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   64056篇
  免费   1009篇
  国内免费   300篇
化学   31083篇
晶体学   1031篇
力学   3312篇
综合类   8篇
数学   5158篇
物理学   24773篇
  2022年   530篇
  2021年   662篇
  2020年   586篇
  2019年   575篇
  2018年   701篇
  2017年   589篇
  2016年   1108篇
  2015年   815篇
  2014年   1219篇
  2013年   2824篇
  2012年   2703篇
  2011年   3430篇
  2010年   2400篇
  2009年   2457篇
  2008年   3108篇
  2007年   2888篇
  2006年   2720篇
  2005年   2393篇
  2004年   2170篇
  2003年   1893篇
  2002年   1764篇
  2001年   3095篇
  2000年   2231篇
  1999年   1610篇
  1998年   1130篇
  1997年   1103篇
  1996年   924篇
  1995年   821篇
  1994年   745篇
  1993年   668篇
  1992年   996篇
  1991年   970篇
  1990年   875篇
  1989年   765篇
  1988年   750篇
  1987年   810篇
  1986年   659篇
  1985年   887篇
  1984年   835篇
  1983年   579篇
  1982年   567篇
  1981年   553篇
  1980年   504篇
  1979年   629篇
  1978年   660篇
  1977年   667篇
  1976年   582篇
  1975年   490篇
  1974年   529篇
  1973年   454篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
21.
Meccanica - Fiber reinforced materials are used in assorted engineering application and for this reason, new additive manufacturing technologies have been developed for this type of materials. With...  相似文献   
22.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
23.
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   
24.
25.
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication.  相似文献   
26.
27.
28.
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   
29.
Applied Biochemistry and Biotechnology - The human exposure to bisphenol A (BPA) occurs frequently. Once, this compound was one of the highest volume chemicals produced worldwide and used as a...  相似文献   
30.
In this work, we have used the MuMax3 software to simulate devices consisting of a ferromagnetic thin film placed over a heavy metal thin film. The devices are two interconnected partial-disks where a Néel domain wall is formed in the disks junction. In our simulations we investigate devices with disk radius r=50 nm and different distance d between the disks centers (from d=12 nm to d=2R=100 nm). By applying strong sinusoidal external magnetic fields, we find a mechanism able to create, annihilate and even manipulate a skyrmion in each side of the device. This mechanism is discussed in terms of interactions between skyrmion and domain wall. The Néel domain wall formed in the center of the device interacts with the Néel skyrmion, leading to a process of transporting a skyrmion from one disk to the other periodically. Our results have relevance for potential applications in spintronics such as logical 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