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271.
272.
Fu-Lin Evelyn Chu Eric D. Lund Paul R. Littreal Kate E. Ruck Ellen Harvey Jean-René Le Coz Yanic Marty Jeanne Moal Philippe Soudant 《Marine Biology》2009,156(2):155-169
The kinetics and efficiency of sterol production and bioconversion of phytosterols in two heterotrophic protists Oxyrrhis marina and Gyrodinium dominans were examined by feeding them two different algal species (Rhodomonas salina and Dunaliella tertiolecta) differing in sterol profiles. R. salina contains predominantly brassicasterol (≅99%) and <2% cholesterol. The major sterols in D. tertiolecta are ergosterol (45–49%), 7-dehydroporiferasterol (29–31%) and fungisterol (21–26%). O. marina fed R. salina metabolized dietary brassicasterol to produce 22-dehydrocholesterol and cholesterol. O. marina fed D. tertiolecta metabolized dietary sterols to produce cholesterol, 22-dehydrocholesterol, brassicasterol and stigmasterol. G. dominans fed either R. salina or D. tertiolecta metabolized dietary sterols to make cholesterol, brassicasterol and a series of unknown sterols. When protists were fed R. salina, which contains cholesterol, the levels of cholesterol were increased to a magnitude of nearly 5- to 30-fold at the phytoplankton-heterotrophic
protist interface, equivalent to a production of 172.5 ± 16.2 and 987.7 ± 377.7 ng cholesterol per mg R. salina carbon consumed by O. marina and G. dominans, respectively. When protists were fed D. tertiolecta, which contains no cholesterol, a net production of cholesterol by the protists ranged from 123.2 ± 30.6 to 871.8 ± 130.8 ng
per mg algal C consumed. Cholesterol is not only the dominant sterol, but a critical precursor for many physiologically functional
biochemicals in higher animal. As intermediates, these heterotrophic protists increase the amount of cholesterol at the phytoplankton–zooplankton
interface available to higher trophic levels relative to zooplankton feeding on algae directly. 相似文献
273.
Ab STEVELS Jaco HUISMAN Feng WANG Jinhui LI Boyang LI Huabo DUAN 《Frontiers of Environmental Science & Engineering》2013,7(4):475-482
This paper indicates that the performance of tack-back and treatment of electronic waste (e-waste) system can be improved substantially. This can be reached by better taking into account in a better way the big variety in material composition and potential toxicity of electrical and electronic products - from a technical, organizational and regulatory perspective. Realizing that there is no ‘one size fit for all’ and combining smart tailor made solutions with economic of sale will result in the best environmental gain/cost ratio. Several examples show how science and engineering have supported or will support this approach. 相似文献
274.
The current status of the treatment and disposal of hazardous wastes in China is summarized on the basis of the results of
the Declaring and Registration Project initiated nationally in 1995. A principle framework for the sound management of hazardous
wastes is proposed, which includes three levels of technical solutions. Large-scale enterprises are encouraged to recycle,
to treat, and to dispose of wastes by means of constructing facilities, and to have their extra capacities available to the
public for a reasonable fee. Municipal governments, provincial governments, and the Central Government are to plan and construct
centralized facilities to recycle, treat, and dispose of wastes. For a solution at the manufacturing level, recycling is identified
as the main approach. Centralized facilities at the municipal level will mainly focus on special wastes that are unsuitable
to transport and store, such as hospital waste, and for the technical solution at this level, incineration and recycling are
identified as the main approaches. For the technical solution at the provincial and national levels, landfill and incineration
are identified as the main approaches. Based on this principle and the current available data on hazardous wastes, a preliminary
plan for the spatial distribution of cross-provincial centralized treatment and disposal facilities of hazardous wastes is
presented. The construction of approximately nine cross-provincial comprehensive facilities is proposed. A priority list for
the construction of these planned facilities is also presented. 相似文献
275.
Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements 总被引:2,自引:0,他引:2
Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol was observed in the plants exposed to arsenic, which was not found in the control. The concentration of the unidentified thiol showed a very strong and positive correlation with arsenic concentration in the leaflets. The unidentified thiol was low in rachises and undetectable in the roots for As-treated plants. Total and acid-soluble thiols were also measured and the results indicated that arsenic mainly stimulated the synthesis of acid-soluble thiol in Chinese Brake. The investigations of other trace elements (Cd, Cu, Cr, Zn, Pb, Hg, and Se) showed that these elements were not accumulated in Chinese Brake to high levels and the synthesis of the unidentified thiol in the plant was not observed. Our study suggests that the unidentified thiol was induced specifically by arsenic and the distribution patterns of the unidentified thiol and arsenic in the plant were consistent, indicating that the synthesis of this compound was related to As exposure. 相似文献
276.
The Reproductive Health Response in Conflict (RHRC) Consortium designed a standardised questionnaire to measure gender-based violence (GBV) prevalence in conflict-affected settings. A preliminary field test was undertaken July-August 2002 in one urban and one rural district in East Timor to assess the prevalence of GBV among women 18-49 years of age during and after conflict. The field test used a cross-sectional survey design with a two-stage random selection process. During the year preceding East Timor's 1999 crisis, 23.8 per cent of respondents reported physical assault by an intimate partner; this rate was not significantly different in the year preceding the survey (24.8 per cent). Assault by perpetrators outside the family declined significantly from 24.2 per cent during the crisis to 5.8 per cent post-crisis for physical assault (p<.001) and 22.7 per cent during the crisis to 9.7 per cent post-crisis for sexual assault (p=0.046). The field test stimulated and informed additional research in East Timor, and the complementary findings of these research initiatives continue to be used to develop local policies and programming to prevent and address GBV. 相似文献
277.
278.
大气沉降可为上层海洋带来生物可利用性的营养元素(如N、P、Fe等),从而改变浮游植物的初级生产过程及群落结构,并影响海洋的碳循环.于2014年春季在南黄海开展2次船基围隔培养实验,通过人工添加沙尘、灰霾颗粒及多种营养盐来模拟大气沉降对海洋表层浮游植物生长的影响,结果表明:南黄海北部B07站浮游植物生长主要受到磷限制;南黄海中部H10站则主要受氮限制.沙尘添加在B07站和H10站均显著促进小型和微型浮游植物生长,对微微型浮游植物生长的促进作用不明显.灰霾添加在B07站对浮游植物生长总体呈现抑制作用,且主要抑制小型和微型浮游植物生长,对微微型浮游植物则为先抑制后促进;在H10站对浮游植物的影响整体呈现先抑制后促进,培养前期对各粒级浮游植物均有抑制作用,培养后期对微型和微微型浮游植物有促进作用. 相似文献
279.
280.
Teresa I. Schueller Erik V. Nordheim Benjamin J. Taylor Robert L. Jeanne 《Die Naturwissenschaften》2010,97(11):1017-1022
This study explores whether or not foragers of the Neotropical swarm-founding wasp Polybia occidentalis use nest-based recruitment to direct colony mates to carbohydrate resources. Recruitment allows social insect colonies to rapidly exploit ephemeral resources, an ability especially advantageous to species such as P. occidentalis, which store nectar and prey in their nests. Although recruitment is often defined as being strictly signal mediated, it can also occur via cue-mediated information transfer. Previous studies indicated that P. occidentalis employs local enhancement, a type of cue-mediated recruitment in which the presence of conspecifics at a site attracts foragers. This recruitment is resource-based, and as such, is a blunt recruitment tool, which does not exclude non-colony mates. We therefore investigated whether P. occidentalis also employs a form of nest-based recruitment. A scented sucrose solution was applied directly to the nest. This mimicked a scented carbohydrate resource brought back by employed foragers, but, as foragers were not allowed to return to the nest with the resource, there was no possibility for on-nest recruitment behavior. Foragers were offered two dishes—one containing the test scent and the other an alternate scent. Foragers chose the test scent more often, signifying that its presence in the nest induces naïve foragers to search for it off-nest. P. occidentalis, therefore, employs a form of nest-based recruitment to carbohydrate resources that is mediated by a cue, the presence of a scented resource in the nest. 相似文献