全文获取类型
收费全文 | 1517篇 |
免费 | 48篇 |
国内免费 | 23篇 |
专业分类
安全科学 | 61篇 |
废物处理 | 65篇 |
环保管理 | 335篇 |
综合类 | 125篇 |
基础理论 | 481篇 |
环境理论 | 4篇 |
污染及防治 | 297篇 |
评价与监测 | 110篇 |
社会与环境 | 84篇 |
灾害及防治 | 26篇 |
出版年
2023年 | 11篇 |
2022年 | 25篇 |
2021年 | 33篇 |
2020年 | 27篇 |
2019年 | 30篇 |
2018年 | 39篇 |
2017年 | 52篇 |
2016年 | 56篇 |
2015年 | 51篇 |
2014年 | 54篇 |
2013年 | 131篇 |
2012年 | 74篇 |
2011年 | 120篇 |
2010年 | 73篇 |
2009年 | 88篇 |
2008年 | 105篇 |
2007年 | 96篇 |
2006年 | 77篇 |
2005年 | 56篇 |
2004年 | 56篇 |
2003年 | 51篇 |
2002年 | 34篇 |
2001年 | 16篇 |
2000年 | 15篇 |
1999年 | 20篇 |
1998年 | 15篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有1588条查询结果,搜索用时 46 毫秒
191.
The Colony Structure and Population Biology of Invasive Ants 总被引:6,自引:0,他引:6
192.
Frank C. Curriero Michael E. Hohn Andrew M. Liebhold Subhash R. Lele 《Environmental and Ecological Statistics》2002,9(1):89-110
Geostatistics is a set of statistical techniques that is increasingly used to characterize spatial dependence in spatially referenced ecological data. A common feature of geostatistics is predicting values at unsampled locations from nearby samples using the kriging algorithm. Modeling spatial dependence in sampled data is necessary before kriging and is usually accomplished with the variogram and its traditional estimator. Other types of estimators, known as non-ergodic estimators, have been used in ecological applications. Non-ergodic estimators were originally suggested as a method of choice when sampled data are preferentially located and exhibit a skewed frequency distribution. Preferentially located samples can occur, for example, when areas with high values are sampled more intensely than other areas. In earlier studies the visual appearance of variograms from traditional and non-ergodic estimators were compared. Here we evaluate the estimators' relative performance in prediction. We also show algebraically that a non-ergodic version of the variogram is equivalent to the traditional variogram estimator. Simulations, designed to investigate the effects of data skewness and preferential sampling on variogram estimation and kriging, showed the traditional variogram estimator outperforms the non-ergodic estimators under these conditions. We also analyzed data on carabid beetle abundance, which exhibited large-scale spatial variability (trend) and a skewed frequency distribution. Detrending data followed by robust estimation of the residual variogram is demonstrated to be a successful alternative to the non-ergodic approach. 相似文献
193.
194.
195.
The transuranium elements, Np, Pu and Am discharged from the BNFL fuel reprocessing plant at Sellafield have accumulated in
the local environment. The processes responsible for their dispersal rely both on physical transportation and their chemical
reactivity. The transuranics have a complex chemistry, with multiple oxidation states and a strongly polarising character.
In the environment, the particle active III/IV and more mobile VNI oxidation state groups are important and govern their geochemical
behaviour and subsequent dispersal.
Studies of the behaviour of the transuranics, particularly Pu, in the Irish Sea, have shown that the majority of the radionuclides
in the liquid effluent discharged from Sellafield, quickly becomes associated with the marine sediments. Their dispersal and
distribution in the environment is then governed primarily by the movement of particulate material and for some sites it has
been suggested that sediment profiles preserve the historical record of discharges from the plant.
In tidally inundated soils, radionuclide levels are greatly enhanced. These soils are water-logged for long periods of the
year, are strongly anoxic and accretion rate are very low. The distribution of Np, Pu and Am in the soil suggests that simple
sedimentary accumulation mechanism cannot provide an adequate explanation for the profiles observed. From preliminary studies
of soil pore water composition and detailed analysis of the variation of isotopic ratios in the soil cores, it is apparent
that a small but significant component of the radionuclide inventory is mobile. In addition, it is clear that the mechanisms
responsible for this mobility allows differentiation between the transuranium nuclides. 相似文献
196.
Summary Non-random mating by size (NRMS) plays a central role in the study of sexual selection and the evolution of mating systems. Theory suggests that NRMS should be influenced by conflicting demands (e.g., predation risk, hunger); few experimental studies, however, have addressed these effects. We used a factorial experiment to examine the influence of predatory green sunfish and food deprivation on NRMS in male and female stream water striders, Aquarius remigis. As predicted by theory, food deprivation decreased the large-male mating advantage. The influence of predation risk, however, went against existing theory; that is, risk increased the large male mating advantage. The degree of large-male mating advantage was negatively related to a measure of the rate of male harassment of females. A behavioral mechanism that can explain these patterns emphasizes the contrasting effects of different competing demands on male harassment rates, female resistance and the role of male size in overcoming female resistance. Females usually resist male mating attempts. Successful mating occurs when males overcome female resistance. If harassment rates (of females by males) are low, larger males have a mating advantage over smaller males perhaps because females resist heavily and thus only larger males can overcome female resistance. If, however, male harassment rates are very high, female resistance might be swamped; mating should then be more random with respect to male size. Food deprivation increases gerrid activity and thus increases harassment rates which should then reduce NRMS. In contrast, risk decreases gerrid activity, thus decreasing harassment rates and increasing NRMS. Females did not show significant NRMS. Females did, however, show a pattern of change in NRMS that is consistent with male choice for larger females.
