全文获取类型
收费全文 | 14001篇 |
免费 | 474篇 |
国内免费 | 50篇 |
专业分类
化学 | 11212篇 |
晶体学 | 73篇 |
力学 | 228篇 |
数学 | 1740篇 |
物理学 | 1272篇 |
出版年
2023年 | 100篇 |
2022年 | 312篇 |
2021年 | 560篇 |
2020年 | 310篇 |
2019年 | 364篇 |
2018年 | 266篇 |
2017年 | 223篇 |
2016年 | 469篇 |
2015年 | 471篇 |
2014年 | 451篇 |
2013年 | 870篇 |
2012年 | 924篇 |
2011年 | 1043篇 |
2010年 | 634篇 |
2009年 | 621篇 |
2008年 | 878篇 |
2007年 | 860篇 |
2006年 | 722篇 |
2005年 | 671篇 |
2004年 | 566篇 |
2003年 | 463篇 |
2002年 | 454篇 |
2001年 | 173篇 |
2000年 | 136篇 |
1999年 | 114篇 |
1998年 | 116篇 |
1997年 | 102篇 |
1996年 | 130篇 |
1995年 | 86篇 |
1994年 | 91篇 |
1993年 | 79篇 |
1992年 | 65篇 |
1991年 | 81篇 |
1990年 | 56篇 |
1989年 | 72篇 |
1988年 | 64篇 |
1987年 | 52篇 |
1986年 | 52篇 |
1985年 | 64篇 |
1984年 | 84篇 |
1983年 | 46篇 |
1982年 | 67篇 |
1981年 | 58篇 |
1980年 | 55篇 |
1979年 | 48篇 |
1978年 | 54篇 |
1977年 | 39篇 |
1976年 | 33篇 |
1975年 | 27篇 |
1963年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Rodríguez Patino JM Molina Ortiz SE Carrera Sánchez C Rodríguez Niño MR Añón MC 《Journal of colloid and interface science》2003,268(1):50-57
In this paper we present surface dilatational properties of soy globulins (beta-conglycinin, glycinin, and reduced glycinin with 10 mM of dithiothreitol (DTT)) adsorbed onto the air-water interface, as a function of adsorption time. The experiments were performed at constant temperature (20 degrees C), pH (8.0), and ionic strength (0.05 M). The surface rheological parameters were measured as a function of protein concentration (ranging from 1 to 1x10(-3)% wt/wt). We found that the surface dilatational modulus, E, increases, and the phase angle, phi, decreases with time, theta, which may be associated with protein adsorption. These phenomena have been related to protein adsorption, unfolding, and/or protein-protein interactions (at long-term adsorption) as a function of protein concentration in solution. From a rheological point of view, the surface viscoelastic characteristics of soy globulin films adsorbed at the air-water interface are practically elastic. The main conclusion is that the dilatational properties of the adsorbed films depend on the molecular structure of the protein. 相似文献
962.
Theodosis Giousis Georgia Potsi Antonios Kouloumpis Konstantinos Spyrou Yiannis Georgantas Nikolaos Chalmpes Konstantinos Dimos Myrsini‐Kiriaki Antoniou Georgios Papavassiliou Athanasios B. Bourlinos Hae Jin Kim Vijay Kumar Shankarayya Wadi Saeed Alhassan Majid Ahmadi Bart J. Kooi Graeme Blake Daniel M. Balazs Maria A. Loi Dimitrios Gournis Petra Rudolf 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2021,133(1):364-369
Germanane (GeH), a germanium analogue of graphane, has recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices, photovoltaics, and photocatalysis. Up to now, the synthesis of GeH has been conducted by substituting Ca by H in a β‐CaGe2 layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6 to 14 days. The new and facile protocol presented here allows to synthesize GeH at room temperature in a significantly shorter time (a few minutes), which renders this method highly attractive for technological applications. The GeH produced with this method is highly pure and has a band gap (Eg) close to 1.4 eV, a lower value than that reported for germanane synthesized using HCl, which is promising for incorporation of GeH in solar cells. 相似文献
963.
Charlotte Toftmann Hansen Hanne E. H. Mller Aleksandra Maria Rojek Niels Marcussen Hans Christian Beck Niels Abildgaard 《Molecules (Basel, Switzerland)》2021,26(12)
Screening for systemic amyloidosis is typically carried out with abdominal fat aspirates with varying reported sensitivities. Fat aspirates are preferred for use in primary screening instead of organ biopsies as they are less invasive and thereby minimize the potential risk of complications. At Odense Amyloidosis Center, we performed a prospective study on whether the combined use of fat aspirate and tru-cut skin biopsy could increase the diagnostic sensitivity. Both fat aspirates and skin biopsies were screened with Congo Red staining, and positive biopsies were subsequently subtyped using immunoelectron microscopy and mass spectrometry. Seventy-six patients were included. In total, 24 patients had systemic amyloidosis (11 AL, 12 wtATTR, 1 AA), and 6 patients had localized amyloidosis. Combined fat aspirate and skin biopsy were Congo Red-positive in 15 patients (overall sensitivity (OS) 62.5%). Fat aspirates were positive in 14 patients (OS 58.3%), and the skin biopsy was positive in 5 patients (OS 20.8%). In only one patient did the skin biopsy add extra diagnostic information. The sensitivity differed between AL and ATTR amyloidosis—81.8% and 41.7%, respectively. Using skin biopsy as the only screening method is not recommended. 相似文献
964.
