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   46315篇
  免费   1473篇
  国内免费   199篇
电工技术   496篇
综合类   30篇
化学工业   7459篇
金属工艺   1154篇
机械仪表   792篇
建筑科学   2018篇
矿业工程   114篇
能源动力   1091篇
轻工业   2906篇
水利工程   451篇
石油天然气   125篇
武器工业   5篇
无线电   2790篇
一般工业技术   6251篇
冶金工业   6724篇
原子能技术   389篇
自动化技术   15192篇
  2023年   215篇
  2022年   432篇
  2021年   684篇
  2020年   463篇
  2019年   630篇
  2018年   786篇
  2017年   697篇
  2016年   837篇
  2015年   762篇
  2014年   1246篇
  2013年   2542篇
  2012年   2433篇
  2011年   5120篇
  2010年   2772篇
  2009年   2533篇
  2008年   2461篇
  2007年   2352篇
  2006年   2030篇
  2005年   2002篇
  2004年   1687篇
  2003年   1694篇
  2002年   1323篇
  2001年   709篇
  2000年   558篇
  1999年   623篇
  1998年   694篇
  1997年   604篇
  1996年   580篇
  1995年   583篇
  1994年   538篇
  1993年   518篇
  1992年   508篇
  1991年   300篇
  1990年   431篇
  1989年   397篇
  1988年   328篇
  1987年   362篇
  1986年   321篇
  1985年   427篇
  1984年   456篇
  1983年   329篇
  1982年   301篇
  1981年   289篇
  1980年   269篇
  1979年   271篇
  1978年   249篇
  1977年   229篇
  1976年   209篇
  1975年   197篇
  1974年   173篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Photovoltaic (PV) solar energy installations are growing all over the world as a promising renewable alternative to generate electricity. However, many studies have highlighted some drawbacks associated with the installation and operation of conventional solar energy power plants. Thus, floating photovoltaic (FPV) systems have been emerging as a new concept in solar energy to lessen negative environmental impacts caused by allocation of conventional PV facilities. This paper is an overview of the potential negative and positive environmental impacts caused by photovoltaic systems with particular interest on large-scale conventional and floating photovoltaic. This study addresses and compares the impacts at all phases of project implementation, which covers planning, construction, and operation and decommissioning, focusing on ambient located in the tropics. The overall impacts associated with project allocation such as deforestation (for the project implementation and site accessing), bird mortality, erosion, runoff, and change in microclimate are expected to have higher magnitudes for the implementation of conventional PV facilities. The results highlight advantages of FPV over conventional PV during the operational and decommissioning phases as well. Though, further studies are required to assess both qualitative and quantitative aspects of installations in similar areas.  相似文献   
992.
ABSTRACT

A primary goal for human-autonomy integration (HAI) is to balance the strengths of human and autonomy in order to achieve performance objectives more efficiently and robustly than either the human or autonomous agents would independently. This paper proposes the Privileged Sensing Framework (PSF) as a novel approach to HAI. This approach is based on the concept of dynamically ‘privileging’ information during the process of integration by dynamically bestowing special rights based on the characteristics of each individual agent, the task context, and the performance goals. The proposed framework is tested through a series of simulation experiments that provide a clear demonstration of increased accuracy and throughput of human-autonomy performance. These proof-of-concept simulations provide initial evidence of the utility of the PSF. Continued development of this approach has the potential to revolutionise capabilities of multi-agent cooperative teams across a broad range of applications.  相似文献   
993.
994.
