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   66194篇
  免费   1059篇
  国内免费   480篇
化学   31755篇
晶体学   1122篇
力学   3500篇
综合类   33篇
数学   5711篇
物理学   25612篇
  2022年   731篇
  2021年   733篇
  2020年   736篇
  2019年   728篇
  2018年   747篇
  2017年   646篇
  2016年   1148篇
  2015年   857篇
  2014年   1234篇
  2013年   2965篇
  2012年   2760篇
  2011年   3489篇
  2010年   2424篇
  2009年   2442篇
  2008年   3096篇
  2007年   2874篇
  2006年   2745篇
  2005年   2429篇
  2004年   2175篇
  2003年   1951篇
  2002年   1810篇
  2001年   3148篇
  2000年   2282篇
  1999年   1649篇
  1998年   1142篇
  1997年   1111篇
  1996年   947篇
  1995年   832篇
  1994年   779篇
  1993年   682篇
  1992年   1021篇
  1991年   999篇
  1990年   903篇
  1989年   790篇
  1988年   772篇
  1987年   830篇
  1986年   690篇
  1985年   939篇
  1984年   883篇
  1983年   601篇
  1982年   615篇
  1981年   575篇
  1980年   544篇
  1979年   669篇
  1978年   702篇
  1977年   704篇
  1976年   617篇
  1975年   516篇
  1974年   547篇
  1973年   485篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
Constructing molecular switches based on supramolecular assembly strategy is a research hotspot. In this work, we constructed an all visible-light-regulated supramolecular photo-switch based on pyridinium-modified diarylethene derivative (DTE-Me) and cucurbit[8]uril (CB[8]). CB[8] not only accelerated the photochromic process under 365 nm ultraviolet light but also shifted the absorption of open formed DTE-Me to the visible region, which led to efficient photocyclization under 450 nm visible light irradiation, while DTE-Me and DTE-Me/CB[7] remained unchanged under the same irradiating condition. Moreover, the complexation with CB[8] could induce the strong thermally activated delayed fluorescence (TADF) of guest molecular at 550 nm, which further shifted to 670 nm through two-step sequential energy transfer with sulforhodamine B (SRB) and Cy5. This energy transfer process could also be regulated with visible light, and the application for information encryption was also demonstrated. This assembly provides a convenient approach to construct all visible light-regulated TADF photo-switch.  相似文献   
15.
Aluminum is one of the most toxic metals causing a variety of neurologic diseases, especially Alzheimer's disease. It is impossible to avoid contact with aluminum because of its existence in food to medications. Therefore, removal of aluminum from the blood or wastewater is urgently important. The cost-effective and easy-to-prepare adsorbents are needed to get efficient aluminum removal. For that purpose, the poly(2-hydroxyethylmethacrylate-co-acrylic acid), poly(HEMA-co-AA), microparticles was synthesized to remove aluminum in a very short interaction time. The achievement of the desired polymeric structure was confirmed via Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM), etc. Additionally, particle features such as swelling ratio, size, and surface area were determined. The microparticles synthesized in this study have been determined with very good adsorption capacity even in small aluminum concentrations.  相似文献   
16.
The disinfection of the inner surface of a medical device has long been a challenge for the central sterile supply departments. Dental unit waterline system (DUWLs) foster the attachment of microorganisms and development of biofilm, which lead to continuous contamination of the outlet water from dental units; this contamination may be responsible for a potential risk of infection due to the exposure of patients and medical staff. The present study investigated the disinfection effects of cold atmospheric plasma-activated water (CAPAW) on DUWLs using a model of 5-day-old Enterococcus faecalis biofilm. The results showed that the colony-forming unit was reduced from 107 to 0 after 5 min of treatment. The physicochemical properties of CAPAW were evaluated, including the pH value, oxidation reduction potential, and NO radical. The results showed that the inactivation mechanisms were mainly triggered by the reactive oxygen/nitrogen species. Additionally, CAPAW had a metal corrosion rate same as that of deionized water. We conclude that CAPAW can be applied as an appropriate alternative disinfectant against biofilm contamination of DUWLs.  相似文献   
17.
Research on Chemical Intermediates - This study presents the synthesis of rare earth-doped Y (RE Y) zeolite, its application in formulation of a fluid catalytic cracking (FCC) catalyst and the...  相似文献   
18.
  相似文献   
19.
Chen  Yu.  Li  Y.  Tang  Q. 《Siberian Mathematical Journal》2017,58(1):176-182
Siberian Mathematical Journal - We give Gröbner–Shirshov bases for the Drinfeld–Kohno Lie algebra L n in [1] and the Kukin Lie algebra A P in [2], where P is a semigroup. By way of...  相似文献   
20.
Mu  D. D.  Zhao  Y. X.  Sun  G. Y.  Bobakulov  Kh. M.  Aisa  H. A.  Wu  T. 《Chemistry of Natural Compounds》2021,57(5):939-941
Chemistry of Natural Compounds -  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