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   2267篇
  免费   33篇
  国内免费   1篇
电工技术   17篇
化学工业   229篇
金属工艺   49篇
机械仪表   36篇
建筑科学   121篇
矿业工程   7篇
能源动力   66篇
轻工业   200篇
水利工程   14篇
石油天然气   8篇
无线电   172篇
一般工业技术   372篇
冶金工业   771篇
原子能技术   13篇
自动化技术   226篇
  2021年   13篇
  2019年   18篇
  2018年   13篇
  2017年   21篇
  2016年   12篇
  2015年   20篇
  2014年   24篇
  2013年   115篇
  2012年   55篇
  2011年   85篇
  2010年   70篇
  2009年   59篇
  2008年   71篇
  2007年   77篇
  2006年   67篇
  2005年   71篇
  2004年   62篇
  2003年   56篇
  2002年   42篇
  2001年   49篇
  2000年   46篇
  1999年   52篇
  1998年   216篇
  1997年   119篇
  1996年   78篇
  1995年   71篇
  1994年   75篇
  1993年   63篇
  1992年   36篇
  1991年   22篇
  1990年   20篇
  1989年   20篇
  1988年   21篇
  1987年   21篇
  1986年   22篇
  1985年   23篇
  1984年   21篇
  1983年   14篇
  1982年   25篇
  1981年   24篇
  1980年   18篇
  1979年   24篇
  1978年   24篇
  1977年   37篇
  1976年   60篇
  1975年   16篇
  1974年   13篇
  1973年   19篇
  1972年   14篇
  1968年   13篇
排序方式: 共有2301条查询结果,搜索用时 484 毫秒
101.
The paper presents Bayesian information fusion theory in the context of neural-network model combination. It shows how confidence measures can be combined with individual model estimates to minimize risk through the fusion process. The theory is illustrated through application to the real task of quality prediction in the papermaking industry. Prediction uncertainty estimates are calculated using approximate Bayesian learning. These are incorporated into model combination as confidence measures. Cost functions in the fusion center are used to control the influence of the confidence measures and improve the performance of the resultant committee.  相似文献   
102.
Pfizer Inc. is a research based global pharmaceutical company committed to the discovery and development of innovative medicines that improve the quality of life of individuals throughout the world. In order to gain a competitive advantage over competitor companies in the discovery of new medicines, we must speed up drug discovery and drive down costs. Using non-combinatorial chemistry techniques increases the efficiency with which we discover new ‘leads,’ leveraging our drug discovery efforts through retaining complete control over the properties of each product made. Compound purification, managed through in-house software, augments the quality of data obtained upon biological screening of compounds.  相似文献   
103.
104.
BACKGROUND: The precise mechanisms involved in islet xenograft rejection remain unknown. The purpose of the present study was to determine cellular mechanisms responsible for islet xenograft rejection in the liver to facilitate finding a procedure for prevention of immune rejection. METHODS: Hepatic mononuclear cells (MNC) as well as splenocytes, peripheral blood MNC, and thymocytes from streptozotocin-induced diabetic mice (BALB/c) rejecting the intrahepatic rat (Lewis) islet xenografts were isolated and examined by two-color FACS analysis. RESULTS: The characteristic finding of the hepatic MNC from the mice rejecting islet xenografts compared with mice receiving isografts was a significant increase in the yield as well as in the percentage of the cells expressing CD3+ interleukin-2 receptor (IL-2R) alpha- beta+, CD3+ CD8alpha+ beta+, and T cell receptor (TCR) alphabeta+ lymphocyte function-associated antigen-1+. The expression of CD3 and TCR alphabeta of these T cells was found to be of intermediate intensity (TCR(int) cells). The expansion of these TCR(int) cells occurred predominantly in the liver. There was no significant difference in the cells expressing CD3+ IL-2R alpha+, CD3+ CD4+, CD3+ TCRgammadelta+, CD3- IL-2Rbeta+ (natural killer cells), and B220+ (B cells). In vivo administration of anti-IL-2Rbeta monoclonal antibody directed to the expanded cells produced a prevention of rejection. CONCLUSIONS: These findings suggest that islet xenograft rejection in the liver from rat to mouse is an event for which the TCR(int) cells are responsible.  相似文献   
105.
The Vanderbilt free-electron laser (FEL) is a continuously tunable source of pulsed, mid-infrared radiation. FEL applications research has been underway for a decade. Recent experimental advances in FEL ablation of soft tissue indicate the potential for FEL-based protocols in surgery and medicine. In anticipation of these medical applications, the Vanderbilt FEL is being upgraded to meet the reliability and performance standards for a medical laser. Facilities for laser surgery have been constructed and equipped and medical delivery systems are being developed for pre-clinical and clinical research  相似文献   
106.
107.
108.
109.
Real-time multimedia communication applications demand performance requirements which differ significantly from conventional data communication applications. Current local area networks (LANs) provide efficient transport for bursty data traffic; however, they cannot necessarily provide quality of service guarantees for real-time communications. In this work we introduce and investigate an experimental priority protocol for supporting real-time communication on Ethernet, a popular implementation of multiple-access broadcast bus LANs. We examine the new protocol, known as Priority Mode-CSMA/CD (PM-CSMA/CD), providing a high priority (HP) class with CSMA/CD employed for standard priority (SP) traffic. PM-CSMA/CD performance is examined through computer simulation of videotelephony workstations operating over the shared bus LAN. Over all observed traffic conditions, the priority protocol provides performance satisfying real-time packet transport requirements of audio and video streams. The primary advantage of our protocol over similar priority schemes is its physical layer compatibility with standard CSMA/CD. The protocol also provides improved channel utilization with increasing high priority load, with no penalty in SP class performance at low to medium network loads.  相似文献   
110.
BACKGROUND: Human serum represents an important barrier to the entry of most mucosal organisms into tissues and to the systemic circulation. If at all present, Helicobacter pylori within gastric tissue is rare, and bacteremia for this organism has been described only once. METHODS: To assess the susceptibility of H. pylori to the bactericidal activity present in normal human serum (NHS), we examined 13 H. pylori isolates. To assess the contributions of the classical and alternative complement pathways to killing, we added either C2-deficient or factor B-deficient serum, respectively, to heat-inactivated NHS. Also we assessed the ability of the strains to bind 125I-C3. RESULTS: After incubation for 60 minutes at 37 degrees C, all 13 H. pylori strains were killed by NHS; heating to 56 degrees C for 30 minutes ablated killing, indicating complement dependence for this phenomenon. In the absence of an antibody source, there was no killing when either an alternative or classical complement pathway source was used. Adding B-deficient serum to heat-inactivated normal human serum did not restore killing, but adding C2-deficient serum permitted partial killing. All of the 13 strains bound 125I-C3. Although the kinetics varied from strain to strain, C3 bound was significantly correlated (r = 0.61, p = 0.03) with serum susceptibility. CONCLUSIONS: H. pylori are susceptible to complement, alternative pathway activation appears critical, and C3 binding is a major locus of variability.  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