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   31222篇
  免费   1888篇
  国内免费   3522篇
化学   10881篇
晶体学   105篇
力学   1210篇
综合类   143篇
数学   2363篇
物理学   6080篇
综合类   15850篇
  2024年   39篇
  2023年   197篇
  2022年   241篇
  2021年   319篇
  2020年   374篇
  2019年   325篇
  2018年   261篇
  2017年   346篇
  2016年   548篇
  2015年   560篇
  2014年   617篇
  2013年   856篇
  2012年   985篇
  2011年   2724篇
  2010年   1525篇
  2009年   1696篇
  2008年   1058篇
  2007年   941篇
  2006年   913篇
  2005年   1264篇
  2004年   3328篇
  2003年   2384篇
  2002年   2156篇
  2001年   1602篇
  2000年   911篇
  1999年   1086篇
  1998年   1126篇
  1997年   1124篇
  1996年   669篇
  1995年   527篇
  1994年   698篇
  1993年   1162篇
  1992年   978篇
  1991年   814篇
  1990年   782篇
  1989年   589篇
  1988年   307篇
  1987年   220篇
  1986年   148篇
  1985年   74篇
  1984年   49篇
  1983年   25篇
  1982年   19篇
  1981年   12篇
  1980年   8篇
  1977年   3篇
  1970年   3篇
  1957年   3篇
  1938年   3篇
  1893年   3篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
Du  Zhong  Xu  Tao  Ren  Shuai 《Nonlinear dynamics》2021,104(1):683-689
Nonlinear Dynamics - In this paper, we investigate the interactions of the vector breathers for the coupled Hirota system with $$4\times 4$$ Lax pair. Firstly, we give the first-order breather...  相似文献   
3.
加强成人高等教育质量监控研究,有利于实现成人高等教育教学的目标管理、精细化管理,也有利于实现成人高等教育的制度化、规范化和科学化.目前学界对成人高等教育质量监控的研究,虽然取得了不少研究成果,但还存在许多不足之处,需要进一步探讨成人高等教育质量的价值取向,全面把握当前成人高等教育质量监控工作的基本现状,从教学信息、教学督导、教学管理等方面系统构建起成人高等教育质量监控体系.  相似文献   
4.
Redox-based post-translational modification of protein thiols has become an attractive strategy in cellular homeostasis and cell signaling.Due to the reductive end of the redox buffer network,the vicinal dithiol-containing proteins(VDPs)maintains an appropriate oxidation-reduction state of proteins through the reversible transformation from vicinal dithiols to disulfide,which is responsible for a variety of  相似文献   
5.
6.
We conducted measurements of black carbon(BC) aerosol in Jiaxing,China during autumn from September 26 to November 30,2013.We investigated temporal and diurnal variations of BC,and its correlations with meteorological parameters and other major pollutants.Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m3,with an average of 5.1 μg/m3.The diurnai variation of BC exhibited a bimodal distribution,with peaks at 07:00 and 18:00.The morning peak was larger than the evening peak.The mass percentages of BC in PM2.5 and PM10 were 7.1%and 4.8%,respectively.The absorption coefficient of BC was calculated to be 44.4 Mm-1,which accounted for 11.1%of the total aerosol extinction.BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m3 during the measurement period.Correlation analysis indicated that the main sources of BC were motor vehicle exhaust,and domestic and industrial combustion.  相似文献   
7.
8.
9.
The contribution of rheological properties and viscoelasticity of the interfacial adsorbed layer to the emulsification mechanism of enzymatic modified sugar beet pectin (SBP) was studied. The component content of each enzymatic modified pectin was lower than that of untreated SBP. Protein and ferulic acid decreased from 5.52% and 1.08% to 0.54% and 0.13%, respectively, resulting in a decrease in thermal stability, apparent viscosity, and molecular weight (Mw). The dynamic interfacial rheological properties showed that the interfacial pressure and modulus (E) decreased significantly with the decrease of functional groups (especially proteins), which also led to the bimodal distribution of particle size. These results indicated that the superior emulsification property of SBP is mainly determined by proteins, followed by ferulic acid, and the existence of other functional groups also promotes the emulsification property of SBP.  相似文献   
10.
The random copolymerization of norbornene-functionalized macromonomers was explored as a method of synthesizing mixed-graft block copolymers (mGBCPs). The copolymerization kinetics of a model system of polystyrene (PS) and poly(lactic acid) (PLA) macromonomers was first analyzed, revealing a gradient composition of side chains along the mGBCP backbone. The phase separation behavior of mGBCPs with PS and PLA side chains of various backbone lengths and side chain molar ratios was investigated, and increasing the backbone length was found to stabilize the phase-separated nanostructures. The graft architecture was also demonstrated to improve the processability of the mGBCP, compared to a linear counterpart. Investigations of mGBCPs comprised of polydimethylsiloxane and poly(ethylene oxide) side chains exemplified the diverse self-assembled morphologies, including a Frank-Kasper A15 phase, that can be obtained with mGBCPs synthesized by random copolymerization of macromonomers. Lastly, a ternary mGBCP was synthesized by the copolymerization of three macromonomers.  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