全文获取类型
收费全文 | 809篇 |
免费 | 3篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 17篇 |
废物处理 | 12篇 |
环保管理 | 74篇 |
综合类 | 178篇 |
基础理论 | 141篇 |
环境理论 | 2篇 |
污染及防治 | 304篇 |
评价与监测 | 52篇 |
社会与环境 | 39篇 |
灾害及防治 | 1篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 14篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 53篇 |
2015年 | 34篇 |
2014年 | 59篇 |
2013年 | 57篇 |
2012年 | 55篇 |
2011年 | 60篇 |
2010年 | 29篇 |
2009年 | 26篇 |
2008年 | 49篇 |
2007年 | 45篇 |
2006年 | 45篇 |
2005年 | 32篇 |
2004年 | 42篇 |
2003年 | 25篇 |
2002年 | 27篇 |
2001年 | 11篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1961年 | 1篇 |
1952年 | 1篇 |
排序方式: 共有820条查询结果,搜索用时 36 毫秒
761.
Morphological and histological studies of Alvinella pompejana (a polychaete living in the vicinity of hydrothermal vents of the East Pacific Ocean) were performed using light, scanning and transmission electron microscopy. The worms were collected in April–May 1979, during the Rise cruise by the submersible Alvin on the crest of East Pacific Rise at 21°N. The digestive tracts contained many sulfide particles (as determined by microprobe analysis) associated with organic matter and bacteria. Bacterial communities of different morphological types (cocci and filaments) were also observed at different levels of the worm's outer teguments. An atypical (possibly bacteria-derived) nutritional source of carbon and nitrogen for A. pompejana is indicated by the natural abundances of 13C:12C and 15N:14N in its tissues.Contribution No. 807 from Centre Océanologique de Bretagne, B.P. 337, F-29273 Brest Cédex, France 相似文献
762.
D. Hedgecock S. Launey A. I. Pudovkin Y. Naciri S. Lapègue F. Bonhomme 《Marine Biology》2007,150(6):1173-1182
The great fecundity and very high larval mortality of most marine invertebrates and fish make possible substantial variance
in the number of offspring contributed by adults to subsequent generations. The reproductive success of such organisms may
thus resemble a sweepstakes lottery, in which a minority of progenitors succeeds in replacing an entire population, while
the majority fails to procreate. One specific prediction of this hypothesis, that genetic diversity of newly settled cohorts
should be less than that of the adult population, is tested in the present study. Microsatellite DNA markers were examined
in naturally spawned juvenile European flat oysters Ostrea edulis (L.), collected over a 12-day period in 1993 from the western Mediterranean Sea, near Sète, France (43°32′N, 3°56′E) and
grown out for a period of up to 10 months. Variation in these juveniles was compared to that in a pooled sample of adults
collected in 1994 from two locations (Thau Lagoon and Port St. Louis) that had statistically homogeneous allelic frequencies.
Though nearly twice as large as the pooled adult sample, the juvenile sample had only 60% of the adult allelic diversity.
Analyses of linkage disequilibrium and kinship, as well as estimation of the effective number of parents, suggested that 10–20
adults produced this juvenile cohort. This observation supports the hypothesis of sweepstakes reproductive success and suggests
that partial inbreeding may occur even in species with large populations and dispersing planktonic larvae.
Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
763.
Claude D'Ercole Léon Boubli Jacqueline Franck Michel Casta Jean-Robert Harle Catherine Chagnon Ludovic Cravello Michèle Leclaire Bernard Blanc 《黑龙江环境通报》1995,15(12):1171-1175
We describe the case of a patient with systemic lupus erythematosus, treated by corticosteroids, who presented during two successive pregnancies with serological reactivation of toxoplasmosis associated with fetal lesions. The first infected fetus died in utero with signs of hydrops. The second fetus was treated in utero with a combination of sulfadoxine and pyrimethamine, administered to the mother, and is now well. The increasing number of immunocompromised pregnant patients with immunity to Toxoplasma gondii may lead to a higher risk of reactivation of maternal toxoplasmosis and congenital infection. 相似文献
764.
On the occasion of the anniversary a recollection is given of the history of the discovery of electron diffraction.
相似文献765.
Sylvie Lapègue Inès Ben Salah Frederico M. Batista Serge Heurtebise Lassad Neifar Pierre Boudry 《Marine Biology》2006,150(1):103-110
Despite the economic importance of oysters due to the high aquaculture production of several species, the current knowledge of oyster phylogeny and systematics is still fragmentary. In Europe, Ostrea edulis, the European flat oyster, and Ostreola stentina, the Provence oyster or dwarf oyster, are both present along the European and African, Atlantic and Mediterranean, coasts. In order to document the relationship not only between O. stentina and O. edulis, but also with the other Ostrea and Ostreola species, we performed a sequence analysis of the 16S mitochondrial fragment (16S rDNA: the large subunit rRNA-coding gene) and the COI fragment (COI: cytochrome oxidase subunit I). Oysters were sampled from populations in Portugal (two populations), Tunisia (two populations) and Morocco (one population), identified as O. stentina on the basis of shell morphological characters. Our data supported a high degree of differentiation between O. stentina and O. edulis and a close relationship between O. stentina and both Ostrea aupouria (from New Zealand) and Ostreola equestris (from Mexico Gulf/Atlantic). The status of this geographic disjunction between these closely related species is discussed. Furthermore, although identified in a separate genus Ostreola by Harry (Veliger 28:121–158, 1985), our molecular data on O. stentina, together with those available for the other two putative congeneric species, O. equestris and Ostreola conchaphila, would favour incorporation of Ostreola in Ostrea. Finally, a PCR-RFLP approach allowed the rapid identification of O. edulis and O. stentina. 相似文献
766.
