全文获取类型
收费全文 | 9778篇 |
免费 | 368篇 |
国内免费 | 3800篇 |
专业分类
安全科学 | 734篇 |
废物处理 | 646篇 |
环保管理 | 859篇 |
综合类 | 5081篇 |
基础理论 | 1645篇 |
环境理论 | 2篇 |
污染及防治 | 3872篇 |
评价与监测 | 392篇 |
社会与环境 | 319篇 |
灾害及防治 | 396篇 |
出版年
2024年 | 5篇 |
2023年 | 151篇 |
2022年 | 482篇 |
2021年 | 391篇 |
2020年 | 283篇 |
2019年 | 264篇 |
2018年 | 355篇 |
2017年 | 457篇 |
2016年 | 521篇 |
2015年 | 668篇 |
2014年 | 807篇 |
2013年 | 1045篇 |
2012年 | 902篇 |
2011年 | 889篇 |
2010年 | 687篇 |
2009年 | 654篇 |
2008年 | 733篇 |
2007年 | 584篇 |
2006年 | 497篇 |
2005年 | 367篇 |
2004年 | 287篇 |
2003年 | 352篇 |
2002年 | 305篇 |
2001年 | 252篇 |
2000年 | 260篇 |
1999年 | 246篇 |
1998年 | 248篇 |
1997年 | 242篇 |
1996年 | 222篇 |
1995年 | 173篇 |
1994年 | 120篇 |
1993年 | 122篇 |
1992年 | 104篇 |
1991年 | 79篇 |
1990年 | 54篇 |
1989年 | 26篇 |
1988年 | 28篇 |
1987年 | 10篇 |
1986年 | 18篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
571.
通过对某市饮用水源中不同点位的三卤甲烷浓度测试,同时采用SOS/ Umu 试验对水体进行生物遗传毒性分析,结果表明:采用液氯消毒工艺的地表水厂在消毒后水样和用户端水样中检出的三卤甲烷含量较高,而采用二氧化氯消毒的地下水厂的出水中挥发性有机物仅略有上升;进行三卤甲烷浓度和生物遗传毒性之间的相关性分析得知,三卤甲烷和间接遗传毒性的相关性较好. 相似文献
572.
573.
作为体育产业重要组成部分的高校体育产业正面临着巨大的商机,蕴藏着巨大潜力.本文运用文献资料法,对我国高校体育产业化的现状进行分析,结合实际对我国高校体育产业化的发展提出相应的对策:更新观念、提高认识,积极创建体育俱乐部,充分利用自身的资源优势,开展多项经营,加速对体育经营管理人才的培养,严格遵循市场经济规律等. 相似文献
574.
提出一种“分解-重构-预测”小波网络的大气污染物浓度的预测方法。通过小波分解,把浓度序列分解为不同频段的小波系数序列,再对各层的小波系数子序列重构到原尺度上,然后对小波系数序列采用相匹配的BP神经网络模型进行预测,最后合成浓度序列的最终预测结果。经对二氧化硫浓度预测证明,该方法预测模型推广能力强,预测精度高。 相似文献
575.
576.
Safety instrumented systems (SISs) are commonly used in the process industry, to respond to hazardous events. In line with the important standard IEC 61508, SISs are generally classified into two types: low-demand systems and high-demand systems. This article explores this classification by studying the SIS reliability for varying demand rates, demand durations, and test intervals. The approach is based on Markov models and is exemplified by two simple system configurations. The SIS reliability is quantified by the probability of failure on demand (PFD) and the frequency of entering a hazardous state that will lead to an accident if the situation is not controlled by additional barriers. The article concludes that very low-demand systems are similar and may be treated as a group. The same applies to very high-demand system. Between these group, there is a rather long interval where the demand rate is neither high-demand nor low-demand. These medium-demand systems need a specific treatment. The article shows that the frequency of entering into a hazardous state increases with the demand rate for low-demand systems, while it is nearly independent of both the demand rate and the demand duration for high-demand systems. The PFD is an adequate measure for the SIS reliability for low-demand systems, but may be confusing and difficult to interpret for high-demand systems. 相似文献
577.
