全文获取类型
收费全文 | 30027篇 |
免费 | 315篇 |
国内免费 | 203篇 |
专业分类
安全科学 | 798篇 |
废物处理 | 1263篇 |
环保管理 | 4101篇 |
综合类 | 5074篇 |
基础理论 | 8305篇 |
环境理论 | 17篇 |
污染及防治 | 7561篇 |
评价与监测 | 1859篇 |
社会与环境 | 1358篇 |
灾害及防治 | 209篇 |
出版年
2022年 | 209篇 |
2021年 | 221篇 |
2019年 | 208篇 |
2018年 | 374篇 |
2017年 | 369篇 |
2016年 | 588篇 |
2015年 | 464篇 |
2014年 | 677篇 |
2013年 | 2323篇 |
2012年 | 872篇 |
2011年 | 1216篇 |
2010年 | 1003篇 |
2009年 | 1054篇 |
2008年 | 1233篇 |
2007年 | 1268篇 |
2006年 | 1130篇 |
2005年 | 989篇 |
2004年 | 921篇 |
2003年 | 918篇 |
2002年 | 880篇 |
2001年 | 1120篇 |
2000年 | 841篇 |
1999年 | 492篇 |
1998年 | 364篇 |
1997年 | 402篇 |
1996年 | 415篇 |
1995年 | 491篇 |
1994年 | 439篇 |
1993年 | 407篇 |
1992年 | 380篇 |
1991年 | 417篇 |
1990年 | 411篇 |
1989年 | 385篇 |
1988年 | 339篇 |
1987年 | 330篇 |
1986年 | 307篇 |
1985年 | 273篇 |
1984年 | 338篇 |
1983年 | 299篇 |
1982年 | 357篇 |
1981年 | 303篇 |
1980年 | 257篇 |
1979年 | 281篇 |
1978年 | 245篇 |
1977年 | 218篇 |
1976年 | 188篇 |
1975年 | 204篇 |
1974年 | 205篇 |
1973年 | 217篇 |
1972年 | 199篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
11.
12.
13.
Understanding implications of consumer behavior for wildlife farming and sustainable wildlife trade 下载免费PDF全文
A. Nuno J. M. Blumenthal T. J. Austin J. Bothwell G. Ebanks‐Petrie B. J. Godley A. C. Broderick 《Conservation biology》2018,32(2):390-400
Unsustainable wildlife trade affects biodiversity and the livelihoods of communities dependent upon those resources. Wildlife farming has been proposed to promote sustainable trade, but characterizing markets and understanding consumer behavior remain neglected but essential steps in the design and evaluation of such operations. We used sea turtle trade in the Cayman Islands, where turtles have been farm raised for human consumption for almost 50 years, as a case study to explore consumer preferences toward wild‐sourced (illegal) and farmed (legal) products and potential conservation implications. Combining methods innovatively (including indirect questioning and choice experiments), we conducted a nationwide trade assessment through in‐person interviews from September to December 2014. Households were randomly selected using disproportionate stratified sampling, and responses were weighted based on district population size. We approached 597 individuals, of which 37 (6.2%) refused to participate. Although 30% of households had consumed turtle in the previous 12 months, the purchase and consumption of wild products was rare (e.g., 64–742 resident households consumed wild turtle meat [i.e., 0.3–3.5% of households] but represented a large threat to wild turtles in the area due to their reduced populations). Differences among groups of consumers were marked, as identified through choice experiments, and price and source of product played important roles in their decisions. Despite the long‐term practice of farming turtles, 13.5% of consumers showed a strong preference for wild products, which demonstrates the limitations of wildlife farming as a single tool for sustainable wildlife trade. By using a combination of indirect questioning, choice experiments, and sales data to investigate demand for wildlife products, we obtained insights about consumer behavior that can be used to develop conservation‐demand‐focused initiatives. Lack of data from long‐term social–ecological assessments hinders the evaluation of and learning from wildlife farming. This information is key to understanding under which conditions different interventions (e.g., bans, wildlife farming, social marketing) are likely to succeed. 相似文献
14.
15.
16.
Maheswari C. Ramya A. S. Priya B. Meenakshi Sudhahar S. Prabhu Raj B. Lokesh B. Ramani G. 《Journal of Material Cycles and Waste Management》2021,23(6):2255-2265
Journal of Material Cycles and Waste Management - The present research work focused on fabricating Biodegradable Plate (BD plate) composed of rice husk ash, bagasse and corn starch which is... 相似文献
17.
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
18.
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
19.
20.
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