Valentina Laghezza Masci Anna‐Rita Taddei Thomas Courant Ozgül Tezgel Fabrice Navarro Franco Giorgi Denis Mariolle Anna‐Maria Fausto Isabelle Texier 《Macromolecular bioscience》2019,19(5)
Curcumin‐loaded collagen cryostructurates have been devised for wound healing applications. Curcumin displays strong antioxidant, antiseptic, and anti‐inflammatory properties, while collagen is acknowledged for promoting cell adhesion, migration and differentiation. However, when curcumin is loaded directly into collagen hydrogels, it forms large molecular aggregates and clogs the matrix pores. A double‐encapsulation strategy is therefore developed by loading curcumin into lipid nanoparticles (LNP), and embedding these particles inside collagen scaffolds. The resulting collagen/LNP cryostructurates have an optimal fibrous structure with ≈100 µm average pore size for sustaining cell migration. Results show that collagen is structurally unaltered and that nanoparticles are homogeneously distributed amidst collagen fibers. Hydrogels soaked in saline buffer release about 20 to 30% of their nanoparticles content within 24 h, while achieved 100% release after 25 days. When exposed to NIH 3T3 fibroblasts, these hydrogels provide a satisfactory scaffold for cell interaction as early as 4 h after seeding, with no cytotoxic counter effect. These positive features make the collagen/lipid cryostructurates a promising material for further use in wound healing. 相似文献
965.
Isabel V. L. Wilkinson Kelly J. Perkins Hannah Dugdale Lee Moir Aini Vuorinen Maria Chatzopoulou Sarah E. Squire Sebastian Monecke Alexander Lomow Marcus Geese Philip D. Charles Peter Burch Jonathan M. Tinsley Graham M. Wynne Stephen G. Davies Francis X. Wilson Fraydoon Rastinejad Shabaz Mohammed Kay E. Davies Angela J. Russell 《Angewandte Chemie (International ed. in English)》2020,59(6):2420-2428
Duchenne muscular dystrophy (DMD) is a fatal muscle‐wasting disease arising from mutations in the dystrophin gene. Upregulation of utrophin to compensate for the missing dystrophin offers a potential therapy independent of patient genotype. The first‐in‐class utrophin modulator ezutromid/SMT C1100 was developed from a phenotypic screen through to a Phase 2 clinical trial. Promising efficacy and evidence of target engagement was observed in DMD patients after 24 weeks of treatment, however trial endpoints were not met after 48 weeks. The objective of this study was to understand the mechanism of action of ezutromid which could explain the lack of sustained efficacy and help development of new generations of utrophin modulators. Using chemical proteomics and phenotypic profiling we show that the aryl hydrocarbon receptor (AhR) is a target of ezutromid. Several lines of evidence demonstrate that ezutromid binds AhR with an apparent KD of 50 nm and behaves as an AhR antagonist. Furthermore, other reported AhR antagonists also upregulate utrophin, showing that this pathway, which is currently being explored in other clinical applications including oncology and rheumatoid arthritis, could also be exploited in future DMD therapies. 相似文献
966.
Dongyi Liu Ahmed M. El‐Zohry Maria Taddei Clemens Matt Laura Bussotti Zhijia Wang Jianzhang Zhao Omar F. Mohammed Mariangela Di Donato Stefan Weber 《Angewandte Chemie (International ed. in English)》2020,59(28):11591-11599
We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long‐lived triplet charge‐transfer (3CT) state, based on the electron spin control using spin‐orbit charge transfer intersystem crossing (SOCT‐ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT‐ISC takes 8 ns to produce the 3NI* state. Then the slow secondary CS (125 ns) gives the long‐lived 3CT state (0.94 μs in deaerated n‐hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as 1NI*→1CT→3NI*→3CT. With time‐resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron‐spin polarization pattern was observed for the naphthalimide‐localized triplet state. Our spiro compact dyad structure and the electron spin‐control approach is different to previous methods for which invoking transition‐metal coordination or chromophores with intrinsic ISC ability is mandatory. 相似文献
967.
Multi‐responses Methodology Applied in the Electroanalytical Determination of Hair Dye by Using Printed Carbon Electrode Modified with Graphene 下载免费PDF全文
Felipe Fantinato Hudari Sergio Luis Costa Ferreira Maria Valnice Boldrin Zanoni 《Electroanalysis》2016,28(5):1085-1092
This paper describes a rapid and sensitive method for determination of the hair dye Basic Blue 41 in wastewater samples using screen‐printed carbon electrodes modified with graphene (SPCE/Gr). The method is based on the reversible reduction of azo groups of the dye at potential of ?0.23 V/?0.26 V, where both the anodic and cathodic currents increased 1,300 % when compared to screen‐printed carbon (SPCE) and glassy carbon electrodes (GCE). The optimization of a square wave voltammetric method was performed by means of 23 factorial design, Doehlert matrix and multi‐response assays, and the best parameters were: frequency (54.8 Hz), step potential (6 mV), pulse amplitude (43.7 mV) and pH 4.5. The analytical curve was constructed from 3.00×10?8 to 2.01×10?6 mol L?1, with detection and quantification limits of 5.00×10?9 and 1.70×10?8 mol L?1, respectively. The repeatability of the method evaluated for 10 consecutive measurements at concentrations of 1.70×10?7 mol L?1 and 1.70×10?6 mol L?1, showed relative standard deviation of 3.56 and 0.57 %, respectively. The sensor based in SPCE/Gr was successfully applied in wastewater samples collected from a drinking water treatment plant and validated by comparison with HPLC‐DAD method with good accuracy. 相似文献
968.
