全文获取类型
收费全文 | 68155篇 |
免费 | 3010篇 |
国内免费 | 1692篇 |
专业分类
化学 | 34532篇 |
晶体学 | 1193篇 |
力学 | 3748篇 |
综合类 | 126篇 |
数学 | 5672篇 |
物理学 | 27586篇 |
出版年
2022年 | 841篇 |
2021年 | 999篇 |
2020年 | 1020篇 |
2019年 | 965篇 |
2018年 | 1014篇 |
2017年 | 898篇 |
2016年 | 1422篇 |
2015年 | 1277篇 |
2014年 | 1681篇 |
2013年 | 3313篇 |
2012年 | 3293篇 |
2011年 | 3947篇 |
2010年 | 2766篇 |
2009年 | 2863篇 |
2008年 | 3466篇 |
2007年 | 3166篇 |
2006年 | 2980篇 |
2005年 | 2578篇 |
2004年 | 2285篇 |
2003年 | 1965篇 |
2002年 | 1858篇 |
2001年 | 3155篇 |
2000年 | 2289篇 |
1999年 | 1666篇 |
1998年 | 1177篇 |
1997年 | 1125篇 |
1996年 | 946篇 |
1995年 | 828篇 |
1994年 | 743篇 |
1993年 | 665篇 |
1992年 | 984篇 |
1991年 | 964篇 |
1990年 | 868篇 |
1989年 | 766篇 |
1988年 | 745篇 |
1987年 | 811篇 |
1986年 | 673篇 |
1985年 | 897篇 |
1984年 | 838篇 |
1983年 | 571篇 |
1982年 | 564篇 |
1981年 | 535篇 |
1980年 | 498篇 |
1979年 | 622篇 |
1978年 | 651篇 |
1977年 | 659篇 |
1976年 | 575篇 |
1975年 | 481篇 |
1974年 | 522篇 |
1973年 | 448篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
21.
22.
23.
24.
S. Q. Hou W. Wang Z. Y. Wang Z. W. Hu K. Liu 《Journal of Applied Mechanics and Technical Physics》2018,59(1):153-162
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages. 相似文献
25.
In the view of substrate availability, atomic efficiency and cost, directly using arenols as coupling partners in cross‐coupling, would be one of the most attractive goals. Up to date, many efforts have been made to activate the C—O bond of phenols with different strategies, for example, through in‐situ formed intermediates, through a catalytic reductive dearomatization‐condensation‐rearomatization sequence or catalytic deoxygenation. In this review, we summarized recent advances in cross‐couplings of arenols as the electrophiles via C—O activation. 相似文献
26.
27.
The Ramanujan Journal - Inspired by Andrews and Merca’s recent work on the number of even parts over all partitions into distinct parts, we introduce a new kind of Beck type identities, which... 相似文献
28.
Nonlinear Dynamics - Conventional tuned liquid column dampers (TLCDs) are deficient in multidirectionality. In contrast, toroidal TLCDs are designed to extend the application to multidirectional... 相似文献
29.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
30.