全文获取类型
收费全文 | 1126篇 |
免费 | 18篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 39篇 |
废物处理 | 43篇 |
环保管理 | 142篇 |
综合类 | 235篇 |
基础理论 | 237篇 |
环境理论 | 3篇 |
污染及防治 | 326篇 |
评价与监测 | 71篇 |
社会与环境 | 53篇 |
灾害及防治 | 3篇 |
出版年
2023年 | 11篇 |
2022年 | 14篇 |
2021年 | 23篇 |
2020年 | 16篇 |
2019年 | 15篇 |
2018年 | 39篇 |
2017年 | 40篇 |
2016年 | 45篇 |
2015年 | 36篇 |
2014年 | 42篇 |
2013年 | 62篇 |
2012年 | 50篇 |
2011年 | 82篇 |
2010年 | 59篇 |
2009年 | 61篇 |
2008年 | 72篇 |
2007年 | 71篇 |
2006年 | 42篇 |
2005年 | 55篇 |
2004年 | 30篇 |
2003年 | 36篇 |
2002年 | 34篇 |
2001年 | 19篇 |
2000年 | 15篇 |
1999年 | 10篇 |
1998年 | 16篇 |
1997年 | 5篇 |
1996年 | 11篇 |
1995年 | 19篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1969年 | 2篇 |
1963年 | 2篇 |
1961年 | 2篇 |
1959年 | 3篇 |
1958年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有1152条查询结果,搜索用时 15 毫秒
461.
Geodiversity—the variability of Earth's surface materials, forms, and physical processes—is an integral part of nature and crucial for sustaining ecosystems and their services. It provides the substrates, landform mosaics, and dynamic physical processes for habitat development and maintenance. By determining the heterogeneity of the physical environment in conjunction with climate interactions, geodiversity has a crucial influence on biodiversity across a wide range of scales. From a literature review, we identified the diverse values of geodiversity; examined examples of the dependencies of biodiversity on geodiversity at a site‐specific scale (for geosites <1 km2 in area); and evaluated various human‐induced threats to geosites and geodiversity. We found that geosites are important to biodiversity because they often support rare or unique biota adapted to distinctive environmental conditions or create a diversity of microenvironments that enhance species richness. Conservation of geodiversity in the face of a range of threats is critical both for effective management of nature's stage and for its own particular values. This requires approaches to nature conservation that integrate climate, biodiversity, and geodiversity at all spatial scales. 相似文献
462.
Summary We studied pair bond maintenance in the pied flycatcher in an experiment on nest predation at the incubation stage. Males defending one or more additional nestboxes (i.e. polyterritorial) on the day of nest predation were significantly more successful in retaining their mate than were the monoterritorial males (54% and 13% succeed, respectively). We manipulated the number of nest sites available for renesting, and found that the females remained preferentially with those males that had access to a new site, regardless of the previous territorial status of the male. Thus, the success of the polyterritorial males in mate retention was related primarily to the resource defended (a new nest site) rather than to some quality of the particular males per se. When the females could choose between alternative nestboxes for renesting, they selected the one located at the greatest distance from the initial site (Fig. 1). Male polyterritorial behaviour has previously been interpreted as a means of achieving polygyny. Our results show that this behaviour may be advantageous even in the absence of polygyny, especially at high levels of nest predation. 相似文献
463.
Jan Jasiewicz 《Natural resources forum》1990,14(1):70-75
Energy cost for industry depends largely on the kind of energy used (or energy mix) and the in-country price of individual energy sources. The benefits of energy conservation measures may therefore not be uniform across industries and countries. A method is presented to evaluate the economics of energy conservation measures by industry. Thailand is used to illustrate how the method is applied. 相似文献
464.
465.
466.
467.
