全文获取类型
收费全文 | 537篇 |
免费 | 14篇 |
国内免费 | 9篇 |
专业分类
安全科学 | 23篇 |
废物处理 | 13篇 |
环保管理 | 143篇 |
综合类 | 52篇 |
基础理论 | 114篇 |
污染及防治 | 136篇 |
评价与监测 | 47篇 |
社会与环境 | 21篇 |
灾害及防治 | 11篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2019年 | 6篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 68篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 17篇 |
2008年 | 24篇 |
2007年 | 28篇 |
2006年 | 25篇 |
2005年 | 21篇 |
2004年 | 14篇 |
2003年 | 20篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有560条查询结果,搜索用时 46 毫秒
71.
Jacobsohn L García-España JF Durbin DR Erkoboni D Winston FK 《Journal of Safety Research》2012,43(1):21-28
IntroductionThe aim of this study was to quantify and identify correlates to the amount of parent-supervised behind-the-wheel practice hours by novice teen drivers.MethodsA national survey of 945 parents of recently licensed teen drivers was conducted. Multivariate logistic regression was used to identify factors related to the number of practice hours completed.ResultsSixty-one percent of parents reported practicing 50 or more hours with their teen. Two-parent involvement was associated with more practice hours, though use of a professional driving instructor was not. Parents of teens licensed in states mandating 50 or more hours of practice driving were more likely to report at least 50 practice hours than those in states mandating 20–40 hours or in states without mandates.Impact on IndustryThe findings underscore the integral role of parents in the learning to drive process and provide further support for GDL requirements for practice hours. 相似文献
72.
This paper examines how the discourse on state fragility affects the preferences of key actors in humanitarian governance for different types of health‐sector interventions in the Democratic Republic of Congo. It argues that, instead of focusing on the actual meaning of state fragility, attention should be paid to interactive processes around the discourse among stakeholders in the health sector. The lack of consensus on state fragility influences humanitarian governance, especially the perceptions of and interactions between the host government, donors, and international non‐governmental organisations. The latter have legitimised the persistence of vertical, emergency‐based interventions by emphasising state fragility, whereas state officials have preferred to assert political statehood and a higher degree of control. Nevertheless, they agree that donors’ financial contributions ensure the survival of the public health sector. Looking ahead, a policy coalition based on harmonised views about addressing fragility is necessary for effective engagement and the sustainability of interventions, but this is unlikely to happen any time soon. 相似文献
73.
Trade-off between mate guarding and mate attraction in the polygynous great reed warbler 总被引:5,自引:0,他引:5
Summary In a Swedish population of the polygynous great reed warbler Acrocephalus arundinaceus, about 40% of the males formed pairs with more than one female. Males sang two completely separated types of song: (1) long song when they tried to attract mates and (2) short shong when they guarded a fertile female. As soon as a male had attracted a female he immediately switched from long to short song and apparently guarded her for at least 3 days. Most males left their female and started singing long several days before her fertile period ended. This behavior probably increased the risk of cuckoldry. By assuming that males of polygynous species maximize their fitness over the whole breeding season (i.e., maximize fitness rate), we predicted longer mate guarding periods when the probability of attracting a second female was low and the risk of cuckoldry was high. These predictions were supported by observations. The probability of attracting a second female decreased during the breeding season and, in accordance, the number of days that males sang long song during the primary female's fertile period was negatively correlated with the time of the season. This trend held also for individual males when comparing mating periods of their primary and secondary female. The increasing rate of male intrusions with season may also have contributed to the increasing mate guarding periods.
Offprint requests to: D. Hasselquist 相似文献
74.
75.
Victoria?SorokerEmail author Dennis?R.?Nelson Ornit?Bahar Saadia?Reneh Sarah?Yablonski Eric?Palevsky 《Chemoecology》2003,13(4):163-168
Summary. Broad mite, Polyphagotarsonemus latus (Acari:
Tarsonemidae) exhibits a specific phoretic relationship with
whiteflies. Under field conditions most broad mites, caught
in sticky traps, are attached to whiteflies. Under laboratory
conditions, attachment occurs equally well in the dark and
light. Mites do not differentiate between the sexes of their
phoretic host Bemisia tabaci. However, mite attachment to
B. tabaci is greatly diminished by washing the host with
various organic solvents, chloroform in particular. The
effect of whitefly waxy particles on broad mite behavior was
studied using wax from the whitefly Aleyrodes singularis
and from the mealybug Planococcus citri. Broad mites were
not only attracted specifically to the A. singularis waxy
particles-treated leaf areas but were also attached to leaf
trichomes in this area. The results of this study suggests the
importance of olfactory cues from the whitefly waxy particles
in the recognition process of the phoretic host and/or
the induction of the attachment behavior to whitefly legs or
leaf trichomes. 相似文献
76.
