全文获取类型
收费全文 | 227928篇 |
免费 | 21052篇 |
国内免费 | 10167篇 |
专业分类
电工技术 | 14284篇 |
技术理论 | 31篇 |
综合类 | 23313篇 |
化学工业 | 27509篇 |
金属工艺 | 9557篇 |
机械仪表 | 11598篇 |
建筑科学 | 32318篇 |
矿业工程 | 14270篇 |
能源动力 | 8315篇 |
轻工业 | 16674篇 |
水利工程 | 10964篇 |
石油天然气 | 14672篇 |
武器工业 | 3254篇 |
无线电 | 14439篇 |
一般工业技术 | 16649篇 |
冶金工业 | 12034篇 |
原子能技术 | 1749篇 |
自动化技术 | 27517篇 |
出版年
2024年 | 1065篇 |
2023年 | 3065篇 |
2022年 | 5803篇 |
2021年 | 7642篇 |
2020年 | 7506篇 |
2019年 | 5539篇 |
2018年 | 5253篇 |
2017年 | 6455篇 |
2016年 | 8001篇 |
2015年 | 8631篇 |
2014年 | 15678篇 |
2013年 | 13771篇 |
2012年 | 16350篇 |
2011年 | 18154篇 |
2010年 | 13372篇 |
2009年 | 13591篇 |
2008年 | 12430篇 |
2007年 | 15038篇 |
2006年 | 13718篇 |
2005年 | 12024篇 |
2004年 | 10045篇 |
2003年 | 8717篇 |
2002年 | 7084篇 |
2001年 | 5850篇 |
2000年 | 5018篇 |
1999年 | 3950篇 |
1998年 | 2837篇 |
1997年 | 2487篇 |
1996年 | 2025篇 |
1995年 | 1677篇 |
1994年 | 1424篇 |
1993年 | 1004篇 |
1992年 | 827篇 |
1991年 | 571篇 |
1990年 | 501篇 |
1989年 | 458篇 |
1988年 | 250篇 |
1987年 | 195篇 |
1986年 | 174篇 |
1985年 | 193篇 |
1984年 | 137篇 |
1983年 | 116篇 |
1982年 | 64篇 |
1981年 | 86篇 |
1980年 | 82篇 |
1979年 | 41篇 |
1978年 | 23篇 |
1977年 | 25篇 |
1975年 | 20篇 |
1959年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Deep Integration of Innovation and Entrepreneurship (InE) Education in Chinese University Classrooms
Recently, InE has been regarded as a popular education strategy in Chinese universities. However, problems have been exposed in the adoption of InE, for example, in InE courses and competitions. The purpose of this paper is to provide a possible solution to the problems, which is to organize effective InE courses by integrating InE with Inter-Course-level Problem-Based Learning (ICPBL). A detailed case is demonstrated by an ICPBL elective course design with deep integration of InE in the teaching, learning, and assessments. This paper contributes to a new curriculum design for promoting InE education in practically for Chinese universities. 相似文献
62.
生姜的根状茎为使用部分,其中包含姜油酮、姜油醇、姜油酚、蛋白质、粗脂肪、糖,并且钙、铁的含量也较为丰富,是人们日常生活当中不可或缺的调味品,还能够加工成为姜片、糖姜片和盐姜片等诸多食品,其在医药方面的应用也较为广泛,备受人们的推崇与喜爱。我国在生姜栽培方面的历史较为悠久,技术也较为成熟,每年生姜出口贸易都能为我国带来非常可观的经济效益。 相似文献
63.
随着我国石油需求量不断增加,致密油藏的开发也愈发重要。如何高效开发致密油藏是一项重点难点,其中致密油藏注天然气提高采收率是一个极具潜力的研究方向。因此,本文着重介绍以天然气作为能量补充介质在国内外的研究现状和应用现状,并且从两相特征等方面总结了理论研究中的一些机理,对致密油藏注天然气提高采收率的发展前景进行了一定的展望。 相似文献
64.
针对传统隐伏型导水地质裂缝勘探方法存在勘测精度较差的问题,提出电磁精细探测法探析隐伏型导水地质裂缝。依照屏蔽系数、实测场强和理论场强数据绘制综合曲线图,通过该图获取隐伏型导水地质裂缝所处位置几何阴影范围,采用层析成像法得到网格化的工作面,获取隐伏型导水地质图像。通过图像直接观测隐伏型导水地质工作面裂缝所处位置,在此基础上,观测四个电磁场分量,采用正交电磁场分量计算介质视电阻率,依据计算视电阻率数值和视电阻率分布状态研究裂缝发育情况和裂缝富水程度。结果表明:采用该方法能较为精准地获取隐伏型导水地质裂缝位置。通过裂缝位置进一步检测出隐伏型导水地质裂缝最大发育高度为63.5 m。当视电阻数值不断增加时,隐伏型导水地质裂缝和裂缝富水性逐渐减小,与实际情况较为相符,说明该种方法探析效果较好。 相似文献
65.
