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   45746篇
  免费   1225篇
  国内免费   281篇
化学   31261篇
晶体学   380篇
力学   1039篇
综合类   2篇
数学   7578篇
物理学   6992篇
  2021年   377篇
  2020年   521篇
  2019年   575篇
  2018年   418篇
  2017年   388篇
  2016年   860篇
  2015年   707篇
  2014年   911篇
  2013年   2266篇
  2012年   2160篇
  2011年   2779篇
  2010年   1397篇
  2009年   1156篇
  2008年   2368篇
  2007年   2509篇
  2006年   2456篇
  2005年   2444篇
  2004年   2128篇
  2003年   1795篇
  2002年   1752篇
  2001年   644篇
  2000年   580篇
  1999年   486篇
  1998年   523篇
  1997年   548篇
  1996年   600篇
  1995年   508篇
  1994年   481篇
  1993年   541篇
  1992年   480篇
  1991年   421篇
  1990年   405篇
  1989年   391篇
  1988年   413篇
  1987年   419篇
  1986年   378篇
  1985年   596篇
  1984年   697篇
  1983年   505篇
  1982年   642篇
  1981年   652篇
  1980年   515篇
  1979年   518篇
  1978年   572篇
  1977年   496篇
  1976年   448篇
  1975年   428篇
  1974年   436篇
  1973年   390篇
  1972年   219篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
Journal of Fluorescence - This report describes a combined immunofluorescence and fluorescence viability stain applied as one staining solution for rapid detection of live Legionella...  相似文献   
2.
3.
In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography.  相似文献   
4.
5.
6.
7.
The current study attempted, for the first time, to qualitatively and quantitatively determine the phytochemical components of Elatostema papillosum methanol extract and their biological activities. The present study represents an effort to correlate our previously reported biological activities with a computational study, including molecular docking, and ADME/T (absorption, distribution, metabolism, and excretion/toxicity) analyses, to identify the phytochemicals that are potentially responsible for the antioxidant, antidepressant, anxiolytic, analgesic, and anti-inflammatory activities of this plant. In the gas chromatography-mass spectroscopy analysis, a total of 24 compounds were identified, seven of which were documented as being bioactive based on their binding affinities. These seven were subjected to molecular docking studies that were correlated with the pharmacological outcomes. Additionally, the ADME/T properties of these compounds were evaluated to determine their drug-like properties and toxicity levels. The seven selected, isolated compounds displayed favorable binding affinities to potassium channels, human serotonin receptor, cyclooxygenase-1 (COX-1), COX-2, nuclear factor (NF)-κB, and human peroxiredoxin 5 receptor proteins. Phytol acetate, and terpene compounds identified in E. papillosum displayed strong predictive binding affinities towards the human serotonin receptor. Furthermore, 3-trifluoroacetoxypentadecane showed a significant binding affinity for the KcsA potassium channel. Eicosanal showed the highest predicted binding affinity towards the human peroxiredoxin 5 receptor. All of these findings support the observed in vivo antidepressant and anxiolytic effects and the in vitro antioxidant effects observed for this extract. The identified compounds from E. papillosum showed the lowest binding affinities towards COX-1, COX-2, and NF-κB receptors, which indicated the inconsequential impacts of this extract against the activities of these three proteins. Overall, E. papillosum appears to be bioactive and could represent a potential source for the development of alternative medicines; however, further analytical experiments remain necessary.  相似文献   
8.
Daylight photodynamic therapy (DPDT) is an effective and patient preferred treatment for the management of field change actinic keratosis. An important factor in DPDT is light dosimetry, to ensure that patients receive sufficient daylight for effective treatment, and this is the focus of the contribution to this issue by (La Rochelle et al. [2019] Photochem. Photobiol., https://doi.org/10.1111/php.13170 ). In this work, the authors present an easy-to-use method for obtaining real-time information about patient received light dose during treatment and for determining indoor locations best suited to DPDT.  相似文献   
9.
The complex interplay of restricted mass transport leading to local accumulation or depletion of educts, intermediates, products, counterions and co-ions influences the reactions at the active sites of electrocatalysts when electrodes are rough, three-dimensionally mesoporous or nanoporous. This influence is important with regard to activity, and even more to selectivity, of electrocatalytic reactions. The underlying principles are discussed based on the growing awareness of these considerations over recent years.  相似文献   
10.
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