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   146867篇
  免费   27910篇
  国内免费   12969篇
化学   113846篇
晶体学   1601篇
力学   8144篇
综合类   655篇
数学   16111篇
物理学   47389篇
  2024年   269篇
  2023年   2303篇
  2022年   3415篇
  2021年   4217篇
  2020年   5649篇
  2019年   6565篇
  2018年   4675篇
  2017年   4146篇
  2016年   8465篇
  2015年   8286篇
  2014年   9398篇
  2013年   12015篇
  2012年   12834篇
  2011年   12771篇
  2010年   9717篇
  2009年   9387篇
  2008年   9439篇
  2007年   8246篇
  2006年   7429篇
  2005年   6596篇
  2004年   5150篇
  2003年   4260篇
  2002年   4801篇
  2001年   3677篇
  2000年   3296篇
  1999年   2784篇
  1998年   2166篇
  1997年   2010篇
  1996年   2183篇
  1995年   1750篇
  1994年   1653篇
  1993年   1303篇
  1992年   1218篇
  1991年   1129篇
  1990年   906篇
  1989年   649篇
  1988年   511篇
  1987年   433篇
  1986年   439篇
  1985年   361篇
  1984年   269篇
  1983年   180篇
  1982年   157篇
  1981年   117篇
  1980年   80篇
  1979年   44篇
  1978年   34篇
  1976年   37篇
  1975年   35篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
101.
102.
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   
103.
Journal of Thermal Analysis and Calorimetry - The fire behavior of one flame-retardant PVC cable used as building wire is investigated in this work. Bench scale tests were performed using a cone...  相似文献   
104.
105.
106.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
107.
108.
Transition Metal Chemistry - Two cubane-like complexes, namely [Ni4L4(HOEt)4] (1), [Co4L4(HOEt)4] (2) (H2L?=?(E)-2-((3-hydroxypropylimino)methyl)-6-methoxyphenol), were prepared under...  相似文献   
109.
Guided by the self-penetrating features can improve the stability of metal organic frameworks (MOFs), an unprecedented 3D self-penetrated framework, {[Zn (tptc)0.5(bimb)]·H2O}n ( NUC-6 , here NUC corresponding to North University of China), with 3D (4,4)-c {86} net, was designed. Benefit from the high chemical stability and excellent luminescent property, NUC-6 can be act as an efficient multi-response chemo-sensor in detecting dichloronitroaniline pesticide and nitrofuran antibiotics in water with the detection limits are 116 ppb for DCN pesticide, 16 ppb for NFT antibiotic, and 12 ppb for NTZ antibiotic. Besides, the mechanisms of luminescence quenching were revealed from the viewpoint of internal filter effect (IFE) and photo-induced electron transfer (PET), implied by the optical spectroscopy and quantum chemical calculation. This work provides a promising strategy to design stable MOFs by improving the self-penetrating features and to expand their practical applications in the detection of organic pollutants in aqueous medium.  相似文献   
110.
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors.  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