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171.
江西省兴国县土壤侵蚀动态监测研究 总被引:5,自引:0,他引:5
介绍发应用遥感技术和调查资料编制的江西省兴国县三个时期(1958,1975,1988年)的土壤侵蚀动态监测图。结果表明,建国以来,该县水土流失的动态变化基本上呈抛物线的态势发展,目前水土流失面积在缩小,程度在降低,总的趋势向好的方向发展。 相似文献
172.
中国黄土高原的形成过程与整治研究 总被引:5,自引:0,他引:5
从黄土高原的形成过程,黄土-古土壤性征的对比,孢粉、石器、历史、地理以及水土流失的定位观测资料,说明目前黄土高原的严重水土流失是人类破坏植被,不合理利用土地和直接毁灭土壤透水和抗冲能力的结果,而不是一个天然的地质过程。以“28字方略”为中心的水土保持措施是开发整治黄土高原水土资源和治理黄河的根本。 相似文献
173.
施少华 《中国人口.资源与环境》1994,4(2):44-48
本文统计分析了历史时期黄河决溢的变化。并从自然和人为因素两方面探讨其原因和规律。认为在湿润的气候时期黄河决溢频率增高,其原因是本地区高强度的暴雨造成了黄土高原严重的水土流失,从而使黄河中下游大量的泥沙沉积。人类特别是小冰期以来加强了对黄土高原的开发,破坏了原先的植被,从而造成了严重的水土流失,这是小冰期以来黄河决溢次数远远高于其它时期的主要原因。作者还认为在下世纪高温环境到来之际,黄河决溢的危险性大大增加。 相似文献
174.
AN ALGORITHM FOR ESTIMATING SURFACE SUSPENDED SEDIMENT CONCENTRATIONS WITH LANDSAT MSS DIGITAL DATA1
Jerry C. Ritchie Charles M. Cooper 《Journal of the American Water Resources Association》1991,27(3):373-379
ABSTRACT: Algorithms for Landsat MSS digital data are needed to reduce the necessity of calibrating each Landsat scene if these data are to be useful in monitoring programs for surface suspended sediments. In this study digital data were extracted from 16 Landsat Multispectral Scanner (MSS) scenes collected between March 1987 and August 1988 over Enid Reservoir in North Central Mississippi. These data were converted to radiance and reflectance data for comparison with field measurements of surface suspended sediment concentrations. Concentrations ranged from 2 to 168 mg/1 during the study with only four greater than 100 mg/l. Linear and polynomial regression analyses were used to relate the surface suspended sediment concentrations with radiance and reflectance. Reflectance in MSS band 2 (0.6 to 0.7 μm) and MSS band 3 (0.7 to 0.8 μm) were best related to the surface suspended sediment concentrations with coefficients of determination accounting for 71 percent and 68 percent of the variation in the data, respectively. Regressions with radiance data accounted for 36 percent (band 2) or less of the variation. Logarithmic transformations of either reflectance or sediment concentrations increase the coefficients of determination for MSS band 2 reflectance data to 81 percent. Regressions between the ratio of MSS band 1 to MSS band 2 reflectances and concentrations also accounted for 80 percent of the variation. An equation Loge SS (mg/l) = 9.21R½+ 2.71R½2 + 8.45, where S is surface suspended sediment concentrations and R1/2 is the ratio of MSS band 1 to MSS band 2 reflectances, provided the best fit to the data with a coefficient of determination of 0.82. This equation is essentially the same as an algorithm proposed by Topliss et at. (1990), for estimating surface suspended sediment concentrations in Canadian coastal waters. These equations for Enid Reservoir and Canadian waters suggest that it may be possible to develop an algorithm for widespread use for estimating surface suspended sediments. 相似文献
175.
Gerald G. Garland 《Environmental management》1990,14(6):793-798
One of the most pressing problems facing wilderness managers in the ecologically fragile Drakensberg Mountains, South Africa,
is that of path erosion, since it detracts from the wilderness experience and is very costly to remediate. As increasing demand
for wilderness and outdoor recreation places greater pressure on paths and trails, it will be necessary to increase path network
size and capacity, and it is important that new paths are routed such that maintenance requirements are minimal.
This study describes the development of a technique based on the site and environmental variables of rainfall, topographic
slope, and lithology, which enables assessment of path erosion risk before paths are planned and constructed. The technique
was tested on a path at the Drakensberg resort of Loteni, and showed good correlation with actual path degradation. When used
as a tool in path network planning, it can aid in the selection of low-maintenance routes and also help in planning maintenance
budgets. 相似文献
176.
高原封闭、半封闭型湖泊是气候和环境演化的敏感指示器,其沉积物记录具有连续性、敏感性和高分辨率的特点。高原湖泊沉积记录在恢复和重塑各种短时间尺度(千年、百年、十年)的气候和环境演化序列上,具有其它自然历史记录无法替代的优势,尤其在揭示近代环境污染历史方面更有其独到之处。本文通过对洱海沉积物重金属地球化学相的研究,利用因子分析方法,识别了沉积物重金属的主要来源和影响其分布的主要因素,即:流域侵蚀作用、大气沉降作用、工业废水与生活污水的排放,以及早期成岩作用。同时,结合沉积物柱芯210PBex计年结果,本文初步评价了洱海150多年来的重金属污染历史:1958年以来.因为化石燃料使用量的增加.洱海湖区大气污染日趋严重;1982年后,由于西洱河水电站的建成运行和湖区植被的破坏,流域侵蚀作用显著加强,应当引起重视。 相似文献
177.
178.
William F. Schillinger Ann C. Kennedy Douglas L. Young 《Agriculture, ecosystems & environment》2007,120(2-4):345-358
The tillage-based winter wheat (Triticum aestivum L.)-summer fallow (WW-SF) cropping system has dominated dryland farming in the Pacific Northwest USA for 125 years. We conducted a large-scale multidisciplinary 8-year study of annual (i.e., no summer fallow) no-till cropping systems as an alternative to WW-SF. Soft white and hard white classes of winter and spring wheat, spring barley (Hordeum vulgare L.), yellow mustard (Brassica hirta Moench), and safflower (Carthamus tinctorius L.) were grown in various rotation combinations. Annual precipitation was less than the long-term average of 301 mm in 7 out of 8 years. Rhizoctonia bare patch disease caused by the fungus Rhizoctonia solani AG-8 appeared in year 3 and continued through year 8 in all no-till plots. All crops were susceptible to rhizoctonia, but bare patch area in wheat was reduced, and grain yield increased, when wheat was grown in rotation with barley every other year. Remnant downy brome (Bromus tectorum L.) weed seeds remained dormant for 6 years and longer to heavily infest recrop winter wheat. There were few quantifiable changes in soil quality due to crop rotation, but soil organic carbon (SOC) increased in the surface 0–5 cm depth with no-till during the 8 years to approach that found in undisturbed native soil. Annual no-till crop rotations experienced lower average profitability and greater income variability compared to WW-SF. Yellow mustard and safflower were not economically viable. Continuous annual cropping using no-till provides excellent protection against wind erosion and shows potential to increase soil quality, but the practice involves high economic risk compared to WW-SF. This paper provides the first comprehensive multidisciplinary report of long-term alternative annual no-till cropping systems research in the low-precipitation region of the Pacific Northwest. 相似文献
179.
180.