全文获取类型
收费全文 | 14757篇 |
免费 | 150篇 |
国内免费 | 113篇 |
专业分类
安全科学 | 395篇 |
废物处理 | 399篇 |
环保管理 | 2063篇 |
综合类 | 3807篇 |
基础理论 | 3375篇 |
环境理论 | 13篇 |
污染及防治 | 3811篇 |
评价与监测 | 661篇 |
社会与环境 | 429篇 |
灾害及防治 | 67篇 |
出版年
2018年 | 153篇 |
2017年 | 165篇 |
2016年 | 217篇 |
2015年 | 186篇 |
2014年 | 241篇 |
2013年 | 1047篇 |
2012年 | 339篇 |
2011年 | 505篇 |
2010年 | 358篇 |
2009年 | 460篇 |
2008年 | 529篇 |
2007年 | 556篇 |
2006年 | 497篇 |
2005年 | 386篇 |
2004年 | 385篇 |
2003年 | 425篇 |
2002年 | 365篇 |
2001年 | 520篇 |
2000年 | 359篇 |
1999年 | 242篇 |
1998年 | 168篇 |
1997年 | 162篇 |
1996年 | 194篇 |
1995年 | 193篇 |
1994年 | 227篇 |
1993年 | 192篇 |
1992年 | 193篇 |
1991年 | 195篇 |
1990年 | 218篇 |
1989年 | 205篇 |
1988年 | 171篇 |
1987年 | 170篇 |
1986年 | 156篇 |
1985年 | 173篇 |
1984年 | 159篇 |
1983年 | 166篇 |
1982年 | 170篇 |
1981年 | 179篇 |
1980年 | 156篇 |
1979年 | 152篇 |
1978年 | 146篇 |
1977年 | 136篇 |
1976年 | 144篇 |
1975年 | 121篇 |
1974年 | 153篇 |
1973年 | 131篇 |
1972年 | 131篇 |
1967年 | 126篇 |
1966年 | 115篇 |
1965年 | 112篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Recovery of temperate-stream fish communities from disturbance: A review of case studies and synthesis of theory 总被引:3,自引:0,他引:3
Naomi E. Detenbeck Philip W. DeVore Gerald J. Niemi Ann Lima 《Environmental management》1992,16(1):33-53
To evaluate the relative effect of autecologic factors, site-specific factors, disturbance characteristics, and community
structure on the recovery of temperate-stream fish communities, we reviewed case histories for 49 sites and recorded data
on 411 recovery end points. Most data were derived from studies of low-gradient third- or fourth-order temperate streams located
in forested or agricultural watersheds. Species composition, species richness, and total density all recovered within one
year for over 70% of systems studied. Lotic fish communities were not resilient to press disturbances (e.g., mining, logging,
channelization) in the absence of mitigation efforts (recovery time >5 to >52 yr) and in these cases recovery was limited
by habitat quality. Following pulse disturbances, autecological factors, site-specific factors, and disturbance-specific factors
all affected rates of recovery. Centrarchids and minnows were most resilient to disturbance, while salmonid populations were
least resilient of all families considered. Species within rock-substrate/nest-spawning guilds required significantly longer
time periods to either recolonize or reestablish predisturbance population densities than did species within other reproductive
guilds. Recovery was enhanced by the presence of refugia but was delayed by barriers to migration, especially when source
populations for recolonization were relatively distant. Median population recovery times for systems in which disturbances
occurred during or immediately prior to spawning were significantly less than median recovery times for systems in which disturbances
occurred immediately after spawning. There was little evidence for the influence of biotic interactions on recovery rates. 相似文献
992.
993.
A field experiment investigated factors expected to influence yielding by motorists to a pedestrian waiting to cross a city street. Subjects consisted of 604 motorists who passed through two marked crosswalks. Motorists were significantly more likely to stop for a disabled pedestrian using a cane than a non-disabled pedestrian without a cane. This study also evaluated the impact of a ‘fatality sign’ erected before one of the crossings. While the fatality sign by itself had no significant effect on motorists yielding, there was a strong interactive effect of the sign and the disability manipulation. Thus, the greatest levels of motorists yielding occurred for subjects who were exposed to the fatality sign and the disabled pedestrian. In contrast, the lowest levels of yielding occurred at the fatality-marked crossing for a non-disabled pedestrian. 相似文献
994.
