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   55978篇
  免费   5142篇
  国内免费   2740篇
电工技术   3553篇
技术理论   8篇
综合类   3649篇
化学工业   9517篇
金属工艺   3006篇
机械仪表   3292篇
建筑科学   4017篇
矿业工程   1528篇
能源动力   1766篇
轻工业   3530篇
水利工程   1107篇
石油天然气   2882篇
武器工业   649篇
无线电   6982篇
一般工业技术   6860篇
冶金工业   2914篇
原子能技术   705篇
自动化技术   7895篇
  2024年   260篇
  2023年   919篇
  2022年   1828篇
  2021年   2493篇
  2020年   1832篇
  2019年   1543篇
  2018年   1705篇
  2017年   1815篇
  2016年   1636篇
  2015年   2302篇
  2014年   2732篇
  2013年   3462篇
  2012年   3612篇
  2011年   3818篇
  2010年   3352篇
  2009年   3248篇
  2008年   3139篇
  2007年   2970篇
  2006年   3003篇
  2005年   2486篇
  2004年   1863篇
  2003年   1625篇
  2002年   1682篇
  2001年   1545篇
  2000年   1328篇
  1999年   1347篇
  1998年   1172篇
  1997年   997篇
  1996年   807篇
  1995年   686篇
  1994年   507篇
  1993年   434篇
  1992年   337篇
  1991年   272篇
  1990年   192篇
  1989年   190篇
  1988年   145篇
  1987年   87篇
  1986年   91篇
  1985年   78篇
  1984年   35篇
  1983年   27篇
  1982年   37篇
  1981年   34篇
  1980年   23篇
  1979年   21篇
  1977年   16篇
  1976年   19篇
  1974年   13篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
A semiconductor factory contains hundreds of pieces of equipment. More reliable service by equipment managers is required to increase the utilization of equipment and improve product quality and yield. Therefore, developing a reliable service management scheme (SMS) for semiconductor factory management systems is essential. This study presents an SMS that applies Jini Technology and uses the design by contract technologies. The SMS has error-detecting and function-replacing capabilities. The SMS detects the malfunctioning of an equipment manager (service) and sends an event notice to the factory manager. The GEV in the SMS archives the credit values of all of the equipment managers so that the factory manager can select better equipment managers for service by checking their credit values. The illustrative example and the evaluation of the reliability improvement reveal that the proposed SMS provides an efficient, reliable, fault tolerant, and cost-effective mechanism for semiconductor factory management systems. Lastly, this illustrative example is successfully implemented and demonstrated and the core technology of SMS is transferred to and commercialized by Charming Systems Corporation.  相似文献   
82.
83.
3.5代移动通信中的链路自适应技术使用自适应调制编码和快速混合重传技术替代了3代中使用的功率控制技术。仿真结果比较了这两种新技术与功率控制技术的性能,证明了这两个新技术显著地提高了网络平均的吞吐量。  相似文献   
84.
85.
The binding of 125I-labelled tissue plasminogen activator (tPA), the tPA A- or B-chain to endothelial cells (EC) were studied in suspensions of cultured human umbilical vein EC (HUVEC) or immortalized microvascular EC (HMEC). By determinations of the concentration-dependent binding it was shown that both the A-chain and the B-chain, which were isolated after partial reduction of two-chain tPA, contain ligands for binding to EC. The affinity for the B-chain was much higher than for the A-chain according to Scatchard analysis (Kd 24 and 515 nM, respectively), whereas the number of binding sites was higher for the A-chain than for the B-chain (Bmax 8 x 10(5) and 1.2 x 10(5), respectively). There were no cross interactions between the A- and B-chains and their binding sites. The binding of tPA to EC induced an almost 100-fold increase of the activation rate when compared to the same amount of enzyme in free solution, which in contrast to the fibrin-induced stimulation was not inhibited by antibodies against fibrin. The enzymatic activity of the B-chain was much less affected by the association to the cells. Both tPA and the tPA B-chain were largely protected against inhibition by an excess plasminogen activator type-1 (PAI-1) when bound to EC, whereas the same amount of free tPA was totally inactivated. The competition studies strongly indicated that an N-terminal segment in the B-chain, AKHRRSPGER, may be the ligand part of the B-chain. It is interesting to note that this polypeptide segment also participates in a binding site for PAI-1, necessary for effective inhibition. This implies a possible competition between PAI-1 and a tPA-receptor for binding of tPA. High molecular weight urokinase had no quenching effect on the binding of the B-chain to EC.  相似文献   
86.
Designing circuits with partial scan   总被引:1,自引:0,他引:1  
In this scan design methodology, only selected faults are targeted for detection. These faults are those not detected by the designer's functional vectors. The test generator decides exactly which flip-flops should be scanned using one of two methods. In the first method, all possible tests are generated for each target fault, and the set of tests requiring the fewest flip-flops is selected. In the second method, only one test is generated for each fault, and the use of flip-flops is avoided as much as possible during test generation. Examples of actual VLSI circuits show a savings of at least a 40% in full-scan overhead  相似文献   
87.
Birds' use of landmarks to identify spatial locations was examined. Black-capped chickadees (Parus atricapillus) and pigeons (Columba livia) searched for hidden food on a 120-cm–2 tray. In each task the target was near an edge with a nearby landmark. On occasional unrewarded tests the landmark was either left in its usual position, shifted parallel to the edge, shifted perpendicular to the edge, or shifted diagonally. On diagonal landmark shifts the birds shifted their searching more in the parallel direction than in the perpendicular, which violates the predictions of the vector sum model (K. Cheng, 1989). In some cases the birds maintained their searching at a constant perpendicular distance under all landmark shifts. This suggests that perpendicular distance to an edge forms an element in determining where to search on the basis of landmarks. Chickadees and pigeons performed similarly, which suggests similarity in the way they encode locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
88.
在辽宁省工业城市进行 A3钢大气暴露试验。两年后测出不同地点腐蚀率。依据所记录的各试验点的气象数据和污染数据,讨论了 A3钢的大气腐蚀规律。  相似文献   
89.
海湾战争中,“爱国者”导弹成功地拦截了“飞毛腿”导弹,给近程地对地战术导弹的作用、发展与装备方向提出了值得思考的问题。本文着重讨论在局部战争中,近程地对地战术导弹的作用、使用场合及其技术发展方向。  相似文献   
90.
结构化P2P网络中基于流言传播的负载均衡   总被引:11,自引:0,他引:11  
提出了结构化P2P网络中利用结点间周期性的拓扑维护通信来夹带、传播消息进行负载均衡的方法,具体针对Chord系统从消息传播的速度和规模两个方面分析了该方法的性能,并利用仿真进行了验证。讨论了结论在其它形式网络中的推广和实现中的消息管理问题。  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