全文获取类型
收费全文 | 5474篇 |
免费 | 481篇 |
国内免费 | 1485篇 |
专业分类
安全科学 | 547篇 |
废物处理 | 181篇 |
环保管理 | 1427篇 |
综合类 | 2753篇 |
基础理论 | 857篇 |
污染及防治 | 915篇 |
评价与监测 | 405篇 |
社会与环境 | 264篇 |
灾害及防治 | 91篇 |
出版年
2024年 | 6篇 |
2023年 | 73篇 |
2022年 | 135篇 |
2021年 | 172篇 |
2020年 | 164篇 |
2019年 | 195篇 |
2018年 | 180篇 |
2017年 | 232篇 |
2016年 | 299篇 |
2015年 | 282篇 |
2014年 | 344篇 |
2013年 | 433篇 |
2012年 | 418篇 |
2011年 | 479篇 |
2010年 | 357篇 |
2009年 | 522篇 |
2008年 | 304篇 |
2007年 | 349篇 |
2006年 | 328篇 |
2005年 | 323篇 |
2004年 | 228篇 |
2003年 | 218篇 |
2002年 | 193篇 |
2001年 | 155篇 |
2000年 | 156篇 |
1999年 | 136篇 |
1998年 | 106篇 |
1997年 | 80篇 |
1996年 | 89篇 |
1995年 | 94篇 |
1994年 | 53篇 |
1993年 | 39篇 |
1992年 | 45篇 |
1991年 | 28篇 |
1990年 | 25篇 |
1989年 | 22篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有7440条查询结果,搜索用时 15 毫秒
141.
Adaptive management: Promises and pitfalls 总被引:3,自引:1,他引:3
Proponents of the scientific adaptive management approach argue that it increases knowledge acquisition rates, enhances information flow among policy actors, and provides opportunities for creating shared understandings. However, evidence from efforts to implement the approach in New Brunswick, British Columbia, Canada, and the Columbia River Basin indicates that these promises have not been met. The data show that scientific adaptive management relies excessively on the use of linear systems models, discounts nonscientific forms of knowledge, and pays inadequate attention to policy processes that promote the development of shared understandings among diverse stakeholders. To be effective, new adaptive management efforts will need to incorporate knowledge from multiple sources, make use of multiple systems models, and support new forms of cooperation among stakeholders. 相似文献
142.
143.
Thomas J. Myers Sherman Swanson 《Journal of the American Water Resources Association》1996,32(2):253-265
ABSTRACT: Detailed studies of long-term management impacts on rangeland streams are few because of the cost of obtaining detailed data replicated in time. This study uses government agency aquatic habitat, stream morphologic, and ocular stability data to assess land management impacts over four years on three stream reaches of an important rangeland watershed in northwestern Nevada. Aquatic habitat improved as riparian vegetation reestablished itself with decreased and better controlled livestock grazing. However, sediment from livestock disturbances and road crossings and very low stream flows limited the rate of change. Stream type limited the change of pool variables and width/depth ratio, which are linked to gradient and entrenchment. Coarse woody debris removal due to previous management limited pool recovery. Various critical-element ocular stability estimates represented changes with time and differences among reaches very well. Ocular stability variables tracked the quantitative habitat and morphologic variables well enough to recommend that ocular surveys be used to monitor changes with time between more intensive aquatic surveys. 相似文献
144.
Frank A. Ward Thomas P Lynch 《Journal of the American Water Resources Association》1996,32(6):1127-1138
ABSTRACT: This paper presents an integrated optimal control model that optimizes economic performance of reservoir management in watersheds in which there are significant economic and hydrologic interdependencies. The model is solved using the General Algebraic Modeling System (GAMS). Results show that application of this model to New Mexico's Rio Chama basin can increase total system benefits over historical benefits by exploiting complementarities between hydroelectricity production, instream recreation, and downstream lake recreation. 相似文献
145.
