全文获取类型
收费全文 | 44247篇 |
免费 | 460篇 |
国内免费 | 365篇 |
专业分类
安全科学 | 1355篇 |
废物处理 | 2065篇 |
环保管理 | 5534篇 |
综合类 | 6877篇 |
基础理论 | 11609篇 |
环境理论 | 17篇 |
污染及防治 | 11340篇 |
评价与监测 | 3157篇 |
社会与环境 | 2847篇 |
灾害及防治 | 271篇 |
出版年
2023年 | 213篇 |
2022年 | 446篇 |
2021年 | 494篇 |
2020年 | 319篇 |
2019年 | 382篇 |
2018年 | 724篇 |
2017年 | 790篇 |
2016年 | 1133篇 |
2015年 | 854篇 |
2014年 | 1336篇 |
2013年 | 3632篇 |
2012年 | 1567篇 |
2011年 | 2057篇 |
2010年 | 1667篇 |
2009年 | 1679篇 |
2008年 | 2064篇 |
2007年 | 2010篇 |
2006年 | 1799篇 |
2005年 | 1541篇 |
2004年 | 1507篇 |
2003年 | 1436篇 |
2002年 | 1336篇 |
2001年 | 1577篇 |
2000年 | 1113篇 |
1999年 | 691篇 |
1998年 | 490篇 |
1997年 | 535篇 |
1996年 | 529篇 |
1995年 | 648篇 |
1994年 | 567篇 |
1993年 | 468篇 |
1992年 | 513篇 |
1991年 | 494篇 |
1990年 | 482篇 |
1989年 | 466篇 |
1988年 | 405篇 |
1987年 | 361篇 |
1986年 | 378篇 |
1985年 | 369篇 |
1984年 | 381篇 |
1983年 | 367篇 |
1982年 | 368篇 |
1981年 | 321篇 |
1980年 | 266篇 |
1979年 | 285篇 |
1978年 | 248篇 |
1977年 | 229篇 |
1975年 | 211篇 |
1973年 | 241篇 |
1972年 | 211篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
41.
Quantitative methods have been applied to the study of floristic structure and diversity in Samarskaya Luka. The results show that Samarskaya Luka is a floristically heterogeneous area in which six elementary floras can be distinguished. This area has been assessed as a floristically autonomous formation, and its floristic representativeness was estimated. 相似文献
42.
Luo J Shukla R Adhikari A Reponen T Grinshpun SA Zhang Q LeMasters GK 《Journal of environmental monitoring : JEM》2006,8(9):955-962
A time series model was fitted to the pollen concentration data collected in the Greater Cincinnati area for the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS). A traditional time series analysis and temporal variogram approach were applied to the regularly spaced databases (collected in 2003) and irregularly spaced ones (collected in 2002), respectively. The aim was to evaluate the effect of the sampling frequency on the sampling precision in terms of inverse of standard error of the overall level of mean value across time. The presence of high autocorrelation in the data was confirmed and indicated some degree of temporal redundancy in the pollen concentration data. Therefore, it was suggested that sampling frequency could be reduced from once a day to once every several days without a major loss of sampling precision of the overall mean over time. Considering the trade-offs between sampling frequency and the possibility of sampling bias increasing with larger sampling interval, we recommend that the sampling interval should take values from 3 to 5 days for the pollen monitoring program, if the goal is to track the long-term average. 相似文献
43.
Kumar A Baroth A Soni I Bhatnagar P John PJ 《Environmental monitoring and assessment》2006,116(1-3):1-7
Anupgarh is the most fertile area of Rajasthan state where a variety of seasonal crops are grown. The availability of three
manmade canals has enhanced the agricultural activities in this area. The farmers use huge amounts of pesticides to increase
the crop productivity. Exposure of humans to these hazardous chemicals occurs directly in the fields and indirectly due to
consumption of contaminated diet, or by inhalation or by dermal contact. The organochlorine pesticides are reported to be
lipophilic and their presence in human milk and blood has been documented in different parts of the world. Blood and milk
samples were collected from lactating women who were divided into four groups on the basis of different living standards viz
residence area, dietary habits, working conditions and addiction to tobacco. The level of total organochlorine pesticides
in blood ranged from 3.319mg/L—6.253mg/L while in milk samples it ranged from 3.209Mdash;4.608 mg/L. The results are in concurrence
with the reports from other countries. 相似文献
44.
A new approach to Assess Atmospheric Nitrogen Deposition by Way of Standardized Exposition of mosses
A standardized method of moss exposition for assessing variations in nitrogen deposition was tested in the western part of
Germany. Six pleurocarpous moss species were transplanted to two sites differing in their deposition rates but being comparable
as to their climatic conditions. The mosses were exposed in standardized containers over a period of 12 months; the focus
of interest was the effect of N deposition on nitrogen content and on 15N natural abundance (δ15N-values). Within the first nine months only trends could be observed. However, after one year all species tested showed significantly
higher N concentrations at the highly polluted site. Besides, more negative δ15N-values possibly reflecting the higher ammonium input were detected at this site. Surprisingly, most of the plants though
being kept in plastic containers without a favourable substratum did not show any conspicuous deficiency symptoms. The potential
advantages of a standardized moss exposition for N monitoring purposes are discussed. It is concluded that the method presented
here can yield significant results in particular if the number of testing sites is increased. 相似文献
45.
Rhea DT Harper DD Farag AM Brumbaugh WG 《Environmental monitoring and assessment》2006,115(1-3):381-393
Portions of the Boulder River watershed contain elevated concentrations of arsenic, cadmium, copper, lead, and zinc in water, sediment, and biota. We measured concentrations of As, Cd, Cu, Pb, and Zn in biofilm and macroinvertebrates, and assessed macroinvertebrate assemblage and aquatic habitat with the objective of monitoring planned remediation efforts. Concentrations of metals were generally higher in downstream sites compared with upstream or reference sites, and two sites contained metal concentrations in macroinvertebrates greater than values reported to reduce health and survival of resident trout. Macroinvertebrate assemblage was correlated with metal concentrations in biofilm and macroinvertebrates. However, macroinvertebrate metrics were significantly correlated with a greater number of biofilm metals (8) than metals in invertebrates (4). Lead concentrations in biofilm appeared to have the most significant impact on macroinvertebrate assemblage. Metal concentrations in macroinvertebrates were directly proportional to concentrations in biofilm, indicating biofilm as a potential surrogate for monitoring metal impacts in aquatic systems. 相似文献
46.
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
47.
48.
49.
50.
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