全文获取类型
收费全文 | 12926篇 |
免费 | 330篇 |
国内免费 | 261篇 |
专业分类
电工技术 | 327篇 |
技术理论 | 1篇 |
综合类 | 519篇 |
化学工业 | 2233篇 |
金属工艺 | 152篇 |
机械仪表 | 323篇 |
建筑科学 | 1362篇 |
矿业工程 | 373篇 |
能源动力 | 3878篇 |
轻工业 | 406篇 |
水利工程 | 718篇 |
石油天然气 | 186篇 |
武器工业 | 26篇 |
无线电 | 235篇 |
一般工业技术 | 421篇 |
冶金工业 | 842篇 |
原子能技术 | 294篇 |
自动化技术 | 1221篇 |
出版年
2024年 | 15篇 |
2023年 | 149篇 |
2022年 | 271篇 |
2021年 | 388篇 |
2020年 | 395篇 |
2019年 | 319篇 |
2018年 | 268篇 |
2017年 | 327篇 |
2016年 | 368篇 |
2015年 | 328篇 |
2014年 | 666篇 |
2013年 | 698篇 |
2012年 | 699篇 |
2011年 | 1192篇 |
2010年 | 967篇 |
2009年 | 885篇 |
2008年 | 837篇 |
2007年 | 876篇 |
2006年 | 640篇 |
2005年 | 526篇 |
2004年 | 480篇 |
2003年 | 409篇 |
2002年 | 338篇 |
2001年 | 282篇 |
2000年 | 195篇 |
1999年 | 181篇 |
1998年 | 130篇 |
1997年 | 112篇 |
1996年 | 98篇 |
1995年 | 68篇 |
1994年 | 62篇 |
1993年 | 48篇 |
1992年 | 46篇 |
1991年 | 40篇 |
1990年 | 46篇 |
1989年 | 24篇 |
1988年 | 26篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1964年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
本文利用程序静态分析技术对Web程序中的用例识别进行了深入研究。对Web页面的用户行为进行了深入分析并建模,从行为模型中提取出描述整个系统中用户行为的事件流图,结合采用现有的从目的成功语句出发、以必经结点为基础的用例识别方法,从各个Web页面中提取的独立控制流图,形成全局控制流图,进行全局用例识别。与以前已有工作相比,本文考虑了Web程序的特点,尤其是前端程序如何实现用户行为,并在前端程序中进行精确的用例识别。本文采用目前使用较为广泛的JSP程序进行了实验,结果表明该方法能够有效识别JSP程序中的用例结构。 相似文献
83.
The process of grinding soybeans to a fine flour and extracting the flour with hexane was studied on a pilot plant scale.
The crude oil from the pilot plant study had 15 ppm phosphorus and was suitable for physical refining after a light acid pretreatment
and bleaching. The refined oil showed a Lovibond color of 1.4 yellow and 0.3 red. The pilot plant study also showed that grinding
of the soybeans and the separation of solid from miscella were the most difficult steps in solvent extraction with fine flour.
A laboratory study on separation of miscella from meal by aqueous ethanol reduced the hold-up volume, but it did not remove
all the miscella. A test with betacarotene showed that only the miscella outside the flour particles was displaced.
Aqueous ethanol solutions used as a second solvent extracted additional nontriglyceride materials (primarily phospholipids)
from the meal. Also, the free fatty acid content of the oil was increased with aqueous ethanol solution wash. The quality
of the extracted crude oil was lowered by using a second solvent, but it had the advantage of needing only one centrifugation
to separate miscella from meal. 相似文献
84.
Lin Gao 《Electrochimica acta》2004,49(8):1281-1287
Yields were determined for the CO2 produced upon the electrochemical oxidation of 1.0 M methanol in 0.1 M HClO4 at the following four fuel cell catalyst systems: Pt black, Pt at 10 wt.% metal loading on Vulcan XC-72R carbon (C/Pt, 10%), PtRu black at 50 at.% Pt, 50 at.% Ru (PtRu (50:50) black), and PtRu at 30 wt.% Pt, 15 wt.% Ru loading on Vulcan XC-72R carbon (C/PtRu, 30 wt.% Pt, 15 wt.% Ru). Samples were electrolyzed in a small volume (50 μl) arrangement for a period of 180 s keeping the reactant depletion in the cell below 1%. The dissolved CO2 produced was determined ex situ by infrared spectroscopy in a micro-volume transmission flow cell. For the PtRu materials, the efficiencies for CO2 formation were near 100% at reaction potentials in the range between 0.4 V (versus the reversible hydrogen electrode (RHE), VRHE ) and 0.9 VRHE. At the Pt catalysts, the yields of CO2 approached 80% between 0.8 and 1.1 VRHE and declined rapidly below 0.8 VRHE. 相似文献
86.
