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   262673篇
  免费   3829篇
  国内免费   505篇
化学   145465篇
晶体学   3321篇
力学   11018篇
综合类   7篇
数学   29864篇
物理学   77332篇
  2021年   2222篇
  2020年   2571篇
  2019年   2769篇
  2018年   3826篇
  2017年   3730篇
  2016年   5732篇
  2015年   3719篇
  2014年   5211篇
  2013年   11854篇
  2012年   10486篇
  2011年   12158篇
  2010年   8378篇
  2009年   8078篇
  2008年   10915篇
  2007年   10849篇
  2006年   10115篇
  2005年   9295篇
  2004年   8273篇
  2003年   7207篇
  2002年   7088篇
  2001年   6936篇
  2000年   5309篇
  1999年   4064篇
  1998年   3555篇
  1997年   3408篇
  1996年   3192篇
  1995年   2872篇
  1994年   2914篇
  1993年   2766篇
  1992年   3091篇
  1991年   3202篇
  1990年   2967篇
  1989年   2995篇
  1988年   2805篇
  1987年   2646篇
  1986年   2520篇
  1985年   3308篇
  1984年   3463篇
  1983年   2860篇
  1982年   3112篇
  1981年   2884篇
  1980年   2765篇
  1979年   2946篇
  1978年   3215篇
  1977年   3057篇
  1976年   3060篇
  1975年   2884篇
  1974年   2957篇
  1973年   2914篇
  1972年   1930篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Journal of Experimental and Theoretical Physics - We suggest that the principle of holographic duality be extended beyond conformal invariance and AdS isometry. Such an extension is based on a...  相似文献   
62.
63.
64.
65.
66.
In this paper, we study the local linear convergence properties of a versatile class of Primal–Dual splitting methods for minimizing composite non-smooth convex optimization problems. Under the assumption that the non-smooth components of the problem are partly smooth relative to smooth manifolds, we present a unified local convergence analysis framework for these methods. More precisely, in our framework, we first show that (i) the sequences generated by Primal–Dual splitting methods identify a pair of primal and dual smooth manifolds in a finite number of iterations, and then (ii) enter a local linear convergence regime, which is characterized based on the structure of the underlying active smooth manifolds. We also show how our results for Primal–Dual splitting can be specialized to cover existing ones on Forward–Backward splitting and Douglas–Rachford splitting/ADMM (alternating direction methods of multipliers). Moreover, based on these obtained local convergence analysis result, several practical acceleration techniques are discussed. To exemplify the usefulness of the obtained result, we consider several concrete numerical experiments arising from fields including signal/image processing, inverse problems and machine learning. The demonstration not only verifies the local linear convergence behaviour of Primal–Dual splitting methods, but also the insights on how to accelerate them in practice.  相似文献   
67.
Human skin is exposed to visible light (VL; 400–700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range.  相似文献   
68.
69.
70.
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