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91.
Corrigendum: Reactions with a Metalloid Tin Cluster {Sn10[Si(SiMe3)3]4}2−: Ligand Elimination versus Coordination Chemistry
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92.
Reactions with a Metalloid Tin Cluster {Sn10[Si(SiMe3)3]4}2−: Ligand Elimination versus Coordination Chemistry
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Dr. Claudio Schrenk Birgit Gerke Prof. Dr. Rainer Pöttgen Dr. Andre Clayborne Prof. Dr. Andreas Schnepf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8222-8228
Chemistry that uses metalloid tin clusters as a starting material is of fundamental interest towards understanding the reactivity of such compounds. Since we identified {Sn10[Si(SiMe3)3]4}2? 7 as an ideal candidate for such reactions, we present a further step in the understanding of metalloid tin cluster chemistry. In contrast to germanium chemistry, ligand elimination seems to be a major reaction channel, which leads to the more open metalloid cluster {Sn10[Si(SiMe3)3]3}? 9 , in which the Sn core is only shielded by three Si(SiMe3)3 ligands. Compound 9 is obtained through different routes and is crystallised together with two different countercations. Besides the structural characterisation of this novel metalloid tin cluster, the electronic structure is analysed by 119Sn Mössbauer spectroscopy. Additionally, possible reaction pathways are discussed. The presented first step into the chemistry of metalloid tin clusters thus indicates that, with respect to metalloid germanium clusters, more reaction channels are accessible, thereby leading to a more complex reaction system. 相似文献
93.
Soma Bahmany Lucia E.A. de Wit Dennis A. Hesselink Teun van Gelder Nauras M. Shuker Carla Baan Bart C.H. van der Nagel Birgit C.P. Koch Brenda C.M. de Winter 《Biomedical chromatography : BMC》2019,33(1)
After solid organ transplantation, tacrolimus is given to prevent rejection. Therapeutic drug monitoring is used to reach target concentrations of tacrolimus in whole blood. Because the site of action of tacrolimus is the lymphocyte, and tacrolimus binds ~80% to erythrocytes, the intracellular tacrolimus concentration in lymphocytes is possibly more relevant. For this purpose, we aimed to develop, improve and validate a UPLC–MS/MS method to measure tacrolimus concentrations in isolated peripheral blood mononuclear cells (PBMCs). PBMCs were isolated using a Ficoll separation technique, followed by a washing step using red blood cell lysis. A cell suspension of 50 μL containing 1 million PBMCs was used in combination with MagSiMUS‐TDMPREP. To each sample we added 30 μL lysis buffer, 20 μL reconstitution buffer containing 13C2H4‐tacrolimus as internal standard, 40 μL MagSiMUS‐TDMPREP Type I Particle Mix and 175 μL Organic Precipitation Reagent VI for methanol‐based protein precipitation. A 10 μL aliquot of the supernatant was injected into the UPLC–MS/MS system. The method was validated, resulting in high sensitivity and specificity. The method was linear (r2 = 0.997) over the range 5.0–1250 pg/1 × 106 PBMCs. The inaccuracy was <5% and the imprecision was <15%. The washing steps following Ficoll isolation could be performed at either room temperature or on ice, with no effect of the temperature on the results. A method for the analysis of tacrolimus concentrations in PBMCs was developed and successfully validated. Further research will be performed to investigate the correlation between concentrations in PBMCs and clinical outcome. 相似文献
94.
Roy A. Meoded Dr. Reiko Ueoka Dr. Eric J. N. Helfrich Dr. Katja Jensen Nancy Magnus Prof. Dr. Birgit Piechulla Prof. Dr. Jörn Piel 《Angewandte Chemie (International ed. in English)》2018,57(36):11644-11648
Enzymatic core components from trans‐acyltransferase polyketide synthases (trans‐AT PKSs) catalyze exceptionally diverse biosynthetic transformations to generate structurally complex bioactive compounds. Here we focus on a group of oxygenases identified in various trans‐AT PKS pathways, including those for pederin, oocydins, and toblerols. Using the oocydin pathway homologue (OocK) from Serratia plymuthica 4Rx13 and N‐acetylcysteamine (SNAC) thioesters as test surrogates for acyl carrier protein (ACP)‐tethered intermediates, we show that the enzyme inserts oxygen into β‐ketoacyl moieties to yield malonyl ester SNAC products. Based on these data and the identification of a non‐hydrolyzed oocydin congener with retained ester moiety, we propose a unified biosynthetic pathway of oocydins, haterumalides, and biselides. By providing access to internal ester, carboxylate pseudostarter, and terminal hydroxyl functions, oxygen insertion into polyketide backbones greatly expands the biosynthetic scope of PKSs. 相似文献
95.
