全文获取类型
收费全文 | 15744篇 |
免费 | 1493篇 |
国内免费 | 480篇 |
专业分类
电工技术 | 429篇 |
综合类 | 1192篇 |
化学工业 | 6622篇 |
金属工艺 | 562篇 |
机械仪表 | 497篇 |
建筑科学 | 1572篇 |
矿业工程 | 736篇 |
能源动力 | 597篇 |
轻工业 | 928篇 |
水利工程 | 456篇 |
石油天然气 | 1031篇 |
武器工业 | 34篇 |
无线电 | 390篇 |
一般工业技术 | 806篇 |
冶金工业 | 1102篇 |
原子能技术 | 244篇 |
自动化技术 | 519篇 |
出版年
2024年 | 83篇 |
2023年 | 214篇 |
2022年 | 415篇 |
2021年 | 485篇 |
2020年 | 572篇 |
2019年 | 451篇 |
2018年 | 399篇 |
2017年 | 498篇 |
2016年 | 509篇 |
2015年 | 588篇 |
2014年 | 958篇 |
2013年 | 1008篇 |
2012年 | 1248篇 |
2011年 | 1159篇 |
2010年 | 942篇 |
2009年 | 966篇 |
2008年 | 722篇 |
2007年 | 963篇 |
2006年 | 862篇 |
2005年 | 730篇 |
2004年 | 604篇 |
2003年 | 590篇 |
2002年 | 457篇 |
2001年 | 415篇 |
2000年 | 335篇 |
1999年 | 302篇 |
1998年 | 230篇 |
1997年 | 214篇 |
1996年 | 162篇 |
1995年 | 121篇 |
1994年 | 118篇 |
1993年 | 58篇 |
1992年 | 56篇 |
1991年 | 48篇 |
1990年 | 46篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 36篇 |
1986年 | 21篇 |
1985年 | 30篇 |
1984年 | 31篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
1959年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
本文通过对立式旋风水膜除尘器除尘性能的模型试验,揭示了几个主要参数对其除尘性能的影响,确定了合理的取值范围,对该种除尘器的设计和应用提供了依据。 相似文献
42.
43.
M.M Ohadi S.S Li R Radermacher S Dessiatoun 《International Journal of Refrigeration》1996,19(4):272-284
Although ammonia has been used for decades as a refrigerant of choice for selected large- and small-scale applications, no formal database is available on heat transfer of ammonia. A critical review of the published literature on heat transfer of ammonia is provided in this paper. The available correlations for in-tube and external boiling/evaporation and condensation heat transfer of ammonia are discussed and evaluated where possible. Supported by the findings of this effort, research areas of relevance that can contribute to expanded use of ammonia as an environmentally friendly refrigerant are suggested. 相似文献
44.
介绍了热钾碱法脱碳钒化工艺技术改进的试验过程,开发了原始开车钒化,在一定条件下取消钒含量控制,实现了运行中不加钒、中修后开车不钒化的新工艺技术。本技术已通过化工部鉴定,处于国内领先水平,并具有可观的经济效益。 相似文献
45.
Sabha Kesraoui-Ouki Christopher R. Cheeseman Roger Perry 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(2):121-126
This paper assesses the potential of natural zeolite utilization as a low-cost ion-exchange and sorbent material in pollution control and recovery of metals. The improvement of the purity of natural zeolites coupled with their chemical modification capabilities in order to provide specific properties may provide a cost-effective alternative for the treatment of heavy metal contaminated soil and water. The application of natural zeolites in industrial pollution control is becoming important and the level of technical effort is increasingly expanding. The extent of application is unlikely to be related solely to their low cost, but also to improved properties and performance characteristics, which will advance the practical implementation of natural zeolites' technology. 相似文献
46.
47.
The simultaneous grinding/agglormeration process has been used to beneficiate Minto coal. Experiments with the Szego Mill, a planetary ring-roller mill with grooved rollers, have given good results. Different roller ridge/groove sizes have been tested and favourable oil-coal-water ratios established. Ash removal is closely related to grinding performance. Very short mill residence times, of the order of 10 seconds, are sufficient for microagglomerate formation. Considerable equipment and operating cost savings are possible with the modified process. 相似文献
48.
Abstract. A method is presented for obtaining the set of all possible pure origins of a given noisy ARMA(2,2) signal. By a transformation to a new set of variables the locus of this set becomes a straight line. 相似文献
49.
This is the last part of a four-part survey of optimization models and solution algorithms for winter road maintenance planning. The two first parts of the survey address system design problems for winter road maintenance. The third part concentrates mainly on vehicle routing problems for spreading operations. The aim of this paper is to provide a comprehensive survey of optimization models and solution methodologies for the routing of vehicles for plowing and snow disposal operations. We also review models for the fleet sizing and fleet replacement problems. 相似文献
50.
Rates of ammonia (NH3) loss from a ryegrass sward measured using a system of small wind tunnels were compared with concurrent measurements made using a micrometeorological mass balance method. Measurements were made during two experiments within a circular plot (radius 10m) treated with urea at a rate of 200kgNha?1. In the first experiment, air speed through the tunnels was adjusted as necessary to maintain a value of approximately 1ms?1. This value differed on most occasions from the mean ambient wind speed which was measured at a height of 250mm and which ranged from 0.61 to 2.95ms?1. Rates of loss measured using the wind tunnels differed by a factor of between two and five from those measured using the mass balance method; there was no consistent pattern in the differences between the rates of loss. The total losses of NH3 measured during 15 days were equivalent to 49.1 and 30.2kg Nha?1 for the mass balance and wind tunnel methods, respectively. In the second experiment, air speed through the tunnels was adjusted as necessary to maintain a value as close as possible to the mean ambient wind speed measured at a height of 250mm. Rates of NH3 loss measured using the two methods did not differ significantly; total losses of NH3 during 17 days were equivalent to 96.9 and 101kg Nha?1 for the mass balance and wind tunnel methods, respectively. The difference between the findings of the two experiments could be attributed to the direct effect of air speed through the tunnels rather than to differences between ambient temperatures and those inside the tunnels. During and following periods of rain the rates of loss measured using the tunnels were up to six times greater than those observed with the mass balance method. Rates of loss measured by the two methods became similar again when the tunnels were moved following rain. The study demonstrates that enclosures can be designed and operated to provide reliable measurements of the rate of NH3 loss from grassland. Potential applications of the two methods are discussed. 相似文献