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   203030篇
  免费   1287篇
  国内免费   428篇
化学   104708篇
晶体学   3391篇
力学   10273篇
综合类   10篇
数学   21830篇
物理学   64533篇
  2021年   1974篇
  2020年   2011篇
  2019年   2567篇
  2018年   3657篇
  2017年   3671篇
  2016年   4808篇
  2015年   2343篇
  2014年   4298篇
  2013年   8583篇
  2012年   6842篇
  2011年   8044篇
  2010年   6460篇
  2009年   6645篇
  2008年   7631篇
  2007年   7592篇
  2006年   6690篇
  2005年   5917篇
  2004年   5636篇
  2003年   5161篇
  2002年   5153篇
  2001年   5605篇
  2000年   4135篇
  1999年   3133篇
  1998年   2698篇
  1997年   2757篇
  1996年   2541篇
  1995年   2209篇
  1994年   2326篇
  1993年   2225篇
  1992年   2522篇
  1991年   2644篇
  1990年   2552篇
  1989年   2622篇
  1988年   2531篇
  1987年   2551篇
  1986年   2412篇
  1985年   3034篇
  1984年   3101篇
  1983年   2596篇
  1982年   2562篇
  1981年   2527篇
  1980年   2335篇
  1979年   2708篇
  1978年   2671篇
  1977年   2870篇
  1976年   2872篇
  1975年   2664篇
  1974年   2602篇
  1973年   2711篇
  1972年   2085篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This article deals with an expanded mixed finite element formulation, based on the Hu‐Washizu principle, for a nonlinear incompressible material in the plane. We follow our related previous works and introduce both the stress and the strain tensors as further unknowns, which yields a two‐fold saddle point operator equation as the corresponding variational formulation. A slight generalization of the classical Babu?ka‐Brezzi's theory is applied to prove unique solvability of the continuous and discrete formulations, and to derive the corresponding a priori error analysis. An extension of the well‐known PEERS space is used to define an stable associated Galerkin scheme. Finally, we provide an a posteriori error analysis based on the classical Bank‐Weiser approach. © 2002 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 18: 105–128, 2002  相似文献   
52.
53.
Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied.  相似文献   
54.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
55.
The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003  相似文献   
56.
57.
The generalized Hilbert symbol in a cyclotomic extension of an absolutely unramified higher local field of characteristic 0 with a perfect last residue field of characteristic p > 2 is considered. Generalized Artin–Hasse and Iwasawa formulas are derived from an explicit Kummer Type Vostokov formula. Bibliography: 13 titles.  相似文献   
58.
A semiclassical theory of electromagnetically induced transparency in a Bose-Einstein condensate is considered. A nonlinear Schrödinger equation that describes the interaction of the Bose-Einstein condensate with an electromagnetic field is derived. An analysis of the obtained solutions to this equation demonstrates a decrease in the group velocity of the light pulse.  相似文献   
59.
The projection approach is applied to construct and investigate an operator-difference scheme for fluid dynamics in Lagrangean variables which has first-order local approximation in the axisymmetric case near the symmetry axis. The scheme also has operator properties that make it suitable for rederiving and substantiating previous results, methods, and algorithms.  相似文献   
60.
Journal of Nanoparticle Research - It was shown that the thermoelastic martensite transformation B2 ? B19 inside nanoparticles surrounded by amorphous matrix in Ni–Ti–Cu alloys as...  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