全文获取类型
收费全文 | 41055篇 |
免费 | 425篇 |
国内免费 | 309篇 |
专业分类
安全科学 | 1089篇 |
废物处理 | 1568篇 |
环保管理 | 5363篇 |
综合类 | 7499篇 |
基础理论 | 11085篇 |
环境理论 | 27篇 |
污染及防治 | 10413篇 |
评价与监测 | 2487篇 |
社会与环境 | 2027篇 |
灾害及防治 | 231篇 |
出版年
2022年 | 272篇 |
2021年 | 278篇 |
2019年 | 293篇 |
2018年 | 549篇 |
2017年 | 525篇 |
2016年 | 786篇 |
2015年 | 664篇 |
2014年 | 932篇 |
2013年 | 2946篇 |
2012年 | 1138篇 |
2011年 | 1675篇 |
2010年 | 1363篇 |
2009年 | 1430篇 |
2008年 | 1690篇 |
2007年 | 1793篇 |
2006年 | 1612篇 |
2005年 | 1356篇 |
2004年 | 1369篇 |
2003年 | 1305篇 |
2002年 | 1266篇 |
2001年 | 1634篇 |
2000年 | 1116篇 |
1999年 | 750篇 |
1998年 | 556篇 |
1997年 | 577篇 |
1996年 | 593篇 |
1995年 | 655篇 |
1994年 | 602篇 |
1993年 | 548篇 |
1992年 | 537篇 |
1991年 | 513篇 |
1990年 | 515篇 |
1989年 | 517篇 |
1988年 | 474篇 |
1987年 | 408篇 |
1986年 | 378篇 |
1985年 | 408篇 |
1984年 | 420篇 |
1983年 | 433篇 |
1982年 | 449篇 |
1981年 | 385篇 |
1980年 | 340篇 |
1979年 | 355篇 |
1978年 | 324篇 |
1977年 | 275篇 |
1976年 | 277篇 |
1975年 | 274篇 |
1974年 | 259篇 |
1973年 | 243篇 |
1972年 | 270篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
J. Malczewski R. Moreno-Sanchez L.A. Bojorquez-Tapia E. Ongay-Delhumeau 《Journal of Environmental Planning and Management》1997,40(3):349-374
This paper is concerned with developing a model for group decision making under multiple criteria. The multiple criteria group decision making (MCGDM)problem involves a set of feasible land use patterns that are evaluated on the basis of multiple, conflicting and noncommensurate criteria by a group of individuals. The model integrates the Analytic Hierarchy Process (AHP) and an integer mathematical programming method. The former provides a tool for structuring the decision problem and determining land suitability for different socio-economicactivities (the uses of land), the latter is used to identify the land use pattern that maximizes consensus among interest groups. The model is used to analyze environmental conflict over land resource allocation in the Cape Region of Mexico. 相似文献
12.
13.
From 1988 to 1991, we studied the postfledging dispersal of 31 radio-tagged White-crowned Pigeons ( Columba leucocephala ) from three natal keys in Florida Bay. Immature birds dispersed from the natal keys at 26–45 days after batching, and most young dispersed more than 20 km during the first 10 days postdispersal. Dispersing birds flew either north to the Florida mainland or east to northeast to the mainline Florida Keys. On the mainland, immature birds fed nearly exclusively within Everglades National Park or an adjacent state wildlife management area. On the mainline keys, White-crowned Pigeons selectively used 5.01–20 ha forest fragments (p < 0.10) during the first 72 hours postdispersal. After this period, dispersing birds showed no preference among fragment size classes but used deciduous seasonal forests more frequently than suburban habitat(p < 0.10). The spatial pattern of dispersal on the mainline keys suggests that, during the first 72 hours postdispersal. White-crowned Pigeons are not able to reach northern Key Largo, where 69% of the deciduous seasonal forests are protected in state or federal ownership. Protection of large forest fragments, especially on southern Key Largo, should be a priority for maintaining populations of White-crowned Pigeons. These forests provide a series of "stepping stones" that enable dispersing immature White-crowned Pigeons to fly to more distant areas where habitat availability is less restricted. This species is threatened in Florida and may play an important role in maintaining plant species diversity in the seasonal deciduous forests of south Florida by dispersing seeds of at least 37 species of trees and shrubs. Protection of sufficient habitat to allow successful postfledging dispersal of this important seed disperser will also protect the ecosystem's biodiversity. 相似文献
14.
We examined the impact of stressful job demands on employee attitudes and attendance. Using Karasek's (1979) theory of job decision latitude as the conceptual foundation, we hypothesized that mental and physical work demands would interact with employee beliefs of personal control. Survey data from 90 male manufacturing employees regarding their control beliefs were combined with objective job analysis data concerning mental and physical demands and one year's worth of archival data regarding unexcused absences, sick days, and days tardy. There were significant interactions between control and objective psychological demands that indicated that these demands were associated with higher levels of tardiness and sick days only under conditions of low perceived control. In contrast, subjective workload ratings showed no relationship with tardiness and sick days, but, in interaction with control, predicted work satisfaction and voluntary absence. We discussed these results in terms of a stress process that affects health-related attendance independent of employee attitudes. 相似文献
15.
New birds on the block: new neighbors increase defensive costs for territorial male willow ptarmigan 总被引:4,自引:0,他引:4
Previous researchers have hypothesized that site-faithful animals may benefit from the presence of familiar neighbors. This study compares the relative costs of territorial defense against new and former neighbors by male willow ptarmigan (Lagopus lagopus). Territorial defense against new neighbors appeared to require a greater expenditure of both time and effort than did defense against former neighbors. Territorial males that had several new neighbors spent a higher proportion of time fighting than did males with fewer new neighbors, and males with both new and former neighbors spent a greater amount of time fighting with their new neighbors, on average, than with their former neighbors. In addition, fights with new neighbors occurred relatively more frequently and were longer than fights with former neighbors. Finally, fights involving new neighbors tended to escalate to higher levels than fights between former neighbors. Reduced defensive costs for site-faithful, territorial males may provide one explanation for the tendency of males to be more site-faithful than females in many species. 相似文献
16.
17.
18.
This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997. 相似文献
19.
Dr. J. F. Bruch P. Metezeau N. Garcia-Fonknechten Y. Richard V. Tricottet B.-L. Hsi A. Kitzis C. Julien E. Papiernik 《黑龙江环境通报》1991,11(10):787-798
Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free inter-villous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities. 相似文献
20.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献