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   7670篇
  免费   302篇
  国内免费   38篇
电工技术   156篇
综合类   22篇
化学工业   1895篇
金属工艺   202篇
机械仪表   208篇
建筑科学   191篇
矿业工程   10篇
能源动力   401篇
轻工业   722篇
水利工程   59篇
石油天然气   46篇
无线电   796篇
一般工业技术   1508篇
冶金工业   770篇
原子能技术   76篇
自动化技术   948篇
  2023年   69篇
  2022年   129篇
  2021年   274篇
  2020年   177篇
  2019年   179篇
  2018年   246篇
  2017年   217篇
  2016年   235篇
  2015年   155篇
  2014年   254篇
  2013年   544篇
  2012年   427篇
  2011年   475篇
  2010年   346篇
  2009年   330篇
  2008年   349篇
  2007年   300篇
  2006年   282篇
  2005年   223篇
  2004年   174篇
  2003年   175篇
  2002年   171篇
  2001年   115篇
  2000年   130篇
  1999年   102篇
  1998年   268篇
  1997年   187篇
  1996年   157篇
  1995年   125篇
  1994年   108篇
  1993年   112篇
  1992年   61篇
  1991年   67篇
  1990年   57篇
  1989年   55篇
  1988年   65篇
  1987年   50篇
  1986年   52篇
  1985年   51篇
  1984年   63篇
  1983年   36篇
  1982年   40篇
  1981年   42篇
  1980年   34篇
  1979年   33篇
  1978年   36篇
  1977年   25篇
  1976年   53篇
  1975年   31篇
  1974年   32篇
排序方式: 共有8010条查询结果,搜索用时 421 毫秒
81.
Based on deformable templates, the paper formulates an integrated and flexible Bayesian recognition system of multiple occluded objects. Various local dependence properties of the model are obtained to reduce the computational cost with the increase in the number of objects. Numerical results for a synthetic image and for a real image of mushrooms are discussed  相似文献   
82.
Phase-induced intensity noise from weak multiple reflectors is evaluated theoretically and experimentally in amplifier cascades without isolators. Rayleigh backscattering alone significantly limits the number of amplifiers in the span. Theory and experiment agree closely for a six-amplifier cascade.<>  相似文献   
83.
In this paper the time-domain surface impedances of an homogeneous absorber layer, are given for the vertical and horizontal polarizations, or respectively for the electric field perpendicular or parallel to the incidence plane. It turns out that the application of the concept in finite difference time-domain (FDTD) in absorbing surface impedances boundary conditions, gives results in good agreement with analytical Fresnel reflection coefficients.  相似文献   
84.
85.
86.
87.
88.
We examined the effect of meprin A, the major matrix degrading metalloproteinase in rat kidney, on the laminin-nidogen complex. N-terminal sequence information from the most abundant 55 kDa fragment revealed that it was a breakdown product of nidogen rather than laminin. In comparison with over 50 nidogen cleavage sites produced by other proteases, the meprin A-induced nidogen cleavage site at amino acid position 899-900, a glutamine-glycine site in the G3 domain, is unique. In addition, these data demonstrate that meprin A degrades the G3 domain of nidogen even in the presence of laminin binding, which usually accords protection from proteolytic degradation. Meprin A also degraded purified nidogen into similar breakdown products. Given that the tubular basement membrane is located on the basilar side of the cell, the location of meprin A on the apical brush border makes it difficult to envision a role for meprin A in injury-induced basement membrane component breakdown. Thus, we examined the possibility that following renal tubular epithelial cell injury, meprin A undergoes a translocation to reach the underlying basement membrane. After renal ischemia-reperfusion there was a marked alteration in meprin A staining with meprin A now distributed throughout the renal tubular cell cytoplasm and directly adherent to the tubular basement membrane. This was in contrast to the usual linear staining of the brush border of tubules in the corticomedullary junction. These data provide unequivocal evidence that following injury, meprin A undergoes redistribution and/or adherence to the tubular basement membrane. Since in our in vitro studies, we identified a distinct meprin-induced 55 kDa nidogen breakdown product, the urine was also examined for the presence of nidogen degradation products after rat renal ischemia-reperfusion injury. Western blots showed a marked increase in the urinary 55 kDa nidogen fragment as early as the first day following ischemia-reperfusion injury and continuing for six days. Taken together, these in vivo data strongly support the notion that the nidogen breakdown products are the result of partial degradation of tubular basement membrane by meprin A following renal tubular ischemia-reperfusion injury.  相似文献   
89.
90.
Cyberattacks are difficult to prevent because the targeted companies and organizations are often relying on new and fundamentally insecure cloud-based technologies, such as the Internet of Things. With increasing industry adoption and migration of traditional computing services to the cloud, one of the main challenges in cybersecurity is to provide mechanisms to secure these technologies. This work proposes a Data Security Framework for cloud computing services (CCS) that evaluates and improves CCS data security from a software engineering perspective by evaluating the levels of security within the cloud computing paradigm using engineering methods and techniques applied to CCS. This framework is developed by means of a methodology based on a heuristic theory that incorporates knowledge generated by existing works as well as the experience of their implementation. The paper presents the design details of the framework, which consists of three stages: identification of data security requirements, management of data security risks and evaluation of data security performance in CCS.  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