全文获取类型
收费全文 | 34526篇 |
免费 | 1223篇 |
国内免费 | 117篇 |
专业分类
电工技术 | 452篇 |
综合类 | 230篇 |
化学工业 | 6353篇 |
金属工艺 | 749篇 |
机械仪表 | 694篇 |
建筑科学 | 1320篇 |
矿业工程 | 99篇 |
能源动力 | 1072篇 |
轻工业 | 4326篇 |
水利工程 | 285篇 |
石油天然气 | 163篇 |
武器工业 | 8篇 |
无线电 | 2611篇 |
一般工业技术 | 5037篇 |
冶金工业 | 7416篇 |
原子能技术 | 279篇 |
自动化技术 | 4772篇 |
出版年
2023年 | 169篇 |
2022年 | 540篇 |
2021年 | 852篇 |
2020年 | 590篇 |
2019年 | 688篇 |
2018年 | 768篇 |
2017年 | 839篇 |
2016年 | 812篇 |
2015年 | 648篇 |
2014年 | 984篇 |
2013年 | 1750篇 |
2012年 | 1480篇 |
2011年 | 1907篇 |
2010年 | 1415篇 |
2009年 | 1438篇 |
2008年 | 1408篇 |
2007年 | 1233篇 |
2006年 | 1022篇 |
2005年 | 1028篇 |
2004年 | 1094篇 |
2003年 | 982篇 |
2002年 | 970篇 |
2001年 | 787篇 |
2000年 | 621篇 |
1999年 | 619篇 |
1998年 | 2122篇 |
1997年 | 1413篇 |
1996年 | 1018篇 |
1995年 | 699篇 |
1994年 | 575篇 |
1993年 | 622篇 |
1992年 | 309篇 |
1991年 | 347篇 |
1990年 | 302篇 |
1989年 | 284篇 |
1988年 | 267篇 |
1987年 | 216篇 |
1986年 | 246篇 |
1985年 | 274篇 |
1984年 | 206篇 |
1983年 | 184篇 |
1982年 | 200篇 |
1981年 | 207篇 |
1980年 | 187篇 |
1979年 | 167篇 |
1978年 | 132篇 |
1977年 | 203篇 |
1976年 | 283篇 |
1975年 | 148篇 |
1973年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
61.
Jing Wang Walker D.M. Xiang Lu Majhi A. Kruseman B. Gronthoud G. Villagra L.E. van de Wiel P.J.A. Eichenberger S. 《Design & Test of Computers, IEEE》2007,24(3):226-234
Excessive power supply noise during test can cause overkill. This article discusses two models for supply noise in delay testing and their application to test compaction. The proposed noise models avoid complicated power network analysis, making them much faster than existing power noise analysis tools. can cause performance degradation and 相似文献
62.
Hemagglutinins present in Amaranthus leucocarpus seed meal were extracted with saline buffer and nutritive value was estimated by PER, NPR as well as Digestible Energy Consumption Evaluations. Protein digestibility was determined both in vitro and in vivo. Trypsin inhibitor activity was also determined. Saline-extracted Amaranth meal had significantly higher PER and NPR values than whole meal (p<0.05). There were no significant differences in digestible energy (Kcal/day/ animal) and protein consumption (g/day/animal) between diets (p<0.05). A. leucocarpus improves in nutritive value after the saline extraction procedures and has a good potential as a complementary food due to its lysine content. In addition purified agglutinin may be a useful biochemical. 相似文献
63.
Transport problems typically involve at least two types of constraints, on income and on time. Therefore, the indirect utility
function depends either on the income available after having subtracted the cost of the discrete alternative and on the free
time left after having worked and travelled by each competing option. In the typical linear-in-the-attributes and in-the-parameters
specification, that represents the first grade approximation of the indirect utility function, the effect of income and time
constraints cancel out and only the cost and time of the alternatives matter in the comparison between them. From a microeconomic
point of view this is equivalent to assume that income and time effects could be disregarded; which is not always the case.
