全文获取类型
收费全文 | 2980篇 |
免费 | 279篇 |
国内免费 | 1091篇 |
专业分类
安全科学 | 293篇 |
废物处理 | 175篇 |
环保管理 | 252篇 |
综合类 | 1950篇 |
基础理论 | 466篇 |
污染及防治 | 817篇 |
评价与监测 | 184篇 |
社会与环境 | 117篇 |
灾害及防治 | 96篇 |
出版年
2024年 | 11篇 |
2023年 | 61篇 |
2022年 | 208篇 |
2021年 | 216篇 |
2020年 | 173篇 |
2019年 | 113篇 |
2018年 | 170篇 |
2017年 | 197篇 |
2016年 | 148篇 |
2015年 | 199篇 |
2014年 | 253篇 |
2013年 | 326篇 |
2012年 | 274篇 |
2011年 | 285篇 |
2010年 | 214篇 |
2009年 | 196篇 |
2008年 | 224篇 |
2007年 | 171篇 |
2006年 | 196篇 |
2005年 | 133篇 |
2004年 | 81篇 |
2003年 | 61篇 |
2002年 | 50篇 |
2001年 | 46篇 |
2000年 | 58篇 |
1999年 | 59篇 |
1998年 | 55篇 |
1997年 | 43篇 |
1996年 | 36篇 |
1995年 | 22篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有4350条查询结果,搜索用时 312 毫秒
191.
193.
ABSTRACT Refrigerant pressure drop and temperature change in pipes are normally ignored in the thermodynamic analysis of traditional vehicle air conditioning system, this will result in serious errors. In this Paper, pressure drop and temperature difference are simulated in different pipes of electric vehicle (EV) heat pump system to analysis the effects of pipes in the actual EV heat pump system. The results indicate that the greater the mass flow, the faster pressure drop increases, the temperature difference decreases. Pressure drop of saturated liquid refrigerant is smaller than that of saturated gas refrigerant at the same saturation pressure and mass flow rate. The higher the refrigerant pressure (no phase change), the slower pressure drop decreases, the faster the temperature difference decreases. Pressure drop decreases with the increment of bending angle of the pipe. For EV heat pump system, suitable valves and less branches are helpful for energy saving of the system. Shortening the pipe between compressor and condenser can reduce temperature change obviously. Pressure drop per unit length in the pipe between evaporator and compressor is large especially in heating mode because of lower refrigerant density. It even reaches to over 100 times of that in the pipe between condenser and throttle valve in heating mode and has negative effects on the performance of the system. If the evaporator is closer to the compressor and the number of branches is less, then pressure drop will decrease a lot, which will be advantageous for energy saving of the heat pump system. 相似文献
194.
Yapeng Song Hui Gong Jianbing Wang Fengmin Chang Kaijun Wang 《Frontiers of Environmental Science & Engineering》2020,14(4):64
195.
Xinjie Wang Yang Li Jian Zhao Hong Yao Siqi Chu Zimu Song Zongxian He Wen Zhang 《Frontiers of Environmental Science & Engineering》2020,14(4):56
196.
Kun Wan Wenfang Lin Shuai Zhu Shenghua Zhang Xin Yu 《Frontiers of Environmental Science & Engineering》2020,14(1):10
197.
Song Yao Wang Liancheng Lv Baoliang Chang Guozhang Jiao Weizhou Liu Youzhi 《Environmental science and pollution research international》2020,27(7):7015-7024
Environmental Science and Pollution Research - In this study, porous activated carbon balls supported by nanoscale zero-valent iron composites (Fe@PACB-700) were used for the first time for the... 相似文献
198.
199.
The moisture from skin sweat and atmospheric water affects the thermal protective performance provided by multilayer protective clothing. Four levels of moisture content were selected to evaluate the impact of moisture on thermal protection under dry (thermal radiation) and wet (thermal radiation and low-pressure steam) heat exposure. Also, the role of moisture and its relationship with exposure time were analyzed based on skin heat flux and Henriques integral value. The addition of moisture to a fabric system was found to result in differences in second-degree and third-degree skin burn times. When moisture is added to a fabric system, it both acts as a thermal conductor to present a negative effect and provides a positive effect owing to thermal storage of water and evaporative heat loss. The positive or negative effects of moisture are mainly dependent on the thermal exposure time, the moisture content and the presence of hot steam. 相似文献
200.
储罐配管在温差作用下产生热位移会导致管壁产生热应力,未采用柔性连接的配管由于热应力集中作用可能发生破漏。针对与石油化工储罐非柔性连接的配管的安全问题,应用ANSYS有限元分析软件模拟计算石化企业典型配管的热应力分布;根据不同类型配管的分析结果,提出了工程技术与管理方面的针对性安全措施。研究结果表明:温差效应对石化储罐配管热应力影响显著,随内外温差的增加,配管应力集中的区域增大,最大热应力值增大;补偿措施能够改善配管的柔性,降低配管应力;约束载荷限制配管热膨胀从而增大配管应力;三通管是多根配管接合的区域,这种复杂管道交汇处会形成明显应力集中。研究结果对于提高石油化工非柔性连接配管安全性有一定的指导意义。 相似文献