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   769篇
  免费   29篇
  国内免费   42篇
系统科学   26篇
丛书文集   17篇
教育与普及   31篇
理论与方法论   6篇
现状及发展   7篇
研究方法   4篇
综合类   749篇
  2024年   6篇
  2023年   16篇
  2022年   18篇
  2021年   27篇
  2020年   6篇
  2019年   3篇
  2018年   6篇
  2017年   7篇
  2016年   12篇
  2015年   13篇
  2014年   32篇
  2013年   28篇
  2012年   32篇
  2011年   33篇
  2010年   34篇
  2009年   43篇
  2008年   35篇
  2007年   28篇
  2006年   20篇
  2005年   27篇
  2004年   22篇
  2003年   18篇
  2002年   9篇
  2001年   31篇
  2000年   24篇
  1999年   35篇
  1998年   43篇
  1997年   41篇
  1996年   43篇
  1995年   25篇
  1994年   21篇
  1993年   17篇
  1992年   21篇
  1991年   13篇
  1990年   11篇
  1989年   12篇
  1988年   16篇
  1987年   8篇
  1986年   3篇
  1985年   1篇
排序方式: 共有840条查询结果,搜索用时 0 毫秒
151.
文章简要介绍了当前中国隧道监控系统的构成,在此基础上分析了控制系统的整体解决方案以及其区域控制器(PLC)及网络的选型,同时,以贵州玉凯高速公路项目为例,详细分析了单隧道和隧道群的具体解决方案,最后分析了隧道监控系统的改进与发展。  相似文献   
152.
翟伟红 《甘肃科技》2009,25(13):90-91
通过分析图书馆人力资源的现状及存在的问题,提出了图书馆人力资源管理的新理念,认为图书馆在人力资源管理方面应以人为本,引入竞争机制、激励机制等。  相似文献   
153.
Proteins differentially expressed from maize leaves in response to the infection by Curvularia lunata strain CX-3 were identified through a high-resolution two-dimensional gel electrophoresis (2-DE) method. Two inbred lines, 78599-1 and E28, were used, respectively, as resistant and susceptible lines to CX-3 infection. Proteins were extracted from the fourth leaves of six- or seven-leaf stage plants sampled at 24, 36, 48, 60, and 72 h after inoculation with CX-3. Twenty-seven differentially expressed protein spots resolved on the 2-DE gels were identified by MALDI-TOF MS/MS. The results showed that these proteins are associated with photosynthesis, respiration,oxidative and drought stress tolerance as well as signal transduction in maize. Among stress-related proteins, the 22 kDa drought-inducible protein, putative glutathione peroxidase (GPX), and translation initiation factor (eIF-5A) were up-regulated in the resistant inbred line and were implicated in host defense response to C. lunata infection. It suggests that drought-inducible and oxidation stress-related proteins might directly contribute to maize resistance to C. lunata.  相似文献   
154.
TRAIL is a tumor necrosis factor family member that selectively induces apoptosis of cancer cells but not of normal cells. To develop TRAIL into a potential cancer drug, three different sizes of soluble TRAIL fragments, including sTRAIL(74—281), sTRAIL(95—281) and sTRAIL(101—281), were expressed in E. coli and purified to homogeneity. Apoptosis assays indicated that sTRAIL(95—281) and sTRAIL(101—281), but not sTRAIL(74—281), can potently induce apoptosis of various cancer cell lines in 6 h, suggesting that the N-terminal fragment of aa101 has inhibitory effect on TRAIL-induced apoptosis. Moreover, we found that some cancer cells were resistant to TRAIL and the resistant cells could be converted into sensitive cells by treatment with the protein synthesis inhibitor cycloheximide, suggesting that one or more short-lived proteins are responsible for cells’ resistance to TRAIL.  相似文献   
155.
An NIH3T3 cell line which overexpresses temperature-sensitive p53Val135 was constructed by introduction of p53Val135 gene. It exhibited rapidly characteristic morphological and biochemical alterations related to repli-cative senescence when being cultured in 32℃. We suggested that the overexpression of p53 activated probably the onset of senescence in NIH3T3 cells, which induced a rapid cellular senescence.  相似文献   
156.
文章对建筑安装工程施工中土建与安装之间配合存在的问题和原因进行了剖析,并提出相应的对策。  相似文献   
157.
遥感影像中浅水河道与居民地具有相似的光谱特性,在浅水河道自动提取过程中噪声较多,经验模态分解(EMD)可获取原始信号不同尺度上的细节信息,有效地提高遥感影像浅水河道自动提取的精度。利用环境与减灾小卫星数据,以彰武县柳河为研究区,对该区2012年10个时期NDVI时间序列分别EMD分解,选取每个时相信息量较大的前三个固有模态函数(IMF),结合2012年9月18号影像共34波段作为研究数据,利用极大似然法、BP神经网络传统的分类方法进行分类。结果表明结合EMD的分类方法可有效地去除居民地噪声, Kappa系数最高达到0.9690,总体分类精度最高达到93.35%,从而有效地解决了遥感影像中浅水河道提取正确率低的难题。  相似文献   
158.
IF-like proteins have been obtained from suspension cells of Nicotiana tabacum by selective extraction. Western blot analysis shows that the major components of IF-like proteins are 6 keratin-like proteins of 64, 58, 55, 54, 50 and 45 ku. Specially the 50 ku ptotein also reacts with polyantibody against microtublin. Two-dimensional gel electrophoresis shows that the 50 ku protein is composed of two different proteins and their amino acid sequences have been determined. Part of the sequence of one protein is identical to that of β-microtublin and the other protein's sequence has no significant homologue, which should be a new sequence-unknown protein. These results suggest that 50 ku keratin-like protein and β-microtublin coexist in higher plant cells, and that may lead to the phenomenon of co-distribution of IF and microtuble in plant cells.  相似文献   
159.
一种高效率PS光子互连网络的实验研究   总被引:1,自引:0,他引:1  
在分析互连元件四脊棱镜和菲涅耳棱镜组等效关系的基础上,对由此构成的光子互连网络进行了实验研究,并给出了具体实验方案及结果。  相似文献   
160.
文章从会计诚信问题形成的原因及如何重塑会计诚信方面作了探索,旨在呼唤会计诚信的回归.  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