全文获取类型
收费全文 | 31655篇 |
免费 | 2755篇 |
国内免费 | 1476篇 |
专业分类
电工技术 | 1120篇 |
综合类 | 2787篇 |
化学工业 | 5463篇 |
金属工艺 | 2190篇 |
机械仪表 | 982篇 |
建筑科学 | 6099篇 |
矿业工程 | 1304篇 |
能源动力 | 1706篇 |
轻工业 | 582篇 |
水利工程 | 1051篇 |
石油天然气 | 2677篇 |
武器工业 | 154篇 |
无线电 | 3251篇 |
一般工业技术 | 3550篇 |
冶金工业 | 922篇 |
原子能技术 | 255篇 |
自动化技术 | 1793篇 |
出版年
2024年 | 157篇 |
2023年 | 467篇 |
2022年 | 764篇 |
2021年 | 933篇 |
2020年 | 921篇 |
2019年 | 795篇 |
2018年 | 788篇 |
2017年 | 1140篇 |
2016年 | 1063篇 |
2015年 | 1189篇 |
2014年 | 1846篇 |
2013年 | 1703篇 |
2012年 | 2176篇 |
2011年 | 2424篇 |
2010年 | 1765篇 |
2009年 | 1798篇 |
2008年 | 1681篇 |
2007年 | 2113篇 |
2006年 | 1979篇 |
2005年 | 1624篇 |
2004年 | 1386篇 |
2003年 | 1267篇 |
2002年 | 1062篇 |
2001年 | 930篇 |
2000年 | 790篇 |
1999年 | 619篇 |
1998年 | 479篇 |
1997年 | 427篇 |
1996年 | 333篇 |
1995年 | 275篇 |
1994年 | 224篇 |
1993年 | 201篇 |
1992年 | 158篇 |
1991年 | 105篇 |
1990年 | 93篇 |
1989年 | 62篇 |
1988年 | 43篇 |
1987年 | 28篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1979年 | 10篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
新修订的《屋面工程技术规范)(GB50345--2012)已由住建部于2012年5月批准发布,并于2012年10月1日起实施。新规范在原规范的基础上进行了较大的修改,包括屋面工程设计、施工按构造层划分章节,修改了屋面防水等级,取消了防水层合理使用年限和刚性防水屋面,增加了消防、节能的有关条文,补充了金属板屋面、玻璃采光顶等新内容。本文对新规范中若干重大修改理由作了较详细的阐述。 相似文献
932.
Oswaldo Burciaga-DiazJose Ivan Escalante-Garcia Alexander Gorokhovsky 《Cement and Concrete Composites》2012,34(1):18-24
A coarse mineral with 70% kaolinite and 30% quartz was calcined and chemically activated by alkaline solutions of Na2SiO3 and NaOH. The compressive strength evolution was investigated as a function of the curing temperature at 20 and 80 °C, and the molar ratios of SiO2/Al2O3 (2.64-4.04) and Na2O/Al2O3 (0.62-1.54). For curing at 20 °C, the best composition was SiO2/Al2O3 = 2.96 and NaO/Al2O3 = 0.62, reaching 85 MPa at 28 days. Curing at 80 °C had a positive effect on the strength development only in the first 3 days. X-ray diffraction of the geopolymeric formulations showed the formation of amorphous silicoaluminates of similar nature. The microstructure consisted of unreacted quartz and metakaolinite particles in a matrix of silicoaluminate polymer and condensed silica gel from the unreacted sodium silicate. 相似文献
933.
以Photoshop软件为基础,对服装设计中的图层混合模式"正片叠底"建模进行分析,证明其能够为服装设计提供便利,提高设计师效率,并更好地表达服装设计意图。 相似文献
934.
