全文获取类型
收费全文 | 101607篇 |
免费 | 1257篇 |
国内免费 | 1349篇 |
专业分类
安全科学 | 3971篇 |
废物处理 | 3912篇 |
环保管理 | 15034篇 |
综合类 | 22243篇 |
基础理论 | 27871篇 |
环境理论 | 79篇 |
污染及防治 | 19603篇 |
评价与监测 | 6206篇 |
社会与环境 | 4691篇 |
灾害及防治 | 603篇 |
出版年
2022年 | 967篇 |
2021年 | 967篇 |
2020年 | 730篇 |
2019年 | 974篇 |
2018年 | 1449篇 |
2017年 | 1478篇 |
2016年 | 2471篇 |
2015年 | 1984篇 |
2014年 | 2776篇 |
2013年 | 9522篇 |
2012年 | 2759篇 |
2011年 | 3364篇 |
2010年 | 3582篇 |
2009年 | 3722篇 |
2008年 | 2964篇 |
2007年 | 2869篇 |
2006年 | 2985篇 |
2005年 | 2810篇 |
2004年 | 3059篇 |
2003年 | 2954篇 |
2002年 | 2443篇 |
2001年 | 2902篇 |
2000年 | 2303篇 |
1999年 | 1679篇 |
1998年 | 1413篇 |
1997年 | 1421篇 |
1996年 | 1539篇 |
1995年 | 1635篇 |
1994年 | 1537篇 |
1993年 | 1369篇 |
1992年 | 1379篇 |
1991年 | 1336篇 |
1990年 | 1302篇 |
1989年 | 1244篇 |
1988年 | 1079篇 |
1987年 | 1021篇 |
1986年 | 1003篇 |
1985年 | 1081篇 |
1984年 | 1176篇 |
1983年 | 1183篇 |
1982年 | 1181篇 |
1981年 | 1102篇 |
1980年 | 962篇 |
1979年 | 941篇 |
1978年 | 835篇 |
1977年 | 725篇 |
1976年 | 648篇 |
1974年 | 633篇 |
1973年 | 646篇 |
1972年 | 657篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
F. Rincón-León G. Zurera-Cosano R. Moreno-Rojas M. Amaro-López 《Environmental monitoring and assessment》1993,27(3):193-200
The importance of eating habits and the number of fish sampled in the estimation of mercury environmental contamination through biological indicators was studied. The species used were one with piscivorous habits (Anguilla anguilla) and another with omnivorous habits (Ciprinus carpio). From one original sample for each species, randomized samples were generated using the subroutine GGSRS from the mathematics library IMSL, and later the statistical significance of Pearson's correlation coefficient for the relationship between fish weight and mercury concentrations in muscle was obtained for each random sample. The results show that the use of omnivorous species such as Ciprinus carpio as a biological indicator of contamination enables us to carry out estimations with a greater degree of confidence than when piscivorous species such as Anguilla anguilla are used. 相似文献
72.
Certain hydrothermal vent invertebrates, e.g. Riftia pachyptila and Calyptogena magnifica, are clearly established as harboring dense populations of chemoautotrophic sulfur bacteria in specialized tissues. By contrast, the physiological characteristics of the abundant intracellular gill symbiont of the vent mussel Bathymodiolus thermophilus have been questioned. The low activities of enzymes diagnostic for CO2 fixation (Calvin cycle) and for sulfur-driven energy generation, as measured by other investigators, have been attributed to bacterial contamination of the gill surface. Based on research at the Galápagos Rift hydrothermal vents in 1988 and subsequent laboratory experiments, the current study confirms that the B. thermophilus symbiont is a psychrophile for which thiosulfate and sulfide stimulate CO2 fixation. It strongly indicates that the symbiont is a chemoautotroph by establishing the following: (1) Sulfide and thiosulfate can stimulate CO2 fixation by partially purified symbionts by up to 43-fold and 120-fold, respectively; (2) the ribulose-1,5-bisphosphate carboxylase/oxygenase activity of the symbiont is sufficient to account for its sulfide- or thiosulfate-stimulated CO2 incorporation; (3) the symbiont's molar growth yield on thiosulfate, as judged by CO2 incorporation, is indistinguishable from that of free-living chemoautotrophs. Due to the high protein-degrading activity of B. thermophilus gill lysate, it is also suggested that host lysis of symbionts plays a more important role in the nutrition of the vent mussel than in R. pachyptila or C. magnifica, for which no comparable protein-degrading activity was found. 相似文献
73.
