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81.
Rebecca J. Safran Kevin M. Pilz Kevin J. McGraw Stephanie M. Correa Hubert Schwabl 《Behavioral ecology and sociobiology》2008,62(3):427-438
Recently, evidence is mounting that females can adaptively engineer the quality of their offspring via the deposition of yolk
compounds, including carotenoids and androgens. In this study, we simultaneously consider how both carotenoids and androgens
in egg yolk relate to parental quality in barn swallows (Hirundo rustica erythrogaster). First, we found no relationship between concentrations or amounts of yolk androgens and carotenoids. Yolk carotenoids decreased
with laying order, whereas we found no relationship between yolk androgens and laying order. Second, we tested the Investment
Hypothesis, which predicts that high-quality females or females paired to high quality mates, allocate differentially more
of these yolk compounds to their offspring. For carotenoids, we mostly found evidence to counter predictions of the Investment
hypothesis: (1) Carotenoid concentrations varied among females, (2) heavier eggs contained lower carotenoid concentrations,
although heavier yolks contained greater amounts of carotenoids, (3) eggs of earlier-laying females had lower concentrations
in their eggs, and (4) yolk carotenoids were not correlated with clutch size or male plumage ornamentation. For androgens,
we found weak support for the Investment Hypothesis: (1) Yolk androgens varied among females, (2) heavier eggs and yolks contained
greater amounts, although not concentrations of androgens, (3) females paired to more colorful males laid eggs with greater
concentrations of androgens, and (4) no effects of laying date or morphological correlates of female quality on androgen concentrations
in egg yolks. Overall, these findings suggest that each yolk compound may have different functions and therefore may be regulated
by different mechanisms. 相似文献
82.
We investigated the effects of population fluctuation on the offspring’s sex allocation by a weakly polygynous mouse, Apodemus argenteus, for 3 years. In acorn-poor seasons, heavier mothers invested more in sons, and lighter mothers invested more in daughters.
In acorn-rich seasons, heavier mothers invested more in daughters, and lighter mothers invested more in sons. Maternal body
condition and litter size affected the sex allocation. Furthermore, there was a maternal investment trade-off between a son’s
birth mass and the number of daughters. Based upon the effect of population fluctuation on the lifetime reproductive success
of each sex, we proposed the new “safe bet hypothesis”. This hypothesis predicts that frequent and unpredictable change in
female distribution, which is often caused by abrupt fall in food condition, favors female-biased maternal investment to offspring
by polygynous mammals and is applicable to many small mammals inhabiting in unstable environments. 相似文献
83.
Lydia H. Beaudrot Sonya M. Kahlenberg Andrew J. Marshall 《Behavioral ecology and sociobiology》2009,63(11):1549-1562
Infanticide is widespread among mammals, is particularly common in primates, and has been shown to be an adaptive male strategy
under certain conditions. Although no infanticides in wild orangutans have been reported to date, several authors have suggested
that infanticide has been an important selection pressure influencing orangutan behavior and the evolution of orangutan social
systems. In this paper, we critically assess this suggestion. We begin by investigating whether wild orangutans have been
studied for a sufficiently long period that we might reasonably expect to have detected infanticide if it occurs. We consider
whether orangutan females exhibit counterstrategies typically employed by other mammalian females. We also assess the hypothesis
that orangutan females form special bonds with particular “protector males” to guard against infanticide. Lastly, we discuss
socioecological reasons why orangutan males may not benefit from infanticide. We conclude that there is limited evidence for
female counterstrategies and little support for the protector male hypothesis. Aspects of orangutan paternity certainty, lactational
amenorrhea, and ranging behavior may explain why infanticide is not a strategy regularly employed by orangutan males on Sumatra
or Borneo. 相似文献
84.
中国城市土地市场有效性的实证研究 总被引:1,自引:0,他引:1
将有效市场假说应用于我国城市土地市场中,利用全国土地交易价格指数,采用序列相关检验、游程检验和方差比检验3种方法分别对我国城市土地市场的弱式有效性进行了实证检验,一致得出我国城市土地市场尚未达到弱式有效的结论.提出了对策建议:①营造公平、公开、公正的土地市场环境,发挥市场在配置土地资源方面的基础性作用.②打破对一级土地市场的垄断,构建城乡一体化的土地市场.③构建完善的土地市场指数系统,强化信息基础平台建设. 相似文献
85.
In financial time series, persistence or inertia is a feature usually observable in absolute returns, i.e., a proxy for volatility. Moreover, asset return series should be essentially unpredictable according to the efficiency market hypothesis (EMH) in its weak form. Surprisingly, recent literature has found evidence of anti-persistence in technology stocks and commodity futures returns. Anti-persistence would be indicative of an overreaction of asset prices to incoming information. 相似文献
86.
国家生态工业示范园是中国工业绿色转型的主要载体。本文基于创建国家生态工业示范园为切入点,采用多期双重差分法(difference-in-differences, DID)和2002-2017年上市公司的面板数据,实证考察了国家生态工业示范园对企业绿色创新的影响。研究发现:①创建国家生态工业示范园显著促进了企业绿色创新,平均提升了上市公司绿色发明专利0.883项,绿色实用专利0.465项;②事件分析表明,国家生态工业示范园与企业绿色创新之间存在着“先增后降”的倒“U”形关系;③国家生态工业示范园显著增加了企业环保投资,抑制了企业排污费,但与政府环保补助之间没有必然联系;④国家生态工业示范园更有助于非国有企业、经营状况比较好的企业以及东部经济发达地区的企业绿色创新,并且其绿色创新效应不集中于特定行业(如重污染行业)。本文从微观企业层面为理解创建国家生态工业示范园的经济社会效益提供了启发。 相似文献
87.
