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   261944篇
  免费   4820篇
  国内免费   1795篇
电工技术   5424篇
技术理论   5篇
综合类   1172篇
化学工业   42578篇
金属工艺   11027篇
机械仪表   7782篇
建筑科学   6683篇
矿业工程   1661篇
能源动力   5639篇
轻工业   26092篇
水利工程   2923篇
石油天然气   5957篇
武器工业   243篇
无线电   27827篇
一般工业技术   49503篇
冶金工业   47268篇
原子能技术   5623篇
自动化技术   21152篇
  2021年   2620篇
  2019年   2170篇
  2018年   3449篇
  2017年   3419篇
  2016年   3766篇
  2015年   2879篇
  2014年   4681篇
  2013年   11493篇
  2012年   7808篇
  2011年   10373篇
  2010年   8222篇
  2009年   8772篇
  2008年   9585篇
  2007年   9675篇
  2006年   8490篇
  2005年   7431篇
  2004年   6697篇
  2003年   6246篇
  2002年   6239篇
  2001年   6340篇
  2000年   5934篇
  1999年   5900篇
  1998年   12881篇
  1997年   9547篇
  1996年   7285篇
  1995年   5541篇
  1994年   5097篇
  1993年   4958篇
  1992年   3948篇
  1991年   3760篇
  1990年   3826篇
  1989年   3774篇
  1988年   3531篇
  1987年   3022篇
  1986年   3053篇
  1985年   3408篇
  1984年   3321篇
  1983年   3074篇
  1982年   2700篇
  1981年   2905篇
  1980年   2643篇
  1979年   2844篇
  1978年   2738篇
  1977年   2844篇
  1976年   3694篇
  1975年   2459篇
  1974年   2291篇
  1973年   2320篇
  1972年   1981篇
  1971年   1785篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...  相似文献   
82.
Protection of Metals and Physical Chemistry of Surfaces - In this work, a universal sorbent has been obtained that works according to the mechanisms of chemisorption and adsorption by impregnating...  相似文献   
83.
Water Resources Management - Public awareness of water quality concerns has increased since the Flint, MI crisis, but knowledge about water resources management remains low. Consequently,...  相似文献   
84.
Microsystem Technologies - The strategy for analysis of noise generated in the analog circuit is presented here. Further, methodology for optimization of noise to improve the performance of the...  相似文献   
85.
Sarcopenia is the loss of skeletal muscle mass and function with advancing age. It involves both complex genetic and modifiable risk factors, such as lack of exercise, malnutrition and reduced neurological drive. Cognitive decline refers to diminished or impaired mental and/or intellectual functioning. Contracting skeletal muscle is a major source of neurotrophic factors, including brain-derived neurotrophic factor, which regulate synapses in the brain. Furthermore, skeletal muscle activity has important immune and redox effects that modify brain function and reduce muscle catabolism. The identification of common risk factors and underlying mechanisms for sarcopenia and cognition may allow the development of targeted interventions that slow or reverse sarcopenia and also certain forms of cognitive decline. However, the links between cognition and skeletal muscle have not been elucidated fully. This review provides a critical appraisal of the literature on the relationship between skeletal muscle health and cognition. The literature suggests that sarcopenia and cognitive decline share pathophysiological pathways. Ageing plays a role in both skeletal muscle deterioration and cognitive decline. Furthermore, lifestyle risk factors, such as physical inactivity, poor diet and smoking, are common to both disorders, so their potential role in the muscle–brain relationship warrants investigation.  相似文献   
86.
A series of 2-phenyloxazoles bearing an amide group at position 4 were designed and synthesized for evaluation as potential inhibitors of human recombinant monoamine oxidases (hrMAOs). Results of kinetics experiments demonstrated that all compounds behave as competitive MAO inhibitors, with good selectivity toward the MAO-B isoform. The most potent and selective derivatives are characterized by inhibition constant (Ki) values in the sub-micromolar range and a good selectivity index (Ki MAO-A/Ki MAO-B>50). Some derivatives were also found to be able to inhibit MAO activity in nerve growth factor (NGF)-differentiated PC12 cells, taken as a model of neuronal cells. In particular, 2-(2-hydroxyphenyl)-N-phenyloxazole-4-carboxamide (compound 4 a ) may be a promising new scaffold, exerting the highest selectivity and inhibitory effect toward MAOs in NGF-differentiated PC12 cell lysates, without compromising cell viability. Molecular docking analysis allowed a rationalization of the experimentally observed binding affinity and selectivity.  相似文献   
87.
Ji  Chengang  Yang  Chenying  Shen  Weidong  Lee  Kyu-Tae  Zhang  Yueguang  Liu  Xu  Guo  L. Jay 《Nano Research》2019,12(3):543-548

We present a new scheme for visibly-opaque but near-infrared-transmitting filters involving 7 layers based on one-dimensional ternary photonic crystals, with capabilities in reaching nearly 100% transmission efficiency in the near-infrared region. Different decorative reflection colors can be created by adding additional three layers while maintaining the near-infrared transmission performance. In addition, our proposed structural colors show great angular insensitivity up to ±60° for both transverse electric and transverse magnetic polarizations, which are highly desired in various fields. The facile strategy described here involves a simple deposition method for the fabrication, thereby having great potential in diverse applications such as image sensors, anti-counterfeit tag, and optical measurement systems.

  相似文献   
88.
89.
90.
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