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261.
应用比较分子力场分析 (Co MFA)方法研究 4 -肟醚基喹唑啉类化合物抗烟草花叶病毒活性的三维构效关系 (3 D-QSAR) ,引入分子的摩尔折射率 (MR)和偶极矩 (DIPOLE)分别作为 Co MFA的第三和第四个场 .在此基础上进行偏最小二乘 (PLS)分析 :交叉验证 (leave-one-out)结果为 r2cv=0 .4 43 ,非交叉验证 (novalidation)结果为 r2 =0 .93 2 ,说明所建立的模型有较好的可靠性 ,并且在三维等值线图的基础上得到了一个此类化合物的模拟作用模型 ,据此可生长出一系列先导分子 相似文献
262.
263.
1 INTRODUCTION The interest in the complexes of transition met-als with ketoxime ligands[1, 2] as potential modelsfor metal binding sites in ferroverdin[3, 4] hasprompted the investigations on the structures andthe overall coordination geometry of the metalcenters in these complexes. Oxime derivatives areinteresting ligands since the ketoximes are foundto chelate transition metals through the N (oxime)and O (ketone) donors[5~10]. Herein we report thesynthesis… 相似文献
264.
《Analytical letters》2012,45(10):683-694
Abstract Oxime derivatives (methoxime, benzyloxime, trimethylsilyloxime) of 17-ketosteroids will, under some gas chromatographic conditions, undergo Beckmann fission in the injector zone. The result of this effect is partial or total conversion of the steroid derivative to a nitrile. Since oxime derivatives are widely used in gas chromatography for steroids and other compounds, it is important to recognize that this reaction may occur. In analytical separations conditions which do not lead to the fission reaction should be maintained. 相似文献
265.
Fatemeh Azarakhshi Davood Nori-Shargh Nasrin Masnabadi Hooriye Yahyaei Seiedeh Negar Mousavi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):276-293
Abstract The impacts of the generalized anomeric effect (GAE) and gauche effect (GE) associated with donor–acceptor electron delocalizations and dipole–dipole interactions on the conformational properties of 2-methoxy- (1), 2-methylthio- (2), 2-methylseleno- (3), 2-fluoro- (4), 2-chloro- (5), and 2-bromocyclohexanone oxime (6) have been studied by means of hybrid density functional theory (B3LYP/6–311+G**) and ab initio molecular orbital (HF/6–311+G**)-based methods and natural bond orbital (NBO) interpretation. Both methods used showed that the above compounds exist predominantly in the axial chair conformation and the axial conformation stability increased from 2-methoxy- (1) to 2-methylselenocyclohexanone oxime (3) and also from 2-fluoro- (4) to 2-bromocyclohexanone oxime (6). The NBO analysis showed that the GAE increases from compound 1 to compound 3 and also from compound 4 to compound 6. GE does not have significant impact on the conformational behaviors of compounds 1–6 and GAE succeeds in accounting qualitatively for the increase of the axial preferences in both series of compounds. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Table S1. Supporting Information Available. The structures optimized and thermodynamic functions of the axial and equatorial conformations of compounds 1–6. This material is available free of charge via the Internet. 相似文献
266.
Xiaohong Liu Xiaohua Stella Huang Ny Sin Brian L. Venables Vikram Roongta 《Magnetic resonance in chemistry : MRC》2010,48(11):873-876
In this article, we describe the characteristic 15N chemical shifts of isatin oxime ethers and their isomer nitrone. These oxime ethers and nitrones are the alkylation reaction products of isatin oximes. In our study, the 15N chemical shifts observed in these oxime ethers were in the 402–408 (or 22–28) ppm range, although those for their corresponding nitrone series were in the 280–320 (or ?100 to ?60) ppm range. This remarkable difference in 15N NMR chemical shift values could potentially be used to determine the O‐ versus N‐alkylation of oximes, even when only one isomer is available. In this paper, the differences in 15N NMR chemical shifts serve as the basis for a discussion about how to distinguish both regioisomers derived from the oximes alkylation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
267.
A. Srinivasa K. M. Mahadevan P. Prabhakara Varma A. Sudhakara 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1843-1853
A novel one-pot Fischer indole synthesis approach has been developed by using antimony (III) sulfate as the catalyst. Good yields were obtained after reacting phenylhydrazines hydrochlorides and ketones in refluxing methanol. The exclusive formation of 2,3- disubstituted indoles was observed in the reaction of ethyl methyl ketone with phenylhydrazines. One-pot synthesis of indole-3-propanol using dihydropyran has also been described. The use of reusable antimony (III) sulfate as a catalyst makes this method both economically and environmentally friendly. 相似文献
268.
Oxidative deprotection of silylethers, acetals and ketals to their corresponding alcohols, aldehydes and ketones have been achieved using oxygen or air in the presence of cobalt and manganese salts of 4-aminobenzoic acid supported an silica gel as catalysts. Reactions are clean and catalysts can be recovered easily and reused repeatedly. 相似文献
269.
Three new symmetrical pregnenolone oxyminyl oxalate dimers (8–10) were synthesized from the corresponding pregnenolone oximes (3, 5, and 7) at room temperature. All dimers were characterised by spectroscopic means, notably HRFABMS and comprehensive NMR spectroscopic
data analyses.
Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 250–252, May–June, 2008. 相似文献
270.