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   447篇
  免费   31篇
  国内免费   46篇
电工技术   2篇
综合类   16篇
化学工业   126篇
金属工艺   97篇
机械仪表   16篇
建筑科学   44篇
矿业工程   3篇
能源动力   14篇
轻工业   36篇
水利工程   1篇
石油天然气   22篇
武器工业   2篇
无线电   20篇
一般工业技术   22篇
冶金工业   36篇
原子能技术   3篇
自动化技术   64篇
  2023年   13篇
  2022年   37篇
  2021年   51篇
  2020年   13篇
  2019年   9篇
  2018年   11篇
  2017年   10篇
  2016年   19篇
  2015年   18篇
  2014年   27篇
  2013年   26篇
  2012年   31篇
  2011年   42篇
  2010年   18篇
  2009年   24篇
  2008年   20篇
  2007年   30篇
  2006年   18篇
  2005年   19篇
  2004年   9篇
  2003年   13篇
  2002年   15篇
  2001年   13篇
  2000年   7篇
  1999年   6篇
  1998年   7篇
  1997年   4篇
  1996年   7篇
  1995年   1篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
排序方式: 共有524条查询结果,搜索用时 15 毫秒
1.
In the first critical assessment of knowledge economy dynamic paths in Africa and the Middle East, but for a few exceptions, we find overwhelming support for diminishing cross-country disparities in knowledge-based economy dimensions. The paper employs all the four components of the World Bank's Knowledge Economy Index (KEI): economic incentives, innovation, education, and information infrastructure. The main finding suggests that sub-Saharan African (SSA) and the Middle East and North African (MENA) countries with low levels of KE dynamics and catching-up their counterparts of higher KE levels. We provide the speeds of integration and time necessary to achieve full (100%) integration. Policy implications are also discussed.  相似文献   
2.
Bestehen ausreichende Anhaltspunkte für die Hochwassergef?hrdung, ist die Gemeinde verpflichtet, sich durch Nachforschungen Gewissheit über das Vorliegen oder Nichtvorliegen eines Hochwasserabflussgebietes gem § 38 Abs 3 WRG zu verschaffen. Liegt ein solches vor, hat sie gem § 12 Abs 1 Z 2 krnt GplG dieses im Fl?chenwidmungsplan ersichtlich zu machen. Erteilt die Gemeinde eine Baubewilligung ohne diese von der Erteilung einer wasserrechtlichen Bewilligung abh?ngig zu machen, haftet sie für die Kosten der Bauführung, die bei gesetzes-konformer Vorgangsweise unterlassen worden w?re.  相似文献   
3.
Wang  Fuhui  Geng  Shujiang  Zhu  Shenglong 《Oxidation of Metals》2002,58(1-2):185-195
A nanocrystalline coating of K38G alloy was obtained by means of magnetron sputtering. The corrosion behavior of cast K38G alloy and its sputtered nanocrystalline coating with a solid NaCl deposit in dry air or wet oxygen at 600 and 700°C have been studied and compared. The results indicated that the mass gain of the coating is higher than that of the cast alloy at 600 and 700°C. Therefore, nanocrystallization reduced the corrosion resistance at these temperatures. Furthermore, the mass gains of the coating and the cast alloy with a NaCl deposit in wet oxygen were less than that with a NaCl deposit in dry air. The relevant corrosion mechanisms are discussed.  相似文献   
4.
Games such as CHESS, GO and OTHELLO can be represented by minimax game trees. Among various search procedures to solve such game trees,- and SSS* are perhaps most well known. Although it is proved that SSS* explores only a subset of the nodes explored by-, - is commonly believed to be faster in real applications, since it requires very little memory space and hence its storage management cost is low. Contrary to this folklore, however, this paper reports, using the OTHELLO game as an example, that SSS* is much faster than-. It is also demonstrated that SSS* can be modified to make the required memory space controllable to some extent, while retaining the high efficiency of the original SSS*.This research was partially supported by the Ministry of Education, Science and Culture of Japan, under a Scientific Grant-in-Aid.  相似文献   
5.
