全文获取类型
收费全文 | 47555篇 |
免费 | 10232篇 |
国内免费 | 3664篇 |
专业分类
化学 | 49090篇 |
晶体学 | 497篇 |
力学 | 1198篇 |
综合类 | 223篇 |
数学 | 3416篇 |
物理学 | 7027篇 |
出版年
2024年 | 50篇 |
2023年 | 260篇 |
2022年 | 458篇 |
2021年 | 624篇 |
2020年 | 1733篇 |
2019年 | 3021篇 |
2018年 | 1503篇 |
2017年 | 1106篇 |
2016年 | 3885篇 |
2015年 | 4120篇 |
2014年 | 4145篇 |
2013年 | 4842篇 |
2012年 | 3962篇 |
2011年 | 3259篇 |
2010年 | 3710篇 |
2009年 | 3534篇 |
2008年 | 3130篇 |
2007年 | 2442篇 |
2006年 | 2068篇 |
2005年 | 2137篇 |
2004年 | 1917篇 |
2003年 | 1751篇 |
2002年 | 2583篇 |
2001年 | 1810篇 |
2000年 | 1596篇 |
1999年 | 643篇 |
1998年 | 218篇 |
1997年 | 151篇 |
1996年 | 148篇 |
1995年 | 140篇 |
1994年 | 89篇 |
1993年 | 74篇 |
1992年 | 69篇 |
1991年 | 62篇 |
1990年 | 64篇 |
1989年 | 34篇 |
1988年 | 27篇 |
1987年 | 22篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1971年 | 1篇 |
1957年 | 2篇 |
1936年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
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
4.
5.
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
6.
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
7.
We reveal that for a realistic system, interference effects are obtained such as the suppression of central line and inner sidebands and the narrowing of the outer fluorescence sidebands. For this purpose, we consider a spontaneous decay from an excited state to a metastable state when the excited and metastable states are resonantly coupled to an auxiliary metastable state by a laser field and a microwave field, respectively. The fluorescence spectrum evolves from a five-peaked structure into a doublet of ultrasharp lines as the ratio of the laser field Rabi frequency to the microwave Rabi frequency is decreased. The physical origin is presented in terms of dressed states. 相似文献
8.
9.
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
10.
Existence, Multiplicity and Infinite Solvability of Positive Solutions for One-Dimensional p-Laplacian 总被引:5,自引:0,他引:5
Qing Liu YAO 《数学学报(英文版)》2005,21(4):691-698
The existence, multiplicity and infinite solvability of positive solutions are established for some two-point boundary value problems of one-dimensional p-Laplacian. In this paper, by multiplicity we mean the existence of m solutions, where m is an arbitrary natural number. 相似文献