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   568231篇
  免费   6244篇
  国内免费   1010篇
电工技术   10524篇
综合类   467篇
化学工业   90275篇
金属工艺   23404篇
机械仪表   18557篇
建筑科学   12540篇
矿业工程   4333篇
能源动力   14439篇
轻工业   45789篇
水利工程   6970篇
石油天然气   15012篇
武器工业   39篇
无线电   60374篇
一般工业技术   116587篇
冶金工业   95857篇
原子能技术   14791篇
自动化技术   45527篇
  2021年   5508篇
  2019年   5284篇
  2018年   9223篇
  2017年   9446篇
  2016年   9869篇
  2015年   6046篇
  2014年   10267篇
  2013年   26148篇
  2012年   15810篇
  2011年   21138篇
  2010年   17005篇
  2009年   18882篇
  2008年   19114篇
  2007年   18803篇
  2006年   16319篇
  2005年   14776篇
  2004年   14041篇
  2003年   13726篇
  2002年   13288篇
  2001年   12884篇
  2000年   12355篇
  1999年   12041篇
  1998年   27704篇
  1997年   20074篇
  1996年   15669篇
  1995年   12030篇
  1994年   10883篇
  1993年   10643篇
  1992年   8350篇
  1991年   8125篇
  1990年   8008篇
  1989年   7777篇
  1988年   7486篇
  1987年   6757篇
  1986年   6547篇
  1985年   7399篇
  1984年   6712篇
  1983年   6452篇
  1982年   5787篇
  1981年   5913篇
  1980年   5644篇
  1979年   5747篇
  1978年   5695篇
  1977年   6212篇
  1976年   7725篇
  1975年   5128篇
  1974年   4917篇
  1973年   5000篇
  1972年   4293篇
  1971年   4052篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The Fusion program, a method for agile, flexible computer integrated manufacturing (CIM) at Motorola's Paging Products Group, is discussed. Fusion's CIM and automated assembly system can manufacture a wide variety of different products on the same production line. The development of the Fusion program and how it differs from its predecessor, the Bandit program, are described  相似文献   
992.
A precoding scheme for noise whitening on intersymbol interference (ISI) channels is presented. This scheme is compatible with trellis-coded modulation and, unlike Tomlinson precoding, allows constellation shaping. It can be used with almost any shaping scheme, including the optimal SVQ shaping, as opposed to trellis precoding, which can only be used with trellis shaping. The implementation complexity of this scheme is minimal-only three times that of the noise prediction filter, hence effective noise whitening can be achieved by using a high-order predictor  相似文献   
993.
High-statistics (>4 × 108 counts), room-temperature measurements of the electron-positron momentum density of La2?x Sr x CuO4 have been performed for samples with Sr concentrations of x=0.0, 0.1, 0.13, and 0.2. These spectra have been analyzed in conjunction with theoretical calculations of the electron-positron momentum density. The metallic samples show features consistent with the presence of a Fermi surface, but its evolution with increasing Sr concentration does not follow the predictions of band theory. These results may indicate the effects of electron-electron correlation on the electron momentum distribution in the Cu-O plane.  相似文献   
994.
A case of histologically confirmed Paget's disease of the breast in a 72 year old man, without underlying breast carcinoma, is reported. This report raises questions about the pathogenesis of this condition and suggests that Paget's disease is an independent, intraepidermal carcinoma rather than a direct extension of intraductal carcinoma of the breast to the nipple and areola.  相似文献   
995.
We evaluated the effect of 4-(2-benzylphenoxy)-N-methylbutylamine hydrochloride (bifemelane hydrochloride) on superoxide production by human neutrophils using an MCLA-dependent chemiluminescence assay. Bifemelane hydrochloride dose-dependently inhibited superoxide production by neutrophils stimulated with phorbol myristate acetate, opsonized zymosan, or N-formyl-methionyl-leucyl-phenylalanine, while it had no effect on superoxide production by a hypoxanthine-xanthine oxidase system. These results indicate that bifemelane hydrochloride does not have a scavenging effect, but has an inhibitory effect on superoxide generation by neutrophils. Although this drug is commonly used for treating chronic cerebral infarction, it may also have a protective effect on acute ischemia/reperfusion injury.  相似文献   
996.
997.
A wideband low-noise pseudomorphic HEMT MMIC variable-gain amplifier has been designed and fabricated. The amplifier has a nominal gain of 13 dB across the band 2-20 GHz, with gain flatness better than ±0.4 dB. The noise figure is less than 3 dB across the band 6-16 GHz. An on-chip temperature-sensing diode is used to provide a linear temperature correction which has been used to reduce the gain variation of the amplifier by a factor of 2 across the temperature range -50°C to +95°C  相似文献   
998.
The effect of spreading code length on the BER performance of an asynchronous DS-CDMA system is studied by means of Monte Carlo simulation. The probability of the crosscorrelation value between segments of long sequences is also discussed. Results indicate that the system performance with very long codes is ~1 dB worse compared to that of short CDMA codes  相似文献   
999.
We report the implementation of a prototype three-dimensional (3D) optoelectronic neural network that combines free-space optical interconnects with silicon-VLSI-based optoelectronic circuits. The prototype system consists of a 16-node input, 4-neuron hidden, and a single-neuron output layer, where the denser input-to-hidden-layer connections are optical. The input layer uses PLZT light modulators to generate optical outputs which are distributed over an optoelectronic neural network chip through space-invariant holographic optical interconnects. Optical interconnections provide negligible fan-out delay and allow compact, purely on-chip electronic H-tree type fan-in structure. The small prototype system achieves a measured 8-bit electronic fan-in precision and a calculated maximum speed of 640 million interconnections per second. The system was tested using synaptic weights learned off system and was shown to distinguish any vertical line from any horizontal one in an image of 4×4 pixels. New, more efficient light detector and small-area analog synapse circuits and denser optoelectronic neuron layouts are proposed to scale up the system. A high-speed, feed-forward optoelectronic synapse implementation density of up to 104/cm2 seems feasible using new synapse design. A scaling analysis of the system shows that the optically interconnected neural network implementation can provide higher fan-in speed and lower power consumption characteristics than a purely electronic, crossbar-based neural network implementation  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