全文获取类型
收费全文 | 166543篇 |
免费 | 1452篇 |
国内免费 | 544篇 |
专业分类
电工技术 | 2867篇 |
综合类 | 2402篇 |
化学工业 | 21666篇 |
金属工艺 | 11271篇 |
机械仪表 | 9309篇 |
建筑科学 | 3747篇 |
矿业工程 | 1347篇 |
能源动力 | 2228篇 |
轻工业 | 5727篇 |
水利工程 | 2215篇 |
石油天然气 | 1993篇 |
武器工业 | 1篇 |
无线电 | 17305篇 |
一般工业技术 | 36662篇 |
冶金工业 | 14119篇 |
原子能技术 | 1713篇 |
自动化技术 | 33967篇 |
出版年
2021年 | 208篇 |
2019年 | 193篇 |
2018年 | 20790篇 |
2017年 | 20486篇 |
2016年 | 13253篇 |
2015年 | 1266篇 |
2014年 | 653篇 |
2013年 | 1143篇 |
2012年 | 5664篇 |
2011年 | 16799篇 |
2010年 | 15232篇 |
2009年 | 12109篇 |
2008年 | 12738篇 |
2007年 | 15534篇 |
2006年 | 869篇 |
2005年 | 5503篇 |
2004年 | 3537篇 |
2003年 | 3264篇 |
2002年 | 1814篇 |
2001年 | 840篇 |
2000年 | 926篇 |
1999年 | 721篇 |
1998年 | 2270篇 |
1997年 | 1474篇 |
1996年 | 1120篇 |
1995年 | 759篇 |
1994年 | 684篇 |
1993年 | 694篇 |
1992年 | 403篇 |
1991年 | 409篇 |
1990年 | 355篇 |
1989年 | 356篇 |
1988年 | 316篇 |
1987年 | 281篇 |
1986年 | 253篇 |
1985年 | 296篇 |
1984年 | 234篇 |
1983年 | 220篇 |
1982年 | 200篇 |
1981年 | 227篇 |
1980年 | 212篇 |
1979年 | 178篇 |
1978年 | 161篇 |
1977年 | 281篇 |
1976年 | 400篇 |
1968年 | 198篇 |
1967年 | 184篇 |
1966年 | 202篇 |
1955年 | 161篇 |
1954年 | 174篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
Karina Polak Beata Bergler-Czop Micha Szczepanek Kamila Wojciechowska Aleksandra Frtczak Norbert Kiss 《International journal of molecular sciences》2021,22(9)
Psoriasis is a chronic, immune-mediated inflammatory disease that affects around 125 million people worldwide. Several studies concerning the gut microbiota composition and its role in disease pathogenesis recently demonstrated significant alterations among psoriatic patients. Certain parameters such as Firmicutes/Bacteroidetes ratio or Psoriasis Microbiome Index were developed in order to distinguish between psoriatic and healthy individuals. The “leaky gut syndrome” and bacterial translocation is considered by some authors as a triggering factor for the onset of the disease, as it promotes chronic systemic inflammation. The alterations were also found to resemble those in inflammatory bowel diseases, obesity and certain cardiovascular diseases. Microbiota dysbiosis, depletion in SCFAs production, increased amount of produced TMAO, dysregulation of the pathways affecting the balance between lymphocytes populations seem to be the most significant findings concerning gut physiology in psoriatic patients. The gut microbiota may serve as a potential response-to-treatment biomarker in certain cases of biological treatment. Oral probiotics administration as well as fecal microbial transplantation were most reported in bringing health benefits to psoriatic patients. However, the issue of psoriatic bacterial gut composition, its role and healing potential needs further investigation. Here we reviewed the literature on the current state of the relationship between psoriasis and gut microbiome. 相似文献
3.
4.
5.
V. E. Gromov A. M. Glezer K. V. Morozov Yu. F. Ivanov K. V. Volkov 《Russian Metallurgy (Metally)》2015,2015(13):1094-1097
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis. 相似文献
6.
7.
8.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
9.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
10.