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   114483篇
  免费   12140篇
  国内免费   6694篇
电工技术   8582篇
技术理论   8篇
综合类   9769篇
化学工业   17593篇
金属工艺   6427篇
机械仪表   7619篇
建筑科学   9467篇
矿业工程   3510篇
能源动力   3329篇
轻工业   10128篇
水利工程   2734篇
石油天然气   4809篇
武器工业   1312篇
无线电   13077篇
一般工业技术   12068篇
冶金工业   4513篇
原子能技术   1553篇
自动化技术   16819篇
  2024年   457篇
  2023年   2104篇
  2022年   4045篇
  2021年   5550篇
  2020年   4171篇
  2019年   3264篇
  2018年   3631篇
  2017年   4025篇
  2016年   3511篇
  2015年   5152篇
  2014年   6587篇
  2013年   7693篇
  2012年   8831篇
  2011年   9000篇
  2010年   8516篇
  2009年   7919篇
  2008年   7658篇
  2007年   7120篇
  2006年   6483篇
  2005年   5188篇
  2004年   3711篇
  2003年   2836篇
  2002年   2828篇
  2001年   2367篇
  2000年   2137篇
  1999年   1876篇
  1998年   1220篇
  1997年   1066篇
  1996年   996篇
  1995年   760篇
  1994年   642篇
  1993年   457篇
  1992年   377篇
  1991年   278篇
  1990年   195篇
  1989年   188篇
  1988年   124篇
  1987年   73篇
  1986年   56篇
  1985年   35篇
  1984年   35篇
  1983年   19篇
  1982年   23篇
  1981年   24篇
  1980年   36篇
  1979年   15篇
  1977年   3篇
  1976年   3篇
  1959年   10篇
  1951年   16篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
In this paper, based on adaptive dynamic programming (ADP) with concurrent learning, the problem of optimal guaranteed cost tracking is studied for a class  相似文献   
73.
Wang  Wencheng  Yuan  Xiaohui  Wu  Xiaojin  Dong  Yihua 《Multimedia Tools and Applications》2020,79(37-38):27185-27203
Multimedia Tools and Applications - As the key parameter of dehazing algorithms, airlight value directly affect the calculation accuracy of sky region, and any deviation will lead to the chromatic...  相似文献   
74.
在丙烷脱沥青装置加热炉试烧装置自产调合前沥青,通过观察油枪雾化沥青的能力、火嘴的燃烧情况以及燃烧后的烟尘状况,筛选出适合沥青燃烧的油枪,最终实现调合前沥青直接做加热炉燃料、减少重油出厂量的目的。  相似文献   
75.
The {100} facet of single-crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures.  相似文献   
76.
Neural Computing and Applications - More and more enterprises hope to achieve cooperation and win–win. However, many companies often have problems such as insufficient partner credit, which...  相似文献   
77.
中国深层煤层气资源丰富,但总体勘探和认识程度较低,尚未形成较为系统的深层煤层气地质理论。通过解剖分析准噶尔盆地白家海凸起和鄂尔多斯盆地临兴区块深层"超饱和"煤层气井的试气/生产动态,估算原地游离气的含气量,分析了深层"超饱和"煤层气的形成条件。研究表明:①深层"超饱和"煤层气储层中除吸附气外,还含有原地游离气,用常规试气方法可直接获得气流,煤层气的产出不明显依赖于排水降压;②埋藏超过一定深度,在煤阶和温度的综合作用下,煤的吸附能力将随埋深的继续增加而降低,煤层中吸附气的饱和度有增加的趋势,在达到吸附饱和后,出现原地游离气并形成"超饱和"煤层气,盆地深层具有"超饱和"煤层气形成的优势条件;③由于地温梯度和压力梯度的不同,不同盆地"超饱和"煤层气出现的临界深度不同,异常高压和异常高热流可以降低深层"超饱和"煤层气形成的临界深度;④深层"超饱和"煤层气开发具有大大缩短见气时间、充分利用地层能量和累积产水量低等优势,有望成为未来煤层气勘探开发的一个重要领域。  相似文献   
78.
Video transmission over IEEE 802.11e wireless networks still shows poor performance for large bandwidth demand and frequently changed environments. Thus, several enhancements of IEEE 802.11e were proposed. On the other hand, big frames and simultaneous sending of adjacent frames always cause packet dropping for buffer overflow. In the past, we proposed an IEEE 802.11e enhancement named DFAA and a content aware mechanism to solve the above problems. The motivation of this paper is to find a proper way to integrate these two mechanisms. A DFAA enhancement (DFAA-E) is proposed to make up the insufficiency of content aware mechanism. Experiments results show that the combination of DFAA-E and content aware mechanism improves the video decoded quality greatly. And its performance can be further enhanced by selecting the suitable settings of certain parameters.  相似文献   
79.
This work is concerned with the prediction of visual colour difference between pairs of palettes. In this study, the palettes contained five colours arranged in a horizontal row. A total of 95 pairs of palettes were rated for visual difference by 20 participants. The colour difference between the palettes was predicted using two algorithms, each based on one of six colour-difference formulae. The best performance (r2 = 0.86 and STRESS = 16.9) was obtained using the minimum colour-difference algorithm (MICDM) using the CIEDE2000 equation with a lightness weighing of 2. There was some evidence that the order (or arrangement) of the colours in the palettes was a factor affecting the visual colour differences although the MICDM algorithm does not take order into account. Application of this algorithm is intended for digital design workflows where colour palettes are generated automatically using machine learning and for comparing palettes obtained from psychophysical studies to explore, for example, the effect of culture, age, or gender on colour associations.  相似文献   
80.
Carbohydrates and their conjugates play important roles in many biological processes including fertilization, differentiation, development, immune response, and infection. Their activities are largely dependent on the properties of terminal mono‐ or disaccharides. Galactose, mannose, fucose, glucose, sialic acid, etc., are commonly used as powerful scaffolds installed on drug molecules for targeting specific tissues including brain, liver, and cancers, and as epitopes for enhancing the targeting of various vaccines. This review focuses on the influence of their structural variations, including changes in sugar type, substituent groups and their positions, as well as length of linker portion, on the targeting of drugs or their efficacy. Particular attention is paid to the targeting properties of mono‐ and disaccharides applied in drug design and discovery.  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