Two studies were designed to test hypotheses derived from Locke's (1969, 1976, 1984) model of job satisfaction. Consistent with the model, both studies found that perceived have-want discrepancy scores were powerful predictors of facet job satisfaction. In addition, facet importance tended to moderate this relationship in the manner predicted by Locke. Workers who viewed a job facet as having high importance were more satisfied with a small perceived have-want discrepancy and more dissatisfied with a large discrepancy than workers who viewed the facet as having low importance. Finally, as expected, facet importance failed to moderate the relationship between facet satisfaction and overall job satisfaction. This finding supports Locke's proposition that facet satisfaction scores are ‘implicitly weighted’ by facet importance. Implications and directions for future research are discussed. 相似文献
995.
Jurgen Garbrecht Lawrence W. Martz 《Journal of the American Water Resources Association》1993,29(6):909-916
ABSTRACT: An automated extraction of channel network and sub-watershed characteristics from digital elevation models (DEM) is performed by model DEDNM. This model can process DEM data of limited vertical resolution representing low relief terrain. Such representations often include ill-defined drainage boundaries and indeterminate flow paths. The application watershed is an 84 km2 low relief watershed in southwestern Oklahoma. The standard for validation is the network and subwatershed parameters defined by the blue line method on USGS 7.5–minute topographic maps. Evaluation of the generated and validation networks by visual comparisons shows a high degree of correlation. Comparison of selected network parameters (channel length, slope, drainage density, etc.) and of drainage network composition (bifurcation, length, slope, and area ratios) shows that, on the average, the generated parameters are within 5 percent of those derived from the validation network. The largest discrepancies were found for the channel slope values. The results of this application demonstrate that DEDNM effectively addresses network definition problems often encountered in low relief terrain and that it can generate accurate network and subwatershed parameters under those conditions. 相似文献
996.
In previous research on unemployment, conflicting evidence has been found for a ‘reverse causation interpretation’, indicating that prolonged unemployment is a consequence of psychological distress instead of the reverse. The present longitudinal study was conducted to test this reverse causation explanation. A second issue addressed in this study was whether getting a job or not depends more strongly on subjective or psychological factors than on objective factors (e.g. a person's biographical background, length of unemployment). Two independent samples were examined: Sample 1 (n = 635) consisted of school-leavers, and sample 2 (n = 467) consisted of subjects who had been unemployed for more than one year. Some support was found for the reverse causation explanation. In addition, more than objective factors, a strong job orientation and a problem focused coping style appeared to be a precursor of success in the labour market. Accordingly, getting a job seems to be primarily a function of one's own efforts. 相似文献
997.
998.
MARIJKE WIJNROKS MARTIN W. BLOEM NAEL ISLAM HABIB RAHMAN SWAPAN KUMAR DAS ABDUL HYE GILLIAN HALL 《Disasters》1993,17(4):348-356
Early in 1992, Bangladesh experienced an influx of Burmese refugees, reaching a total of 263,000 by May. As the health and nutritional status of the refugee population was reportedly poor, a need was felt to collect dependable data through epidemiological surveillance, on which interventions could be based. The nutritional and health status of children was dramatically poor in all camps surveyed and a deterioration was expected in the coming monsoon. Several problem areas could be identified. Based on these findings it was possible to undertake appropriate action and to avert threatening calamities. Epidemiological surveillance is an important monitoring tool to provide reliable data on the health and nutritional status of refugee populations and to help the organizations involved to prioritize and evaluate their actions. 相似文献
999.
W. B. Kirchner S. Grabowski 《Journal of the American Water Resources Association》1972,8(6):1259-1264
This paper serves as a literature review of manganese in fresh water. The major aspects of manganese occurrence discussed are: (1) sources, (2) geochemistry, (3) manganese-iron relationships, (4) effects on the fauna and flora and (5) detection. 相似文献
1000.
Charles W. Howe 《Journal of the American Water Resources Association》1971,7(4):670-675
ABSTRACT
Three main issues are discussed: the demands for additional water stemming from population dispersion; supply alternatives to large-scale interbasin transfers; and the displacement of agriculture from nonprofit regions. It is concluded that population dispersion is unlikely to increase aggregate water demands; that large additional supplies are available from other sources at lesser costs; and that a very likely consequence of large-scale transfers will be the displacement of agriculture in other parts of the country. 相似文献
Three main issues are discussed: the demands for additional water stemming from population dispersion; supply alternatives to large-scale interbasin transfers; and the displacement of agriculture from nonprofit regions. It is concluded that population dispersion is unlikely to increase aggregate water demands; that large additional supplies are available from other sources at lesser costs; and that a very likely consequence of large-scale transfers will be the displacement of agriculture in other parts of the country. 相似文献