全文获取类型
收费全文 | 2543篇 |
免费 | 57篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 462篇 |
金属工艺 | 49篇 |
机械仪表 | 51篇 |
建筑科学 | 124篇 |
矿业工程 | 7篇 |
能源动力 | 58篇 |
轻工业 | 235篇 |
水利工程 | 35篇 |
石油天然气 | 7篇 |
无线电 | 265篇 |
一般工业技术 | 385篇 |
冶金工业 | 598篇 |
原子能技术 | 19篇 |
自动化技术 | 294篇 |
出版年
2021年 | 24篇 |
2020年 | 19篇 |
2019年 | 29篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 52篇 |
2015年 | 26篇 |
2014年 | 52篇 |
2013年 | 121篇 |
2012年 | 82篇 |
2011年 | 146篇 |
2010年 | 81篇 |
2009年 | 83篇 |
2008年 | 111篇 |
2007年 | 111篇 |
2006年 | 104篇 |
2005年 | 113篇 |
2004年 | 79篇 |
2003年 | 71篇 |
2002年 | 73篇 |
2001年 | 59篇 |
2000年 | 52篇 |
1999年 | 61篇 |
1998年 | 110篇 |
1997年 | 72篇 |
1996年 | 73篇 |
1995年 | 45篇 |
1994年 | 48篇 |
1993年 | 34篇 |
1992年 | 34篇 |
1991年 | 24篇 |
1990年 | 34篇 |
1989年 | 37篇 |
1988年 | 35篇 |
1987年 | 29篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 35篇 |
1983年 | 38篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 23篇 |
1977年 | 21篇 |
1976年 | 22篇 |
1975年 | 23篇 |
1974年 | 20篇 |
1973年 | 17篇 |
1971年 | 11篇 |
排序方式: 共有2606条查询结果,搜索用时 15 毫秒
101.
In 2007, the UK Government announced an ambitious zero-carbon target for all new housing in England. This paper shows how the definition and its associated policies emerged from discourses of environmental policy innovation; how the problem subsequently became framed as one of mainstreaming, consequent upon the apparent success of experimental schemes and defined in more detail through the interaction between pressure group politics and the technical analyses that accompanied the government's consultation exercises. Finally, it shows how regional and local variations in housing and property markets are likely to influence the ease of zero carbon development. The analysis uses concepts drawn from both the science and technology literature and the literature on policy implementation. 相似文献
102.
This study aimed to investigate the rheology of two-mineral mixture systems as a function of pH and solid concentration. Single minerals (nickel oxide, quartz and hematite) and two-mineral systems (nickel oxide–quartz and nickel oxide–hematite) were studied. Rheology tests were conducted to investigate the effect of pH and solid concentration on shear yield stress of suspensions while zeta potential measurements of suspensions were used to explain the rheology results. Rheology results indicated that single mineral experiments showed that 5 and 10 vol.% of quartz and hematite had no shear yield stress whereas the one of nickel oxide was positive value. Shear yield stress of nickel oxide–quartz mixture and nickel oxide–hematite mixtures increased as increasing pH and solid concentration, and the value was higher than the one obtained with only nickel oxide. These results obtained with two-mineral mixture systems were explained by electrokinetic properties of the minerals, i.e. zeta potential of the minerals. 相似文献
103.
104.
Barry C. Arnold Enrique Castillo Jos María Sarabia 《Computational statistics & data analysis》2009,53(12):4555-4569
Two new concepts of order statistics for multivariate samples are introduced. In one of the versions it turns out that not every multivariate order statistic is present in every sample. These order statistics have application in multivariate ranked set sampling and can be used to generate broad classes of multivariate densities in the sense of Jones. In this case the likelihood for the sample values and their corresponding ranks can be calculated based on the conditional density of a multivariate order statistics given its sample value, and such that its integral gives the probability for the multivariate order statistics under discussion to be observed. An alternative version of multivariate order statistics is also introduced, for which multivariate order statistics are always well defined and expressions for their marginal densities are derived. Since these multivariate order statistics are tailor made for multivariate ranked set sampling, their densities allow for parameter inference based on ranked set sampling. Some simulations show that both multivariate order statistics densities can be used with advantage with respect to simple random sampling. 相似文献
105.
Fabian C. Hadipriono Richard E. Larew Barry Wong 《Civil Engineering and Environmental Systems》2013,30(2):99-103
This paper demonstrates the use of a rule-based weighted rating system (RWRS) developed for improving the rating of concrete culverts. RWRS combines the qualitative rating based on a guideline commonly used by the Department of Transportation, the quantitative rating based on a regression model, and the inspector's own judgment on the culvert's rating. Weight on each rating is provided by the supervisor. A case study is presented to demonstrate the use of RWRS. 相似文献
106.
