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   203554篇
  免费   3225篇
  国内免费   1305篇
化学   114334篇
晶体学   2465篇
力学   8264篇
综合类   55篇
数学   19771篇
物理学   63195篇
  2018年   1504篇
  2016年   2657篇
  2015年   2077篇
  2014年   2850篇
  2013年   8508篇
  2012年   6077篇
  2011年   7568篇
  2010年   5031篇
  2009年   4981篇
  2008年   6680篇
  2007年   6806篇
  2006年   6477篇
  2005年   5900篇
  2004年   5424篇
  2003年   4834篇
  2002年   4660篇
  2001年   6056篇
  2000年   4631篇
  1999年   3694篇
  1998年   2889篇
  1997年   2903篇
  1996年   2883篇
  1995年   2636篇
  1994年   2538篇
  1993年   2337篇
  1992年   2782篇
  1991年   2622篇
  1990年   2591篇
  1989年   2595篇
  1988年   2550篇
  1987年   2527篇
  1986年   2355篇
  1985年   3268篇
  1984年   3269篇
  1983年   2676篇
  1982年   2851篇
  1981年   2808篇
  1980年   2685篇
  1979年   2848篇
  1978年   3106篇
  1977年   2920篇
  1976年   2876篇
  1975年   2720篇
  1974年   2683篇
  1973年   2710篇
  1972年   1734篇
  1968年   1934篇
  1967年   2130篇
  1966年   1925篇
  1965年   1502篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
In many organic electronic devices functionality is achieved by blending two or more materials, typically polymers or molecules, with distinctly different optical or electrical properties in a single film. The local scale morphology of such blends is vital for the device performance. Here, a simple approach to study the full 3D morphology of phase‐separated blends, taking advantage of the possibility to selectively dissolve the different components is introduced. This method is applied in combination with AFM to investigate a blend of a semiconducting and ferroelectric polymer typically used as active layer in organic ferroelectric resistive switches. It is found that the blend consists of a ferroelectric matrix with three types of embedded semiconductor domains and a thin wetting layer at the bottom electrode. Statistical analysis of the obtained images excludes the presence of a fourth type of domains. The criteria for the applicability of the presented technique are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1231–1237  相似文献   
34.
Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers...  相似文献   
35.
Journal of Thermal Analysis and Calorimetry - Low productivity of single-slope solar still is the main barrier for its worldwide usability. An attempt has been conducted to enhance the distillate...  相似文献   
36.
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   
37.
38.
39.
40.
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