全文获取类型
收费全文 | 997篇 |
免费 | 139篇 |
国内免费 | 440篇 |
专业分类
安全科学 | 150篇 |
废物处理 | 17篇 |
环保管理 | 58篇 |
综合类 | 826篇 |
基础理论 | 304篇 |
污染及防治 | 102篇 |
评价与监测 | 56篇 |
社会与环境 | 49篇 |
灾害及防治 | 14篇 |
出版年
2024年 | 5篇 |
2023年 | 14篇 |
2022年 | 41篇 |
2021年 | 53篇 |
2020年 | 53篇 |
2019年 | 51篇 |
2018年 | 50篇 |
2017年 | 70篇 |
2016年 | 85篇 |
2015年 | 73篇 |
2014年 | 81篇 |
2013年 | 122篇 |
2012年 | 83篇 |
2011年 | 69篇 |
2010年 | 67篇 |
2009年 | 83篇 |
2008年 | 76篇 |
2007年 | 104篇 |
2006年 | 60篇 |
2005年 | 52篇 |
2004年 | 47篇 |
2003年 | 32篇 |
2002年 | 19篇 |
2001年 | 14篇 |
2000年 | 35篇 |
1999年 | 21篇 |
1998年 | 25篇 |
1997年 | 16篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1576条查询结果,搜索用时 31 毫秒
11.
12.
对影响葫芦岛市城区环境质量可吸入颗粒物的各类污染源颗粒物的粒度成份、分布特征进行分析。采用斯托克直径ds(Stoke's Diameter)表示法,利用巴柯离心机对样品进行处理,得到各类排放源所排放的不同粒径的颗粒物重量百分比,为环境管理提供科学依据。 相似文献
13.
14.
《环境科学学报(英文版)》2023,35(4):794-805
In this study, the effects of a diesel oxidation catalyst (DOC) coupled with a catalyzed diesel particulate filter (CDPF) with different catalyst loadings on the power, fuel consumption, gaseous and particulate emissions from a non-road diesel engine were investigated. Results showed that the after-treatment had a negligible effect on the power and fuel consumption. The reduction effect of the DOC on the CO and hydrocarbon (HC) increased with the engine load. Further reductions occurred coupling with the CDPF. Increasing the catalyst loading resulted in a more significant reduction in the HC emissions than CO emissions. The DOC could increase the NO2 proportion to 37.9%, and more NO2 was produced when coupled with the CDPF below 250°C; above 250°C, more NO2 was consumed. The after-treatment could reduce more than 99% of the particle number (PN) and 98% of the particle mass (PM). Further reductions in the PN and PM occurred with a higher CDPF catalyst loading. The DOC had a better reduction effect on the nucleation particles than the accumulation ones, but the trend reversed with the CDPF. The DOC shifted the particle size distribution (PSD) to larger particles with an accumulation particle proportion increasing from 13% to 20%, and the geometric mean diameter (GMD) increased from 18.2 to 26.0 nm. The trend reversed with the CDPF and the accumulation particle proportion declined to less than 10%. A lower catalyst loading on the CDPF led to a higher proportion of nucleation particles and a smaller GMD. 相似文献
15.
大气飘尘对大鼠肺细胞的毒性比较 总被引:1,自引:0,他引:1
采用大白鼠气管内注入飘尘后分析肺灌洗液的方法,比较了上海不同地区飘尘对大鼠肺细胞的毒性;再运用毒性指数及效应指数,综合评价了上海市不同地区大气飘尘污染的状况。研究表明:从肺灌洗液的生化成份分析及细胞分类显示,以彭浦新村、隆昌路平凉路、康定路胶州路3个点的飘尘毒性较大。综合评价结果,彭浦新村的效应指数最大,以后依次为康定路胶州路、鲁班路斜土路、青云路、隆昌路平凉路等。 相似文献
16.
17.
