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   195648篇
  免费   2152篇
  国内免费   614篇
化学   108115篇
晶体学   3316篇
力学   7917篇
综合类   4篇
数学   18471篇
物理学   60591篇
  2016年   2280篇
  2015年   1688篇
  2014年   2402篇
  2013年   7871篇
  2012年   5273篇
  2011年   6644篇
  2010年   4444篇
  2009年   4399篇
  2008年   6018篇
  2007年   6192篇
  2006年   5938篇
  2005年   5432篇
  2004年   4972篇
  2003年   4461篇
  2002年   4334篇
  2001年   5803篇
  2000年   4407篇
  1999年   3547篇
  1998年   2773篇
  1997年   2798篇
  1996年   2771篇
  1995年   2540篇
  1994年   2406篇
  1993年   2302篇
  1992年   2791篇
  1991年   2685篇
  1990年   2636篇
  1989年   2655篇
  1988年   2593篇
  1987年   2603篇
  1986年   2419篇
  1985年   3283篇
  1984年   3302篇
  1983年   2731篇
  1982年   2923篇
  1981年   2855篇
  1980年   2764篇
  1979年   2905篇
  1978年   3144篇
  1977年   2969篇
  1976年   2905篇
  1975年   2762篇
  1974年   2708篇
  1973年   2722篇
  1972年   1768篇
  1971年   1474篇
  1968年   1943篇
  1967年   2134篇
  1966年   1924篇
  1965年   1500篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
31.
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   
32.
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   
33.
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   
34.
35.
36.
37.
38.
39.
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.  相似文献   
40.
Xu  H. J.  Zhang  Q. G.  Debenest  G. 《Transport in Porous Media》2021,140(3):625-627
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the...  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