全文获取类型
收费全文 | 398150篇 |
免费 | 5432篇 |
国内免费 | 1831篇 |
专业分类
电工技术 | 7021篇 |
综合类 | 314篇 |
化学工业 | 59133篇 |
金属工艺 | 17150篇 |
机械仪表 | 12574篇 |
建筑科学 | 9029篇 |
矿业工程 | 1986篇 |
能源动力 | 10127篇 |
轻工业 | 32778篇 |
水利工程 | 3851篇 |
石油天然气 | 7688篇 |
武器工业 | 31篇 |
无线电 | 48756篇 |
一般工业技术 | 79507篇 |
冶金工业 | 76208篇 |
原子能技术 | 8923篇 |
自动化技术 | 30337篇 |
出版年
2021年 | 3344篇 |
2019年 | 3026篇 |
2018年 | 5307篇 |
2017年 | 5203篇 |
2016年 | 5650篇 |
2015年 | 3822篇 |
2014年 | 6380篇 |
2013年 | 17331篇 |
2012年 | 10358篇 |
2011年 | 14117篇 |
2010年 | 11414篇 |
2009年 | 13014篇 |
2008年 | 13297篇 |
2007年 | 13122篇 |
2006年 | 11701篇 |
2005年 | 10742篇 |
2004年 | 10070篇 |
2003年 | 9676篇 |
2002年 | 9418篇 |
2001年 | 9498篇 |
2000年 | 8894篇 |
1999年 | 9354篇 |
1998年 | 24150篇 |
1997年 | 17028篇 |
1996年 | 13264篇 |
1995年 | 9594篇 |
1994年 | 8599篇 |
1993年 | 8397篇 |
1992年 | 6019篇 |
1991年 | 5946篇 |
1990年 | 5706篇 |
1989年 | 5569篇 |
1988年 | 5352篇 |
1987年 | 4421篇 |
1986年 | 4441篇 |
1985年 | 5046篇 |
1984年 | 4726篇 |
1983年 | 4287篇 |
1982年 | 4073篇 |
1981年 | 4188篇 |
1980年 | 3960篇 |
1979年 | 3801篇 |
1978年 | 3818篇 |
1977年 | 4430篇 |
1976年 | 5964篇 |
1975年 | 3422篇 |
1974年 | 3264篇 |
1973年 | 3265篇 |
1972年 | 2831篇 |
1971年 | 2604篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We report the first case of primitive breast fibromatosis associated with a synchronous independent musculo-aponeurotic fibromatosis of the omolateral pectoralis major muscle in an otherwise healthy 29-year-old woman without clinical evidence of any genetic syndrome. The primary occurrence of the two lesions was supported by the absence of any macroscopic and microscopic connection. The present case suggests that a pre- or intraoperative frozen section diagnosis of breast fibromatosis should lead the surgeon and pathologist to exclude an independent fibromatosis of the underlying musculo-aponeurotic fascia. 相似文献
992.
993.
An unconditionally stable two-stage CMOS amplifier 总被引:1,自引:0,他引:1
This paper describes a two-stage CMOS amplifier that is stable for any capacitive load. This is achieved through the use of an optimized cascoded compensation topology. A new level shifting technique allows independent optimization of drive capability, noise and systematic offset voltage. The circuit is 0.1 mm2 in a 2 μm technology and has a quiescent current consumption of 110 μA 相似文献
994.
A memory-based processing approach to discourse comprehension emphasizes the rapid deployment of information in memory to facilitate understanding of the text that is currently being read. S. B. Greene, R. J. Gerrig, G. McKoon, and R. Ratcliff (1994) demonstrated that when a text described the reunion of 2 characters who had previously discussed a 3rd character, the accessibility of the 3rd character increased, and the use of an unheralded pronoun (R. J. Gerrig, 1986) to refer to that character was felicitous. In experiments in this article, the authors demonstrate that concepts related to the unheralded pronoun also increase in accessibility and that those concepts form associations in memory with concepts present in the discourse at the time the pronoun is used. The authors also show that the increase in accessibility for the referent of the pronoun, as well as the appropriate long-term memory associations, occurs even in the absence of the pronoun. 相似文献
995.
996.
Concurrent engineering (CE) is a vital concept in the world of new product development, and up-to-date information about the extent of its adoption and the use of the enabling tools in the engineering industry is of great value. This article presents the data from an industry-wide survey of technical managers and analyses the significance of the information obtained. This reveals that CE is beginning to be widely applied, but there are significant differences between large and smaller companies, and between different industrial sectors 相似文献
997.
Reininger D.J. Dipankar Raychaudhuri Hui J.Y. 《Selected Areas in Communications, IEEE Journal on》1996,14(6):1076-1086
A scheme for delivery or variable bit-rate (VBR) video over asynchronous transfer mode (ATM) networks where bandwidth can be renegotiated during the duration of a call between the video source and the network is considered. Renegotiation can be initiated by either the video source or the network. The video bandwidth requirement is characterized by a usage parameter control (UPC) consisting, in general, of peak rate, burst length, and sustained rate. A baseline design is outlined where rate-control adjusts the source's rate while a new UPC is requested from the network. When granted, the new UPC allows the source to maintain its target quantization and delay requirements. Rate control epochs may be extended when the network blocks UPC requests or sets a lower UPC value to temporally deal with congestion. Simulation results are presented for VBR MPEG video. The results show that with a moderate renegotiation rate the scheme tracks the bandwidth requirements of the source. As a result, the video quality and bandwidth efficiency can be maintained 相似文献
998.
999.
Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori. 相似文献
1000.
Luk Chiu Li Jagdish Parasrampuria Ron Levans Kurt G. Van Scoik 《Drug development and industrial pharmacy》1994,20(13):2079-2090
The moisture-uptake kinetics of a hygroscopic powder, sodium heparin contained in a cylindrical container, was determined using a novel moisture-uptake measuring device under a constant convective air flow. The amount of moisture uptake increased with the increase in the relative humidity of the air. The effect of powder-bed height on the total amount of moisture uptake was found to be significant only at the highest relative humidity (75%) evaluated in this study. However, the percent of weight increase of the powder as a result of moisture uptake decreases as the height of the powder bed increases. The results of this study are explained by the dynamic nature of the moisture-uptake process associated with the instrument. 相似文献