Michael G. Pfeffer Tanja Kowacs Dr. Maria Wächtler Dr. Julien Guthmuller Prof. Dr. Benjamin Dietzek Prof. Dr. Johannes G. Vos Prof. Dr. Sven Rau 《Angewandte Chemie (International ed. in English)》2015,54(22):6627-6631
A molecular photocatalyst consisting of a RuII photocenter, a tetrapyridophenazine bridging ligand, and a PtX2 (X=Cl or I) moiety as the catalytic center functions as a stable system for light‐driven hydrogen production. The catalytic activity of this photochemical molecular device (PMD) is significantly enhanced by exchanging the terminal chlorides at the Pt center for iodide ligands. Ultrafast transient absorption spectroscopy shows that the intramolecular photophysics are not affected by this change. Additionally, the general catalytic behavior, that is, instant hydrogen formation, a constant turnover frequency, and stability are maintained. Unlike as observed for the Pd analogue, the presence of excess halide does not affect the hydrogen generation capacity of the PMD. The highly improved catalytic efficiency is explained by an increased electron density at the Pt catalytic center, this is confirmed by DFT studies. 相似文献
969.
Dr. Andreas A. Bastian Dr. Maria Bastian Dr. Manuel Jäger Mark Loznik Dr. Eliza M. Warszawik Xintong Yang Dr. Nabil Tahiri Dr. Peter Fodran Prof. Dr. Martin D. Witte Anne Thoma Dr. Jens Köhler Prof. Dr. Adriaan J. Minnaard Prof. Dr. Andreas Herrmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(36):e202200883
The continuous emergence of antimicrobial resistance is causing a threat to patients infected by multidrug-resistant pathogens. In particular, the clinical use of aminoglycoside antibiotics, broad-spectrum antibacterials of last resort, is limited due to rising bacterial resistance. One of the major resistance mechanisms in Gram-positive and Gram-negative bacteria is phosphorylation of these amino sugars at the 3’-position by O-phosphotransferases [APH(3’)s]. Structural alteration of these antibiotics at the 3’-position would be an obvious strategy to tackle this resistance mechanism. However, the access to such derivatives requires cumbersome multi-step synthesis, which is not appealing for pharma industry in this low-return-on-investment market. To overcome this obstacle and combat bacterial resistance mediated by APH(3’)s, we introduce a novel regioselective modification of aminoglycosides in the 3’-position via palladium-catalyzed oxidation. To underline the effectiveness of our method for structural modification of aminoglycosides, we have developed two novel antibiotic candidates overcoming APH(3’)s-mediated resistance employing only four synthetic steps. 相似文献
970.
Dr. Martin Piesch Dr. Amélie Nicolay Dr. Maria Haimerl Dr. Michael Seidl Dr. Gábor Balázs Prof. T. Don Tilley Prof. Dr. Manfred Scheer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(45):e202201144
The bridging MeCN ligand in the dicopper(I) complexes [(DPFN)Cu2(μ,η1 : η1-MeCN)][X]2 (X=weakly coordinating anion, NTf2 ( 1 a ), FAl[OC6F10(C6F5)]3 ( 1 b ), Al[OC(CF3)3]4 ( 1 c )) was replaced by white phosphorus (P4) or yellow arsenic (As4) to yield [(DPFN)Cu2(μ,η2 : η2-E4)][X]2 (E=P ( 2 a – c ), As ( 3 a – c )). The molecular structures in the solid state reveal novel coordination modes for E4 tetrahedra bonded to coinage metal ions. Experimental data and quantum chemical computations provide information concerning perturbations to the bonding in coordinated E4 tetrahedra. Reactions with N-heterocyclic carbenes (NHCs) led to replacement of the E4 tetrahedra with release of P4 or As4 and formation of [(DPFN)Cu2(μ,η1 : η1-MeNHC)][X]2 ( 4 a,b ) or to an opening of one E−E bond leading to an unusual E4 butterfly structural motif in [(DPFN)Cu2(μ,η1 : η1-E4DippNHC)][X]2 (E=P ( 5 a,b ), E=As ( 6 )). With a cyclic alkyl amino carbene (EtCAAC), cleavage of two As−As bonds was observed to give two isomers of [(DPFN)Cu2(μ,η2 : η2-As4EtCAAC)][X]2 ( 7 a,b ) with an unusual As4-triangle+1 unit. 相似文献