全文获取类型
收费全文 | 91333篇 |
免费 | 8683篇 |
国内免费 | 5216篇 |
专业分类
电工技术 | 6611篇 |
技术理论 | 2篇 |
综合类 | 6770篇 |
化学工业 | 15732篇 |
金属工艺 | 4074篇 |
机械仪表 | 5485篇 |
建筑科学 | 3504篇 |
矿业工程 | 2545篇 |
能源动力 | 3906篇 |
轻工业 | 12225篇 |
水利工程 | 1564篇 |
石油天然气 | 23586篇 |
武器工业 | 665篇 |
无线电 | 5440篇 |
一般工业技术 | 5857篇 |
冶金工业 | 2285篇 |
原子能技术 | 788篇 |
自动化技术 | 4193篇 |
出版年
2024年 | 476篇 |
2023年 | 1302篇 |
2022年 | 2375篇 |
2021年 | 2841篇 |
2020年 | 3042篇 |
2019年 | 2888篇 |
2018年 | 2495篇 |
2017年 | 3314篇 |
2016年 | 3513篇 |
2015年 | 3459篇 |
2014年 | 5147篇 |
2013年 | 5515篇 |
2012年 | 6349篇 |
2011年 | 6675篇 |
2010年 | 4844篇 |
2009年 | 4715篇 |
2008年 | 4218篇 |
2007年 | 5392篇 |
2006年 | 5461篇 |
2005年 | 4689篇 |
2004年 | 4106篇 |
2003年 | 3777篇 |
2002年 | 3190篇 |
2001年 | 2656篇 |
2000年 | 2419篇 |
1999年 | 2023篇 |
1998年 | 1599篇 |
1997年 | 1408篇 |
1996年 | 1166篇 |
1995年 | 919篇 |
1994年 | 771篇 |
1993年 | 517篇 |
1992年 | 437篇 |
1991年 | 351篇 |
1990年 | 283篇 |
1989年 | 246篇 |
1988年 | 142篇 |
1987年 | 89篇 |
1986年 | 52篇 |
1985年 | 83篇 |
1984年 | 83篇 |
1983年 | 51篇 |
1982年 | 41篇 |
1981年 | 19篇 |
1980年 | 25篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1976年 | 5篇 |
1959年 | 9篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
本文针对美孚油回收液与兰炼8#油混合利用进行可行性实验研究,经过重度、粘度、可燃性等方面的实验研究,表明美孚油回收液与兰炼8#油混合可以用在电动轮上并且获得良好的效果。 相似文献
12.
Bhupesh C. Roy Motonobu Goto & Tsutomu Hirose 《International Journal of Food Science & Technology》1996,31(2):137-141
Tomato seed oil was extracted with supercritical carbon dioxide in a semibatch-flow extractor within the temperature range 313–343 K and the pressure range 10.8–24.5MPa. The extraction rates increased with pressure, but decreased with temperature increase because of the variation in solvent density and resultant differences in oil solubility. The fatty acid composition of the extracted oil was similar to that of soybean oil. 相似文献
13.
对传统双曲线极尖的四极透镜进行了磁性能分析。在此基础上,提出了极尖断面为折线的四极透镜结构。磁场的数值分析以及测量结果表明:该结构产生的场梯度均匀,且具有磁场集中、磁场梯度高、便于加工和安装的对称性控制等优点。该结构的四极透镜已用于CYCIAE-30回旋加速器和HI-13串列加速器束流输运线之中 相似文献
14.
