全文获取类型
收费全文 | 3592篇 |
免费 | 105篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 46篇 |
综合类 | 5篇 |
化学工业 | 508篇 |
金属工艺 | 78篇 |
机械仪表 | 71篇 |
建筑科学 | 145篇 |
矿业工程 | 13篇 |
能源动力 | 143篇 |
轻工业 | 428篇 |
水利工程 | 25篇 |
石油天然气 | 21篇 |
无线电 | 302篇 |
一般工业技术 | 476篇 |
冶金工业 | 870篇 |
原子能技术 | 32篇 |
自动化技术 | 547篇 |
出版年
2023年 | 18篇 |
2022年 | 34篇 |
2021年 | 51篇 |
2020年 | 32篇 |
2019年 | 36篇 |
2018年 | 57篇 |
2017年 | 48篇 |
2016年 | 59篇 |
2015年 | 60篇 |
2014年 | 100篇 |
2013年 | 180篇 |
2012年 | 146篇 |
2011年 | 153篇 |
2010年 | 137篇 |
2009年 | 123篇 |
2008年 | 139篇 |
2007年 | 144篇 |
2006年 | 137篇 |
2005年 | 93篇 |
2004年 | 78篇 |
2003年 | 104篇 |
2002年 | 83篇 |
2001年 | 73篇 |
2000年 | 71篇 |
1999年 | 73篇 |
1998年 | 272篇 |
1997年 | 180篇 |
1996年 | 117篇 |
1995年 | 77篇 |
1994年 | 89篇 |
1993年 | 88篇 |
1992年 | 48篇 |
1991年 | 42篇 |
1990年 | 36篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 36篇 |
1986年 | 25篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 31篇 |
1982年 | 19篇 |
1981年 | 24篇 |
1980年 | 29篇 |
1978年 | 18篇 |
1977年 | 31篇 |
1976年 | 47篇 |
1974年 | 15篇 |
1973年 | 19篇 |
1972年 | 14篇 |
排序方式: 共有3710条查询结果,搜索用时 15 毫秒
1.
Brian Lawn David Marshall Rishi Raj Greg Hirth Trevor Page Julie Yeomans 《Journal of the American Ceramic Society》2021,104(1):23-26
Crystalline quartz has long been identified as among the weakest of abundant crustal minerals. This weakness is particularly evident around the α–β phase inversion at 573°C, in which Si–O bonds undergo a displacive structural transformation from trigonal to hexagonal symmetry. Here we present data using indentation testing methodologies that highlight the precipitous extent of the transformational weakening. Although the indentations are localized over relatively small specimen contact areas, the data quantify the essential deformation and fracture properties of quartz in a predominantly (but not exclusively) compressive stress field, at temperatures and pressures pertinent to conditions in the earth's crust. 相似文献
2.
Karolina Storesund Francine Amon Anne Steen‐Hansen Shayesteh Haghighatpanah Ida Larsson 《火与材料》2021,45(1):181-190
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production. 相似文献
3.
Manjin Kim Qinfen Gu Tanveer Hussain Yahia Ali Trevor B. Abbott Kazuhiro Nogita 《International Journal of Hydrogen Energy》2021,46(53):27096-27106
With superior properties of Mg such as high hydrogen storage capacity (7.6 wt% H/MgH2), low price, and low density, Mg has been widely studied as a promising candidate for solid-state hydrogen storage systems. However, a harsh activation procedure, slow hydrogenation/dehydrogenation process, and a high temperature for dehydrogenation prevent the use of Mg-based metal hydrides for practical applications. For these reasons, Mg-based alloys for hydrogen storage systems are generally alloyed with other elements to improve hydrogen sorption properties. In this article, we have added Na to cast Mg–La alloys and achieved a significant improvement in hydrogen absorption kinetics during the first activation cycle. The role of Na in Mg–La has been discussed based on the findings from microstructural observations, crystallography, and first principles calculations based on density functional theory. From our results in this study, we have found that the Na doped surface of Mg–La alloy systems have a lower adsorption energy for H2 compared to Na-free surfaces which facilitates adsorption and dissociation of hydrogen molecules leading to improvement of absorption kinetic. The effect of Na on the microstructure of these alloys, such as eutectic refinement and a density of twins is not highly correlated with absorption kinetics. 相似文献
4.
