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   272188篇
  免费   1932篇
  国内免费   528篇
化学   123020篇
晶体学   4378篇
力学   14105篇
综合类   3篇
数学   44791篇
物理学   88351篇
  2020年   1441篇
  2019年   1602篇
  2018年   10779篇
  2017年   11678篇
  2016年   7344篇
  2015年   2868篇
  2014年   3414篇
  2013年   8210篇
  2012年   10198篇
  2011年   19389篇
  2010年   12239篇
  2009年   12244篇
  2008年   17191篇
  2007年   20561篇
  2006年   6523篇
  2005年   12270篇
  2004年   8604篇
  2003年   8058篇
  2002年   5949篇
  2001年   5456篇
  2000年   4243篇
  1999年   3048篇
  1998年   2568篇
  1997年   2442篇
  1996年   2450篇
  1995年   2260篇
  1994年   2208篇
  1993年   2116篇
  1992年   2422篇
  1991年   2355篇
  1990年   2310篇
  1989年   2243篇
  1988年   2256篇
  1987年   2252篇
  1986年   2128篇
  1985年   2768篇
  1984年   2843篇
  1983年   2533篇
  1982年   2637篇
  1981年   2432篇
  1980年   2421篇
  1979年   2571篇
  1978年   2629篇
  1977年   2448篇
  1976年   2545篇
  1975年   2449篇
  1974年   2417篇
  1973年   2626篇
  1972年   1692篇
  1971年   1381篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
103.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
104.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
105.
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual polytope.  相似文献   
106.
107.
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays.  相似文献   
108.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution.  相似文献   
109.
110.
ONAPAIROFNONISOMETRICISOSPECTRALDOMAINSWITHFRACTALBOUNDARIESANDTHEWEYLBERRYCONJECTURESLEEMAN,B.D.CHENHUAManuscriptrec...  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