Given its uniformly high expression on plasma cells, CD38 has been considered as a therapeutic target in patients with systemic lupus erythematosus (SLE). Herein, we investigate the distribution of CD38 expression by peripheral blood leukocyte lineages to evaluate the potential therapeutic effect of CD38-targeting antibodies on these immune cell subsets and to delineate the use of CD38 as a biomarker in SLE. We analyzed the expression of CD38 on peripheral blood leukocyte subsets by flow and mass cytometry in two different cohorts, comprising a total of 56 SLE patients. The CD38 expression levels were subsequently correlated across immune cell lineages and subsets, and with clinical and serologic disease parameters of SLE. Compared to healthy controls (HC), CD38 expression levels in SLE were significantly increased on circulating plasmacytoid dendritic cells, CD14++CD16+ monocytes, CD56+ CD16dim natural killer cells, marginal zone-like IgD+CD27+ B cells, and on CD4+ and CD8+ memory T cells. Correlation analyses revealed coordinated CD38 expression between individual innate and memory T cell subsets in SLE but not HC. However, CD38 expression levels were heterogeneous across patients, and no correlation was found between CD38 expression on immune cell subsets and the disease activity index SLEDAI-2K or established serologic and immunological markers of disease activity. In conclusion, we identified widespread changes in CD38 expression on SLE immune cells that highly correlated over different leukocyte subsets within individual patients, but was heterogenous within the population of SLE patients, regardless of disease severity or clinical manifestations. As anti-CD38 treatment is being investigated in SLE, our results may have important implications for the personalized targeting of pathogenic leukocytes by anti-CD38 monoclonal antibodies.  相似文献   
6.
7.
An efficient method to monitor changes in soil inorganic N content during crop growth would be a useful means to guide N fertilization to ensure high yields and low N losses to the environment. In this study, soil apparent electrical conductivity (ECa) measured by the widely used conductivity meter EM38 was tested as an indirect measurement of available N in spring barley during two cropping seasons at two sites with morainic loam in SE Norway. The experiment was constructed to maximize soil variation. In spite of the ȁ8noiseȁ9 caused by the soil heterogeneity, concentrations of inorganic N (cNinorg) or NO3-N were most strongly correlated with ECa in both years and at both locations (with one exception). The measurements of ECa reflected well the temporal variation in inorganic N content (Ninorg), and a ranking of the treatments based on ECa fitted very well with a ranking based on Ninorg at the first three sampling times after fertilizing. The best subset of sensor variables (i.e. variables which can be measured ȁ8on-the-goȁ9 by sensor techniques in the field) described 27–69% (average 47%) of the variation in topsoil cNinorg. When expanding the regression models to include pH as well, the degree of explanation increased significantly. In conclusion, the method of using ECa appears to be quite robust in terms of detecting relative differences in cNinorg, whereas a determination of absolute levels of cNinorg with the method is unreliable.  相似文献   
8.
为使冲压仿真工程师高效地整理仿真结果并生成仿真报告,介绍JSTAMP/NV软件的自动报告书功能及其操作流程;以自动生成汽车翼子板的拉深工序的仿真报告为例,详细说明JSTAMP/NV自动报告书功能的使用.该功能可显著减少制作仿真报告的工作量.  相似文献   
9.
p38MAPK抑制剂增强阿霉素抑制乳腺癌细胞增殖的体外研究   总被引:1,自引:0,他引:1  
以乳腺癌细胞株MCF-7为研究对象,经阿霉素及阿霉素联合p38MAPK抑制剂(SB20580)作用细胞,通过MTT法测定细胞存活率、光学显微镜观察细胞形态变化。实验数据显示相同药物浓度下,SB20580可以明显降低MCF-7细胞存活率。结果表明p38MAPK抑制剂可以促进阿霉素抑制细胞增殖的效果。  相似文献   
10.
Geng  S.  Wang  F.  Zhu  S.  Wu  W. 《Oxidation of Metals》2002,57(5-6):549-557
The hot-corrosion behavior of a nanocrystalline coating of K38G alloy, prepared by magnetron sputtering and cast K38G in molten 75 wt.% Na2SO4+25 wt.% K2SO4 at 900°C was studied. The coating eliminated internal sulfidation during the early stage of corrosion as a result of the formation of a continuous and compact Al2O3 scale. The nanocrystallization of K38G alloy prolonged the incubation of breakaway corrosion and improved the corrosion resistance of K38G. The relevant corrosion mechanism is discussed.  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