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991.
992.
Gräwert T Span I Bacher A Groll M 《Angewandte Chemie (International ed. in English)》2010,49(47):8802-8809
The biosynthesis of natural products is a treasure trove of unusual reaction mechanisms. This Minireview summarizes recent work on the structure and mechanism of IspH protein, which catalyzes the reductive dehydroxylation of an allyl alcohol in a biosynthetic pathway leading to isoprenoid precursors. 相似文献
993.
Oya Tagit Dominik Jańczewski Ming Yong Han Jennifer L. Herek 《European Polymer Journal》2010,46(7):1397-16948
Synthesis, characterization, and applications of novel thermoresponsive polymeric coatings for quantum dots (QDs) are presented. Comb-copolymers featuring hydrophobic alkyl groups, carboxylic groups and poly(N-isopropylacrylamide) (PNIPAM) side chains with molar masses ranging from 1000 g/mol to 25,400 g/mol were obtained. The amphiphilic comb-copolymers were shown to efficiently transfer the QDs to aqueous media. The PNIPAM-coated QD materials display a lower critical solution temperature (LCST). The absorbance, luminescence emission, size of the assemblies, and electrophoretic mobility were followed as a function of temperature and the reversibility of the temperature induced changes is demonstrated by cyclic heating and cooling. 相似文献
994.
Ligia Frunza Stefan Frunza Irina Zgura Traian Beica Nicoleta Gheorghe Paul Ganea Daniel Stoenescu Adrian Dinescu Andreas Schönhals 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(4):1228-1235
Composites prepared from aerosil A380 and liquid crystals (LCs) of 4-n-alkyl-4′-cyanophenyl benzoate type, with four to six carbon atoms in the alkyl chain were investigated by infrared spectroscopy. Their high silica content (of 2–7 g aerosil/1 g of LC) was given by thermogravimetric investigations and allows the observation of a rather thin LC layer on the silica particles. Several surface species onto the external surface of the grains were demonstrated. Arguments are given that monomer and dimer species are present in the bulk cyanophenyl benzoate materials while bulk-like species along with hydrogen-bonded ones coexist in the so-called surface layer of the composites. The main interaction of LC molecules with the aerosil surface is by hydrogen bonding taking place with the involvement of the cyan group. There is a contribution of ester carbonyl group to these surface interactions but this cannot be well quantified. 相似文献
995.
Maxwell D. Cummings Jimmy Lindberg Tse‐I Lin Herman de Kock Oliver Lenz Elisabet Lilja Sara Felländer Vera Baraznenok Susanne Nyström Magnus Nilsson Lotta Vrang Michael Edlund Åsa Rosenquist Bertil Samuelsson Pierre Raboisson Kenneth Simmen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(19):3320-3320
996.
A blue light-inducible phosphodiesterase (PDE) activity, specific for the hydrolysis of cyclic di-GMP (c-di-GMP), has been identified in a recombinant protein from Synechococcus elongatus. Blue light (BL) activation is accomplished by a light, oxygen, voltage (LOV) domain, found in plant phototropins and bacterial BL photoreceptors. The genome of S. elongatus contains two genes coding for proteins with LOV domains fused to EAL domains (SL1 and SL2). In both cases, a GGDEF motif is placed in between the LOV and the EAL motifs. Such arrangement is frequently found with diguanylate-cyclase (DGC) functions that form c-di-GMP. Cyclic di-GMP acts as a second messenger molecule regulating biofilm formation in many microbial species. Both enzyme activities modulate the intracellular level of this second messenger, although in most proteins only one of the two enzyme functions is active. Both S. elongatus LOV-GGDEF-EAL proteins were expressed in full length or as truncated proteins. Only the SL2 protein, expressed as a LOV-GGDEF-EAL construct, showed an increase of PDE activity upon BL irradiation, demonstrating this activity for the first time in a LOV-domain protein. Addition of GTP or c-di-GMP did not affect the observed enzymatic activity. In none of the full-length or truncated proteins was a DGC activity detected. 相似文献
997.
