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981.
Various oxomolybdenum complexes are efficient and selective homogeneous catalysts in the presence of organic hydroperoxides. The increasing interest in the heterogenisation of such catalysts has led to an increased interest in finding suitable support materials for the complexes. These supports include ionic liquids, mesoporous materials and zeolites to name a few. Several methods are used to anchor the catalyst depending on the nature of the carrier material. The supported catalysts combine properties of homogeneous catalysts such as reactivity, control and selectivity with those of heterogeneous catalysts such as enhanced stability and recyclability. 相似文献
982.
983.
We describe a method for modeling chemical mutagenicity in terms of simple rules based on molecular features. A classification model was built using a rule-based ensemble method called RuleFit, developed by Friedman and Popescu. We show how performance compares favorably against literature methods. Performance was measured through the use of cross-validation and testing on external test sets. All data sets used are publicly available. The method automatically generated transparent rules in terms of molecular structure that agree well with known toxicology. While we have focused on chemical mutagenicity in demonstrating this method, we anticipate that it may be more generally useful in modeling other molecular properties such as other types of chemical toxicity. 相似文献
984.
For C*-algebras A and B, the identity map from into A
λ
B is shown to be injective. Next, we deduce that the center of the completion of the tensor product A⊗B of two C*-algebras A and B with centers Z(A) and Z(B) under operator space projective norm is equal to . A characterization of isometric automorphisms of and A
h
B is also obtained.
Dedicated to Ajit Iqbal Singh on her 65th birthday. 相似文献
985.
Veerasamy Ravichandran Abhishek Jain Vishnukanth Mourya Ram K. Agrawal 《Chemical Papers》2008,62(6):596-602
A QSAR study on a series of pyrimidinyl and triazinyl amines was performed to explore the physico-chemical parameters responsible
for their anti-HIV activity and cytotoxicity. Physico-chemical parameters were calculated using WIN CAChe 6.1. Stepwise multiple
linear regression analysis was carried out to derive QSAR models which were further evaluated for statistical significance
and predictive power by internal and external validation. The selected best QSAR models showed correlation coefficient R of 0.914 and 0.901, and cross-validated squared correlation coefficient Q
2 of 0.685 and 0.691 for anti-HIV activity and cytotoxicity, respectively. The developed significant QSAR model indicates that
hydrophobicity of the whole molecule plays an important role in the anti-HIV activity and cytotoxicity of pyrimidinyl and
triazinyl amine derivatives. When hydrophobicity is increased, anti-HIV activity of the present series of compounds is decreased
leading to high cytotoxicity. 相似文献
986.
Chemical shift assignments of (1)H and (13)C of five cembrene compounds isolated from the hexane extract of guggul, the resin of Commiphora mukul, are reported. Using (1)H, (13)C, and 2D NMR methods their structures were determined as cembrene (1-isopropyl-4,8,12-trimethyl-cyclotetradeca-2,4,7,11-tetraene), cembrene A (1-isopropenyl-4,8,12-trimethyl-cyclotetradeca-4,8,12-triene), cembrenol (1-isopropyl-4,8,12-trimethyl-cyclotetradeca-3,7,11-trienol), mukulol (1-isopropyl-4,8,12-trimethyl- cyclotetradeca-3,7,11-trienol), and verticillol (4,8,12,15,15-pentamethyl-bicyclo[9.3.1]pentadeca-3,7-dien-12-ol). 相似文献
987.
Empirical scoring functions used in protein-ligand docking calculations are typically trained on a dataset of complexes with
known affinities with the aim of generalizing across different docking applications. We report a novel method of scoring-function
optimization that supports the use of additional information to constrain scoring function parameters, which can be used to
focus a scoring function’s training towards a particular application, such as screening enrichment. The approach combines
multiple instance learning, positive data in the form of ligands of protein binding sites of known and unknown affinity and
binding geometry, and negative (decoy) data of ligands thought not to bind particular protein binding sites or known not to bind in particular geometries. Performance of the method for the Surflex-Dock scoring function is shown in cross-validation
studies and in eight blind test cases. Tuned functions optimized with a sufficient amount of data exhibited either improved
or undiminished screening performance relative to the original function across all eight complexes. Analysis of the changes
to the scoring function suggest that modifications can be learned that are related to protein-specific features such as active-site
mobility. 相似文献
988.
Vinod K. Jain Hiren C. Mandalia Eringathodi Suresh 《Journal of inclusion phenomena and macrocyclic chemistry》2008,62(1-2):167-178
The synthesis, spectroscopic characterization and preliminary complexation properties of functionalized calix[4]pyrroles are described. To date, two generalized preparative approaches have been pursued (i) modifying the basic pyrrole-plus-ketone synthesis of calix[4]pyrrole by using microwave irradiation protocol, (ii) the basic meso-tetra(methyl) meso-tetra(p-nitrophenyl) calix[4]pyrrole skeleton was functionalized to give hydroxamic acids, especially in the meso-position of the macrocycles. The structures of novel calix[4]pyrrole hydroxamic acid derivatives were confirmed on the basis of various physico-chemical techniques such as elemental analysis, FT-IR, 1H NMR and FAB-Mass. The results of preliminary studies on the extraction of vanadium (V) with the host calix[4]pyrrole hydroxamic acids were elucidated by significant examination of UV–Vis spectroscopy and ICP-AES. Single crystal structure of basic meso-tetra(methyl) meso-tetra (p-nitro phenyl) calix[4]pyrrole moiety has also been reported. 相似文献
989.
The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of chromium dipeptide complex ([Cr(Ⅲ)-Gly-Gly]2 ) with ninhydrin under varying conditions has been investigated. The rates of the reaction were determined in both water and surfactant micelles in the absence and presence of various organic and inorganic salts at 70 ℃ and pH 5.0. The reaction followed first- and fractional-order kinetics with respect to [Cr(Ⅲ)- Gly-Gly2 ] and [ninhydrin]. Increase in the total concentration of CTAB from 0 to 40×10-3 mol·dm-3 resulted in an increase in the pseudo-first-order rate constant (kψ) by a factor of ca 3. Quantitative kinetic analysis of kψ-[CTAB] data was performed on the basis of the pseudo-phase model of the micelles. As added salts induce structural changes in micellar systems that may modify the substrate-surfactant interactions, the effect of some inorganic (NaBr, NaCl, Na2SO4) and organic (NaBenz, NaSal, NaTos) salts on the rate was also explored. It was found that the tightly bound counterions (derived from organic salts) were the most effective. 相似文献
990.
Jain R Shukla D Mehra A 《Langmuir : the ACS journal of surfaces and colloids》2005,21(24):11528-11533
The process of formation of nanoparticles obtained by mixing two micellized, aqueous solutions has been simulated using the Monte Carlo technique. The model includes the phenomena of finite nucleation, growth via intermicellar exchange, and coagulation of nanoparticles after their formation. Using the model, an exploratory study has been conducted to analyze whether the coagulation of nanoparticles is the reason for the formation of nanoparticles whose sizes are comparable to the size of the reverse micelles. The model explains the possible mechanism of coagulation of semiconductor nanoparticles formed within reverse micelles and its effect on the evolution of their size with time. The model is predictive in nature, and the simulation results compare well with those observed experimentally. 相似文献