全文获取类型
收费全文 | 14399篇 |
免费 | 32篇 |
国内免费 | 172篇 |
专业分类
安全科学 | 97篇 |
废物处理 | 1036篇 |
环保管理 | 1631篇 |
综合类 | 1609篇 |
基础理论 | 4341篇 |
环境理论 | 2篇 |
污染及防治 | 2893篇 |
评价与监测 | 1306篇 |
社会与环境 | 1675篇 |
灾害及防治 | 13篇 |
出版年
2023年 | 19篇 |
2022年 | 69篇 |
2021年 | 40篇 |
2020年 | 26篇 |
2019年 | 38篇 |
2018年 | 1714篇 |
2017年 | 1552篇 |
2016年 | 1337篇 |
2015年 | 215篇 |
2014年 | 102篇 |
2013年 | 275篇 |
2012年 | 588篇 |
2011年 | 1632篇 |
2010年 | 973篇 |
2009年 | 861篇 |
2008年 | 1203篇 |
2007年 | 1631篇 |
2006年 | 143篇 |
2005年 | 214篇 |
2004年 | 189篇 |
2003年 | 277篇 |
2002年 | 299篇 |
2001年 | 260篇 |
2000年 | 159篇 |
1999年 | 76篇 |
1998年 | 65篇 |
1997年 | 48篇 |
1996年 | 34篇 |
1995年 | 41篇 |
1994年 | 42篇 |
1993年 | 41篇 |
1992年 | 30篇 |
1991年 | 35篇 |
1990年 | 27篇 |
1989年 | 32篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 36篇 |
1983年 | 31篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1975年 | 12篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Spatial and seasonal distribution of nitrogen in marsh soils of a typical floodplain wetland in Northeast China 总被引:3,自引:0,他引:3
Bai J Wang Q Deng W Gao H Tao W Xiao R 《Environmental monitoring and assessment》2012,184(3):1253-1263
Horizontal and profile distributions of nitrogen in marsh soils in different seasons were studied in a typical site within
the Erbaifangzi wetland in Northeast China. Results showed that there was higher spatial heterogeneity for nitrate nitrogen
(NO3--_{3}^{-}-N) and ammonium nitrogen (NH4+_{4}^{+}–N), as well as available nitrogen (AN), in surface soils in July compared to that in September. Relative to July, the mean
nitrogen contents in surface soils were slightly higher in September; however, in November, soils contained significantly
lower NO3--_{3}^{-}-N and NH4+_{4}^{+}–N, higher AN, organic nitrogen (Org-N), and total nitrogen (TN). Except for mineral nitrogen, no significant differences
were observed between Org-N and TN contents in September and November. Nitrogen contents generally declined exponentially
with depth along soil profiles in three sampling dates (July, September, and November), except for a significant accumulation
peak of NO3--_{3}^{-}-N at the 20–30 cm depth in September. However, NH4+_{4}^{+}–N contents showed a vertical alternation of “increasing and decreasing” in both July and September, while nearly kept constant
with depth in November. The depth ranking of nitrogen showed the shallowest distribution for AN, followed by Org-N and TN,
while deeper distributions for NO3--_{3}^{-}-N and NH4+_{4}^{+}–N. TN, Org-N, and AN were significantly correlated with soil organic matter and total phosphorus. Soil pH values were significantly
correlated with TN and AN contents in surface soils. Clay contents showed significant correlations with nitrogen contents
except for NO3--_{3}^{-}-N in surface soils and NH4+_{4}^{+}–N in profile soils. However, soil moisture was not significantly correlated with nitrogen contents among all soil samples. 相似文献
992.
The aim of the current study was to investigate the potential of an aquatic plant, the water hyacinth (Eichhornia crassipes) devoid rhizospheric bacteria, to reduce naphthalene (a polyaromatic hydrocarbon) present in wastewater and wetlands.The capability of sterile water hyacinth plants to remove naphthalene from water and wastewater was studied in batch systems. Water hyacinths enhance the removal of pollutants through their consumption as nutrients and also through microbial activity of their rhizospheric bacteria.Experimental kinetics of naphthalene removal by water hyacinth coupled with natural rhizospheric bacteria was 100% after 9 d. Plants, decoupled of rhizospheric bacteria, reduced naphthalene concentration up to 45% during 7 d. Additionally, naphthalene uptake by water hyacinth revealed a biphasic behavior: a rapid first phase completed after 2.5 h, and a second, considerably slower rate, phase (2.5-225 h). In conclusion, water hyacinth devoid rhizospheric bacteria reduced significantly naphthalene concentration in water, revealing a considerable plant contribution in the biodegradation process of this pollutant. 相似文献
993.