This study investigates the feeding behaviour of the precious red coral Corallium rubrum on bacterioplankton. The effects of flow rate, prey concentration, and seawater temperature were tested. The results obtained
show that C. rubrum was able to prey on both pico- and nanoplankton cells. Flagellates constituted the major bacterioplankton food source in
terms of carbon and nitrogen, representing from 43 to 70% of the C and N ingested. Flow speed (2, 6, and 11 cm s−1) had no effect on grazing rates, maybe due to the small size of the ingested particles. Conversely, feeding rates increased
with prey concentration and seawater temperature. There was a doubling of the picoplankton ingestion rate for a sixfold increase
in its concentration. The ingestion of autotrophic flagellates, however, increased at the same time as their concentration,
indicating a preference for this type of food. Considering the range of concentrations typically found in the Ligurian Sea,
the ingestion of pico- and nanoplankton brings 148 ng C polyp−1 day−1 and 28 ng N polyp−1 day−1. This type of food represents only ca. 4.5% of the total carbon gained by C. rubrum from the different sources, but might be the most important in terms of nitrogen, phosphorus, and other essential elements. 相似文献
767.
Hélène Hégaret Gary H. Wikfors Philippe Soudant Christophe Lambert Sandra E. Shumway Jean Baptiste Bérard Patrick Lassus 《Marine Biology》2007,152(2):441-447
The possible effect of Alexandrium spp. containing paralytic shellfish poisoning (PSP) toxins on the hemocytes of oysters was tested experimentally. In one
trial, eastern oysters, Crassostrea virginica Gmelin, were exposed to bloom concentrations of the sympatric dinoflagellate, Alexandrium
fundyense Balech, alone and in a mixture with a non-toxic diatom, Thalassiosira weissflogii (Grun) Fryxell et Hasle. Subsequently, another experiment exposed Pacific oysters, Crassostrea gigas Thunberg, to a mixed suspension of the sympatric, toxic species Alexandrium catenella (Whedon et Kofoid) Balech, with T. weissflogii. Measurements of numbers of oyster hemocytes, percentages of different cell types, and functions (phagocytosis, reactive
oxygen species (ROS) production, and mortality) were made using flow-cytometry. During and after exposure, almost no significant
effects of Alexandrium spp. upon hemocyte numbers, morphology, or functions were detected, despite observations of adductor-muscle paralysis in
C. virginica and measured toxin accumulation in C. gigas. The only significant correlation found was between toxin accumulation at one temperature and higher numbers of circulating
live and dead hemocytes in C. gigas. The PSP toxins are known to interfere specifically with sodium-channel function; therefore, the finding that the toxins
had no effect on measured hemocyte functions suggests that sodium-channel physiology is not important in these hemocyte functions.
Finally, because oysters were exposed to the living algae, not purified toxins, there was no evidence of bioactive compounds
other than PSP toxins affecting hemocytes in the two species of Alexandrium studied. 相似文献
768.
D. Rivière 《Marine Biology》1983,75(1):19-23
Four copepod species (Acartia clausi, Centropages typicus, Temora stylifera, Calanus helgolandicus) from the northwest Mediterranean were subjected to electrophoresis on polyacrylamide gel in an attempt to distinguish specific biochemical characteristics for each species. Enzymograms of 5 enzymes were studied: esterases, leucine aminopeptidase, alkaline phosphatase, malate dehydrogenase and the malic enzyme. Marked interspecific differences were revealed, enabling specific biochemical identities to be established which can be useful as taxonomic criteria in the same way as morphological characteristics. The study was performed during different seasons in 1980. 相似文献
769.
Females of the Norway lobster Nephrops norvegicus (L.) incubate their eggs under the abdomen for a period of several months. We estimated the individual fecundity of N. norvegicus (1) before spawning, and (2) at the end of the incubation period. From these two relationships, we then calculated the average egg loss. Egg loss seems to be relatively higher for small females than for large ones. The mean egg loss estimated for the Bay of Biscay (45%) differs from the only other existing value (75%) calculated by other authors for Portuguese waters. Egg loss may regulate stock-density, and may be a mechanism intervening in stock-recruitment. In order to estimate the fecundity per recruit, fecundity at the end of the incubation period must be used: this takes into account the rate of egg loss as a function of female length.
Contribution No. 721, du Centre Océanologique de Bretagne 相似文献
Contribution No. 721, du Centre Océanologique de Bretagne 相似文献
770.
欧洲公园联盟 ( EUROPARC)制定了保护区可持续旅游的欧洲宪章 ,来促进完善的公园管理 .认证 的一个主要条件是保护区应具有一个经与当地的代表旅游、资源保护区和社区利益的利害攸 关者协商而精心制定的可持续旅游战略和行动计划 . 本文阐明了宪章制定的背景和一些有关 的问题及教训 . 相似文献