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   24270篇
  免费   537篇
  国内免费   99篇
化学   13365篇
晶体学   142篇
力学   755篇
综合类   9篇
数学   3419篇
物理学   7216篇
  2022年   112篇
  2021年   347篇
  2020年   357篇
  2019年   313篇
  2018年   406篇
  2017年   364篇
  2016年   622篇
  2015年   517篇
  2014年   595篇
  2013年   966篇
  2012年   1251篇
  2011年   1427篇
  2010年   792篇
  2009年   751篇
  2008年   1202篇
  2007年   1174篇
  2006年   1060篇
  2005年   1490篇
  2004年   1519篇
  2003年   1049篇
  2002年   645篇
  2001年   553篇
  2000年   524篇
  1999年   303篇
  1998年   268篇
  1997年   269篇
  1996年   335篇
  1995年   310篇
  1994年   302篇
  1993年   327篇
  1992年   318篇
  1991年   260篇
  1990年   214篇
  1989年   202篇
  1988年   177篇
  1987年   173篇
  1986年   175篇
  1985年   230篇
  1984年   211篇
  1983年   182篇
  1982年   183篇
  1981年   180篇
  1980年   167篇
  1979年   150篇
  1978年   174篇
  1977年   137篇
  1976年   134篇
  1975年   112篇
  1974年   131篇
  1973年   121篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
1.
Meccanica - The driver coupled to a driven system through mechanical couplings is very common in rotating machinery. These couplings can present angular and parallel misalignments with more or less...  相似文献   
2.
3.
4.
Archiv der Mathematik - In this paper, we establish a sharp integral inequality for n-dimensional closed spacelike submanifolds with constant scalar curvature immersed with parallel normalized mean...  相似文献   
5.
Central European Journal of Operations Research - Societal awareness and legislation changes concerning sustainability have affected how organizations generate value for stakeholders, as well as...  相似文献   
6.
Journal of Thermal Analysis and Calorimetry - The hot coil slump is a recurrent problem in the manufacturing process of medium and high equivalent carbon steel plates. Even with the success of the...  相似文献   
7.
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   
8.
Herein, we report ultrasound-propelled graphene-oxide coated gold nanowire motors, functionalized with fluorescein-labeled DNA aptamers (FAM-AIB1-apt), for qualitative detection of overexpressed AIB1 oncoproteins in MCF-7 breast cancer cells. The movement of nanomotors under the ultrasound field facilitated intracellular uptake and resulted in a faster aptamer binding with the target protein and thus faster fluorescence recovery. The propulsion behavior of the aptamer functionalized nanomotors greatly enhanced the fluorescence intensity compared to static conditions. The new aptamer@nanomotor-based strategy offers considerable potential for further development of sensing methodologies towards diagnosis of breast cancer.  相似文献   
9.
The emergence of untreatable drug-resistant strains of Mycobacterium tuberculosis is a major public health problem worldwide, and the identification of new efficient treatments is urgently needed. Mycobacterium tuberculosis cytochrome P450 CYP121A1 is a promising drug target for the treatment of tuberculosis owing to its essential role in mycobacterial growth. Using a rational approach, which includes molecular modelling studies, three series of azole pyrazole derivatives were designed through two synthetic pathways. The synthesized compounds were biologically evaluated for their inhibitory activity towards M. tuberculosis and their protein binding affinity (KD). Series 3 biarylpyrazole imidazole derivatives were the most effective with the isobutyl ( 10 f ) and tert-butyl ( 10 g ) compounds displaying optimal activity (MIC 1.562 μg/mL, KD 0.22 μM ( 10 f ) and 4.81 μM ( 10 g )). The spectroscopic data showed that all the synthesised compounds produced a type II red shift of the heme Soret band indicating either direct binding to heme iron or (where less extensive Soret shifts are observed) putative indirect binding via an interstitial water molecule. Evaluation of biological and physicochemical properties identified the following as requirements for activity: LogP >4, H-bond acceptors/H-bond donors 4/0, number of rotatable bonds 5–6, molecular volume >340 Å3, topological polar surface area <40 Å2.  相似文献   
10.
A fast and accurate experimental method is demonstrated to assess the fraction of exsolved metallic nanoparticles using magnetic measurements. As a benchmark, nanometric metallic nickel exsolved from (La1−xSrx)(Cr1−yNiy)O3−δ is used for its high relevance as a solid oxide fuel cell component. The method is based on the difference in the magnetic response of the exsolved metallic nickel (ferromagnetic) and Sr-doped lanthanum chromite ceramic matrix (paramagnetic). The exsolved nickel results in coherent nanoparticles pinned on the surface of the Sr-doped lanthanum chromite ceramic matrix, as evidenced by electron microscopy analyses. The results obtained indicate the procedure as a fast and sensitive method to study the exsolution of ferromagnetic nanoparticles.  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