77.
Wolfgang Forstmeier Dennis Hasselquist Staffan Bensch Bernd Leisler 《Behavioral ecology and sociobiology》2006,59(5):634-643
Song complexity is often regarded as a sexually selected trait that reflects the overall quality of a male. In many passerine
species, old males possess larger song repertoires than younger males. This may be either because individual males improve
their performance as they get older (longitudinal increase) or because poor singers have reduced viability and, hence, are
underrepresented in old age classes (cross-sectional increase). We studied the age dependence of repertoire size and other
song traits in a German and a Swedish great reed warbler (Acrocephalus arundinaceus) population. We found marked differences between longitudinal and cross-sectional approaches, as well as between the two
study populations. In the German population, we found that syllable switching, a measure of immediate versatility and strophe
length, increased with age in a cross-sectional analysis. This was not because birds improved with age (longitudinally) but
because syllable switching was positively correlated with male longevity. However, in Sweden, syllable switching seemed to
be unrelated to age and longevity. In the Swedish population, individual males increased their repertoire size as they got
older (longitudinal increase), but this did not happen in the German population. Hence, two populations, even when belonging
to the same subspecies, may differ in whether or not they show delayed song maturation. 相似文献
78.
Mario F. Teisl Brian Roe Robert L. Hicks 《Journal of Environmental Economics and Management》2002,43(3):339
In this paper we test whether the dolphin-safe labels altered consumer purchases of tuna. We also provide a partial measure of the total welfare effects of the dolphin-safe labeling policy. The results confirm our hypothesis that the dolphin–tuna controversy and the subsequent implementation of dolphin-safe labeling affected consumer behavior. Further, the paper provides market-based evidence that consumers can respond to eco-labels; the dolphin-safe label increased the market share of canned tuna. The welfare analysis provides a partial measure of society's willingness to pay to avoid personally contributing to dolphin mortality as a result of tuna fishing. 相似文献
79.
H. S. J. Roe 《Marine Biology》1983,77(3):287-298
The relationship between the vertical distributions of euphausiids and fish and light intensity has been studied directly by using a photometer in conjunction with an acoustically controlled rectangular midwater trawl. Samples were taken at a position centered on 47°N; 17°W on 15 and 16 May 1978. Five species of euphausiid and six species of fish have been analysed, both groups contained migrant and non-migrant species. The population of each of these species occurred throughout a light regime spanning at least three orders of magnitude of intensity; none of them was restricted to, or followed, and isolume. There were no sexual or size differences in the distributions of the euphausiids, but the population of Argyropelecus hemigymnus was probably stratified during the day, with smaller individuals occurring shallower than large ones. The results are discussed in relation to previous observations and to the theories of photic regulation of distributions and migrations. 相似文献
80.
Most resource allocation models developed to aid resource planning have been deterministic; that is, the ecosystem and economic variables are assumed to be known with certainty. It is these elements that present problems concerning risk and uncertainty involved in decision making. The objective of this study is to present a mathematical approach for optimizing resource allocation in management situations in which random events occur. This particular technique of decision analysis is chance-constrained programming. The model makes possible the investigation of risk and uncertainty associated with resource management decision making. Range decision-makers must often stock their range before they are sure of the available forage; thus, the amount of available forage is a random element with which managers must contend. The chance-constrained approach to decision making may be used when such random events occur and when it is not possible to plan exactly for future events. Two parameters are used to adjust the mean value of constraints; these are the standard deviation of the constraint value (Sbi) and the probability term which is specified by the manager (Kαi). The mean values are adjusted by the product KαiSbi. In the study reported here, a Kαi value of 0.57 gave results which appeared to have usefulness. The results indicate that the penalties a rancher must assume for over-estimating his carrying capacity are greater than the penalties for underestimating the carrying capacity. With the value of the standard deviation used in the example, numbers of livestock and the corresponding net revenues should be about 22% less than those indicated by average forage production. With greater variation in forage production, the reduction would be greater. By using these values, the chance-constrained approach can meaningfully incorporate random variables into a decision model. 相似文献