全文获取类型
收费全文 | 60303篇 |
免费 | 4387篇 |
国内免费 | 2483篇 |
专业分类
电工技术 | 2116篇 |
技术理论 | 2篇 |
综合类 | 3999篇 |
化学工业 | 9552篇 |
金属工艺 | 3205篇 |
机械仪表 | 2782篇 |
建筑科学 | 4981篇 |
矿业工程 | 1985篇 |
能源动力 | 1727篇 |
轻工业 | 15209篇 |
水利工程 | 964篇 |
石油天然气 | 1438篇 |
武器工业 | 767篇 |
无线电 | 2852篇 |
一般工业技术 | 10614篇 |
冶金工业 | 3050篇 |
原子能技术 | 479篇 |
自动化技术 | 1451篇 |
出版年
2024年 | 415篇 |
2023年 | 1019篇 |
2022年 | 1762篇 |
2021年 | 2305篇 |
2020年 | 2292篇 |
2019年 | 1934篇 |
2018年 | 1840篇 |
2017年 | 2165篇 |
2016年 | 2108篇 |
2015年 | 1962篇 |
2014年 | 3088篇 |
2013年 | 3347篇 |
2012年 | 3719篇 |
2011年 | 3963篇 |
2010年 | 3000篇 |
2009年 | 3301篇 |
2008年 | 2625篇 |
2007年 | 3982篇 |
2006年 | 3660篇 |
2005年 | 3173篇 |
2004年 | 2617篇 |
2003年 | 2398篇 |
2002年 | 1988篇 |
2001年 | 1564篇 |
2000年 | 1398篇 |
1999年 | 1122篇 |
1998年 | 841篇 |
1997年 | 688篇 |
1996年 | 599篇 |
1995年 | 486篇 |
1994年 | 438篇 |
1993年 | 340篇 |
1992年 | 247篇 |
1991年 | 181篇 |
1990年 | 139篇 |
1989年 | 131篇 |
1988年 | 78篇 |
1987年 | 49篇 |
1986年 | 37篇 |
1985年 | 37篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 14篇 |
1964年 | 4篇 |
1959年 | 7篇 |
1958年 | 4篇 |
1955年 | 8篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
European intercomparison on electron spin resonance identification of irradiated foodstuffs 总被引:1,自引:0,他引:1
J. RAFFI † M. H. STEVENSON M. KENT J. M. THIERY J.-J. BELLIARDO 《International Journal of Food Science & Technology》1992,27(2):111-124
The results of a co-trial organized by the Community Bureau of Reference on the use of Electron Spin Resonance spectroscopy for the identification of irradiated food in 21 laboratories are presented. The trial was qualitative on beef and trout bones, sardine scales, pistachio nut shells, dried grapes, and papaya, and quantitative on poultry bones. There was no difficulty in identifying irradiated meat bones, dried grapes, and papaya. In the case of fish bones there is a need for further kinetic study on different species. Identification of irradiation in pistachio nuts is more complicated and additional research is needed before further trials. All laboratories were able to distinguish between chicken bones irradiated at 1 to 3 kGy or 7 to 10 kGy although there was a partial overlap between the results. 相似文献
132.
用屏蔽暂堵技术封堵水平井裂缝性漏层 总被引:1,自引:1,他引:0
克拉玛依油田HW702水平井的大斜度段和水平段,将穿越纵向裂缝发育的二叠系佳木河组储层。为安全钻进和保护油层,用超细碳酸钙和磺化沥青复配后加入复合离子钻井液中成屏蔽暂堵的堵漏钻井液。室内用岩心试验,屏蔽暂堵后渗透率可降为0,暂堵深度小于3cm,可用酸化和射孔解堵。现场使用效果也很好,使HW702水平井顺利完钻,并获得工业油气流。 相似文献
133.
反应烧结法制备MgAlON的合成机理及烧结行为的研究 总被引:2,自引:1,他引:1
通过对以Al2 O3、MgO和AlN为起始原料 ,在氮气气氛中反应烧结合成MgAlON材料合成机理的研究发现 :在 12 0 0℃以前 ,MgO与Al2 O3反应生成镁铝尖晶石 ,此后 ,随着温度的升高 ,Al2O3不断向所形成的尖晶石中固溶 ;在 130 0℃以前 ,AlN基本上不参与反应 ,而在更高的温度下 ,AlN开始向尖晶石中固溶形成MgAlON ,约在 15 5 0℃时形成单一的MgAlON相。用热膨胀仪检测了试样的线变化率随温度和时间的变化 ,用最小二乘法回归分析了试样线变化率的实验数据 ,并根据烧结理论对MgAlON材料烧结初期的动力学进行了探讨。结果表明 ,MgAlON材料烧结初期的烧结机理以体积扩散为主 相似文献
134.
135.
WANG Jiqing 《声学技术》2004,23(Z3)
This paper gives an overview of the research at Institute of Acoustics, Tongji University, on functional absorbers and experience acquired in practical applications over the past three decades. Experiments and analysis of the absorption characteristics of three different geometrical forms of functional absorbers, i.e., panels, cubes and tubes, were conducted with different arrangements. The resulting esthetical effects are illustrated with pictures. Several non-fiber materials are used to compose functional absorbers with advantages both in acoustic properties and in architectural features. Cost effectiveness analysis is also given in order to provide design guidelines. 相似文献
136.
A new interaction integral formulation is developed for evaluating the elastic T-stress for mixed-mode crack problems with
arbitrarily oriented straight or curved cracks in orthotropic nonhomogeneous materials. The development includes both the
Lekhnitskii and Stroh formalisms. The former is physical and relatively simple, and the latter is mathematically elegant.
The gradation of orthotropic material properties is integrated into the element stiffness matrix using a “generalized isoparametric
formulation” and (special) graded elements. The specific types of material gradation considered include exponential and hyperbolic-tangent
functions, but micromechanics models can also be considered within the scope of the present formulation. This paper investigates
several fracture problems to validate the proposed method and also provides numerical solutions, which can be used as benchmark
results (e.g. investigation of fracture specimens). The accuracy of results is verified by comparison with analytical solutions. 相似文献
137.
Rafael Gallego Lucia Comino Alberto Ruiz‐Cabello 《International journal for numerical methods in engineering》2006,66(12):1913-1933
In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
138.
139.
140.
阐述了硅铁生产中焦碳生产输送系统的工作原理和工艺要求,介绍了PLC在原料输送系统中的应用,给出了PLC的I/O接线图及程序框图,提出了工业原料生产输送控制系统的设计特点。 相似文献