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   17984篇
  免费   3255篇
  国内免费   2096篇
化学   12912篇
晶体学   185篇
力学   1044篇
综合类   103篇
数学   1817篇
物理学   7274篇
  2024年   78篇
  2023年   412篇
  2022年   660篇
  2021年   723篇
  2020年   753篇
  2019年   748篇
  2018年   671篇
  2017年   599篇
  2016年   905篇
  2015年   880篇
  2014年   1041篇
  2013年   1312篇
  2012年   1625篇
  2011年   1518篇
  2010年   1060篇
  2009年   981篇
  2008年   1089篇
  2007年   1024篇
  2006年   939篇
  2005年   850篇
  2004年   610篇
  2003年   516篇
  2002年   508篇
  2001年   397篇
  2000年   358篇
  1999年   425篇
  1998年   346篇
  1997年   337篇
  1996年   318篇
  1995年   276篇
  1994年   225篇
  1993年   198篇
  1992年   156篇
  1991年   136篇
  1990年   157篇
  1989年   111篇
  1988年   76篇
  1987年   54篇
  1986年   59篇
  1985年   59篇
  1984年   30篇
  1983年   30篇
  1982年   30篇
  1981年   19篇
  1980年   10篇
  1979年   3篇
  1977年   3篇
  1942年   2篇
  1930年   2篇
  1916年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A tripeptide (β-AspFF) gelator was designed and synthesised using solid-phase peptide synthesis. The as-prepared gelator formed a stable and clear multi-responsive gel in toluene solution. Encapsulating the quantum dots with β-AspFF effectively increased stability and antioxidisation ability which are beneficial for optical identification.  相似文献   
992.
This paper presents a new parameter estimation method for Itô diffusions such that the resulting model predicts the equilibrium statistics as well as the sensitivities of the underlying system to external disturbances. Our formulation does not require the knowledge of the underlying system, however, we assume that the linear response statistics can be computed via the fluctuation–dissipation theory. The main idea is to fit the model to a finite set of “essential” statistics that is sufficient to approximate the linear response operators. In a series of test problems, we will show the consistency of the proposed method in the sense that if we apply it to estimate the parameters of the underlying model, then we must obtain the true parameters.  相似文献   
993.
994.
995.
Three series of cholesteryl-containing supramolecular hydrogen-bonded (H-bonded) liquid crystal (LC) complexes with different number of fluoro-substituent were synthesised and characterised. Cholesteryl isonicotinate as proton acceptor and 4-n-alkoxybenzoic acids with or without fluoro-substituent as proton donor had been mixed in tetrahydrofuran to obtain H-bonded LC complexes. The effect of lateral substitution and the length of terminal chain in the H-bonded precursors on the formation of the supramolecular complexes had been examined. It was found that the introduction of fluoro substituent on the induced mesogens could widen the molecular width and thus reduce the molecular aspect ratio of the complexes, therefore it could lead to compress the formation of the LCs. However, the fluoro substituent played a positive role in enhancing the intermolecular interactions and stabilising the H-bond structure of the complexes. The influence of terminal length on the mesogenic behaviours is also discussed. On increasing the spacer length, the clear point and the thermal range of induced mesophase-like cholesteric phase decreased, and an induced chiral smectic phase began to appear in some complexes with long terminal tails.  相似文献   
996.
997.
The knowledge of whether one enzyme can interact with a small molecule is essential for understanding the molecular and cellular functions of organisms. In this paper, we introduce a classifier to predict the small molecule– enzyme interaction, i.e., whether they can interact with each other. Small molecules are represented by their chemical functional groups, and enzymes are represented by their biochemical and physicochemical properties, resulting in a total of 160 features. These features are input into the AdaBoost classifier, which is known to have good generalization ability to predict interaction. As a result, the overall prediction accuracy, tested by tenfold cross-validation and independent sets, is 81.76% and 83.35%, respectively, suggesting that this strategy is effective. In this research, we typically choose interactions between small molecules and enzymes involved in metabolism to ultimately improve further understanding of metabolic pathways. An online predictor developed by this research is available at . Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
998.
Previously the perihelion advance in binary system was computed approximately. We will present an exact analytical solution to nonlinear differential equation of perihelion advance by method of Jacobian elliptic function and the advanced angle between successive perihelions. Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars from Ministry of Education, China (Grant No. [2004]527) and the Natural Science Foundation of Hunan Province, China (Grant No. 06JJ2026)  相似文献   
999.
1000.
The effect of magnetic relaxation on flux jump is studied in high temperature superconducting slab. The magnetothermal diffusion equations based on the Kim model are presented in this paper to estimate the effect of magnetic relaxation on flux jump inside the slab in the flux dynamics process. Numerical results obtained show that the flux-jump phenomenon could be suppressed by the magnetic relaxation and the dependence of the number of flux jumps on the relaxation time are obvious.  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