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   196662篇
  免费   2315篇
  国内免费   618篇
化学   109388篇
晶体学   3313篇
力学   7868篇
综合类   4篇
数学   18533篇
物理学   60489篇
  2016年   2361篇
  2015年   1765篇
  2014年   2528篇
  2013年   7992篇
  2012年   5458篇
  2011年   6821篇
  2010年   4561篇
  2009年   4469篇
  2008年   6148篇
  2007年   6285篇
  2006年   6033篇
  2005年   5512篇
  2004年   5035篇
  2003年   4498篇
  2002年   4358篇
  2001年   5812篇
  2000年   4409篇
  1999年   3533篇
  1998年   2758篇
  1997年   2790篇
  1996年   2746篇
  1995年   2524篇
  1994年   2398篇
  1993年   2291篇
  1992年   2784篇
  1991年   2666篇
  1990年   2612篇
  1989年   2642篇
  1988年   2580篇
  1987年   2587篇
  1986年   2401篇
  1985年   3266篇
  1984年   3283篇
  1983年   2712篇
  1982年   2908篇
  1981年   2844篇
  1980年   2752篇
  1979年   2893篇
  1978年   3137篇
  1977年   2960篇
  1976年   2894篇
  1975年   2754篇
  1974年   2700篇
  1973年   2715篇
  1972年   1759篇
  1971年   1467篇
  1968年   1929篇
  1967年   2130篇
  1966年   1920篇
  1965年   1497篇
排序方式: 共有10000条查询结果,搜索用时 686 毫秒
31.
32.
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   
33.
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   
34.
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   
35.
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   
36.
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