全文获取类型
收费全文 | 4781篇 |
免费 | 200篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 38篇 |
综合类 | 15篇 |
化学工业 | 815篇 |
金属工艺 | 122篇 |
机械仪表 | 71篇 |
建筑科学 | 192篇 |
矿业工程 | 32篇 |
能源动力 | 139篇 |
轻工业 | 559篇 |
水利工程 | 43篇 |
石油天然气 | 7篇 |
无线电 | 427篇 |
一般工业技术 | 653篇 |
冶金工业 | 1130篇 |
原子能技术 | 26篇 |
自动化技术 | 721篇 |
出版年
2023年 | 25篇 |
2022年 | 35篇 |
2021年 | 72篇 |
2020年 | 75篇 |
2019年 | 69篇 |
2018年 | 105篇 |
2017年 | 118篇 |
2016年 | 130篇 |
2015年 | 89篇 |
2014年 | 119篇 |
2013年 | 279篇 |
2012年 | 178篇 |
2011年 | 243篇 |
2010年 | 214篇 |
2009年 | 209篇 |
2008年 | 241篇 |
2007年 | 243篇 |
2006年 | 192篇 |
2005年 | 143篇 |
2004年 | 145篇 |
2003年 | 141篇 |
2002年 | 117篇 |
2001年 | 85篇 |
2000年 | 82篇 |
1999年 | 78篇 |
1998年 | 300篇 |
1997年 | 179篇 |
1996年 | 128篇 |
1995年 | 95篇 |
1994年 | 78篇 |
1993年 | 90篇 |
1992年 | 49篇 |
1991年 | 40篇 |
1990年 | 35篇 |
1989年 | 44篇 |
1988年 | 38篇 |
1987年 | 43篇 |
1986年 | 29篇 |
1985年 | 39篇 |
1984年 | 32篇 |
1983年 | 36篇 |
1982年 | 26篇 |
1981年 | 21篇 |
1980年 | 23篇 |
1978年 | 17篇 |
1977年 | 21篇 |
1976年 | 32篇 |
1975年 | 33篇 |
1973年 | 15篇 |
1972年 | 16篇 |
排序方式: 共有4990条查询结果,搜索用时 15 毫秒
21.
Grant Lewison 《Scientometrics》2007,72(3):439-458
This paper describes an analysis of coverage of the risks from agricultural and food genetically-modified organisms (GMOs)
from April 2002 to April 2004 in 14 news media from six countries (Canada, France, Germany, Spain, the UK and the USA) which
was conducted as part of a review for the European Commission of the management of risk communication. A total of 597 relevant
news articles were found and coded for their presentational tone, the types of risk (environmental, financial, health and
political, in that order), the organisms described (mainly maize, rape and beet crops), and the documents, people and organisations
cited. UK news media tended to be the most “scary” and Spanish ones the most “robust”. Articles quoting public perceptions,
non-governmental environmental organisations and politicians tended to emphasize the risks of GMOs; those quoting scientists
tended to downplay the risks and describe their potential benefits. Some suggestions for possible action by the European Commission
are put forward, such as the facilitation of contact between journalists and scientists, but it is recognized that for some
newspapers, their editorial wish to campaign will inevitably over-ride their reporters’ wish to present the truth. 相似文献
22.
The main purpose of the study reported here was to investigate the relative importance of complexity of syllable structure and task differences in measuring phonological awareness in low-literacy adults. This study is a replication of a study with children conducted by S. A. Stahl and B. A. Murray (1994). Results indicated that the complexity of syllable structure did indeed better describe the construct of phonological awareness in low-literacy adults. At the same time, the authors also found some differences in the pattern of literacy acquisition for their Spanish adults in comparison with child literacy acquisition in English. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
Jim Durcan 《电子产品世界》2003,(24):42,78
随着对新一代电路交换移动网络的资金投入及其频谱成本的不断增加,移动通信运营商们正在谨慎地向前继续迈进,计划向企业和大众消费市场推出无线数据服务。如果移动通信运营商想成功地让大众消费市场接纳无线数据业务,就必须找到一种新的技术解决方案,克服电路交换式架构遗留下来的障碍,进而采用端到端的包交换网络系统,这种系统能够在不同投资规模下提供有利可图的无线数据服务。突发性是数据流量的特征,也就是说数据流到达的时间、到达的速率、以及信息的比特数,在不同的时间里会有很大的变化。并且,数据应用需要传输非常可靠,实际上不能允… 相似文献
24.
