全文获取类型
收费全文 | 4073篇 |
免费 | 90篇 |
国内免费 | 136篇 |
专业分类
电工技术 | 51篇 |
技术理论 | 1篇 |
综合类 | 311篇 |
化学工业 | 821篇 |
金属工艺 | 367篇 |
机械仪表 | 711篇 |
建筑科学 | 237篇 |
矿业工程 | 149篇 |
能源动力 | 199篇 |
轻工业 | 300篇 |
水利工程 | 26篇 |
石油天然气 | 261篇 |
武器工业 | 15篇 |
无线电 | 106篇 |
一般工业技术 | 231篇 |
冶金工业 | 109篇 |
原子能技术 | 33篇 |
自动化技术 | 371篇 |
出版年
2024年 | 7篇 |
2023年 | 37篇 |
2022年 | 68篇 |
2021年 | 87篇 |
2020年 | 88篇 |
2019年 | 68篇 |
2018年 | 75篇 |
2017年 | 56篇 |
2016年 | 69篇 |
2015年 | 91篇 |
2014年 | 162篇 |
2013年 | 221篇 |
2012年 | 176篇 |
2011年 | 271篇 |
2010年 | 188篇 |
2009年 | 216篇 |
2008年 | 218篇 |
2007年 | 246篇 |
2006年 | 249篇 |
2005年 | 206篇 |
2004年 | 187篇 |
2003年 | 183篇 |
2002年 | 180篇 |
2001年 | 145篇 |
2000年 | 126篇 |
1999年 | 124篇 |
1998年 | 109篇 |
1997年 | 83篇 |
1996年 | 106篇 |
1995年 | 64篇 |
1994年 | 47篇 |
1993年 | 25篇 |
1992年 | 27篇 |
1991年 | 17篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有4299条查询结果,搜索用时 15 毫秒
101.
磁碟机病毒及其变种是近几年来病毒技术含量最高、破坏性最强的病毒,已感染数十万台计算机,造成的损失远远超过"熊猫烧香"。为了能有效地防御和查杀该病毒,该文特地对磁碟机病毒进行了深入的研究,分析了磁碟机的破坏机制,指出了磁碟机的种种危害,提出了防治磁碟机的几种技术方法,这对当前防御和清除磁碟机病毒具有一定的现实意义。 相似文献
102.
本文利用微观调查数据对我国国有部门与非国有部门工资决定机制的差异进行了实证研究。研究发现,在市场化改革过程中,不论是机关事业单位还是国有企业,其人力资本的收益率不断提高,这表明人力资本的报酬机制在国有部门的工资决定中得到了强化。但是与非国有部门工资决定模式相比较,国有部门的工资决定依然带有较强的制度化特征。进一步对工资差异进行的布兰德-瓦哈卡(Blinder-Oaxaca)分解表明,国有部门与非国有部门之间长期存在一定程度的工资溢价。溢价的存在意味着工资对劳动生产率(或者说人力资本水平)的偏离,同时也意味着同质劳动在两个部门得到不同的报酬,即"同工不同酬"。这种现象的存在必然会降低劳动力市场的效率,同时也会带来资源的浪费。 相似文献
103.
The prototype of a CO2 sensor made of CuO–BaTiO3, which has capacitance sensitive effect, is designed based on the pn heterojunctions of CuO and BaTiO3 semiconductors. The preparation of BaTiO3 semiconductor powders is pointed out, using the coprecipitation and semiconducting techniques. The characteristic quantities relating to the capacitance sensitive effect of the sensor are studied systematically with the aid of a gas tester. A reasonable mechanism of the sensor is proposed. 相似文献
104.
依据马克思主义的生产力理论和邓小平同志关于“科学技术是第一生产力”的论述,指出了经济系统的机理及其动力学性质。并在此基础上提出了经济系统生产力和生产力做功的模型及生产力产出效率模型,且与此同时在经济理论上得出: (1)生产力要素所具有的生产力大小等于它在实际产出上的生产力与克服生产关系反作用的生产力之和; (2)投入生产系统的全部生产力做功等于其实际产出做功与克服生产关系反作用做的无用功之和; (3)生产力效率,以及相对生产力效率的概念。作者认为,这些结果对正确认识和分析我国经济发展中存在和出现的一些重大问题可能具有一定的指导意义。 相似文献
105.
