首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   19125篇
  免费   2759篇
  国内免费   1866篇
化学   13581篇
晶体学   220篇
力学   933篇
综合类   97篇
数学   2480篇
物理学   6439篇
  2023年   306篇
  2022年   388篇
  2021年   578篇
  2020年   759篇
  2019年   785篇
  2018年   698篇
  2017年   601篇
  2016年   933篇
  2015年   851篇
  2014年   1041篇
  2013年   1511篇
  2012年   1662篇
  2011年   1671篇
  2010年   1104篇
  2009年   1127篇
  2008年   1277篇
  2007年   1145篇
  2006年   1005篇
  2005年   883篇
  2004年   743篇
  2003年   610篇
  2002年   601篇
  2001年   447篇
  2000年   315篇
  1999年   315篇
  1998年   253篇
  1997年   240篇
  1996年   241篇
  1995年   199篇
  1994年   166篇
  1993年   150篇
  1992年   139篇
  1991年   137篇
  1990年   99篇
  1989年   75篇
  1988年   65篇
  1987年   64篇
  1986年   69篇
  1985年   66篇
  1984年   46篇
  1983年   41篇
  1982年   41篇
  1981年   44篇
  1980年   29篇
  1979年   39篇
  1978年   27篇
  1977年   21篇
  1976年   27篇
  1975年   26篇
  1974年   20篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
International Journal of Theoretical Physics - In this paper, we investigate Einstein-Podolsky-Rosen steering, Bell non-locality, first-order coherence and concurrence in the spin- $\frac {1}{2}$...  相似文献   
2.
Jiang  H.  Lei  Z.  Bai  R.  Liu  J.  Guo  Z.  Dong  H.  Feng  W. 《Experimental Mechanics》2021,61(5):867-883
Experimental Mechanics - Ratcheting is an important mechanical behavior of metals and alloys, which is caused by the repeated accumulations of tensile and compressive strain in circle load....  相似文献   
3.
Song  Zi-Long  Zhu  Yun  Liu  Jing-Rui  Guo  Shu-Ke  Gu  Yu-Cheng  Han  Xinya  Dong  Hong-Qiang  Sun  Qi  Zhang  Wei-Hua  Zhang  Ming-Zhi 《Molecular diversity》2021,25(1):205-221
Molecular Diversity - Based on the strategy of diversity-oriented synthesis and the structures of natural product pimprinine and streptochlorin, two series of novel pimprinine derivatives...  相似文献   
4.
Nguyen  Duc H.  Lowenberg  Mark H.  Neild  Simon A. 《Nonlinear dynamics》2022,108(2):1179-1196
Nonlinear Dynamics - Based on bifurcation theory, nonlinear frequency response analysis is a recent development in the field of flight dynamics studies. Here, we consider how this method can be...  相似文献   
5.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  相似文献   
6.
7.
8.
A capillary electrophoresis-acid barrage stacking online enrichment method has been established to detect the four isoflavones which are Daidzein, Genistein, Formononetin, and Biochanin A. The proposed method was optimized using a single factor alternative method, and the optimal conditions obtained from the optimization were: the BGE was 25 mM borax and 2 mM β-cyclodextrin, the applied separation voltage was 20 kV, and the detection wavelength was 260 nm. The time ratio of the injection of sample and the injection of acid was 150 s:20 s, and the acid used was 250 mM acetic acid. The sample solvent used was 60% v/v acetonitrile. The established method had the enrichment factor of these four isoflavones at 24.5, 32.0, 29.2, and 33.7, respectively, LOD and LOQ are as low as nanograms per milliliter. Finally, the CE-acid barrage stacking method was successfully applied to the determination of four isoflavones in rat plasma and red clover extract, verifying the applicability and feasibility of the method.  相似文献   
9.
10.
Pd-based catalysts are the most widely used for CO oxidation because of their outstanding catalytic activity and thermal stability. However, fundamental understanding of the detailed catalytic processes occurring on Pd-based catalysts under realistic conditions is still lacking. In this study, we investigated CO oxidation on metallic Pd clusters supported on Al2O3 and SiO2. High-angle annular dark-field scanning transmission electron microscopy revealed the formation of similar-sized Pd clusters on Al2O3 and SiO2. In contrast, CO chemisorption analysis indicated a gradual change in the dispersion of Pd (from 0.79 to 0.2) on Pd/Al2O3 and a marginal change in the dispersion (from 0.4 to 0.24) on Pd/SiO2 as the Pd loading increased from 0.27 to 5.5 wt %; these changes were attributed to differences in the metal-support interactions. Diffuse reflectance infrared Fourier-transform spectroscopy revealed that fewer a-top CO species were present in Pd supported on Al2O3 than those in Pd supported on SiO2, which is related to the morphological differences in the metallic Pd clusters on these two supports. Despite the different dispersion profiles and surface characteristics of Pd, O2 titration demonstrated that linearly bound CO (with an infrared signal at 2090 cm−1) reacted first with oxygen in the case of CO-saturated Pd on Al2O3 and SiO2, which suggests that a-top CO on the terrace site plays an important role in CO oxidation. The experimental observations were corroborated by periodic density functional calculations, which confirmed that CO oxidation on the (111) terrace sites is most plausible, both kinetically and thermodynamically, compared to that on the edge or corner sites. This study will deepen the fundamental understanding of the effect of Pd clusters on CO oxidation under reaction conditions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号