Distribution of diatoms in the surficial sediments of the Mangyung-Dongjin tidal flat,west coast of Korea (Eastern Yellow Sea) 总被引:1,自引:0,他引:1
The relationship between the distribution of benthic diatoms and sediment characteristics of the Mangyung-Dongjin tidal flat on the west coast of Korea was investigated during June and July 1988. Diatoms were collected from the upper 5 mm of sediments at 60 sites along eight transect lines running perpendicular to the shore line. Of the 371 taxa encountered in the study area, 88% were pennate diatoms. Genera represented by the greatest number of species were Navicula, Nitzschia, Amphora, Cocconeis, Fragilaria and Achnanthes. The most abundant species were Paralia sulcata, Navicula sp. #1, N. arenaria and Cymatosira belgica; all were broadly distributed across the tidal flats. The 60 sites could be assigned to eight clusters with respect to similarity in species composition. Discriminant analysis showed that separation cluster was primarily related to the mean grain size of the sediment. The species could not be separated into groups based on similarities in occurrence; a high degree of spatial overlap was observed. The preferences of the more abundant species for grain size were, therefore, analysed by plotting numerical abundance against mean grain size. There were at least four patterns: species groups could be associated with finegrained sediments, those of intermediate size and coarser sediments and the last group showed no discernible pattern. 相似文献
74.
Processes involved in uptake and release of nitrogen dioxide from soil and building stones into the atmosphere 总被引:1,自引:0,他引:1
Atmospheric NO2 was taken up by samples of various soils and building stones. The NO2 uptake rate constants were highest in soil samples taken during the summer months. However, the NO2 uptake rate constants of the soils and building stones were not significantly correlated with any of the following variables: moisture, pH, ammonium, nitrite, or nitrate. NO2 uptake by soil and stone was not abolished by autoclaving indicating a chemical uptake process. NO2 uptake by acidic and air-dry soils and stones resulted in nearly stoichiometric reduction of NO2 to NO. This reduction was enhanced by the addition of ferrous iron and was further enhanced by incubation under 1 ppmv SO2. The results suggest that NO2 reduction may be coupled to oxidation of ferrous to ferric iron which may be reduced again by atmospheric SO2 thus regenerating the ferrous iron content of the soil or stone. Conversion of NO2 to NO was not observed in neutral or/and moist soils and stones. NO2 was also taken up by purified and sterilized quartz sand moistend with water. This uptake was enhanced by addition of humic material but not by addition of bacteria which both had been extracted from genuine soil. Under most conditions, only uptake but no release of NO2 was observed. However, NO2 was released in air-dry soils that were heated to 45–65°C, or in ammonium-fertilized soil or stone that was drying up at room temperature. Under the latter conditions mimicking field practice, the NO2 release reached rates that were similar to the NO release rates. 相似文献
75.
Christophe Pélabon Jean-Michel Gaillard Anne Loison Christine Portier 《Behavioral ecology and sociobiology》1995,37(5):311-319
We examined data on sex-specific differences in neonatal weight, litter size and adult female body weight in 32 populations of polygynous ungulates of 18 different species to test for the existence of a trade-off between sex-biased maternal care and the total amount of maternal expenditure. This corresponds to an extension of the hypothesis of Byers and Moodie (1990) that sex-biased maternal care is limited by a high level of maternal expenditure. We did not find any relationship between sex-biased care and two measures of total maternal expenditure. We highlighted high intraspecific variability in sex-biased care and very low intraspecific variability in total maternal expenditure. Even when this between-population variability in sex-biased care was accounted for, no relationship between sex-biased maternal care and maternal expenditure was detected. Apart from difficulties in finding suitable measures for both variables, two other reasons may account for the lack of a relationship between sex-biased maternal care and total maternal expenditure. Firstly, male offspring seem to be more affected than female offspring by harsh environmental conditions. This may lead to the variation observed in the extent of sex-specific differences in birth weight within a single species. If we assume that for a given maternal expenditure reproductive costs incurred by mothers are highest during harsh conditions, this could indicate the existence of a trade-off between sex-biased maternal care and maternal expenditure at the intra-specific level, thereby supporting the Byers and Moodie hypothesis. Secondly, polygyny is only a poor predictor of sex-biased care and factors such as compensatory growth or extended periods of growth may be expected to modify predictions for different species. Thus, environmental conditions and relative effects of maternal care on male and female lifetime reproductive success are better predictors of sex-biased care than total maternal expenditure.Communicated by P.M. Kappeler 相似文献
76.
