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   32203篇
  免费   5103篇
  国内免费   4581篇
化学   24238篇
晶体学   423篇
力学   1853篇
综合类   324篇
数学   3577篇
物理学   11472篇
  2024年   20篇
  2023年   489篇
  2022年   593篇
  2021年   868篇
  2020年   1090篇
  2019年   1100篇
  2018年   958篇
  2017年   873篇
  2016年   1495篇
  2015年   1450篇
  2014年   1788篇
  2013年   2364篇
  2012年   2852篇
  2011年   2917篇
  2010年   2107篇
  2009年   2019篇
  2008年   2404篇
  2007年   2176篇
  2006年   1990篇
  2005年   1699篇
  2004年   1427篇
  2003年   1215篇
  2002年   1255篇
  2001年   1039篇
  2000年   796篇
  1999年   719篇
  1998年   512篇
  1997年   497篇
  1996年   482篇
  1995年   466篇
  1994年   362篇
  1993年   306篇
  1992年   298篇
  1991年   240篇
  1990年   218篇
  1989年   175篇
  1988年   122篇
  1987年   110篇
  1986年   88篇
  1985年   74篇
  1984年   54篇
  1983年   41篇
  1982年   26篇
  1981年   30篇
  1980年   18篇
  1978年   13篇
  1977年   7篇
  1976年   8篇
  1973年   7篇
  1957年   6篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
1.
Zhai  Shidong  Gao  Hui  Luo  Guoqiang  Tao  Junli 《Nonlinear dynamics》2021,106(2):1133-1147
Nonlinear Dynamics - This paper introduces a multigroup COVID-19 model with immunity, in which the total population of each group is partitioned into five compartments, that is, susceptible,...  相似文献   
2.
3.
Gao  Zhigen  Guo  Jianhua  Ma  Yanyuan 《中国科学 数学(英文版)》2021,64(8):1905-1916
Science China Mathematics - Linear factor models are familiar tools used in many fields. Several pioneering literatures established foundational theoretical results of the quasi-maximum likelihood...  相似文献   
4.
5.
Hu  Duo-Duo  Gao  Qian  Dai  Jing-Cheng  Cui  Ru  Li  Yuan-Bo  Li  Yuan-Ming  Zhou  Xiao-Guo  Bian  Kang-Jie  Wu  Bing-Bing  Zhang  Kai-Fan  Wang  Xi-Sheng  Li  Yan 《中国科学:化学(英文版)》2022,65(4):753-761
Science China Chemistry - A light-induced, nickel-catalyzed three-component arylsulfonation of 1,3-enynes in the absence of photocatalyst is reported. This methodology exhibited mild conditions,...  相似文献   
6.
Chen  Xiulong  Tang  Yuefei  Gao  Shun 《Meccanica》2022,57(1):229-250
Meccanica - The multi-link press mechanism is developing in the direction of high speed and high precision. However, the non-uniform wear of joint clearance seriously affects the output motion...  相似文献   
7.
8.
Zhang  Zhen  Gao  Zhi-Tong  Fang  Bo  Zhang  Ye-Wei 《Nonlinear dynamics》2022,109(3):1259-1275
Nonlinear Dynamics - As a simplified model of structures of many kinds, the Euler Bernoulli beam has proved useful for studying vibration suppression. In order to meet engineering design...  相似文献   
9.
The drug delivery system based on nano/micromotors has become a research hot spot in recent years. However, naked micromotors may be ruptured or passivated under the complex biological environment, which will result in the leakage of drugs in advance or limited self-propulsion performance. Herein, an injectable micromotor@hydrogel drug delivery system to protect micromotors from the external environment is proposed. The micromotors were prepared through layer-by-layer assembly technology. The asymmetric decomposition of hydrogen peroxide catalyzed by the locally distributed platinum nanoparticles enabled efficient propulsion of the micromotors in low concentration of hydrogen peroxide. In order to protect micromotors, they were loaded into the Schiff base hydrogel. The micromotor@hydrogel system can be injected directly into the lesion to release micromotors in response to the environment, reducing external influence on micromotors and improving the sustained-release effect. Erythromycin (Ery) loaded into the micromotors and the micromotor@hydrogel system demonstrated excellent antibacterial effect. Micromotors released from the hydrogel underwent enhanced diffusion in the surroundings of bacteria without addition of exogenous hydrogen peroxide, which was manifested by their appearance in edge of the inhibition zone. The proposed micromotor@hydrogel drug delivery system offers a new strategy for the treatment of bacterial infections.  相似文献   
10.
Cubic-like CaTaO2N photocatalysts with high crystallinity and uniform particle size were successfully prepared by the flux-assisted nitridation method. The growth of CaTaO2N single crystals under different synthesis conditions was systematically investigated to understand the effects of the crystallinity and optical property on photocatalytic performance of CO2 reduction. Moreover, the modification of CaTaO2N single crystals with core-shell Ni−Ag bicomponent cocatalyst by two-step decoration process gave a 2.4 times higher amount of CO evolution than the deposition of sole Ag cocatalyst, because of the synergistic effects of bicomponent cocatalyst on the interfacial electron transfer and surface catalytic process. This study provides a valuable way to construct high-crystalline photocatalysts with effective bicomponent cocatalyst for visible-light-driven CO2 reduction with H2O.  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