全文获取类型
收费全文 | 38183篇 |
免费 | 4048篇 |
国内免费 | 2158篇 |
专业分类
电工技术 | 1692篇 |
技术理论 | 2篇 |
综合类 | 2882篇 |
化学工业 | 7883篇 |
金属工艺 | 2151篇 |
机械仪表 | 1121篇 |
建筑科学 | 3688篇 |
矿业工程 | 1935篇 |
能源动力 | 3447篇 |
轻工业 | 814篇 |
水利工程 | 5453篇 |
石油天然气 | 3049篇 |
武器工业 | 173篇 |
无线电 | 3237篇 |
一般工业技术 | 3305篇 |
冶金工业 | 1166篇 |
原子能技术 | 322篇 |
自动化技术 | 2069篇 |
出版年
2024年 | 154篇 |
2023年 | 562篇 |
2022年 | 874篇 |
2021年 | 1096篇 |
2020年 | 1155篇 |
2019年 | 1096篇 |
2018年 | 971篇 |
2017年 | 1269篇 |
2016年 | 1376篇 |
2015年 | 1356篇 |
2014年 | 2138篇 |
2013年 | 2384篇 |
2012年 | 2668篇 |
2011年 | 2878篇 |
2010年 | 2152篇 |
2009年 | 2100篇 |
2008年 | 2126篇 |
2007年 | 2442篇 |
2006年 | 2380篇 |
2005年 | 1967篇 |
2004年 | 1728篇 |
2003年 | 1548篇 |
2002年 | 1370篇 |
2001年 | 1220篇 |
2000年 | 976篇 |
1999年 | 838篇 |
1998年 | 657篇 |
1997年 | 562篇 |
1996年 | 479篇 |
1995年 | 402篇 |
1994年 | 291篇 |
1993年 | 257篇 |
1992年 | 235篇 |
1991年 | 153篇 |
1990年 | 121篇 |
1989年 | 106篇 |
1988年 | 76篇 |
1987年 | 82篇 |
1986年 | 31篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 8篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1959年 | 4篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
A mathematical model for the drying rate of granular particles in a multistage inclined fluidized bed(IFB) is presented from the standpoint of simultaneous heat and mass transfer, with taking the effect of mechanical vibration added vertically into consideration.
Steady-state distributions for the temperatures and concentrations of the particles and the heating gas, and for the moisture content of the particles are numerically calculated based on the present model. The calculated results show fairly good agreement with the experimental data, which were obtained from the drying experiments of brick particles in a three-stage IFB using comparatively low temperature air(40-60°C) as the heating gas.
It has been found within the range of the experimental conditions employed that, the mechanical vibration added vertically enhances the over-all drying rate of the particles and its effect can be considered equivalent to an increase in the air velocity. 相似文献
Steady-state distributions for the temperatures and concentrations of the particles and the heating gas, and for the moisture content of the particles are numerically calculated based on the present model. The calculated results show fairly good agreement with the experimental data, which were obtained from the drying experiments of brick particles in a three-stage IFB using comparatively low temperature air(40-60°C) as the heating gas.
It has been found within the range of the experimental conditions employed that, the mechanical vibration added vertically enhances the over-all drying rate of the particles and its effect can be considered equivalent to an increase in the air velocity. 相似文献
163.
164.
讨论了固定床反应器阻力降快速升高的原因,介绍了用轴径向技术解决这一问题的原理及优点,及其在铁铬系变换催化剂和钴钼系耐硫变换催化剂反应器中的实际应用。 相似文献
165.
在天然河道中,河势演变虽具有一定的随机性,但仍有一定的规律可循,在一个河段内,一般可归纳出2-3条基本流路,为控制河势变化,需要选择出一条基本流路进行河道整治,当连续发生枯水期或洪水期时,部分河段的河势可能出现大的变化,为防止不利河势向下游传播,可修建较长的龙头弯道工程,利用龙头弯道工程分段调整,控导河势,保持河势稳定。 相似文献
166.
