全文获取类型
收费全文 | 7577篇 |
免费 | 137篇 |
国内免费 | 12篇 |
学科分类
工业技术 | 7726篇 |
出版年
2023年 | 21篇 |
2022年 | 19篇 |
2021年 | 99篇 |
2020年 | 48篇 |
2019年 | 61篇 |
2018年 | 96篇 |
2017年 | 71篇 |
2016年 | 120篇 |
2015年 | 76篇 |
2014年 | 149篇 |
2013年 | 308篇 |
2012年 | 234篇 |
2011年 | 286篇 |
2010年 | 229篇 |
2009年 | 262篇 |
2008年 | 280篇 |
2007年 | 260篇 |
2006年 | 240篇 |
2005年 | 221篇 |
2004年 | 203篇 |
2003年 | 223篇 |
2002年 | 197篇 |
2001年 | 174篇 |
2000年 | 189篇 |
1999年 | 226篇 |
1998年 | 675篇 |
1997年 | 421篇 |
1996年 | 294篇 |
1995年 | 223篇 |
1994年 | 218篇 |
1993年 | 202篇 |
1992年 | 123篇 |
1991年 | 105篇 |
1990年 | 107篇 |
1989年 | 109篇 |
1988年 | 93篇 |
1987年 | 77篇 |
1986年 | 82篇 |
1985年 | 91篇 |
1984年 | 67篇 |
1983年 | 61篇 |
1982年 | 64篇 |
1981年 | 69篇 |
1980年 | 50篇 |
1979年 | 52篇 |
1978年 | 38篇 |
1977年 | 54篇 |
1976年 | 77篇 |
1975年 | 16篇 |
1973年 | 13篇 |
排序方式: 共有7726条查询结果,搜索用时 185 毫秒
71.
72.
Nakamura K. Kuhara S. Kimura T. Takada M. Suzuki H. Yoshida H. Yamazaki T. 《Solid-State Circuits, IEEE Journal of》1994,29(11):1317-1322
This 512 Kw×8 b×3 way synchronous BiCMOS SRAM uses a 2-stage wave-pipeline scheme, a PLL self-timing generator and a 0.4-μm BiCMOS process to achieve 220 MHz fully-random read/write operations with a GTL I/O interface. Newly developed circuit technologies include: 1) a zig-zag double word-line scheme, 2) a centered bit-line load layout scheme, and 3) a phase-locked-loop (PLL) with a multistage-tapped ring oscillator which generates a clock cycle proportional pulse (CCPP) and a clock edge lookahead pulse (CELP) 相似文献
73.
Hozumi N. Suzuki H. Okamoto T. Watanabe K. Watanabe A. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1994,1(6):1068-1076
Space charge distribution was measured, applying an electric field of >1 MV/cm to 3 mm thick XLPE cable insulation. Improving the conventional pulse electro-acoustic method, a new method was developed to measure space charge when applying HV to cables. Under high field, hetero charges were formed soon after voltage application, followed by an injection from the cathode. Then intermittent injections of charge packets from the anode took place. The space charge distribution kept changing without becoming stabilized. A simulation was done assuming hysteresis of the injection characteristics. The observed intermittent injection near the anode was qualitatively reproduced using computer simulation 相似文献
74.
Yasuo Suzuki Ryoetsu Yoshino Hisashi Saitoh Kazunori Fukushi Yoshikazu Sonehara 《Journal of Alloys and Compounds》1992,180(1-2):383-389
The mean molal activity coefficients of aqueous scandium chloride, nitrate, bromide and perchlorate solutions were determined at 25.0° for dilute to saturated concentrations, together with the activities of water. In the dilute solutions of scandium halides, the activity coefficients were obtained from electromotive force measurements on galvanic cells, and the osmotic coefficients of all four solutions above 0.1 mol kg−1 were determined from the isopiestic measurements. Least-squares equations were fitted to these coefficients, which were then used to calculate the mean molal activity coefficients and water activities. The relationships between these results and the corresponding activity data for other rare earth salts, and to the cation hydration and ionic interactions, are discussed. The results on scandium perchlorate solutions suggested that the inner-sphere hydration number of tervalent scandium ion may be seven. 相似文献
75.
