全文获取类型
收费全文 | 104290篇 |
免费 | 16639篇 |
国内免费 | 11871篇 |
专业分类
化学 | 72732篇 |
晶体学 | 1137篇 |
力学 | 5914篇 |
综合类 | 676篇 |
数学 | 12679篇 |
物理学 | 39662篇 |
出版年
2024年 | 352篇 |
2023年 | 2074篇 |
2022年 | 3670篇 |
2021年 | 3960篇 |
2020年 | 4187篇 |
2019年 | 3967篇 |
2018年 | 3718篇 |
2017年 | 3341篇 |
2016年 | 5028篇 |
2015年 | 4932篇 |
2014年 | 6060篇 |
2013年 | 7788篇 |
2012年 | 9291篇 |
2011年 | 9497篇 |
2010年 | 6634篇 |
2009年 | 6370篇 |
2008年 | 6686篇 |
2007年 | 5977篇 |
2006年 | 5589篇 |
2005年 | 4672篇 |
2004年 | 3656篇 |
2003年 | 2937篇 |
2002年 | 2669篇 |
2001年 | 2234篇 |
2000年 | 1949篇 |
1999年 | 2065篇 |
1998年 | 1750篇 |
1997年 | 1569篇 |
1996年 | 1563篇 |
1995年 | 1376篇 |
1994年 | 1241篇 |
1993年 | 1008篇 |
1992年 | 905篇 |
1991年 | 778篇 |
1990年 | 652篇 |
1989年 | 503篇 |
1988年 | 379篇 |
1987年 | 341篇 |
1986年 | 337篇 |
1985年 | 263篇 |
1984年 | 189篇 |
1983年 | 154篇 |
1982年 | 127篇 |
1981年 | 80篇 |
1980年 | 59篇 |
1979年 | 26篇 |
1978年 | 22篇 |
1976年 | 22篇 |
1975年 | 22篇 |
1957年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
Yanzhe Li 《数学学报(英文版)》2015,31(9):1424-1434
This paper studies the quasisymmetric mappings on Moran sets. We introduce a generalized form of weak quasisymmetry and prove that, on Moran set satisfying the small gap condition, a generalized weakly quasisymmetric mapping is quasisymmetric. We further give a criterion for the quasisymmetry of mappings between Moran sets with some regular structure. 相似文献
995.
The research provides a novel approach for producing diarylmethane derivatives using CB[7]–NaCl–PdCl2 catalyzed Suzuki cross-coupling reaction of benzyl chloride derivatives and arylboronic acids in ethanol aqueous solution. 相似文献
996.
Two new silver(I) trans‐cinnamates, namely [Ag(2‐cca)(H2O)]2 ( 1 ) and [Ag(4‐cca)]n ( 2 ) (2‐ccaH = 2‐chlorocinnamic acid and 4‐ccaH = 4‐chlorocinnamic acid), were synthesized and structurally characterized. Single crystal X‐ray studies reveal that each silver(I) atom in 1 is two‐coordinate by a 2‐chlorocinnamate ligand and one water molecule to afford a discrete centrosymmetric dimer with the ligand‐unsupported Ag···Ag interactions (3.218(4) Å), while a pair of symmetry‐related silver(I) atoms in 2 are clamped by two μ2‐η1:η1 4‐chlorocinnamate ligands to yield a binuclear silver(I) moiety incorporating a ligand‐supported Ag···Ag interaction (2.819(5) Å). Both complexes 1 and 2 show potent urease inhibitory activities with the respective IC50 values of 0.66 and 1.10 μM. 相似文献
997.
Jia‐Xuan Yan Hu Li Xiang‐Wei Liu Jiang‐Ling Shi Xin Wang Zhang‐Jie Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(19):5045-5049
3,4‐Dihydroquinolinones were synthesized by the palladium‐catalyzed, oxidative‐addition‐initiated activation and arylation of inert C(sp3) H bonds. Pd(OAc)2 and P(o‐tol)3 were used as the catalyst and ligand, respectively, to improve the efficiency of the reaction. A further advantage of this reaction is that it could be performed in air. A relatively rare seven‐membered palladacycle was proposed as a key intermediate of the catalytic cycle. 相似文献
998.
Xue‐Jun Wu Xiao Huang Xiaoying Qi Hai Li Bing Li Hua Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(34):9075-9079
Two‐dimensional (2D) copper‐based ternary and quaternary semiconductors are promising building blocks for the construction of efficient solution‐processed photovoltaic devices at low cost. However, the facile synthesis of such 2D nanoplates with well‐defined shape and uniform size remains a challenge. Reported herein is a universal template‐mediated method for preparing copper‐based ternary and quaternary chalcogenide nanoplates, that is, CuInS2, CuInxGa1−xS2, and Cu2ZnSnS4, by using a pre‐synthesized CuS nanoplate as the starting template. The various synthesized nanoplates are monophasic with uniform thickness and lateral size. As a proof of concept, the Cu2ZnSnS4 nanoplates were immobilized on a Mo/glass substrate and used as semiconductor photoelectrode, thus showing stable photoelectrochemical response. The method is general and provides future opportunities for fabrication of cost‐effective photovoltaic devices based on 2D semiconductors. 相似文献
999.
Qian Li Matthias Driess John F. Hartwig 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(32):8611-8614
Reported herein is an iridium‐catalyzed, regioselective silylation of the aromatic C H bonds of benzylamines and the benzylic C H bonds of 2,N‐dialkylanilines. In this process, (hydrido)silyl amines, generated in situ by dehydrogenative coupling of benzylamine or aniline with diethylsilane, undergo selective silylation at the C H bond γ to the amino group. The products of this silylation are suitable for subsequent oxidation, halogenation, and cross‐coupling reactions to deliver benzylamine and arylamine derivatives. 相似文献
1000.