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   60872篇
  免费   13692篇
  国内免费   4864篇
化学   58309篇
晶体学   623篇
力学   2394篇
综合类   239篇
数学   5180篇
物理学   12683篇
  2024年   73篇
  2023年   598篇
  2022年   868篇
  2021年   1086篇
  2020年   2285篇
  2019年   3455篇
  2018年   1884篇
  2017年   1504篇
  2016年   4517篇
  2015年   4609篇
  2014年   4825篇
  2013年   5868篇
  2012年   5196篇
  2011年   4564篇
  2010年   4483篇
  2009年   4280篇
  2008年   4083篇
  2007年   3245篇
  2006年   2911篇
  2005年   2765篇
  2004年   2347篇
  2003年   2025篇
  2002年   2798篇
  2001年   1996篇
  2000年   1839篇
  1999年   1055篇
  1998年   545篇
  1997年   462篇
  1996年   496篇
  1995年   419篇
  1994年   381篇
  1993年   313篇
  1992年   286篇
  1991年   250篇
  1990年   219篇
  1989年   177篇
  1988年   155篇
  1987年   102篇
  1986年   87篇
  1985年   82篇
  1984年   56篇
  1983年   53篇
  1982年   30篇
  1981年   34篇
  1980年   17篇
  1979年   10篇
  1978年   12篇
  1976年   10篇
  1975年   10篇
  1957年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We consider a useful modification of the inexact implicit method with a variable parameter in Wang et al. J Optim Theory 111: 431–443 (2001) for generalized mixed monotone variational inequalities. One of the contributions of the proposed method in this paper is that the restrictions imposed on the variable parameter are weaker than the ones in Wang et al. J Optim Theory 111: 431–443 (2001). Another contribution is that we establish a sufficient and necessary condition for the convergence of the proposed method to a solution of the general mixed monotone variational inequality.  相似文献   
102.
103.
104.
A graph G is N2locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005  相似文献   
105.
The irreversibility field (Hirr) of Y-based superconductor is much higher than that of Bi-based superconductor. Y-based superconductor is capable of maintaining stable electrical currents in high magnetic field and electric field, so it is a better suited mate-rial for electric-current applications. Commonly, the Y-based tapes comprise a YBCO thick film deposited on a flexible substrate, typically with an intermediate buffer layer, and an overcoat of noble metal. In this process, the interm…  相似文献   
106.
In this paper, a very useful numerical technique has been developed for analyzing the transient characteristics of a planar-spiral inductor on-chip. A locally conformal technique and an alternating-direction implicit scheme are applied to the finite-difference time-domain method. A formulation for solving three dimensional Maxwell’s equations is proposed. Using the proposed method, various parameters of the planar-spiral inductors have been analyzed and an equivalent circuit, which includes frequency-independent circuit elements, has been introduced. Highly computational efficiency is implemented. Numerical results show excellent agreement with the measured data over a wide frequency range.  相似文献   
107.
The existence, multiplicity and infinite solvability of positive solutions are established for some two-point boundary value problems of one-dimensional p-Laplacian. In this paper, by multiplicity we mean the existence of m solutions, where m is an arbitrary natural number.  相似文献   
108.
In the title compound, catena‐poly[lithium‐μ3‐ethyl­ene­diphos­phon­ato], [Li(C2H7O6P2)]n, the supra­molecular monoclinic (C2/c) structure consists of one‐dimensional lithium chains [Li⋯Li = 2.7036 (8) Å] that are embedded within ethyl­ene­diphosphon­ate anions linked by strong symmetric hydrogen bonds [O⋯O = 2.473 (3) Å]. The Li atoms and the H atom in the symmetric hydrogen bond reside on twofold rotation axes and there is an inversion center at the mid‐point of the C—C bond of the ethylenediphosphonate ligand.  相似文献   
109.
Photoluminescence (PL) linewidth broadening of CdxZn1 − xSe/ZnSe triple quantum wells, grown on GaAs substrates by molecular beam epitaxy (MBE), has been investigated. Various quantum well (QW) samples have been prepared with different QW thickness and composition (Cd-composition). Measured and calculated PL linewidth are compared. Both composition and thickness fluctuations are considered for the calculation with the parameters such as the volume of exciton, nominal thickness and composition of QWs. Surface roughness measured by atomic force microscopy (AFM) is used to estimate the interface roughness. Results show that when Cd-composition increases additional linewidth broadening due to Zn/Cd interdiffusion is enhanced.  相似文献   
110.
The inhomogeneous Dirichlet problems concerning divergence form elliptic equations are studied. Optimal regularity requirements on the coefficients and domains for the W1,p theory, 1 < p < ∞, are obtained. The principal coefficients are supposed to be in the John‐Nirenberg space with small BMO seminorms. The domain is a Reifenberg domain. These conditions for the W1,p theory not only weaken the requirements on the coefficients but also lead to a more general geometric condition on the domains. In fact, these domains might have fractal dimensions. © 2004 Wiley Periodicals, Inc.  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