全文获取类型
收费全文 | 81134篇 |
免费 | 6697篇 |
国内免费 | 3495篇 |
专业分类
电工技术 | 3751篇 |
技术理论 | 2篇 |
综合类 | 4368篇 |
化学工业 | 17024篇 |
金属工艺 | 4273篇 |
机械仪表 | 2829篇 |
建筑科学 | 4788篇 |
矿业工程 | 6504篇 |
能源动力 | 5734篇 |
轻工业 | 7097篇 |
水利工程 | 377篇 |
石油天然气 | 18098篇 |
武器工业 | 536篇 |
无线电 | 1670篇 |
一般工业技术 | 5628篇 |
冶金工业 | 6021篇 |
原子能技术 | 710篇 |
自动化技术 | 1916篇 |
出版年
2024年 | 286篇 |
2023年 | 1125篇 |
2022年 | 2114篇 |
2021年 | 2767篇 |
2020年 | 2902篇 |
2019年 | 2398篇 |
2018年 | 2177篇 |
2017年 | 2364篇 |
2016年 | 2813篇 |
2015年 | 2748篇 |
2014年 | 4745篇 |
2013年 | 4617篇 |
2012年 | 5924篇 |
2011年 | 6153篇 |
2010年 | 4262篇 |
2009年 | 4138篇 |
2008年 | 3546篇 |
2007年 | 4705篇 |
2006年 | 4982篇 |
2005年 | 4217篇 |
2004年 | 3622篇 |
2003年 | 3192篇 |
2002年 | 2753篇 |
2001年 | 2457篇 |
2000年 | 2084篇 |
1999年 | 1655篇 |
1998年 | 1335篇 |
1997年 | 1119篇 |
1996年 | 887篇 |
1995年 | 733篇 |
1994年 | 626篇 |
1993年 | 449篇 |
1992年 | 350篇 |
1991年 | 244篇 |
1990年 | 208篇 |
1989年 | 190篇 |
1988年 | 74篇 |
1987年 | 54篇 |
1986年 | 45篇 |
1985年 | 37篇 |
1984年 | 31篇 |
1983年 | 22篇 |
1982年 | 23篇 |
1981年 | 70篇 |
1980年 | 41篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 5篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
P. S. Lawson 《Biomass & bioenergy》1992,2(1-6):319-330
In recent years it has been recognised by an increasing number of nations that there is considerable energy potential within MSW. As a result many countries have established R,D& D programmes to examine methods of exploiting this potential. The IEA's MSW Conversion Activity was set up in 1986 to provide an infrastructure for sharing information and co-ordinating work in this area internationally. This Activity was extended in 1989 and currently a total of 9 nations participate in it.
To cope with the wide scope of the area (encompassing both biological and thermal processing of MSW) the Activity was divided into three subgroups or Expert Working Groups (EWGs). Each of these dealt with a distinct area of expertise:
- 1. •Downstream effects of source separation and screening of MSW
- 2. •Sampling and analytical protocols
- 3. •Landfill gas
In addition to these groups a central secretariat based at Harwell (UK) has provided guidance, established and administered databases of contacts and produced a series of national reports.
This paper describes the achievements of the Activity and discusses work proposed for the future. 相似文献
12.
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
13.
本文根据四川天然气产能建设多年的实践,分析了产能建设的特点和存在问题,着重强调了当前搞好产能建设应注意的几个问题,供决策和工作参考。 相似文献
14.
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
15.
用50W连续波CO_2激光器为热源,诱发SiH_4和C_2H_4反应,合成SiC超细粉末。实验确定了反应腔体内压力p、气源中的C/Si原子比、喷嘴内径2r以及激光功率密度与粉末特性之间的关系,并对合成的产物进行物理、化学表征。 相似文献
16.
17.
黄土塬区复杂的地表条件难以获得可供解释的物探资料,本文给出了勘探天然气的地震技术,在野外弯线地震数据采集中,冲沟区运用了弯线高分辨率技术;塬上区采用非纵测线和地震测深观测系统,大药量、深井和强化组合法的接收条件。初步解决了弯线地震资料处理中二维滤波、静校正、速度分析等技术难题。摸索出一套以地震为骨架,构造解释与岩性解释相结合,重力-电法-地震联合解释落实古生界天然气构造圈闭的综合物探解释技术,并以实例展示方法的有效性。 相似文献
18.
Flory–Huggins interaction parameters, λ, were determined for a series of probes in an amine cured epoxy resin matrix (433–493 K) and its precursors (324–363 K) by inverse gas chromatography (IGC). Hildebrand–Scatchard theory was combined with Flory–Huggins theory in order to estimate infinte dilution solubility parameters (δ2) for the matrix and its precursors at 298 K. It was shown that the value of the solubility parameter for the cured resin matrix lies between those of its precursors. Compared to the majority of published work, an unusual aspect of this application of IGC is that solubility parameters have been determined when the stationery phases are (i) small molecules and (ii) a highly crosslinked polymer. Moreover, all possible attempts have been made to ensure equilibrium conditions between probe and stationary phase, and compensation for asymmetry of peak profile has been applied in determining δ2. The solubility parameters estimated by IGC are in good agreement with those calculated by other methods. 相似文献
19.
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
20.
节流式差压流量计的发展和现状 总被引:2,自引:0,他引:2
文章介绍节流式差压流量计的特点及标准化进程,煤气流量测量中存在的难点以及正在试图解决的途径。 相似文献