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   138篇
  免费   2篇
  国内免费   3篇
安全科学   14篇
废物处理   1篇
环保管理   6篇
综合类   69篇
基础理论   9篇
污染及防治   8篇
评价与监测   24篇
社会与环境   1篇
灾害及防治   11篇
  2022年   3篇
  2021年   4篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   3篇
  2016年   4篇
  2015年   7篇
  2014年   9篇
  2013年   4篇
  2012年   2篇
  2011年   8篇
  2010年   3篇
  2009年   15篇
  2008年   11篇
  2007年   6篇
  2006年   1篇
  2005年   3篇
  2004年   4篇
  2003年   1篇
  2002年   4篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1994年   1篇
  1993年   7篇
  1992年   7篇
  1991年   7篇
  1990年   3篇
  1989年   2篇
  1987年   5篇
  1985年   3篇
  1984年   3篇
  1983年   1篇
  1982年   1篇
排序方式: 共有143条查询结果,搜索用时 15 毫秒
41.
介绍了徐州市环境安全监测预警系统的建设背景、适用范围与构成,明确了环境安全监测预警系统在徐州市国民经济和社会发展中的重要地位,阐述了徐州市应急监测系统与预警系统的职责与建设现状,总结了徐州市环境安全监测预警系统运行保障的思路与措施。  相似文献   
42.
环境风险预警方法与应急成套装备的应用展望   总被引:1,自引:0,他引:1  
介绍了环境风险预警方法建立的环境风险预警指标体系、环境风险源管理平台、环境风险源风险评估技术方法以及模块式应急成套装备的技术特点等;分析了环境风险预警方法与应急成套设备在危险化学品环境风险与应急管理,在区域大气环境挥发性有机污染物(VOCs)监控预警等方面的实际需求。面临现实的环境风险状况从环境风险防控与应急工程技术研究中心建设角度提出了需进一步完善、开发的环境风险预测预警技术与应急成套装备等新思路。  相似文献   
43.
This study assesses the reliability of estimating gestational age via crown-rump or gestational sac measurements obtained at 8 weeks' gestation or earlier as part of routine physician office practice. To accomplish this, we studied 88 pregnancies managed at 45 different sites in which both an early first-trimester ultrasonically-derived gestational age estimate and a second-trimester biparietal diameter (BPD) estimate were available. The first-and second-trimester determinations were highly correlated, but the first-trimester determinations were, on average, 0.43 weeks earlier than the second. The first-trimester estimates were satisfactory for use in interpreting maternal serum alpha-fetoprotein (MSAFP) screening measurements, but second-trimester BPD measurements obtained prior to MSAFP screening should be the method of choice for interpreting MSAFP values, due to the increased sensitivity for detecting open spina bifida.  相似文献   
44.
Cervieo-genital colonization with micro-organisms poses a potential threat to the pregnancy when transcervical (TC) CVS is performed. In order to evaluate this threat, cervical swabs in 478 patients were obtained and cultured for bacteria, yeasts, and mycoplasmas; chlamydias were detected by an enzyme immunology test. Two hundred and seventy-one patients had CVS (ione transvaginally and 207 underwent transabdominal (TA) CVS. Transvaginal specimens were obtained in 61.6 per cent by forceps biopsy. Overall in 29.9 per cent of patients micro-organisms were detected, the rate and distribution of different species being the same in both groups. There were 36 (7.5 per cent) miscarriages up to 28 weeks of gestation in the combined groups, 29 (10.7 per cent) in the TC-CVS group and 7 (3.4 percent) in the TA-CVS group. When miscarriages occurred after TC-CVS, bacteria/yeasts were involved in 10.3 per cent cif cases and mycoplasmas in 37.9 per cent, this proportion being almost the same in early (<2 weeks) and late (>2 weeks) miscarriages. After TA-CVS, in 28.6 per cent only mycoplasmas, and this only in late miscarriages (> 2 weeks), were involved, accounting for 40 per cent of late miscarriages.  相似文献   
45.
浙赣皖相邻地区燕山期大茅山、铜山、里山岭、黄山、伏岭等岩体主要由黑云母花岗岩组成,其中斜长石属钠长石和富钠更长石,黑云母呈它形填隙状,结晶晚于浅色矿物。岩石化学成分富SiO_2(73.92%-77.55%)、富碱(Na_2O+K_2O为7.81%~8. 67%),贫CaO(0.26%-0.92%)、MgO(0—0.45%);微量元素中富集Y、Nb、Zr等HFSE,贫过渡元素及Sr、Ba;稀土配分曲线呈“海鸥型”。这些特点与区内及华南I型和S型花岗岩明显不同,而具有A_2型花岗岩的典型特征。  相似文献   
46.
