全文获取类型
收费全文 | 3266篇 |
免费 | 235篇 |
国内免费 | 1篇 |
专业分类
化学 | 2319篇 |
晶体学 | 18篇 |
力学 | 136篇 |
数学 | 548篇 |
物理学 | 481篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 23篇 |
2020年 | 37篇 |
2019年 | 43篇 |
2018年 | 62篇 |
2017年 | 38篇 |
2016年 | 132篇 |
2015年 | 97篇 |
2014年 | 107篇 |
2013年 | 230篇 |
2012年 | 249篇 |
2011年 | 268篇 |
2010年 | 140篇 |
2009年 | 155篇 |
2008年 | 214篇 |
2007年 | 221篇 |
2006年 | 211篇 |
2005年 | 216篇 |
2004年 | 180篇 |
2003年 | 161篇 |
2002年 | 118篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 35篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 24篇 |
1995年 | 20篇 |
1994年 | 9篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 14篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 8篇 |
1982年 | 25篇 |
1981年 | 13篇 |
1980年 | 26篇 |
1979年 | 28篇 |
1978年 | 18篇 |
1977年 | 20篇 |
1976年 | 26篇 |
1975年 | 19篇 |
1974年 | 18篇 |
1973年 | 16篇 |
排序方式: 共有3502条查询结果,搜索用时 31 毫秒
141.
Spin‐State Ordering on One Sub‐lattice of a Mononuclear Iron(III) Spin Crossover Complex Exhibiting LIESST and TIESST 下载免费PDF全文
Dr. Kevin D. Murnaghan Dr. Chiara Carbonera Dr. Loic Toupet Dr. Michael Griffin Dr. Marinela M. Dîrtu Dr. Cédric Desplanches Prof. Dr. Yann Garcia Prof. Eric Collet Prof. Jean‐François Létard Dr. Grace G. Morgan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(19):5613-5618
The two‐step spin crossover in mononuclear iron(III) complex [Fe(salpm)2]ClO4 ? 0.5 EtOH ( 1 ) is shown to be accompanied by a structural phase transition as concluded from 57Fe Mössbauer spectroscopy and single crystal X‐ray diffraction, with spin‐state ordering on just one of two sub‐lattices in the intermediate magnetic and structural phase. The complex also exhibits thermal‐ and light‐induced spin‐state trapping (TIESST and LIESST), and relaxation from the LIESST and TIESST excited states occurs via the broken symmetry intermediate phase. Two relaxation events are evident in both experiments, that is, two T(LIESST) and two T(TIESST) values are recorded. The change in symmetry which accompanies the TIESST effect was followed in real time using single crystal diffraction. After flash freezing at 15 K the crystal was warmed to 40 K at which temperature superstructure reflections were observed to appear and disappear within a 10 000 s time range. In the frame of the international year of crystallography, these results illustrate how X‐ray diffraction makes it possible to understand complex ordering phenomena. 相似文献
142.
An Investigation of Photo‐ and Pressure‐Induced Effects in a Pair of Isostructural Two‐Dimensional Spin‐Crossover Framework Materials 下载免费PDF全文
Dr. Natasha F. Sciortino Dr. Suzanne M. Neville Dr. Cédric Desplanches Dr. Jean‐François Létard Dr. Victor Martinez Prof. José Antonio Real Dr. Boujemaa Moubaraki Prof. Keith S. Murray Prof. Cameron J. Kepert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7448-7457
Two new isostructural iron(II) spin‐crossover (SCO) framework (SCOF) materials of the type [Fe(dpms)2(NCX)2] (dpms=4,4′‐dipyridylmethyl sulfide; X=S ( SCOF‐6(S) ), X=Se ( SCOF‐6(Se) )) have been synthesized. The 2D framework materials consist of undulating and interpenetrated rhomboid (4,4) nets. SCOF‐6(S) displays an incomplete SCO transition with only approximately 30 % conversion of high‐spin (HS) to low‐spin iron(II) sites over the temperature range 300–4 K (T1/2=75 K). In contrast, the NCSe? analogue, SCOF‐6(Se) , displays a complete SCO transition (T1/2=135 K). Photomagnetic characterizations reveal quantitative light‐ induced excited spin‐state trapping (LIESST) of metastable HS iron(II) sites at 10 K. The temperature at which the photoinduced stored information is erased is 58 and 50 K for SCOF‐6(S) and SCOF‐6(Se) , respectively. Variable‐pressure magnetic measurements were performed on SCOF‐6(S) , revealing that with increasing pressure both the T1/2 value and the extent of spin conversion are increased; with pressures exceeding 5.2 kbar a complete thermal transition is achieved. This study confirms that kinetic trapping effects are responsible for hindering a complete thermally induced spin transition in SCOF‐6(S) at ambient pressure due to an interplay between close T1/2 and T(LIESST) values. 相似文献
143.
