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   2747篇
  免费   22篇
电工技术   26篇
综合类   2篇
化学工业   152篇
金属工艺   20篇
机械仪表   20篇
建筑科学   13篇
矿业工程   1篇
能源动力   19篇
轻工业   69篇
水利工程   3篇
石油天然气   4篇
无线电   50篇
一般工业技术   72篇
冶金工业   2263篇
原子能技术   4篇
自动化技术   51篇
  2024年   3篇
  2022年   15篇
  2021年   21篇
  2020年   15篇
  2019年   22篇
  2018年   19篇
  2017年   9篇
  2016年   15篇
  2015年   12篇
  2014年   22篇
  2013年   18篇
  2012年   27篇
  2011年   21篇
  2010年   23篇
  2009年   27篇
  2008年   28篇
  2007年   28篇
  2006年   12篇
  2005年   10篇
  2004年   15篇
  2003年   22篇
  2002年   11篇
  2001年   14篇
  2000年   17篇
  1999年   69篇
  1998年   691篇
  1997年   425篇
  1996年   259篇
  1995年   176篇
  1994年   120篇
  1993年   160篇
  1992年   24篇
  1991年   39篇
  1990年   31篇
  1989年   35篇
  1988年   28篇
  1987年   25篇
  1986年   23篇
  1985年   25篇
  1983年   5篇
  1982年   8篇
  1981年   15篇
  1980年   21篇
  1978年   5篇
  1977年   49篇
  1976年   93篇
  1975年   2篇
  1974年   4篇
  1973年   4篇
  1961年   1篇
排序方式: 共有2769条查询结果,搜索用时 15 毫秒
1.
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   
2.
3.
In this work, we investigated a procedure which exploits microwave ovens to produce SiC- based components by reactive melt infiltration of silicon into graphite preforms. The employed oven is designed to grant optical access to the sample surface, which allows to measure its temperature evolution though a noncontact pyrometer. This signal was used as a feedback to control the power provided to the preform and as an experimental output whose analysis provides insight into the reaction mechanism. Specifically, it is found that complete infiltration is achieved much before the end of the reaction. The latter is not fully self-sustained as the global reaction rate continuously decreases with time until it is no more able to keep the temperature above the silicon solidification value. At that point, the reaction stops. The analysis of the processed samples proved that this procedure allows producing fully infiltrated samples without material failure by adjusting the heat provided during the infiltration stage rather than by tuning the preform structure and composition, which is the usual approach. The proposed method is less time and energy consuming than the standard one.  相似文献   
4.
Guest Editorial: Wireless Mobile Internet   总被引:1,自引:0,他引:1  
  相似文献   
5.
The transjugular intrahepatic portosystemic shunt procedure is an accepted treatment for adults with complications of portal hypertension. We performed a retrospective review of all pediatric TIPS placements performed at the University of California, San Francisco between 1990 and 1996. Twelve procedures were attempted in nine children, with a mean age (+/- SD) of 9.4 +/- 3.9 years (range, 5 to 15 years) and a mean weight of 31 +/- 18 kg (range, 16 to 70 kg). The indications for TIPS placement were portal hypertension complicated by chronic variceal hemorrhage not controlled with sclerotherapy (n = 7) and hypersplenism with thrombocytopenia (n = 2). TIPS placement was successfully completed initially in seven of nine (78%) patients. Unfavorable vascular anatomy was the cause of failure in two cases. The seven patients who underwent successful TIPS placement were followed up for an average of 136 days (range, 1 to 800 days); two still have patent shunts, three underwent liver transplantation, one had a splenorenal shunt after stenosis, and one died of underlying liver disease. Variceal bleeding was controlled in four of five patients who successfully underwent TIPS placement. Shunt occlusion occurred in four patients; patency was restored by transjugular shunt revision in three, and a splenorenal shunt was performed in one.  相似文献   
6.
7.
Research in the past few years has documented significant advances in our understanding of the CD40-CD40 ligand (CD154) system in diverse immune functions. This system influences many T cell mediated inflammatory immune responses and effector functions, unmasking a previously unexpected role for CD40-CD154 in cell mediated immunity. Manipulation of CD154 in animal models of infection by the use of CD154-deficient mice or anti-CD154 antibodies has shown the importance of this system in the initiation of the inflammatory response, in the activation of antigen-presenting cells and in resistance to infections.  相似文献   
8.
A genetic linkage map of human chromosome 21q (HC21q) containing 43 markers genotyped by the polymerase chain reaction in the CEPH pedigrees is presented. The markers placed on this map are highly polymorphic with an average heterozygosity of 61%. The average interval size of the markers localized at 1000:1 odds is 2.5 cM. The map has a total length of 65.5 cM, with male and female lengths of 47.7 and 83.3 cM, respectively. The genotypes used in the construction of this map were subjected to rigorous error checking, which is reflected in the shorter map length compared to previous maps; the estimated error rate in genotyping is less than 0.04%. As noted in previous linkage maps there is increased recombination in females on proximal HC 21q and in the male in a region near the telomere. This map of HC 21 represents a highly informative and dense meiotic linkage map and will be useful in linking disease phenotypes to loci on this chromosome.  相似文献   
9.
10.
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