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   53920篇
  免费   4293篇
  国内免费   2007篇
电工技术   2816篇
技术理论   5篇
综合类   3027篇
化学工业   9274篇
金属工艺   3284篇
机械仪表   3272篇
建筑科学   3885篇
矿业工程   1758篇
能源动力   1702篇
轻工业   3895篇
水利工程   874篇
石油天然气   3761篇
武器工业   404篇
无线电   5807篇
一般工业技术   6415篇
冶金工业   2962篇
原子能技术   660篇
自动化技术   6419篇
  2024年   192篇
  2023年   870篇
  2022年   1409篇
  2021年   2262篇
  2020年   1679篇
  2019年   1450篇
  2018年   1650篇
  2017年   1805篇
  2016年   1594篇
  2015年   2121篇
  2014年   2712篇
  2013年   3145篇
  2012年   3360篇
  2011年   3675篇
  2010年   3255篇
  2009年   2931篇
  2008年   2854篇
  2007年   2770篇
  2006年   2949篇
  2005年   2504篇
  2004年   1570篇
  2003年   1372篇
  2002年   1300篇
  2001年   1026篇
  2000年   1221篇
  1999年   1509篇
  1998年   1186篇
  1997年   1018篇
  1996年   1024篇
  1995年   884篇
  1994年   704篇
  1993年   463篇
  1992年   375篇
  1991年   293篇
  1990年   237篇
  1989年   199篇
  1988年   172篇
  1987年   106篇
  1986年   90篇
  1985年   62篇
  1984年   52篇
  1983年   36篇
  1982年   32篇
  1981年   29篇
  1980年   17篇
  1979年   7篇
  1978年   7篇
  1977年   10篇
  1976年   14篇
  1975年   4篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
碱法造纸黑液驱油研究   总被引:2,自引:0,他引:2  
马宝岐  黄风林 《油田化学》1994,11(3):226-229
在玻璃细珠充填柱人造岩心模型上进行了碱法造纸黑液驱替稠油的实验研究,考察了稠油酸值、盐、温度、岩心渗透率、注入量和注入方式的影响。在实验条件下碱法造纸黑液驱稠油的采收率较水驱提高25%  相似文献   
93.
通过比较煤矿生产、安全调度显示方式的优缺点,提出和分析了适合于煤矿生产安全调度的LED电子大屏幕显示系统配置、功能及特点。  相似文献   
94.
The objective is to have uniformly distributed tangential stresses on the transition profile of a stepped bar subjected to tensile and torsional loading using an axisymmetric boundary element formulation. The transition curve is represented by the Langragian interpolation polynomial with progressive degrees to avoid shape distortion during the optimization procedure. The calculated result is compared with that obtained by fluid dynamics given in the literature. It is seen that the transition curve obtained in this paper is reasonable.  相似文献   
95.
Particulate TiB2 reinforced aluminum-based metal matrix composites (MMCs) were successfully fabricated by means of the reaction processing method. TiB2 particulates were formed in situ through the reaction of Ti and B in Ti-Al-B, TiO2 and B in TiO2-Al-B, and TiO2 and B2O3 in TiO2-Al-B2O3 systems. The results showed that in situ TiB2 particulates formed in the Ti-Al-B system had a size of 5 μm and they exhibited block and rodlike structures. Moreover, coarse Al3Ti blocks several tens of micrometers in size were also formed simultaneously. On the other hand, equiaxed Al2O3 and TiB2 particulates with a size of less than 2 μm were formed in situ in the TiO2-Al-B and TiO2-Al-B2O3 systems. The Al3Ti phase was completely eliminated in the TiO2-Al-B system with increasing B content. Tensile tests revealed that the Al2O3 · TiB2/Al composite fabricated from the TiO2-Al-B system exhibits excellent mechanical properties. The yield strength of the Al2O3 · TiB2/Al composite appeared to increase with increasing TiB2 content. The yield strength of the Al2O3 · TiB2/Al composite could be further increased by introducing CuO into the TiO2-Al-B system. Such an increment in mechanical strength arose from the strengthening effect caused by the Al2Cu precipitates. The incorporation of CuO had no effect on the in situ reaction process of the TiO2-Al-B system. Finally, the effect of SiC addition on the microstructure and mechanical properties of the composites fabricated from the TiO2-Al-B and TiO2-Al-B-CuO systems was also investigated.  相似文献   
96.
Control of peak sidelobe level in adaptive arrays   总被引:1,自引:0,他引:1  
Adaptive beamforming techniques are now widely used to reject interference (jammer/clutter) signals in radar, communication, and sonar applications. In adaptive arrays using the sample matrix inversion (SMI) algorithm, inadequate estimation of the covariance matrix results in adaptive antenna patterns with high sidelobes and distorted mainbeams. In this paper, a method is proposed to precisely control the peak (rather than average) sidelobe level of adaptive array patterns. The proposed method is also generalized to adaptive array antennas with moderate bandwidth and large random amplitude and phase errors. Theoretical analysis and simulation results are provided to illustrate the performance of the method proposed  相似文献   
97.
本文讨论了一个具有通用性的测试评估软件生成系统的设计思想和实现方法,给出了该生成器的系统组成、数据组织结构、查询搜索方式以及用户界面的设计。该系统具广泛的应用领域和实用意义。  相似文献   
98.
小型蠕动机器人原理与实现   总被引:12,自引:1,他引:11  
白绍平  汪劲松 《机器人》1994,16(3):140-143,149
本文阐述了蠕动的原理,在此基础上研制了一套小型蠕动机器人系统,其主要部分由三个La:PZT电致伸缩微位移器和一套独特的柔性链机构所组成。机器人的外形尺寸为150*61*46mm,重2kg,最大步距10μm,行程40mm,运动精度0.2μm。  相似文献   
99.
We present the design of E-kernel, an embedding kernel on the Victor V256 message-passing partitionable multiprocessor, developed for the support of program mapping and network reconfiguration. E-kernel supports the embedding of a new network topology onto Victor's 2D mesh and also the embedding of a task graph onto the 2D mesh network or the reconfigured network. In the current implementation, the reconfigured network can be a line or an even-size ring, and the task graphs meshes or tori of a variety of dimensions and shapes or graphs with similar topologies. For application programs having these task graph topologies and that are designed according to the communication model of E-kernel, they can be run without any change on partitions connected by the 2D mesh, line, or ring. Further, E-kernel attempts the communication optimization of these programs on the different networks automatically, thus making both the network topology and the communication optimization attempt completely transparent to the application programs. Many of the embeddings used in E-kernel are optimal or asymptotically optimal (with respect to minimum dilation cost). The implementation of E-kernel translated some of the many theoretical results in graph embeddings into practical tools for program mapping and network reconfiguration in a parallel system. E-kernel is functional on Victor V256. Measurements of E-kernel's performance on V256 are also included  相似文献   
100.
子波变换理论及其在信号处理中的应用   总被引:4,自引:0,他引:4  
子波分析的形成是傅里叶分析发展史上里程碑式的进展,子波分析优于傅里叶交换的地方在于它在时域和频域同时具有良好的局部化性质,从而可以把分析的重点聚焦到任意的细节,被人们誉为数学显微镜,成为近年来在工具和方法上的重大突破。本文将子波理论中的主要定理、结论、变换特性和一些重要概念加以综述,以促进子波理论的应用。本文的重点在于介绍多分辨率分析和子波分析及其实现、子波变换及其算法、子波和滤波器组等的重要内容,并介绍其在信号处理中的应用及研究动态。  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