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   21498篇
  免费   1581篇
  国内免费   700篇
电工技术   1037篇
技术理论   3篇
综合类   1305篇
化学工业   3791篇
金属工艺   1013篇
机械仪表   1279篇
建筑科学   1852篇
矿业工程   458篇
能源动力   562篇
轻工业   1474篇
水利工程   340篇
石油天然气   1093篇
武器工业   157篇
无线电   2250篇
一般工业技术   3088篇
冶金工业   1183篇
原子能技术   265篇
自动化技术   2629篇
  2024年   78篇
  2023年   297篇
  2022年   469篇
  2021年   623篇
  2020年   521篇
  2019年   462篇
  2018年   482篇
  2017年   617篇
  2016年   560篇
  2015年   737篇
  2014年   877篇
  2013年   1156篇
  2012年   1229篇
  2011年   1301篇
  2010年   1092篇
  2009年   1072篇
  2008年   1141篇
  2007年   1076篇
  2006年   1177篇
  2005年   1139篇
  2004年   716篇
  2003年   668篇
  2002年   636篇
  2001年   545篇
  2000年   692篇
  1999年   737篇
  1998年   631篇
  1997年   561篇
  1996年   494篇
  1995年   460篇
  1994年   335篇
  1993年   250篇
  1992年   210篇
  1991年   171篇
  1990年   137篇
  1989年   117篇
  1988年   90篇
  1987年   45篇
  1986年   48篇
  1985年   43篇
  1984年   18篇
  1983年   5篇
  1982年   14篇
  1981年   13篇
  1980年   13篇
  1979年   6篇
  1978年   3篇
  1977年   3篇
  1976年   4篇
  1970年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
p-偏振光在镀膜平板基片两面的反射光强度比值的角谱是膜层参数(折射率、消光系数和厚度)的函数.实验表明通过角谱的测量和数值模拟是精确测量薄膜参数的新途径.基于此原理,还试制出掺Sb的SnO2溶胶凝胶薄膜的光化学气敏传感器.  相似文献   
92.
直馏汽油异构化装置的运行   总被引:4,自引:1,他引:3  
长庆油田公司第二助剂厂新建的 70kt a直馏汽油异构化装置 ,采用二个反应器 ,以常压直馏汽油为原料 ,采用非临氢重整催化剂 ,生产的异构化汽油的研究法辛烷值约 90 ,但改质汽油收率较低 ,仅 65 %左右  相似文献   
93.
A study of dislocation configurations in superconducting oxide BiSrCaCuO has been made by transmission electron microscopy. Evidence was found for the presence of dislocation pairs composed of two parallel single dislocations holding together with the same Burgers vectors. The pair can further dissociate into partials, giving rise to a four-fold ribbon. Networks consisting of dislocation pairs were also observed. These phenomena are attributed to the possible ordering of strontium and calcium ions and the existence of some oxygen sheet of the Aurivillius type in the oxide crystal. Schemes to illustrate the configurations are suggested and discussed.  相似文献   
94.
首先本文介绍了开发富客户端应用程序的RIA技术,然后对当前一种可用的RIA技术—XUL的各方面特性以及由它实现富客户端的途径做了深入探讨,最后通过一个项目实例-订单管理系统演示了基于XUL开发富客户端应用程序的一种实现。  相似文献   
95.
立体书是一种独特的纸张艺术形式,有着精细的几何结构.针对一类特殊的V型立体纸雕进行了系统性的研究,给出了V型立体纸雕可实现性的充分条件,使其可以只借助2张支撑面的力量进行打开和关闭,同时在这个过程中所有的面片都保持刚性并且相互不产生自交.基于这些充分条件,文中分别实现了一个计算机辅助交互V型纸雕设计工具,以及一个基于体方法的自动生成算法.  相似文献   
96.