D. K. A. Barnes 《Marine Biology》1995,121(3):555-563
Photographs were taken every 0.5 m along three transects of 5.5 m length on shallow rock faces at Signy Island, Antarctica, during the austral summer of 1991/1992. The percentage cover of substratum ranged from 0 to 100% and the colonising communities included representatives of ten phyla. The zone from mean low-water neap level to 1.5 m depth was mostly devoid of organisms as a result of the seasonal formation of the encrusting ice foot. Coralline and macroalgae dominated from 2 to 3 m, and animal groups from 3.5 to 5.5 m. Bryozoans, and to a lesser extent sponges, were the most abundant animal phyla. Within the bryozoans a succession of colonisation of different species was observed, the most abundant two of which occupied >80% of substratum in places. Substratum type seemed to be the main factor influencing community development in the shallow sublittoral at Signy Island, although ice impact prevents community development in the top 1.5 m and limits it over the rest of the transect down to 5.5 m. Depth and profile of substratum also influenced communities within this depth range (particularly taxonomic composition). 相似文献
77.
Mark Walker W. Douglass Shaw Marnee Benson 《Journal of the American Water Resources Association》2006,42(5):1363-1370
ABSTRACT: Churchill County, Nevada, has approximately 23,000 residents, among whom an estimated 13,500 relied on private wells for water supply in 2002. This study examined exposure to arsenic in water supplies among residents with private domestic wells and factors related to householder choice to consume tap water. It compared opinions and concerns about water quality with consumption habits and observed concentrations from tap water samples. The results from 351 households indicated that a majority (75 percent) of respondents consumed tap water and that a minority (38 percent) applied treatment. Approximately 66 percent of those who consumed tap water were exposed to concentrations of arsenic that exceeded 10 ppb. Water consumption was related to application of treatment. Among 98 respondents who were not at all concerned about the health effects of aqueous arsenic, 59 (60 percent) reported consuming tap water with concentrations of arsenic exceeding 10 ppb. Conversely, among 86 respondents who were highly concerned about arsenic, 33 (37 percent) consumed tap water with concentrations of arsenic exceeding 10 ppb. Results from a national sampling effort showed that 620 of 5,304 private wells sampled (11.7 percent) had arsenic concentrations above 10 ppb. The paradox of awareness of arsenic in water supplies coupled with consumption of aqueous arsenic in concentrations greater than 10 ppb may be common in other parts of the nation. Enhanced educational efforts, especially related to tap water sampling and explanations of efficacy of available treatment, may be useful means of reducing exposure through private water supplies. 相似文献
78.
The most widely used method for fetocide in late termination of pregnancy for fetal abnormalities (TOPFA) consists of injecting of potassium chloride (KCl) into the fetal heart and is likely to be painful after 22 weeks of gestation. We studied ten consecutive women undergoing TOPFA between 22 and 38 weeks. This technique for fetocide consisted of a single umbilical vein puncture under ultrasound guidance with injections of sufentanil 5 µg followed by KCl 2 g. No electrocardiographic modifications could be observed and maternal plasma potassium levels did not show any significant variation throughout the procedure. Fetal umbilical phlebotomy for fetal analgesia followed by fetocide therefore appears to be a safe procedure for the mother and allows the fetus to die without pain when late termination of pregnancy (TOP) is indicated. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
79.
Fragile X syndrome is the most common cause of familial mental retardation. The most common mutation is expansion of a triplet (CGG)n repeat in the 5′ untranslated region of the FMR1 gene on Xq27.3. The expansion is refractory to PCR due to preferential amplification of the smaller allele in heterozygous cells and the high GC content of the repeat and surrounding sequences. Direct detection of the normal parental alleles in preimplantation embryos has been used for preimplantation genetic diagnosis (PGD) of this disorder. However, this approach is only suitable for approximately 63% of couples due to the heterozygosity of the repeat in the normal population. As an alternative we investigated the use of polymorphic markers flanking the mutation to track the normal and premutation carrying maternal chromosomes in preimplantation embryos. Using a panel of 11 polymorphisms, six (CA)n repeats and five single nucleotide polymorphisms, diagnosis was developed for 90% of referred couples. Multiplex amplification of informative markers was tested in 300 single buccal cells from interested couples with efficiency and allele drop out (ADO) rates ranging from 69% to 96% and 6% to 18%, respectively. Use of this approach is accurate and applicable to a larger number of patients at risk of transmitting fragile X to their offspring. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
80.