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   1530771篇
  免费   26587篇
  国内免费   7154篇
电工技术   34861篇
综合类   6439篇
化学工业   273530篇
金属工艺   65410篇
机械仪表   43956篇
建筑科学   46581篇
矿业工程   11658篇
能源动力   50450篇
轻工业   114930篇
水利工程   15516篇
石油天然气   38146篇
武器工业   149篇
无线电   198249篇
一般工业技术   288560篇
冶金工业   171209篇
原子能技术   34277篇
自动化技术   170591篇
  2021年   15770篇
  2020年   12028篇
  2019年   14780篇
  2018年   17333篇
  2017年   16803篇
  2016年   22163篇
  2015年   17617篇
  2014年   28865篇
  2013年   88323篇
  2012年   36108篇
  2011年   49601篇
  2010年   43974篇
  2009年   52273篇
  2008年   45990篇
  2007年   43581篇
  2006年   44879篇
  2005年   40388篇
  2004年   41920篇
  2003年   41684篇
  2002年   40671篇
  2001年   37368篇
  2000年   35768篇
  1999年   35017篇
  1998年   46947篇
  1997年   40549篇
  1996年   36167篇
  1995年   31262篇
  1994年   29143篇
  1993年   29074篇
  1992年   26317篇
  1991年   23462篇
  1990年   23762篇
  1989年   22913篇
  1988年   21446篇
  1987年   19627篇
  1986年   18992篇
  1985年   22334篇
  1984年   22450篇
  1983年   20406篇
  1982年   19346篇
  1981年   19485篇
  1980年   18113篇
  1979年   18587篇
  1978年   17855篇
  1977年   17828篇
  1976年   18996篇
  1975年   16139篇
  1974年   15570篇
  1973年   15665篇
  1972年   13163篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
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   
992.
993.
Translated from Izmeritel'naya Tekhnika, No. 3, pp. 57–58, March, 1993.  相似文献   
994.
This investigation retrospectively examined changes in marital satisfaction following stroke. The relationship between such changes and other pertinent factors were also examined, including severity of aphasia, knowledge of aphasia, number of months after stroke, and length of the marriage. The subjects were 40 spouses of patients with aphasia grouped according to severity of the aphasia (mild, moderate, severe). Spouses completed two different measures of marital satisfaction--the Marital Satisfaction Scale (MSS) and the Marital Comparison Level Index (MCLI). These measures were completed in both a prestroke (retrospective reporting) and a poststroke format to allow for change to be assessed. In addition, a Knowledge of Aphasia questionnaire was completed by the normal spouses to evaluate their understanding of the disorder of aphasia. There was a significant difference between prestroke and poststroke scores on both the MSS and the MCLI, indicating a lower level of satisfaction following the stroke. The amount of change between prestroke and poststroke MSS and MCLI scores was not related to either number of months poststroke or number of years married. Although there was no relationship between changes in prestroke and poststroke scores on the MCLI and Knowledge of Aphasia scores, there was a significant correlation between changes in these scores on the MSS and Knowledge of Aphasia scores. Hence, the more knowledge spouses had regarding aphasia, the less the negative impact the stroke had on marital satisfaction, as measured by the MSS. Results are discussed in terms of the interdisciplinary treatment needs of aphasic patients and the implications for future investigations.  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.
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