In group assessment, the focus is on finding high‐authority experts to improve the reliability of assessment results. In this study, we propose an authority updating algorithm while considering the power and judgement reliability of an expert on the basis of social networks and post‐evaluations. A network power index is established and used to reflect the power of an expert while considering social networks. The measurement of the judgement reliability of an expert considers the post‐evaluation of the objects selected by experts, thereby more scientifically reflecting the reliability of experts. The analysis shows the following: although the social‐network structure influences the authority of experts, the influence weakens when the assessment group is a highly or even fully connected group; the network effect may increase the authority of some experts and reduce that of others, and it will weaken as the network connectivity increases; moreover, the judgement reliability and authority of an expert while considering post‐evaluation can encourage him/her to make fair assessments and strive to reduce his/her motivation and cognitive biases.  相似文献   
97.
Gu  Min  Gu  Yanhui  Luo  Weilan  Xu  Guandong  Yang  Zhenglu  Zhou  Junsheng  Qu  Weiguang 《Neural computing & applications》2021,33(11):6009-6025
Neural Computing and Applications - Semantic understanding is an essential research issue for many applications, such as social network analysis, collective intelligence and content computing,...  相似文献   
98.
Unstructured peer-to-peer (P2P) networks have become a very popular architecture for content distribution in large-scale and dynamic environments. The search efficiency problem in unstructured P2P networks has not been adequately addressed so far, especially concerning search for rare objects. In this paper, we propose a proactive replication strategy to improve search efficiency for rare objects. It uses an object-probing technique for peers to decide whether or not to establish replications for their objects when they join the network. This strategy can effectively increase the popularity of rare objects in order to enhance search efficiency. We also present a rare object search algorithm to reduce the overhead caused by the replication strategy. When a peer forwards a search request, the forward probability is calculated according to its neighbors' degrees and the number of neighbors' objects. Therefore, the search request is forwarded to the peers more likely containing target objects. Simulations show that our proactive replication strategy greatly improves search efficiency for rare objects with moderate communication overhead. The rare object search algorithm not only improves search efficiency for rare objects, but also achieves load balance in search.  相似文献   
99.
Fuzzy local maximal marginal embedding for feature extraction   总被引:1,自引:0,他引:1  
In graph-based linear dimensionality reduction algorithms, it is crucial to construct a neighbor graph that can correctly reflect the relationship between samples. This paper presents an improved algorithm called fuzzy local maximal marginal embedding (FLMME) for linear dimensionality reduction. Significantly differing from the existing graph-based algorithms is that two novel fuzzy gradual graphs are constructed in FLMME, which help to pull the near neighbor samples in same class nearer and nearer and repel the far neighbor samples of margin between different classes farther and farther when they are projected to feature subspace. Through the fuzzy gradual graphs, FLMME algorithm has lower sensitivities to the sample variations caused by varying illumination, expression, viewing conditions and shapes. The proposed FLMME algorithm is evaluated through experiments by using the WINE database, the Yale and ORL face image databases and the USPS handwriting digital databases. The results show that the FLMME outperforms PCA, LDA, LPP and local maximal marginal embedding.  相似文献   
100.
This paper presents the following results on sets that are complete for NP.
  1. If there is a problem in NP that requires $2^{n^{\Omega(1)}}$ time at almost all lengths, then every many-one NP-complete set is complete under length-increasing reductions that are computed by polynomial-size circuits.
  2. If there is a problem in co-NP that cannot be solved by polynomial-size nondeterministic circuits, then every many-one NP-complete set is complete under length-increasing reductions that are computed by polynomial-size circuits.
  3. If there exist a one-way permutation that is secure against subexponential-size circuits and there is a hard tally language in NP??co-NP, then there is a Turing complete language for NP that is not many-one complete.
Our first two results use worst-case hardness hypotheses whereas earlier work that showed similar results relied on average-case or almost-everywhere hardness assumptions. The use of average-case and worst-case hypotheses in the last result is unique as previous results obtaining the same consequence relied on almost-everywhere hardness results.  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