全文获取类型
收费全文 | 35406篇 |
免费 | 9578篇 |
国内免费 | 1398篇 |
专业分类
化学 | 41133篇 |
晶体学 | 319篇 |
力学 | 457篇 |
数学 | 2152篇 |
物理学 | 2321篇 |
出版年
2023年 | 10篇 |
2022年 | 25篇 |
2021年 | 186篇 |
2020年 | 1253篇 |
2019年 | 2593篇 |
2018年 | 1027篇 |
2017年 | 662篇 |
2016年 | 3387篇 |
2015年 | 3527篇 |
2014年 | 3451篇 |
2013年 | 4066篇 |
2012年 | 2942篇 |
2011年 | 2187篇 |
2010年 | 2849篇 |
2009年 | 2839篇 |
2008年 | 2380篇 |
2007年 | 1758篇 |
2006年 | 1448篇 |
2005年 | 1634篇 |
2004年 | 1441篇 |
2003年 | 1330篇 |
2002年 | 2005篇 |
2001年 | 1364篇 |
2000年 | 1282篇 |
1999年 | 369篇 |
1998年 | 56篇 |
1997年 | 44篇 |
1996年 | 28篇 |
1995年 | 18篇 |
1994年 | 7篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1966年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
41.
42.
43.
44.
In this Note we give a necessary and sufficient condition for the spectral controllability from one simple node of a general network of strings that undergoes transversal vibrations in a sufficiently large time. This condition asserts that no eigenfunction vanishes identically on the string that contains the controlled node. The proof combines the Beurling–Malliavin's theorem and an asymptotic formula for the eigenvalues of the network. The optimal control time may be characterized as twice the sum of the lengths of all the strings of the network. To cite this article: R. Dáger, E. Zuazua, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 545–550. 相似文献
45.
46.
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
47.
Wen Zhang Hui Huang Yu Ding Margherita Gavagnin Ernesto Mollo Guido Cimino Yue‐Wei Guo 《Helvetica chimica acta》2006,89(4):813-820
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds. 相似文献
48.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
49.
Enrique Fernández-Cara Sergio Guerrero Oleg Yurievich Imanuvilov Jean-Pierre Puel 《Comptes Rendus Mathematique》2004,338(5):375-380
This Note deals with the controllability of Stokes and Navier–Stokes systems with distributed controls with support in possibly small subdomains. We first present a new global Carleman inequality for the solutions to Stokes-like systems that leads to the null controllability at any time T>0. Then, we present a local result concerning exact controllability to trajectories of the Navier–Stokes system. To cite this article: E. Fernández-Cara et al., C. R. Acad. Sci. Paris, Ser. I 338 (2004). 相似文献