全文获取类型
收费全文 | 556篇 |
免费 | 7篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 28篇 |
废物处理 | 24篇 |
环保管理 | 142篇 |
综合类 | 51篇 |
基础理论 | 148篇 |
环境理论 | 1篇 |
污染及防治 | 110篇 |
评价与监测 | 46篇 |
社会与环境 | 15篇 |
灾害及防治 | 6篇 |
出版年
2023年 | 5篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 15篇 |
2014年 | 15篇 |
2013年 | 51篇 |
2012年 | 17篇 |
2011年 | 35篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 28篇 |
2007年 | 32篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 9篇 |
2003年 | 24篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 15篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有571条查询结果,搜索用时 62 毫秒
231.
Herman E. Wyandt Ph.D. Thomas Maker Nancy L. Fisher Shivanand R. Patil Peter Osella Frederick W. Luthardt Charles Kawada Roger Williamson Aubrey Milunsky 《黑龙江环境通报》1990,10(9):569-574
We report three cases of amniocentesis in which mosaicism for trisomy 12 was detected in two or more independent cultures. The parents elected to terminate the pregnancy in all three cases. Follow-up studies in two of the cases confirmed the mosaicism in fetal tissues (in subcutaneous tissue in one case; in fetal lung in the other), but not in blood. No fetal anomalies were evident by ultrasound or at autopsy. These results along with other reported cases demonstrate the difficulty in counselling for mosaic trisomy 12. 相似文献
232.
Acomprehensive,standardized,andthematicallyappropriatemapofCentralAmericanvegetationandlandcovertypeswasdevelopedbyclassifyingtheremotesensedimagery(AVHRR)1km2 相似文献
233.
Clark NN Kern JM Atkinson CM Nine RD 《Journal of the Air & Waste Management Association (1995)》2002,52(1):84-94
Societal and governmental pressures to reduce diesel exhaust emissions are reflected in the existing and projected future heavy-duty certification standards of these emissions. Various factors affect the amount of emissions produced by a heterogeneous charge diesel engine in any given situation, but these are poorly quantified in the existing literature. The parameters that most heavily affect the emissions from compression ignition engine-powered vehicles include vehicle class and weight, driving cycle, vehicle vocation, fuel type, engine exhaust aftertreatment, vehicle age, and the terrain traveled. In addition, engine control effects (such as injection timing strategies) on measured emissions can be significant. Knowing the effect of each aspect of engine and vehicle operation on the emissions from diesel engines is useful in determining methods for reducing these emissions and in assessing the need for improvement in inventory models. The effects of each of these aspects have been quantified in this paper to provide an estimate of the impact each one has on the emissions of diesel engines. 相似文献
234.
The goal of this study was to investigate the influence of one variable, natural organic matter, on residual gasoline saturation in sandy soils. Capillary pressure-saturation (Pc−S) relationships (air-gasoline) were determined for three physically-similar sandy soils, with different organic carbon contents (0.086%, 0.89% and 1.65%) and residual gasoline saturations were compared. Two initial moisture conditions, residual water saturation and air-dry, were evaluated. One soil type was packed to two different bulk densities. Visualization of the soils using cryo-scanning electron microscopy was performed to aid in better understanding the role of the organic matter in the soil. The results showed that soils with higher organic contents had higher residual gasoline saturations when starting with an initially air-dry soil. Increasing the bulk density of the same air-dried soil resulted in an increase in residual gasoline saturation. In the presence of a residual water saturation, however, residual gasoline saturations were virtually identical for the three soils and independent of bulk density; approximately 5–10 times lower than in soil that was initially air-dry. The presence of the residual water effectively coated the surface of the soil thereby reducing or eliminating gasoline/soil interactions. Some residual water may also be occupying very small pore spaces, making these locations inaccessible to the gasoline. 相似文献
235.
Juniper (Juniperus monosperma), a small-diameter underutilized material, has been studied as a lignocellulosic biosorbent for removing heavy metals from water. In this study, juniper wood was modified by sulfonation to enhance sorption capacity for cadmium in water. The origin of the enhancement was investigated by observing the sorption behaviors and the change in surface functional group concentrations. Cadmium sorption by all juniper wood biosorbents studied was fast and the sorption capacity decreased with decreasing pH, similar to results found for other biosorbents. Sulfonated juniper was found to have at least twice the sorption capacity for cadmium removal from water compared to that of untreated juniper, though the sorption capacity increased with increasing pH. A slight increase in carboxylate content after sulfonation was likely responsible for a small portion of the enhancement. Elemental analysis showed an increase in sulfur content after sulfonation. Diffuse reflectance infrared Fourier transform (DRIFT) spectra showed a decrease in the band at 1660 cm(-1) in the range of carbonyl groups as a result of sulfonation. This indicates that coniferaldehyde groups in the lignin of juniper wood corresponding to this band were substituted into sulfonic acid groups after sulfonation. This interpretation was supported by both the color forming reaction with phloroglucinol-hydrochloric acid and the reaction mechanisms from the acid sulfite pulping process. Consequently, the enhancement of cadmium sorption capacity of juniper wood by sulfonation mainly originated from the production of sulfonic acid groups, which are binding sites for heavy metals. 相似文献
236.
237.
238.
C. Roger 《Marine Biology》1973,18(4):317-320
Analysis of the fluctuations of the repletion index of stomachs over a 24 h period allowed us to establish the main features of the feeding behaviour for the most abundant species of euphausiids inhabiting the equatorial and south tropical Pacific Ocean. Although feeding activity never stops completely, its intensity shows usually a rhythm, revealed by a sinusoid-type curve of the repletion index. This rhythm, in most cases, is not synchronous with the day-night alternation; for several species, an increase of the feeding activity is evident as early as 14.00 hrs, i.e., long before the nocturnal ascent of animals toward the surface, when they are still concentrated in the 300 to 600 m water layer. By integrating the data for 9 species, it is shown that the search for food is, as a whole, most active by night (20.00 to 6.00 hrs) in the subsurface layers, but is also quite intense between 14.00 and 20.00 hrs in intermediate and deep layers (300 to 600 m). 相似文献
239.
Characteristics of Resuspension,Settling and Diffusion of Particulate Matter in a Water Column 总被引:1,自引:0,他引:1
Michael?Belinsky Hillel?Rubin Yehuda?AgnonEmail author Eliezer?Kit Joseph?F.?Atkinson 《Environmental Fluid Mechanics》2005,5(5):415-441
Experiments were conducted in order to characterize the distributions of concentrations of suspended particulate matter (SPM)
in water columns of lakes and reservoirs. The experiments, in a reduced model of the water column, used a set of oscillating
grids. Runs were done with particles denser than water as well as with light particles. The results were in good agreement
with analytical solutions for steady-state, and non-steady-state conditions. An approximate analytical solution was derived
and found to be in agreement with the full solution. The threshold for resuspension was measured, and characterized in terms
of a modified Shields parameter, which is appropriate to a zero-shear environment. All experiments showed that the distribution
of SPM exhibited a layer near the bottom that is thought to be analogous to the benthic nepheloid layer (BNL) observed in
larger lakes. The thickness of the nepheloid layer increases with the turbulence intensity. 相似文献
240.
Andrew S. Cohen Roger Bills Christine Z. Cocquyt A.G. Caljon 《Conservation biology》1993,7(3):667-677