全文获取类型
收费全文 | 25824篇 |
免费 | 4885篇 |
国内免费 | 26759篇 |
专业分类
安全科学 | 1668篇 |
废物处理 | 916篇 |
环保管理 | 3339篇 |
综合类 | 31861篇 |
基础理论 | 6494篇 |
环境理论 | 7篇 |
污染及防治 | 9343篇 |
评价与监测 | 2345篇 |
社会与环境 | 1094篇 |
灾害及防治 | 401篇 |
出版年
2023年 | 100篇 |
2022年 | 188篇 |
2021年 | 214篇 |
2020年 | 829篇 |
2019年 | 2001篇 |
2018年 | 2303篇 |
2017年 | 2263篇 |
2016年 | 2139篇 |
2015年 | 2515篇 |
2014年 | 3272篇 |
2013年 | 4317篇 |
2012年 | 3497篇 |
2011年 | 3264篇 |
2010年 | 2887篇 |
2009年 | 2936篇 |
2008年 | 2642篇 |
2007年 | 2720篇 |
2006年 | 2021篇 |
2005年 | 1584篇 |
2004年 | 1514篇 |
2003年 | 1239篇 |
2002年 | 1076篇 |
2001年 | 1216篇 |
2000年 | 1175篇 |
1999年 | 889篇 |
1998年 | 649篇 |
1997年 | 638篇 |
1996年 | 665篇 |
1995年 | 669篇 |
1994年 | 459篇 |
1993年 | 397篇 |
1992年 | 436篇 |
1991年 | 439篇 |
1990年 | 403篇 |
1989年 | 373篇 |
1988年 | 294篇 |
1987年 | 201篇 |
1986年 | 228篇 |
1985年 | 195篇 |
1984年 | 242篇 |
1983年 | 186篇 |
1982年 | 215篇 |
1981年 | 191篇 |
1980年 | 131篇 |
1979年 | 150篇 |
1978年 | 96篇 |
1977年 | 98篇 |
1975年 | 88篇 |
1974年 | 93篇 |
1972年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
32.
33.
多波长法用于减小浊度对水源水中甲醛测定结果的影响 总被引:1,自引:1,他引:0
比较了减小水样浊度对样品结果影响的各种方法,包括过滤法、双波长法、三波长法,3种方法均基于乙酰丙酮分光光度法,测定波长均为414 nm。结果表明,以480 nm为参比波长的双波长法所得方法检出限为0.027 mg/L,采用470 nm与360 nm、460 nm与370 nm、450 nm与380 nm 3对参比波长的三波长法测得方法检出限为0.025~0.028 mg/L,这些方法用于检测0.100 mg/L标准点样品时,检测结果 RSD介于8.0%~8.6%。双波长法适合低浊度样品的直接分析,而浊度较高或双波长法测得结果大于方法检出限时,应采用三波长法进行定量分析,他们的使用有助于提高方法的准确度及减少工作量。用于地表水样品分析时,0.200、0.400 mg/L加标样品的回收率介于90.3%~101%,对应RSD介于0.0%~4.2%。 相似文献
34.
Under what conditions do critical events trigger large-scale public discussion and mobilisation, and can these lead to policy change? In a comparative study of nuclear energy policy after the Japanese Fukushima disaster in March 2011, a theory-development approach is adopted, mobilising data collected from national news agencies’ newswires, public surveys, legislation and parliamentary databases, and newspaper editorials in 12 established democracies between March 2011 and March 2013. The analysis suggests two main hypotheses that can guide future research: critical events are more likely to trigger policy change when intense (contentious) mobilisation from policy challengers aligns with the views of the general public, and is backed by major political allies; and critical events are more likely to trigger intense (contentious) mobilisation when policy challengers articulate their opposition around pre-existing policy debates on the issue and resort to pre-existing organisational and mobilisation resources. 相似文献
35.
Abstract: Introduction of artificial light into wildlife habitat represents a rapidly expanding form of human encroachment, particularly in coastal systems. Light pollution alters the behavior of sea turtles during nesting; therefore, long-wavelength lights—low-pressure sodium vapor and bug lights—that minimize impacts on turtles are required for beach lighting in Florida (U.S.A.). We investigated the effects of these two kinds of lights on the foraging behavior of Santa Rosa beach mice ( Peromyscus polionotus leucocephalus ). We compared patch use and giving-up densities of mice for experimental food patches established along a gradient of artificial light in the field. Mice exploited fewer food patches near both types of artificial light than in areas with little light and harvested fewer seeds within patches near bug lights. Our results show that artificial light affects the behavior of terrestrial species in coastal areas and that light pollution deserves greater consideration in conservation planning. 相似文献
36.
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
37.
38.
39.
40.
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