The adaptive significance of male polymorphism in the acarid mite Caloglyphus berlesei 总被引:5,自引:0,他引:5
Jacek Radwan 《Behavioral ecology and sociobiology》1993,33(3):201-208
Summary Two forms of males occur in the acarid mite, Caloglyphus berlesei. One of them uses its thickened third pair of legs to kill other males; the other, without modified legs, does not attack other males. Previous studies have shown that the form of the male is environmentally determined: fighter males develop only at low population densities and their development can be suppressed by substances emanating from dense colonies. In this study, the duration of development, longevity and virility of the two male morphs were measured. The only significant difference was that fighters had a shorter development time between the two last moults. In another experiment, two groups of colonies were maintained under the same conditions but had different numbers of individuals: small colonies contained 2 fighters and 2 non-fighters, whereas large colonies contained 30 males of each type. The relative reproductive success of both morphs was estimated from numbers of matings. In small colonies, the estimated reproductive success (ERS) was significantly higher for fighters than for non-fighters, mainly because in over 50% of these colonies a single fighter male managed to kill all the rival males and monopolize the females. The opposite was true in large colonies, in which non-fighters achieved significantly higher ERS, mainly because the fighters were killed in fights more often than the non-fighters. This implies that the ratio of costs to benefits obtained by adopting the fighter-male strategy increases with the number of rival males, which may explain conditional male development in C. berlesei. 相似文献
18.
19.
Small body size is generally correlated with r‐selected life‐history traits, including early maturation, short‐generation times, and rapid growth rates, that result in high population turnover and a reduced risk of extinction. Unlike other classes of vertebrates, however, small freshwater fishes appear to have an equal or greater risk of extinction than large fishes. We explored whether particular traits explain the International Union for Conservation of Nature (IUCN) Red List conservation status of small‐bodied freshwater fishes from 4 temperate river basins: Murray‐Darling, Australia; Danube, Europe; Mississippi‐Missouri, North America; and the Rio Grande, North America. Twenty‐three ecological and life‐history traits were collated for all 171 freshwater fishes of ≤120 mm total length. We used generalized linear mixed‐effects models to assess which combination of the 23 traits best explained whether a species was threatened or not threatened. We used the best models to predict the probability of 29 unclassified species being listed as threatened. With and without controlling for phylogeny at the family level, small body size—among small‐bodied species—was the most influential trait correlated with threatened species listings. The k‐folds cross‐validation demonstrated that body size and a random effect structure that included family predicted the threat status with an accuracy of 78% (SE 0.5). We identified 10 species likely to be threatened that are not listed as such on the IUCN Red List. Small body size is not a trait that provides universal resistance to extinction, particularly for vertebrates inhabiting environments affected by extreme habitat loss and fragmentation. We hypothesize that this is because small‐bodied species have smaller home ranges, lower dispersal capabilities, and heightened ecological specialization relative to larger vertebrates. Trait data and further model development are needed to predict the IUCN conservation status of the over 11,000 unclassified freshwater fishes, especially those under threat from proposed dam construction in the world's most biodiverse river basins. 相似文献
20.
Estimating abundance without recaptures of marked pallid sturgeon in the Mississippi River
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nicholas A. Friedenberg Jan Jeffrey Hoover Krista Boysen K. Jack Killgore 《Conservation biology》2018,32(2):457-465
Abundance estimates are essential for assessing the viability of populations and the risks posed by alternative management actions. An effort to estimate abundance via a repeated mark‐recapture experiment may fail to recapture marked individuals. We devised a method for obtaining lower bounds on abundance in the absence of recaptures for both panmictic and spatially structured populations. The method assumes few enough recaptures were expected to be missed by random chance. The upper Bayesian credible limit on expected recaptures allows probabilistic statements about the minimum number of individuals present in the population. We applied this method to data from a 12‐year survey of pallid sturgeon (Scaphirhynchus albus) in the lower and middle Mississippi River (U.S.A.). None of the 241 individuals marked was recaptured in the survey. After accounting for survival and movement, our model‐averaged estimate of the total abundance of pallid sturgeon ≥3 years old in the study area had a 1%, 5%, or 25% chance of being <4,600, 7,000, or 15,000, respectively. When we assumed fish were distributed in proportion to survey catch per unit effort, the farthest downstream reach in the survey hosted at least 4.5–15 fish per river kilometer (rkm), whereas the remainder of the reaches in the lower and middle Mississippi River hosted at least 2.6–8.5 fish/rkm for all model variations examined. The lower Mississippi River had an average density of pallid sturgeon ≥3 years old of at least 3.0–9.8 fish/rkm. The choice of Bayesian prior was the largest source of uncertainty we considered but did not alter the order of magnitude of lower bounds. Nil‐recapture estimates of abundance are highly uncertain and require careful communication but can deliver insights from experiments that might otherwise be considered a failure. 相似文献