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   35668篇
  免费   6010篇
  国内免费   4279篇
化学   24146篇
晶体学   437篇
力学   2456篇
综合类   319篇
数学   4165篇
物理学   14434篇
  2024年   127篇
  2023年   698篇
  2022年   1321篇
  2021年   1424篇
  2020年   1453篇
  2019年   1355篇
  2018年   1274篇
  2017年   1231篇
  2016年   1748篇
  2015年   1744篇
  2014年   2105篇
  2013年   2745篇
  2012年   3110篇
  2011年   3186篇
  2010年   2232篇
  2009年   2151篇
  2008年   2387篇
  2007年   2102篇
  2006年   1902篇
  2005年   1584篇
  2004年   1197篇
  2003年   952篇
  2002年   873篇
  2001年   764篇
  2000年   682篇
  1999年   756篇
  1998年   607篇
  1997年   602篇
  1996年   564篇
  1995年   516篇
  1994年   417篇
  1993年   384篇
  1992年   307篇
  1991年   275篇
  1990年   260篇
  1989年   198篇
  1988年   154篇
  1987年   136篇
  1986年   102篇
  1985年   105篇
  1984年   67篇
  1983年   53篇
  1982年   54篇
  1981年   22篇
  1980年   12篇
  1979年   5篇
  1971年   1篇
  1959年   1篇
  1957年   9篇
  1936年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
GFFs with less than 0.4 dB peak-to-peak error functions are routinely fabricated using commercially available coating machines by utilizing the natural error compensation mechanism of wavelength variable turning point optical monitoring method.  相似文献   
92.
The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO2) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO2 causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO2 hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007  相似文献   
93.
The synthesis of three new series of chiral Schiff's bases containing benzilideneaniline and 2-hydroxybenzilideneaniline moieties as mesogenic cores is presented. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements were used to study the phase transition temperatures and behaviour. The results reveal that most of these materials show chiral smectic mesomorphism.  相似文献   
94.
Miniature, etching ridge InGaAsP/InP Phase Modulator with highly efficient phase shifting efficiency of 60°/V.mm and 43°/V.mm for TE and TM modes, respectively, and 3 dB bandwidth of 650 MHz at 1.52 μm are reported. It is well suited for integrated opto-electronics. Some functions depending on bandwidth of the devices are discussed.  相似文献   
95.
对任一函数f∈Lp[0,1],n阶Bernstein—Durrnieyer算子为  相似文献   
96.
The line search method incorporating the Wolfe conditions is modified to ensure that a descent algorithm terminates in a finite number of steps at an approximate stationary point where the second-order conditions of optimality are satisfied. A simple procedure based on conjugate directions is proposed to determine directions of negative curvature.  相似文献   
97.
98.
This paper studies the pullback asymptotic behavior of solutions for a non-autonomous incompressible non-Newtonian fluid in two-dimensional (2D) bounded domains. We first prove the existence of pullback attractors AV in space V (has H2-regularity, see notation in Section 2) and AH in space H (has L2-regularity) for the cocycle corresponding to the solutions of the fluid. Then we verify the regularity of the pullback attractors by showing AV=AH, which implies the pullback asymptotic smoothing effect of the fluid in the sense that the solutions become eventually more regular than the initial data.  相似文献   
99.
A molecular dynamics method has been used to simulate the argon ion-assisted deposition of Cu/Co/Cu multilayers and to explore ion beam assistance strategies that can be used during or after the growth of each layer to control interfacial structures. A low-argon ion energy of 5–10 eV was found to minimize a combination of interfacial roughness and interlayer mixing (alloying) during the ion-assisted deposition of multilayers. However, complete flattening with simultaneous ion assistance could not be achieved without some mixing between the layers when a constant ion energy approach was used. It was found that multilayers with lower interfacial roughness and intermixing could be grown either by modulating the ion energy during the growth of each metal layer or by utilizing ion assistance only after the completion of each layers deposition. In these latter approaches, relatively high-energy ions could be used since the interface is buried and less susceptible to intermixing. The interlayer mixing dependence upon the thickness of the over layer has been determined as a function of ion energy.  相似文献   
100.
The article referenced above was first published online on 7 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd.  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