全文获取类型
收费全文 | 79143篇 |
免费 | 8561篇 |
国内免费 | 4475篇 |
专业分类
电工技术 | 6640篇 |
技术理论 | 8篇 |
综合类 | 6451篇 |
化学工业 | 11336篇 |
金属工艺 | 4786篇 |
机械仪表 | 4973篇 |
建筑科学 | 6213篇 |
矿业工程 | 2864篇 |
能源动力 | 2403篇 |
轻工业 | 5488篇 |
水利工程 | 1944篇 |
石油天然气 | 3734篇 |
武器工业 | 1038篇 |
无线电 | 9023篇 |
一般工业技术 | 8380篇 |
冶金工业 | 4419篇 |
原子能技术 | 1196篇 |
自动化技术 | 11283篇 |
出版年
2024年 | 448篇 |
2023年 | 1531篇 |
2022年 | 3220篇 |
2021年 | 4169篇 |
2020年 | 3188篇 |
2019年 | 2370篇 |
2018年 | 2706篇 |
2017年 | 2923篇 |
2016年 | 2666篇 |
2015年 | 3807篇 |
2014年 | 4588篇 |
2013年 | 5429篇 |
2012年 | 6141篇 |
2011年 | 6432篇 |
2010年 | 5644篇 |
2009年 | 5219篇 |
2008年 | 5094篇 |
2007年 | 4722篇 |
2006年 | 4256篇 |
2005年 | 3548篇 |
2004年 | 2447篇 |
2003年 | 1722篇 |
2002年 | 1564篇 |
2001年 | 1264篇 |
2000年 | 1204篇 |
1999年 | 1014篇 |
1998年 | 1035篇 |
1997年 | 787篇 |
1996年 | 720篇 |
1995年 | 477篇 |
1994年 | 402篇 |
1993年 | 314篇 |
1992年 | 227篇 |
1991年 | 135篇 |
1990年 | 119篇 |
1989年 | 97篇 |
1988年 | 91篇 |
1987年 | 53篇 |
1986年 | 48篇 |
1985年 | 39篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 24篇 |
1981年 | 17篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1977年 | 58篇 |
1976年 | 106篇 |
1959年 | 14篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
AN Grigorenko 《Canadian Metallurgical Quarterly》1992,46(11):7292-7294
12.
Yang Lüyun 《中国稀土学报(英文版)》2006,24(Z2)
The fabrication of one kind of large core area Nd3 doped silicate glass photonic crystal fiber, and demonstration of the fiber's waveguidence properties were reported. This fiber owns a random air hole distribution in the cladding. The measured minimum loss of this kind of fiber is 10 dB·m-1 at 660 nm. These fibers can sustain only a single mode at least over wavelength ranging from 660 nm to 980 nm. 相似文献
13.
In order to meet increasingly stringent discharge standards, new applications and control strategies for the sustainable removal of nitrogen from wastewater have to be implemented. In the past years, numerous studies have been carried out dealing with the application of fuzzy logic to improve the control of the activated sludge process. In this paper, fuzzy control strategies of predenitrification systems are presented that could lead to better effluent quality and, in parallel, to a reduction of chemicals consumption. Extensive experimental investigations on lab scale plant studies have shown that there was excellent correlation between nitrate concentration and ORP value at the end of the anoxic zone. Results indicated that ORP could be used as an on-line fuzzy control parameter of nitrate recirculation and external carbon addition. The optimal value of ORP to control nitrate recirculation and external carbon addition was - 86 +/- 2 mV and - 90 +/- 2 mV, respectively. The results obtained with real wastewater also showed the good performance and stability of the fuzzy controllers independently from external disturbances. The integrated control structure of nitrate recirculation and external carbon addition in the predenitrification system is also presented. 相似文献
14.
PURPOSE: To evaluate the accuracy of measuring intraocular pressure by handheld non-contact applanation tonometer. METHOD: 58 patients' (113 eyes) intraocular pressure were measured by Keeler, non-contact tonometer and R 900 Goldmann applanation tonometer and the results of measurement of intraocular pressure by the two kinds of tonometers were compared. RESULT: The mean intraocular pressure measured by non-contact is 16.31 +/- 5.59 mmHg and 17.49 +/- 6.13 mmHg (1 mmHg = 0.1333 kPa) by Goldmann applanation tonometer, respectively. There was no statistical significance to be found (P > 0.05) between the two methods. By linear correlation and regression analysis, a positive correlation was found between the two methods (r = 0.8942, b = 0.8154). CONCLUSION: The handheld non-contact tonometer has the same accuracy and reliability of measurement of intraocular pressure comparing with Goldmann applanation tonometer, and it can be used in glaucoma clinic and screening. 相似文献
15.
16.
17.
ElectronmicroscopicobservationsandDNAchainfragmentationstudiesonapoptosisinbonetumorcelsinducedby153SmEDTMPZhuShouPeng,Xia... 相似文献
18.
Mei Xuan Xu Wen Guang Liu Yun Lin Guan Zuo Peng Bi Kang De Yao 《Polymer International》1995,38(2):205-209
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties. 相似文献
19.
The iron rhenate was compounded by chemical method, which may be generated during wear process of Fe-Re alloys at elevated
temperature. The friction coefficient of iron rhenate has been determined by a pin-on-disc device. The results show that iron
rhenate plays role of lubricating at RT-600 °C. The lubricating behavior is related to the matching pairs. The hardness of
the materials of matching pairs, compatibility of iron rhenate with materials of matching pairs and surface roughness of disc
affect the lubricating behavior of iron rhenate mostly. The principle of matching pairs is proposed.
Project supported by the National Natural Science Foundation of China
Synopsis of the first author Xiong Dangsheng. associated professor, born in 1960. Current research fields include high-temperature self-lubricating alloys
and tribological properties of material. 相似文献
20.