Birgit Maaten Lauri Loo Alar Konist Andres Siirde 《Journal of Thermal Analysis and Calorimetry》2018,131(3):2087-2091
Four oil shale samples with different amounts of organic and mineral matter were analysed through non-isothermal thermogravimetric analysis using a heating rate of 50 °C min?1 in nitrogen. The goal of the paper is to study the supposed catalytic effect of the indigenous and removed minerals. The samples contained 30, 49, 70 and 90% of organic matter, respectively. X-ray diffraction analysis was used to identify the minerals in the samples. Thermal analysis experiments were carried out up to temperatures of 850 °C in pyrolysis conditions. The mass loss data were used to study the variations in the conversion profiles of the organic matter depending on the content of the mineral matter. The obtained data and the comparison of the sample composition show that the effect of the mineral matter amount on the course of the pyrolysis processes is insignificant. 相似文献
96.
Axel Wehling Dr. Wiebke H. Pohl Birgit Gerke Stephan Kipp Dr. Peter J. Walla Prof. Dr. 《Chemphyschem》2008,9(2):327-331
Scanning electron microscope images show that it is easy to generate nanopores on polycarbonate membranes with well‐defined pore diameters by ion‐track perforation and subsequent magnetron sputtering with metal. The size reduction of the nanopores during sputtering with gold is a linear function of time. Images of different angles and from the bottom side of the membrane show that the channels are the smallest very close to the surface of the metal layer, have a conelike shape, and reach about half as much into the polymer membranes as the metal‐layer thickness. This topographical pore shape is ideal for use as optically coherent near‐field sources in deep‐nulling microscopy. We present the first results of significantly improved nulling stabilization in the presence (<2 nm optical pathway difference) and the absence (<0.6 nm optical pathway difference) of the nanoapertures in the focal region of a deep‐nulling microscope. 相似文献
97.
A CE-MS method was developed and validated for the quantitative analysis of negatively charged metabolites by making use of the high mass accuracy and the quantitation capabilities of a TOF mass analyzer in combination with automated feature extraction and database search. Metabolites of the central carbon metabolism were quantified with an LOD and lower LOQ (LLOQ) of 0.2-2 and 1-4 microM, respectively. The method was used to elucidate metabolic changes in the Escherichia coli deletion mutant PntAB-UdhA that lacks nicotinamide nucleotide transhydrogenase function, under both stationary and exponential growth conditions. The reproducibility of metabolite extraction and CE-TOF-MS analysis ranged from 3.7 to 22.7 and 7.9 to 22.6%, respectively, while the biological variance was 3.4-31.3%. We observed significant differences in metabolite abundance, particularly in the citrate cycle, between wild-type and mutant E. coli. Overall, more than 600 features were found by automated feature detection, which resulted in approximately 150 high-confidence metabolite identifications. Concomitant analyses with two different GC-MS methods allowed not only crossvalidation of the quantitative results obtained by the various methods, but also led to a more comprehensive coverage of the E. coli metabolome. 相似文献
98.
Gunther Buehrdel Rainer Beckert Birgit Friedrich Helmar Goerls 《Journal of heterocyclic chemistry》2008,45(3):845-851
99.
Philipp Seitz Dr. Manik Bhosale Luisa Rzesny Anselm Uhlmann Dr. Jan S. Wössner Robin Wessling Prof. Dr. Birgit Esser 《Angewandte Chemie (International ed. in English)》2023,62(43):e202306184
With their bent π-systems, cyclic conjugation and inherent cavities, conjugated nanohoops are attractive for organic electronics applications. For ease of processing and morphological stability, an incorporation into polymers is desirable, but to date was hampered with few exceptions by synthetic difficulties. We herein present a unique strategy for the synthesis of conjugated nanohoop polymers using a dibenzo[a,e]pentalene (DBP) as central connector. We demonstrate this versatility by synthesizing three electronically diverse copolymers with dithienyldiketo(pyrrolopyrrol), fluorene and carbazole comonomers, and report the first donor-acceptor nanohoop polymer. Optoelectronic investigations reveal the prevalence of cyclic or linear conjugation, depending on the comonomer unit, and ambipolar electrochemical properties through the antiaromatic character of the DBP units. As the first report on using conjugated nanohoops for charge storage as positive electrode materials, we show a significant improvement in battery performance in a nanohoop-containing polymer compared to an equivalent nanohoop-free reference polymer. We believe this study will pave the way for the synthesis of a diverse range of nanohoop polymers and further stimulate their exploration for charge storage in batteries. 相似文献
100.
We refine our earlier work on the existence and uniqueness of structures on -theoretic spectra to show that the connective versions of real and complex -theory as well as the connective Adams summand at each prime have unique structures as commutative -algebras. For the -completion we show that the McClure-Staffeldt model for is equivalent as an ring spectrum to the connective cover of the periodic Adams summand . We establish a Bousfield equivalence between the connective cover of the Lubin-Tate spectrum and .