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911.
利用调制地震方法对华北地区1973年以来发生的24个ML≥5.5地震前地震调制比、地震调制比异常面积、调制地震条带和调制地震频度的异常变化进行分析,对异常类型进行分类。分析结果认为,华北地区ML≥5.5地震前地震调制比和异常面积随时间进程的起伏、调制地震频度震前数月的突然增大以及调制地震条带异常图象是显著的异常变化,可以用于对中、强地震的中期预报  相似文献   
912.
采用地震学异常度预测法对华南地区的地震活动趋势进行再研究,丰富了华南地区的地震学异常度预测震例,对全区未来地震趋势作出了较为合理的判断,尤其是对广西环江、荔波4.9级地震的跟踪预测和震后环境判定得出了令人信服的图象判据。  相似文献   
913.
对张北6-2 级地震震中区的地壳深部构造和靠近震中区的晋北地区的重力场变化进行了研究。认为,区域构造运动、地壳深部物质迁移和区域应力场的积累是这次地震的主要原因。晋北地区地震前后出现了明显的重力场变化,并具有异常范围大、幅度高的特点。  相似文献   
914.
通过对盱眙县鲍集等乡(镇)农村住房基本情况调查,反映了目前农村住房质量差,存在严重震灾隐患的问题。一旦遭遇5~6级中强地震,倒塌或严重破坏的房屋将占40%左右。分析原因,主要是广大农民抗震减灾意识淡薄,对农村建房疏于管理及农村建筑队伍技术力量薄弱。对此提出治理意见并建议地方政府在制定农村房屋建筑管理办法,使农村房屋基本达到抗震要求,最大限度减轻地震灾害损失。  相似文献   
915.
ABSTRACT: Many difficulties exist in the matching of models with data. This paper identifies elements of this problem and discusses considerations involved in model evaluation. The well known multivariate linear regression model is used to illustrate the distinctions between accuracy and precision and between estimation and prediction (because the model is commonly misused.) No amount of additional data will improve the accuracy of a poor model. A high R2, while indicative of a good matching between the observed data and model estimates, is a poor criterion for judging adequacy of the model to make good predictions of future events. Model evaluation also includes the problem of introducing secondary data and proxy variables into a model. Secondary data frequently enter, for example, the mass, energy and water budget equations because of difficulties in measuring the primary variables. Proxy variables arise because of a desire to collapse a vector of incomparable values, say, of water quality into a single number. Review of the above issues indicates that model evaluation is a multi-criterion problem, often imbedded in a larger framework where models are intended to meet multiple objectives. The mismatch of models and data has increasing legal and social consequences.  相似文献   
916.
Cellulose powder and softwood sawdust were subjected to alkaline degradation under conditions representative of a cementitious environment for periods of 7 and 3 years, respectively. During the first 3 years, sampling was frequent, and data on the degradation of cellulose and production of isosaccharinic acid was used for establishing long-term prediction models. Samples after an additional period of 4 years were compared to the predicted values. The total rate of degradation was measured as the increase in total organic carbon (TOC) in corresponding solutions. A previously published theoretical model of degradation kinetics gave a good approximation of the present experimental data. Peeling-off, stopping, and alkaline hydrolysis reaction rate constants were obtained as model parameters, and the results suggested that the transformation of the glucose end group is the rate-limiting step in the cellulose peeling-off reaction and also determines the pH dependence of that reaction. After 3 years, isosaccharinic (ISA) acid represented 70–85% of all degradation products as quantified by capillary zone electrophoresis. The long-term prediction model indicated that all of the cellulose would be degraded after only 150–550 years. The control sampling after 7 years points toward a lower degradation of cellulose and production of ISA than predicted by the model, reflecting either a degradation of ISA that was faster than the production or a termination of the ISA production.  相似文献   
917.
A large body of literature addresses the role of science in environmental impact assessment (EIA) but less attention has been given to the views of practitioners themselves. In this research a survey of 31 EIA practitioners in Western Australia was undertaken to determine their perceptions of the quality and importance of science in EIA. The survey results are compared with previous theoretical, empirical, and survey studies of the role of science in EIA. Interview questions addressed the role of science in impact prediction, monitoring activities, mitigation and management, and EIA decision-making. It was clear from the interviews that many practitioners are satisfied with the quality of science currently used in EIA, but do not believe that it is given sufficient importance in the process. The quality and importance of science in the predecision stages of EIA was rated higher than in the postdecision stages. While science was perceived to provide the basis for baseline data collection, impact prediction, and mitigation design, it was seen to be less important during decision-making and ongoing project management. Science was seen to be just one input to decision-makers along with other factors such as sociopolitical and economic considerations. While time and budget constraints were seen to limit the scientific integrity of EIA activities, pressure from the public and regulatory authorities increased it. Improving the scientific component of EIA will require consideration of all these factors, not just the technical issues.  相似文献   
918.
对1983-11-07山东菏泽5.9级地震前地下流体前兆异常特征进行了识别与研究,分析了菏泽5.9级地震前地下流体前兆异常的阶段性、层次性和同步性特征,利用震前地下流体高频突变异常频次速率和异常频次累加值的变化,采用地下流体层次跟踪震情预测方法对菏泽5.9级地震长期、中期和短临三个时间尺度的震情进行了检验性预测。  相似文献   
919.
酸雨pH预测的偏最小二乘回归模型   总被引:7,自引:0,他引:7  
酸雨pH值受酸性离子[SO4^2-]、[NO3^-]和碱性离子[Ca^2 ]、[NH4^ ]等的影响。这些影响因素之间存在多重相关性。用一般最小二乘回归法建模预测pH值,估计参数存在着很大的误差且物理意义明显不足。应用偏最小二乘回归技术建立pH值预测模型,克服了自变量之间的多重相关性的问题,因而更具有先进性,计算结果更为可靠。以我国17个城市pH值预测为例,探讨偏最小二乘法的优势,并与最小二乘回归法进行了比较。  相似文献   
920.
断层逸出气CO_2的有感小震前兆异常及预报意义   总被引:1,自引:0,他引:1  
简要介绍了目前国内断层逸出气CO2的主要观测状态与观测方法。给出了苏州地区近4年来5次有感小震群前断层逸出气CO2的前兆异常特征与典型图像,总结了它的灵敏性及其时、空、强的规律性,分析了它的超前时间、异常幅度、有效监测范围等特征及其对地震预报的实际意义。  相似文献   
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