To account for these effects the utility function should include second order attributes; however, in non-linear utility functions
it may not be easy to distinguish among several effects that could be relevant: direct preferences for good and leisure, and
simple interactions between attributes other than income and time effects. This paper analyses these effects from a theoretical
point of view focusing on the possible confounding problem in detecting income and time effects. We use a dataset collected
for a modal choice context and containing both revealed and stated preference data, and estimate several NL models examining
the effect of the different second-order terms on detecting income and time effects. We compared specifications including
square cost and time attributes, interactions between time and cost, cost divided by the income available to be spent on free
time, and time multiplied by free time. Our results confirm the strong effect of direct preferences for goods and leisure
time on choice, and the potential confounding effect between quadratic attributes and other non-linear omitted terms. Finally,
we also found that care should be taken in highlighting income and time effects using mixed data sources, since confounding
effects can occur when non-linearities are accounted for in both data sets. 相似文献
64.
65.
David N. Johnson Alan A. Johnson 《Fatigue & Fracture of Engineering Materials & Structures》1985,8(3):287-294
The results of Stan ton and Bairstow (1908) have been reanalyzed to yield information on the composition dependence of the low cycle impact fatigue properties of pearlitic plain carbon steels. It has been found that the energy absorbed per impact, Ei, and the number of impacts are failure, Nf, are related by the equation: In this equation q is determined by the carbon, manganese and silicon contents of the steel; Eo is the impact endurance limit; and C and D are constants. The curve represented by this equation intersects that representing the Johnson-Keller high cycle impact fatigue equation at a value of logeNf equal to 1/C. Thus, the transition from low to high cycle impact fatigue occurs at this value of logeNf. 相似文献
66.
67.
Martin E. Valdez H. Shibata Alan W. Cramb 《Metallurgical and Materials Transactions B》2006,37(6):959-965
The objective of this study is to determine the conditions under which the inclusions present in liquid steel can act as heterogeneous
nucleants for solidification. In order to study the factors that define the undercooling of a given metal/oxide couple, the
undercooling of a pure iron sessile droplet in contact with Al2O3, ZrO2, and MgO substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The results
showed that the undercooling of iron, in contact with a particular substrate, did not have a unique value, but was significantly
affected by the oxygen content on the gas phase. For oxygen partial pressures between 10−21 and 10−19, the undercooling of iron on ZrO2 substrates was stable and around 290 °C. In the same range of oxygen partial pressure, the undercooling of iron on MgO substrates
remained below 100 °C due to the low stability of this oxide. At lower oxygen contents, substrate decomposition might be the
cause for the observed drop in the undercooling of iron on ZrO2 substrates to below 100 °C. The undercooling also decreased for increasing oxygen content as verified when the gas was changed
from gettered Ar/Ar-H2 to CO/CO2 mixtures. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deep undercooling
observed in the ZrO2 experiments occurred when the highest contact angle between the liquid metal and the substrate was achieved. 相似文献
68.
Russomanno D.J. de Jongh Curry A.L. Atanasova G.S. Hunt L.C. Goodwin J.C. 《IEEE transactions on information technology in biomedicine》2008,12(1):76-86
DefibViz is a software application developed for defibrillation simulation and visualization. It exploits both surface techniques and methods for the interactive exploration of volumetric datasets for the analysis of transthoracic defibrillation simulation results. DefibViz has a graphical user interface for the specification of the shape, size, position, and applied voltage of a defibrillator's electrodes. An option is provided for using 3D slice plane widgets, which operate on the volumetric datasets, such that the distribution of the voltage gradient induced by an electric shock can be visually inspected in various tissues throughout the myocardium and torso. One goal of DefibViz is to enhance understanding of how electrode parameters relate to the change of the voltage gradient distribution throughout the heart, which may help lead to optimal defibrillator design. DefibViz is significant, in that, it is built by using an open-source graphics and visualization framework providing a platform for subsequent modifiability and extensibility. Moreover, it integrates simulation and visualization techniques, which previously required the running of several independent software executables, into an enhanced, seamless, and comprehensive software application. 相似文献
69.
70.
Talita Moreira de Oliveira Nilda de Fátima Ferreira Soares Rodrigo Magela Pereira Kátia de Freitas Fraga 《Packaging Technology and Science》2007,20(2):147-153
Conservation of food products depends on product quality and packaging suitability. The objective of this work was to develop and evaluate the antimicrobial efficiency of natamycin‐incorporated film in the production process of Gorgonzola cheese. It aims to optimize the production process and increase shelf‐life and food safety for the consumer. Films with different concentrations of natamycin were produced and tested in Gorgonzola cheeses to evaluate its efficiency against Penicillium roqueforti on the cheese surface. Films with 2 and 4% natamycin presented satisfactory results for fungus inhibition and the amount of natamycin released to the cheese was below that allowed by the legislation. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献