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   239666篇
  免费   2127篇
  国内免费   574篇
电工技术   3757篇
综合类   191篇
化学工业   35916篇
金属工艺   8711篇
机械仪表   6752篇
建筑科学   6008篇
矿业工程   1374篇
能源动力   5880篇
轻工业   22399篇
水利工程   2705篇
石油天然气   4201篇
武器工业   12篇
无线电   25359篇
一般工业技术   46813篇
冶金工业   45948篇
原子能技术   5252篇
自动化技术   21089篇
  2021年   2528篇
  2020年   2014篇
  2019年   2338篇
  2018年   3972篇
  2017年   4047篇
  2016年   4267篇
  2015年   2836篇
  2014年   4404篇
  2013年   11467篇
  2012年   7234篇
  2011年   9000篇
  2010年   7175篇
  2009年   7755篇
  2008年   8071篇
  2007年   7942篇
  2006年   6658篇
  2005年   6143篇
  2004年   5843篇
  2003年   5638篇
  2002年   5190篇
  2001年   5083篇
  2000年   4988篇
  1999年   5259篇
  1998年   14135篇
  1997年   9756篇
  1996年   7496篇
  1995年   5317篇
  1994年   4822篇
  1993年   4605篇
  1992年   3412篇
  1991年   3260篇
  1990年   3074篇
  1989年   3140篇
  1988年   3004篇
  1987年   2549篇
  1986年   2470篇
  1985年   2896篇
  1984年   2666篇
  1983年   2456篇
  1982年   2230篇
  1981年   2347篇
  1980年   2160篇
  1979年   2241篇
  1978年   2225篇
  1977年   2534篇
  1976年   3554篇
  1975年   1913篇
  1974年   1829篇
  1973年   1847篇
  1972年   1482篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
81.
Until now, attention has been focused solely in the drying of squid mantle from an experimental point of view, neglecting the transport phenomenon studies of water in squid muscle. This work studies the drying of squid mantle (Loligo brasiliensis), previously salted and smoked by liquid smoking (hickory extract), using a tubular dryer in closed cycle with a silicagel fixed bed in series. The mass transfer phenomenon during drying was studied, based on the Fick's second law, with the effective diffusivity supposed constant, which enabled an analytical solution to the problem. The drying curve calculated with the resulting equation was compared with experimental data. The model was applied to a hollow cylinder geometry (round squid mantle), with its internal surface isolated from the drying environment by a plastic film. The latter was given a tubular form and introduced inside the mantle cavity (impervious wall boundary condition).  相似文献   
82.
We report on the fabrication and characterization of high-speed p-type modulation-doped field-effect transistors (MODFETs) with 0.7-μm and 1-μm gate-lengths having unity current-gain cut-off frequencies (fT) of 9.5 GHz and 5.3 GHz, respectively. The devices were fabricated on a high hole mobility SiGe heterostructure grown by ultra-high-vacuum chemical vapor deposition (UHV-CVD). The dc maximum extrinsic transconductance (gm) is 105 mS/mm (205 mS/mm) at room temperature (77 K) for the 0.7-μm gate length devices. The fabricated devices show good pinch-off characteristics and have a very low gate leakage current of a few μA/mm at room temperature and a few nA/mm at 77 K  相似文献   
83.
Softening behaviour of 50 CrV4 steel on thermomechanical treatment Determination of static softening of austenite on thermomechanical treatment of steel by rolling. Analysed was the development of the austenite structure and influencing the work softening processes depending on the deformation-temperature-time mode. The static softening processes were modelled mathematically by using Avrami's relationships.  相似文献   
84.
85.
Analysis of a complexity-based pruning scheme for classification trees   总被引:2,自引:0,他引:2  
A complexity-based pruning procedure for classification trees is described, and bounds on its finite sample performance are established. The procedure selects a subtree of a (possibly random) initial tree in order to minimize a complexity penalized measure of empirical risk. The complexity assigned to a subtree is proportional to the square root of its size. Two cases are considered. In the first, the growing and pruning data sets are identical, and in the second, they are independent Using the performance bound, the Bayes risk consistency of pruned trees obtained via the procedure is established when the sequence of initial trees satisfies suitable geometric and structural constraints. The pruning method and its analysis are motivated by work on adaptive model selection using complexity regularization.  相似文献   
86.
A menu-driven interactive graphics software package has been developed for use as an instructional aid for the electric machines course in the electrical engineering curriculum. The main purpose of this tool is to give the students a clearer understanding of the basics of the operation of rotating electric machines. The animation program was developed for displaying live and rotating diagrams depicting different modes of operation of synchronous generators. Different parts are identified with different colors. The interaction of the magnetic poles on the stator and on the rotor, and the relative spatial positions and time variations of the magnetic and electric quantities are demonstrated through moving images. The software features are described  相似文献   
87.
88.
89.
The authors present a successful model of industry/university cooperation in establishing a strong power system curriculum in both the graduate and undergraduate level. Numerous long-term and short-term research projects have been developed to satisfy the university mission and to tackle challenging problems facing the power industry. A unique structure for the Clemson University Electric Power Research Association (CUEPRA) has been established to promote electric power system research and to meet the need for a working communication link between the power industry and the academic community. The power industries involvements in the power program at Clemson University and the strategic improvements that have been accomplished in research and education are outlined  相似文献   
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