107.
Ulijn RV Janssen AE Moore BD Halling PJ Kelly SM Price NC 《Chembiochem : a European journal of chemical biology》2002,3(11):1112-1116
Thermolysin is catalytically inactive in mixtures of 10-15 % acetonitrile in aqueous buffer. Unexpectedly, dilution of the inactive enzyme with acetonitrile leads to complete recovery of the catalytic activity in a similar way to dilution with aqueous buffer. Circular dichroism and fluorescence studies of thermolysin in the same solvent mixtures reveal discontinuous changes in the overall secondary and tertiary protein structure that correlate well with the reversible differences in catalytic activity. The spectra on either side of the minimum activity point are different from each other, a fact indicating that the enzyme may be able to access two active conformations which are thermodynamically stable in different solvent environments. 相似文献
108.
Investigating the Relations used in Conceptual Combination 总被引:1,自引:0,他引:1
How do people understand noun–noun compounds such as volcano science and pear bowl? In this paper, we present evidence against one approach to noun–noun compounds, namely that of arranging the meanings of compounds into a small, finite taxonomy of general semantic relations. Using a typical relation taxonomy, we conducted an experiment examining how people classify compounds into the taxonomy’s relation categories. We found that people often select not one but several relations for each compound; for example, people classify coffee stain as coffee MAKES stain, stain MADE OF coffee, coffee CAUSES stain and stain DERIVED FROM coffee. A natural metric for relational similarity follows from our experimental data; we found that using cluster analysis to group compounds’ interpretations with respect to this metric produced groupings that were different from the original taxonomic categories, suggesting that there is more than one way to classify the meanings of compounds. We also found that compounds which had similar constituent concepts tended to be interpreted with similar relations, indicating that the intrinsic properties of a compound’s constituent concepts help determine how that compound is interpreted. Such findings are problematic for taxonomic theories of conceptual combination 相似文献
109.
Augmented geophysical data interpretation through automated velocity picking in semblance velocity images 总被引:1,自引:0,他引:1
J. Ross Beveridge Charlie Ross Darrell Whitley Barry Fish 《Machine Vision and Applications》2002,13(3):141-148
Velocity picking is the problem of picking velocity–time pairs based on a coherence metric between multiple seismic signals.
Coherence as a function of velocity and time can be expressed as a 2D color semblance velocity image. Currently, humans pick
velocities by looking at the semblance velocity image; this process can take days or even weeks to complete for a seismic
survey. The problem can be posed as a geometric feature-matching problem. A feature extraction algorithm can recognize islands
(peaks) of maximum semblance in the semblance velocity image: a heuristic combinatorial matching process can then be used
to find a subset of peaks that maximizes the coherence metric. The peaks define a polyline through the image, and coherence
is measured in terms of the summed velocity under the polyline and the smoothness of the polyline. Our best algorithm includes
a constraint favoring solutions near the median solution for the local area under consideration. First, each image is processed
independently. Then, a second pass of optimization includes proximity to the median as an additional optimization criterion.
Our results are similar to those produced by human experts.
Accepted: 15 June 2001 相似文献
110.
Strohmer Douglas C.; Moilanen Donna L.; Barry Lauren J. 《Canadian Metallurgical Quarterly》1988,35(1):56
We report the results of two experiments that examined the way individuals test hypotheses about themselves. Both experiments were based on the work of Snyder (e.g., Snyder, 1981; Snyder & Skrypnek, 1981), which suggests that individuals have a confirmatory bias when testing hypotheses about others and about themselves. In Experiment 1, we examined the extent to which this bias toward confirmation persists when a negative (e.g., depression) or nonconsistent (not consistent with the individual's evaluation of him- or herself) personal hypothesis is tested. Results suggest that the negative or positive nature of a personal hypothesis does not directly influence the way individuals test their hypothesis. However, the way individuals tested personal hypotheses was influenced by hypothesis consistency. In Experiment 2, we examined the relation of a cognitive schematic variable (i.e., vulnerability for depression) and hypothesis testing. Results suggest that vulnerability is related to the way individuals test a personal hypothesis about depression. Vulnerable, low-depression participants were confirmatory when testing a depression hypothesis, whereas nonvulnerable, low-depression participants were disconfirmatory. We discuss implications for counseling and future directions for research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献