全文获取类型
收费全文 | 25939篇 |
免费 | 2615篇 |
国内免费 | 1406篇 |
专业分类
电工技术 | 4088篇 |
技术理论 | 1篇 |
综合类 | 2708篇 |
化学工业 | 1505篇 |
金属工艺 | 1966篇 |
机械仪表 | 3357篇 |
建筑科学 | 1163篇 |
矿业工程 | 1240篇 |
能源动力 | 1396篇 |
轻工业 | 871篇 |
水利工程 | 517篇 |
石油天然气 | 781篇 |
武器工业 | 364篇 |
无线电 | 2441篇 |
一般工业技术 | 2198篇 |
冶金工业 | 1712篇 |
原子能技术 | 131篇 |
自动化技术 | 3521篇 |
出版年
2024年 | 100篇 |
2023年 | 322篇 |
2022年 | 608篇 |
2021年 | 677篇 |
2020年 | 829篇 |
2019年 | 621篇 |
2018年 | 634篇 |
2017年 | 843篇 |
2016年 | 965篇 |
2015年 | 1004篇 |
2014年 | 1643篇 |
2013年 | 1420篇 |
2012年 | 2000篇 |
2011年 | 2088篇 |
2010年 | 1468篇 |
2009年 | 1475篇 |
2008年 | 1325篇 |
2007年 | 1798篇 |
2006年 | 1556篇 |
2005年 | 1388篇 |
2004年 | 1058篇 |
2003年 | 1084篇 |
2002年 | 853篇 |
2001年 | 834篇 |
2000年 | 685篇 |
1999年 | 570篇 |
1998年 | 395篇 |
1997年 | 390篇 |
1996年 | 279篇 |
1995年 | 226篇 |
1994年 | 196篇 |
1993年 | 118篇 |
1992年 | 108篇 |
1991年 | 77篇 |
1990年 | 61篇 |
1989年 | 70篇 |
1988年 | 46篇 |
1987年 | 35篇 |
1986年 | 19篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1980年 | 4篇 |
1975年 | 3篇 |
1964年 | 5篇 |
1962年 | 6篇 |
1957年 | 4篇 |
1956年 | 4篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Biases in social comparative judgments, such as those illustrated by above-average and comparative-optimism effects, are often regarded as products of motivated reasoning (e.g., self-enhancement). These effects, however, can also be produced by information-processing limitations or aspects of judgment processes that are not necessarily biased by motivational factors. In this article, the authors briefly review motivational accounts of biased comparative judgments, introduce a 3-stage model for understanding how people make comparative judgments, and then describe how various nonmotivational factors can influence the 3 stages of the comparative judgment process. Finally, the authors discuss several unresolved issues highlighted by their analysis, such as the interrelation between motivated and nonmotivated sources of bias and the influence of nonmotivated sources of bias on behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125 相似文献
73.
关于气井产能、气田稳产特征和气区开采潜力的探讨 总被引:2,自引:0,他引:2
根据气田开发特点和国内外开发实践,对气田平均产能评价方法、开发速度与稳产的关系以及气区开采潜力等问题进行了探讨,以提高开发评价、开发建设及投资决策的科学性与可靠性,达到高效开发和稳定供气的目的。分析评价了国内外常用的6种气井产能评价方法,指出了其适用条件。利用中国、土库曼斯坦和俄罗斯部分开发历史较长的气田开发实例分析了开发速度与稳产的关系,结果表明四川裂缝系统稳产情况最好,而土库曼斯坦气田稳产关系最差。利用俄罗斯已枯竭老气区、正在开发的大型主力气区以及中国四川开采历史较长气区的开发实例,对气区开采潜力进行综合分析和探讨,认为在预测气田(或气区)的开发潜力、稳定供气水平和年限时,要全面评价、预计尚未探明储量的规模、质量、投产时间、投产顺序以及储量的可信度和可靠性,以降低开发决策的风险,提高中、长期开发规划的科学性。图5表2参10 相似文献
74.
概述污水处理厂的一般工艺,简单介绍了风机、水泵等的节能特点,介绍了变频调速装置在污水处理厂各处理工段的应用。 相似文献
75.
76.
Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation. 相似文献
77.
本文探讨了影响中厚板厚度波动的因素,结合安钢中板厂2800mm轧机按合同轧制一批交货重量不大于理论重量船板的生产实践,总结了实际生产中实现高精度厚度控制的有效方法。 相似文献
78.
Ideal-gas thermodynamic properties for natural-gas applications 总被引:2,自引:0,他引:2
Calculating caloric properties from a thermal equation of state requires information such as isobaric heat capacities in the ideal-gas state as a function of temperature. In this work, values for the parameters of thec
p
0
correlation proposed by Aly and Lee were newly determined for 21 pure gases which are compounds of natural gas mixtures. The values of the parameters were adjusted to selectedc
p
0
data calculated from spectroscopic data for temperatures ranging from 10 to 1000 K. The data sources used are discussed and compared with literature data deduced from theoretic models and caloric measurements. The parameters presented will be applied in a current GERG project for evaluating equations of state (e.g., the AGA 8 equation) for their suitability for calculating caloric properties. 相似文献
79.
本文针对天然气井提高钻井速度问题,总结分析了盆地中部井身结构,水力、机械参数,聚合物钻井液,正注反挤固井等工艺技术对该地区钻速的影响。指出提高天然气井钻井速度,必须搞好系统工程,形成配套技术。 相似文献
80.