Tree pruning wastes from six woody species, namely Acacia salicina, Conocarpus erectus, Ficus altissima, Leucaena glauca, Pithecellobium dulce and Tamarix aphylla, were used to manufacture high-quality wood reinforced cement composites (WRCCs). Hydrations experiments were conducted to screen the compatibility of the selected tree pruning wastes with cement. Additionally, various particle pretreatments and chemical additives were applied to enhance the compatibility of wood with cement. The best treatment for each species was selected and used to manufacture the WRCCs. The panels were produced under specific manufacturing variables and the mechanical properties and dimensional stability of the panels were determined. The results indicated that both board density and wood/cement (W/C) ratio had significant effects on the properties of WRCCs. With few exceptions, a W/C ratio of 1/2 and either 1200 kg m−3 or 1300 kg m−3 produced the optimal strength properties. The tree pruning wastes are suitable for use as raw materials in the manufacturing of WRCCs after pre-treatment of the wood particles with either cold or hot water and with addition 3% of CaCl2, Al2(SO4)3 or MgCl2. Therefore, these wastes could be used as an alternative wood source for WRCCs. 相似文献
935.
Franz B. Spingler Adam Phillips Tobias Schuler Michael C. Tucker Adam Z. Weber 《International Journal of Hydrogen Energy》2017,42(19):13960-13969
Reducing mass-transport losses in polymer-electrolyte fuel cells (PEFCs) is essential to increase their power density and reduce overall stack cost. At the same time, cost also motivates the reduction in expensive precious-metal catalysts, which results in higher local transport losses in the catalyst layers. In this paper, we use a hydrogen-pump limiting-current setup to explore the gas-phase transport losses through PEFC catalyst layers and various gas-diffusion and microporous layers. It is shown that the effective diffusivity in the gas-diffusion layers is a strong function of liquid saturation. In addition, it is shown how the catalyst layer unexpectedly contributes significantly to the overall measured transport resistance. This is especially true for low catalyst loadings. It is also shown how the various losses can be separated into different mechanisms including diffusional processes and mass-dependent and independent ones, where the data suggests that a large part of the transport resistance in catalyst layers cannot be attributed to a gas-phase diffusional process. The technique is promising for deconvoluting transport losses in PEFCs. 相似文献
936.
Atomic Layer Deposition (ALD) is a process used to deposit nanometer scale films for use in semiconductor electronics. The reactor consists of a warm wall horizontal flow tube, a substrate mounted on a disk downstream from the inlet, and cyclic flow between a reactant gas, a purging gas and a gas that preps the surface of the substrate. The objective is to achieve a uniform coating on the substrate layer by layer in minimal time. It is possible to use in situ monitoring of the gas phase and deposition to modify layer formation. Process improvement is currently accomplished experimentally by monitoring the precursor delivery and the growth of the film and adjusting the parameters: flow rates, temperature, pressure, concentrations, etc. Accurate simulation and optimization can decrease processing time and cost and increase control during product development. In addition, increased accuracy of gas transport simulation can be used to analyze reaction and diffusion rates, reaction mechanisms and other physical properties. In this paper we introduce the first comprehensive numerical solution of the Dusty-Gas Model including the complete binary diffusion term. We derive a concentration dependent Damkohler number relevant to the purge step of the process. The simulation matched the experimental data at a specific Damkohler number and further variation of the parameter confirmed existing experimentally observed phenomena. 相似文献
937.
本文采用预测FRC板的复合材料模型,从表面层到夹芯层进行力学性能分析,并根据工程使用的关键力学性能—抗弯强度进行材性结构设计。 相似文献
938.
S. Younessi Sinaki M. H. Panjeshahi F. Moattar 《Petroleum Science and Technology》2019,37(20):2122-2127
There is a wide range of resources for CO2 emissions. The net amount of CO2 emissions in the cement industry due to the consumption of fossil fuels and the chemical processes of cement production under heating raw materials is reported to be in the range of 15–25%; this industry, among all the industries and after the power plants and refineries, is the largest CO2 gas producer throughout the world. Using CO2 capture and storage (CCS), it can reduce greenhouse gas emissions in a short time. In this study, the technical feasibility study of recycling CO2 in Abyek Cement Company, with a cement production capacity of about 12,500 tons per day in two production lines, has been studied as one of the largest cement industries throughout the world. Fuel oil (Mazut) is used as the primary fuel for furnaces in this industry. Affected by combustion, the emissions emitted from the five-stage preheater contain 5/24% vol% of CO2, 7.6% H2O, 4.8% vol% of O2, and 63.1% N2. 相似文献
939.
940.