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   176540篇
  免费   18445篇
  国内免费   11012篇
电工技术   14629篇
技术理论   4篇
综合类   14689篇
化学工业   24701篇
金属工艺   10889篇
机械仪表   11860篇
建筑科学   14865篇
矿业工程   6007篇
能源动力   5281篇
轻工业   13427篇
水利工程   4376篇
石油天然气   8971篇
武器工业   2058篇
无线电   21502篇
一般工业技术   17820篇
冶金工业   7086篇
原子能技术   1979篇
自动化技术   25853篇
  2024年   902篇
  2023年   2898篇
  2022年   5840篇
  2021年   7960篇
  2020年   6028篇
  2019年   4669篇
  2018年   5184篇
  2017年   6165篇
  2016年   5330篇
  2015年   7963篇
  2014年   9978篇
  2013年   11846篇
  2012年   13747篇
  2011年   14309篇
  2010年   13257篇
  2009年   12480篇
  2008年   12248篇
  2007年   11650篇
  2006年   10572篇
  2005年   8296篇
  2004年   5760篇
  2003年   4878篇
  2002年   4662篇
  2001年   4118篇
  2000年   3324篇
  1999年   2710篇
  1998年   1754篇
  1997年   1419篇
  1996年   1327篇
  1995年   1141篇
  1994年   935篇
  1993年   579篇
  1992年   471篇
  1991年   344篇
  1990年   269篇
  1989年   231篇
  1988年   160篇
  1987年   104篇
  1986年   97篇
  1985年   46篇
  1984年   39篇
  1983年   26篇
  1982年   35篇
  1981年   41篇
  1980年   44篇
  1979年   25篇
  1977年   10篇
  1976年   11篇
  1959年   10篇
  1951年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Wei  Mengnan  Ban  Boyuan  Li  Jingwei  Sun  Jifei  Li  Feifei  Jiang  Xuesong  Chen  Jian 《SILICON》2020,12(2):327-338
Silicon - A novel green cationic surfactant Poly (propylene glycol) bis (2-aminopropyl ether) (PEA) with multiple amine groups was utilized as a collector for flotation separation of quartz from...  相似文献   
12.
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients.  相似文献   
13.
14.
15.
Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications.  相似文献   
16.
本文据国内矫直机的使用情况,提出完善弯辊功能,解决辊缝标定清零及运行中的问题,提升轧钢厂运行效率与产品质量。  相似文献   
17.
18.
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes.  相似文献   
19.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view.  相似文献   
20.
Wei  LingNan  Wang  ZhenHua  Zhang  ZhiDong  Liu  Chieh-Wen  Gao  Xuan P. A. 《Nano Research》2020,13(5):1332-1338
Nano Research - We report the composition and back-gate voltage tuned transport properties of ternary compound Bi2(Te1−xSex)3 nanowires synthesized by chemical vapor deposition (CVD). It is...  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