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991.
One‐pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Catalysed by Cupric Acetate under Solvent‐free Conditions 下载免费PDF全文
Chingrishon Kathing Jims World Star Rani Nongthombam Geetmani Singh Shokip Tumtin Ridaphun Nongrum Rishanlang Nongkhlaw 《中国化学会会志》2014,61(11):1254-1258
A solvent‐free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones from aromatic aldehydes, β‐keto ester/acetyl acetone and urea catalysed by cupric acetate under thermal condition is reported as a simple and an efficient protocol. Compared with classical Biginelli reaction reported in 1893, this new method provides much improved modification in terms of yield and reaction time. The usage of milder catalyst, environmental friendly procedures and excellent yields within a very short time (5–15 min) are the advantages of the method in which the involvement of solvent‐free condition adds an edge to the method. Thus, the efficiency of the protocol enabled the rapid synthesis of 3,4‐dihydropyrimidin‐2(1H)‐one derivatives in a short duration. 相似文献
992.
Dheer Singh Anju Chopra Ravindra Kumar M. I. S. Sastry M. B. Patel B. Basu 《Chromatographia》2014,77(1-2):165-169
EN 14103 is generally used for quantification of ester content in biodiesel free of heptadecanoate ester (C17:0) or methyl nonadecanoate (C19:0), which are employed as internal standards. It was observed that ester content obtained by EN 14103 method did not match with theoretical value of biodiesel, as the method did not take care of response factors of each component to compensate for changes in detector sensitivities. In this study, the whole range of fatty acid (C6–C24:1) methyl esters have been taken into consideration for the calculation of the ester content. Methyl nonadecanoate (C19:0) was used as an internal standard. The response factors of both the saturated and unsaturated methyl esters in the range C6–C24:1 were estimated and found in the range 0.97–1.16. The ester content was calculated after applying the response factors of each methyl ester. The results obtained by this method agreed well with the theoretical value as compared to estimated value using EN14103 method. The results obtained from this method also show good correlation (R 2 = 0.98) with 1H-NMR method. Further, this method does not depend on nature of biodiesel feed stock and is applicable to all methyl biodiesel samples obtained from different raw materials. 相似文献
993.
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995.
Harshadas Mitaram Meshram Palakuri RameshBandi Chennakesava Reddy Balasubramanian SridharJhillu Singh Yadav 《Tetrahedron》2011,67(17):3150-3155
An efficient vinylogous Mukaiyama aldol reaction (VMAR) of 2-(trimethylsilyloxy)furan with various (N-alkyl)isatins is described in the presence of lanthanum(III) triflates (5 mol %). The reaction proceeds rapidly and affords the corresponding 3-hydroxy-(5-oxo-2,5-dihydrofuran-2-yl)indolin-2-one in high yields with good diastereoselectivities (threo:erythro ratio up to ≤95:5). 相似文献
996.
We synthesized a novel 1,3,5-substituted triethylbenzene derivative with a benzimidazole moiety as a binding and signalling subunit. The triethylbenzene platform was judiciously incorporated into the receptor design such that all the fluorophores are in close proximity to each other in order to facilitate stacking. The advantage of this approach lies in the fact that the receptor will offer a dual channel emission for the multiple ratiometric determination of metal ions. The sensor was tested in a CH3CN/H2O (7:3, v/v, pH 7.1) HEPES buffered solution and successfully developed for the ratiometric and simultaneous estimation of Fe3+ and Cu2+ ions in aqueous samples. 相似文献
997.
We synthesized a novel benzimidazole-based, anthracene-coupled fluorescent receptor capable of recognizing and estimating the concentrations of Fe3+ in semi-aqueous solution by ratiometric estimation. Our sensor can be made highly selective for Fe3+ over other metal ions by changing the solvent composition. 相似文献
998.
Suresh AlluNagaraju Molleti Ramachandrarao PanemVinod K. Singh 《Tetrahedron letters》2011,52(32):4080-4083
Enantioselective organocatalytic direct aldol reaction of unactivated ketones with various isatin derivatives was developed using cinchonine based urea ligand employing a noncovalent catalysis mechanism. Using this protocol we can access functionalized 3-alkyl-3-hydroxyindolin-2-ones in high yields with good to excellent enantioselectivities. 相似文献
999.
Bhagwat PrasadAmit Garg Hardik TakwaniSaranjit Singh 《Trends in analytical chemistry : TRAC》2011,30(2):360-387
Metabolite identification (Met ID) is important during the early stages of drug discovery and development, as the metabolic products may be pharmacologically active or toxic in nature. Liquid chromatography-mass spectrometry (LC-MS) has a towering role in metabolism research.This review discusses current approaches and recent advances in using LC-MS for Met ID. We critically assess and compare various mass spectrometers, highlighting their strengths and limitations. Citing appropriate examples, we cover recent LC and ion sources, isotopic-pattern matching, hydrogen/deuterium-exchange MS, data dependent analyses, MSE, mass defect filter, 2D and 3D approaches for the elucidation of molecular formula, polarity switching, and background-subtraction and noise-reduction algorithms. A flow chart outlines a comprehensive strategy for Met ID, including a focus on reactive metabolites. 相似文献
1000.
S. Biswas P. N. Pathak D. K. Singh S. B. Roy V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):557-564
The extraction of U(VI) from sulphate medium with 2-ethylhexyl phosphonic acid-mono-2-ethylhexyl ester (PC88A, H2A2 in dimeric form) in n-dodecane has been investigated under varying concentrations of sulphuric acid and uranium. Slope analysis of uranium (VI)
distribution data as a function of PC88A concentration suggests the formation of monomeric species, viz. UO2(HA2)2. This observation was further supported by the mathematical expression obtained during non-linear least square regression
analysis of U(VI) distribution data correlating the percentage extraction (%E) and the acidity (H
i). A mathematical model correlating the experimental distribution ratio values of U(VI) (D
U) with initial acidity (H
i) and initial uranium concentrations (C
i) was developed:
D\textU = 12.98( ±0.90)/{ C\texti - 0.75( ±0.05) ×[ H\texti ]2 } D_{\text{U}} = 12.98( \pm 0.90)/\left\{ {C_{\text{i}}^{ - 0.75( \pm 0.05)} \times \left[ {H_{\text{i}} } \right]^{2} } \right\} . This expression can be used to predict the concentration of uranium in organic as well as in aqueous phase at any C
i and H
i. The extraction data were used to calculate the conditional extraction constant (K
ex) values at different acidities (2–7 M H+), uranium (0.02–0.1 M) and PC88A (0.2–0.6 M) concentrations. These studies were also extended for the extraction of U(VI)
using synergistic mixtures of PC88A and TOPO from sulphate medium. 相似文献