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   268654篇
  免费   2435篇
  国内免费   643篇
化学   142892篇
晶体学   4166篇
力学   11967篇
综合类   10篇
数学   29605篇
物理学   83092篇
  2019年   2308篇
  2018年   3141篇
  2017年   3124篇
  2016年   4525篇
  2015年   2686篇
  2014年   4310篇
  2013年   10749篇
  2012年   8110篇
  2011年   9961篇
  2010年   7133篇
  2009年   6921篇
  2008年   9370篇
  2007年   9564篇
  2006年   8948篇
  2005年   8133篇
  2004年   7467篇
  2003年   6784篇
  2002年   6707篇
  2001年   7359篇
  2000年   5701篇
  1999年   4391篇
  1998年   3874篇
  1997年   3858篇
  1996年   3603篇
  1995年   3348篇
  1994年   3514篇
  1993年   3209篇
  1992年   3681篇
  1991年   3683篇
  1990年   3607篇
  1989年   3468篇
  1988年   3576篇
  1987年   3471篇
  1986年   3292篇
  1985年   4377篇
  1984年   4641篇
  1983年   3880篇
  1982年   4014篇
  1981年   3937篇
  1980年   3918篇
  1979年   3883篇
  1978年   4197篇
  1977年   4111篇
  1976年   4179篇
  1975年   3855篇
  1974年   3899篇
  1973年   4054篇
  1972年   2858篇
  1971年   2381篇
  1970年   2179篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
The lidar equation for the vibrational backscattering of neodymium laser radiation and its harmonics by hydrogen molecules is solved numerically. Inclined paths in the atmosphere are investigated with the aim of selecting the transmitter wavelength for detecting the lowest concentrations of hydrogen. Zh. Tekh. Fiz. 68, 20–22 (January 1998)  相似文献   
122.
The electrostatic problem for a thin, unclosed spherical shell and a torus is reduced to paired summation equations in the Legendre polynomials by means of formulas relating the spherical and toroidal harmonic functions. The paired equations are transformed to a Fredholm integral equation of the second kind. Formulas are obtained for computing the charges of the conductors in the form of a series in a small parameter. The capacitance is computed for certain geometrical parameters of the conductors. Zh. Tekh. Fiz. 68, 1–6 (July 1998)  相似文献   
123.
The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in 207Pb81+. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics from an ion beam at relativistic velocities. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
124.
The dependence of distribution functions of quarks, antiquarks, diquarks and their fragmentation into hadrons on the transverse momentumk t is discussed in the frame of the quark-gluon string model. We then discuss the division ofk t between 2n-quark-antiquark chains, orn-pomeron showers. Hadron and hadron-nuclear processesp?p,p?A,K +?p,K +?A are analysed. A strong dependence of the observed values on the numbern is derived by this method, which is of special importance for the analysis of hadron-nucleus collisions. Our method is compared with the regulark t division method.  相似文献   
125.
The effect of clay on the radiolysis of malonic acid solutions was studied. The results showed an enhanced of decarboxylation rather than condensation reactions.  相似文献   
126.
Multidimensional two-phase Stefan (k=1) and nonstationary filtration Florin (k=0) problems for second order parabolic equations in the case when the free boundary is a graph of a functionx n k (xt),x′∈ n?1 ,n≥2,t∈(0,T) are studied. A unique solvability theorem in weighted Hölder spaces of functions with time power weight is proved, coercive estimates for solutions are obtained. Bibliography: 30 titles.  相似文献   
127.
128.
129.
We report on the first observation and studies of a weak delocalizing logarithmic temperature dependence of the conductivity, which causes the conductivity of the 2D metal to increase as T decreases down to 16 mK. The prefactor of the logarithmic dependence is found to decrease gradually with density, to vanish at a critical density n c , 2∼2×1012 cm−2, and then to have the opposite sign at n>n c ,2. The second critical density sets the upper limit on the existence region of the 2D metal, whereas the conductivity at the critical point, G c ,2∼120e 2/h, sets an upper (low-temperature) limit on its conductivity. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 6, 497–501 (25 September 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.  相似文献   
130.
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