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   22283篇
  免费   2126篇
  国内免费   948篇
电工技术   1223篇
综合类   1050篇
化学工业   3722篇
金属工艺   1494篇
机械仪表   1658篇
建筑科学   1284篇
矿业工程   625篇
能源动力   824篇
轻工业   1529篇
水利工程   314篇
石油天然气   962篇
武器工业   118篇
无线电   2979篇
一般工业技术   3607篇
冶金工业   1239篇
原子能技术   187篇
自动化技术   2542篇
  2024年   96篇
  2023年   453篇
  2022年   728篇
  2021年   1156篇
  2020年   846篇
  2019年   683篇
  2018年   836篇
  2017年   783篇
  2016年   807篇
  2015年   927篇
  2014年   1111篇
  2013年   1362篇
  2012年   1450篇
  2011年   1615篇
  2010年   1388篇
  2009年   1356篇
  2008年   1232篇
  2007年   1022篇
  2006年   978篇
  2005年   866篇
  2004年   666篇
  2003年   645篇
  2002年   596篇
  2001年   504篇
  2000年   474篇
  1999年   474篇
  1998年   458篇
  1997年   355篇
  1996年   329篇
  1995年   261篇
  1994年   210篇
  1993年   139篇
  1992年   114篇
  1991年   76篇
  1990年   74篇
  1989年   63篇
  1988年   42篇
  1987年   33篇
  1986年   32篇
  1985年   22篇
  1984年   14篇
  1983年   9篇
  1982年   8篇
  1981年   14篇
  1980年   10篇
  1979年   5篇
  1978年   6篇
  1977年   6篇
  1976年   10篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
141.
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.  相似文献   
142.
噻二唑二聚物/丁氧基三乙二醇复合物的合成   总被引:4,自引:0,他引:4  
合成了噻二唑二聚物/丁氧基三乙二醇复合物。反应物的摩尔比及反应温度影响产物作为添加剂加入到润滑脂中的抗烧结性能。在最佳反应条件下,即n(噻二唑二聚物)∶n(丁氧基三乙二醇)=0.5∶1.0,反应温度125℃时,产率为85%。通过分子模拟、红外光谱、13C核磁共振及N、S元素的含量测定,探讨了产物的结构及反应机理。结果表明,噻二唑二聚物与丁氧基三乙二醇的摩尔比越大,在金属表面形成配位的噻二唑环的个数就越多,就会表现出更强的吸附特性,从而表现出更高的抗烧结性能。  相似文献   
143.
In a complex social, political, economic, technological, and/or environmental context, corporate, military, government, and other organizations are often faced with collective decision-making situations. The rationale for group decision exercises is that the judgment of many will usually prove superior to the judgment of one. However, it has been shown that collective decision exercises are often highly dependent on matters of perspective, values and opinion, all of which - being essentially subjective in nature - are beyond the reach of existing formal decision technology. Furthermore, it can be expected that many collective decision exercises - particularly those of strategic import - will not lend themselves to the quantitative analysis instruments that have long dominated the management and decision science repertoire. This does not, however, mean that they must remain entirely and forever outside the bounds of scientific rationality. The ordering protocols which are currently available do not have enough technical mechanics to be relied upon to bring us to any satisfying resolution of a priori disputation. Hence, we propose an a priori ordering reference model that might support consensus-building in a multiple stakeholders context. In order to detect whether the subjective arguments are products of proper reasons or merely instances of raw rhetoric and to suggest how any logical or syntactical flaws might best be repaired, we propose logical ordering facilities and protocols for integrating procedural and instrumental provisions for a group-decision process with two lines of technical innovation: the superimpositional ordering function and the logical ordering support facilities.  相似文献   
144.
In this letter, we examined whether the parasitic bipolar junction transistors (BJTs) in the MOSFET fabricated by the standard CMOS process can play a role as a fluorescence detector. To suppress the action of two vertical parasitic BJTs, the gate and n-well were tied in the parasitic BJTs, and the body node was connected to the drain. The proposed device was compared with the inherent and the parasitic diodes in the MOSFET. It had 100 times higher photocurrents than the diodes in the MOSFET. In addition, it was applied for the detection of the fluorescent signal, and could detect near 10 nM of Alexa 546. Therefore, CMOS-process-compatible parasitic BJTs can be used as a photodetector in an integrated fluorescence detector.  相似文献   
145.
