全文获取类型
收费全文 | 30250篇 |
免费 | 1324篇 |
国内免费 | 97篇 |
专业分类
电工技术 | 372篇 |
综合类 | 46篇 |
化学工业 | 6968篇 |
金属工艺 | 645篇 |
机械仪表 | 608篇 |
建筑科学 | 1991篇 |
矿业工程 | 173篇 |
能源动力 | 929篇 |
轻工业 | 2838篇 |
水利工程 | 255篇 |
石油天然气 | 84篇 |
武器工业 | 7篇 |
无线电 | 2035篇 |
一般工业技术 | 5702篇 |
冶金工业 | 3619篇 |
原子能技术 | 192篇 |
自动化技术 | 5207篇 |
出版年
2023年 | 193篇 |
2022年 | 412篇 |
2021年 | 690篇 |
2020年 | 468篇 |
2019年 | 458篇 |
2018年 | 668篇 |
2017年 | 618篇 |
2016年 | 780篇 |
2015年 | 640篇 |
2014年 | 954篇 |
2013年 | 2112篇 |
2012年 | 1527篇 |
2011年 | 2056篇 |
2010年 | 1457篇 |
2009年 | 1407篇 |
2008年 | 1756篇 |
2007年 | 1517篇 |
2006年 | 1300篇 |
2005年 | 1168篇 |
2004年 | 1047篇 |
2003年 | 925篇 |
2002年 | 854篇 |
2001年 | 515篇 |
2000年 | 482篇 |
1999年 | 528篇 |
1998年 | 531篇 |
1997年 | 481篇 |
1996年 | 445篇 |
1995年 | 385篇 |
1994年 | 410篇 |
1993年 | 382篇 |
1992年 | 315篇 |
1991年 | 269篇 |
1990年 | 246篇 |
1989年 | 292篇 |
1988年 | 232篇 |
1987年 | 202篇 |
1986年 | 207篇 |
1985年 | 279篇 |
1984年 | 252篇 |
1983年 | 210篇 |
1982年 | 195篇 |
1981年 | 235篇 |
1980年 | 156篇 |
1979年 | 171篇 |
1978年 | 167篇 |
1977年 | 141篇 |
1976年 | 148篇 |
1975年 | 135篇 |
1974年 | 127篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Chadwin D. Young Gennadi Bersuker Yuegang Zhao Jeff J. Peterson Joel Barnett George A. Brown Jang H. Sim Rino Choi Byoung Hun Lee Peter Zeitzoff 《Microelectronics Reliability》2005,45(5-6):806
Effects of constant voltage stress (CVS) on gate stacks consisting of an ALD HfO2 dielectric with various interfacial layers were studied with time dependent sensing measurements: DC I–V, pulse I–V, and charge pumping (CP) at different frequencies. The process of injected electron trapping/de-trapping on pre-existing defects in the bulk of the high-κ film was found to constitute the major contribution to the time dependence of the threshold voltage (Vt) shift during stress. The trap generation observed with the low frequency CP measurements is suggested to occur within the interfacial oxide layer or the interfacial layer/high-κ interface, with only a minor effect on Vt. 相似文献
82.
83.
84.
85.
86.
Peter Horn Peter Schaaf Brigitte Holbach Stefan Hölzl Heinz Eschnauer 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1993,196(5):407-409
For provenance assignments of wines strontium isotope ratios can be used because soils from different wine-growing regions, and hence the wines grown there, each show specific ratios. Some successful applications are demonstrated.
87Sr/86Sr aus Gestein und Boden in Rebe und Wein
Zusammenfassung Zur Herkunftsbestimmung von Weinen können Strontium-Isotopenverhältnisse herangezogen werden, da die Böden verschiedener Weinbaugebiete, und damit die dort gezogenen Weine, jeweils spezifische Verhältnisse aufweisen. Einige erfolgreiche Anwendungen werden demonstriert.相似文献
87.
