全文获取类型
收费全文 | 341550篇 |
免费 | 10745篇 |
国内免费 | 5327篇 |
专业分类
化学 | 189654篇 |
晶体学 | 3875篇 |
力学 | 15219篇 |
综合类 | 292篇 |
数学 | 40310篇 |
物理学 | 108272篇 |
出版年
2021年 | 2641篇 |
2020年 | 3416篇 |
2019年 | 3306篇 |
2018年 | 3170篇 |
2017年 | 2984篇 |
2016年 | 5531篇 |
2015年 | 4886篇 |
2014年 | 6443篇 |
2013年 | 16510篇 |
2012年 | 13789篇 |
2011年 | 16578篇 |
2010年 | 10469篇 |
2009年 | 10425篇 |
2008年 | 14701篇 |
2007年 | 14685篇 |
2006年 | 14220篇 |
2005年 | 12716篇 |
2004年 | 11216篇 |
2003年 | 9698篇 |
2002年 | 8859篇 |
2001年 | 10371篇 |
2000年 | 7871篇 |
1999年 | 6258篇 |
1998年 | 4953篇 |
1997年 | 4930篇 |
1996年 | 4932篇 |
1995年 | 4828篇 |
1994年 | 4508篇 |
1993年 | 4242篇 |
1992年 | 4709篇 |
1991年 | 4494篇 |
1990年 | 4170篇 |
1989年 | 3947篇 |
1988年 | 4220篇 |
1987年 | 3839篇 |
1986年 | 3743篇 |
1985年 | 5395篇 |
1984年 | 5423篇 |
1983年 | 4368篇 |
1982年 | 4731篇 |
1981年 | 4764篇 |
1980年 | 4482篇 |
1979年 | 4620篇 |
1978年 | 4612篇 |
1977年 | 4590篇 |
1976年 | 4560篇 |
1975年 | 4451篇 |
1974年 | 4317篇 |
1973年 | 4486篇 |
1972年 | 2532篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
81.
Structural Chemistry - It is obvious and well known that the hydrogen bond plays a crucial role in numerous physical, chemical and biochemical processes. However, the significance of other... 相似文献
82.
Tyrosine nitration of human ERK1 introduces an intra-hydrogen bond by molecular dynamics simulations
Xu Wu Zhang Yuanya Achi Oliver Y. Knierim Kathleen D. Hanks Justin G. Wang Yingchun 《Structural chemistry》2019,30(4):1459-1470
Structural Chemistry - ERK1 is an important kinase in Ras–Raf–MEK signaling. We have recently demonstrated by mass spectrometry that Tyr210 of ERK1 can be nitrated, and the nitration... 相似文献
83.
J. Chevallier A. Duarte E. Löcherbach G. Ost 《Stochastic Processes and their Applications》2019,129(1):1-27
We consider spatially extended systems of interacting nonlinear Hawkes processes modeling large systems of neurons placed in and study the associated mean field limits. As the total number of neurons tends to infinity, we prove that the evolution of a typical neuron, attached to a given spatial position, can be described by a nonlinear limit differential equation driven by a Poisson random measure. The limit process is described by a neural field equation. As a consequence, we provide a rigorous derivation of the neural field equation based on a thorough mean field analysis. 相似文献
84.
85.
Yining Zhao Zhangyao Xu Tianming Wang Yuanyuan Li Li Yang Shaoyong Liu Rong Shi Yueming Ma 《Biomedical chromatography : BMC》2019,33(7)
Tanreqing capsule (TRQC) is a formulation frequently used in traditional Chinese medicine to treat pyrexia, cough, expectoration and pharyngalgia. Since the pharmacological action of traditional Chinese medicines is closely related to their complex and diverse constituents, understanding the exact composition of TRQC is important to elucidate its clinical effectiveness and mechanism of action as well as to establish quality control methods and resolve safety issues. Herein, we employed high‐performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry for the simultaneous quantitation of 23 bioactive compounds in five batches of TRQC; the analytes could be categorized into five types: organic acids (seven compounds), flavonoids (10 compounds), iridoids (two compounds), phenylethanoid glycosides (two compounds) and bile acids (two compounds). The calibration curves for all analytes showed good linearity (r > 0.9953), and the inter‐ and intra‐day precisions did not exceed 4.94 and 4.97%, respectively. The recoveries varied from 90.47% to 109.80%; the corresponding relative standard deviations (RSDs) did not exceed 4.94%; and the repeatability (RSD < 4.72%) and stability (RSD < 4.88%) were also within acceptable limits. Thus, this study can be viewed as a fundamental reference for setting comprehensive TRQC quality standards. 相似文献
86.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
87.
Amber M. Kelley Eni Minerali Jennifer E. Wilent Nicholas J. Chambers Kyla J. Stingley G. Tyler Wilson Kimberly S. Petersen 《Tetrahedron letters》2019,60(18):1262-1264
A straightforward method for the asymmetric preparation of novel lactone and lactam spirocycles is described. An initial desymmetrization via a chiral Brønsted acid yields enantioenriched lactones which readily undergo a second cyclization to give the desired spirocycle. 相似文献
88.
Yong-Li Li Qiang Zhang Jian-Jun Wu Li-Jun Xue Li-Ming Chen Jun-Mian Tian Zhuo-Ni Xu Ying Chen Xian-Wen Yang Xiao-Jiang Hao Jie Li 《Tetrahedron letters》2019,60(10):751-753
From Abies nukiangensis, two novel 13,14-seco-abietane diterpenes, nukiangendines A (1) and B (2) were isolated. Their relative structures were determined by extensive NMR and HRMS spectroscopic analysis. The absolute configuration of 1 was established by ECD calculations. Compound 1 showed significant anti-hepatitis C virus (HCV) effects. 相似文献
89.
Shevchenko V. V. Gumenna M. A. Bliznyuk V. N. Klimenko N. S. Stryutsky A. V. Wang J. Binek C. 《Theoretical and Experimental Chemistry》2019,55(2):125-131
Theoretical and Experimental Chemistry - A method was developed for the synthesis of ion-coordinated polysilsesquioxanes (OSS-M) by reaction of amphiphilic carboxyl-containing oligosilsesquioxanes... 相似文献
90.
Antonio Fernandez Emily J. Thompson Jeffrey W. Pollard Takanori Kitamura Marc Vendrell 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):17050-17054
We report the novel chemical design of fluorescent activatable chemokines as highly specific functional probes for imaging subpopulations of immune cells in live tumours. Activatable chemokines behave as AND‐gates since they emit only after receptor binding and intracellular activation, showing enhanced selectivity over existing agents. We have applied this strategy to produce mCCL2‐MAF as the first probe for in vivo detection of metastasis‐associated macrophages in a preclinical model of lung metastasis. This strategy will accelerate the preparation of new chemokine‐based probes for imaging immune cell function in tumours. 相似文献