全文获取类型
收费全文 | 1360篇 |
免费 | 24篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 47篇 |
废物处理 | 53篇 |
环保管理 | 279篇 |
综合类 | 124篇 |
基础理论 | 392篇 |
环境理论 | 1篇 |
污染及防治 | 327篇 |
评价与监测 | 83篇 |
社会与环境 | 70篇 |
灾害及防治 | 11篇 |
出版年
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 16篇 |
2019年 | 12篇 |
2018年 | 25篇 |
2017年 | 12篇 |
2016年 | 44篇 |
2015年 | 30篇 |
2014年 | 34篇 |
2013年 | 125篇 |
2012年 | 35篇 |
2011年 | 67篇 |
2010年 | 48篇 |
2009年 | 60篇 |
2008年 | 56篇 |
2007年 | 71篇 |
2006年 | 57篇 |
2005年 | 52篇 |
2004年 | 40篇 |
2003年 | 44篇 |
2002年 | 45篇 |
2001年 | 39篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 18篇 |
1997年 | 20篇 |
1996年 | 20篇 |
1995年 | 34篇 |
1994年 | 19篇 |
1993年 | 20篇 |
1992年 | 13篇 |
1991年 | 25篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 25篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1971年 | 7篇 |
排序方式: 共有1387条查询结果,搜索用时 15 毫秒
921.
The objective of this study was to assess the effects of two brief training interventions to improve obstetricians' and midwives' explanations to patients of a routine prenatal screening test. Health professionals were randomly allocated to one of two intervention groups or a control group. Information-giving about the test and communication skills were assessed at baseline, post-training and 3-month follow-up from audiotaped consultations. Both intervention groups received a 1-h training session involving small group discussions focused around a video. In addition, one group received individual feedback on their baseline and post-training consultations. Twenty-six midwives and nine obstetricians completed the study according to the protocol. Changes between baseline and post-training, and between baseline and follow-up, were computed. Information-giving and communication skills improved significantly in subjects receiving training and feedback on their performance, with the greatest improvements occurring before feedback was given. Those receiving training without feedback significantly improved their communication skills and showed some improvement in information-giving. These results show that modest improvements in communication can be made with relatively brief training. Greater and more sustained improvements may be found if all staff were trained, and trained on a regular basis. 相似文献
922.
P. W. Glynn N. J. Gassman C. M. Eakin J. Cortes D. B. Smith H. M. Guzman 《Marine Biology》1991,109(3):355-368
Reproductive ecology of two major reef-building corals in the eastern Pacific [Pocillopora damicornis (Linnaeus) andPocillopora elegans Dana] was investigated between 1984 and 1990 in Costa Rica, Panama (Gulf of Chiriqui and Gulf of Panama), and the Galapagos Islands (Ecuador) following the 1982–83 El Niño disturbance. Mature spermatocytes and oocytes were found in both species and were usually present in the same polyp in nearly equal ratios. Numerous zooxanthellae were observed in mature, unfertilized oocytes. Although spawning in field populations was not observed, it is likely that both pocilloporids are simultaneous hermaphroditic spawners, as evidenced by the disappearance of mature gametes after full moon. This is in contrast with most known pocilloporid corals that brood and release planula larvae. Corals were reproductively most active in the thermally stable environments of Costa Rica and the Gulf of Chiriqui (Panama) where 32 to 90% of all colonies contained gametes. In the moderately varying thermal conditions in the Galapagos Islands, 16 to 40% of colonies contained gametes, and in the pronounced seasonal upwelling environment of the Pearl Islands (Panama) only 6 to 18% of colonies contained gametes. Year-round reproduction occurred in Costa Rica and the Gulf of Chiriqui, whereas reproduction was confined to warm periods in the seasonally varying environments of the Galapagos Islands and the Gulf of Panama. Pocilloporid corals in Costa Rica and the Gulf of Chiriqui demonstrated lunar spawning activity, with mature gametes present a few days before and after full moon. Some limited spawning may have occurred also at new moon. While frequent gamete maturation has been demonstrated in this study, the relatively low rates of larval recruitment occurring on eastern Pacific coral reefs disturbed by the 1982–83 El Niño suggest that the recovery of important frame-building corals could be greatly prolonged. 相似文献
923.
Diane R. Smith 《补救:环境净化治理成本、技术与工艺杂志》1995,5(3):131-142
After suits by the AFL-CIO and the Service Employees International Union demanding more worker protection, OSHA published new proposed asbestos regulations in 1990. Hearings were held in 1991. Everyone was very interested. Nothing happened for about three years. Then, just when everyone thought they had their “asbestos problems” figured out, along came the new October 11, 1994, asbestos rules. Look out building owners, property management companies, abatement contractors, and asbestos consultants—it's your turn to cry. 相似文献
924.
Orendovici T Skelly JM Ferdinand JA Savage JE Sanz MJ Smith GC 《Environmental pollution (Barking, Essex : 1987)》2003,125(1):31-40
Tropospheric ozone has been identified as the most important regional scale air pollutant across much of eastern United States of America and many areas of Mediterranean climes in southern Europe. Recent field surveys in the northeastern USA and in southeastern Spain have revealed many additional plant species that exhibit symptoms typical of ozone-induced injuries. Objectives of this study were to confirm ozone as the cause of the observed foliar symptoms, determine ozone induced exposure/response relationships, and identify possible bio-indicator species. Thirteen native species of northeastern USA and 27 native species of southeastern Spain were selected for study. Plant species were exposed to ozone within 16 CSTR chambers in a greenhouse during the summer seasons of 2000 and 2001; ozone exposures of 30, 60, 90, and 120 ppb were delivered for 7 h/day, 5 days/week. Results have confirmed that with few exceptions, symptoms observed in the field were induced by exposures to ambient ozone. Species differed significantly in terms of the exposures required for the initiation of visible symptoms and subsequent injury progression. 相似文献
925.
