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   117211篇
  免费   19149篇
  国内免费   12310篇
化学   79352篇
晶体学   1474篇
力学   7744篇
综合类   747篇
数学   13422篇
物理学   45931篇
  2024年   387篇
  2023年   2238篇
  2022年   3937篇
  2021年   4266篇
  2020年   4545篇
  2019年   4502篇
  2018年   3907篇
  2017年   3687篇
  2016年   5681篇
  2015年   5497篇
  2014年   6639篇
  2013年   8589篇
  2012年   10348篇
  2011年   10726篇
  2010年   7191篇
  2009年   6975篇
  2008年   7422篇
  2007年   6784篇
  2006年   6299篇
  2005年   5224篇
  2004年   3995篇
  2003年   3187篇
  2002年   3045篇
  2001年   2544篇
  2000年   2134篇
  1999年   2359篇
  1998年   2024篇
  1997年   1836篇
  1996年   1998篇
  1995年   1588篇
  1994年   1527篇
  1993年   1244篇
  1992年   1113篇
  1991年   1023篇
  1990年   829篇
  1989年   598篇
  1988年   482篇
  1987年   399篇
  1986年   387篇
  1985年   333篇
  1984年   247篇
  1983年   158篇
  1982年   143篇
  1981年   110篇
  1980年   79篇
  1979年   47篇
  1978年   34篇
  1976年   36篇
  1975年   34篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
李建林  魏广生 《数学学报》2002,45(5):847-850
设函数f(w)为凸区域D内的单叶解析函数,对于2≤n≤8和所有w∈D,本文得到估计式|f(n)(w)/f'(w)|的精确上界.这个结果推广了一些已知的结论.  相似文献   
52.
成功地在六路高功率Nd玻璃激光装置上建立了2660紫外激光探针和适合紫外波段的Normaski干涉仪,首次将可见波长的连续激光应用于紫外干涉仪中靶成像调整和光路准直。利用该紫外光干涉仪,在铜柱状靶(φ500μm)上测量了厚等离子体中高达0.6n。的电子密度。  相似文献   
53.
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters. Received 28 July 2001  相似文献   
54.
In this paper, the dimension of the spaces of bivariate spline with degree less that 2r and smoothness order r on the Morgan-Scott triangulation is considered. The concept of the instability degree in the dimension of spaces of bivariate spline is presented. The results in the paper make us conjecture the instability degree in the dimension of spaces of bivariate spline is infinity.  相似文献   
55.
金属β-二酮化合物用于MOCVD法生长铁电氧化物薄膜   总被引:1,自引:0,他引:1  
对用于MOCVD法生长铁电氧化物薄膜的金属β-二酮化合物的制备、结构及性质进行了评述,对它们在生长铁电薄膜中的应用现状进行了介绍,并对它们的应用前景作了展望。  相似文献   
56.
We investigate the KdV like equation with higher order nonlinearity ut + a(1 +bun)unux + uxxx = 0with n ≥ 1, a, b ∈ R and α≠ 0. The bifurcations and explicit expressions of solitary wave solutions for theequation are discussed by using the bifurcation method and qualitative theory of dynamical systems. Thebifurcation diagrams, existence and number of the solitary waves are given.  相似文献   
57.
Analysis of the field distributions in a single biological cell under electromagnetic wave is given. With Debye approximation, the dielectric relaxation of each part of the cell, including the extracellular and cellular media, the cell membrane and the nuclear membrane, was taken into account. Making use of some typical parameters for a cell, the voltage across nuclear and cytoplasma membranes under electromagnetic waves are calculated up to millimeter wave frequency range. The calculated result indicates that it is unlikely to generate electroporation by present available millimeter wave sources.  相似文献   
58.
Note on Bernstein polynomials and Kantorovich polynomials   总被引:2,自引:0,他引:2  
We obtain two asymptotic representations of remainder of approximation of derivable functions by Bernstein polynomials and Kantorovich polynomials separately.  相似文献   
59.
A new type of vortices called Chern-Simons vortices is considered and the existence is established.  相似文献   
60.
The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar+ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate.  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