全文获取类型
收费全文 | 10374篇 |
免费 | 1158篇 |
国内免费 | 584篇 |
专业分类
电工技术 | 178篇 |
技术理论 | 4篇 |
综合类 | 872篇 |
化学工业 | 285篇 |
金属工艺 | 20篇 |
机械仪表 | 86篇 |
建筑科学 | 1591篇 |
矿业工程 | 135篇 |
能源动力 | 470篇 |
轻工业 | 102篇 |
水利工程 | 6874篇 |
石油天然气 | 460篇 |
武器工业 | 2篇 |
无线电 | 64篇 |
一般工业技术 | 167篇 |
冶金工业 | 329篇 |
原子能技术 | 36篇 |
自动化技术 | 441篇 |
出版年
2024年 | 54篇 |
2023年 | 188篇 |
2022年 | 373篇 |
2021年 | 386篇 |
2020年 | 433篇 |
2019年 | 459篇 |
2018年 | 353篇 |
2017年 | 422篇 |
2016年 | 448篇 |
2015年 | 400篇 |
2014年 | 564篇 |
2013年 | 538篇 |
2012年 | 742篇 |
2011年 | 903篇 |
2010年 | 605篇 |
2009年 | 537篇 |
2008年 | 547篇 |
2007年 | 617篇 |
2006年 | 616篇 |
2005年 | 517篇 |
2004年 | 423篇 |
2003年 | 317篇 |
2002年 | 277篇 |
2001年 | 217篇 |
2000年 | 188篇 |
1999年 | 161篇 |
1998年 | 109篇 |
1997年 | 116篇 |
1996年 | 123篇 |
1995年 | 77篇 |
1994年 | 97篇 |
1993年 | 80篇 |
1992年 | 66篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 50篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1981年 | 6篇 |
1980年 | 15篇 |
1979年 | 2篇 |
1974年 | 1篇 |
1965年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
Thirty six tests on model tubular steel piles embedded in sand were carried out in the laboratory to assess the effects of compressive load on uplift capacity of piles considering various parameters. The model piles were of 25 mm outside diameter and 2 mm wall thickness. The soil–pile friction angles were 21 and 29° in loose and dense conditions of sand. The piles were embedded in sand for embedment length/diameter ratios of 8,16, and 24 inside a model tank. They were subjected to a static compressive load of 0, 25, 50, 75, and 100% of their ultimate capacity in compression and subjected to pull out loading tests. The experimental results indicated that the presence of the compressive load on the pile decreases the net uplift capacity of a pile and the decrease depends on the magnitude of the compressive load. A logical approach, based on the experimental results, has been suggested to predict the net uplift capacity of a pile considering the presence of compressive load. 相似文献
23.
介绍了长江江新洲堤段应用软体排护岸新型技术的情况,结合长江江新洲护岸工程对软体排施工、工艺、设备作简要叙述。 相似文献
24.
80年代黄河中游来沙量减少,主要原因是降雨量减少和降雨强度减小,流域综合治理也起到了减沙作用。据分析,降雨因素减沙约占总减沙量的70%,流域综合治理减沙约占30%。 相似文献
25.
26.
27.
黑河干流中游地区耗水量变化的历史分析 总被引:3,自引:0,他引:3
黑河流域水资源极其匮乏,加之地区上的配置不均衡和中游地区水土资源的过度开发,导致黑河下游出现了严重的生态环境问题,已影响到我国北方广大地区生态环境质量,受到国家的高度重视和全社会的广泛关注。黑河水资源开发利用主要集中在中游地区,该区是全国重要的商品粮、蔬菜和经济作物生产基地之一,耗水量占流域耗水量的85%以上,是黑河的主要耗水区和径流利用区。利用黑河上游控制站莺落峡站和中游控制站正义峡站水文资料,分析了黑河中游耗水量的变化,结果表明:20世纪80年代以前黑河中游耗水量在4.4亿m^3左右,比较稳定;进入20世纪80年代以后,耗水量明显增加,80年代耗水量比70年代以前增加了1.97亿-2.49亿m^3;90年代耗水量又比80年代增加了1.64亿m^3左右;80年代以来流域耗水量呈明显增加的趋势,这是以人类活动影响为主的结果。 相似文献
28.
P. Balle H. Bockhorn B. Geiger N. Jan S. Kureti D. Reichert T. Schrder 《Chemical Engineering and Processing: Process Intensification》2006,45(12):1065-1073
This study deals with the development of a laboratory bench for the practical evaluation of catalysts that are useful for the direct conversion of NOx and soot in the exhaust of diesel engines. The employed model exhaust is generated by using a diffusion burner with additionally dosing some gaseous components to the burner gas to obtain a realistic feed composition. The produced soot is extensively characterized by employing thermogravimetry, transmission electron microscopy, N2 physisorption and temperature programmed techniques. The results of the different characterization methods show that the present soot is suitable for the intended catalytic investigations. The simultaneous conversion of NOx and soot is examined like in practice, i.e. the soot is separated from the tail gas by a diesel particulate filter (DPF) that is coated with the catalyst. The deposited soot is then catalytically converted by NOx and O2 to form N2 and CO2. The conversions of NOx and soot are measured by exclusively applying gas analysers, whereby a special experimental procedure is developed to determine the soot removal. Hence, additional soot related analytics are not required. To show the suitability of the constructed bench a Pt/Fe2O3/β-zeolite sample is taken as test catalyst that is reported to be very active in NOx/soot reaction. The measurements performed with and without catalyst clearly show the effect of the used sample in simultaneous NOx/soot conversion. We therefore consider the constructed laboratory bench to be a useful tool for testing and ranking catalytic materials. 相似文献
29.
A statistical method for surveying water quality and analysing the results in terms of quantiles is described. The value of a water quality variable in a grab-sample is taken as a deterministic function of the temporal and spatial coordinates of the sampling point. Quantiles can then be defined for any specified region in time and space as unique, fixed values, and randomly located grab-samples may be used to estimate them for the purposes of describing or regulating water quality. Robust statistical inferences are possible using the binomial distribution. Properties of the quantiles, confidence limits, comparisons with fixed values or between regions, assessment of trends, simultaneous inferences and estimation of sample sizes are discussed. Two examples of water quality surveys, one of Port Phillip Bay, the other of the Maribyrnong River, Victoria, are used to illustrate the theory, paying particular attention to practical problems which arose. The proposed method is compared with others based on stochastic models, and is claimed to be simpler and more reliable. 相似文献
30.
针对辽河油田高凝油区块注高温热水(85—95℃)引起的腐蚀、结垢,开展了室内和现场缓蚀、阻垢试验;分析了不同温度下注水的腐蚀情况,对比、考察了不同的缓蚀剂、阻垢剂及其复配物,得出了如下认识:在注高温热水条件下直接采用常温下使用的防腐蚀、防垢方法是不可行的,必须有针对性地进行高温条件下防腐蚀、防垢的实验研究工作。 相似文献