全文获取类型
收费全文 | 4745篇 |
免费 | 110篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 31篇 |
综合类 | 10篇 |
化学工业 | 324篇 |
金属工艺 | 17篇 |
机械仪表 | 66篇 |
建筑科学 | 154篇 |
矿业工程 | 1篇 |
能源动力 | 83篇 |
轻工业 | 160篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
无线电 | 428篇 |
一般工业技术 | 455篇 |
冶金工业 | 2548篇 |
原子能技术 | 16篇 |
自动化技术 | 548篇 |
出版年
2023年 | 23篇 |
2022年 | 27篇 |
2021年 | 36篇 |
2020年 | 37篇 |
2019年 | 43篇 |
2018年 | 59篇 |
2017年 | 46篇 |
2016年 | 84篇 |
2015年 | 56篇 |
2014年 | 71篇 |
2013年 | 143篇 |
2012年 | 94篇 |
2011年 | 117篇 |
2010年 | 101篇 |
2009年 | 125篇 |
2008年 | 136篇 |
2007年 | 118篇 |
2006年 | 119篇 |
2005年 | 85篇 |
2004年 | 86篇 |
2003年 | 96篇 |
2002年 | 64篇 |
2001年 | 70篇 |
2000年 | 77篇 |
1999年 | 131篇 |
1998年 | 764篇 |
1997年 | 458篇 |
1996年 | 341篇 |
1995年 | 201篇 |
1994年 | 159篇 |
1993年 | 160篇 |
1992年 | 48篇 |
1991年 | 56篇 |
1990年 | 53篇 |
1989年 | 59篇 |
1988年 | 67篇 |
1987年 | 55篇 |
1986年 | 45篇 |
1985年 | 53篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1981年 | 28篇 |
1980年 | 21篇 |
1979年 | 4篇 |
1978年 | 13篇 |
1977年 | 46篇 |
1976年 | 102篇 |
1975年 | 9篇 |
1973年 | 4篇 |
排序方式: 共有4859条查询结果,搜索用时 203 毫秒
51.
52.
Laser light scattering techniques for making two- and three-dimensional measurements in turbulent flows and flames are outlined, and examples of data representations are shown. Limitations and problems in displaying data are discussed 相似文献
53.
54.
Chan B.C.B. Chan F.H.Y. Lam F.K. Ping-Wing Lui Poon P.W.F. 《IEEE transactions on bio-medical engineering》1997,44(4):237-246
The introduction of air bubbles into the systemic circulation can result in significant morbidity. Real-time monitoring of continuous heart sound in patients detected by precordial Doppler ultrasound is, thus, vital for early detection of venous air embolism (VAE) during surgery. In this study, the multiscale feature of wavelet transforms (WT's) is exploited to examine the embolic Doppler heart sound (DHS) during intravenous air injections in dogs. As both humans and dogs share similar physiological conditions, the authors' methods and results for dogs are expected to be applicable to humans. The WT of DHS at scale 2 j(j=1,2) selectively magnified the power of embolic, but not the normal, heart sound. Statistically, the enhanced embolic power was found to be sensitive (P<0.01 at 0.01 ml of injected air) and correlated significantly (P<0.0005, τ=0.83) with the volume of injected air from 0.01 to 0.10 ml. A fast detection algorithm of O(N) complexity with unit complexity constant for VAE was developed (processing speed=8 ms per heartbeat), which confirmed the feasibility of real-time processing for both humans and dogs 相似文献
55.
56.
57.
This paper presents a new model to study the reliability of communication networks in which link failures are statistically dependent. The approach tries to identify and model explicitly the events that cause communication link failures. No conditional probabilities are needed, and so two major difficulties inherent to them, namely, an exponential number of conditional probabilities to deal with and a consistency requirement to satisfy, are avoided. For reliability computations, some existing algorithms for finding network reliability can be used with minor modifications and no significant increase in computational complexity. 相似文献
58.
59.
DJ Benos BH Hahn JK Bubien SK Ghosh NA Mashburn MA Chaikin GM Shaw EN Benveniste 《Canadian Metallurgical Quarterly》1994,91(2):494-498
Infection by human immunodeficiency virus type 1 (HIV-1) is often complicated by a variety of neurological abnormalities. The most common clinical syndrome, termed acquired immunodeficiency syndrome (AIDS) dementia complex, presents as a subcortical dementia with cognitive, motor, and behavioral disturbances and is unique to HIV-1 infection. The pathogenesis of this syndrome is poorly understood but is believed to involve interactions among virally infected macrophages/microglia, astrocytes, and neurons. In this study, we show that exposure of primary rat and human astrocytes to heat-activated HIV-1 virions, or to eukaryotically expressed HIV-1 and HIV-2 envelope glycoproteins (gp120) stimulates amiloride-sensitive Na+/H+ antiport, potassium conductance, and glutamate efflux. These effects are blocked specifically by amiloride, an inhibitor of Na+/H+ antiport and by the selective removal of gp120 with immobilized monoclonal antibody. As a result of modulation of astrocytic function by gp120, the ensuing neuronal depolarization and glutamate exposure could activate both voltage-gated and N-methyl-D-aspartate-regulated Ca2+ channels, leading to increases in intraneuronal Ca2+ and neuronal death. These findings implicate the astrocyte directly in the pathogenesis of AIDS dementia complex. 相似文献
60.