Emmanuel O. Egbogah Richard A. Dawe 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(3):132-144
Recent studies have suggested the possibility of spontaneous emulsification as a mechanism for enhanced oil recovery (EOR). The discussions have, however, remained essentially qualitative. A study was therefore undertaken to estimate quantitatively the contribution of spontaneous emulsification as an EOR mechanism. The tests were conducted on several bulk liquid/liquid systems as well as by displacement experiments in unconsolidated synthetic sand packs. Spontaneous emulsification was found to be a mechanism for EOR: the estimated extra contribution to EOR due to this mechanism was found to be significant in laboratory scale displacement experiments. Tertiary recovery was always greater when spontaneous emulsification was evident than otherwise. Results of tests on bulk liquid/liquid systems indicate that the occurrence or absence of spontaneous emulsification can be correlated with the values of ‘partition parameter’. It may be concluded that higher oil recoveries may be achieved in chemical EOR processes where interface mass transfer (and the accompanying spontaneous emulsification) occurs. The evaluation of efficiency of residual oil mobilisation through the capillary number theory (with and without spontaneous emulsification) is also discussed. Displacement tests with spontaneously emulsifying systems showed that residual oil left behind a conventional waterflood was mobilised in a range of capillary numbers much less than that which applies to low-tension waterfloods. 相似文献
15.
储层石蜡沉积预测技术研究与应用 总被引:1,自引:0,他引:1
在油田开发过程中 ,由于油藏温度、压力等条件的变化 ,高含蜡原油在近井带容易产生石蜡沉积 ,堵塞地层孔隙或裂缝 ,严重影响油田开采 ,尤其对于低渗油田 ,伤害特别严重。文中应用理想溶液理论、质量守恒和能量守恒等基本原理 ,建立更符合油田实际情况的油藏中石蜡沉积预测数学模型 ,开发一套方便实用的油藏中石蜡沉积预测软件系统FPOS1 0。在此基础上 ,应用室内实验数据和现场数据对吉林新民油田油井石蜡沉积情况进行预测和现场拟合 ,确定新民油田临界石蜡沉积半径为 2 5m ,快速、准确地为现场清防蜡措施提供理论依据。 相似文献
16.
用于重离子核反应实验测量的纵向电场气体电离室 总被引:1,自引:0,他引:1
本文报道了一种新型的大动态范围,多叠层探测器系统组件之一的纵向电场气体电离室的构造,性能和在中能得离子核反应实验中的应用。 相似文献
17.
Monitoring of nitrate (NO3-) and nitrite (NO2-) content in agricultural products in Slovenia has been carried out since 1996. The results of monitoring over the period 1996-2002 are presented. During this time 924 samples of 14 different agricultural products (potato, lettuce, apples, carrot, silage maize, cabbage, grapes, peaches, string beans, cereals, pears, cucumbers, strawberries and tomato) were analysed. The samples were taken at the time of maturity directly from growing sites and they were analysed using segmented flow analysis. The average nitrate contents were the highest in lettuce (1074 mg kg-1), cabbage (881 mg kg-1), string beans (298 mg kg-1) and carrot (264 mg kg-1), and they were moderately high in potato (158 mg kg-1), silage maize (122 mg kg-1), strawberries (94 mg kg-1), cucumbers (93 mg kg-1) and cereals (49 mg kg-1). Low nitrate contents (below 6 mg kg-1) were found in fruit (grapes, peaches, apples and pears) and tomato. With the exception of cereals (8.9 mg kg-1), apples (1.5 mg kg-1), potato (1.2 mg kg-1) and pears (1.0 mg kg-1) the content of nitrites did not exceed 0.5 mg kg-1. It may be concluded that the results of the monitoring were in most cases similar to the results of investigations obtained in other countries. 相似文献
18.
19.
空气压缩机无油润滑在山脚树矿的应用 总被引:1,自引:1,他引:0
山脚树矿有5台1966年上海生产的4L—20/8空气压缩机,运行很不经济,利用聚四氟乙烯合成材料制成活塞环,全部实现无油润滑运转,取得了良好的经济效益。 相似文献
20.
This paper highlights the role of the faculty member in recruiting students currently enrolled in B.S. programs in engineering and the sciences into full-time pursuit of a graduate-level engineering degree. The faculty member is demonstrated to be in a unique position to influence such students, providing strong counterforces to a confluence of attitudes and pressures experienced during the B.S. experience which effectively create a barrier to full-time engineering graduate study. We analyze this barrier via the method of force field analysis, and demonstrate that effective recruitment into full-time graduate study must be based on a four-fold strategy of education, expectations, improved B.S. experience and better control of the B.S. environment. Approaches to implement these strategies are discussed. 相似文献