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   421篇
  免费   29篇
  国内免费   49篇
安全科学   47篇
环保管理   37篇
综合类   241篇
基础理论   110篇
环境理论   1篇
污染及防治   16篇
评价与监测   10篇
社会与环境   25篇
灾害及防治   12篇
  2024年   3篇
  2023年   4篇
  2022年   11篇
  2021年   18篇
  2020年   11篇
  2019年   12篇
  2018年   8篇
  2017年   14篇
  2016年   14篇
  2015年   6篇
  2014年   8篇
  2013年   22篇
  2012年   10篇
  2011年   35篇
  2010年   13篇
  2009年   13篇
  2008年   18篇
  2007年   17篇
  2006年   29篇
  2005年   20篇
  2004年   23篇
  2003年   18篇
  2002年   16篇
  2001年   13篇
  2000年   4篇
  1999年   9篇
  1998年   6篇
  1997年   4篇
  1996年   4篇
  1995年   14篇
  1994年   15篇
  1993年   6篇
  1992年   10篇
  1991年   17篇
  1990年   3篇
  1989年   14篇
  1988年   10篇
  1987年   13篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   3篇
  1982年   2篇
  1981年   4篇
排序方式: 共有499条查询结果,搜索用时 921 毫秒
221.
Prenatal diagnosis for Tay-Sachs disease was performed on 25 patients using chorionic villus sampling (CVS). Nineteen were diagnosed as normal, and six were affected. Normal villus extracts had both hexosaminidase (hex) A and B activity, as determined by Cellogel and polyacrylamide gel electrophoresis, while extracts from affected fetuses had only hex B activity. Compared to cultured amniotic fluid cells or fibroblasts, villi contained less hex A. Hex A levels in fresh villi and cultured trophoblasts were roughly comparable.  相似文献   
222.
我国“硒与健康”数据库应用DATATRTIEVE数据管理系统管理数据;在VAX-11/780计算机上实现。它以我国公开刊物和文集为数据源。现存有五千个记录,约400种样品,遍及28个省市,主要反映的是克山病、大骨节病、硒中毒、某类癌症、心脏病等。依关键词:样品名、省、县、健康属性、分析方法等可以检索并输出所需样品含硒量数值报表。数据库能自动实现检索集合极大值、极小值选择,计算均值和标准差,进行单因素数据质量评价,并配有FORTRAN语言编写的模式识别为主的多元统计程序包,有助于多因素数据质量评价。  相似文献   
223.
Selenium concentration in hair are sorted out into three classes, i.e. low (<110 ppb), medium (110-520 ppb) and high (>520 ppb) according to the principle of multiple normal distribution and a map of classification of selenium concentration in hair from children and youngsters in China has been drawn. Selenium insufficiency in relation to Keshan disease and Kashin-Beck's disease is expounded. Geographical differentiation of hair selenium concentrations and its causes are explained.  相似文献   
224.
湘南地区天草主要病虫害发生特点及综合防治   总被引:1,自引:0,他引:1  
天草主要病害有炭疽病、煤烟病、日灼病和缺素症,主要害螨害虫有红蜘蛛、锈壁虱、蚜虫、潜叶蛾、柑桔象虫类、柑桔凤蝶和介壳虫类.文章总结了这些主要病虫害在天草上发生特点、时期及防治方法.  相似文献   
225.
Abstract:  Habitat loss and fragmentation can have strong negative impacts on populations of some native species. Spillover of generalist natural enemies from the surrounding landscape matrix is one mechanism potentially generating such effects, yet this has been rarely studied in insects. We examined the influence of habitat conversion to agriculture on the abundance and potential effects of predatory coccinellid beetles on native insect herbivores within 12 grassland remnants in central Nebraska (U.S.A.). Results of sweep sampling revealed that coccinellids were three to six times more abundant at native grassland sites embedded within cropland-dominated landscapes compared with control sites in grassland-dominated landscapes over the 3 years of the study. Exclusion experiments further demonstrated that predation intensity was strongly related to coccinellid abundances across sites and that coccinellids can dramatically reduce densities of a native aphid herbivore. In contrast to studies of specialized insect parasitoids, which have generally found reduced enemy pressure in fragmented landscapes, our results suggest that native herbivores may in some cases experience increased consumer pressure in landscapes with increasing habitat loss because of spillover of generalist predators from surrounding cropland habitats.  相似文献   
226.
