全文获取类型
收费全文 | 224195篇 |
免费 | 27145篇 |
国内免费 | 16628篇 |
专业分类
化学 | 154228篇 |
晶体学 | 2641篇 |
力学 | 11601篇 |
综合类 | 985篇 |
数学 | 25863篇 |
物理学 | 72650篇 |
出版年
2023年 | 2577篇 |
2022年 | 5049篇 |
2021年 | 5749篇 |
2020年 | 6854篇 |
2019年 | 7932篇 |
2018年 | 6986篇 |
2017年 | 6438篇 |
2016年 | 10740篇 |
2015年 | 9727篇 |
2014年 | 11773篇 |
2013年 | 15249篇 |
2012年 | 15927篇 |
2011年 | 15832篇 |
2010年 | 12674篇 |
2009年 | 12463篇 |
2008年 | 12483篇 |
2007年 | 11107篇 |
2006年 | 10145篇 |
2005年 | 8971篇 |
2004年 | 7516篇 |
2003年 | 6464篇 |
2002年 | 7049篇 |
2001年 | 5817篇 |
2000年 | 5014篇 |
1999年 | 3877篇 |
1998年 | 3215篇 |
1997年 | 2849篇 |
1996年 | 2774篇 |
1995年 | 2403篇 |
1994年 | 2360篇 |
1993年 | 2059篇 |
1992年 | 1924篇 |
1991年 | 1858篇 |
1990年 | 1733篇 |
1989年 | 1523篇 |
1988年 | 1282篇 |
1987年 | 1237篇 |
1986年 | 1204篇 |
1985年 | 1180篇 |
1984年 | 1092篇 |
1983年 | 977篇 |
1982年 | 923篇 |
1981年 | 779篇 |
1979年 | 827篇 |
1978年 | 835篇 |
1977年 | 823篇 |
1976年 | 942篇 |
1975年 | 835篇 |
1974年 | 852篇 |
1973年 | 864篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Optics and Spectroscopy - The relationship between the parameters of quadripoles (mirrors, for example) ensuring the fulfillment of the energy conservation law are considered. Apart from the... 相似文献
32.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献
33.
Li Boyu 《数学学报(英文版)》1991,7(3):247-251
H. Crapo raised in 1982 the following problem: IfP is a complete lattice, is Retr (P) a complete lattice? here Retr (P) denotes the set of all retraction operators onP with the pointwise order, that is,f≤g in Retr (P) ifff(x)≤g(x) for everyx inP. An affirmative answer will be given in the present paper. 相似文献
34.
Yu. K. Voron'ko A. B. Kudryavtsev V. V. Osiko E. V. Sorokin 《Journal of Applied Spectroscopy》1991,55(4):953-957
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991. 相似文献
35.
36.
Zi-Cai Li 《Numerical Methods for Partial Differential Equations》1989,5(4):279-295
The nonconforming combination of Ritz-Galerkin and finite difference methods is presented for solving elliptic boundary value problems with singularities. The Ritz-Galerkin method is used in the subdomains including singularities, the finite difference method is used in the rest of the solution domain. Moreover, on the common boundary of two regions where two different methods are used, the continuity conditions are constrained only on the nodes of difference grids. Theoretical analysis and numerical experiments have shown that average errors of numerical solutions and their generalized derivatives can reach the convergence rate O(h2-δ), where h is the mesh spacing of uniform difference grids, and δ is an arbitrarily small, positive number. This convergence rate is better than O(h), obtained by the nonconforming combination of the Ritz-Galerkin and finite element methods. 相似文献
37.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities. 相似文献
38.
39.
40.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献