P Kn?bl G Schernthaner C Schnack P Pietschmann A Griesmacher R Prager M Müller 《Canadian Metallurgical Quarterly》1993,36(10):1045-1050
Parameters of haemostasis, endothelial cell markers and lipid peroxide levels were studied in 64 Type 1 (insulin-dependent) and 94 Type 2 (non-insulin-dependent) diabetic patients according to their urinary albumin excretion rate in comparison with age-matched control subjects. We determined plasma levels of fibrinogen (Clauss' method), coagulation factor VII:activity (clotting assay), factor VII antigen, protein C and S antigen, von Willebrand factor antigen, D-dimer concentration (ELISA), and lipid peroxide levels (thiobarbituric acid) in relation to urinary albumin excretion rate (RIA). Significant positive correlations were found between urinary albumin excretion rate and plasma fibrinogen (p < 0.005, p < 0.02), factor VII activity (p < 0.0002, p < 0.002), factor VII antigen (p < 0.0001, p < 0.001), protein C (p < 0.003, p < 0.05), and lipid peroxides (p < 0.02, p < 0.004) in Type 1 as well as in Type 2 diabetes. Von Willebrand factor (p < 0.001) and protein S (p < 0.0005) correlated with albuminuria only in patients with Type 1 diabetes. Although most of the haemostatic abnormalities are already found in normoalbuminuric patients, the significant positive correlations to urinary albumin excretion indicate that endothelial cell damage and coagulation disorders deteriorate with the progression of diabetic nephropathy. 相似文献
88.
Theophylline pellets were coated with Eudragit RS 30 D in a miniature fluid-bed pan coater called MiniWiD developed recently. The dispersions were plasticized with varying amounts of triethyl citrate (TEC), dibutyl phthalate (DBP), and polyethylene glycol 6000 (PEG) and applied at different temperatures ranging from 25 to 45 °C. Theophylline release was tested by dissolution using the USP Apparatus 2 (paddle) in 0.1 N hydrochloric acid under sink conditions over 6 hours.
At a coating level of 4 % (0.7 mg/cm2) sustained-release profiles were obtained from dispersions plasticized with TEC or DBP. By reducing the amount of plasticizer from 20 to 10%, films with higher permeabilities were obtained. This effect was compensated by tempering the pellets at 50 deg;C for 24 hours. The coating temperature had little effect on the dissolution profiles of TEC-plasticized films and no effect on films with DBP.
Coatings plasticized with 20% PEG were applied at temperatures ranging from 25 to 45 °C. These films required a coating level of about 18 % (3.3 mg/cm2) to provide comparable sustained-release properties. In contrast to DBP and TEC, a strong influence of the coating temperature on the release rates was observed in which higher temperatures led to slower release rates. This behavior can be explained by the minimum film-forming temperature (MFT). Since PEG does not lower the MFT of Eudragit RS 30 D, the application of these films below the MFT of 45 °C is associated with a lower degree of film formation. 相似文献
At a coating level of 4 % (0.7 mg/cm2) sustained-release profiles were obtained from dispersions plasticized with TEC or DBP. By reducing the amount of plasticizer from 20 to 10%, films with higher permeabilities were obtained. This effect was compensated by tempering the pellets at 50 deg;C for 24 hours. The coating temperature had little effect on the dissolution profiles of TEC-plasticized films and no effect on films with DBP.
Coatings plasticized with 20% PEG were applied at temperatures ranging from 25 to 45 °C. These films required a coating level of about 18 % (3.3 mg/cm2) to provide comparable sustained-release properties. In contrast to DBP and TEC, a strong influence of the coating temperature on the release rates was observed in which higher temperatures led to slower release rates. This behavior can be explained by the minimum film-forming temperature (MFT). Since PEG does not lower the MFT of Eudragit RS 30 D, the application of these films below the MFT of 45 °C is associated with a lower degree of film formation. 相似文献
89.
Peter Fleischmann Ingo Janiszczak 《Applicable Algebra in Engineering, Communication and Computing》1996,7(3):221-234
In this paper an algorithm is presented to determine the number of semisimple conjugacy classes for a given centralizertype for the Chevalley groupsSL
n(q) andSU
n(q). Moreover we give the exact number of regular semisimple classes of this groups and a summary of results on the generic classnumber of exceptional Chevalley groups of adjoint type.The first author acknowledges financial support by a grant of the Deutsche Forschungsgemeinschaft 相似文献
90.