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   1729篇
  免费   4篇
电工技术   1篇
化学工业   36篇
机械仪表   3篇
建筑科学   5篇
能源动力   9篇
轻工业   17篇
无线电   8篇
一般工业技术   23篇
冶金工业   1603篇
自动化技术   28篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2020年   1篇
  2019年   5篇
  2018年   3篇
  2017年   2篇
  2015年   2篇
  2014年   3篇
  2013年   12篇
  2012年   3篇
  2011年   9篇
  2010年   8篇
  2009年   3篇
  2008年   5篇
  2007年   10篇
  2006年   3篇
  2005年   2篇
  2004年   10篇
  2003年   6篇
  2002年   4篇
  2001年   1篇
  2000年   3篇
  1999年   39篇
  1998年   490篇
  1997年   290篇
  1996年   186篇
  1995年   107篇
  1994年   77篇
  1993年   119篇
  1992年   14篇
  1991年   13篇
  1990年   13篇
  1989年   21篇
  1988年   24篇
  1987年   21篇
  1986年   28篇
  1985年   21篇
  1983年   2篇
  1982年   10篇
  1981年   9篇
  1980年   12篇
  1979年   2篇
  1978年   2篇
  1977年   42篇
  1976年   85篇
  1975年   2篇
  1974年   1篇
  1971年   1篇
  1955年   1篇
排序方式: 共有1733条查询结果,搜索用时 15 毫秒
31.
Understanding the mechanisms responsible for photodamage to the skin is most important for dermatology. 3-D cultures have been used as tools to mimic the in vivo situation for several years. We irradiated such a system containing human dermal fibroblasts cultured in collagen gels, a well-known model considered to be a dermal equivalent, which reproduces the interaction between cells and the surrounding extracellular matrix. The effects of solar irradiation (315-800 nm) on the steady-state levels of the mRNAs of extracellular matrix components (type I and III collagens) and their degrading enzymes (interstitial collagenase, MMP-1 and stromelysin 1, MMP-3) were measured. Exposure to low levels of solar radiation (0-10 J cm-2 in the UVA, i.e. suberythemal UVA doses) caused a transient decrease in type I procollagen mRNA, an increase in MMP-mRNA, and no change in type III procollagen mRNA steady-state levels. These results describe the early changes in the connective tissue of the skin following exposure to low-level solar stimulation, and may help explain the long-term changes in photodamaged skin.  相似文献   
32.
33.
34.
Regulators of G protein signaling (RGS) proteins act as GTPase-activating proteins (GAPs) toward the alpha subunits of heterotrimeric, signal-transducing G proteins. RGS11 contains a G protein gamma subunit-like (GGL) domain between its Dishevelled/Egl-10/Pleckstrin and RGS domains. GGL domains are also found in RGS6, RGS7, RGS9, and the Caenorhabditis elegans protein EGL-10. Coexpression of RGS11 with different Gbeta subunits reveals specific interaction between RGS11 and Gbeta5. The expression of mRNA for RGS11 and Gbeta5 in human tissues overlaps. The Gbeta5/RGS11 heterodimer acts as a GAP on Galphao, apparently selectively. RGS proteins that contain GGL domains appear to act as GAPs for Galpha proteins and form complexes with specific Gbeta subunits, adding to the combinatorial complexity of G protein-mediated signaling pathways.  相似文献   
35.
PURPOSE: This study aimed to identify a dangerous new weapon capable of causing damage to the ocular and periocular regions. METHODS: The authors report two patients who had penetrating ocular injury in the past year because of homemade recreational potato guns. RESULTS: In one 14-year-old boy, projectiles from the firing of a potato gun resulted in orbital and cranial injuries that were life threatening with widespread fractures, marked disruption of facial structures, a cerebrospinal fluid fistula requiring bifrontal surgical repair, and loss of one eye. In a separate accident with a different potato gun, a 14-year-old boy who was wearing glasses at the time of injury had a sight-threatening perforating corneal laceration. CONCLUSION: Practitioners must be aware of the existence of these new, homemade unregulated devices. Information about the use and construction of these guns is widespread on the Internet, but no injuries resulting from these guns currently are documented in the medical literature.  相似文献   
36.
In recent years, innovative applications based on the detection of emission sources such as the light emission from off-state leakage current (LEOSLC) of CMOS transistors have been developed for testing and diagnosing modern ultralarge-scale integration circuits. In this paper, we show that LEOSLC can be used to effectively debug circuits, localize defects with a quick turn around time, read the logic state of gates, and extract the internal voltage drop of power distribution grids among others.  相似文献   
37.
38.
39.
40.
McManus  John 《ITNOW》2007,49(6):8-9
Poor service provision within the global software services industryis contributing to a profound rethink in many firms that offerinformation and technology services. Recent press reports suggestthat all but a few software providers are willing to committhe organisation and its resources to high volume high riskservice provision.  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