A novel bidirectional complementary metal-oxide-semiconductor (CMOS) transceiver for chip-to-chip optical interconnects operating at 2.5 Gb/s is proposed, which shares the common block of a receiver and a transmitter on a single chip. The share of the common block of two circuits makes it possible to save 55% or 20% of power dissipation, depending on the operating mode. The chip in 0.18-/spl mu/m CMOS technology occupies an area of 0.82/spl times/0.82 mm/sup 2/, 70% of the total area of a typical unshared transceiver chip. The transmitting and receiving modes of operation show -3-dB bandwidths of 2.2 and 2.4 GHz and electrical isolations of -28 and -40 dB, respectively.  相似文献   
146.
    
“悟”是一种对客观的事和物的一种感知,是对事和物获取了解、获取知效,是人们求得理解的一种启示、一种认识的过程。一般地说,“我对事和物,意在彻悟”,是指人们得到充分的悟性,特别对意、意义的悟,有的很快领会,有的要耗费时日,有的要经过一定的时间乃至终身。悟性就是理解的  相似文献   
147.
“对于建筑事业,没有什么比让全民的建筑意识提高更重要的事情了。”五十多年前,年轻的齐康对此深信不疑,如今已是古稀之年的齐老对此仍然耿耿于怀。对于青年一代的教育,他从未放松;传统与现代的比较、东方与西方差异的研究,他从未停止。从本期起,我们将连续刊登齐康系列文章《建筑课》。  相似文献   
148.
力量空间     
设计师做自己办公空间设计往往想法很多,也很苛求。这种设计状态会令将来的作品显得杂乱、稚嫩, 容易出现“昏招”,或者流于刻板、拘谨、不灵动。我懂得调整自己的状态:有时记住自己是甲方,可以任意发挥,有时把它忘了,也就不必太苛求,以致经常改动设计,不坚决。由于急于搬迁的缘故,加之那时我正好出差在外,所以本案设计周期较短。几天时间在宾馆里伏案设计,倒给出了一个好的状态:略去许多泉涌的想法, 只抓住最好的,好比画者在做速写,把控大局。凭我个人的喜好和习惯,以及对设计公司办公空间的理解与思考,我在凝神中拔高自己,发现塑造一种力量空间会比较接近于表达设计师这种群体的周遭环境,无需过多地出招,无需捕捉人的眼球。力量是潜在的,它无处不在,闭着眼也能抓住你的心。我就这样确立了设计主旨。  相似文献   
149.
Fresh persimmons were subjected to two different processes: sun-drying during 1 month and dehydration at 60 °C during 12 h. To assess the effect of this process on nutritional and health-related properties of persimmons dietary fibers, minerals, trace elements, polyphenols and the total radical scavenging activities (TRSAs) were determined before and after processing. It was found that the contents of dietary fibers, minerals and trace elements in fresh and dried persimmons fruits were comparable. Total polyphenols in fresh persimmons was higher than in dried fruits (1.3 vs. 0.9 and 0.8 mg/100 g FW, respectively) and percentage of inhibition was higher than in dried fruits (70% vs. 59% and 55% and 58% vs. 53% and 46% for 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) [ABTS] radicals, respectively (P>0.05 in all cases). In conclusion: (1) the differences in the contents of dietary fibers, minerals and trace elements in fresh and dried persimmons are not significant; (2) the contents of polyphenols and the level of the TRSA are higher in fresh persimmons than in dried fruits; however, both variables are also high in dried persimmons; (3) when fresh fruits are not available, proper dried persimmons could be used as a valuable substitute.  相似文献   
150.
Destination-driven routing for low-cost multicast   总被引:19,自引:0,他引:19  
We present a destination-driven algorithm that optimizes for applications, such as group video or teleconferencing, that require multicast trees with low total cost. The destination-driven algorithm uses a greedy strategy based on shortest-path trees and minimal spanning trees but biases routes through destinations. The performance of the algorithm is analyzed through extensive simulation and compared with several Steiner tree heuristics and the popular shortest-path tree (SPT) method. The algorithm is found to produce trees with significantly lower overall cost than the SPT while maintaining reasonable per-destination performance. Its performance also compares well with other known Steiner heuristics. Moreover, the algorithm does not suffer from high complexity common to most Steiner tree heuristics and builds a route by querying only incident links for cost information  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