全文获取类型
收费全文 | 575570篇 |
免费 | 26679篇 |
国内免费 | 8716篇 |
专业分类
电工技术 | 21483篇 |
技术理论 | 37篇 |
综合类 | 17825篇 |
化学工业 | 91339篇 |
金属工艺 | 29551篇 |
机械仪表 | 27324篇 |
建筑科学 | 29938篇 |
矿业工程 | 10196篇 |
能源动力 | 15682篇 |
轻工业 | 43427篇 |
水利工程 | 7150篇 |
石油天然气 | 22888篇 |
武器工业 | 2239篇 |
无线电 | 67410篇 |
一般工业技术 | 88139篇 |
冶金工业 | 71020篇 |
原子能技术 | 7666篇 |
自动化技术 | 57651篇 |
出版年
2024年 | 6618篇 |
2023年 | 6253篇 |
2022年 | 9189篇 |
2021年 | 13878篇 |
2020年 | 11267篇 |
2019年 | 10200篇 |
2018年 | 11173篇 |
2017年 | 12155篇 |
2016年 | 11572篇 |
2015年 | 13722篇 |
2014年 | 17630篇 |
2013年 | 28682篇 |
2012年 | 23866篇 |
2011年 | 28126篇 |
2010年 | 23781篇 |
2009年 | 23814篇 |
2008年 | 23834篇 |
2007年 | 23705篇 |
2006年 | 23767篇 |
2005年 | 21348篇 |
2004年 | 15943篇 |
2003年 | 14797篇 |
2002年 | 14184篇 |
2001年 | 13531篇 |
2000年 | 13473篇 |
1999年 | 15562篇 |
1998年 | 24943篇 |
1997年 | 18587篇 |
1996年 | 15441篇 |
1995年 | 11907篇 |
1994年 | 10209篇 |
1993年 | 8980篇 |
1992年 | 6661篇 |
1991年 | 6053篇 |
1990年 | 5192篇 |
1989年 | 4852篇 |
1988年 | 4517篇 |
1987年 | 3795篇 |
1986年 | 3564篇 |
1985年 | 4016篇 |
1984年 | 3499篇 |
1983年 | 3141篇 |
1982年 | 2961篇 |
1981年 | 2934篇 |
1980年 | 2825篇 |
1979年 | 2616篇 |
1978年 | 2512篇 |
1977年 | 3193篇 |
1976年 | 4744篇 |
1975年 | 2198篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
北京远南大厦设计及其成败得失 总被引:2,自引:0,他引:2
介绍了北京南大厦供暖,空调通风,机械排风以及防排烟系统的设计概况,总结了设计中的成功经验,并结合运行情况,提出了一些在设计,生产,施工安装中应注意的问题。 相似文献
92.
Bosi Zhang Jiaqing Zhang Xiaomin Wang Shouxiang Lu Changhai Li Ruiyu Chen 《Fire Technology》2016,52(2):547-562
The effects of air inlet configuration on pool fire behavior in a mechanically ventilated cabin were investigated. The closed cabin used was a model of a certain machinery cabin on a naval ship. Two air inlet configurations of one vent and two vents were taken into account together with five different elevations of air inlet. In one-vent cases, mass loss rate and gas temperature were lower and oxygen concentrations were higher than those of two-vent cases. With the increase of air inlet elevation, a sudden drop in average mass loss rate and peak temperature were found in the two-vent cases at the air inlet elevation of 1.56 m. In one-vent cases, a similar drop in average mass loss rate was found at the air inlet elevation of 0.88 m, while the peak temperature was almost unaffected by inlet elevation. According to temperature profiles and the characteristic parameter of the smoke layer stability, the formation of the smoke layer was destroyed by increasing the air inlet elevation or reducing the air inlets, and furthermore a more uniform distribution could be found. For the current cabin, the one-vent case with a lower air inlet elevation was recommended for smoke control, and the inlet should be set away from the essential equipment and the entrances of the cabin. 相似文献
93.
Including in total 135 participants in the ages 19–69 years (recruited from the general public), an unannounced full-scale field evacuation experiment was performed in the Stockholm underground metro system on the night between October 17 and 18, 2014. The purpose was to collect data on the flow rate of people in train exits during the evacuation of a train in a tunnel and on the walking speed of people when moving long distances on an uneven surface in a tunnel, and to study exit choice and behaviour during an evacuation. Consequently, the experiment involved the evacuation of a rail car (a Bombardier C20 train) in a tunnel as well as the subsequent evacuation of the tunnel itself; the latter meant that the participants either could evacuate to the closest station (~400 m) or to an available emergency exit (~200 m). Among other things, the experiment demonstrated that the averaged flow rates of people in the train exits varied between 0.19 p/s and 0.22 p/s (0.14–0.16 p/m s when considering the train exit width of 1.4 m) and that the averaged walking speeds in the tunnel varied between 1.1 m/s and 1.2 m/s (no smoke present). Furthermore, all 135 participants found and used the available emergency exit, which had been equipped with a technical system consisting of a loudspeaker that broadcasted a combined alarm signal and a pre-recorded voice message. 相似文献
94.
95.
To further clarify the features of wedding dresses in new, style weddings in cities and towns of the Wu culture region, the author sorted out and made a statistical analysis of modern journals and periodicals as well as conducted a comparison in combination with diaries of celebrities and novels in modern times to collect 368 wedding photos in total in the Wu culture region. The analysis results indicate that wedding dresses in the Wu culture region were mainly of modified styles from 1859 to 1949, the development of wedding dresses went through the stages of unitary styles, mixed styles and diversified styles, in each of which there were also representative regular ways of matching. In general, wedding dresses were in simple, elegant and delicate styles, and the silhouettes kept up with popular western styles, showing a high level of acceptance of foreign cultures. The colors of wedding dresses tended to combinations of light colors, while traditional colors were gradually reduced. Besides, patterns of flowers and plants with thin stems and leaves were mainly used to decorate wedding dresses, showing the distribution features of scattering and covering. © 2018 China Silk Association. All rights reserved. 相似文献
96.
结合山西中部引黄工程的水文地质条件,分析了小断面隧洞快速掘进的施工难点及关键因素,并从施工部署、加宽段距离、工序衔接等方面,阐述了具体的施工方法,总结了施工安全、质量保障措施,实现了小断面隧洞的快速施工。 相似文献
97.
以某地铁线土压平衡盾构区间的渣土出运设计为例,介绍了土压平衡盾构的渣土运输系统,从渣土车选择、电瓶车运输能力选择等方面,阐述了电瓶车编组的方式,通过对其运输系统工效的分析,指出该工程采用的渣土运输设计方案,提高了盾构掘进速度,缩短了施工工期。 相似文献
98.
99.
农村及偏远地区饮用水除氟研究 总被引:9,自引:0,他引:9
研究了农村及偏远地区地下饮用水的除氟方法及其工艺流程、发展中的除氟新方法及新材料;分析了现有饮用水除氟设施存在的问题及其原因;提出了适合于农村及偏远郊区的除氟方法及其设施的发展方向. 相似文献
100.
水文地质参数的计算工作一直是工程地质和水文地质界工程师们所关注的重点问题之一,传统的计算方法比较繁琐、费时,国内外目前也没有比较全面的水文地质求参软件,因此,本文利用Visual Basic语言研究开发了一款基于现场试验的水文地质参数计算的新型软件SHP,通过数据库调用Excel文件录入数据,利用最小二乘法原理拟合直线。实现了手动配线和自动配线两种方法求参。通过南京市玄武湖隧道工程实例的校验,结果表明,该软件实用性强、计算精度较高、人机交互简单,满足工程需要。 相似文献