首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   283篇
  免费   41篇
  国内免费   6篇
安全科学   199篇
废物处理   2篇
环保管理   19篇
综合类   57篇
基础理论   31篇
污染及防治   2篇
评价与监测   4篇
社会与环境   5篇
灾害及防治   11篇
  2023年   3篇
  2022年   5篇
  2021年   15篇
  2020年   16篇
  2019年   9篇
  2018年   4篇
  2017年   5篇
  2016年   11篇
  2015年   8篇
  2014年   21篇
  2013年   46篇
  2012年   21篇
  2011年   26篇
  2010年   17篇
  2009年   18篇
  2008年   9篇
  2007年   13篇
  2006年   11篇
  2005年   9篇
  2004年   9篇
  2003年   13篇
  2002年   8篇
  2001年   5篇
  2000年   5篇
  1999年   8篇
  1998年   2篇
  1997年   4篇
  1996年   4篇
  1995年   2篇
  1994年   1篇
  1992年   2篇
排序方式: 共有330条查询结果,搜索用时 546 毫秒
141.
为明确不同极端低温环境与防护装备下,日间清醒和夜间睡眠状态下各部位皮肤温度变化特征,在-16 ℃~-30 ℃极端低温环境下,采用皮温测量系统对实验对象5个代表性部位(胸部、手臂、大腿、小腿和脚趾)皮肤温度进行测试。结果表明:日间测试胸部温度相对最高,大腿和小腿在实验中后期出现温度反转。夜间除脚趾外,各部位皮肤温度变化差异较小,大腿温度相对最高,小腿温度与其他部位分离。研究结果可为低温环境下防护服研发与保暖效果评价提供参考。  相似文献   
142.
The pultruded jute/phenolic composites were aged under various humidity, hydrothermal and weathering conditions. Aging-induced effect of these conditions on the jute profiles was studied in terms of their physico-mechanical properties. It is observed that dimensional change of the profiles was only upto 4% even in an accelerated water aging condition. The effect of absorbed moisture/water on the jute profile was more pronounced in an accelerated water aging than the samples are being exposed to high humidity and alternate wetting and drying cycles. The changes in the values of internal bond strength of the profiles could be used as an indicator because of its sensitivity towards aging. Accentuation of fibres on the weathered samples along with severe resin erosion has suggested to layer the surface of the profiles with rich resin prior to use in the outdoor. The properties of jute profile door frame were satisfactory when compared with the requirements mentioned in IS: 4021–83 – Indian standard specification for timber door, window and ventilator frames. Performance of the installed door frame has shown no sign of dimensional instability in terms of warping and bulging after 3 years. It is suggested that jute door frames could be used as an alternative to the wooden door frames in buildings.  相似文献   
143.
为提高轮式装甲车防护地雷的能力,寻找能够实现最佳防护效果的装甲结构形式,利用ANSYS/LS-DYNA软件平台,对不同的装甲结构在爆炸载荷作用下的响应进行仿真计算。首先探究多层圆管排列方式对冲击吸能的影响,得出密排圆管结构的抗冲击能力强于齐排和交叉排列的方式。然后在爆炸载荷下对由双层密排圆管组成的夹芯层防护结构进行数值计算,并对比试验结果,验证了所建立计算模型数值模拟结果的有效性。最后由数值计算结果确定了最佳的防护结构。数值模拟和试验结果表明,防护结构的面密度增大,防护效果明显改善;相同面密度的防护结构中圆管的直径越大,圆管的压缩行程越大,防护效果越好。  相似文献   
144.
南岳珍稀濒危动物的调查研究   总被引:1,自引:0,他引:1  
在南岳野生动物中,珍稀濒危动物共有28种,一级1种,即黄腹角雉TragopanCaboti;二级23种,其中哺乳类5种,鸟类15种,两栖类2种;中国生物多样性保护行动计划优先保护名录二级动物1种;中国优先保护动物中国特有种(A级)4种.本文主要介绍了它们的分类位置、形态特征和在我国的分布,根据南岳现有的资源状况,提出了保护措施与对策.  相似文献   
145.