Critical to restoring the nature conservation value of many river corridors is an understanding of how alluvial landscapes will respond to cessation of river management and land use practices that have previously degraded the environment. This paper analyses changes in valley floor landforms and vegetation patch dynamics, in relation to fluvial disturbance, over a period of almost 100 years following flood embankment abandonment on a wandering gravel‐bed river, namely the River Tummel, Scotland. Such rivers were once typical of many draining upland areas of northern maritime Europe. Prior to abandonment the valley floor landscape was agriculturally dominated and the river for the most part was single thread confined between flood embankments. The pattern of landform change and vegetation patch development over time following a decision in 1903 not to maintain embankments was tracked by geomorphic and land cover mapping utilizing successive sets of aerial photography for the period 1946 to 1994. A historical context for these changes was also feasible because the channel planform in 1900 and earlier channel planform changes dating back to 1753 were known due to the availability of old maps and earlier geomorphic studies. The land cover mapping was validated by comparison of results produced from the interpretation work on the 1994 aerial photographs with the field‐based UK National Vegetation Classification protocol. The findings of the study illustrate that bordering the River Tummel fluvial landforms and vegetation patch mosaics, presumably resembling those that occurred before valley floor land use intensification, evolved in less than 50 years after flood embankment abandonment with a resultant increase in habitat diversity. The change relates primarily to flood‐induced channel planform change and moderate levels of fluvial disturbance. The general significance of this change to plant species diversity on the valley floor of the River Tummel and elsewhere is discussed as is possible implications of the upstream impoundment and scenarios for climatically induced changes in flood frequency and magnitude. The overall outcome is the strong possibility that simple changes in river management and land use practices could result in re‐establishment of the nature conservation value of similar river corridors in Europe over the medium term without active restoration efforts. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
167.
长江重要堤防安全监测技术的应用与发展 总被引:1,自引:0,他引:1
长江重要堤防安全监测工程中,对主要穿堤建筑物、重要堤段都布置了安全监测设施.两年多来的监测过程中,获得了大量的监测资料和信息,为评价防渗墙的渗控效果及穿堤建筑物的运行状况提供了科学依据.防渗墙是堤防加固和防渗处理的主要工程措施之一,通过监测资料分析,防渗墙的实施有效地改善了堤身、堤基的渗流状态,不同结构形式的防渗墙所起的截渗效果是不一样的.穿堤建筑物内部监测由渗压计、测缝计、位错计和界面土压力计组成,为穿堤建筑物安全运行状况和施工质量评价提供了科学的依据.堤防安全监测新技术的开发与应用研究拓展了传统的安全监测领域,先进的安全监测技术在堤防工程建设中将得到广泛应用. 相似文献
168.
随着工农业发展和人口的增长,南流江流域水资源供需矛盾日益突出,水资源的可持续利用日益显得重要,针对流域水资源特点,提出加强水资源统一管理,实施跨流域调水,加强水资源保护等对策。 相似文献
169.
浅析中央空调系统替代制冷剂的选择 总被引:1,自引:0,他引:1
田国庆 《制冷空调与电力机械》2002,23(2):25-27
根据大气臭氧层耗损和温室气体对全球气候变化的影响,分析了中央空调系统几种替代制冷剂的特性,探讨了在实际使用中如何进行替代制冷剂的选择。 相似文献
170.
分子筛吸附柱和热金属镁床是手套箱气氛中氚化水 (HTO)搜集和分解处理的一种有效手段。测试了分子筛柱对气氛中水的吸附性能和热金属镁床对HTO的分解性能。结果表明 :分子筛柱对气氛中水的吸附效率 >99 99% ,在空气中水含量为 3 4× 1 0 - 3~ 4 2× 1 0 - 3条件下 ,未发现吸附柱水的贯穿现象 ;热金属镁床对HTO的分解率 >99 9% ,当金属镁的消耗量大于 80 %时 ,未见分解率明显降低。 相似文献