Suciu NA Ferrari T Ferrari F Trevisan M Capri E 《Environmental science and pollution research international》2012,19(4):1229-1236
Purpose
Many reports on purification of water containing pesticides are based on studies using unformulated active ingredients. However, most commercial formulations contain additives/adjuvants or are manufactured using microencapsulation which may influence the purification process. Therefore, the main objective of this work was to develop and test a pilot scheme for decontaminating water containing pesticides formulated with antifoaming/defoaming agents. 相似文献994.
The current state of the ecology of the impact regions is outlined. It is argued that the complex of ecosystems situated around
a point polluter (an impact region) is an appropriate model for solving several fundamental and applied ecological problems
related to the exploration of strong external impacts on biota. Typical methodological errors resulting from insufficient
attention to specific features of passive experiments are analysed, and ways to avoid them are proposed. The principles of
spatial arrangements of study sites within the impact region and of the selection of experimental and evaluation units are
discussed. 相似文献
995.
Chlorinated paraffins (CPs) are straight chain hydrocarbons that are produced as complex mixtures and are used as flame retardants
and paint additives. These mixtures are extremely difficult to characterize using conventional chromatographic methods, as
conventional gas chromatography results in unresolved complex chromatograms that preclude the identification and quantification
of individual congeners or any reasonable assessment of the average carbon chain length. Carbon chain length is an important
parameter for assessing physical properties and the toxicity of these materials. We have modified and improved a previously
published gas chromatography–flame ionization detector method that uses Pd catalyst held in the gas chromatograph injector
to simultaneously dechlorinate the CPs and separate the resulting alkanes. In addition, we have adapted this method to gas
chromatography–mass spectrometry. Dehalogenation of other compounds was also studied with this system to investigate potential
application to other complex halogenated mixtures. 相似文献
996.
Voss KA Pohlman A Viswanathan S Gibson D Purohit J 《Environmental monitoring and assessment》2012,184(3):1603-1616
Environmental agencies across the United States have searched for adequate methods to assess anthropogenic impacts on the
environment. Biological assessments, which compare the taxonomic composition of an aquatic assemblage to relevant biocriteria,
have surfaced as an effective method to assess the ecological integrity of US waterbodies. In this study, bioassessment data
were collected and analyzed in conjunction with physical habitat and chemical stressor data for streams and rivers within
the San Diego basin from 1998 through 2005. Physical stressors such as sediment loading, riparian destruction, and in-stream
habitat homogenization affect many locations in the region. However, physical habitat measures alone were found to frequently
overestimate the biological integrity of streams in the region. Many sites within the San Diego Basin, although unaffected
by physical stressors, continue to exhibit low biological integrity scores. Sites with low biological integrity tend to possess
higher specific conductance and salinity compared to sites with high biological integrity. We suggest that one possible reason
for these differences is the source water used for municipal purposes. 相似文献
997.
Sexual cannibalism can occur before, during or after mating. Relatively few experimental studies have examined why there is
variation in the timing of sexual cannibalism. We examined the latency and number of attacks required for female spiders to
capture male spiders pre- vs. postcopulation. We also examined the effects of female mating status and hunger level on the
occurrence of pre- and postcopulatory cannibalism, which reflects the contribution of both relative capture success and female
motivation to cannibalize males. Precopulatory cannibalism occurred after a shorter interval and required fewer chases and
physical interactions for the female to successfully capture the male than was the case for postcopulatory cannibalism. Virgin
females were more likely to engage in postcopulatory rather than precopulatory cannibalism and mated females vice versa. Those
virgin females that did engage in precopulatory cannibalism had significantly lower body condition than virgin females engaging
in postcopulatory cannibalism. While precopulatory cannibalism occurred more quickly and required fewer attacks by females,
it comes at a potential cost of not mating with males. Hence, females are more likely to engage in precopulatory cannibalism
if they have already mated or, if virgins, if they have low body condition. These results indicate that the decision of when
to cannibalize males is dynamic and depends upon the relative value of a male as a mate versus a meal. 相似文献
998.
