全文获取类型
收费全文 | 148067篇 |
免费 | 13592篇 |
国内免费 | 10271篇 |
专业分类
化学 | 90844篇 |
晶体学 | 1945篇 |
力学 | 8608篇 |
综合类 | 675篇 |
数学 | 17974篇 |
物理学 | 51884篇 |
出版年
2023年 | 1650篇 |
2022年 | 3057篇 |
2021年 | 3776篇 |
2020年 | 4365篇 |
2019年 | 4424篇 |
2018年 | 4473篇 |
2017年 | 4429篇 |
2016年 | 5830篇 |
2015年 | 4684篇 |
2014年 | 6275篇 |
2013年 | 8524篇 |
2012年 | 9496篇 |
2011年 | 9906篇 |
2010年 | 7465篇 |
2009年 | 7317篇 |
2008年 | 7731篇 |
2007年 | 7093篇 |
2006年 | 6383篇 |
2005年 | 5618篇 |
2004年 | 4756篇 |
2003年 | 4121篇 |
2002年 | 4206篇 |
2001年 | 3666篇 |
2000年 | 2918篇 |
1999年 | 2648篇 |
1998年 | 2380篇 |
1997年 | 2122篇 |
1996年 | 2082篇 |
1995年 | 1799篇 |
1994年 | 1766篇 |
1993年 | 1603篇 |
1992年 | 1488篇 |
1991年 | 1517篇 |
1990年 | 1441篇 |
1989年 | 1274篇 |
1988年 | 1089篇 |
1987年 | 1074篇 |
1986年 | 1033篇 |
1985年 | 1060篇 |
1984年 | 998篇 |
1983年 | 913篇 |
1982年 | 855篇 |
1979年 | 817篇 |
1978年 | 820篇 |
1977年 | 824篇 |
1976年 | 939篇 |
1975年 | 833篇 |
1974年 | 850篇 |
1973年 | 863篇 |
1972年 | 771篇 |
排序方式: 共有10000条查询结果,搜索用时 437 毫秒
991.
992.
M. R. Nuriddinova V. M. Malikov A. Yu. Kushmuradov A. I. Saidkhodzhaev 《Chemistry of Natural Compounds》1992,28(6):551-552
A microcolumn HPLC fingerprint method has been developed for the epigeal organs ofFerula kuhistanica andF. tenuisecta. The possibility has been shown of control by the microcolumn HPLC method of the qualitative and quantitative yields of ferutinin
in the initial plant raw material and in preparations extracted from it, and also at each stage of the isolation of the desired
product. The method is universal and does not depend on species and chemical composition of the plant.
Institute of the Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh
Soedinenii, No. 6, pp. 635–636, November–December, 1992. 相似文献
993.
Gas-phase cigarette smoke (GPCS) was able to induce lipid peroxidation in lecithin liposomes, rat liver microsomes, and rat lung cells (RLC), and change the membrane fluidity of RLCs. Lipid free radicals were trapped in a GPCS-treated microsomal suspension by using 4-POBN as the spin trap. In addition, it was found that GPCS-peroxidized liposomes in appropriate degree of lipid peroxidation had the ability to increase the generation of superoxide anions in rat peritoneal neutrophils (RPN). Effects of green tea polyphenols (GTP) on the GPCS-induced damages were investigated The results showed that GTP was capable of inhibiting the GPCS-induced damages. 相似文献
994.
Based on the Kachanov method and the alternating iteration technique, a new method is proposed to deal with the problem of the strongly interacted multiple cracks in an infinite plate. Unlike the Kachanov method which neglects the interaction of the tractions of the non-uniform components, the tractions of the non-uniform components on the surfaces of cracks are considered through the alternating technique. The accuracy and efficiency of present method are validated by comparing the results of two collinear and two parallel overlapped open the cracks obtained by the present method with those of the exact solutions, the results of the Kachanov method and the alternating iteration technique. Applications of present method in solving sliding close crack problems and evaluating the plastic zones demonstrate the versatility of present method. 相似文献
995.
The mechanisms of liquid-phase phenol ozonation are revised. A new mechanism in which a significant role is played by free-radical reactions is suggested for this process. 相似文献
996.
V. L. Bratman Yu. K. Kalynov V. N. Manuilov S. V. Samsonov 《Radiophysics and Quantum Electronics》2005,48(10-11):731-736
We develop a thermionic-emission electron-optical system forming a dense beam of electrons moving along helical trajectories round the axis of a gyrotron cavity. The maximum beam current is 4 A and the pitch-factor of electrons is 1.0 for a particle energy of 250 keV and a pulse duration of 10 µs. Using such a beam in a gyrotron operated at the third cyclotron harmonic, we obtain single-mode oscillation with a power of 10 µs in the TE3,8 and TE3,9 modes with frequencies 371 and 414 GHz, respectively. 相似文献
997.
Yu. A. Tserkovnikov 《Theoretical and Mathematical Physics》1992,93(3):1367-1402
A degenerate weakly nonideal Bose gas is investigated at temperatures near zero. Relations connecting the irreducible Green's functions are used to obtain exact expressions for the two-time temperature-dependent Green's functions. In the case of weak nonideality an expression possessing interpolation properties with respect to the frequency and momentum is obtained for the density—density Green's function. At low frequencies, the results of two-fluid hydrodynamics are reproduced. At wavelengths less than the mean free path the energy of the elementary excitations and the damping obtained in the paper agree with the results of perturbation theory with respect to the coupling constant. An expression for the operator of the superfluid velocity is obtained.In memory of Nikolai Nikolaevich BogolyubovV. A. Steklov Mathematics Institute, Russian Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 93, No. 3, pp. 412–465, December, 1992. 相似文献
998.
999.
1000.
原伊鲁烷型倍半萜醇芳香酸酯的碳谱研究 总被引:4,自引:0,他引:4
作者自人工发酵得到的蜜环菌Armillaria mellea (Vahl.ex Fr.) Quel.菌丝体中分离出十七个原伊鲁烷型倍半萜醇芳香酸翻,在研究这些化合物的化学结构中,对其全去偶碳谱,偏共振谱或INEPT谱,C-H COSY谱和远程C-H COSY谱进行比较仔细地分析,指定了每个化合物各碳的归属,讨论了其碳谱的特征,并指出13C NMR谱是对新的该类型化合物结构测定的有效方法. 相似文献