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   38317篇
  免费   6556篇
  国内免费   4581篇
化学   27401篇
晶体学   487篇
力学   2340篇
综合类   366篇
数学   4196篇
物理学   14664篇
  2024年   85篇
  2023年   793篇
  2022年   1185篇
  2021年   1328篇
  2020年   1651篇
  2019年   1578篇
  2018年   1329篇
  2017年   1289篇
  2016年   1850篇
  2015年   1793篇
  2014年   2144篇
  2013年   2773篇
  2012年   3466篇
  2011年   3455篇
  2010年   2371篇
  2009年   2379篇
  2008年   2602篇
  2007年   2303篇
  2006年   2194篇
  2005年   1790篇
  2004年   1390篇
  2003年   1108篇
  2002年   974篇
  2001年   815篇
  2000年   751篇
  1999年   820篇
  1998年   672篇
  1997年   614篇
  1996年   593篇
  1995年   536篇
  1994年   469篇
  1993年   438篇
  1992年   358篇
  1991年   312篇
  1990年   296篇
  1989年   201篇
  1988年   160篇
  1987年   118篇
  1986年   127篇
  1985年   95篇
  1984年   53篇
  1983年   59篇
  1982年   43篇
  1981年   30篇
  1980年   14篇
  1979年   12篇
  1977年   4篇
  1975年   5篇
  1965年   4篇
  1957年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Cai  Peng  Yue  Xiaokui  Wang  Mingming  Cui  Yao 《Nonlinear dynamics》2022,108(3):2309-2322
Nonlinear Dynamics - A capacitive micromachined ultrasonic transducer (CMUT) due to many benefits is being considered as an imaging and therapeutic technology recently. The critical challenge is to...  相似文献   
22.
Methodology and Computing in Applied Probability - This paper is devoted to the study of an optimal investment and risk control problem for an insurer. The risky asset process and the insurance...  相似文献   
23.
Journal of Radioanalytical and Nuclear Chemistry - In the present work the final products of coumarin radiation chemical transformation are investigated by chromatography. During radiolysis of...  相似文献   
24.
25.
26.
Zhu  Lina  Zheng  Yangong  Jian  Jiawen 《Ionics》2015,21(10):2919-2926
Ionics - This study aims to explore the potential merits of palladium oxide sensing electrode. PdO is applied on a solid-state potentiometric sensor on an yttria-stabilized zirconia (YSZ)...  相似文献   
27.
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   
28.
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
29.
30.
Li  C.  Zhang  D.  Cheng  G.  Zhu  Y. 《Experimental Mechanics》2020,60(3):329-343
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices....  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