Precision PEGylated Polymers Obtained by Sequence‐Controlled Copolymerization and Postpolymerization Modification 下载免费PDF全文
Sansanee Srichan Dr. Hatice Mutlu Dr. Nezha Badi Dr. Jean‐François Lutz 《Angewandte Chemie (International ed. in English)》2014,53(35):9231-9235
Copolymers containing water‐soluble poly(ethylene glycol) (PEG) side chains and precisely controlled functional microstructures were synthesized by sequence‐controlled copolymerization of donor and acceptor comonomers, that is, styrene derivatives and N‐substituted maleimides. Two routes were compared for the preparation of these structures: a) the direct use of a PEG–styrene macromonomer as a donor comonomer, and b) the use of an alkyne‐functionalized styrenic comonomer, which was PEGylated by copper‐catalyzed alkyne–azide cycloaddition after polymerization. The latter method was found to be the most versatile and enabled the synthesis of high‐precision copolymers. For example, PEGylated copolymers containing precisely positioned fluorescent (e.g. pyrene), switchable (e.g. azobenzene), and reactive functionalities (e.g. an activated ester) were prepared. 相似文献
144.
Dr. Tao Liu Dr. Aline Nonat Dr. Maryline Beyler Dr. Martín Regueiro‐Figueroa Dr. Katia Nchimi Nono Dr. Olivier Jeannin Dr. Franck Camerel Dr. François Debaene Dr. Sarah Cianférani‐Sanglier Prof. Raphaël Tripier Dr. Carlos Platas‐Iglesias Dr. Loïc J. Charbonnière 《Angewandte Chemie (International ed. in English)》2014,53(28):7259-7263
Lanthanide complexes (Ln=Eu, Tb, and Yb) that are based on a C2‐symmetric cyclen scaffold were prepared and characterized. The addition of fluoride anions to aqueous solutions of the complexes resulted in the formation of dinuclear supramolecular compounds in which the anion is confined into the cavity that is formed by the two complexes. The supramolecular assembly process was monitored by UV/Vis absorption, luminescence, and NMR spectroscopy and high‐resolution mass spectrometry. The X‐ray crystal structure of the europium dimer revealed that the architecture of the scaffold is stabilized by synergistic effects of the Eu? F? Eu bridging motive, π stacking interactions, and a four‐component hydrogen‐bonding network, which control the assembly of the two [EuL] entities around the fluoride ion. The strong association in water allowed for the luminescence sensing of fluoride down to a detection limit of 24 nM . 相似文献
145.
Léna Sambe Victor R. de La Rosa Khaled Belal Dr. François Stoffelbach Dr. Joel Lyskawa Dr. François Delattre Marc Bria Prof. Graeme Cooke Prof. Richard Hoogenboom Prof. Patrice Woisel 《Angewandte Chemie (International ed. in English)》2014,53(20):5044-5048
A new class of polymeric thermometers with a memory function is reported that is based on the supramolecular host–guest interactions of poly(N‐isopropylacrylamide) (PNIPAM) with side‐chain naphthalene guest moieties and the tetracationic macrocycle cyclobis(paraquat‐p‐phenylene) (CBPQT4+) as the host. This supramolecular thermometer exhibits a memory function for the thermal history of the solution, which arises from the large hysteresis of the thermoresponsive LCST phase transition (LCST=lower critical solution temperature). This hysteresis is based on the formation of a metastable soluble state that consists of the PNIPAM–CBPQT4+ host–guest complex. When heated above the transition temperature, the polymer collapses, and the host–guest interactions are disrupted, making the polymer more hydrophobic and less soluble in water. Aside from providing fundamental insights into the kinetic control of supramolecular assemblies, the developed thermometer with a memory function might find use in applications spanning the physical and biological sciences. 相似文献
146.
Xibo Yan Dr. Marco Delgado Dr. Amy Fu Pierre Alcouffe Dr. Sébastien G. Gouin Prof. Etienne Fleury Prof. Joseph L. Katz Dr. François Ganachaud Dr. Julien Bernard 《Angewandte Chemie (International ed. in English)》2014,53(27):6910-6913
A general, rapid, and undemanding method to generate at will functional oil‐filled nanocapsules through nanoprecipitation is reported. On the basis of polymer and hexadecane/water/acetone phase diagrams, the composition can be set so that polymer chains preferentially stick at the interface of the oil droplets to create nanocapsules. The nanocapsules can be decorated with biorelevant molecules (biotin, fluorescent tags, metal nanoparticles) within the shell and loaded with hydrophobic molecules in a simple one‐pot procedure. 相似文献
147.
