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   324767篇
  免费   3765篇
  国内免费   993篇
化学   181943篇
晶体学   5253篇
力学   13262篇
综合类   7篇
数学   31661篇
物理学   97399篇
  2018年   2931篇
  2017年   2883篇
  2016年   4817篇
  2015年   3268篇
  2014年   4830篇
  2013年   13606篇
  2012年   10088篇
  2011年   12300篇
  2010年   8367篇
  2009年   8258篇
  2008年   11297篇
  2007年   11200篇
  2006年   10765篇
  2005年   9822篇
  2004年   8897篇
  2003年   8092篇
  2002年   7860篇
  2001年   10168篇
  2000年   7627篇
  1999年   5970篇
  1998年   4497篇
  1997年   4630篇
  1996年   4501篇
  1995年   4142篇
  1994年   4056篇
  1993年   3755篇
  1992年   4577篇
  1991年   4544篇
  1990年   4379篇
  1989年   4345篇
  1988年   4239篇
  1987年   4250篇
  1986年   3964篇
  1985年   5205篇
  1984年   5252篇
  1983年   4332篇
  1982年   4503篇
  1981年   4330篇
  1980年   4237篇
  1979年   4581篇
  1978年   4949篇
  1977年   4699篇
  1976年   4609篇
  1975年   4382篇
  1974年   4288篇
  1973年   4355篇
  1972年   2893篇
  1968年   2722篇
  1967年   2794篇
  1966年   2457篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
63.
64.
65.
66.
67.
68.
Journal of Thermal Analysis and Calorimetry - In the present study, numerical simulations have been carried out on thermal characteristics and second-law analysis of turbulent Cu–H2O...  相似文献   
69.
70.
Oral microbes have the capacity to spread throughout the gastrointestinal system and are strongly associated with multiple diseases. Given that tonsils are located between the oral cavity and the laryngopharynx at the gateway of the alimentary and respiratory tracts, tonsillar tissue may also be affected by microbiota from both the oral cavity (saliva) and the alimentary tract. Here, we analyzed the distribution and association of the microbial communities in the saliva and tonsils of Korean children subjected to tonsillectomy because of tonsil hyperplasia (n = 29). The microbiome profiles of saliva and tonsils were established via 16S rRNA gene sequencing. Based on the alpha diversity indices, the microbial communities of the two groups showed high similarities. According to Spearman’s ranking correlation analysis, the distribution of Treponema, the causative bacterium of periodontitis, in saliva and tonsils was found to have a significant positive correlation. Two representative microbes, Prevotella in saliva and Alloprevotella in tonsils, were negatively correlated, while Treponema 2 showed a strong positive correlation between saliva and tonsils. Taken together, strong similarities in the microbial communities of the tonsils and saliva are evident in terms of diversity and composition. The saliva microbiome is expected to significantly affect the tonsil microbiome. Furthermore, we suggest that our study creates an opportunity for tonsillar microbiome research to facilitate the development of novel microbiome-based therapeutic strategies.Subject terms: Comparative genomics, Metagenomics  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