The Environmental Protection Agency (EPA) has made available on the worldwide web a systematic stream stressor identification
procedure, the “Causal Analysis/Diagnosis Decision Information System” or CADDIS. We report here the results of a survey of
regulators and scientists in 11 states who use CADDIS or another stressor identification procedure in their work. The 13 survey
questions address guidelines as to what impairment scenarios to approach with stressor identification, what information is
needed to perform stressor identification, and what the stakeholder role is in performing stressor identification. At the
time of this survey (the summer of 2009), the EPA CADDIS website was less commonly used among the state regulators surveyed
than the published EPA stressor identification document on which it is based. The respondents generally find the EPA stressor
identification procedure useful and capable of being adapted to their individual needs. Survey respondents all use stressor
identification in their Total Maximum Daily Load work, but also in a wide variety of other applications. All the “types of
evidence” included in the CADDIS stressor identification procedure are used by the practitioners surveyed with the exception
of the results of ecological simulation models. While the CADDIS documentation encourages the involvement of stakeholders
in stressor identification, most respondents do not assemble stakeholder teams of local officials and citizens to participate
in stressor analyses. 相似文献
999.
Monavari SM Omrani GA Karbassi A Raof FF 《Environmental monitoring and assessment》2012,184(4):1841-1846
Environment problems associated with the generation of waste are part of societal changes where households play an important
role. These societal changes influence the size, structure and characteristic of given households. For the effective planning
of solid-waste handling infrastructure, it is essential to know the quantity of waste generation and its composition. This
paper presents the findings of a study carried out in an urban municipal area in Iran to determine the household solid-waste
generation rate and waste composition based on field surveys and to determine the related socioeconomic parameters. The dependent
variables were waste generation and composition, and independent variables were family size, family employment, age, number
of room and education. Over 400 sample households were selected for the study using a stratified random sampling methodology
and from five different socioeconomic groups. Waste collected from all groups of households were segregated and weighted.
Waste generation rate was 5.4 kg/household/day. Household solid waste comprised of ten categories of wastes and with the largest
component (76.9%). The generation and composition of household solid waste were correlated with family size, education level
and households income. This paper adequately suggests new insights concerning the role of socioeconomic parameters in affecting
the generation of household waste. 相似文献
1000.
Bouo FX Kouamé JK Tchétché Y Kré RN Moussé ML Assamoi P Cautenet S Cautenet G 《Chemosphere》2011,84(11):1617-1629
The purpose of this paper is to study the redistribution of chemical species (OH, HO2, H2O2, HNO3 and H2SO4) over West Africa, where the cloud cover is ubiquitously present, and where deep convection often develops. In this area, because of these cloud systems, chemical species are redistributed by the ascending and descending flow, or leached if they are soluble. So, we carry out a mesoscale study using the Regional Atmospheric Modelling System (RAMS) coupled to a code of gas and aqueous chemistry (RAMS_Chemistry). It takes into account all processes under mesh. We examine several cases following the period (November and July), with inputs emissions (anthropogenic, biogenic and biomass burning). The radicals OH and HO2 are an indicator of possibilities for chemical activity. They characterize the oxidizing power of the atmosphere and are very strong oxidants. The acids HNO3 and H2SO4 are interesting in their transformation into nitrates and sulfates in precipitation. In November, when photochemistry is active during an event of biomass burning, concentrations of chemical species are higher than those of November in the absence of biomass burning. The concentrations of nitric acid double and sulfuric acid increases 70 times. In addition, the concentrations are even lower in July if there is a deep convection. Compared to measures of the African Monsoon Multidisciplinary Analysis (AMMA), the results and observations of radicals OH and HO2 are the same order of magnitude. Emissions from biomass burning increase the concentrations of acid and peroxide, and a deep convection cloud allows the solubility and the washing out of species, reducing their concentration. Rainfalls play a major role in solubility and washing out acids, peroxides and radicals in this region. 相似文献