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   28109篇
  免费   2435篇
  国内免费   1430篇
电工技术   1748篇
技术理论   1篇
综合类   1989篇
化学工业   4652篇
金属工艺   1459篇
机械仪表   1791篇
建筑科学   2175篇
矿业工程   911篇
能源动力   770篇
轻工业   2491篇
水利工程   543篇
石油天然气   1810篇
武器工业   206篇
无线电   2800篇
一般工业技术   2985篇
冶金工业   1320篇
原子能技术   320篇
自动化技术   4003篇
  2024年   144篇
  2023年   508篇
  2022年   896篇
  2021年   1206篇
  2020年   871篇
  2019年   747篇
  2018年   849篇
  2017年   939篇
  2016年   829篇
  2015年   1115篇
  2014年   1484篇
  2013年   1801篇
  2012年   1875篇
  2011年   2147篇
  2010年   1836篇
  2009年   1770篇
  2008年   1789篇
  2007年   1617篇
  2006年   1543篇
  2005年   1384篇
  2004年   923篇
  2003年   758篇
  2002年   715篇
  2001年   625篇
  2000年   614篇
  1999年   584篇
  1998年   450篇
  1997年   413篇
  1996年   349篇
  1995年   287篇
  1994年   257篇
  1993年   170篇
  1992年   147篇
  1991年   83篇
  1990年   66篇
  1989年   38篇
  1988年   48篇
  1987年   28篇
  1986年   15篇
  1985年   7篇
  1984年   13篇
  1983年   8篇
  1982年   8篇
  1981年   7篇
  1980年   6篇
  1979年   2篇
  1959年   2篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Let G1 and G2 be two connected graphs. The Kronecker product G1×G2 has vertex set V(G1×G2)=V(G1V(G2) and the edge set . In this paper, we show that if G is a bipartite graph with κ(G)=δ(G), then G×Kn(n?3) is super-κ.  相似文献   
42.
43.
A system-level model with lumped parameters for a thermal flow sensor is presented. The model is built with 13 circuit cells consisting of thermal resistors and thermal capacitors in SPICE. The circuit cell originates from the heat conduction equation using the Finite Differential Method, including the 2-D thermal conduction cell, the convection cell, and the thermal capacity in the chip. Based on the thermal model of the flow sensor, the 2-D temperature distribution of the chip can be calculated with SPICE in both the constant power mode (CP) and constant temperature difference mode (CTD). As an example, the system level model of the thermal anemometer in the CTD mode was established in PSPICE. Wind tunnel test was carried out to verify the system model, and show a reasonable agreement with the simulation results, with an error less than 8%.  相似文献   
44.
讨论使用混合图对图像进行识别的连通性、相似性和可比性原则,并提出一种混合图结构的约化算法。通过可比性原则,对图像的混合图结构中复合节点用参考图像进行比较,计算出混合图复合节点在参考图像中的可能匹配和相似度,以此对混合图结构进行约化。为方便计算和阐述约化过程,使用单个属性,对混合图进行属性标记,把相似性比较简化为线性复杂度的排序和查询运算。结果显示,该方法切实可行。  相似文献   
45.
To deal with the planarization problem widely used in many applications including routing very-large-scale integration (VLSI) circuits, this paper points out that only when its vertices are arranged in some specific order in a line can a planar graph be embedded on a line without any cross connections or cross edges. Energy function is proposed to meet the need of embedding a graph on a single line and route it correctly. A Hopfield network is designed according to the proposed energy function for such embedding and routing. The advantage of the proposed method is that it not only can detect if a graph is a planar one or not, but also can embed a planar graph or the maximal planar subgraph of a non-planar graph on a single line. In addition, simulated annealing is employed for helping the network to escape from local minima during the running of the Hopfield network. Experiments of the proposed method and its comparison with some existent conventional methods were performed and the results indicate that the proposed method is of great feasibility and effectiveness especially for the planarization problem of large graphs.  相似文献   
46.
Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed using comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) on a series of agonists of thyroid hormone receptor beta (TRbeta), which may lead to safe therapies for non-thyroid disorders while avoiding the cardiac side effects. The reasonable q(2) (cross-validated) values 0.600 and 0.616 and non-cross-validated r(2) values of 0.974 and 0.974 were obtained for CoMFA and CoMSIA models for the training set compounds, respectively. The predictive ability of two models was validated using a test set of 12 molecules which gave predictive correlation coefficients (r(pred)(2)) of 0.688 and 0.674, respectively. The Lamarckian Genetic Algorithm (LGA) of AutoDock 4.0 was employed to explore the binding mode of the compound at the active site of TRbeta. The results not only lead to a better understanding of interactions between these agonists and the thyroid hormone receptor beta but also can provide us some useful information about the influence of structures on the activity which will be very useful for designing some new agonist with desired activity.  相似文献   
47.
The prototype of a CO2 sensor made of CuO–BaTiO3, which has capacitance sensitive effect, is designed based on the pn heterojunctions of CuO and BaTiO3 semiconductors. The preparation of BaTiO3 semiconductor powders is pointed out, using the coprecipitation and semiconducting techniques. The characteristic quantities relating to the capacitance sensitive effect of the sensor are studied systematically with the aid of a gas tester. A reasonable mechanism of the sensor is proposed.  相似文献   
48.
高速公路联网系统车道收费软件的设计与实现   总被引:1,自引:0,他引:1  
张明  舒勤  潘宏 《计算机工程》2001,27(12):130-131,134
通过对当前常用的车道收费软件的分析对比,提出了一种基于Mini Server战术的车道收费软件的体系结构,并就其实现技术及性能特点进行了详细的论述,还对Mini Server控制下多Agent通信策略等方面进行了较深入的描述。  相似文献   
49.
首先对CIMS进行了简述,然后介绍了某研究所科研生产的现状,最后提出某研究所实现CIMS的可能途径。  相似文献   
50.
Acoustic emission (AE) experiments have been performed on gas-saturated coal specimens under conventional triaxial compression. The AE characteristics were investigated for a methane gas flow through the coal specimen. One AE parameter, AE count, when normalized by the total count number was used to represent the damage evolution in the gassy coal. It is shown that this AE parameter is a reasonable indicator for damage occurring within the coal specimen since its envelope has almost the same shape as the complete stress–strain curve, except for a short time delay. In addition, the change in AE count is highly consistent with the change in coal permeability. Test results also show that methane containing coal emits a small number of AE events before entering the yield stage. AE activity gradually increases during the yield process up to the peak stress. The lowest permeability corresponds to the highest AE activity, implying failure will soon occur. An AE based constitutive model was constructed and the theoretical results agree well with those of experiments.  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