全文获取类型
收费全文 | 12861篇 |
免费 | 1000篇 |
国内免费 | 732篇 |
专业分类
电工技术 | 206篇 |
综合类 | 966篇 |
化学工业 | 2267篇 |
金属工艺 | 793篇 |
机械仪表 | 359篇 |
建筑科学 | 610篇 |
矿业工程 | 691篇 |
能源动力 | 493篇 |
轻工业 | 708篇 |
水利工程 | 203篇 |
石油天然气 | 4377篇 |
武器工业 | 165篇 |
无线电 | 408篇 |
一般工业技术 | 869篇 |
冶金工业 | 525篇 |
原子能技术 | 114篇 |
自动化技术 | 839篇 |
出版年
2024年 | 56篇 |
2023年 | 175篇 |
2022年 | 341篇 |
2021年 | 383篇 |
2020年 | 412篇 |
2019年 | 317篇 |
2018年 | 302篇 |
2017年 | 377篇 |
2016年 | 400篇 |
2015年 | 374篇 |
2014年 | 603篇 |
2013年 | 867篇 |
2012年 | 774篇 |
2011年 | 851篇 |
2010年 | 653篇 |
2009年 | 677篇 |
2008年 | 594篇 |
2007年 | 716篇 |
2006年 | 785篇 |
2005年 | 691篇 |
2004年 | 575篇 |
2003年 | 547篇 |
2002年 | 502篇 |
2001年 | 453篇 |
2000年 | 359篇 |
1999年 | 321篇 |
1998年 | 263篇 |
1997年 | 221篇 |
1996年 | 201篇 |
1995年 | 170篇 |
1994年 | 120篇 |
1993年 | 84篇 |
1992年 | 65篇 |
1991年 | 61篇 |
1990年 | 74篇 |
1989年 | 52篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 17篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1977年 | 3篇 |
1964年 | 5篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
南哨水电站位于雷公山暴雨中心区, 洪水峰高量大, 水库基本无滞洪削峰, 由于坝址处河床深切而狭窄, 溢洪道作拱坝坝身表孔溢流短鼻坎挑流的布置。为使溢洪道既有较好的挑流消能效果, 又能达到控制大坝工程投资的双重目的, 将混凝土拱坝体型作了一反常规的设计布置, 即河床部分悬臂梁的上部向水库倒悬呈负坡, 岸边悬臂梁渐变为竖直呈正坡; 水平拱圈曲率由高到低逐渐变小, 而曲率半径则逐渐加大。拱坝的体型适应了溢洪道作高落差挑流鼻坎的布置, 使其溢洪舌远离坝脚, 经运行13 年来多次洪水的检验, 在下游不做消能防冲工程措施的情况下, 保证了大坝和下游两岸岩体的稳定安全, 而大坝和溢洪道运行状态良好。 相似文献
32.
33.
Standard Gibbs free energy of formation (ΔGf0), an important property needed in design calculations has been estimated using molar refraction, RM. The linear relationships derived between ΔGf0 and RM tested with the data on 8 series of hydrocarbons at 228 compounds yielded average deviations comparable to the methods cited in recent literature. The method can be used as an alternative to the existing ones, because of its simplicity combined with reasonable accuracy. 相似文献
34.
This paper discusses the seafloor thermalwater spout sedimentary activity in South Yongmei Depression according to the following
evidences: the Yongmei region was in an extended tectonic environment of metaplateform and locally developed intracontinental
rift aulacogen in company with the activity of rich alkali, high potassium volcanics of double-peak type. Several kinds of
hydrothermal sedimentary rocks and the ore-bearing sedimentary formations of copper-polymetals, iron and manganese exist in
this region with a zoning feature of the seafloor thermalwater spout sedimentation.
Project supported by the Science Foundation of NECC for Returns
Synopsis of the first author Wu Chengjian, associated professor, born in 1957, majoring in ore deposit and mineralgraphy. 相似文献
35.
Convection promotion within a tubular ceramic membrane by using the kenics static mixer is studied. The experiments were carried out with aqueous solutions of pectin and sodium carboxymethylcellulose (CMC), for Reynolds number in the range of 60-5000. From the results of these experiments it can be concluded that the presence of convection promotor decreasing the concentration of the gel layer. The experimental data are correlated satisfactorily by the equation of the general form Sh=A ReaScb. 相似文献
36.
Rates of coke formation during steam pyrolysis of naphtha have been investigated in a jet-stirred reactor both for sodium silicate coated and uncoated Inconel 600 surfaces in the temperature range of 1078–1108 K. Coke formation rates were significantly reduced on sodium silicate coated plates due to the passivation of the metal surface. However, the coking rates gradually increased with successive decokings of the coated surface. 相似文献
37.
本文简要介绍了国外在开发超酸性气体过程中遇到的材料选择、腐蚀监测、水化物堵塞、超酸性气的处理和加工等问题所采取的措施和办法。 相似文献
38.
39.
高含酸性气碳酸盐岩气藏流体敏感性实验研究 总被引:2,自引:0,他引:2
对川东北雷口坡组、嘉陵江组、飞仙关组、长兴组高含H,S及032的碳酸盐岩储层流体敏感性进行了实验研究,结果表明岩样速敏损害弱~强,水敏和盐敏损害中偏弱~极强,碱敏损害严重。岩石学分析揭示,川东北高含酸性气碳酸盐岩储层发育伊利石、微晶石英、白云石、方解石、硫化钙等潜在损害物质。钻井完井液侵入会破坏储层各物质间的原始动态平衡,诱发储层损害。主要损害机理为:①储层流体pH增加引起黏土矿物以及微晶石英失稳;②碱液与微晶石英、长石、白云石反应生成硅酸盐、高岭石、水镁石等新矿相;③流体矿化度改变可降低伊利石微粒间的连接力;④硫化钙水解产生OH^-,过量的OH-与Ca^2+结合形成氢氧化钙沉淀;⑤储层含水饱和度和流体离子浓度改变,致使焦沥青脱附并在储层深部沉积;⑥硬石膏水化膨胀、分散运移。针对该气藏损害机理,可采用屏蔽暂堵技术以形成优质滤饼,有效降低储层流体敏感性损害。图5表2参10。 相似文献
40.
Kazutaka Chibana Chaedong Kang Masashi Okada Koji Matsumoto Tetsuo Kawagoe 《International Journal of Refrigeration》2002,25(2):83
Water-silicone oil emulsion with an additive, (C2H5O)3SiC3H6NH2, was examined as a heat storage material. A spiral tube used as a heat exchanger was immersed in a low temperature bath and the emulsion was circulated in the tube to make ice continuously. Ice was separated from the ice–liquid suspension in an outlet tank. The amount of formed ice, the temperatures of the inlet and the outlet of the heat exchanger, and the temperatures in the tube wall were measured and the overall heat transfer coefficient and the heat flux through the tube were calculated. Experiments were carried out, varying the flow rate, the temperature of cooling brine, and the thickness of tube wall. The condition under which slurry ice was formed continuously without adhesion of ice to the cooling wall was clarified. Though decrease in the thermal resistance of the tube increased the rate of ice formation or raised the brine temperature, it narrowed the range of the flow rate and of the brine temperature in which slurry ice was formed continuously. 相似文献