全文获取类型
收费全文 | 28293篇 |
免费 | 321篇 |
国内免费 | 199篇 |
专业分类
安全科学 | 763篇 |
废物处理 | 1245篇 |
环保管理 | 3722篇 |
综合类 | 4339篇 |
基础理论 | 7910篇 |
环境理论 | 12篇 |
污染及防治 | 7399篇 |
评价与监测 | 1838篇 |
社会与环境 | 1412篇 |
灾害及防治 | 173篇 |
出版年
2022年 | 212篇 |
2021年 | 198篇 |
2019年 | 185篇 |
2018年 | 355篇 |
2017年 | 367篇 |
2016年 | 587篇 |
2015年 | 436篇 |
2014年 | 650篇 |
2013年 | 2204篇 |
2012年 | 818篇 |
2011年 | 1160篇 |
2010年 | 959篇 |
2009年 | 968篇 |
2008年 | 1185篇 |
2007年 | 1233篇 |
2006年 | 1107篇 |
2005年 | 939篇 |
2004年 | 900篇 |
2003年 | 930篇 |
2002年 | 858篇 |
2001年 | 1142篇 |
2000年 | 820篇 |
1999年 | 477篇 |
1998年 | 359篇 |
1997年 | 376篇 |
1996年 | 393篇 |
1995年 | 465篇 |
1994年 | 398篇 |
1993年 | 353篇 |
1992年 | 370篇 |
1991年 | 371篇 |
1990年 | 392篇 |
1989年 | 370篇 |
1988年 | 324篇 |
1987年 | 307篇 |
1986年 | 270篇 |
1985年 | 281篇 |
1984年 | 322篇 |
1983年 | 279篇 |
1982年 | 334篇 |
1981年 | 276篇 |
1980年 | 232篇 |
1979年 | 255篇 |
1978年 | 217篇 |
1977年 | 190篇 |
1976年 | 176篇 |
1975年 | 187篇 |
1974年 | 200篇 |
1973年 | 196篇 |
1972年 | 179篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Carly E. Federman Durelle T. Scott Erich T. Hester 《Journal of the American Water Resources Association》2023,59(1):29-48
River flooding impacts human life and infrastructure, yet provides habitat and ecosystem services. Traditional flood control (e.g., levees, dams) reduces habitat and ecosystem services, and exacerbates flooding elsewhere. Floodplain restoration (i.e., bankfull floodplain reconnection and Stage 0) can also provide flood management, but has not been sufficiently evaluated for small frequent storms. We used 1D unsteady Hydrologic Engineering Center's River Analysis System to simulate small storms in a 5 km-long, second-order generic stream from the Chesapeake Bay watershed, and varied % channel restored (starting at the upstream end), restoration location, restoration bank height (distinguishes bankfull from Stage 0 restoration), and floodplain width/Manning's n. Stream restoration decreased (attenuated) peak flow up to 37% and increased floodplain exchange by up to 46%. Floodplain width and % channel restored had the largest impact on flood attenuation. The incremental effects of new restoration projects on flood attenuation were greatest when little prior restoration had occurred. By contrast, incremental effects on floodplain exchange were greatest in the presence of substantial prior restoration, setting up a tradeoff. A similar tradeoff was revealed between attenuation and exchange for project location, but not bank height or floodplain width. In particular, attenuation and exchange were always greater for Stage 0 than for bankfull floodplain restoration. Stage 0 thus may counteract human impacts such as urbanization. 相似文献
12.
13.
14.
15.
