全文获取类型
收费全文 | 465969篇 |
免费 | 12591篇 |
国内免费 | 5603篇 |
专业分类
电工技术 | 13162篇 |
技术理论 | 4篇 |
综合类 | 5523篇 |
化学工业 | 68611篇 |
金属工艺 | 20097篇 |
机械仪表 | 17846篇 |
建筑科学 | 13664篇 |
矿业工程 | 4462篇 |
能源动力 | 13281篇 |
轻工业 | 33064篇 |
水利工程 | 5862篇 |
石油天然气 | 11045篇 |
武器工业 | 1007篇 |
无线电 | 56933篇 |
一般工业技术 | 88904篇 |
冶金工业 | 77601篇 |
原子能技术 | 10043篇 |
自动化技术 | 43054篇 |
出版年
2022年 | 4948篇 |
2021年 | 7162篇 |
2020年 | 5322篇 |
2019年 | 5614篇 |
2018年 | 8494篇 |
2017年 | 8758篇 |
2016年 | 8944篇 |
2015年 | 7361篇 |
2014年 | 10797篇 |
2013年 | 24312篇 |
2012年 | 16569篇 |
2011年 | 20605篇 |
2010年 | 16971篇 |
2009年 | 18330篇 |
2008年 | 18536篇 |
2007年 | 17800篇 |
2006年 | 16150篇 |
2005年 | 14263篇 |
2004年 | 12577篇 |
2003年 | 11791篇 |
2002年 | 11112篇 |
2001年 | 10838篇 |
2000年 | 10149篇 |
1999年 | 10343篇 |
1998年 | 24800篇 |
1997年 | 17140篇 |
1996年 | 13195篇 |
1995年 | 9867篇 |
1994年 | 8600篇 |
1993年 | 8571篇 |
1992年 | 6228篇 |
1991年 | 5799篇 |
1990年 | 5770篇 |
1989年 | 5379篇 |
1988年 | 5097篇 |
1987年 | 4456篇 |
1986年 | 4333篇 |
1985年 | 4826篇 |
1984年 | 4432篇 |
1983年 | 4003篇 |
1982年 | 3665篇 |
1981年 | 3743篇 |
1980年 | 3444篇 |
1979年 | 3330篇 |
1978年 | 3336篇 |
1977年 | 3750篇 |
1976年 | 4849篇 |
1975年 | 2850篇 |
1974年 | 2665篇 |
1973年 | 2732篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
Zienko S. I. Zhbanova V. L. 《Journal of Communications Technology and Electronics》2022,67(4):395-402
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a... 相似文献
2.
Atomic Energy - The history and direction of further development of space nuclear energetics are examined. The functional diagram and principle of operation of a promising, powerful,... 相似文献
3.
Xiao Zhu Chen Yanxun Jiang Hongbo Hu Zhenzhen Lui John C. S. Min Geyong Dustdar Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of... 相似文献
4.
5.
Can Ercan S. Esra Safran Artuğ Türkmenoğlu Uğur Karabakal 《Journal of surfactants and detergents》2021,24(1):139-147
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated. 相似文献
6.
7.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a... 相似文献
8.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献
9.
针对煤矸石粉替代率50%、聚酯纤维掺量0.4%的沥青混合料,开展盐冻耦合作用(NaCl溶液质量分数为0%、7.0%、13.0%、26.5%,冻融循环次数为0、2、4、6、8)下的半圆弯曲(SCB)试验,分析了盐冻耦合作用对SCB试件内部损伤劣化过程的影响.结果表明:NaCl溶液质量分数为13.0%、冻融循环为8次时,盐冻耦合作用对沥青混合料的侵蚀破坏作用最强,试件内部损伤最严重;在煤矸石粉与矿粉质量比为1∶1、聚酯纤维掺量为0.4%的条件下,沥青混合料能够形成高黏性、致密、厚实的沥青膜以及由纤维形成的三维网状结构,从而显著降低盐冻侵蚀对沥青混合料的损伤.通过Poly2D模型对SCB试件的极限拉应力损伤量进行拟合,拟合系数为0.944. 相似文献
10.
Telecommunication Systems - Energy saving in User Equipment (UE) is one of the important issues for limited sources of power in the device. It is critical for the UE to maximize its energy... 相似文献