Low‐level laser therapy (LLLT) is a form of phototherapy used to promote cell proliferation. This study investigates the potential role of LLLT in cellular proliferation of human monocytic leukaemia cells Tamm‐Horsfall Protein 1 (THP‐1) under in vitro conditions. Cells were irradiated with an 850 nm diode laser and exposed to doses ranging from 0 to 26.8 J/cm2. After irradiation, cells were incubated for 12 and 24 h to allow time for proliferation. Comet assay was conducted to evaluate genotoxicity of the irradiated cells. Trypan blue was used to estimate cytotoxicity, which peaked at the highest dose as expected. Preliminary results suggest that cell counts increase at low doses, whereas a decrease in cell number at high doses was noted compared with controls. Comet assay showed no significant difference between irradiated and non‐irradiated cells at low doses. In contrast, DNA damage increased at doses ≥8.9 J/cm2 and was comparable with the 100 μM hydrogen peroxide positive control at the highest fluence. It could be concluded that LLLT has the ability to stimulate the THP‐1 cell line to proliferate if supplied with the correct energy and dose.Inspec keywords: photodynamic therapy, laser applications in medicine, cellular effects of radiation, biological effects of laser radiation, DNA, diseases, semiconductor lasersOther keywords: photo‐stimulatory effect, LLLT, human monocytic leukaemia cells, cell proliferation rate, low‐level laser therapy, phototherapy, THP‐1, Comet assay, Trypan blue, cytotoxicity, DNA damage, wavelength 850 nm, time 12 h, time 24 h  相似文献   
995.
Zan  Wu  Zhang  Qiaochu  Xu  Hu  Liao  Fuyou  Guo  Zhongxun  Deng  Jianan  Wan  Jing  Zhu  Hao  Chen  Lin  Sun  Qingqing  Ding  Shijin  Zhou  Peng  Bao  Wenzhong  Zhang  David Wei 《Nano Research》2018,11(7):3739-3745
Nano Research - A spin-coating method was applied to obtain thinner and smoother PEO/LiClO4 polymer electrolyte films (EFs) with a lower level of crystallization than those obtained using a...  相似文献   
996.
There is a growing interest in the development of microelectronics that can perform reliably and robustly at temperatures above 300 °C. Such devices require stable thermal properties, low thermal drift, and thermal cycling resistance. Conventional hybrid circuit technology demonstrates high-temperature packages, but the high costs and lead time are significant drawbacks. In contrast, additive manufacturing processes, including aerosol jet printing (AJP), offer cost and time benefits, as well as 3D structures and embedded features. However, the properties and reliability of additive packaging materials at extreme temperatures are not well known. Herein, the reliability at temperatures up to 750 °C in terms of electrical performance and mechanical strength of aerosol jet printed gold thick films onto ceramic substrates are assessed. Thermal coefficient of resistance of printed gold films is measured. The electrical resistance stability and leakage current of printed gold structures are also characterized during over 100 h of aging at temperatures up to 750 °C. Finally, the mechanical adhesion strength of the printed gold films is evaluated after aging for 100 h at temperatures up to 750 °C. The adhesion of the printed gold to the ceramic substrates remains high after aging, very stable resistances and minimal leakage currents have been observed.  相似文献   
997.
Software engineering programmes are not computer science programmes   总被引:1,自引:1,他引:0  
Programmes in Software Engineering have become a source of contention in many universities. Some Computer Science departments, many of which have used that phrase to describe individual courses for decades, claim software engineering as part of their discipline. However, Engineering faculties claim Software Engineering as a new speciality in the family of engineering disciplines. This paper discusses the differences between traditional computer science programmes and most engineering programmes and argues that we need programmes that follow the traditional engineering approach to professional education and educate engineers whose speciality within engineering is software construction. One such programme is described.  相似文献   
998.
999.
In this paper, a unified approach to the design of a nonlinear excitation controller/power system stabilizer for a synchronous generator/infinite bus power system is presented. The approach is based on a form of state feedback linearization, known as input–output feedback linearization, which provides an exact semi-global state transformation that is valid for a large class of operating points of the power system. With this transformation, the terminal voltage becomes a linear function of the control input. The excitation controller/power system stabilizer is then synthesized by using linear controller design techniques. The controller is proven to provide small signal stability and to provide local asymptotic tracking of admissible constant reference signals for a large class of operating points. A procedure is given to tune the controller gains to provide significant damping of the power angle oscillations.  相似文献   
1000.
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