全文获取类型
收费全文 | 3595篇 |
免费 | 323篇 |
国内免费 | 228篇 |
专业分类
电工技术 | 195篇 |
综合类 | 447篇 |
化学工业 | 275篇 |
金属工艺 | 66篇 |
机械仪表 | 181篇 |
建筑科学 | 285篇 |
矿业工程 | 99篇 |
能源动力 | 79篇 |
轻工业 | 166篇 |
水利工程 | 131篇 |
石油天然气 | 130篇 |
武器工业 | 102篇 |
无线电 | 490篇 |
一般工业技术 | 353篇 |
冶金工业 | 203篇 |
原子能技术 | 15篇 |
自动化技术 | 929篇 |
出版年
2024年 | 5篇 |
2023年 | 33篇 |
2022年 | 62篇 |
2021年 | 78篇 |
2020年 | 88篇 |
2019年 | 85篇 |
2018年 | 67篇 |
2017年 | 107篇 |
2016年 | 121篇 |
2015年 | 138篇 |
2014年 | 200篇 |
2013年 | 252篇 |
2012年 | 241篇 |
2011年 | 293篇 |
2010年 | 188篇 |
2009年 | 218篇 |
2008年 | 219篇 |
2007年 | 246篇 |
2006年 | 217篇 |
2005年 | 170篇 |
2004年 | 148篇 |
2003年 | 157篇 |
2002年 | 113篇 |
2001年 | 92篇 |
2000年 | 87篇 |
1999年 | 60篇 |
1998年 | 44篇 |
1997年 | 56篇 |
1996年 | 58篇 |
1995年 | 36篇 |
1994年 | 38篇 |
1993年 | 29篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 30篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1964年 | 5篇 |
1963年 | 4篇 |
1960年 | 3篇 |
1957年 | 4篇 |
1955年 | 6篇 |
排序方式: 共有4146条查询结果,搜索用时 0 毫秒
1.
均匀设计法分析制备过程对钴钼硫化物催化剂机械强度的影响 总被引:1,自引:1,他引:0
建立了CoMoP/Al2O3加氢精制催化剂机械强度及其可靠性在制备过程中的数学模型,采用均匀设计考察了浸渍、干燥、煅烧、硫化4个制备过程中,浸渍时间、干燥温度、干燥时间、煅烧温度、煅烧时间、硫化温度和硫化升温速率7个实验因子对催化剂强度均值、Weibull模量的影响,同时考察了这些因素对颗粒密度的影响。方差分析表明所有模型都是充足的。实验结果表明,硫化过程是影响催化剂强度均值的主要过程。在实验范围内提高硫化温度、降低硫化时的升温速率有利于提高催化剂的强度。影响催化剂Weibull模量的因素主要为各个制备过程的交互效应。要提高催化剂强度的可靠性就必须全面考虑催化剂制备的各个过程,特别是各个制备过程的交互效应。 相似文献
2.
David L. Hoover 《Computers and the Humanities》2003,37(2):151-178
This article examines the usefulness ofvocabulary richness for authorship attributionand tests the assumption that appropriatemeasures of vocabulary richness can capture anauthor's distinctive style or identity. Afterbriefly discussing perceived and actualvocabulary richness, I show that doubling andcombining texts affects some measures incomputationally predictable but conceptuallysurprising ways. I discuss some theoretical andempirical problems with some measures anddevelop simple methods to test how wellvocabulary richness distinguishes texts bydifferent authors. These methods show thatvocabulary richness is ineffective for largegroups of texts because of the extremevariability within and among them. I concludethat vocabulary richness is of marginal valuein stylistic and authorship studies because thebasic assumption that it constitutes awordprint for authors is false. 相似文献
3.
Stress Heterogeneity Effect on the Strength of Silicon Nitride 总被引:1,自引:0,他引:1
François Hild Elisabeth Amer Didier Marquis 《Journal of the American Ceramic Society》1992,75(3):700-702
The experiments reported in this paper demonstrate the causes of the failure of monolithic ceramics. The specimens are made of silicon nitride and tested at room temperature. The stress field within the specimen is different for each of four series of tests that have been conducted. Fractographic observations have also been made to identify the causes of the failures. A size effect analysis is performed. 相似文献
4.
Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
5.
6.
An assessment of hydrocarbon and metal/metalloids (arsenic, cadmium, copper, lead, mercury, selenium, zinc) contamination in sediments from Lake Mulwala, Australia, was undertaken. The objectives of the study were: (i) to determine the extent of contamination in the lake sediments, compared to Australian and international sediment quality guidelines, and (ii) to attempt to identify the contaminant sources to the lake. With the exception of a few samples containing elevated levels of arsenic and/or mercury, the levels of all contaminants in the sediment samples taken from the lake were below the ‘lower trigger’ of the Australian Sediment Quality Guidelines that would warrant further investigation. High molecular weight hydrocarbons (up to 700 mg kg−1) were found in most sediment samples. Non‐metric statistical analysis indicated that the contaminant distribution was different in different parts of the lake, with the lowest concentrations generally found at the influent to the lake. No definitive source(s) of contamination could be identified for either metalloids or hydrocarbons. 相似文献
7.
A stochastic model is proposed for a basic mechanism in the formation of uncertainties in physical quantity measurements.
__________
Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–17, January, 2006. 相似文献
8.
9.
Chunsheng Lu Robert Danzer Franz Dieter Fischer 《Journal of the American Ceramic Society》2002,85(6):1640-1642
The influence of threshold stress on the estimation of the Weibull statistics is discussed in terms of the Akaike information criterion. Numerical simulations show that, if sample data are limited in number and threshold stress is not too large, the two-parameter Weibull distribution is still a preferred choice. For example, the fit of strength data of glass and ceramics to the two- and three-parameter Weibull distributions is compared. 相似文献
10.
This paper addresses the problem of finding the parameters of the arrival law which most significantly influence expected occupation and loss of a finite capacity queue. The input process is supposed to be ergodic and wide sense stationary. We show that it is mostly possible to fit an MMPP(2) to the decisive parameters of observational data. Numerical examples illustrate the importance of the decisive parameters, called key parameters, and also show the accuracy of the proposed fitting procedure. Finally, in the appendix we present the solution of the finite capacity queueing problem with Special Semi Markov Process (SSMP) arrivals and a general service strategy. 相似文献