Our laboratory has received 1375 early amniotic fluid (EA) specimens during the past 5-year period for cytogenetics analysis. The gestational ages of the EA specimens were less than 14 weeks as estimated by ultrasound. The average volume of specimen received was 16 ml. Specimens were typically received in two collection tubes and cultured in Chang A and in supplemented MEM media using the in situ technique. Of the 1375 EA specimens received, 1356 were successfully cultured and yielded results. Abnormal results were found in 67 (4.9 per cent) of the cases. Nineteen specimens (1.4 per cent) failed to yield a result. The mean turn-around time (TAT) for all EA specimens was 8.28 days. In 1991, the average TAT for the EA specimens was 8.00 days compared with a TAT of 6.59 days for all specimens received over 14 weeks gestational age. The number of EA specimens received has increased from 1.5 per month in 1986 to 57 per month in 1991. In summary, our experience with EA specimens for cytogenetic analysis has demonstrated that the success rate is 98.6 per cent and that an increasing number of obstetricians are performing early amniocentesis as they seek to provide their patients with earlier results and an alternative to chorionic villus sampling.  相似文献   
47.
It is thought that young homing pigeons are able to use information acquired en route for their initial homeward orientation. However, the cues involved and mechanisms utilised are under discussion. Blocking light-dependent route-specific information during the first leg of an outward journey detour, together with analysis of pigeons that were raised under different loft conditions, allowed us to correctly evaluate the functioning of this mechanism and, more generally, the navigational map of birds. Pigeons from the same stock were raised and kept in two different lofts. The birds in the experimental groups were transported to the release sites via detours, and light-dependent information was denied during the first half of the outward journey (no compass information was available). Control birds were transported by the most direct route and had access to all available information. In general, the results showed that the low-loft birds preferred to use magnetic compass cues, whereas the high-loft birds preferred to use navigational map cues to collect information of the first part of the outward journey. The impairments observed in the homing performances of the experimental groups highlight the reliability of information collected inside the map area. Relevant to an understanding of the route-reversal mechanism was the evidence that this mechanism is able to function in the absence of compass information (birds raised in a wind-exposed loft show a detour effect). In systems where directional information could be provided by multiple sources, processing and extracting accurate course trajectories through a common mechanism may prove more efficient and reliable.  相似文献   
48.
Early amniocentesis from 9 to 14 weeks' gestation provides a safe and accurate method of prenatal diagnosis of cytogenetic and biochemical disorders. There was a 100 per cent success rate in culturing the amniotic cells from 222 samples obtained between 9 and 14 weeks' gestation. Follow-up of the patients to delivery revealed an abortion rate of 1·4 per cent. Among the 207 live- and stillborn infants, only one had a congenital abnormality (bilateral talipes equino-varus) and no infant had respiratory distress syndrome or pneumonia. Eleven pregnancies were terminated following the detection of a chromosomal, biochemical, or congenital abnormality (5·0 per cent). However, before the procedure of early amniocentesis becomes routine clinical practice, it requires appraisal by a randomized clinical trial.  相似文献   
49.
Network theory is commonly used to reveal social interactions and the organisation of interconnected nodes—but has not yet been applied to animal invasions. Non-native species invasions are now considered one of the foremost threats to natural ecosystems and biodiversity. This is the first attempt to assess social network properties within a freshwater fish assemblage invaded by a non-native fish species. We show that invasive sunbleak Leucaspius delineatus is socially more strongly interconnected with native species than the native species with each other. The social networks also reveal characteristics of a ‘small world’ such as low clustering coefficients C and short path lengths L. The findings may indicate potential traits of successful invaders and the implication for the spread of pathogens between individuals within a group of animals that contain a non-native invasive species. The success of establishment and subsequent invasion may be highlighted not only by the capacity of the new species to adapt to the new environment, but also in its capacity to penetrate the social circle of the native community.  相似文献   
50.
昭通地区滑坡泥石流预警系统及其减灾效益分析   总被引:6,自引:1,他引:5  
李观德 《灾害学》1998,13(1):50-52
阐述了昭通地区滑坡泥石流预警系统的由来与建立。该系统5a成功预报了11起滑坡泥石流灾害,419人幸免于难,预报成功率达58%。表明了在滑坡泥石流点多面广、灾情严重的地区建立预警系统是一条费省效宏的有效路子。  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