胶粘耐磨涂层的研制及其磨损机理分析 总被引:1,自引:0,他引:1
本文介绍了JNT90系列涂层的研制过程及计算机辅助涂层配方优化方法,分析了影响胶粘胶耐磨涂层耐磨性的主要因素,并通过扫描电镜对粘涂层的结构形貌,磨损机理进行了研究,提出了提高涂层性能折途径和见解。 相似文献
106.
Short rotation willow coppice (SRC) and a synthetic biomass, a mixture of the basic biomass components (cellulose, hemicellulose and lignin), have been investigated for the influence of potassium on their pyrolysis behaviours. The willow sample was pre-treated to remove salts and metals by hydrochloric acid, and this demineralised sample was impregnated with potassium. The same type of pre-treatment was applied to components of the synthetic biomass. Characterisation was performed using thermogravimetric analysis with measurement of products by means of Fourier transform infrared spectroscopy (TGA-FTIR) and pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). A comparison of product distributions and kinetics are reported. While the general features of decomposition of SRC are described well by an additive behaviour of the individual components, there are some differences in the magnitude of the influence of potassium, and on the products produced. For both SRC and the synthetic biomass, TGA traces indicate catalytic promotion of both of the two-stages of biomass decomposition, and potassium can lower the average apparent first-order activation energy for pyrolysis by up to 50 kJ/mol. For both SRC and synthetic biomass the yields and distribution of pyrolysis products have been influenced by the presence of the catalyst. Potassium catalysed pyrolysis increases the char yields markedly and this is more pronounced for synthetic biomass than SRC. Gas evolution profiles during pyrolysis show the same general features for both SRC and synthetic biomass. Relative methane yields increase during the char formation stage of pyrolysis of the potassium doped samples. The evolution profiles of acetic acid and formaldehyde change, and these products are seen in lower relative amounts for both the demineralised samples. A greater variation in pyrolysis products is observed from the treated SRC samples compared to the different synthetic biomass samples. Furthermore, substituted phenols from lignin pyrolysis are more dominant in the pyrolysis profiles of the synthetic biomass than of the SRC, implying that the extracted lignins used in the synthetic biomass yield a greater fraction of monomeric type species than the lignocellulosic cell wall material of SRC. For both types of samples, PY-GS-MS analyses show that potassium has a significant influence on cellulose decomposition markers, not just on the formation of levoglucosan, but also other species from the non-catalysed mechanism, such as 3,4-dihydroxy-3-cyclobutene-1,2-dione. 相似文献
107.
108.
To solve the problem of water seepage of vertical feeding borehole for solid materials, we established the fluid-solid coupling dynamic model of groundwater flowing in rock mass adjacent to the vertical feeding borehole. Combining with the engineering geological conditions, we built a numeral model to study the influence rule of the aquifer hydraulic pressure and seepage location of feeding borehole on the amount of seepage with finite element numerical method. The results show that the nonlinear relationship is presented among the amount of seepage, the seepage location and aquifer hydraulic pressure. The higher the aquifer hydraulic pressure is, the closer the distance between seepage location and aquifer is, and the faster the harmful levels of aquifer will grow. In practice, we calculated the allowable seepage of feeding borehole by the optimum moisture content and natural moisture content of backfilling materials, and then determined the protection zone of feeding borehole, so the moisture content of backfilling materials can be controlled within the scope of optimum moisture content. 相似文献
109.
"校村结对"是高校参与新农村建设的重要组织形式,能有效促进"生产发展、生活宽裕、乡风文明、村容整洁、管理民主"目标的实现。有关参与各方应创新"政府主导,农民主体,高校参与"三位一体新机制,拓展"校村结对"组织形式,健全考核激励机制,建立长效机制,构建内部组织体系,促进"校村结对"机制的不断完善和发展。 相似文献
110.
Flotation tests,contact angle measurements,infrared spectrum analyses,X-ray analyses and computer simulation were carried out in order to study the activation mechanism of lime-depressed pyrite with ox... 相似文献