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   7278篇
  免费   193篇
  国内免费   11篇
电工技术   113篇
综合类   12篇
化学工业   1078篇
金属工艺   112篇
机械仪表   135篇
建筑科学   285篇
矿业工程   18篇
能源动力   161篇
轻工业   661篇
水利工程   96篇
石油天然气   6篇
无线电   682篇
一般工业技术   1028篇
冶金工业   2104篇
原子能技术   61篇
自动化技术   930篇
  2023年   26篇
  2022年   72篇
  2021年   115篇
  2020年   57篇
  2019年   88篇
  2018年   118篇
  2017年   99篇
  2016年   120篇
  2015年   95篇
  2014年   162篇
  2013年   273篇
  2012年   278篇
  2011年   345篇
  2010年   241篇
  2009年   241篇
  2008年   260篇
  2007年   283篇
  2006年   198篇
  2005年   202篇
  2004年   193篇
  2003年   177篇
  2002年   166篇
  2001年   109篇
  2000年   111篇
  1999年   162篇
  1998年   692篇
  1997年   459篇
  1996年   316篇
  1995年   192篇
  1994年   188篇
  1993年   186篇
  1992年   79篇
  1991年   73篇
  1990年   84篇
  1989年   72篇
  1988年   86篇
  1987年   55篇
  1986年   56篇
  1985年   76篇
  1984年   52篇
  1983年   39篇
  1982年   46篇
  1981年   46篇
  1980年   42篇
  1979年   47篇
  1978年   41篇
  1977年   52篇
  1976年   78篇
  1975年   34篇
  1974年   25篇
排序方式: 共有7482条查询结果,搜索用时 15 毫秒
21.
22.
具有高含量3,4-结构的IR能特别有效地提高高性能轮胎的湿抓着力。因此,可以通过调整炭黑和BR用量来提高轮胎的磨耗和滚动阻力性能,同时保持优异的湿抓着性能。  相似文献   
23.
The composition of the lipids of two samples of krill and one of “red crab” was determined by thin layer, column and gas chromatographic procedures. A large number of unusual fatty acids were present.  相似文献   
24.
An inventory is made of the possibilities to recover sustainable energy from the water cycle by identifying different water flows in a municipal environment as a sustainable energy source. It is discussed what role public water utilities should play in the market of energy from water. This is done for Waternet, the public water utility of Amsterdam, by describing experiences on two practical applications for aquifer thermal energy storage and energy recovery from drinking water. The main conclusion is that public water utilities can substantially contribute to the production of sustainable energy, especially by making use of heat and cold from the water cycle. Public water utilities have the opportunity to both regulate and enter the market for energy from water.  相似文献   
25.
This letter presents an improved cue integration approach to reliably separate coherent moving objects from their background scene in video sequences. The proposed method uses a probabilistic framework to unify bottom-up and top-down cues in a parallel, "democratic" fashion. The algorithm makes use of a modified Bayes rule where each pixel's posterior probabilities of figure or ground layer assignment are derived from likelihood models of three bottom-up cues and a prior model provided by a top-down cue. Each cue is treated as independent evidence for figure-ground separation. They compete with and complement each other dynamically by adjusting relative weights from frame to frame according to cue quality measured against the overall integration. At the same time, the likelihood or prior models of individual cues adapt toward the integrated result. These mechanisms enable the system to organize under the influence of visual scene structure without manual intervention. A novel contribution here is the incorporation of a top-down cue. It improves the system's robustness and accuracy and helps handle difficult and ambiguous situations, such as abrupt lighting changes or occlusion among multiple objects. Results on various video sequences are demonstrated and discussed. (Video demos are available at http://organic.usc.edu:8376/ approximately tangx/neco/index.html .).  相似文献   
26.
A novel-type Raman cell especially suitable for the generation of tunable vacuum ultraviolet (VUV) radiation with pump radiation from a frequency-doubled dye laser is described. This hydrogen-filled Raman cell permits the generation of narrow-bandwidth radiation to below 114 nm. Absolute VUV energies in the various anti-Stokes orders and measurements of pulse durations and pressure dependences are given.  相似文献   
27.
4. Conclusions Diastolic LV function and myocardial HEP metabolism are impaired only when LVH is caused by permanent pressure or volume overload, and not by a temporary increase in cardiac workload during part of the day as in elite athletes. Therefore, training-induced and pressure/volume-overload-induced LVH seem to represent different phenotypes of LVH, possibly related to genetic reprogramming which only occurs during permanent cardiac overload [17]. Moreover, there is an association between impaired LV diastolic function and altered myocardial HEP metabolism in patients with hypertension and in patients with aortic valve disease. Finally we did not find a correlation between myocardial HEP metabolism and LV mass in any of the groups studied. The latter indicates that LVH should be regarded as an epiphenomenon to cardiac overload, and not as a primary factor causing abnormal HEP metabolism.  相似文献   
28.
Business process models are becoming available in large numbers due to their widespread use in many industrial applications such as enterprise and quality engineering projects. On the one hand, this raises a challenge as to their proper management: how can it be ensured that the proper process model is always available to the interested stakeholder? On the other hand, the richness of a large set of process models also offers opportunities, for example with respect to the re-use of existing model parts for new models. This paper describes the functionality and architecture of an advanced process model repository, named APROMORE. This tool brings together a rich set of features for the analysis, management and usage of large sets of process models, drawing from state-of-the art research in the field of process modeling. A prototype of the platform is presented in this paper, demonstrating its feasibility, as well as an outlook on the further development of APROMORE.  相似文献   
29.
As the need for concepts such as cancellation and OR-joins occurs naturally in business scenarios, comprehensive support in a workflow language is desirable. However, there is a clear trade-off between the expressive power of a language (i.e., introducing complex constructs such as cancellation and OR-joins) and ease of verification. When a workflow contains a large number of tasks and involves complex control flow dependencies, verification can take too much time or it may even be impossible. There are a number of different approaches to deal with this complexity. Reducing the size of the workflow, while preserving its essential properties with respect to a particular analysis problem, is one such approach. In this paper, we present a set of reduction rules for workflows with cancellation regions and OR-joins and demonstrate how they can be used to improve the efficiency of verification. Our results are presented in the context of the YAWL workflow language.  相似文献   
30.
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