全文获取类型
收费全文 | 35053篇 |
免费 | 9594篇 |
国内免费 | 1396篇 |
专业分类
化学 | 41060篇 |
晶体学 | 312篇 |
力学 | 450篇 |
综合类 | 1篇 |
数学 | 1887篇 |
物理学 | 2333篇 |
出版年
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 154篇 |
2020年 | 1239篇 |
2019年 | 2583篇 |
2018年 | 1011篇 |
2017年 | 651篇 |
2016年 | 3361篇 |
2015年 | 3527篇 |
2014年 | 3435篇 |
2013年 | 4057篇 |
2012年 | 2937篇 |
2011年 | 2128篇 |
2010年 | 2819篇 |
2009年 | 2804篇 |
2008年 | 2341篇 |
2007年 | 1721篇 |
2006年 | 1419篇 |
2005年 | 1600篇 |
2004年 | 1400篇 |
2003年 | 1291篇 |
2002年 | 1980篇 |
2001年 | 1361篇 |
2000年 | 1301篇 |
1999年 | 369篇 |
1998年 | 44篇 |
1997年 | 31篇 |
1996年 | 29篇 |
1995年 | 21篇 |
1994年 | 24篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 22篇 |
1985年 | 21篇 |
1984年 | 20篇 |
1982年 | 11篇 |
1981年 | 24篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 16篇 |
1977年 | 21篇 |
1976年 | 15篇 |
1975年 | 14篇 |
1974年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
41.
42.
43.
We study the nonrelativistic limit of the Cauchy problem for the nonlinear Klein-Gordon equation and prove that any finite
energy solution converges to the corresponding solution of the nonlinear Schr?dinger equation in the energy space, after the
infinite oscillation in time is removed. We also derive the optimal rate of convergence in .
Received: 13 July 2000 / Published online: 1 February 2002 相似文献
44.
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
45.
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
46.
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
47.
Jong Chan Lee Jin Young Park So Young Yoon Yong Hun Bae Seung Jun Lee 《Tetrahedron letters》2004,45(1):191-193
A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described. 相似文献
48.
49.
50.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献