Mixtures of dense nonaqueous phase liquids (DNAPLs) trapped in the subsurface can act as long-term sources of contamination by dissolving into flowing groundwater. If the components have different solubilities then dissolution will alter the composition of the remaining DNAPL. We theorized that a multicomponent DNAPL pool may become mobile due to the natural dissolution process. In this study, we focused on two scenarios: (1) a DNAPL losing light component(s), with the potential for downward migration; and (2) a DNAPL losing dense component(s), with the potential for upward migration following transformation into a less dense than water nonaqueous phase liquid (LNAPL). We considered three binary mixtures of common groundwater contaminants: benzene and tetrachloroethylene (PCE), PCE and dichloromethane (DCM), and DCM and toluene. A number of physical properties that control the retention and transport of DNAPL in porous media were measured for the mixtures, namely: density, interfacial tension, effective solubility, and viscosity. All properties except density exhibited nonlinear relationships with changing molar ratio of the DNAPL. To illustrate the potential for natural remobilization, we modelled the following two primary mechanisms: the reduction in pool height as mass is lost by dissolution, and the changes in fluid properties with changing molar ratio of the DNAPL. The first mechanism always reduces the capillary pressure in the pool, while the second mechanism may increase the capillary pressure or alter the direction of the driving force. The difference between the rate of change of each determines whether the potential for remobilization increases or decreases. Static conditions and horizontal layering were assumed along with a one-dimensional, compositional modelling approach. Our results indicated that for initial benzene/PCE ratios greater than 25:75, the change in density was sufficiently faster than the decline in pool height to promote DNAPL breakthrough into the adjacent porous medium. In contrast, there was no potential for natural remobilization of a PCE-DCM mixture, primarily because the densities of the components are not sufficiently different. Dissolution of a DCM-toluene mixture decreased the density, reducing the tendency for downward displacement. However, the ultimate transformation from a DNAPL to an LNAPL may induce upward displacement. These results suggest that at sites with DNAPL pools containing a mix of components of sufficiently different densities and relative solubilities, natural remobilization may be an active mechanism, with implications for site evaluation and remediation. 相似文献
926.
927.
This paper presents a dynamic framework for environmental assessment when the system under study is undergoing successional
change. Successional differences between sites for which one wishes to detect a difference because of a treatment are essentially
confounding factors. We show how successional changes over the study period or resulting from differences in study site plot
ages can be factored out by developing a null model of expected behavior over time. The null model for change in state with
time is characterized in terms of a stochastic envelope around a nominal trajectory. Specific tests for the detection of trends
associated with succession are described and illustrated on example data. It is concluded that the methods developed work
particularly well for laboratory microcosm data. 相似文献
928.
929.
Conditional lekking in ruff (Philomachus pugnax) 总被引:3,自引:0,他引:3
Summary In our study of ruff, a lekking shorebird, we found that the lek ratio — the proportion of the total population of males occurring on leks was low, averaging 12% over the breeding season (Fig. 1D). Off-lek males spent approximately the same proportion of time as lek males in displaying to females (Fig. 4). We defined three spacing tacties that male ruffs use to position themselves to court females: Following — directly pursuing females, and two types of lekking behavior, Intercepting — waiting for females at resource-rich sites, and True Lekking — waiting for females at places without any resources other than the males themselves. Males switched among these tactics, causing the lek ratio to vary over the season (Fig. 1 D). Lek ratio increased when the number of females present in the study area plummeted at the end of May, and was positively correlated throughout the season with the copulation rate of the preceding day, suggesting that males were tracking the behavior, as well as the number, of females available (Table 1, Fig. 1). Early in the season, males off leks spent most of their time feeding (Fig. 4), and lek ratio was positively correlated with temperature (Table 1), suggesting that some males may have been unable to lek during cold weather. Males on leks mated at significantly higher rates than Followers (Table 4). On average, males at our interception lek were less site faithful and less peristent than males at true leks, and the interception lek itself disappeared after females stopped coming to use its adjacent resource (Table 2, Fig. 5). The most successful individuals in our population were the True Lekking males, rather than the Interceptors.In addition to the conditinal lekking tactics described here, ruff display a dimorphism in behaviorat leks. Independent males defend small courts on leks, while Satellite males share courts and mutually display with independents Both independents and satellites may use all three conditional tactics. We propose that satellites evolved as specialized. Followers, adept at tracking the movements of females among leks. 相似文献
930.
Sohel Q. Saikat Joy E. Carter Aradhana Mehra Barry Smith Alex Stewart 《Environmental geochemistry and health》2004,26(3-4):395-401
Endemic goitre was prevalent in the population of Derbyshire in the UK for many centuries until it declined from the 1930s. A contemporary medical survey showed that endemicity of goitre was particularly higher in the Carboniferous limestone areas of the Derbyshire-Peak District. Unlike classical goitrous areas of the world, where the distribution of goitre has been found to be related to the iodine content in the environment, there is no such relationship reported for the Derbyshire-Peak District area. The present study reviews the presence of endemic goitre in this area with reference to iodine in different environmental media using past and present data. In comparison with the world average values, the iodine contents in the soil and sediment in the Peak District are not deficient, but compared to England, Wales and Scotland averages, these levels are low. As no information on the mobility and bioavailability of iodine of this area is available, a cautious approach is necessary before any assumption is made on the aetiology of endemic goitre. The study also discusses some hypotheses relating to the possible cause of endemic goitre in the limestone areas. Further research needs are suggested depending on the land use and geochemistry of the Peak District to determine the underlying causes of the former endemic goitre in this area. 相似文献