全文获取类型
收费全文 | 34439篇 |
免费 | 5259篇 |
国内免费 | 3606篇 |
专业分类
化学 | 23790篇 |
晶体学 | 444篇 |
力学 | 2258篇 |
综合类 | 369篇 |
数学 | 3939篇 |
物理学 | 12504篇 |
出版年
2024年 | 31篇 |
2023年 | 669篇 |
2022年 | 681篇 |
2021年 | 1010篇 |
2020年 | 1381篇 |
2019年 | 1363篇 |
2018年 | 1131篇 |
2017年 | 1069篇 |
2016年 | 1580篇 |
2015年 | 1555篇 |
2014年 | 1916篇 |
2013年 | 2558篇 |
2012年 | 3206篇 |
2011年 | 3265篇 |
2010年 | 2120篇 |
2009年 | 2100篇 |
2008年 | 2177篇 |
2007年 | 2006篇 |
2006年 | 1777篇 |
2005年 | 1487篇 |
2004年 | 1150篇 |
2003年 | 915篇 |
2002年 | 817篇 |
2001年 | 637篇 |
2000年 | 582篇 |
1999年 | 676篇 |
1998年 | 588篇 |
1997年 | 585篇 |
1996年 | 661篇 |
1995年 | 545篇 |
1994年 | 476篇 |
1993年 | 403篇 |
1992年 | 373篇 |
1991年 | 329篇 |
1990年 | 258篇 |
1989年 | 210篇 |
1988年 | 159篇 |
1987年 | 137篇 |
1986年 | 128篇 |
1985年 | 125篇 |
1984年 | 89篇 |
1983年 | 65篇 |
1982年 | 43篇 |
1981年 | 36篇 |
1980年 | 21篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1975年 | 28篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Redox Communication within Multinuclear Iron–Sulfur Complexes Related to Electronic Interplay in the Active Site of [FeFe]Hydrogenase 下载免费PDF全文
Kai‐Ti Chu Dr. Yu‐Chiao Liu Yi‐Lan Huang Dr. Gene‐Hsiang Lee Dr. Mei‐Chun Tseng Prof. Ming‐Hsi Chiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6852-6861
The one‐electron oxidations of a Fe2 complex lead to the formation of a persistent metal‐stabilized thiyl radical Fe2 species, mixed‐valent Fe4, and Fe8 complexes. The unpaired spin in the Fe2 radical species delocalizes over the Fe2 and the aromatic dithiolate, mostly on the terminal sulfur. The subsequent dimerization of the singly oxidized Fe2 to the Fe4 retains the partial thiyl radical character. For an analogue with less steric hindrance, the π–π stacking interaction between the dithiolato aromatic rings induces generation of the Fe8, in which process electronic structures of the species are modulated through reducing the thiyl radical to the thiolate. Electronic reorganization repeats when the Fe8 is converted to Fe4. Electronic interplay in the complexes decreases the energy gap of frontier MOs and buffers electronic impacts upon redox events. Easier accessible redox potentials and increased stability of the species are facilitated. The results demonstrate that electronic versatility of the benzenedithiolate exerts pronounced influences on electronic and coordination structure of the metal complexes. 相似文献
93.
采用最大网络流量模型和Ford-Fulkerson算法思想编写的Matlab程序在计算c轴织构122型铁基超导体临界传输电流密度时表现出色。变动部分参数后,该模型和计算方法也同样适用于其它铁基超导体。这里计算了c轴织构的1111型铁基超导体在不同温度和磁场下的临界电流密度Jc,并研究了材料的相对密度对Jc的影响。 相似文献
94.
95.
96.
97.
Palladium‐Catalyzed N‐Arylation of Iminodibenzyls and Iminostilbenes with Aryl‐ and Heteroaryl Halides 下载免费PDF全文
Dr. Wenliang Huang Prof. Stephen L. Buchwald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14186-14189
Compounds containing the iminodibenzyl and iminostilbene ring systems are prevalent in medicinal targets and functional materials. Herein, we report palladium‐catalyzed conditions for the N‐arylation of these ring systems. This protocol could be applied to a variety of (hetero)aryl chloride and bromide substrates, including ones, which are sterically hindered or those containing a variety of functional groups. Use of the fourth‐generation palladacycle precatalyst gave good to excellent yields by using low palladium‐catalyst loadings (0.1 to 1 mol %). 相似文献
98.
99.
Zihao Yang Junzhi Cui Yufeng Nie Zhiqiang Huang Meizhen Xiang 《Acta Mechanica Sinica》2015,31(5):762-776
In this paper,a statistical second-order twoscale(SSOTS) method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,the random distribution characteristics of particles,including the shape,size,orientation,spatial location,and volume fractions,are all considered.Firstly,the repre.sentation for the microscopic configuration of the statistically inhomogeneous materials is described.Secondly,the SSOTS formulation for the dynamic thermo-mechanical coupled problem is proposed in a constructive way,including the cell problems,effective thermal and mechanical parameters,homogenized problems,and the SSOTS formulas of the temperatures,displacements,heat flux densities and stresses.And then the algorithm procedure corresponding to the SSOTS method is brought forward.The numerical results obtained by using the SSOTS algorithm are compared with those by classical methods.In addition,the thermo-mechanical coupling effect is studied by comparing the results of coupled case with those of uncoupled case.It demonstrates that the coupling effect on the temperatures,heat flux densities,displacements,and stresses is very distinct.The results show that the SSOTS method is valid to predict the dynamic thermo-mechanical coupled performances of statistically inhomogeneous materials. 相似文献
100.