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   76046篇
  免费   819篇
  国内免费   729篇
电工技术   1455篇
综合类   94篇
化学工业   11420篇
金属工艺   3511篇
机械仪表   2727篇
建筑科学   1720篇
矿业工程   534篇
能源动力   1930篇
轻工业   6480篇
水利工程   875篇
石油天然气   2332篇
武器工业   41篇
无线电   7364篇
一般工业技术   16612篇
冶金工业   12464篇
原子能技术   2659篇
自动化技术   5376篇
  2022年   627篇
  2021年   976篇
  2020年   762篇
  2019年   809篇
  2018年   1592篇
  2017年   1602篇
  2016年   1808篇
  2015年   986篇
  2014年   1613篇
  2013年   3641篇
  2012年   2429篇
  2011年   2904篇
  2010年   2432篇
  2009年   2710篇
  2008年   2678篇
  2007年   2585篇
  2006年   2215篇
  2005年   1950篇
  2004年   1884篇
  2003年   1835篇
  2002年   1770篇
  2001年   1734篇
  2000年   1697篇
  1999年   1581篇
  1998年   3685篇
  1997年   2613篇
  1996年   1939篇
  1995年   1525篇
  1994年   1331篇
  1993年   1353篇
  1992年   997篇
  1991年   1053篇
  1990年   1072篇
  1989年   1053篇
  1988年   942篇
  1987年   877篇
  1986年   878篇
  1985年   935篇
  1984年   778篇
  1983年   768篇
  1982年   675篇
  1981年   691篇
  1980年   661篇
  1979年   647篇
  1978年   620篇
  1977年   774篇
  1976年   933篇
  1975年   583篇
  1974年   551篇
  1973年   545篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Journal of Communications Technology and Electronics - An approach to building a multichannel pattern-recognition system by sensing systems is proposed. A list of problems solved by the sensing...  相似文献   
992.
The effect of the oxygen content (\(C_{O_2 } \)) in the gas mixture (20% of SiH4 + 80% of Ar) + O2 and the surface area of an erbium target (SEr) on the composition and Er3+ photoluminescence of amorphous a-SiOx:(H, Er, O) films prepared by dc magnetron sputtering has been investigated. Analysis of the experimental data shows that [Er-O] and [Er-O-Si-O] clusters are formed in the gas plasma due to the competing processes of oxidation and sputtering of Si and Er targets and to the interaction of [Si-O] and [Er-O] clusters with each other and with the oxygen in the gas phase. The discontinuities in the dependences of the contents of erbium-bound oxygen and erbium in a film, and N O Er-O and NEr = f(\(C_{O_2 } \), SEr), at \(C_{O_2 } \) ≈ (5–6.5) mol % supports the hypothesis on the existence of different erbium clusters. The necessary conditions for preparing a-SiOx:(H, Er, O) films with the highest photoluminescence intensity of erbium ions at a wavelength of 1.54 μm are determined.  相似文献   
993.
994.
Dry yambean seeds, prior to soaking and during storage treatments, were moist cooked and autoclaved. Seeds, presoaked in water, sodium chloride (brine), as filterate (alkali) and a mixture of brine and alkali (alkalibrine) were also similarly cooked. Water and alkali-soaked seeds became hydrated faster than those pre-soaked in brine and alkali-brine solution. When cooked under constant temperature conditions the untreated yambean took about 190 min to cook on a hot plate and kerosene stove and 65 min by autoclaving. Soaking treatments substantially rendered dry yambean more quick-cooking, especially when pre-contacted in brine or alkali-brine for which cooking time was about a third of that of un-soaked seeds. Yambean cook-ability declined by 9% after 3 months in storage under room temperature (29 °C).  相似文献   
995.
