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   164639篇
  免费   4419篇
  国内免费   2490篇
化学   92881篇
晶体学   2568篇
力学   7099篇
综合类   106篇
数学   15365篇
物理学   53529篇
  2022年   1419篇
  2021年   1775篇
  2020年   1922篇
  2019年   1988篇
  2018年   2305篇
  2017年   2286篇
  2016年   3430篇
  2015年   2436篇
  2014年   3377篇
  2013年   7327篇
  2012年   6430篇
  2011年   7416篇
  2010年   5221篇
  2009年   5179篇
  2008年   6780篇
  2007年   6496篇
  2006年   6281篇
  2005年   5769篇
  2004年   5031篇
  2003年   4609篇
  2002年   4490篇
  2001年   5920篇
  2000年   4322篇
  1999年   3492篇
  1998年   2453篇
  1997年   2543篇
  1996年   2385篇
  1995年   2189篇
  1994年   2134篇
  1993年   1918篇
  1992年   2366篇
  1991年   2429篇
  1990年   2291篇
  1989年   2209篇
  1988年   2149篇
  1987年   2138篇
  1986年   1967篇
  1985年   2428篇
  1984年   2420篇
  1983年   1938篇
  1982年   1938篇
  1981年   1768篇
  1980年   1747篇
  1979年   2029篇
  1978年   2100篇
  1977年   2049篇
  1976年   1975篇
  1975年   1859篇
  1974年   1842篇
  1973年   1875篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
In this paper we study a stochastic differential equation with multivalued maximally monotone drift operator. Under certain assumptions on the growth of the multivalued operator we prove a theorem on the existence and uniqueness of the solution of such an equation.Translated fromTeoriya Sluchainykh Protsessov, Vol. 15, pp. 54–59, 1987.  相似文献   
72.
Summary Wet-chemical cleaning procedures of Si(100) wafers are surface analytically characterized and compared. Hydrophobic surfaces show considerably less native oxides in comparison to hydrophilic surfaces.The growth of the oxide is determined as a function of exposure to air by means of XPS measurements. The chemically shifted Si2p XPS signal is utilized for the quantification of the growth kinetics.One hour after cleaning no chemically shifted Si2p XPS peak is discernible on the hydrophobic surfaces. Assuming homogeneous oxide growth, the detection limit of native oxides is estimated to be below 0.05 nm using an emission angle of 18° with respect to the wafer surface. The calculation of the oxide thickness from the chemically shifted and nonchemically shifted Si2p XPS peak intensities is carried out according to Finster and Schulze [1]. For more than a day after cleaning no surface oxides can be identified on the hydrophobic surfaces. The oxide growth kinetics is logarithmic. The very slow oxidation rate cannot be attributed to fluorine residues since no fluorine is seen by XPS. We explain the slow oxidation rate by a homogeneous hydrogen saturated Si(100) wafer surface.
Oberflächenanalytische Charakterisierung oxidfreier Si(100)-Waferoberflächen
  相似文献   
73.
74.
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 41, No. 8, pp. 1137–1141, August, 1989.  相似文献   
75.
This paper presents the development and laboratory evaluation of a PM10/2.5/1.0 trichotomous sampling inlet that consists of two main parts: a previously designed PM10 size‐selective inlet part and a PM2.5/1.0 two‐stage virtual impactor, which was newly fabricated and attached serially to the PM10 size selective inlet part. Particles are collected in three locations through the trichotomous sampling inlet to provide for not only particle concentration measurements of PM10, PM2.5 and PM1.0, but also those of PM2.5–10 and PM1.0–2.5.  相似文献   
76.
77.
78.
Several illusions of vision are considered on the basis of a neurophysiological holographic model of visual perception at the level of the eye’s and the retina. It is suggested that the eye’s optical system forms a spatial spectrum of the observed object rather than its image on the retina. The spectrum is encoded by active anisotropic quasi-crystalline structures of rod rhodopsins and cone iodopsins, and a complex Fourier hologram of the observed object consisting of two quadrature components is recorded. The holographic hypothesis is confirmed by the results obtained by digital simulation.  相似文献   
79.
80.
Bismuth, antimony and its alloys are the typical representatives of a class of semimetals, which electric conductance is lower in 102-103 times, than of usual well conducting an electrical current metals. The alloys bismuth with antimony have semi-conductor properties in wide area of compositions at temperatures below 77 °K. The semimetals are rather perspective materials from the point of view of their probable application in various devices [1,2,3].In present time the semimetal alloys BiSb have wide application in thermoelectric generators and refrigerators. In work [3] the opportunity of use of semimetals BiSb with percentage content of Bi and Sb from 8 % up to 25 % was shown as high-sensitivity and of small inertion indicators of the mm range radiation where thermoelectric effect is used. The principle of action of such indicators is based on occurrence of temperature gradient in a semimetal crystal BiSb that has two contacts of the various area with flowing electrical current. Basic element of such device is the dot contact metal - semimetal. One of the main characteristics is volt-watt sensitivity of metal-semimetal BiSb contact which calculating is shown in present work.  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