全文获取类型
收费全文 | 8533篇 |
免费 | 608篇 |
国内免费 | 311篇 |
专业分类
电工技术 | 187篇 |
综合类 | 399篇 |
化学工业 | 1645篇 |
金属工艺 | 501篇 |
机械仪表 | 243篇 |
建筑科学 | 315篇 |
矿业工程 | 62篇 |
能源动力 | 189篇 |
轻工业 | 3354篇 |
水利工程 | 26篇 |
石油天然气 | 155篇 |
武器工业 | 32篇 |
无线电 | 574篇 |
一般工业技术 | 474篇 |
冶金工业 | 244篇 |
原子能技术 | 134篇 |
自动化技术 | 918篇 |
出版年
2024年 | 36篇 |
2023年 | 130篇 |
2022年 | 287篇 |
2021年 | 271篇 |
2020年 | 251篇 |
2019年 | 249篇 |
2018年 | 233篇 |
2017年 | 271篇 |
2016年 | 309篇 |
2015年 | 331篇 |
2014年 | 456篇 |
2013年 | 609篇 |
2012年 | 693篇 |
2011年 | 714篇 |
2010年 | 492篇 |
2009年 | 509篇 |
2008年 | 446篇 |
2007年 | 538篇 |
2006年 | 452篇 |
2005年 | 351篇 |
2004年 | 295篇 |
2003年 | 266篇 |
2002年 | 255篇 |
2001年 | 202篇 |
2000年 | 152篇 |
1999年 | 91篇 |
1998年 | 84篇 |
1997年 | 80篇 |
1996年 | 61篇 |
1995年 | 45篇 |
1994年 | 38篇 |
1993年 | 40篇 |
1992年 | 28篇 |
1991年 | 16篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1959年 | 2篇 |
排序方式: 共有9452条查询结果,搜索用时 15 毫秒
11.
A. Murua 《Computing》1997,59(1):43-61
A class of half-explicit methods for index 2 differential-algebraic systems in Hessenberg form is proposed, which takes advantage
of the partitioned structure of such problems. For this family of methods, which we call partitioned half-explicit Runge-Kutta
methods, a better choice in the parameters of the method than for previously available half-explicit Runge-Kutta methods can
be made. In particular we construct a family of 6-stage methods of order 5, and determine its parameters (based on the coefficients
of the successful explicit Runge-Kutta method DOPRI5) in order to optimize the local error coefficients. Numerical experiments
demonstrate the efficiency of this method for the solution of constrained multi-body systems. 相似文献
12.
An endoprotease was purified from melon fruit (Cucumis melo L.) by ammonium sulfate precipitation, gel filtration and ion-exchange chromatography using t-butyloxycarbonyl-Ala-Ala-Pro-Leu p-nitroanilide as a substrate. The molecular weight was estimated as 26,000 and isoelectric point pH 9.5. It preferentially hydrolyzed peptide bonds of the carboxyl terminal sides of Leu, Ala, His, Gin, and Am. Activity was strongly inhibited by diisopropyl phosphofluoridate, indicating the serine protease nature of the enzyme. The migration distance on electrophoresis, molecular weight and substrate specificity differed from cucumisin, a known protease from melon. This unusual protease may have potential for special food treatment applications. 相似文献
13.
An experimental investigation under cold condition was made to study the effects of some operating/design parameters and non-mechanical L valve configuration on the solid circulation rate in a 4.5 m tall, 0.15 m diameter circulating fluidized bed with riser flow rate varying from 1400 litres/min to 2000 litres/min and bed inventory from 15 kg to 25 kg of sand of average sizes 200 μm, 400 μm and 500 μm. Solid circulation rate was estimated by measuring velocity of sand particle travelling through a vertical Perspex tube section at the bottom of the return leg. It was found to be in the range of 2.8 to 12.3kg/m2s, 0.07 to 9.1kg/m2s and 0.12 to 2.23kg/m2s for sand sizes of 200 μm, 400 μm and 500 μm, respectively for a horizontal L valve. Two mathematical correlations have been developed from the experimental results to predict solid circulation rate as a function of riser flow rate, aeration flow rate, total bed inventory and particle size used. 相似文献
14.
HCPL-260L/060L是美国安捷伦科技有限公司推出的高速数字光电耦合器。该器件的逻辑电平与LVTTL/LVCMOS兼容 ,并具有输出使能端。文中详细介绍了HCPL -260L/060L的引脚功能、内部结构、主要特点、使用要求和注意事项 ,给出了它与LVTTL器件的典型接口电路及隔离的3.3VRS232接口电路。 相似文献
15.
16.
