全文获取类型
收费全文 | 8071篇 |
免费 | 453篇 |
国内免费 | 88篇 |
专业分类
电工技术 | 167篇 |
综合类 | 543篇 |
化学工业 | 2294篇 |
金属工艺 | 357篇 |
机械仪表 | 560篇 |
建筑科学 | 96篇 |
矿业工程 | 125篇 |
能源动力 | 591篇 |
轻工业 | 695篇 |
水利工程 | 27篇 |
石油天然气 | 2534篇 |
武器工业 | 18篇 |
无线电 | 54篇 |
一般工业技术 | 244篇 |
冶金工业 | 98篇 |
原子能技术 | 25篇 |
自动化技术 | 184篇 |
出版年
2024年 | 8篇 |
2023年 | 82篇 |
2022年 | 150篇 |
2021年 | 190篇 |
2020年 | 213篇 |
2019年 | 190篇 |
2018年 | 147篇 |
2017年 | 191篇 |
2016年 | 236篇 |
2015年 | 278篇 |
2014年 | 398篇 |
2013年 | 408篇 |
2012年 | 355篇 |
2011年 | 550篇 |
2010年 | 391篇 |
2009年 | 348篇 |
2008年 | 272篇 |
2007年 | 329篇 |
2006年 | 338篇 |
2005年 | 330篇 |
2004年 | 287篇 |
2003年 | 333篇 |
2002年 | 263篇 |
2001年 | 291篇 |
2000年 | 388篇 |
1999年 | 336篇 |
1998年 | 248篇 |
1997年 | 240篇 |
1996年 | 204篇 |
1995年 | 178篇 |
1994年 | 122篇 |
1993年 | 88篇 |
1992年 | 75篇 |
1991年 | 46篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有8612条查询结果,搜索用时 15 毫秒
51.
52.
高分子量聚合物的分子量对岩心渗透率的适应性研究 总被引:12,自引:2,他引:10
本文通过不同分子量的高分子量聚合物(部分水解聚丙烯酰胺)在不同渗透率岩心中的流动实验,研究了高分子量聚合物的分子量与岩心渗透率之间的匹配关系,为大庆油田采用高分子量聚合物驱油提供决策依据。 相似文献
53.
Bo Jiang Jeffrey L. Brown Jane Sheraton Nathalie Fortin Howard Bussey 《Yeast (Chichester, England)》1994,10(3):341-353
We have identified three yeast genes, KES1, HES1 and OSH1, whose products show homology to the human oxysterol binding protein (OSBP). Mutations in these genes resulted in pleiotropic sterol-related phenotypes. These include tryptophan-transport defects and nystatin resistance, shown by double and triple mutants. In addition, mutant combinations showed small but apparently cumulative reductions in membrane ergosterol levels. The three yeast genes are also functionally related as overexpression of HES1 or KES1 alleviated the tryptophan-transport defect in kes1Δ or osh1Δ mutants, respectively. Our study implicates this new yeast gene family in ergosterol synthesis and provides comparative evidence of a role for human OSBP in cholesterol synthesis. 相似文献
54.
防治畜类寄生线虫的又一阿维菌素类化合物--道拉菌素 总被引:4,自引:2,他引:2
道拉菌素是利用生物突变合成方法得到的新型阿维菌素族广谱杭寄生虫药。它的化学结构和作用机制与依维菌素相似。试验证实道拉菌素在低剂量下对多种体内外寄生虫具有良好的防治效果。 相似文献
55.
靳军 《石油化工安全环保技术》2003,19(3):17-18
简述了大庆油田助剂厂3500kt/a常减压减压塔的管道布置设计特点,体现出塔类设备的管道设计原则,并结合管道设计的经济性、安全性展开论述。 相似文献
56.
57.
中国油田堵水技术综述 总被引:17,自引:0,他引:17
本文论述了我国油田堵水技术的发展及其在油田开发中的作用,总结和阐述了油井化学堵水技术和注水井吸水剖面调整技术的原理和效益,指明了实践证实的有成效的工艺方法和堵水技术发展方向。 相似文献
58.
The effect of solute impregnation on water loss and oil uptake during potato strip frying was studied. Blanched potato strips were impregnated at 25°C by soaking in a solution of sucrose-NaCl-water, 20-5-75% by weight. After rinsing and air drying, strips were deep fried in sunflower oil at 160, 170 and 180°C. A control treatment, consisting of potato strips blanched but not soaked and later air dried was also conducted. Solute impregnation provided a decrease of the oil uptake. Two models, based on Fick's law were used to describe water loss during frying. The first one is the classic model with an effective moisture diffusion coefficient assumed a constant value. The second model considers that diffusion coefficient varies during the frying process. For a given frying temperature, constant diffusion coefficient for control potatoes resulted in lower values than the impregnated ones. The variable diffusivity model showed a two-stage behavior: during the first stage of frying, diffusion coefficient increased with frying temperatures, but from a given time on an inverse behavior began. This last fact was found to be related to an increase of the measured peak force needed to penetrate the potato crust. 相似文献
59.
Three sorbents were compared in order to determine their potential for oil spill cleanup. Polypropylene nonwoven web, rice hull, and bagasse with two different particle sizes were evaluated in terms of oil sorption capacities and oil recovery efficiencies. Polypropylene can sorb almost 7 to 9 times its weight from different oils. Bagasse, 18 to 45 mesh size, follows polypropylene as the second sorbent in oil spill cleanup. Bagasse, 14 to 18 mesh size, and rice hull have comparable oil sorption capacities, which are lower than those of the two former sorbents. It was found that oil viscosity plays an important role in oil sorption by sorbents. All adsorbents used in this work could remove the oil from the surface of the water preferentially. 相似文献
60.
Biochemical conversion of crude oils is a multi-step process proceeding through a series of biochemical reactions. These reactions can be characterized by a set of chemical markers which are associated with the chemical composition of crude oils. Reactions with heavy crude oils indicate that there is an overall decrease in the concentration and chemical speciation of organic sulfur compounds, and a redistribution of hydrocarbons and organometallic species. The contents of trace metals in the crude oils, such as nickel and vanadium, also decrease. Further, heavy ends of crudes, containing the asphaltenes and the polar nitrogen, sulfur, and oxygen containing fractions, as well as the organometallic compounds and complexes, are biochemically converted to lower molecular weight chemical species. In the studies reported in this paper, microorganisms used to mediate such reactions were thermophilic ( > 60°C) and pressure tolerant (up to 2500 psi). These organisms are also capable of biochemical conversion of bituminous and lignite coals in an analogous manner to their action on crude oils and follow similar trends characterized by chemical markers. For example, X-ray absorption near-edge structural (XANES) analyses of biotreated crude oils and low grade coals show that biochemical reactions lead to decreases in organic sulfides and thiophenes with a concurrent increase in sulfoxide contents. Chemically related constituents present in heavy crude oil fractions and low grade coals are the asphaltenes. Asphaltenes are complex structures containing heteroatoms and metals involved in inter- and intra-molecular bridges and stereochemical configurations. The chemical markers associated with the biochemical conversion of oils and coals indicate multiple biochemical processes involving chemical reactions at sites containing heteroatoms and metals leading to a breakdown of the structure(s) to smaller molecular weight units. Thus, using chemical markers as diagnostic tools, the extent and the efficiency of fossil fuel bioconversion may be predicted and monitored, allowing for better cost-efficient field trials. Recent results in this area will be presented and discussed in this paper. 相似文献