全文获取类型
收费全文 | 60842篇 |
免费 | 6569篇 |
国内免费 | 4143篇 |
专业分类
电工技术 | 8280篇 |
技术理论 | 2篇 |
综合类 | 6239篇 |
化学工业 | 4264篇 |
金属工艺 | 4915篇 |
机械仪表 | 5953篇 |
建筑科学 | 3516篇 |
矿业工程 | 2785篇 |
能源动力 | 3005篇 |
轻工业 | 1934篇 |
水利工程 | 1636篇 |
石油天然气 | 5788篇 |
武器工业 | 919篇 |
无线电 | 6877篇 |
一般工业技术 | 5963篇 |
冶金工业 | 2988篇 |
原子能技术 | 816篇 |
自动化技术 | 5674篇 |
出版年
2024年 | 284篇 |
2023年 | 854篇 |
2022年 | 1558篇 |
2021年 | 1749篇 |
2020年 | 1885篇 |
2019年 | 1560篇 |
2018年 | 1474篇 |
2017年 | 2085篇 |
2016年 | 2196篇 |
2015年 | 2378篇 |
2014年 | 3550篇 |
2013年 | 3260篇 |
2012年 | 4475篇 |
2011年 | 4809篇 |
2010年 | 3493篇 |
2009年 | 3518篇 |
2008年 | 3203篇 |
2007年 | 4150篇 |
2006年 | 3834篇 |
2005年 | 3292篇 |
2004年 | 2676篇 |
2003年 | 2569篇 |
2002年 | 2071篇 |
2001年 | 1824篇 |
2000年 | 1685篇 |
1999年 | 1407篇 |
1998年 | 1049篇 |
1997年 | 955篇 |
1996年 | 807篇 |
1995年 | 641篇 |
1994年 | 562篇 |
1993年 | 351篇 |
1992年 | 287篇 |
1991年 | 219篇 |
1990年 | 199篇 |
1989年 | 217篇 |
1988年 | 125篇 |
1987年 | 68篇 |
1986年 | 39篇 |
1985年 | 29篇 |
1984年 | 34篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1962年 | 7篇 |
1959年 | 9篇 |
1955年 | 5篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
本文采用粘滞流模型试验对青海桥头电厂河子沟灰场拦洪坝设计方案进行了论证,分析了多种防渗条件下的渗流场特点,提出了满足工程运作的既经济又合理的建议。 相似文献
63.
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
64.
基于物质平衡方程、产能方程和递减方程的结合,提出了定容气田开发规划的概算法.该法可用于预测地层压力、井底流动压力、井口流动压力和稳产年限.实际应用表明,本文提供的方法是实用有效的. 相似文献
65.
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
66.
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
67.
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
68.
Satoshi Takeuchi Ryo Sugihara 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1998,410(3):104-508
The longitudinal electric field of single and double Gaussian laser beams are used to accelerate electrons. The longitudinal field of the single beam is concentrated on the axis and is favourable for acceleration. A set of two beams is considered. Beams run parallel, collinearly, overlap partially and have a phase difference iπ in between. As a result, the transverse components of fields cancel each other while the longitudinal components are double-fold. In both schemes, the electrons are accelerated in lengths of the Rayleigh range, which is common to the plasma-based accelerators. 相似文献
69.
70.
StudyonFactorsAffectingtheStructureofHighSpeedSteelIngotProducedbyESRLiZhengbang;CheXiangqianAbstract:Theinfluenceofthemetalp... 相似文献