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   5165篇
  免费   384篇
  国内免费   107篇
电工技术   136篇
综合类   131篇
化学工业   1351篇
金属工艺   208篇
机械仪表   248篇
建筑科学   252篇
矿业工程   66篇
能源动力   248篇
轻工业   564篇
水利工程   74篇
石油天然气   145篇
武器工业   22篇
无线电   621篇
一般工业技术   742篇
冶金工业   256篇
原子能技术   34篇
自动化技术   558篇
  2024年   25篇
  2023年   76篇
  2022年   127篇
  2021年   228篇
  2020年   163篇
  2019年   194篇
  2018年   209篇
  2017年   179篇
  2016年   196篇
  2015年   201篇
  2014年   254篇
  2013年   462篇
  2012年   304篇
  2011年   310篇
  2010年   260篇
  2009年   279篇
  2008年   268篇
  2007年   188篇
  2006年   212篇
  2005年   149篇
  2004年   123篇
  2003年   119篇
  2002年   116篇
  2001年   110篇
  2000年   105篇
  1999年   105篇
  1998年   100篇
  1997年   93篇
  1996年   72篇
  1995年   77篇
  1994年   53篇
  1993年   25篇
  1992年   37篇
  1991年   26篇
  1990年   19篇
  1989年   16篇
  1988年   14篇
  1987年   16篇
  1986年   12篇
  1985年   19篇
  1984年   11篇
  1983年   14篇
  1982年   8篇
  1981年   10篇
  1980年   16篇
  1979年   10篇
  1976年   12篇
  1975年   5篇
  1973年   4篇
  1972年   6篇
排序方式: 共有5656条查询结果,搜索用时 218 毫秒
31.
Fuzzy rule-based systems have been very popular in many engineering applications. In mineral engineering, fuzzy rules are normally constructed using some fuzzy rule extraction techniques to establish the determination model in predicting the d50c of hydrocyclones. However, when generating fuzzy rules from the available information, it may result in a sparse fuzzy rule base. The use of more than one input variable is also common in hydrocyclone data analysis. This paper examines the application of fuzzy interpolation to resolve the problems using sparse fuzzy rule bases, and to perform analysis of fuzzy interpolation in multidimensional input spaces.  相似文献   
32.
给出了单齿泵削角的优化模型与计算实例,并对理论设计与实验进行了比较分析。  相似文献   
33.
A generalized parameter-level statistical model, called statistical MOS (SMOS), capable of generating statistically significant model decks from intra- and inter-die parameter statistics is described. Calculated model decks preserve the inherent correlations between model parameters while accounting for the dependence of parameter variance on device separation distance and device area. Using a Monte Carlo approach to parameter sampling, circuit output means and standard deviations can be simulated. Incorporated in a CAD environment, these modeling algorithms will provide the analog circuit designer with a method to determine the effect of both circuit layout and device sizing on circuit output variance. Test chips have been fabricated from two different fabrication processes to extract statistical information required by the model. Experimental and simulation results for two analog subcircuits are compared to verify the statistical modeling algorithms  相似文献   
34.
The LiPO3-Y(PO3)3 system has been studied for the first time. Microdifferential thermal analysis (μ-DTA), infrared spectroscopy (IR) and X-ray diffraction were used to investigate the liquidus and solidus relations. The only new compound observed within this system is LiY(PO3)4, melting incongruently at 1104 K. An eutectic appears at 4±1 mol% Y(PO3)3 at 933 K. LiY(PO3)4 crystallizes in the monoclinic system C2/c with a unit cell: a=16.201(4) Å, b=7.013(2) Å, c=9.573(2) Å, β=125.589(9)°, Z=4 and V=884.5 Å3, which is isostructural to LiNd(PO3)4. The infrared absorption spectrum indicates that this salt is a chain polyphosphate.  相似文献   
35.
This paper presents a method of calculating the insulating safety distances for hot-line working robots at high voltage when dielectric is adulterated with conducts. Also, finite element method is adopted to calculate the electric field strength to find whether it is beyond the critical. The above methods have been applied to analyze the insulating safety of the robot for hot-line sweeping post insulators in a 220 KV substation. They have also been testified by experimentations.  相似文献   
36.
“十一五”规划重点突出了“科学的发展观”,“自主创新”与“节约型循环型经济增长”等概念,印刷业的环保、节约资源自然也就成了议论热点。然而宏观层面的问题尽管是头等大事,但对业主或厂主们来说毕竟还是缺乏饥寒忧患的迫切感。老实说,目前印企老总们最关心的还是业务、工价和盈利这老三样。如果同时召开一个环保问题和一个开拓业务问题的会议,前者的参与者肯定没有后者踊跃。  相似文献   
37.
Design of a CMOS 18th-order IF (intermediate frequency) bandpass filter for integrated low-IF Bluetooth receivers is presented. The centre frequency and bandwidth of the filter are 3 and 1 MHz, respectively. The proposed filter is based on unity gain fully differential voltage buffers and provides efficient, low power and a small area design solution. The filter, including its automatic tuning circuit, occupies an area of 0.6 mm2 in a standard 0.5 mum-CMOS chip. Experimental results show that the filter satisfies the selectivity and dynamic range requirements of Bluetooth while operating from a total supply current of 0.9 mA  相似文献   
38.
Supply chain management has offered a way to improve the industrial environment becomes more competitive. While, the commonly seen methodologies may be effective in solving the production–distribution problem only from supplier- or customer-oriented consideration, those cannot present the interactive relationship between upstream and downstream enterprises. In the competitive semiconductor industry environment, considering the viewpoints of the supplier and consumer simultaneously is particularly required, because multiple manufacturing and demanding steps are performed at separate situations, concurrently. In this paper, we propose an interaction-oriented approach, which bases on the analytic hierarchy process (AHP) methodology and proportional rule, to solve the semiconductor distribution problem with multiple quantitative and qualitative criteria. The developed approach gives an expected satisfaction for the all participators of the whole chain while the cooperative information is shared perfectly and effectively. Analysis results demonstrate the proposed methodology is efficient and effective through a real world case study.  相似文献   
39.
40.
The authors report on the fabrication and the resultant device characteristics of the first 0.25-μm gate-length field-effect transistor based on n-type modulation-doped Si/SiGe. Prepared using ultrahigh vacuum/chemical vapor deposition (UHV/CVD), the mobility and electron sheet charge density in the strained Si channel are 1500 (9500) cm2/V-s and 2.5×1012 (1.5×1012 ) cm-2 at 300 K (77 K). At 77 K, the devices have a current and transconductance of 325 mA/mm and 600 mS/mm, respectively. These values far exceed those found in Si MESFETs and are comparable to the best results achieved in GaAs/AlGaAs modulation-doped transistors  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