全文获取类型
收费全文 | 1896篇 |
免费 | 37篇 |
专业分类
电工技术 | 32篇 |
综合类 | 6篇 |
化学工业 | 338篇 |
金属工艺 | 37篇 |
机械仪表 | 39篇 |
建筑科学 | 96篇 |
矿业工程 | 17篇 |
能源动力 | 54篇 |
轻工业 | 153篇 |
水利工程 | 8篇 |
石油天然气 | 12篇 |
武器工业 | 1篇 |
无线电 | 135篇 |
一般工业技术 | 243篇 |
冶金工业 | 470篇 |
原子能技术 | 14篇 |
自动化技术 | 278篇 |
出版年
2022年 | 10篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 18篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 30篇 |
2014年 | 33篇 |
2013年 | 107篇 |
2012年 | 53篇 |
2011年 | 79篇 |
2010年 | 56篇 |
2009年 | 82篇 |
2008年 | 72篇 |
2007年 | 78篇 |
2006年 | 77篇 |
2005年 | 80篇 |
2004年 | 76篇 |
2003年 | 53篇 |
2002年 | 60篇 |
2001年 | 52篇 |
2000年 | 38篇 |
1999年 | 44篇 |
1998年 | 71篇 |
1997年 | 65篇 |
1996年 | 63篇 |
1995年 | 32篇 |
1994年 | 36篇 |
1993年 | 36篇 |
1992年 | 37篇 |
1991年 | 14篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 20篇 |
1986年 | 20篇 |
1985年 | 29篇 |
1984年 | 32篇 |
1983年 | 24篇 |
1982年 | 20篇 |
1981年 | 21篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1976年 | 33篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 10篇 |
排序方式: 共有1933条查询结果,搜索用时 1 毫秒
1.
2.
本部分将讲述PortletConfig对象及其PortletContext对象的概念及应用。 相似文献
3.
4.
Several N-(phosphonomethyl) amides have previously been reported to act as particularly effective flame retardants for cellulose. It has also been demonstrated previously that the efficiency of a flame retardant on cellulose frequently parallels its ability to phosphorylate cellulosic hydroxyls at elevated temperatures. This study of the hydrolysis and alcoholysis reactions of N-(phosphonomethyl) amides establishes their unique reactivity. An explanation for this high reactivity is proposed on the basis of intramolecular assistance of the attack of water or alcohols at phosphorus by the carbonyl oxygen of the amide moiety. 相似文献
5.
6.
A value-based test is presented for economic screening of electric utility demand-side management (DSM) programs. The widely used least cost test is valid if the programs do not alter the amount or value of energy services provided to customers. But, in general, DSM programs have such effects and, as a result, the value consumers receive is changed. A more general economic efficiency test, the most value test, provides a practical method for considering the effects of DSM on customer value. The version presented allows for multiple load periods and can account for rate impacts on several customer classes. Four typical DSM programs are evaluated as illustrations 相似文献
7.
OBJECTIVES: 1) To quantify the frequency of underrecognized Neisseria gonorrhoeae and Chlamydia trachomatis cervical infections in women tested in the ED, 2) to describe and compare the characteristics of those treated and not treated during the initial visit, and 3) to quantify the delay interval until treatment was provided. METHODS: A 2-year, retrospective consecutive case series was performed from June 1, 1992, to May 31, 1994. There were 148 women with > or = 1 discrete occurrence of culture-proven cervical N. gonorrhoeae or C. trachomatis infection studied. All the patients were evaluated in a university-affiliated, tertiary care hospital-based ED with a large rural referral area. The main outcome measures were the proportions of patients with positive cultures both treated and not treated in the ED, the clinical characteristics of each group, and the proportion remaining untreated or experiencing treatment delays of > 2 weeks after attempted phone, mail, and public health follow-up. RESULTS: Of 157 occurrences of positive cultures for N. gonorrhoeae or C. trachomatis, 86 (53%) were treated with a regimen suggested by the CDC prior to ED release. The proportion of women with isolated C. trachomatis infections that were underrecognized and untreated initially was larger than the proportions with isolated N. gonorrhoeae or combined infections (79% vs 27% and 53%, respectively, p < 0.0001). Women with findings suggestive of advanced disease (history of fever or chills, or examination evidence of temperature > 38 degrees C, purulent vaginal discharge, or any uterine/salpinx/ovarian tenderness) were more often recognized and treated with appropriate antibiotics initially (p = 0.02 to < 0.00001 for all). After phone, mail, and public health follow-up, treatment could not be documented for 25% of the occurrences, in all cases due to an inability to locate the patient. An additional 20% of the women did not receive treatment for 14-60 days. CONCLUSIONS: In this population, both N. gonorrhoeae and C. trachomatis cervical infections are frequently underrecognized in the ED, with isolated C. trachomatis infections associated with significantly higher proportions of underrecognition. Many affected women remain untreated for extended intervals, creating public and individual health risks. Improved point of contact detection, follow-up, and treatment policies are needed to limit these risks. 相似文献
8.
Macroscopic analysis of design processes based on a scheme for coding designers' cognitive actions 总被引:1,自引:0,他引:1
We have devised a new scheme for coding designers' cognitive actions from video/audio design protocols. Designers' actions are coded into four cognitive levels; physical, perceptual, functional and conceptual. Relations between actions belonging to different levels, such as dependencies and triggering relations, are also coded. The present scheme has two benefits. First, we found that design actions are definable in a systematic way using the vocabulary of the scheme, and thus a designer's cognitive behaviours in each of local design stages is represented as a structure composed of defined primitive actions. This is expected to lay the foundation for microscopic analyses of how particular types of actions contribute to the formation of key design ideas. Second, this scheme is suitable for macroscopic analyses of how designers cognitively interact with their own sketches. We examined, for a practising architect, the ways in which drawing, inspection of drawings, perception, and functional thoughts correlated with one another in his design process. The findings suggest that design sketches serve not only as external memory or as a provider of visual cues for association of non-visual information, but also as a physical setting in which design thoughts are constructed on the fly. 相似文献
9.
10.