In this paper, the effect of wall conduction of an autothermal tubular methane microreformer is investigated numerically. It is found that the axial wall conduction can strongly influence the performance of the microreactor and should not be neglected without a careful a priori investigation of its impact. By increasing the wall thermal conductivity, the maximum wall surface temperature is decreased. Due to the complex exothermic–endothermic nature of the chemistry of reforming, the axial variation of the wall temperature is not monotonic. Methane conversion and hydrogen yield are strongly dependent on the wall inner surface temperature, hence the heat conduction through the channel wall. The equivalence ratio and the wall thickness also significantly affect the reforming effectiveness and must be carefully considered in reactor optimization. Furthermore, it is found that exothermic oxidation reaction mechanisms, especially partial oxidation, are responsible for syngas (hydrogen and carbon monoxide) production near the inlet. Farther downstream, in the oxygen deficient region, endothermic steam reforming is the main hydrogen producing mechanism. By increasing the thermal conductivity, steam reforming becomes stronger and partial oxidation becomes weaker. For all investigated inlet conditions, the highest hydrogen yield is obtained for no or very low conductive walls. 相似文献
87.
阎宝慧 《太原重型机械学院学报》2009,(5):387-391
介绍了液晶及液晶显示器,从环境温度、湿度对液晶显示器正常工作所造成的影响进行分析,提出了低温加热、高温散热针对性解决方法。 相似文献
88.
为了揭示药物在机体内的ADME过程,将脉冲微分方程理论应用于研究药物动力学若干问题中,通过对系统动力学行为的研究进而设计最佳用药方案,丰富了脉冲微分方程理论并对指导临床实践具有积极意义. 相似文献
89.
Lise T. Sagdahl Mari-Ann Einarsrud Tor Grande 《Journal of the European Ceramic Society》2006,26(16):3665-3673
The sintering properties of La1−xSrxFeO3−δ (x = 0.1, 0.25) mixed conductors have been investigated with particular emphasis on the effect of secondary phases due to cation non-stoichiometry (±5 mol% La excess and deficiency). Secondary phases, located at grain boundaries in cation non-stoichiometric materials, increased the sintering temperature compared to single-phase materials. Extensive swelling in final stage of sintering was observed in all materials, which resulted in micro-porous materials. The swelling was most pronounced in the phase pure and two-phase materials due to La-deficiency, while refractory secondary phases in La-excess materials inhibited both sintering, grain growth and swelling. In La-deficient materials, formation of molten secondary phases resulted in rapid swelling due to viscous flow. The present findings demonstrated the importance of controlling sintering temperature and time, as well as careful control of the cation stoichiometry of La1−xSrxFeO3−δ in order to achieve fully dense and homogenous La1−xSrxFeO3−δ ceramics. 相似文献
90.
为探究城镇化进程引起土地利用类型变化对山前平原区洪涝过程的影响,以梅溪流域下游平原区的洪濑镇为例,分析了2002—2018年梅溪流域上游山区和下游平原区的土地利用类型变化,并基于多情景数值模拟,研究了流域尺度内土地利用类型变化对山前平原区洪涝过程和地表淹没状况的影响。结果表明:随着梅溪流域耕地和林地面积减少、城镇建设用地增加,上游山区的径流系数和峰值流量均增大,下游山前平原区的淹没状况更加严重;上游山区的城镇建设用地增加使山区骤发洪水峰值流量增大、峰现时间提前,主要影响地表平均最大淹没水深和平均峰现时间;下游平原区的城镇建设用地增加使内涝发生的时间提前,主要影响地表平均淹没历时。 相似文献