目前湖泊营养盐浓度级别评价常采用的平均值法忽视了变量的不确定性.本文据此提出一种基于正态分布总体均值假设检验的级别评价方法,并结合我国地表水环境质量标准(GB3838—2002)对营养盐浓度的分类,提出了简便快捷的图示法.结果发现,该方法能体现营养盐浓度变量的不确定性,融合先验级别假设,将决策风险定量化,可提供较为广阔的决策空间.同时,采用该方法对滇池外海观音山监测断面氨氮浓度的水质级别进行评价,发现先验级别假设、样本容量和决策偏好对评价结果有显著影响;与平均值法的比较发现,假设检验法具有更小的错误概率(例如,样本容量13时,风险0.21),评价结果具有更高的可信度,验证了假设检验法的适用性. 相似文献
88.
This work explores the heterogeneous effect of urbanization and nonrenewable energy consumption on the environment in 54 African nations. Panel data were used from 1996 to 2019. For estimation, panel quantile regression analysis, augmented mean group, panel threshold regression, and the environment Kuznets curve hypothesis were applied to check the relationship between income and carbon emissions. The study's outcome demonstrates that urbanization and nonrenewable energy consumption degrade the environment in Africa. Furthermore, an inverted U-shape relationship exists between economic growth and CO2 emissions, confirming the environmental Kuznets curve hypothesis. The findings indicate that urbanization should be planned; otherwise, urbanization can cause environmental degradation. African countries must adopt green urbanization and use renewable energy and clean manufacturing technologies. The institutions are encouraged to execute the standard, regulatory environment, and policies to reduce carbon emissions. Countries throughout the African continent should actively respond to the issues by charting a separate and diverse route for urban development. 相似文献
89.
As apex predators disappear worldwide, there is escalating evidence of their importance in maintaining the integrity and diversity of the ecosystems they inhabit. The largest extant marsupial carnivore, the Tasmanian devil (Sarcophilus harrisii) is threatened with extinction from a transmissible cancer, devil facial tumor disease (DFTD). The disease, first observed in 1996, has led to apparent population declines in excess of 95% in some areas and has spread to more than 80% of their range. We analyzed a long‐term Tasmania‐wide data set derived from wildlife spotlighting surveys to assess the effects of DFTD‐induced devil decline on populations of other mammals and to examine the relative strength of top–down and bottom–up control of mesopredators between 2 regions with different environmental conditions. Collection of the data began >10 years before DFTD was first observed. A decrease in devil populations was immediate across diseased regions following DFTD arrival, and there has been no indication of population recovery. Feral cats (Felis catus) increased in areas where the disease was present the longest, and feral cat occurrence was significantly and negatively associated with devils. The smallest mesopredator, the eastern quoll (Dasyurus viverrinus), declined rapidly following DFTD arrival. This result suggests the species was indirectly protected by devils through the suppression of larger predators. Rainfall deficiency was also a significant predictor of their decline. Environmental variables determined the relative importance of top–down control in the population regulation of mesopredators. In landscapes of low rainfall and relatively higher proportions of agriculture and human settlement, top–down forces were dampened and bottom–up forces had the most effect on mesopredators. For herbivore prey species, there was evidence of population differences after DFTD arrival, but undetected environmental factors had greater effects. The unique opportunity to assess population changes over extensive temporal and spatial scales following apex predator loss further demonstrated their role in structuring ecosystems and of productivity in determining the strength of top–down control. Cascadas Tróficas Después de la Declinación Inducida por Enfermedad de un Depredador Apical, el Demonio de Tasmania 相似文献
90.
R. S. Sikes 《Behavioral ecology and sociobiology》1996,38(5):303-310
The Trivers-Willard hypothesis of sex-biased maternal investment in response to fluctuations in resource availability has
provided a theoretical foundation for research on maternal investment for more than two decades. Their hypothesis holds that
mothers in poor condition as a result of poor resource availability should bias parental investment towards offspring with
the highest probability of reproducing. In the polygynous mating system of mammals where males compete for breeding access
to females, the hypothesis predicts investment favoring females. Although data from many systems have supported this hypothesis,
other systems do not follow the predicted patterns and have resulted in various alternative hypotheses. The present research
was designed to test whether differences in body condition of young reared by nutritionally stressed dams relative to young
reared by unstressed dams were maintained into adulthood, one of the fundamental assumptions underlying the Trivers-Willard
hypothesis. Post-weaning growth in eastern woodrats (Neotoma floridana) and northern grasshopper mice (Onychomys leucogaster) was examined relative to maternal nutritional plane. Individuals from undernourished dams were lighter than their unrestricted
counterparts at weaning but no difference was evident by the time they had reached adult size. Failure to maintain body condition
differences into adulthood violates one of the assumptions essential for application of the Trivers-Willard hypothesis of
maternal investment patterns. Although the Trivers-Willard model proposed that natural selection favors differential investment
in the sexes over the entire course of parental investment, evidence from this and other studies suggests that the Trivers-Willard
hypothesis might not be appropriate to address maternal investment questions in postnatally malnourished dams, but instead
should be restricted to systems concerned with prenatal maternal condition or resource availability.
Received: 22 February 1995/Accepted after revision: 30 December 1995 相似文献