首页 | 官方网站   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   5105篇
  免费   312篇
  国内免费   4篇
工业技术   5421篇
  2023年   35篇
  2022年   59篇
  2021年   207篇
  2020年   112篇
  2019年   130篇
  2018年   168篇
  2017年   161篇
  2016年   205篇
  2015年   157篇
  2014年   261篇
  2013年   368篇
  2012年   347篇
  2011年   377篇
  2010年   262篇
  2009年   290篇
  2008年   252篇
  2007年   236篇
  2006年   161篇
  2005年   141篇
  2004年   115篇
  2003年   134篇
  2002年   103篇
  2001年   60篇
  2000年   68篇
  1999年   81篇
  1998年   219篇
  1997年   146篇
  1996年   109篇
  1995年   80篇
  1994年   67篇
  1993年   51篇
  1992年   23篇
  1991年   22篇
  1990年   20篇
  1989年   24篇
  1988年   13篇
  1987年   15篇
  1986年   16篇
  1985年   11篇
  1984年   9篇
  1983年   11篇
  1982年   10篇
  1981年   14篇
  1980年   9篇
  1979年   4篇
  1978年   12篇
  1977年   14篇
  1976年   15篇
  1973年   3篇
  1968年   2篇
排序方式: 共有5421条查询结果,搜索用时 15 毫秒
1.
Wireless Personal Communications - Underwater Wireless Sensor Networks (UWSNs) are playing a vital role in exploring the unseen underwater (UW) natural resources. However, performance evaluation of...  相似文献   
2.
Alcohol-free beer with isotonic properties is getting more popular and its production can be carried out by different production strategies; however, interrupted fermentation is still a challenge. Therefore, the objective of this study was to develop a low-alcohol isotonic beer (<0.5% v/v) by interrupted fermentation. Moreover, the major objective is to compare the developed product to commercial beverages (sports drinks, ‘Pilsen' regular beer, alcohol-free beers and low-alcohol isotonic beer). The beverages were evaluated based on pH, alcohol content (% v/v), total titratable acidity (mEq L−1), osmolality (mOsmol kg−1), bitterness International Bitterness Units, colour European Brewery Convention, total phenolic compounds (mg L−1 gallic acid), reducing and total sugars (%) and Na and K contents (mg L−1). The developed low-alcohol isotonic beer presented characteristics similar to sports drinks, with the advantage of being richer in phenolic compounds and suitable osmolality. Despite salts were added in its formulation, the grades attributed to all beers employed in the sensory evaluation, as well as the purchase intention did not present significant differences.  相似文献   
3.
4.
5.
6.
Software and Systems Modeling - Many model transformation scenarios require flexible execution strategies as they should produce models with the highest possible quality. At the same time,...  相似文献   
7.
Reactivity between SiC and Ir as a function of SiC-crystallinity was investigated by diffusion bonding technique under a vacuum and over the temperature range of 1200–1450 °C. As reaction products, various Ir-silicides and free unreacted-C were detected. Reactivity is strongly affected by the temperature and SiC-crystallinity involving a series of interactions, from “no reaction” to “massive exothermic reactions”. In particular, interfacial phenomena are more pronounced by the presence of defects and grain boundaries.Solid state reactions result in formation of fine C-precipitates rearranged in a quasi-periodic microstructure. On the contrary, clustering of highly ordered C-precipitates (C-graphitized) occurs after “massive reactions” take place.A relationship between the degree of graphitization (from 1 to multi-layers of graphene), temperature and SiC crystallinity was found by Raman spectroscopy. 2D-layering phenomenon is enhanced in polycrystalline SiC at high temperature.  相似文献   
8.
9.
10.
Recently, preemption techniques have attracted considerable attention as a means to provide differentiated quality of service in optical burst switching (OBS) networks. This paper is focused on the analysis of preemption probabilities for bursts within the same priority class. As proposed by Vokkarane and Jue ((2003)* IEEE J Select Areas Commun 21(7): 1198–1209) an incoming burst will preempt the burst in service, within the same priority class, if the residual length of the burst in service is smaller than the incoming burst length. For a general case with wavelength conversion, the preemption probability of contending bursts with a generic service distribution, not necessarily exponential, is analyzed. First, we show that the size distribution for the preempting bursts is shifted to larger values, in comparison to the original burst size distribution. Second, we obtain an upper and lower bound for the preemption probability. Finally, the asymptotic behavior of the OBS switch is analyzed showing that preemption will always occur for a very large number of wavelengths.  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-23

京公网安备 11010802026262号