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   8957篇
  免费   337篇
  国内免费   37篇
电工技术   122篇
综合类   22篇
化学工业   2077篇
金属工艺   167篇
机械仪表   230篇
建筑科学   572篇
矿业工程   31篇
能源动力   172篇
轻工业   775篇
水利工程   54篇
石油天然气   10篇
武器工业   1篇
无线电   589篇
一般工业技术   1446篇
冶金工业   1520篇
原子能技术   70篇
自动化技术   1473篇
  2023年   51篇
  2022年   87篇
  2021年   142篇
  2020年   104篇
  2019年   120篇
  2018年   168篇
  2017年   110篇
  2016年   191篇
  2015年   191篇
  2014年   249篇
  2013年   563篇
  2012年   397篇
  2011年   547篇
  2010年   410篇
  2009年   389篇
  2008年   432篇
  2007年   422篇
  2006年   365篇
  2005年   312篇
  2004年   292篇
  2003年   222篇
  2002年   228篇
  2001年   174篇
  2000年   165篇
  1999年   157篇
  1998年   258篇
  1997年   194篇
  1996年   159篇
  1995年   140篇
  1994年   122篇
  1993年   136篇
  1992年   131篇
  1991年   75篇
  1990年   92篇
  1989年   79篇
  1988年   95篇
  1987年   66篇
  1986年   54篇
  1985年   81篇
  1984年   94篇
  1983年   61篇
  1982年   66篇
  1981年   83篇
  1980年   70篇
  1979年   86篇
  1978年   68篇
  1977年   67篇
  1976年   56篇
  1975年   58篇
  1973年   48篇
排序方式: 共有9331条查询结果,搜索用时 31 毫秒
51.
The Kernighan/Lin graph partitioning heuristic, also known as min-cut or group migration, has been extended over several decades very successfully for circuit partitioning. Those extensions customized the heuristic and its associated data structure to rapidly compute the minimum-cut metric central to circuit partitioning; as such, those extensions are not directly applicable to other problems. In this paper, we extend the heuristic for functional partitioning, which in turn can solve the much investigated codesign problem of partitioning a system's coarse-grained functions among hardware and software components. The key extension customizes the heuristic and data structure to rapidly compute execution-time and communication metrics, crucial to hardware and software partitioning, and leads to near-linear time-complexity and excellent resulting quality. Another extension uses a new criteria for terminating the heuristic, eliminating time-consuming and unnecessary fine-tuning of a partition. Our experiments demonstrate extremely fast execution times (just a few seconds) with results matched only by the slower simulated annealing heuristic, meaning that the extended Kernighan/Lin heuristic will likely prove hard to beat for hardware and software functional partitioning.  相似文献   
52.
53.
The effect of sodium sulfate on the solidification/stabilization of a large quantity of a synthetic electroplating sludge in cementitious binders was s  相似文献   
54.
55.
Examined distributions of estimates of the dollar value of performance in studies employing the method of F. L. Schmidt et al (1979) for estimating the standard deviation of job performance (SDy) and found evidence that (1) the mean 50th percentile estimate is biased downward, (2) estimates of SDy appear to be a constant percentage of the 50th percentile estimate, and (3) estimates of SDy as a percentage of the 50th percentile value (SDp) are quite similar to empirical SDp values based on actual employee output. These findings suggest that the downward bias in the mean estimate of the 50th percentile causes the mean estimates of SDy to be similarly biased downward, but does not bias the estimates of SDp. Finally, an objective method for estimating the value of average employee output is described. The product of this value and the mean supervisory estimate of SDp yields an unbiased estimate of SDy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
56.
We have used the technique of antibody reshaping to producea humanized antibody specific for the a toxin of Clostridiumperfringens. The starting antibody was from a mouse hybridomafrom which variable (V) region nucleo-tide sequences were determined.The complementarity-determining regions (CDRs) from these Vregions were then inserted into human heavy and light chainV region genes with human constant region gene fragments subsequentlyadded. The insertion of CDRs alone into human frameworks didnot produce a functional reshaped antibody and modificationsto the V region framework were required. With minor frameworkmodifications, the affinity of the original murine mAb was restoredand even exceeded. Where affinity was increased, an alteredbinding profile to overlapping peptides was observed. Computermodelling of the reshaped heavy chain V regions suggested thatamino acids adjacent to CDRs can either contribute to, or distort,CDR loop conformation and must be adjusted to achieve high bindingaffinity.  相似文献   
57.
We have measured the heat capacities of3He films and liquid3He in porous Vycor glass at 10 to 600 mK. With increasing the film thickness from 1 to 3 atomic layers, the specific heat evolves gradually from that typical to solid to that of liquid3He. At about 2 atomic layers, however, its low-temperature part is nearly temperature-independent; we interpret this as a result of gradual freezing of spins in an amorphous solid3He film with decreasing the temperature. The contribution of liquid3He in the center of the Vycor pores can be described as the specific heat of bulk liquid3He at corresponding pressures in the range 0 to 28 bar. The thickness of amorphous solid on the pore walls increases with external pressure roughly linearly. Preplating the walls with4He allows to determine the positions of3He atoms contributing to the surface specific heat at 10 to 50 mK. In addition, the contribution from the specific heat of3 He -4He mixing at 100 to 600 mK is discussed as a function of pressure and amount of4He.0n leave from ISSP Acad. Sci. of Russia, Chernogolovka, Russia  相似文献   
58.
Ultrafiltration and thermization of milk on dairy farms in France have been under study since 1979. More recently five dairy farms in Brittany have been routinely producing 2:1 whole milk retentate for Emmental and St. Paulin cheese making. The milk processed is ultrafiltered at 35°C and thermized at 72°C for 15 s in an Ultratherm unit. Cheese quality generally appears satisfactory.In Eastern France a new specialty cheese industry has been started utilizing 4.5:1 whole milk retentate produced by ultrafiltration conducted at 40°C. The specialty cheese attains its characteristic white surface from Penicillium album mold. It has a bland, nutty flavor and very soft, smooth texture. A surface bluing phenomenon occurs after 14 d.  相似文献   
59.
着重介绍Raychem电路保护部的PolySwitch PPTC(聚合物正温度系数)元件在电源管理中提供电流过载和温度过载的保护过程。另外还介绍了电源适配器、CLA(点烟器)、移动电话设备及电池板的保护装置是如何进一步改善实际使用中的总体可靠性的。  相似文献   
60.
Nickel molybdate catalysts used in several different upgrading reactions of coal-derived materials from low-rank Australian coals have been regenerated and their activity assessed using a number of physical and chemical techniques. Regeneration of spent coked catalysts for 20 hours in air at 450°C was sufficient to restore chemical hydrogenation activity to catalyst used for pre-asphaltene, asphaltene and oil upgrading, provided poisoning of the catalyst surface by other impurities, principally chlorine-containing molecules, had not occurred.  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