76.
A novel tungsten light-shield structure has been developed. Tungsten film properties, the device configuration with the tungsten light-shield structure, and experimentally achieved results regarding device characteristics are described. Optical measurement clarified that tungsten film has a sufficiently low transmittance value for practical use for more than 200-nm-thick film and is stable up to 1000°C. The good step coverage and low reflectance, such as 20-40% for aluminum, required for light-shield film were also obtained. A tungsten light-shield structure was applied to a 1/2-in format 668(H)-pixel×575(V)-pixel charge coupled-device (CCD) image sensor. An extremely low smear value, less than 0.001%, was obtained for a 300-nm film thickness 相似文献
77.
Lipid-Lowering Effect of Eriocitrin, the Main Flavonoid in Lemon Fruit, in Rats on a High-Fat and High-Cholesterol Diet 总被引:2,自引:0,他引:2
Yoshiaki Miyake Eriko Suzuki Satoko Ohya Syuichi Fukumoto Masanori Hiramitsu Kazuhiro Sakaida Toshihiko Osawa Yukio Furuichi 《Journal of food science》2006,71(9):S633-S637
ABSTRACT: Eriocitrin (eriodictyol 7- O -β-rutinoside) is the main flavonoid in lemon fruit. In this study, eriocitrin was investigated for its lowering effect on serum and hepatic lipids in high-fat and high-cholesterol fed rats. Rats in the control group ( N = 6) were fed a 20% lard and 1% cholesterol diet for 21 d, and rats in the 0.35% eriocitrin group ( N = 6) and 0.70% eriocitrin group ( N = 6) were fed a diet supplemented with eriocitrin 0.35% and 0.70%, respectively. The content of hepatic total cholesterol and triglyceride in the eriocitrin group was no different from that of the control group. The total cholesterol, VLDL+LDL, triglyceride, and phospholipid in the serum of the 0.35% eriocitrin group showed significantly lower concentrations than the control group ( P < 0.05), although there was no difference in the HDL concentrations among the groups. The lowering effect of eriocitrin for serum total cholesterol was thought to be caused by a decrease in VLDL+LDL. The 0.35% eriocitrin group was shown to have a significant increase in excretion of fecal bile acid ( P < 0.05) and a tendency for enhanced hepatic m-RNA levels of LDL receptor in comparison with the control group. 相似文献
78.
In recent years the requirement for the reduction of energy consumption has been increasing to solve the problems of global warming and the shortage of petroleum resources. For example, in the power generation field, as thermal power generation occupied 60% of the power generation demand, considerable improvement of the thermal efficiency is required. This paper describes the pressure drop characteristics of finned tube banks used for heat exchangers in thermal power generation that were clarified by testing serrated finned tube banks with different fin heights for improved heat transfer and conventional spiral finned tube banks with different fin heights, and an equation to predict pressure drop which is necessary for the heat exchanger design is proposed. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 179–193, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20112 相似文献
79.
The esters of dichloropropanols from the byproduct of hydrolysates during food processing were degraded by the cell-free extracts of a dichloropropanol-assimilating bacterium of Pseudomonas sp. OS-K-29. 1-Acyloxy-2,3-dichloropropane was hydrolysed into the corresponding carbonic acid and 2,3-dichloropropanol, and then the dichloropropanol was dechlorinated. The esterase activity of the cell-free extracts was effective for the esters of the dichloropropanols and monoacylglycerides, but not for hydrolysing the lipase substrates such as triacylglycerides and Tween 60. A comparative study using a series of octanoyl glycerides and the esters of the dichlopropanols showed that the substrate specificities of the cell-free extracts were similar to the monoacylglyceride lipase from Penicillium camembertii. 相似文献
80.