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   1503172篇
  免费   26223篇
  国内免费   7083篇
电工技术   35136篇
综合类   6396篇
化学工业   272893篇
金属工艺   66052篇
机械仪表   44367篇
建筑科学   45638篇
矿业工程   11786篇
能源动力   50350篇
轻工业   109537篇
水利工程   15174篇
石油天然气   38433篇
武器工业   150篇
无线电   198527篇
一般工业技术   286453篇
冶金工业   151066篇
原子能技术   34430篇
自动化技术   170090篇
  2021年   15666篇
  2020年   11913篇
  2019年   14674篇
  2018年   18384篇
  2017年   18133篇
  2016年   22466篇
  2015年   17552篇
  2014年   28724篇
  2013年   88078篇
  2012年   35634篇
  2011年   49755篇
  2010年   44798篇
  2009年   53295篇
  2008年   45936篇
  2007年   43660篇
  2006年   43941篇
  2005年   40163篇
  2004年   41492篇
  2003年   41155篇
  2002年   40044篇
  2001年   36417篇
  2000年   35032篇
  1999年   33969篇
  1998年   40829篇
  1997年   36682篇
  1996年   33528篇
  1995年   29570篇
  1994年   27872篇
  1993年   27824篇
  1992年   25866篇
  1991年   22919篇
  1990年   23306篇
  1989年   22393篇
  1988年   20855篇
  1987年   19208篇
  1986年   18536篇
  1985年   21860篇
  1984年   22181篇
  1983年   20119篇
  1982年   19131篇
  1981年   19242篇
  1980年   17843篇
  1979年   18387篇
  1978年   17631篇
  1977年   17224篇
  1976年   17671篇
  1975年   15959篇
  1974年   15479篇
  1973年   15546篇
  1972年   13031篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
This article describes the phenomenon of morphological instability in solid-solid phase transformations during thin-film interdiffusion, specifically related to the initial stages of precipitation when phase growth occurs along the interface between thin films. The experimental observations that revealed this effect will be presented, and a working hypothesis will be discussed. Experimental observations suggest that the ledge mechanism of growth is present in this system but does not inhibit the formation of interfacial instabilities. It is proposed that morphological stability for solid-phase growth occurring during thin-film interdiffusion can be treated by the inclusion of a solute-source term into the two-dimensional perturbation approach generally used to study unstable growth morphologies. Experimental observations that provide qualitative and semiquantitative support for the solute-source model are also presented.  相似文献   
993.
994.
Translated from Izmeritel'naya Tekhnika, No. 3, pp. 57–58, March, 1993.  相似文献   
995.
We report the results of the first national survey of psychologists in private practice regarding their participation in peer consultation groups. The sample (71% return) was drawn from 800 randomly selected psychologists listed in the National Register of Health Service Providers in Psychology. We found that 23% of the sample currently belonged to peer consultation groups, and 24% had belonged in the past. Of those not currently in groups, 61% expressed the desire to belong if one were available. There were virtually no significant demographic differences between current members and nonmembers. We examined the following group characteristics: formation, length of existence, size, membership, leadership, theoretical orientation, range of experience, time and place, content, and group process. Groups tended to be small, informal, and leaderless; however, we found great variation among groups on all dimensions. Findings also showed a high degree of satisfaction with membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
996.
The effect of enzymatic hydrolysis of proteins in milk using neutrase on the growth of the probiotic strain Bifidobacterium bifidus was evaluated by estimation of microbial growth, acidity, viscosity and flavour production. A significant increase in the growth of B bifidus was observed in neutrase‐hydrolysed milk. The setting time of bifidus‐cultured milk was advanced by about 12 h at 5% degree of hydrolysis. Enzymatic hydrolysis of proteins prior to cultivation also significantly increased the viscosity of the product. An approximately 60% increase in viscosity of the product was observed in neutrase‐hydrolysed milk. Production of steam‐volatile monocarbonyls as an indication of development of flavour was also higher in neutrase‐hydrolysed milk. The concentration of steam‐volatile monocarbonyls was 2.47 µmol per 100 ml in neutrase‐hydrolysed milk but only 1.84 µmol per 100 ml in control milk at the setting point of the curd. © 2002 Society of Chemical Industry  相似文献   
997.
The paper proposes a structure for quality-of-service (QoS)-centered service level agreements (SLA), and a framework for their real-time management in multiservice packet networks. The SLA is structured to be fair to both parties, the service provider and their customer. The SLA considered here are for QoS assured delivery of aggregate bandwidth from ingress to egress nodes; however, the control and signaling is for the more granular flows or calls. A SLA monitoring scheme is presented in which revenue is generated by the admission of flows into the network, and penalty incurred when flows are lost in periods when the service provider is not SLA compliant. In the SLA management scheme proposed, the results of a prior off-line design are used, in conjunction with measurements taken locally at ingress nodes, to classify the loading status of routes. The routing and resource management are based on virtual partitioning and its supporting mechanism of bandwidth protection. The effectiveness of SLA management is measured by the robustness in performance in the presence of substantial diversity in actual traffic conditions. A simulation testbed called D'ARTAGNAN has been built from which we report numerical results for a case study. The results show that the SLA management scheme is robust, fair and efficient over a broad range of traffic conditions  相似文献   
998.
999.
An InAs/AlGaAs quantum-dot infrared photodetector based on bound-to-bound intraband transitions in undoped InAs quantum dots is reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 /spl mu/m. At 77 K and -0.7 V bias, the responsivity was 14 mA/W and the detectivity, D*, was 10/sup 10/ cm/spl middot/Hz/sup 1/2//W.  相似文献   
1000.
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