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   52573篇
  免费   9207篇
  国内免费   3845篇
化学   47238篇
晶体学   498篇
力学   1836篇
综合类   220篇
数学   4346篇
物理学   11487篇
  2024年   267篇
  2023年   535篇
  2022年   942篇
  2021年   1166篇
  2020年   2253篇
  2019年   3456篇
  2018年   1643篇
  2017年   1231篇
  2016年   3791篇
  2015年   3814篇
  2014年   3918篇
  2013年   4725篇
  2012年   4203篇
  2011年   3587篇
  2010年   3567篇
  2009年   3460篇
  2008年   3208篇
  2007年   2578篇
  2006年   2220篇
  2005年   2164篇
  2004年   1840篇
  2003年   1574篇
  2002年   2181篇
  2001年   1620篇
  2000年   1427篇
  1999年   785篇
  1998年   447篇
  1997年   360篇
  1996年   346篇
  1995年   324篇
  1994年   269篇
  1993年   255篇
  1992年   195篇
  1991年   211篇
  1990年   186篇
  1989年   158篇
  1988年   143篇
  1987年   100篇
  1986年   78篇
  1985年   102篇
  1984年   48篇
  1983年   51篇
  1982年   45篇
  1981年   28篇
  1980年   15篇
  1979年   15篇
  1978年   11篇
  1977年   11篇
  1976年   9篇
  1973年   10篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
52.
The olive tree (Olea europaea L.) can be affected by Colletotrichum acutatum, causing a loss of yield and quality of the final products, whilst the incidence of this fungal infection depends on several factors, including cultivar susceptibility. Thus, the effect of C. acutatum infection in cultivars displaying different susceptibilities to this fungal disease (‘Galega Vulgar’ ‐ susceptible, ‘Cobrançosa’ ‐ moderately susceptible, ‘Picual’ ‐ tolerant) has been assessed through spectrophotometric methods and HPLC, while the FTIR spectra of the cuticles have been concomitantly registered, resorting to the ATR accessory. With the support of multivariate analysis, these spectra allowed to discriminate olives with distinct infection times, besides retrieving evidences concerning the different susceptibility of each cultivar, while these observations were reinforced by the spectrophotometric and chromatographic methods. Furthermore, the assessment of the phenolic profile evidenced individual compounds in the distinct cultivars, so as their variations in response to the fungal infection.  相似文献   
53.
54.
Journal of Solid State Electrochemistry - In order to meet the growing energy demand, it is of great significance to develop high-performance electrochemical energy storage materials. In this...  相似文献   
55.
Li  Baixue  Li  Zhen  You  Kai  Qin  Anjun  Tang  Ben Zhong 《中国科学:化学(英文版)》2022,65(4):771-777
Science China Chemistry - Secrecy has received tremendous attention in modern information society. Innovative polymer-based fluorescent materials with multiple mode emission are quite desirable to...  相似文献   
56.
57.
Cyclic organic amines are emerging as excellent building blocks to assemble organic–inorganic hybrid phase transition materials due to their flexible cyclic structure. Here, we have assembled a 1D organic-inorganic hybrid dielectric material C5H6NOPbBr3 ( 1 ) by alloying the cyclic organic amine 3-hydroxypyridine. 1 displays a remarkable switchable dielectric response induced by an order-disorder transformation of the organic moiety, this transformation behaviour is confirmed by DSC and Hirshfeld surface measurements. More interestingly, 1 has a narrowband emission (FWHM=4.64 nm) at 590 nm; FWHM is a major quality figure for narrowband photodetectors. In addition, 1 exhibits semiconducting properties with an indirect bandgap of 2.78 eV by the analysis of the UV-Vis absorption results.  相似文献   
58.
Alam  Nur  Tong  Li  He  Zhibin  Tang  Ruihua  Ahsan  Laboni  Ni  Yonghao 《Cellulose (London, England)》2021,28(13):8641-8651
Cellulose - Lateral flow assay (LFA) is an important point-of-care (POC) test platform due to the associated portability, on-site testing, and low cost for diagnosis of pathogen infections and...  相似文献   
59.
The recent development of selective oxidation of aromatic sulfides with molecular oxygen was highlighted. The sulfoxides and sulfones could be obtained by simply switching the reaction media, i.e., bis(2-butoxyethyl)ether (BBE) or poly(ethylene glycol)dimethyl ether (PEGDME). The application of the high-boiling-point polyether as an initiator and green media can eliminate the need of large quantities of additives and volatile solvents. This strategy represents an economic and eco-friendly method that could find potential applications.  相似文献   
60.
We studied on the structural requirement of C11b chirality of tetrabenazine (TBZ) analogs as vesicular monoamine transporter 2 (VMAT2) ligands. TBZ analogs (2, 6a, 6b) and 18F-radiolabeled [18F]6a and [18F]6b with eliminated C11b chirality were synthesized and characterized. Competition studies demonstrated that 2, 6a and 6b displayed much lower in vivo VMAT2 bindings than TBZ. MicroPET imaging studies of [18F]6a and [18F]6b showed negligible accumulation in VMAT2-enriched regions as compared with the known VMAT2 ligand 18F-FP-(+)-DTBZ. These results suggest that C11b chirality of TBZ analogs is essential for in vivo VMAT2 binding bioactivity.  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