全文获取类型
收费全文 | 4808篇 |
免费 | 382篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 42篇 |
综合类 | 4篇 |
化学工业 | 1148篇 |
金属工艺 | 63篇 |
机械仪表 | 125篇 |
建筑科学 | 152篇 |
矿业工程 | 12篇 |
能源动力 | 120篇 |
轻工业 | 898篇 |
水利工程 | 55篇 |
石油天然气 | 20篇 |
无线电 | 171篇 |
一般工业技术 | 741篇 |
冶金工业 | 814篇 |
原子能技术 | 21篇 |
自动化技术 | 807篇 |
出版年
2024年 | 24篇 |
2023年 | 59篇 |
2022年 | 83篇 |
2021年 | 170篇 |
2020年 | 168篇 |
2019年 | 145篇 |
2018年 | 241篇 |
2017年 | 241篇 |
2016年 | 270篇 |
2015年 | 183篇 |
2014年 | 228篇 |
2013年 | 446篇 |
2012年 | 314篇 |
2011年 | 298篇 |
2010年 | 228篇 |
2009年 | 246篇 |
2008年 | 192篇 |
2007年 | 216篇 |
2006年 | 106篇 |
2005年 | 99篇 |
2004年 | 89篇 |
2003年 | 90篇 |
2002年 | 64篇 |
2001年 | 39篇 |
2000年 | 28篇 |
1999年 | 40篇 |
1998年 | 273篇 |
1997年 | 151篇 |
1996年 | 107篇 |
1995年 | 71篇 |
1994年 | 53篇 |
1993年 | 46篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1977年 | 12篇 |
1976年 | 19篇 |
1975年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有5193条查询结果,搜索用时 0 毫秒
1.
2.
3.
Summary The influence of draw ratio on macroscopic and crystallographic density of polyethylene with different initial morphologies, has been investigated by solid-state extrusion. An initial drop followed by an increase in macroscopic density as a function of draw ratio has been observed. Since precision X-ray measurements of unit cell parameters showed no variation of crystallographic density, it was concluded that plastic deformation of polyethylene upon drawing proceeds with a decrease of the degree of crystallinity. This was confirmed by differential scanning calorimetry. 相似文献
4.
5.
Martín A. Rodríguez Ricardo M. Carranza Raúl B. Rebak 《Metallurgical and Materials Transactions A》2005,36(5):1179-1185
Alloy 22 (N06022) is the current candidate alloy used to fabricate the external wall of the high-level nuclear waste containers
for the Yucca Mountain repository. It was of interest to study and compare the general and localized corrosion susceptibility
of Alloy 22 in fluoride and chloride solutions at 90 °C. Standard electrochemical tests such as cyclic potentiodynamic polarization,
amperometry, and electrochemical impedance spectroscopy were used. Studied variables included the solution pH and the alloy
microstructure (thermal aging). Results show that Alloy 22 is highly resistant to general corrosion in all the solutions tested.
Thermal aging is not detrimental and even seems to be slightly beneficial for general corrosion at the higher solution pHs.
Pitting corrosion was never observed. Crevice corrosion was found only for high chloride-containing solutions after anodic
polarization. The presence of fluoride ions together with chloride ions seems to increase the susceptibility of Alloy 22 to
crevice corrosion compared to pure chloride solutions.
This article is based on a presentation made in the symposium “Effect of Processing on Materials Properties for Nuclear Waste
Disposition,” November 10–11, 2003, at the TMS Fall meeting in Chicago, Illinois, under the joint auspices of the TMS Corrosion
and Environmental Effects and Nuclear Materials Committees. 相似文献
6.
Mass media--friend or foe? Radio, television, and/or the printed word regularly enter most of the world's households. With a better understanding between health workers and those who produce what we hear, see and read, positive messages could do much to change the habits the jeopardize health. Clear, accurate information is the first step towards improvement. 相似文献
7.
MC Bueno Jayme Gallani RC Rodrigues Colombo E de Araújo Cintra S Brunelli Rigacci 《Canadian Metallurgical Quarterly》1996,4(2):179-199
The overall purpose of this study was to explore nurses' feelings about the applicability and adequacy of a pilot model of nursing assessment (PMNA) developed for coronary care units (CCU) in order to obtain data that could help in establishing a definitive model. The evaluation, performed by 11 CCU nurses, showed that they considered the development and implementation of PMNA as valuable, and that its design was adequate for interviewing cardiac patients. These results will be employed in the elaboration of a definitive model of nursing assessment. 相似文献
8.
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
9.
10.
Peter Eaton Andrea Ragusa Caroline Clavel Cristina T Rojas Paul Graham Raúl V Durán Soledad Penadés 《IEEE transactions on nanobioscience》2007,6(4):309-318
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents. 相似文献