Gesi LiuYongzhi Zhao Yanlei Liu Jinyang ZhengShuiping Sheng Shuxin Han 《Journal of Loss Prevention in the Process Industries》2011,24(2):156-165
The explosion accident caused by residual pressure is one of the most common kinds of accidents in quick actuating pressure vessels. And it is important to provide some reliable methods, which can give reasonable analysis of the explosion. In this study, experiments of the explosion are preformed by using two quick actuating pressure vessels with residual pressure, and a new mathematical model is presented. The model is based on the combination of the Spalart-Allmaras turbulence fluid model and Newton’s second Law for the solid motion. And the model is solved with local remeshing method. By performing the simulation with the same parameters of experiments, the results of the simulation confirm the accuracy of the model. And the results shows the crucial factor of vessel structure, which the maximum ejected speed of the lid highly depends on. Based on that, the optimal design of the structure is presented, which can provide better security. 相似文献
578.
Both the net primary productivity (NPP) and the normalized difference vegetation index (NDVI) are commonly used as indicators
to characterize vegetation vigor, and NDVI has been used as a surrogate estimator of NPP in some cases. To evaluate the reliability
of such surrogation, here we examined the quantitative difference between NPP and NDVI in their outcomes of vegetation vigor
assessment at a landscape scale. Using Landsat ETM+ data and a process model, the Boreal Ecosystem Productivity Simulator,
NPP distribution was mapped at a resolution of 90 m, and total NDVI during the growing season was calculated in Heihe River
Basin, Northwest China in 2002. The results from a comparison between the NPP and NDVI classification maps show that there
existed a substantial difference in terms of both area and spatial distribution between the assessment outcomes of these two
indicators, despite that they are strongly correlated. The degree of difference can be influenced by assessment schemes, as
well as the type of vegetation and ecozone. Overall, NDVI is not a good surrogate of NPP as the indicators of vegetation vigor
assessment in the study area. Nonetheless, NDVI could serve as a fairish surrogate indicator under the condition that the
target region has low vegetation cover and the assessment has relatively coarse classification schemes (i.e., the class number
is small). It is suggested that the use of NPP and NDVI should be carefully selected in landscape assessment. Their differences
need to be further evaluated across geographic areas and biomes. 相似文献
579.
Characterizing hydrochemical properties of springs in Taiwan based on their geological origins 总被引:1,自引:0,他引:1
This study was performed to characterize hydrochemical properties of springs based on their geological origins in Taiwan.
Stepwise discriminant analysis (DA) was used to establish a linear classification model of springs using hydrochemical parameters.
Two hydrochemical datasets—ion concentrations and relative proportions of equivalents per liter of major ions—were included
to perform prediction of the geological origins of springs. Analyzed results reveal that DA using relative proportions of
equivalents per liter of major ions yields a 95.6% right assignation, which is superior to DA using ion concentrations. This
result indicates that relative proportions of equivalents of major hydrochemical parameters in spring water are more highly
associated with the geological origins than ion concentrations do. Low percentages of Na + equivalents are common properties of springs emerging from acid-sulfate and neutral-sulfate igneous rock. Springs emerging
from metamorphic rock show low percentages of Cl − equivalents and high percentages of HCO3-_{3}^{-} equivalents, and springs emerging from sedimentary rock exhibit high Cl − /SO42-_{4}^{2-} ratios. 相似文献
580.
Impact of socioeconomic development on ecosystem services and its conservation strategies: a case study of Shandong Province,China 总被引:1,自引:0,他引:1
Ecosystems and their components provide a lot of benefits for the welfare of human beings. Coupled with increasing socioeconomic
development, most of the rapidly developing and transitional countries and regions have been experiencing dramatic land use
changes. This has resulted in a large amount of forestland, grassland, and wetland being occupied as residential and industrial
land or reclaimed for arable land, which in turn results in a sharp deterioration of ecosystem services around the world.
Shandong Province, an economically powerful province of China, was chosen as a case study in order to capture the impact of
socioeconomic development on ecosystem services. By way of the study, land uses and their changes were categorized between
1980 and 2006, and the ecosystem services capital and changes of 111 counties of Shandong Province in different phases were
evaluated, as well as the total ecosystem services capital, followed by the zoning of ecosystem services function region of
Shandong Province. We found that the counties in mountainous areas and wetlands, where generally the prefectural-level cities
are located with a rapid socioeconomic development, experienced a successive deterioration of ecosystem services especially
during the 2000s. Finally, three conservation strategies for managing and improving ecosystem services were proposed and discussed
with the aim of achieving coordinate and sustainable development of the socioeconomy, environment, and ecosystems not only
in Shandong Province but also in other provinces of China, as well as in other developing and transitional countries and regions. 相似文献