D. E. Barb J. F. Cruise X. Mo 《Journal of the American Water Resources Association》1996,32(3):511-519
ABSTRACT: A model for urban stormwater quality was developed in this study. The basis for the model is the process by which pollutants build up on the watershed surface. For the wet climate of the study site, it was assumed that there exists an interval of time over which the pollutant buildup equals the pollutant washoff (no accumulation of pollutant). The buildup model was represented by a linear function of the antecedent dry time. The buildup function was then linked with a pollutant washoff model represented by a power function of the storm runoff volume. Various time intervals for no net accumulation were tested to calibrate the model. The model was calibrated to observed data for two small urban basins in Baton Rouge, Louisiana, and model results were used to analyze the behavior of phosphorus concentrations in storm runoff from these basins over a long period of time. 相似文献
146.
Alberto Padilla Antonio Pulido-Bosch Maria L. Calvache Angela Vallejos 《Journal of the American Water Resources Association》1996,32(5):917-928
ABSTRACT: Autoregressive moving average (ABMA) models have been applied to study the flow series of the karstic springs of La Villa, Fuente Mayor (Spain), and Aliou (France). The theoretical meaning of the parameters involved in the model upon applying it to a simplified scheme of the emptying of a karstic aquifer is first analyzed. The types of transformations necessary to apply these models to the flow series that lack normality and have strong periodic components are also indicated, as are the advantages of this type of model and the physical significance of the parameters obtained, with respect to the standpoint of hydraulics, ranging from rather homogeneous aquifers (La Villa) to extremely karstic (Aliou), including aquifers with intermediate characteristics (Fuente Mayor). 相似文献
147.
建筑火灾区域模拟竖孔流动的计算 总被引:2,自引:0,他引:2
本文根据建筑火灾双层区域模拟思想,给出其常微分控制方程组,并分析了其压力求解方法,然后,运用伯努力利方程推导了相邻房间通过矩形竖孔(门或窗)的质量流率计算公式,还讨论了竖孔流动中性面产生条件。在此基础上,结合一两房间、两孔建筑中烟气运动实例,运用C.W.Gear刚性稳定算法对火灾发展及烟气流动过程进行了数值模拟;给出各竖孔中性面位置、数量和各主环境之间通过竖孔的质量流率;还给出各房间气体平均温升、 相似文献
148.
Thermal and mechanical properties of poly(lactic Acid) and poly(ethylene/butylene Succinate) blends 总被引:2,自引:0,他引:2
In this study, blends of poly (lactic acid) (PLA) with poly(ethylene/butylene succinate) (Bionolle) have been investigated
for their thermal and mechanical properties as a function of the concentration of Bionolle. Differential scanning calorimetry
(DSC), dynamic mechanical analysis (DMA), and tensile tests were used to characterize the blends. From the results of the
DMA and DSC, it was found that this blend system was not miscible within the compositions studied. DSC results showed that
adding Bionolle aids in crystallization of PLA. It was observed that increasing the Bionolle concentration led to a slight
increase in the strain-at-break of the blends but a decrease in the Young’s modulus and ultimate tensile strength. Biaxially
oriented films showed an increase in tensile strength, modulus, and strain-at-break. 相似文献
149.
The use of pressure-volume-temperature (PVT) studies in processing of a biodegradable plastic composition made from soy protein
isolate and corn starch is described. The ability of PVT measurements to predict the combined effects of pressure, volume,
and temperature effects is demonstrated. The results show that the PVT relations of the plastic can be predicted by using
a regression analysis similar to the Tait equations of state. A change in slope of the PVT curves was observed at around 80‡C,
which is ascribed to the glass-transition process of the plastic. Evidence of onset of thermal degradation of the plastic
was observed at ca. 160‡C under 0 to 200 MPa isobaric pressure. This thermal degradation precluded determination of the crystal
melting point of the plastic. 相似文献
150.