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   162267篇
  免费   16909篇
  国内免费   9721篇
化学   83430篇
晶体学   1651篇
力学   11927篇
综合类   527篇
数学   41211篇
物理学   50151篇
  2024年   231篇
  2023年   2003篇
  2022年   2626篇
  2021年   3158篇
  2020年   3904篇
  2019年   3482篇
  2018年   12782篇
  2017年   12309篇
  2016年   10063篇
  2015年   4972篇
  2014年   5410篇
  2013年   6897篇
  2012年   11669篇
  2011年   18384篇
  2010年   10921篇
  2009年   11150篇
  2008年   12082篇
  2007年   13514篇
  2006年   5048篇
  2005年   5145篇
  2004年   4453篇
  2003年   4243篇
  2002年   3131篇
  2001年   2097篇
  2000年   1931篇
  1999年   2023篇
  1998年   1799篇
  1997年   1726篇
  1996年   1767篇
  1995年   1443篇
  1994年   1233篇
  1993年   1094篇
  1992年   922篇
  1991年   856篇
  1990年   696篇
  1989年   561篇
  1988年   432篇
  1987年   367篇
  1986年   384篇
  1985年   312篇
  1984年   194篇
  1983年   153篇
  1982年   142篇
  1981年   95篇
  1980年   88篇
  1979年   55篇
  1914年   45篇
  1912年   40篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
JPC – Journal of Planar Chromatography – Modern TLC - A new high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of...  相似文献   
53.
Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been deemed as clean and sustainable strategies to solve the energy crisis and environmental problems. Various catalysts have been developed to promote the process of HER and OER. Among them, two-dimensional covalent organic frameworks (2D COFs) have received great attention due to their diverse and designable structure. In this minireview, we mainly summarize the diverse linkages of 2D COFs and strategies for enhancing the catalytic performance of 2D COFs for HER and OER, such as introducing active building blocks, metal ions and tailored linkages. Furthermore, a brief outlook for the development directions of COFs in the field of HER and OER is provided, expecting to stimulate new opportunities in future research.  相似文献   
54.
Natural products with a variety of pharmacological effects are important sources for commercial drugs, and it is very crucial to develop effective techniques to selectively extract and isolate bioactive natural components from the plants against the background of sustainable development. Ionic liquids (ILs) are a kind of designable material with unique physicochemical properties, including good thermal stability, negligible vapor pressure, good solvation ability, etc. ILs have already been used in pharmaceuticals for extraction, purification, drug delivery, etc. It has been reported that multi-interactions, like hydrogen bonding, hydrophobic interactions, play important roles in the extraction of bioactive components from the plants. In this review, recent progress in the understanding of scientific essence of hydrogen bonding, the special interaction, in ILs was summarized. The extraction of various natural products, one important area in pharmaceutical, by conventional and functional ILs as well as the specific roles of multi-interactions in this process were also reviewed. Moreover, problems existing in bioactive compound extraction by ILs and the future developing trends of this area are given, which might be helpful for scientists, especially beginners, in this field.  相似文献   
55.
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential...  相似文献   
56.
The biodegradability of phtalic acid esters in marine and freshwater environments was characterized by their binding free energy with corresponding degrading enzymes. According to comprehensive biodegradation effects weights, the binding free energy values were converted into dimensionless efficacy coefficient using ratio normalization method. Then, considering comprehensive dual biodegradation effects value and the structural parameters of PAEs in both marine and freshwater environments, a 3D-QSAR pharmacophore model was constructed, five PAE derivatives (DBP−COOH, DBP−CHO, DBP−OH, DINP−NH2, and DINP−NO2) were screened out based on their environmental friendliness, functionality and stability. The prediction of biodegradation effects on five PAE derivatives by biodegradation models in marine and freshwater environment increased by 15.90 %, 15.84 %, 27.21 %, 12.33 %, and 8.32 %, and 21.57 %, 15.21 %, 20.99 %, 15.10 %, and 9.74 %, respectively. By simulating the photodegradation path of the PAE derivative molecular, it was found that DBP−OH can generate .OH and provides free radicals for the photodegradation of microplastics in the environment.  相似文献   
57.
58.
59.
60.
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