Dried and defatted, water extracted and hydrogen peroxide treated silk worm chrysalides (SWC) were analysed for gross composition as well as for energy, fatty acids and amino acids. The amino acid analyses showed well-balanced amino acid patterns. Water extraction and hydrogen peroxide treatment improved odour, taste and colour of the product. Tests with rats showed that raw and water extracted SWC were well utilised whereas hydrogen peroxide treated SWC showed reduced protein utilisation. It is concluded that the water extracted SWC is better suited for eventual use as a food component than the hydrogen peroxide treated SWC.  相似文献   
996.
Changes in biochemical properties of myofibrillar proteins of rabbit muscle, which had been subjected to electrical stimulation soon after slaughter, during postmortem storage at 0°C were investigated. Myofibrillar ATPase activity and the ATPase activity of acto-heavy meromyosin (HMM) complex, reconstituted from actin and HMM which had been prepared from at-death and postmortem muscles, decreased at first and then increased slightly during 7 days storage. In addition, the change of the dissociation constant of acto-HMM complex of electrically stimulated muscle during postmortem storage was quite small, i.e., 1.59 ± 10?4M for at-death muscle, 1.70 ± 10?4M for muscle stored for 1 day and 1.49 ± 10?4M for muscle stored for 7 days. This indicates that electrical stimulation treatment minimized the postmortem change of actin-myosin interaction.  相似文献   
997.
Kang JO  Ito T  Fukazawa T 《Meat science》1983,9(2):131-144
The effect of frozen storage on the biochemical properties of myofibrils, and of their major constituents, actin and myosin, was investigated. Extractability of myofibrillar proteins increased slightly for 3 weeks during frozen storage of muscle, decreasing thereafter. The change in myofibrillar ATPase activity during frozen storage was consistent with that of a reconstituted acto-heavy meromyosin (HMM) complex prepared from frozen stored muscle at the same weight ratio of actin to myosin as in situ. However, myosin ATPase activity showed a different pattern of change when compared with myofibrillar ATPase activity. The maximum velocity of acto-HMM ATPase activity and the apparent dissociation constant of the acto-HMM complex decreased for 1 week during frozen storage, increasing thereafter, indicating that the affinity of actin for myosin was greatest in muscle which had been frozen for 1 week.  相似文献   
998.
Leaf protein concentrates (LPC) were prepared in large pilot plant equipment from seven Brassica varieties grown on plots of up to 0.06 ha. Plants were harvested about a month before and after the lucerne processing season. Best yields of LPC, from leafier or forage-type species, were up to 0.9 t ha?1. Properties were as good as or better than those of LPC from lucerne. Lucerne processing procedures were modified to maximize yields from the more succulent Brassica plants.  相似文献   
999.
We design and implement an efficient on-line approach, FlowMate, for clustering flows (connections) emanating from a busy server, according to shared bottlenecks. Clusters can be periodically input to load balancing, congestion coordination, aggregation, admission control, or pricing modules. FlowMate uses in-band (passive) end-to-end delay measurements to infer shared bottlenecks. Delay information is piggybacked on feedback from the receivers, or, if impossible, TCP or application round-trip time estimates are used. We simulate FlowMate and examine the effects of network load, traffic burstiness, network buffer sizes, and packet drop policies on clustering correctness, evaluated via a novel accuracy metric. We find that coordinated congestion management techniques are more fair when integrated with FlowMate. We also implement FlowMate in the Linux kernel v2.4.17 and evaluate its performance on the Emulab testbed, using both synthetic and tcplib-generated traffic. Our results demonstrate that clustering of medium to long-lived flows is accurate, even with bursty background traffic. Finally, we validate our results on the Internet Planetlab testbed.  相似文献   
1000.
In the context of the thermodynamics of irreversible processes, general expressions for the temperature dependence of the thermoelectric power in the region of hopping conductivity in disordered materials at low temperatures are derived. The effect of degeneracy of impurity levels on the thermoelectric power is taken into account. On the basis of the results, the experimental data on the thermoelectric power in amorphous and impurity-containing semiconductors are discussed.  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