Kinetic Modeling of α‐Hydrogen Abstractions from Unsaturated and Saturated Oxygenate Compounds by Carbon‐Centered Radicals 下载免费PDF全文
Paschalis D. Paraskevas Dr. Maarten K. Sabbe Prof. Marie‐Françoise Reyniers Prof. Dr. Nikos Papayannakos Prof. Dr. Guy B. Marin 《Chemphyschem》2014,15(9):1849-1866
Hydrogen abstractions are important elementary reactions in a variety of reacting media at high temperatures in which oxygenates and hydrocarbon radicals are present. Accurate kinetic data are obtained from CBS‐QB3 ab initio (AI) calculations by using conventional transition‐state theory within the high‐pressure limit, including corrections for hindered rotation and tunneling. From the obtained results, a group‐additive (GA) model is developed that allows the Arrhenius parameters and rate coefficients for abstraction of the α‐hydrogen from a wide range of oxygenate compounds to be predicted at temperatures ranging from 300 to 1500 K. From a training set of 60 hydrogen abstractions from oxygenates by carbon‐centered radicals, 15 GA values (ΔGAVos) are obtained for both the forward and reverse reactions. Among them, four ΔGAVos refer to primary contributions, and the remaining 11 ΔGAVos refer to secondary ones. The accuracy of the model is further improved by introducing seven corrections for cross‐resonance stabilization of the transition state from an additional set of 43 reactions. The determined ΔGAVos are validated upon a test set of AI data for 17 reactions. The mean absolute deviation of the pre‐exponential factors (log A) and activation energies (Ea) for the forward reaction at 300 K are 0.238 log(m3 mol?1 s?1) and 1.5 kJ mol?1, respectively, whereas the mean factor of deviation <ρ> between the GA‐predicted and the AI‐calculated rate coefficients is 1.6. In comparison with a compilation of 33 experimental rate coefficients, the <ρ> between the GA‐predicted values and these experimental values is only 2.2. Hence, the constructed GA model can be reliably used in the prediction of the kinetics of α‐hydrogen‐abstraction reactions between a broad range of oxygenates and oxygenate radicals. 相似文献
148.
Back Cover: Assessment of DNA Binding to Human Rad51 Protein by using Quartz Crystal Microbalance and Atomic Force Microscopy: Effects of ADP and BRC4‐28 Peptide Inhibitor (ChemPhysChem 17/2014) 下载免费PDF全文
149.
Santiago Pedro H. O. Fujimori Mahmi Chagas Marcio A. S. França Eduardo L. Honorio-França Adenilda C. Gatto Claudia C. 《Structural chemistry》2020,31(1):171-180
Structural Chemistry - Two novel Cu(I) complexes with the 2-acetylpyridine-N(4)-phenyl semicarbazone (HL) ligand, [CuCl (HL)(PPh3)]∙CH3CN (1) and [CuBr (HL)(PPh3)] (2), were investigated by... 相似文献
150.
Marcelo T. Oliveira Ana Flávia L. Specian Célia G.T.J. Andrade Emanuele J.G. Fran?a Luciana Furlaneto-Maia Marcia C. Furlaneto 《Micron (Oxford, England : 1993)》2010,41(6):604-608
Candida parapsilosis is found frequently as commensal organism on epithelial tissues, and is also an increasing cause of nosocomial infection. Scanning electron microscope (SEM) observations were used to analyse the capability of C. parapsilosis cells to adhere and grow as biofilm on human natural substrates and to compare the adherence pattern of isolates exhibiting distinct phenotypes. Cells from the crepe phenotype are predominantly elongated and form pseudohyphae whereas cells from the smooth phenotype are yeast-shaped, either in liquid cultures or on human nail and hair surfaces. The electron micrographs revealed that C. parapsilosis cells from the smooth phenotype adhered in higher number to both surfaces compared to the observed for the crepe phenotype. SEM analysis of human hair surface revealed that cells from the smooth phenotype appear as clumped blastoconidia of uniform morphology embedded in a flocculent extracellular material forming biofilm. The extracellular material and biofilm were seeing in a less extension in the crepe phenotype. A distinct adherence pattern was observed when human nail was used as substrate. Here C. parapsilosis cells seem to be linked to surface structures of human nail plate. Fibrillar extracellular material was observed connecting neighbouring cells as well as nail surface. 相似文献