Female control of extra-pair fertilization in tree swallows 总被引:4,自引:0,他引:4
Summary In a Canadian population of tree swallows, Tachycineta bicolor, DNA fingerprinting has previously shown that half of all broods contain many offspring resulting from extra-pair copulations (EPCs), whereas the other half contain only legitimate offspring. This bimodal pattern of extra-pair paternity might be due to variation in the effectiveness of male paternity guards, variation in female ability to resist EPCs, and/or variation in female pursuit of EPCs. Here we report experimental evidence for female control of copulations and fertilizations and the occurrence of two alternative copulation strategies among females in this population. Ten paired male tree swallows were removed on the day their mates laid the first egg. Replacement males took over the nestbox within 0.5–23 h and attempted to copulate with the widowed female. Assuming that eggs were fertilized approximately 24 h prior to laying, the first two eggs were fertilized before the male was removed, while the third and subsequent eggs could potentially be fertilized by the replacement male. Fingerprinting revealed that the first two eggs were sired by the resident males in five nests and by extra-pair males in the remaining five nests. The widows that had been faithful to their initially chosen mate rejected copulation attempts by the replacement male until most of the eggs had been laid. Consequently, nearly all eggs laid by these females were sired by the original male. The widows that had been unfaithful prior to male removal copulated sooner with the replacement male than females that were faithful to their mate. However, these replacement males also had a very low fertilization success; most eggs were sired by males that were not associated with the nest. This is consistent with the situation in non-experimental nests where unfaithful females copulate with their mate at the same rate as faithful females, yet unfaithful females have a majority of offspring sired by extra-pair males. We conclude that fertilization patterns to a large extent are determined by the female through active selection and rejection of copulation partners, though our results also allow some speculation that females have control over sperm competition. Female copulation tactics are probably determined some currently unknown fitness benefits of having the offspring sired by particular males.Correspondence to: Raleigh J. Robertson 相似文献
468.
Antoon Opperhulzen Els W. v. d. Volde Frank A. P. C. Gobas Djlen A. K. Liem Jan M. D. v. d. Steen 《Chemosphere》1985,14(11-12)
Most polychlorinated naphthalones (PCN) accumulate rapidly according to their hydrophobicity. The uptake and ellmination rate constants are comparable to those of chlorinated benzenes and biphenyls.For most PCN-congeners the resulting bioaccumulation factors show an increase with increasing hydrophobicity. For higher Kd,oct-values (>105) however, no further increase of Kc is observed (Kc. max. = 3.5.104).For the two hepta- and the octachloronaphthalenes no detectable concentrations are found in the fishes, although no restricted blo-availability could be expected. Based on these observations and on data obtained from the literature. a loss of membrane permeation is suggested for hydrophobic molecules with widths over 9.5 Å.In addition a membrane permeation model, as part of the accumulation process of hydrophobic chemicals. Is proposed, which is based on diffusion and partition processes. 相似文献
469.
Brian P. Leaderer Jan A. J. Stolwijk Rebecca T. Zagraniski 《Environmental management》1977,1(2):131-137
A method is presented by which an upper limit of the adverse health effect of existing ambient CO concentrations on the U. S. population can be estimated. The method is based upon estimating the primary human physiological response to CO concentrations (COHb%) for the population in terms of person-hour-COHb>1.5% resulting from the time exposure of the population to CO concentrations in excess of the federally designated ambient air quality standard. The estimates of person-hour-COHb>1.5% are for exposures only to ambient CO concentrations and do not take into account the additional CO exposure for people who smoke or have occupational exposures.We estimate that there were up to 30.9×109 person-hour-COHb>1.5% in 1973 due to ambient concentrations in excess of the ambient 8-hour CO standard, with approximately 5×109 person-hour-COHb>1.5% occurring West of the Continental Divide and 25.9>109 person-hour-COHb>1.5% occuring East of the Continental Divide; of these 21.3×109 personhour-COHb>1.5% occurred in New York City. It was also estimated that a 60% reduction in 1973 ambient concentrations of CO (corresponding to an automotive emmision standard of less than 15 g/mile) would be needed to reduce to zero the person-hour-COHb>1.5%. The maximum estimated effects on the U.S. population of increases in ambient CO concentration above 1973 levels are also presented. 相似文献
470.
Jan D. Schmitt-Tegge 《Die Naturwissenschaften》1980,67(4):182-187
Special problems of treatment of hazardous wastes in the Federal Republic of Germany are discussed (i.e., evaluation of the manifest system, “hazardous-waste processes”, control). Special processes (incineration at sea, dumping, deep-well injection) are presented. The second part is a report about the congress of the American Chemical Society in Honolulu in April 1979, i.e., about the U.S. EPA Hazardous-Waste Program, about the abandoned hazardouswaste disposal sites and about several stabilization and solidification processes. 相似文献