黄河三角洲附近海域底栖动物多样性及其保护措施   总被引:5,自引:5,他引:5  
在对黄河王角洲附近海域30个站点底栖动物调查基础上,辅以文献资料法,综合分析了底栖动物物种多样性,研究了生物多样度以及与均度、单纯度之间的关系,并提出了保护底栖动物多样性的措施。结果表明:该海域共记录底栖动物222种,物种较为丰富;生物多样度为0~4.42,均度为0~2.01,单纯度为0.11~1.00;多样度与均度呈显著的正相关,与单纯度呈显著的负相关。  相似文献   
146.
目的考核评价高原环境下服役的直升机旋翼桨叶典型结构及其防护体系的耐腐蚀性能。方法利用建立的模拟高原环境加速试验谱,再现直升机旋翼桨叶结构防护体系实际服役过程中出现的腐蚀损伤,采取电化学阻抗谱测试研究涂层阻抗的变化。结果经历8个周期的户内加速试验后,新修桨叶试验件表面有机涂层Bode曲线呈现小幅下降,即有机涂层防护性能下降;报废桨叶试验件表面有机涂层的特定频率电化学阻抗模值与原始情况相比仅下降了不到1个数量级。结论报废桨叶试验件表面有机涂层电化学阻抗模值曲线在8个周期后仍然小幅高于未经历户内加速试验的新修桨叶试验件。  相似文献   
147.
Abstract

Several types of fabrics were laboratory‐tested for their effectiveness in worker protection to pesticide‐laden dust encountered in the agricultural environment. Of the applied <100 mesh dust, penetrations through knitted jersey and woven fabrics were greater than 87% and less than 5.8%, respectively. Treatment of woven fabrics with fluorocarbon polymers curtailed penetration by greater than 60%. Nonwoven fabrics allowed less than 0.5% dust penetration. Parathion mixed with 100‐mesh sieved dust resulted in increasing “ppm”; levels with decreasing particle size; extent of parathion conversion to paraoxon was independent of particle size for the sandy loam dust used.  相似文献   
148.
The article shows the problem of clogging in connection with the parameters of filtering materials used in respiratory protective equipment. The results of investigations of airflow resistance changes during the depositing of dust inside the filtering material are presented. The configuration of layers differing in mass per unit area and the number of layers, were taken into consideration. For each configuration, the clogging abilities and the changes of airflow resistance as a reason of loading with dust were assessed. The analysis of tested materials confirms the hypothesis that there is an important coincidence between the properties of the material used in filtering equipment and the clogging coefficient. The results show that the filter should have a layered structure and that the outer layer should be made of a nonwoven of relatively high surface density.  相似文献   
149.
The efficiency of a working coverall combined with personal protective equipment to protect operators against dermal exposure to plant protection products under field conditions was studied. Operators wore a non-certified water-repellent finish polyester/cotton coverall plus a certified gown during the mixing/loading and the cleaning phases. Insecticide foliar application to a vineyard was selected as the exposure scenario. The overall dermal residue levels measured in this study were in the range of data recently collected in Europe. The water-repellent finish working coverall reduced body exposure by a factor of approximately 95%. Wearing a Category III Type 3 partial body gown during mixing/loading and cleaning of the application equipment led to a further protective effect of 98.7%. The combination of a water-repellent finish working coverall and partial body protection during specific tasks provided satisfactory levels of protection and can be considered as suitable protection for the conditions of use studied.  相似文献   
150.
A great step toward the improvement of safety at work was made when electrosensitive protective devices (ESPDs) were applied to the protection of press and robot-assisted manufacturing system operators. The way the device is mounted is crucial. The parameters of ESPD mounting that ensure safe distance from the controlled dangerous zone are response time, sensitivity, and the dimensions of the detection zone. The proposed experimental procedure of response time measurement is realized in two steps, with a test piece penetrating the detection zone twice. In the first step, low-speed penetration (at a speed vm) enables the detection zone border to be localized. In the second step of measurement, the probe is injected at a high speed Vd. The actuator rod position is measured and when it is equal to the value L registered by the earlier measurements, counting time begins as well as the monitoring of the state of the equipment under test (EUT) output relays. After the state changes, time tp is registered. The experimental procedure is realized on a special experimental stand. Because the stand has been constructed for certification purposes, the design satisfies the requirements imposed by Polski Komitet Normalizacyjny (PKN, 1995). The experimental results prove the measurement error to be smaller than ± 0.6 ms.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号