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   90364篇
  免费   7917篇
  国内免费   4080篇
电工技术   5686篇
技术理论   2篇
综合类   5776篇
化学工业   14014篇
金属工艺   4953篇
机械仪表   5216篇
建筑科学   6721篇
矿业工程   1853篇
能源动力   2647篇
轻工业   7091篇
水利工程   1811篇
石油天然气   3877篇
武器工业   675篇
无线电   12043篇
一般工业技术   11650篇
冶金工业   4617篇
原子能技术   1029篇
自动化技术   12700篇
  2024年   365篇
  2023年   1372篇
  2022年   2574篇
  2021年   3556篇
  2020年   2502篇
  2019年   2105篇
  2018年   2358篇
  2017年   2802篇
  2016年   2455篇
  2015年   3396篇
  2014年   4445篇
  2013年   5665篇
  2012年   6041篇
  2011年   6756篇
  2010年   5857篇
  2009年   5651篇
  2008年   5586篇
  2007年   5348篇
  2006年   5123篇
  2005年   4178篇
  2004年   2844篇
  2003年   2349篇
  2002年   2370篇
  2001年   2026篇
  2000年   1913篇
  1999年   1940篇
  1998年   1827篇
  1997年   1576篇
  1996年   1411篇
  1995年   1185篇
  1994年   923篇
  1993年   761篇
  1992年   607篇
  1991年   462篇
  1990年   385篇
  1989年   298篇
  1988年   252篇
  1987年   182篇
  1986年   152篇
  1985年   139篇
  1984年   100篇
  1983年   75篇
  1982年   68篇
  1981年   59篇
  1980年   51篇
  1979年   35篇
  1978年   32篇
  1977年   32篇
  1976年   54篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
分包商安全能力不足以及总包商安全管理薄弱,已成为导致工程建设项目事故多发的重要原因。将分包商的安全管理有效纳入到总承包商的安全管理体系内,做好分包商的安全管理,对提高总承包商的安全绩效、确保施工安全,具有极其重要的现实意义。从总承包商和分包商两个角度,研究分析分包安全管理中存在的问题及原因,得出分包安全管理各种问题的根源主要是经济利益,管理源头在总承包单位,站在总承包商的视角提出加强分包商安全管理的建议。  相似文献   
32.
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research.  相似文献   
33.
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   
34.
35.
Ionomics is a novel multidisciplinary field that uses advanced techniques to investigate the composition and distribution of all minerals and trace elements in a living organism and their variations under diverse physiological and pathological conditions. It involves both high-throughput elemental profiling technologies and bioinformatic methods, providing opportunities to study the molecular mechanism underlying the metabolism, homeostasis, and cross-talk of these elements. While much effort has been made in exploring the ionomic traits relating to plant physiology and nutrition, the use of ionomics in the research of serious diseases is still in progress. In recent years, a number of ionomic studies have been carried out for a variety of complex diseases, which offer theoretical and practical insights into the etiology, early diagnosis, prognosis, and therapy of them. This review aims to give an overview of recent applications of ionomics in the study of complex diseases and discuss the latest advances and future trends in this area. Overall, disease ionomics may provide substantial information for systematic understanding of the properties of the elements and the dynamic network of elements involved in the onset and development of diseases.  相似文献   
36.
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry  相似文献   
37.
38.
39.
40.
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