E García R Calvo JM Rodríguez-Sasiaín R Jiménez IF Trocóniz E Suárez 《Canadian Metallurgical Quarterly》1995,39(8):1019-1023
The influence of altered protein binding on the neuromuscular effect of atracurium has been studied in rats with experimental inflammation induced by subcutaneous injection of turpentine oil. Doses of atracurium ranging from 0.45 to 1.5 mg.kg-1 were administered to control (n = 30) and to experimental inflammation induced rats (n = 30). Neuromuscular transmission was monitored by recording the twitch tension of the tibialis-anterior muscle elicited by stimulation of the sciatic nerve. Three effect parameters were recorded: (i) intensity of the effect, measured as percentage depression of baseline twitch tension, (ii) duration of drug action (min) and (iii) recovery time (min). The dose-intensity of the effect relationship was modelled using a sigmoid Emax model. The ED50 (effective dose eliciting 50% of the maximum effect) was significantly increased (P < 0.01) in the inflammation group as compared to the control group (0.94 vs. 0.68 mg.kg-1). This change was reflected in a shift of the dose-response curve to the right in the pretreated rats. For equipotent doses ED95 (defined as the effective dose eliciting 95% of maximum effect), no differences were found in recovery time and duration of action between the two groups of rats. Mucoproteins levels (index of alpha 1-acid glycoprotein (AAG) and protein binding were significantly increased in rats with experimental inflammation as compared to control rats. Based on these results, altered serum protein binding of atracurium appears to be responsible, at least in part, for the resistance to atracurium. 相似文献
25.
Button Cathryn M.; Grant Malcolm J.; Hannah T. Edward; Ross Abraham S. 《Canadian Metallurgical Quarterly》1993,25(2):230
Two studies identified and labeled the dimensions that people use to judge others' attitudes. In the 1st study, 50 male and 50 female undergraduates viewed pairs of attitude statements drawn from 1 or 2 large sets. For each pair of statements, Ss judged whether or not a person who agreed with one statement in the pair would be likely to agree with the other. The dimensions of liberalism and traditional values were found to underlie perceived attitudes. Validity was confirmed in a 2nd study with 60 male and 60 female undergraduates who rated the characteristics of hypothetical people who agreed strongly with particular statements. Results suggest that there is a common structure to people's perceptions of others' attitudes. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
26.
27.
George Grant Fiona Greer Norma H. McKenzie Arpad Pusztai 《Journal of the science of food and agriculture》1985,36(5):409-414
In a series of 10-day pair feeding experiments it was found that the nutritional value of diets containing beans was essentially the same for rats aged between 30 and 123 days. Thus net protein utilisation (NPU) values of 25–39 on diets containing Processor bean (35 g protein kg?1) + egg albumin (65g protein kg?1) were obtained. As food intakes were considerably reduced when rats were fed diets containing more than 35g protein kg?1 of Processor bean, the measurement of protein utilisation became increasingly more difficult. The severe disruption of the brush borders of duodenal and jejunal enterocytes, originally observed when bean-containing diets were fed to young (30-day-old) rats was also found with rats up to the age of 120 days on similar diets. Similarly, the development of circulating anti-lectin antibodies in the animals showed no age dependence within the age limits investigated. It was also shown that oral immunisation did not protect the rats from the effects of toxicity and that the immune response was a result of continuous absorption of lectin throughout the feeding period. Thus the extent and the mechanism of toxicity of Phaseolus vulgaris bean lectins were found not to be dependent on the age or maturity of the animal. 相似文献
28.
29.
Mathematical models for liquid-liquid extraction processes are not widely available. The correlation of liquid-liquid equilibrium for such a model is often difficult. One correlation, based upon the Redlich-Kister expansion for the molar excess Gibb's free energy, has been shown to accurately represent ternary liquid-liquid equilibrium systems used in liquid-liquid extraction operations.
The use of this correlation in an extraction model was investigated and found to be suitable for a ternary liquid-liquid extraction model with only minor limitations. A successful ternary liquid-liquid extraction model was developed using this equilibrium correlation. 相似文献
The use of this correlation in an extraction model was investigated and found to be suitable for a ternary liquid-liquid extraction model with only minor limitations. A successful ternary liquid-liquid extraction model was developed using this equilibrium correlation. 相似文献
30.