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   294940篇
  免费   10811篇
  国内免费   4641篇
电工技术   9230篇
技术理论   2篇
综合类   5902篇
化学工业   44303篇
金属工艺   13049篇
机械仪表   11496篇
建筑科学   11743篇
矿业工程   3135篇
能源动力   8056篇
轻工业   25248篇
水利工程   4196篇
石油天然气   7884篇
武器工业   684篇
无线电   35176篇
一般工业技术   52349篇
冶金工业   42294篇
原子能技术   6157篇
自动化技术   29488篇
  2022年   3380篇
  2021年   5438篇
  2020年   3793篇
  2019年   3838篇
  2018年   5149篇
  2017年   5635篇
  2016年   5470篇
  2015年   5335篇
  2014年   7728篇
  2013年   15088篇
  2012年   11539篇
  2011年   14287篇
  2010年   11762篇
  2009年   12359篇
  2008年   12328篇
  2007年   12089篇
  2006年   10892篇
  2005年   9537篇
  2004年   7960篇
  2003年   7337篇
  2002年   6996篇
  2001年   6742篇
  2000年   6555篇
  1999年   6719篇
  1998年   13405篇
  1997年   9829篇
  1996年   7892篇
  1995年   5908篇
  1994年   5224篇
  1993年   4863篇
  1992年   3833篇
  1991年   3535篇
  1990年   3257篇
  1989年   3260篇
  1988年   3086篇
  1987年   2583篇
  1986年   2463篇
  1985年   2859篇
  1984年   2614篇
  1983年   2427篇
  1982年   2162篇
  1981年   2273篇
  1980年   2092篇
  1979年   2166篇
  1978年   2157篇
  1977年   2410篇
  1976年   3262篇
  1975年   1853篇
  1974年   1779篇
  1973年   1796篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Morozov  Yu. D.  Pemov  I. F.  Matrosov  M. Yu.  Zin’ko  B. F. 《Metallurgist》2020,63(9-10):933-950
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of...  相似文献   
72.
Russian Journal of Non-Ferrous Metals - This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate...  相似文献   
73.
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   
74.
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   
75.
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   
76.
77.
78.
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   
79.
80.
Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity.  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