Chad L. Hewitt Marnie L. Campbell Ronald E. Thresher Richard B. Martin Sue Boyd Brian F. Cohen David R. Currie Martin F. Gomon Michael J. Keough John A. Lewis Matthew M. Lockett Nicole Mays Matthew A. McArthur Tim D. O'Hara Gary C. B. Poore D. Jeff Ross Melissa J. Storey Jeanette E. Watson Robin S. Wilson 《Marine Biology》2004,144(1):183-202
Port Phillip Bay (PPB) is a large (1,930 km2), temperate embayment in southern Victoria, Australia. Extensive bay-wide surveys of PPB have occurred since 1840. In 1995/1996 the Commonwealth Scientific and Industrial Research Organization (CSIRO) Centre for Research on Introduced Marine Pests (CRIMP) undertook an intensive evaluation of the region with the aims of developing a comprehensive species list of native and introduced biota and contrasting previous bay-wide assessments with a current field survey in order to detect new incursions and discern alterations to native communities. Two methods were used to meet these aims: a re-evaluation of regional museum collections and published research in PPB to identify and determine the timing of introductions; and field surveys for benthic (infauna, epifauna and encrusting) organisms between September 1995 to March 1996. One hundred and sixty introduced (99) and cryptogenic (61) species were identified representing over 13% of the recorded species of PPB. As expected, the majority of these are concentrated around the shipping ports of Geelong and Melbourne. Invasions within PPB appear to be increasing, possibly due to an increase in modern shipping traffic and an increase in aquaculture (historically associated with incidental introductions); however the records of extensive biological surveys suggest that this may, in part, be an artefact of sampling effort. In contrast to Northern Hemisphere studies, PPB (and Southern Hemisphere introductions in general) have significantly different suites of successfully invading taxa. PPB is presented as one of the most invaded marine ecosystems in the Southern Hemisphere.Communicated by M.S. Johnson, Crawley 相似文献
16.
17.
A fragment constant QSAR model for evaluating the EC50 values of organic chemicals to Daphnia magna.
Shu Tao Xiaohuan Xi Fuliu Xu Bengang Li Jun Cao R Dawson 《Environmental pollution (Barking, Essex : 1987)》2002,116(1):57-64
The quantitative relationship between the median effective concentration (EC50) of organic chemicals to Daphnia magna and the number of molecular fragments was investigated based on experimental EC50 values for 217 chemicals derived from the literature. A fragment constant model was developed based on a multivariate linear regression between the number of fragments and the logarithmically transformed reciprocal values of EC50. Functional correction factors were introduced into the model. The model was verified using an independent set of randomly selected data. The mean residual of the final model was 0.4 log-units. The robustness of the model was discussed based on the results of three jackknife tests. 相似文献
18.
A transition zone in the otoliths of orange roughy (Hoplostethus atlanticus) is described where annulus width decreases markedly. For fish sampled at spawning time, the relationship between gonad stage
and the presence or absence of a transition zone is consistent with the hypothesis that this zone marks the onset of maturity,
if allowance is made for some error in gonad staging and identification of the zone. Another data set from a non-spawning
area after the spawning season is not consistent with the hypothesis. However, these latter data are considered less reliable
because of the small size of the fish in the sample and difficulties in determining, outside the spawning season, whether
a fish has been reproductively active. This hypothesis was used to provide estimates of the median age (30 yr) and length
(31 cm) at the onset of maturity for the Chatham Rise, New Zealand population. These estimates are unaffected by the biases
associated with the usual ogive method of estimation.
Received: 27 June 1997 / Accepted: 1 July 1997 相似文献
19.
Frank Eierdanz Joseph Alcamo Lilibeth Acosta-Michlik Dörthe Krömker Dennis Tänzler 《Regional Environmental Change》2008,8(4):197-205
This paper presents the technical aspects of a new methodology for assessing the susceptibility of society to drought. The
methodology consists of a combination of inference modelling and fuzzy logic applications. Four steps are followed: (1) model
input variables are selected—these variables reflect the main factors influencing susceptibility in a social group, population
or region, (2) fuzzification—the uncertainties of the input variables are made explicit by representing them as ‘fuzzy membership
functions’, (3) inference modelling—the input variables are used to construct a model made up of linguistic rules, and (4)
defuzzification—results from the model in linguistic form are translated into numerical form, also through the use of fuzzy
membership functions. The disadvantages and advantages of this methodology became apparent when it was applied to the assessment
of susceptibility from three disciplinary perspectives: Disadvantages include the difficulty in validating results and the
subjectivity involved with specifying fuzzy membership functions and the rules of the inference model. Advantages of the methodology
are its transparency, because all model assumptions have to be made explicit in the form of inference rules; its flexibility,
in that informal and expert knowledge can be incorporated through ‘fuzzy membership functions’ and through the rules in the
inference model; and its versatility, since numerical data can be converted to linguistic statements and vice versa through
the procedures of ‘fuzzification’ and ‘defuzzification’. 相似文献
20.