全文获取类型
收费全文 | 1370篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 21篇 |
综合类 | 1篇 |
化学工业 | 216篇 |
金属工艺 | 18篇 |
机械仪表 | 23篇 |
建筑科学 | 68篇 |
能源动力 | 33篇 |
轻工业 | 50篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 181篇 |
一般工业技术 | 177篇 |
冶金工业 | 454篇 |
原子能技术 | 8篇 |
自动化技术 | 158篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 22篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2018年 | 28篇 |
2017年 | 20篇 |
2016年 | 32篇 |
2015年 | 25篇 |
2014年 | 37篇 |
2013年 | 72篇 |
2012年 | 29篇 |
2011年 | 61篇 |
2010年 | 57篇 |
2009年 | 40篇 |
2008年 | 45篇 |
2007年 | 65篇 |
2006年 | 36篇 |
2005年 | 45篇 |
2004年 | 26篇 |
2003年 | 43篇 |
2002年 | 27篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 29篇 |
1998年 | 160篇 |
1997年 | 72篇 |
1996年 | 66篇 |
1995年 | 42篇 |
1994年 | 27篇 |
1993年 | 37篇 |
1992年 | 13篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 2篇 |
1983年 | 8篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有1413条查询结果,搜索用时 15 毫秒
1.
László Lőrincz Máté Zsemberi György Bánsághi Tamás Sohajda Edit Székely 《化学工程与技术》2018,41(7):1466-1472
Chiral molecules, especially enantiomers and diastereomers of purity > 99 %, present a significant market share within the chemical, pharmaceutical, and flavor industries. Antisolvent precipitations, both batch and semicontinuous operations to serve the current trends in flow chemistry were demonstrated to be environmentally benign and efficient tools in achieving high optical purities. Although salts are known to be insoluble in supercritical CO2, instabilities of the nascent salts were detected and applied for increasing efficiency. Diastereomeric excess values of the crystalline products exceeded 99 % in maximum of three consecutive steps both by repeated resolution with half molar equivalent of the amine to the acid and by direct recrystallization of the salts. 相似文献
2.
3.
MF Chen YY Jan CS Wang TL Hwang LB Jeng SC Chen TC Chao 《Canadian Metallurgical Quarterly》1997,84(9):1229-1232
The effect of phenylephrine-induced reflex parasympathetic stimulation on QT interval and its dispersion was studied in 16 healthy subjects with a history of paroxysmal supraventricular tachycardia, both during sinus rhythm and during atrial pacing. Results demonstrate that rapid reflex parasympathetic stimulation does not influence QT interval duration or QT dispersion, and also emphasize the inappropriateness of Bazett's formula, the need for comparison of QT intervals during identical heart rates, and the importance of analyzing all 12 leads of a standard electrocardiogram when assessing the effects of various interventions on the QT interval. 相似文献
4.
5.
Rate (n -1)/n punctured convolutional codes are very effective in conjunction with embedded differential pulse code modulation (EDPCM) in variable-bit-rate speech transmission. The authors investigate the performance of this variable-bit-rate EDPCM system in terms of probability of bit error and audio signal-to-noise ratio (SNR) versus channel SNR in an additive white Gaussian noise and Rayleigh fading channel using soft-decision decoding for specific sets of code generators of punctured convolutional codes. The results show that different sets of code generators affect the performance in terms of both the probability of bit error and the audio SNR. Improvements were obtained in the cases of Gaussian nonfading and Rayleigh fading channels using soft-decision decoding 相似文献
6.
7.
8.
YG Zorbas YY Yaroshenko NK Kuznetsov SL Matvedev 《Canadian Metallurgical Quarterly》1998,64(1-3):259-273
The aim of this study was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on the deficiency of electrolytes, which is characterized by higher rather than lower plasma concentration of electrolytes during prolonged hypokinesia (HK) (decreased number of km taken per day). Forty long distance runners aged 22-25 yr with a peak VO2 65.4 mL min(-1) kg(-1) with an average 14.2 km d running distance were selected as subjects. They were equally divided into four groups: 1) unsupplemented control subjects (UCS); 2) unsupplemented hypokinetic subjects (UHS); 3) supplemented hypokinetic subjects (SHS), and 4) supplemented control subjects (SCS). During the investigation of 364 d, groups 2 and 3 maintained an average running distance of less than 4.7 km per day, groups 1 and 4 did not experience any modification in their normal training routines and diets. During the preexperimental period of 60 d and during the experimental period of 364 d urinary excretion of electrolytes and concentrations of sodium, potassium, calcium, and magnesium in plasma were determined. Whole blood hemoglobin, hematocrit index, plasma osmolality, and plasma protein concentration were measured. In the UHS plasma concentration of electrolytes and urinary excretion thereof, fluid elimination, hematocrit, whole blood hemoglobin, plasma osmolality, and plasma protein concentration increased significantly (p < 0.05) when compared with the UCS, SCS, and SHS groups. In the SHS plasma concentration of electrolytes and urinary excretion thereof, fluid excretion, whole blood hemoglobin, hematocrit, plasma osmolality, and plasma protein concentration decreased when compared with the UHS and increased insignificantly when compared with the UCS and SCS groups. It was concluded that FSS may be used to prevent or minimize electrolyte deficiency in endurance-trained volunteers during prolonged restriction of muscular activity. 相似文献
9.
10.
Optical measurements of thermal diffusivity of a material 总被引:2,自引:0,他引:2
The measurement of thermal diffusivity of a material (in particular, a thin film) is important for various reasons, e.g., to predict the heat transfer in the solid subjected to a thermal process, to monitor surface composition or morphology, or to detect invisible subsurface defects like delaminations. This measurement can be done in a noncontact manner using various photothermal methods. Such methods typically involve pulsed heating of the surface by small amounts using a laser source; the decay of the surface temperature after this pulsed photothermal heating is then probed to provide the thermal diffusivity. Various probing methods have been developed in the literature, including the probing of reflection, refraction, and diffraction from the pulsed heated area, infrared thermal radiometry, and surface deformation. This paper provides an overview of such techniques and some examples of their applications. 相似文献