5.
Pakteera Sripokar Yi Zhang Benjamin K. Simpson Egon Bech Hansen Suppasil Maneerat Sappasith Klomklao 《International Journal of Food Science & Technology》2021,56(12):6368-6375
Beardless barb is a common fish species used in fermentation of fish paste Ka-pi-plaa. Autolytic profile of beardless barb muscle showed the maximum autolysis was at 50 °C, at both acidic and alkaline pH values. With augmentation concentration of NaCl, autolytic activity slightly decreased. Endogenous proteinases isolated from fish muscle in crude extract forms were also characterised. The acidic proteinases had optimum activity at pH 3.0 and 50°C, and they showed higher proteolytic activity than the alkaline proteinases which were optimally active at pH 9.0 and 50 °C. Proteinases in peak at pH 3.0 were inhibited by pepstatin A, but those in peak at pH 9.0 were highly inhibited by PMSF, TLCK and soybean trypsin inhibitor, suggesting that both aspartic and serine proteinases were existed in beardless barb muscle. The proteinases were stable in pH range of 2.0-5.0 but unstable at the temperatures higher than 40 °C. NaCl suppressed the proteolytic activity, ATP activated the proteinase activity, while CaCl2, MgCl2 and CoCl2 exhibited no influence on the activity. The results implied that cathepsin D is the predominant proteinase responsible for autolysis in beardless barb. The findings were useful to improve the processing and qualities of Ka-pi-plaa product using beardless barb as raw material. 相似文献
6.
D Galasko T Saitoh Y Xia LJ Thal R Katzman LR Hill L Hansen 《Canadian Metallurgical Quarterly》1994,44(10):1950-1951
We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap. 相似文献
7.
Steven Y. Susswein Thomas C. Henderson Joseph L. Zachary Chuck Hansen Paul Hinker Gary C. Marsden 《International journal of parallel programming》1991,20(6):453-473
Filtering algorithms are well accepted as a means of speeding up the solution of the consistent labeling problem (CLP). Despite the fact that path consistency does a better job of filtering than arc consistency, AC is still the preferred technique because it has a much lower time complexity. We are implementing parallel path consistency algorithms on multiprocessors and comparing their performance to the best sequential and parallel arc consistency algorithms.(1,2) (See also work by Kerethoet al.
(3) and Kasif(4)) Preliminary work has shown linear performance increases for parallelized path consistency and also shown that in many cases performance is significantly better than the theoretical worst case. These two results lead us to believe that parallel path consistency may be a superior filtering technique. Finally, we have implemented path consistency as an outer product computation and have obtained good results (e.g., linear speedup on a 64K-node Connection Machine 2). 相似文献
8.
The application of computer control continue to grow. If lessons can be learnt from the incidents that have occurred, they may be prevented from happening again. This paper describes some incidents that have occurred in computer-controlled process plants. The errors are, of course, human errors, failures to foresee or allow for equipment failures or failures to foresee how operators will respond to the equipment. The computers provided new and easier opportunities for making old errors. 相似文献
9.
10.
重馏分油加氢脱氮反应动力学模型的研究 总被引:10,自引:1,他引:9
简要地介绍了一些典型的模型氮化物的HDN反应规律。根据胜利VGO在3722B催化剂上的大量HDN实验数据,提出了如下的HDN基本反应动力学方程:dCNdt=-k1+K*CNCNPH2为了扩大上式的应用范围,详细分析了各种因素(如原料油种类和馏程及H2S等)对HDN的影响,并开发了相应的经验关联式,从而得到了一个较完整的馏分油HDN反应动力学模型。验证实验表明,该模型是成功的。 相似文献