豪猪常见疾病的综合防治技术研究   总被引:1,自引:0,他引:1  
通过探讨豪猪疾病发生的原因,介绍豪猪疾病诊断的方法、治疗的药物及其给药的方法、预防措施和防治的注意事项.详细论述了豪猪急性肺炎、肠炎、寄生虫病和外伤等常见疾病的综合防治技术.参9.  相似文献   
227.
This paper illustrates a method based on local likelihood (LL) for detecting disease clusters. The approach is based on estimating a lasso distance for each region: within which regions are considered to be clustered. An important advantage in implementing this approach is that it does not require any special Monte Carlo Markov Chain (MCMC) algorithm, e.g., reversible jump MCMC, which is essential in hidden Markov model approach. Another advantage is that extending the model to incorporate covariates is straightforward. We illustrate three ways of doing this by using Eastern Germany lip cancer data. By using simulated data, we have made a comparison with the BYM model [Besag et al. (1991) Annals of the Institute of Statistical Mathematics, 43, 1–59] and the mixture model [Lawson and Clark (2002) Disease Mapping and Risk Assessment for Public Health, Chapman and Hall]. We also did a limited examination of the ability of the LL model to recover true relative risk under different priors for lasso parameter. In order to check the edge effects, which has been overlooked in many spatial clustering models for disease mapping but deserves special attention as it lacks observable neighbors, we have adapted here a simple approach to observe the changes in relative risks when the edge regions are omitted. An erratum to this article is available at .  相似文献   
228.
《组织行为杂志》2017,38(5):749-766
To advance the understanding of socio‐relational sources of employee creativity, we investigate the effect of a good marriage on workplace creativity. Drawing on family–work enrichment theory, we propose and test the idea that a satisfying marriage boosts a spillover of psychological resources from family to work that enhances employees' workplace creativity. Using survey data collected from 548 spouse–employee–supervisor triads, we find an indirect positive relationship between employees' marital satisfaction and workplace creativity through a spillover of psychological resources from family to work. We also find that this spillover is most pronounced when both employees and their spouses are satisfied with their marriage. The results further demonstrate that the indirect effect of marital satisfaction on workplace creativity through the spillover of psychological resources is significant for employees with a low creative personality, but not for those with a high creative personality. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   
229.
Delphi法职业危害风险评估模型及案例研究   总被引:1,自引:0,他引:1  
为科学合理地进行建设项目职业病危害风险分类,基于系统工程及风险评估的基本原理,采用Delphi法分析和确定了影响职业病危害风险程度的因素,通过构建风险评估指标体系,建立了职业病危害影响因子赋值法(OHFA)定量化风险评估模型。根据对作业场所的危害源、本质及附加防护设施水平、人员接触机会、职业病防治管理等因子的综合分析,预测分析了研究对象的职业病危害的风险程度,为职业病危害风险辨识、风险评估、防治管理及防护设施设计等提供参考。并以某石化行业硫磺回收项目为实例进行应用与验证,得出了该项目的总体职业病危害风险度值为12,风险等级为Ⅰ级,各职业病危害因素的风险度由高到底排序为硫化氢、一氧化碳、二氧化硫、硫磺、高温,其风险分类的关键决定因素为硫化氢。实践表明该方法与专家评估结果及工程实际吻合较好,应用于职业病危害风险评估中可给出定量化的风险分类结果。  相似文献   
230.
采用广义相加模型和分布滞后非线性模型,研究单个气象要素和以"通用的热气候指数"表征的多要素综合效应与北京市2009~2012年呼吸系统疾病急诊人数的暴露-响应关系,并按年龄、性别分层.结果表明,对全人群而言,高温效应即时,低温作用滞后;湿度<30%能显著增加发病风险,且效应持久;3m/s风速对应发病风险最低.少儿(≤ 14岁)受热胁迫影响最强,尤其突出高温高湿作用;成人(15~59岁)受冷胁迫影响强且滞后性;老年患者(>60岁)对冷胁迫敏感,着重防范低温低湿.采用舒适指数探讨环境对呼吸系统疾病的影响优于单要素表征,可加深对发病气象成因的理解,为科学预防、预测预警提供新思路.  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