全文获取类型
收费全文 | 98753篇 |
免费 | 5714篇 |
国内免费 | 4652篇 |
专业分类
化学 | 56238篇 |
晶体学 | 1331篇 |
力学 | 5582篇 |
综合类 | 322篇 |
数学 | 11837篇 |
物理学 | 33809篇 |
出版年
2023年 | 750篇 |
2022年 | 1710篇 |
2021年 | 2053篇 |
2020年 | 2310篇 |
2019年 | 2506篇 |
2018年 | 2892篇 |
2017年 | 2823篇 |
2016年 | 3486篇 |
2015年 | 2410篇 |
2014年 | 3478篇 |
2013年 | 4917篇 |
2012年 | 5060篇 |
2011年 | 5360篇 |
2010年 | 4254篇 |
2009年 | 4259篇 |
2008年 | 4455篇 |
2007年 | 4181篇 |
2006年 | 3809篇 |
2005年 | 3378篇 |
2004年 | 3036篇 |
2003年 | 2713篇 |
2002年 | 2831篇 |
2001年 | 2549篇 |
2000年 | 1989篇 |
1999年 | 1602篇 |
1998年 | 1534篇 |
1997年 | 1330篇 |
1996年 | 1294篇 |
1995年 | 1078篇 |
1994年 | 1156篇 |
1993年 | 1097篇 |
1992年 | 1062篇 |
1991年 | 1124篇 |
1990年 | 1118篇 |
1989年 | 1039篇 |
1988年 | 917篇 |
1987年 | 915篇 |
1986年 | 881篇 |
1985年 | 921篇 |
1984年 | 915篇 |
1983年 | 822篇 |
1982年 | 800篇 |
1979年 | 801篇 |
1978年 | 814篇 |
1977年 | 806篇 |
1976年 | 919篇 |
1975年 | 812篇 |
1974年 | 844篇 |
1973年 | 847篇 |
1972年 | 752篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
V. P. Borovik I. Yu. Bagryanskaya Yu. V. Gatilov O. P. Shkurko 《Journal of Structural Chemistry》2003,44(4):650-654
The crystal structures of 2-amino-4-phenyl-9H-pyrimido[4,5-b]indole and its nitrate were determined by XRD analysis. 13C NMR, XRD, and quantum-chemical data indicate that the acid proton is predominantly localized at the N(3) atom of the pyrimidine ring in both isolated nitrate molecules and in molecules in crystal and solution. 相似文献
992.
It was found experimentally that stacking defects formed in the mechanochemical activation of zinc ferrite enhanced the specific catalytic activity in the reaction of CO oxidation. The specific rate of CO oxidation was a linear function of defect concentration, which was determined using Mössbauer spectroscopy and X-ray diffraction. A conclusion was drawn that the same centers are responsible for an increase in the catalytic activity, the sorption capacity for hydrogen sulfide, and the reactivity of zinc ferrite in the interaction with hydrochloric acid. It was assumed that analogous factors caused an increase in the catalytic activity and reactivity of magnesium ferrite. 相似文献
993.
The results of a kinetic study of model reactions between substituted phenols and bromobenzene in the presence of potassium carbonate and the copper(I) chloride–8-hydroxyquinoline catalytic complex in N,N-dimethylformamide are presented. The reactions were found to obey a first-order rate law. Both orbital and charge interactions should be taken into account in a consideration of the effect of the structural characteristics of reactants on the rate of reaction. The kinetics of substitution of the phenoxide anion for an aromatically bound halogen atom in activated and nonactivated systems with the formation of practically valuable aryl ethers were comparatively studied. The results presented provide an opportunity to distinguish the common features and regularities of activated and nonactivated aromatic substitution in the test systems. 相似文献
994.
An indirect laser photoacoustic technique is described. The basic principle, the experimental set-up and the influencing factors are discussed in detail. This method was used to quantify phenylamine, arginine and methylene blue on membranes. The linear ranges of the calibration curve are up to two orders of magnitude. With 1 microliter of sample solution, the detection limits are 0.25, 1.52 and 0.14 pmol for phenylamine, arginine and methylene blue, respectively. 相似文献
995.
S. Yu. Kudryashov Yu. G. Kuraeva L. A. Onuchak 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(7):1115-1118
The thermodynamic characteristics of adsorption of several organic compounds on the carbon adsorbent Carbopack B before and after its modification by a monomolecular layer of cholesteryl-n-pentyl oxybenzoate were determined by gas chromatography. The initial adsorbent was close in its properties to graphitized carbon black. Modification weakened adsorbate-adsorbent attraction and increased the mobility of adsorbed molecules, to a greater extent for nonpolar adsorbents and to a lesser extent for compounds capable of specifically interacting with modifier molecules. 相似文献
996.
997.
998.
999.
Yu. N. Belokon' T. F. Savel'eva E. A. Paskonova V. M. Belikov 《Russian Chemical Bulletin》1977,26(12):2514-2518
1000.