全文获取类型
收费全文 | 4034篇 |
免费 | 43篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 34篇 |
综合类 | 2篇 |
化学工业 | 473篇 |
金属工艺 | 36篇 |
机械仪表 | 59篇 |
建筑科学 | 174篇 |
矿业工程 | 15篇 |
能源动力 | 68篇 |
轻工业 | 232篇 |
水利工程 | 12篇 |
石油天然气 | 20篇 |
无线电 | 236篇 |
一般工业技术 | 395篇 |
冶金工业 | 1913篇 |
原子能技术 | 28篇 |
自动化技术 | 384篇 |
出版年
2021年 | 18篇 |
2019年 | 22篇 |
2017年 | 21篇 |
2016年 | 28篇 |
2015年 | 22篇 |
2014年 | 37篇 |
2013年 | 147篇 |
2012年 | 72篇 |
2011年 | 117篇 |
2010年 | 94篇 |
2009年 | 82篇 |
2008年 | 115篇 |
2007年 | 104篇 |
2006年 | 114篇 |
2005年 | 78篇 |
2004年 | 78篇 |
2003年 | 86篇 |
2002年 | 84篇 |
2001年 | 60篇 |
2000年 | 60篇 |
1999年 | 93篇 |
1998年 | 392篇 |
1997年 | 221篇 |
1996年 | 180篇 |
1995年 | 143篇 |
1994年 | 120篇 |
1993年 | 114篇 |
1992年 | 70篇 |
1991年 | 50篇 |
1990年 | 67篇 |
1989年 | 67篇 |
1988年 | 71篇 |
1987年 | 69篇 |
1986年 | 64篇 |
1985年 | 70篇 |
1984年 | 49篇 |
1983年 | 56篇 |
1982年 | 56篇 |
1981年 | 40篇 |
1980年 | 55篇 |
1979年 | 46篇 |
1978年 | 35篇 |
1977年 | 53篇 |
1976年 | 83篇 |
1975年 | 43篇 |
1974年 | 44篇 |
1973年 | 34篇 |
1972年 | 26篇 |
1971年 | 17篇 |
1970年 | 17篇 |
排序方式: 共有4081条查询结果,搜索用时 46 毫秒
61.
Lavine Howard; Huff Joseph W.; Wagner Stephen H.; Sweeney Donna 《Canadian Metallurgical Quarterly》1998,75(2):359
In 3 experiments, the authors assessed whether attitude strength moderates the susceptibility of attitudes to item context effects in surveys. In Experiment 1, respondents completed multiple measures of attitude strength. Three weeks later, respondents participated in a context experiment. Results revealed that respondents with weak attitudes exhibited significantly larger context effect for 1 of 2 issues. In Experiment 2, the results of Experiment 1 were conceptually replicated by use of measures of interattitudinal embeddedness to assess attitude strength. In Experiment 3, significant strength-moderated context effects were found when attitude strength was assessed in a multi-item, multidimensional manner but not when it was assessed with a single item. Discussion focuses on measurement and theoretical issues related to the moderation and mediation of context effects in attitude surveys. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
62.
63.
JP Edwards SJ West CL Pooley KB Marschke LJ Farmer TK Jones 《Canadian Metallurgical Quarterly》1998,8(7):745-750
Typhoid fever is often associated with abnormal liver biochemical tests, but severe hepatic involvement with a clinical feature of acute hepatitis is a rare complication. There have been more than 150 cases of salmonella hepatitis reported from both developed and developing countries. The documented incidence varies widely from less than 1% to 26% patients with enteric fever. The possible associated factors for development of salmonella hepatitis are virulence of the organisms, delayed treatment and poor general health of the patients. The pathogenesis of severe hepatic involvement in salmonella infection may be multifactorial and includes endotoxin, local inflammatory and/or host immune reactions. Clinical jaundice in salmonella hepatitis usually occurs within the first 2 weeks of the febrile illness. Hepatomegaly and moderate elevation of transaminase levels are common findings. Extreme hepatic dysfunction with hepatic encephalopathy is a rare coexisting complication in salmonella hepatitis. A positive culture for salmonella from blood or stool is essential to differentiate salmonella hepatitis from other causes of acute hepatitis. Hepatic pathology is characterized by the presence of typhoid nodules with marked hyperplasia of reticuloendothelial cells. The prognosis is usually good as salmonella hepatitis responds well to a specific antibiotic therapy and juandice resolves with clinical improvement. The clinical course can be severe with a mortality rate as high as 20%, particularly with delayed treatment or in patients with other complications of salmonella infection. As enteric fever is a common infection, the recognition of salmonella hepatitis is of clinical importance. 相似文献
64.
65.
Stanley M. Howard 《Metallurgical and Materials Transactions B》1989,20(6):845-852
The primary objective of this investigation was to demonstrate a new method of measuring activities. The mass spectrometric
analysis of effusates from a unique valved Knudsen cell was used to determine the activity of Ag in the liquid Ag−Cu system
at 1400 K. The alloy compositions were varied from one composition extreme to the otherin situ. The system exhibits positive deviation from ideal behavior, and the results are in agreement with previous investigations
and are summarized by the equation
相似文献
66.
67.
68.
Hunter S Howard M Marki P Gelpi MJ Francone J Reed G McGinty K Mayes B Ysmael R Johnson C 《Food management》1992,27(1):92-5, 98
Consumer confidence is at its lowest ebb since 1980. Economic growth is at a standstill & unemployment & inflation are both rising. Here's a front-line report from more than three dozen operators who are fending off the recession's dual pressures of slow sales & rising costs. They are using discount pricing, partnering with vendors, setting pay for performance standards & a variety of other recession-beating practices. 相似文献
69.
Howard W. Starkweather Thomas F. Jordan Gordon B. Dunnington 《Polymer Engineering and Science》1974,14(10):678-681
The yield stress is a simple function of the deformation ratio in the direction of testing for specimens oriented by uniaxial or biaxial stretching or rolling. Unless the yield stress increases more rapidly than in proportion to the deformation ratio, there will be instability during tensile creep under high loads. The relative merit of various polymers differs for creep and stress relaxation. Fatigue and bend recovery are also related to the molecular structure. 相似文献
70.
Ralph W. Howard C. A. McDaniel Dennis R. Nelson Gary J. Blomquist Leslie T. Gelbaum Leon H. Zalkow 《Journal of chemical ecology》1982,8(9):1227-1239
The cuticular hydrocarbon components of four castes ofReticulitermes virginicus (Banks) have been identified and quantitated. Components identified includen-alkanes; 2-, 3-, 11-, 13-, and 15-methyl-alkanes; 11,15-dimethylalkanes, (Z)-9-alkenes; (Z,Z)-7,9-dienes; and (E/Z)-6,9-dienes ranging in carbon number from C21 to C40. All caste forms ofR.virginicus contained the same components, but showed caste-specific proportions. Comparison of these hydrocarbons with those of the sympatric termiteR. flavipes (Kollar) suggest that cuticular hydrocarbons might serve as species- and caste-recognition cues. A bioassay was developed to test this species-recognition hypothesis, with the experimental results supporting the hypothesis.Isoptera: Rhinotermitidae. 相似文献
|