全文获取类型
收费全文 | 154193篇 |
免费 | 14277篇 |
国内免费 | 9013篇 |
专业分类
化学 | 78207篇 |
晶体学 | 1554篇 |
力学 | 11530篇 |
综合类 | 458篇 |
数学 | 40673篇 |
物理学 | 45061篇 |
出版年
2024年 | 177篇 |
2023年 | 1682篇 |
2022年 | 1872篇 |
2021年 | 2792篇 |
2020年 | 3444篇 |
2019年 | 3205篇 |
2018年 | 12480篇 |
2017年 | 12163篇 |
2016年 | 9505篇 |
2015年 | 4619篇 |
2014年 | 4779篇 |
2013年 | 6199篇 |
2012年 | 11010篇 |
2011年 | 17595篇 |
2010年 | 10526篇 |
2009年 | 10621篇 |
2008年 | 11622篇 |
2007年 | 13171篇 |
2006年 | 4520篇 |
2005年 | 4889篇 |
2004年 | 4242篇 |
2003年 | 4109篇 |
2002年 | 2999篇 |
2001年 | 1904篇 |
2000年 | 1843篇 |
1999年 | 1817篇 |
1998年 | 1557篇 |
1997年 | 1507篇 |
1996年 | 1543篇 |
1995年 | 1230篇 |
1994年 | 1032篇 |
1993年 | 905篇 |
1992年 | 760篇 |
1991年 | 673篇 |
1990年 | 581篇 |
1989年 | 463篇 |
1988年 | 429篇 |
1987年 | 338篇 |
1986年 | 325篇 |
1985年 | 263篇 |
1984年 | 196篇 |
1983年 | 152篇 |
1982年 | 134篇 |
1981年 | 113篇 |
1980年 | 125篇 |
1979年 | 92篇 |
1978年 | 84篇 |
1977年 | 66篇 |
1976年 | 53篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
Peng-Yan Gui Xiao-Hui Yan Wen-Juan Yuan Yuan-Liang Ma Xiao Ding Shuai Liu 《Natural product research》2019,33(19):2830-2836
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme. 相似文献
73.
Acta Mathematica Sinica, English Series - We are interested in the existence and asymptotic behavior for the least energy solutions of the following fractional eigenvalue problem $$\left({\rm{P}}... 相似文献
74.
Jia Tian-Cong Guo Jin-Tao Wang Zhen Zhu Xiao-Shan Zhang Qian-Xin Chen Ping Yao Kun Lv Wen-Ying Liu Guo-Guang 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(3):823-829
Journal of Radioanalytical and Nuclear Chemistry - In the present work the final products of coumarin radiation chemical transformation are investigated by chromatography. During radiolysis of... 相似文献
75.
Luo Dajuan Liu Bingqian Gao Rong Su Lixia Su Yonghuan 《Journal of Solid State Electrochemistry》2022,26(3):749-759
Journal of Solid State Electrochemistry - Cortisol, a steroid hormone, has been confirmed as a kind of biomarker that reflects the stress response of psychobiology and related adverse health... 相似文献
76.
An oriented tetrahedron defined on four vertices is a set of four cyclic triples with the property that any ordered pair of vertices is contained in exactly one of the cyclic triples. A tetrahedral quadruple system of order with index , denoted by , is a pair , where is an ‐set and is a set of oriented tetrahedra (blocks) such that every cyclic triple on is contained in exactly members of . A is pure if there do not exist two blocks with the same vertex set. When , the spectrum of a pure TQS has been completely determined by Ji. In this paper, we show that there exists a pure if and only if and . A corollary is that a simple also exists if and only if and . 相似文献
77.
Over the past two decades, advanced materials with hollow interiors have received significant attention in materials research owing to their great application potential across a vast number of technological fields. Though with great difficulty, multi-shelled hollow metal–organic frameworks (MSHMs) have also been successfully synthesized in recent years. Herein, a rational shell-by-shell soft-templating protocol has been devised to fabricate highly uniform multi-shelled hollow cobalt-imidazole-based MOF (ZIF-67). For the first time, it has become possible to endow mesoporosity to this new type of functional material (i.e., mesoporous MOFs). When used as carrier materials in catalytic reactions, in principle, these mesoporous MSHMs with high surface area not only improve the dispersity of metal nanoparticles (NPs), but also efficiently facilitate the mass diffusion of the reactions, resulting in enhanced catalyst activity. Moreover, the obtained MSHMs/M nanocomposites serve as base-metal bifunctional catalysts for one-pot oxidation-Knoevenagel condensation cascade reaction, in which the MSHMs itself serves as a pristine active catalyst in addition to its role of catalyst support. The results demonstrate that excellent multifunctional catalysts can be achieved via preparing intrinsically microporous bulk MOFs into extrinsically mesoporous MSHMs which possess many structural merits that conventional bulk MOFs do not have. 相似文献
78.
基于密度泛函理论的第一性原理计算方法,本文研究了高压对β-InSe弹性常数、机械性能和电子结构的影响.在0~20 GPa范围内,随着压力的增大,β-InSe的晶格常数、晶胞体积逐渐减小,结构参数a/a_0、c/c_0、V/V_0单调减小.在0~12 GPa范围内,弹性模量G、E、B和泊松比v随着压力增大而增大,在16 GPa时大幅减小,G、E、B分别减小了34.9%、53.3%、82.9%.随着压力增大,Se-In和In-In原子之间的电荷密度增大,Se-In原子之间的共价键增强,层间距减小.而且,β-InSe在20 GPa时带隙消失,发生了半导体向半金属的相变. 相似文献
79.
80.