Mario Thevis Ines Möller Andreas Thomas Simon Beuck Grigory Rodchenkov Wolfgang Bornatsch Hans Geyer Wilhelm Schänzer 《Analytical and bioanalytical chemistry》2010,396(7):2479-2491
Since January 2009, the list of prohibited substances and methods of doping as established by the World Anti-Doping Agency includes new therapeutics such as the peroxisome-proliferator-activated receptor (PPAR)-delta agonist GW1516, which is categorized as a gene doping substance. GW1516 has completed phase II and IV clinical trials regarding dyslipidemia and the regulation of the lipoprotein transport in metabolic syndrome conditions; however, its potential to also improve athletic performance due to the upregulation of genes associated with oxidative metabolism and a modified substrate preference that shifted from carbohydrate to lipid consumption has led to a ban of this compound in elite sport. In a recent report, two presumably mono-oxygenated and bisoxygenated urinary metabolites of GW1516 were presented, which could serve as target analytes for doping control purposes after full characterization. Hence, in the present study, phase I metabolism was simulated by in vitro assays employing human liver microsomal fractions yielding the same oxygenation products, followed by chemical synthesis of the assumed structures of the two abundant metabolic reaction products. These allowed the identification and characterization of mono-oxygenated and bisoxygenated metabolites (sulfoxide and sulfone, respectively) as supported by high-resolution/high-accuracy mass spectrometry with higher-energy collision-induced dissociation, tandem mass spectrometry, and nuclear magnetic resonance spectroscopy. Since urine samples have been the preferred matrix for doping control purposes, a method to detect the new target GW1516 in sports drug testing samples was developed in accordance to conventional screening procedures based on enzymatic hydrolysis and liquid–liquid extraction followed by liquid chromatography, electrospray ionization, and tandem mass spectrometry. Validation was performed for specificity, limit of detection (0.1 ng/ml), recovery (72%), intraday and interday precisions (7.7–15.1%), and ion suppression/enhancement effects (<10%). 相似文献
998.
Reinhard Miller James K. Ferri Aliyar Javadi Jürgen Krägel Nenad Mucic Rainer Wüstneck 《Colloid and polymer science》2010,288(9):937-950
The response of interfacial layers to deformations in size and shape depends on their composition. The corresponding main
mechanical quantities are elasticity and viscosity of dilation and shear, respectively. Hence, the interfacial rheology represents
a kind of two-dimensional equivalent to the traditional bulk rheology. Due to growing interest in the quantitative understanding
of foams and emulsions, more works are dedicated to studies on interfacial rheology. This overview presents the theoretical
basis for traditional and recently developed experimental tools and discusses their application to different interfacial systems.
While dilational rheology provides information on the composition of mixed interfacial layers, the shear rheology gives answers
essentially on structures formed at an interface. The most frequently used methods at present are the oscillating drop and
bubble tensiometry methods for dilational deformations and oscillating ring/bicone rheometers for shear deformations. 相似文献
999.
Ivana Kiov Zdenk To
ík Milo Budínský Ondej imk Radek Liboska Dominik Rejman Ondej Pa
es Ivan Rosenberg 《Tetrahedron letters》2009,50(49):6745-6747
A straightforward procedure leading to the new phosphonylating reagent, methyl 4-toluenesulfonyloxymethylphosphonate, requiring no chromatographic purification is described. This stable reagent works with the same efficiency as dimethyl and other dialkyl esters for the introduction of an O-phosphonomethyl moiety while, in contrast to dimethyl ester, it does not cause any unwanted methylation of sensitive functionalities. Its utility for the alkylation of protected nucleosides in high yield is exemplified. 相似文献
1000.
A density functional theory based on Wertheim's first order perturbation theory is developed for inhomogeneous complex fluids. The theory is derived along similar lines as interfacial statistical associating fluid theory [S. Tripathi and W. G. Chapman, J. Chem. Phys. 122, 094506 (2005)]. However, the derivation is more general and applies broadly to a range of systems, retaining the simplicity of a segment density based theory. Furthermore, the theory gives the exact density profile for ideal chains in an external field. The general avail of the theory has been demonstrated by applying the theory to lipids near surfaces, lipid bilayers, and copolymer thin films. The theoretical results show excellent agreement with the results from molecular simulations. 相似文献