Correspondence to: A. Sih 相似文献
197.
A spatially explicit individual-based simulation model has been developed to represent aphid population dynamics in agricultural landscapes. The application of the model to Rhopalosiphum padi (L.) population dynamics is detailed, including an outline of the construction of the model, its parameterisation and validation. Over time, the aphids interact with the landscape and with one another. The landscape is modified by varying a simple pesticide regime, and the multi-scale spatial and temporal implications for a population of aphids is analysed. The results show that a spatial modelling approach that considers the effects on the individual of landscape properties and factors such as wind speed and wind direction provides novel insight into aphid population dynamics both spatially and temporally. This forms the basis for the development of further simulation models that can be used to analyse how changes in landscape structure impact upon important species distributions and population dynamics. 相似文献
198.
Courtship displays and paternal care in male birds are generally thought to be mutually exclusive, because testosterone, necessary for stimulation of sexual behaviours, suppresses paternal behaviours. Superb fairy-wrens, Malurus cyaneus, are unusual in that males concurrently engage in courtship and paternal care. Fairy-wrens live in stable socially monogamous pairs with 0-4 subordinate male helpers. Both helper and dominant males provide care whenever it is required but continue courtship throughout the period of care as most fertilisations are extra-group and females are multi-brooded. To examine the role of testosterone in this trade-off, we compared testosterone levels in males of different social status, while they had dependent nestlings, and determined the effect of testosterone treatment on provisioning rates of pairs. Testosterone levels were lower in subordinate helpers, although these do not provide more paternal care than dominant males. Conversely, testosterone levels were similar in dominant males with or without helpers, although as the number of helpers increases males invest substantially less in nestling care and more in extra-group courtship. Although testosterone levels are high, irrespective of paternal duties, experimental testosterone treatment of males resulted in a large (65%) reduction in nestling feeding rates. Surprisingly, there was no indication that females compensated for this reduction in provisioning, suggesting that females might assume a constant male contribution to offspring care. We conclude that during nestling provisioning, male fairy-wrens maintain testosterone at an individual level that does not interfere with parental duties, while allowing high investment in extra-group courtship. 相似文献
199.
The leopard shark (Triakis semifasciata) is an important predator in coastal marine ecosystems of California, targeted by recreational and commercial fishermen and
of specific interest in fisheries management. From October 2003 to August 2006, 169 leopard sharks were collected from the
coast of California (between 40.750°N and 32.678°N) and analyzed for mitochondrial and nuclear genetic structure. Analyses
of mtDNA control region sequences revealed relatively low levels of genetic variation (five haplotypes, average pairwise divergence
π = 0.0067). In contrast, leopard sharks were highly polymorphic for inter simple sequence repeats (ISSRs), which characterize
a broad range of the nuclear genome. The null hypothesis of panmixia in California waters was rejected for both genetic markers,
and ISSRs displayed a statistically significant pattern of isolation by distance (IBD) across the species range (P = 0.002). A variety of analyses showed that divergence is most pronounced in the northernmost population of Humboldt Bay.
Natal philopatry in T. semifasciata was tested using Siegel-Tukey tests on data partitioned by breeding site status, and sex-specific philopatry was tested by
comparing IBD plots between sexes. Although there was some evidence for natal philopatry in leopard sharks (P = 0.038), and population divergence may be related to the proximity of breeding sites (P = 0.064), we found no support for sex-specific philopatry. In addition to identifying a novel set of highly variable genetic
markers for use in shark population studies, these results may be used to better inform management decisions for leopard sharks
in California. 相似文献
200.
We present a strategy for using an empirical forest growth model to reduce uncertainty in predictions made with a physiological process-based forest ecosystem model. The uncertainty reduction is carried out via Bayesian melding, in which information from prior knowledge and a deterministic computer model is conditioned on a likelihood function. We used predictions from an empirical forest growth model G-HAT in place of field observations of aboveground net primary productivity (ANPP) in a deciduous temperate forest ecosystem. Using Bayesian melding, priors for the inputs of the process-based forest ecosystem PnET-II were propagated through the model, and likelihoods for the PnET-II output ANPP were calculated using the G-HAT predictions. Posterior distributions for ANPP and many PnET-II inputs obtained using the G-HAT predictions largely matched posteriors obtained using field data. Since empirical growth models are often more readily available than extensive field data sets, the method represents a potential gain in efficiency for reducing the uncertainty of process-based model predictions when reliable empirical models are available but high-quality data are not. 相似文献