Hassan Hajjaj Gerard Goma Jean M. François 《International Journal of Food Science & Technology》2015,50(8):1731-1736
In submerged cultures performed in chemically defined fermentation medium containing glucose and glutamate, the growth and production of water‐soluble red pigments and citrinin by the filamentous fungus Monascus ruber were studied under various carbon/nitrogen (C/N) ratios. The specific production of the red pigments was optimal at a glucose/glutamate ratio of about 10 and then steadily decreased at higher C/N ratio. In contrast, the production of the mycotoxin increased with increased C/N with an optimum in the range of 30–45. In a fed‐batch mode, it was also found that the production of pigments was not favoured in fed‐batch mode by feeding the medium with glucose while keeping the C/N ratio lower than 10. This low production likely resulted from concurrent high accumulation of L‐malic acid that was reported to inhibit this production. In contrast, this mode of cultivation was rather favourable for the production of the mycotoxin. 相似文献
66.
67.
心理测试的根本目的是为了让人们在测试过程中,产生某些特定行为,即个体对测试题目的反应,并根据这些行为反应来推论其相应的心理特性。在一定程度上帮助我们了解人类的心理活动,并从中得到帮助。因此,本文对基于学生群体心理测试系统的设计进行深入研究。 相似文献
68.
《International Journal of Hydrogen Energy》2021,46(64):32480-32489
Based on that hydrogen energy is widely used in fuel cells, we focus our interests on the design and research of new complexes that catalyze the reaction in both directions, such as hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs). A highly efficient catalyst for both hydrogen evolution and oxidation, based on a nickel(II) complex, [Ni-en-P2](ClO4)2, has been designed and provided by the reaction of Ni(ClO4)2 with N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P2) in our group. Its structure has been determined by X-ray diffraction. [Ni-en-P2](ClO4)2 can electro-catalyze hydrogen evolution both from acetic acid and a neutral buffer (pH 7.0) with a turnover frequency (TOF) of 204 and 1327 mol of hydrogen per mole of catalyst per hour (H2/mol catalyst/h) under an overpotential (OP) of 914.6 mV and 836.6 mV, respectively. [Ni-en-P2](ClO4)2 also can electro-catalyze hydrogen oxidation with a TOF of 111.7 s−1 under an OP of 330 mV. The results can be attributed to that [NiII-en-P2](ClO4)2 has three good reversible redox waves at 1.01 (NiIII/II), −0.79 (NiII/I) and −1.38 V (NiI/0) versus Fc+/0, respectively. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation. 相似文献
69.
Seyed Ali Maghami 《热应力杂志》2015,38(2):250-270
Thermal bending analysis of doubly curved laminated shell panels with general boundary conditions and laminations is presented. The equations of equilibrium are derived in the form of two coupled sets of ordinary differential equations based on a general shell theory and solved through the state-space approach in a repeated manner. It is depicted that the results of the present method are in great agreement with analytical solutions. Cylindrical shell panels with general boundary conditions and laminations, where no analytical solution is available, are solved. It is found that the present method exhibits a high convergence rate as well as presenting accurate results in all cases. 相似文献
70.
This study addresses the thermo‐diffusion and the diffusion‐thermo phenomena in a semi‐infinite absorbent channel whose walls are contracting/expanding, with heat source/sink effects. The governing partial differential equations with suitable boundary conditions are transformed to a system of dimensionless ordinary differential equations. An analytic solution of the problem has been found using a technique called homotopy analysis method (HAM). HAM gives consistently valid answers to the problem over an extensive variety of parameters and also provides better accuracy. To validate the analytical results, a comparison has been presented with a numerical solution calculated by using the parallel shooting method. The effects of dimensionless parameters, that is, deformation parameter, Reynolds number, Soret and Dufour numbers, and heat source/sink parameter on the expressions of velocity, temperature, and concentration profiles are analyzed graphically to understand the physics of the deformable channel. It has been noted that the velocity across the channel is higher for the expanding channel, as compared to that for the contracting channel. Also the Soret and Dufour number increases the temperature of the fluid, and decreases the concentration. The temperature profile has an increasing behavior in the case of heat source, and a decreasing behavior in the case of heat sink. 相似文献