Hamidreza Alighourchi Mohsen Barzegar Soleiman Abbasi 《European Food Research and Technology》2008,227(3):881-887
Anthocyanins (ACs) are phenolic compounds that are distributed widely in fruits and vegetables. Apart from imparting color
to plants, ACs also have an array of health-promoting benefits. In this research, the amounts of major ACs of 15 pomegranate
(Punica granatum L.) varieties obtained from Yazd province were determined. The major ACs detected in the studied varieties were as follows:
delphinidin 3-glucoside (2.19–16.29 mg/L), delphinidin 3,5-diglucoside (2.36–63.07 mg/L), pelargonidin 3-glucoside (0.26–1.36 mg/L),
pelargonidin 3,5-diglucoside (0.01–8.11 mg/L), cyanidin 3-glucoside (5.78–30.38 mg/L), and cyanidin 3,5-diglucoside (4.39–166.32 mg/L).
The effect of storage time of unprocessed and pasteurized juices on ACs content of four selected varieties was also studied.
Average degradation percentage of each AC was between 23.0 and 83.0% during 10 days at 4 °C. Moreover, in pasteurized juices
average degradation of ACs was 42.8 ± 0.5% after 10 weeks storage at 4 °C. 相似文献
17.
Development of adolescent reading comprehension in language 1 and language 2: A longitudinal analysis of constituent components. 总被引:1,自引:0,他引:1
van Gelderen Amos; Schoonen Rob; Stoel Reinoud D.; de Glopper Kees; Hulstijn Jan 《Canadian Metallurgical Quarterly》2007,99(3):477
This study investigated the relationship between reading comprehension development of 389 adolescents in their dominant language (Language 1 [L1], Dutch) and a foreign language (Language 2 [L2], English). In each consecutive year from Grades 8 through 10, a number of measurements were taken. Students' reading comprehension, their linguistic knowledge (vocabulary and grammar knowledge) and processing efficiency (speed of word recognition and sentence comprehension) in both languages, and their metacognitive knowledge about reading were assessed. The relative strengths of the effects of these components of reading were analyzed to distinguish among 3 hypotheses about the relationship between L1 and L2 reading comprehension: the transfer hypothesis, the threshold hypothesis, and the processing efficiency hypothesis. The transfer hypothesis predicts a strong relationship between L1 and L2 reading comprehension and a strong effect of metacognitive knowledge on L2 reading comprehension, whereas the threshold and processing efficiency hypotheses predict a more important role of language-specific knowledge and processing skills. Results support the transfer hypothesis, although language-specific knowledge and fluency also contribute to L2 reading performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
用WAXD和FT-IR对高温超高压处理前后的HDPE进行了研究。发现经5.0GPa的高压处理或200℃下4.0GPa的高压同时处理后的HDPE分子链的化学结构未发生变化。HDPE晶体中(200)面与(110)面衍射峰的峰高比(γ)随着压力的升高而增大,表明HDPE分子链在超高压作用下发生了取向排列,且升高温度更有利于这种取向排列,但当压力增大至5.0GPa及温度升高至200℃时,γ反而大幅度下降。 相似文献
19.
S. Sen 《Journal of Fusion Energy》2007,26(1-2):179-183
A novel technique is proposed for creating transport barriers by the rf waves. This is that the transport barriers can be
created by the rf induced ponderomotive force itself and no rf induced flow shear generation is necessary. It is demonstrated that the ponderomotive force of the rf waves can stabilize
the ion temperature gradient (ITG) mode, considered nowadays as the dominant source of anomalous energy losses in the low
confinement (L) mode. It is also shown that this stabilization can be achieved for rather modest values of the rf power and
hence should be easily obtained in actual experiments.
相似文献
20.
Y. P. Boglaev 《Computing》1993,51(3-4):185-207
We consider parallel computing methods for ODEs based on the potential parallelism of convolution algorithms. Detailed presentations of fast convolution algorithms are provided. Implementations of our methods on signal processors and special processors are described. The main emphasis is concentrated on applications of powerful parallel signal processing facilities in ODE computations. By using convolution algorithms we show some treatments of parallel computing in finite fields. As an example of our approach we discuss integrating Lorenz's model.
Zusammenfassung Wir behandeln parallele numerische Methoden für gewöhnliche Differentiagleichungen, die auf Parallelismus von konvolutiven Algorithmen basieren. Ausführliche Darstellungen der schnellen konvolutiven Berechnungen mit spezieller Hardware werden präsentiert. Der Schwerpunkt dieser Arbeit ist die Anwendung von leistungsfähigen parallelen Signal-Prozessoren in der Berechnung gewöhnlicher Differentialgleichungen. Unter Verwendung von Konvolutiven Algorithmen erläutern wir einige Anwendungen von parallelem Rechnen in endlichen Körpern. Als Beispiel unseres Zugangs diskutieren wir die Integration des Lorenz-Modells.相似文献