全文获取类型
收费全文 | 22100篇 |
免费 | 114篇 |
国内免费 | 268篇 |
专业分类
安全科学 | 280篇 |
废物处理 | 1397篇 |
环保管理 | 2477篇 |
综合类 | 3000篇 |
基础理论 | 6169篇 |
环境理论 | 1篇 |
污染及防治 | 4875篇 |
评价与监测 | 1931篇 |
社会与环境 | 2280篇 |
灾害及防治 | 72篇 |
出版年
2023年 | 104篇 |
2022年 | 193篇 |
2021年 | 157篇 |
2020年 | 90篇 |
2019年 | 133篇 |
2018年 | 1621篇 |
2017年 | 1550篇 |
2016年 | 1462篇 |
2015年 | 333篇 |
2014年 | 386篇 |
2013年 | 1066篇 |
2012年 | 854篇 |
2011年 | 1870篇 |
2010年 | 1162篇 |
2009年 | 1101篇 |
2008年 | 1454篇 |
2007年 | 1785篇 |
2006年 | 519篇 |
2005年 | 480篇 |
2004年 | 474篇 |
2003年 | 515篇 |
2002年 | 505篇 |
2001年 | 573篇 |
2000年 | 367篇 |
1999年 | 212篇 |
1998年 | 135篇 |
1997年 | 134篇 |
1996年 | 149篇 |
1995年 | 175篇 |
1994年 | 149篇 |
1993年 | 139篇 |
1992年 | 145篇 |
1991年 | 147篇 |
1990年 | 140篇 |
1989年 | 118篇 |
1988年 | 119篇 |
1987年 | 125篇 |
1986年 | 104篇 |
1985年 | 101篇 |
1984年 | 118篇 |
1983年 | 112篇 |
1982年 | 105篇 |
1981年 | 86篇 |
1980年 | 76篇 |
1979年 | 76篇 |
1977年 | 64篇 |
1976年 | 62篇 |
1974年 | 65篇 |
1973年 | 70篇 |
1972年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
I Chu D C Villeneuve B McDonald V E Secours V E Valli 《Journal of environmental science and health. Part. B》1987,22(3):303-317
Pentachlorotoluene (PCT) and pentabromotoluene (PBT) are environmental contaminants detected in the Great Lakes ecosystem. In view of the paucity of toxicity data and the potential for human exposure, a subacute (28 day) and a subchronic (91 day) study were conducted in the rat. In the subacute study, groups of 10 male and 10 female rats were fed the diet containing PCT or PBT at 0, 0.5, 5.0, 50 or 500 ppm for 28-days. In the subchronic study, the group size was increased to 15, the dose levels were 0, 0.05, 0.5, 5.0, 50 and 500 ppm in the diet and the exposure period was 91 days. Growth rate and food consumption were not affected by exposure to either chemical in the subacute and subchronic study. Clinical observations revealed no abnormalities. Decreased hemoglobin was observed in female rats fed 5.0 ppm PCT and higher levels in the subacute (28 day) study. In the same study the hematocrit value and erythrocyte numbers of females fed 5.0 or 500 ppm PCT diets were significantly lower than the control. In both subacute and subchronic studies mild dose-dependent histopathological changes were observed in the thyroid, liver and kidney of rats fed PCT and PBT diets. In general male rats were more susceptible than females to the treatment of PCT and PBT. Based on these data, it was concluded that the no observable adverse effect level for PCT was 50 ppm in the diet (3.5 mg/kg b.w./day) and that of PBT was 5.0 ppm (0.35 mg/kg b.w./day). 相似文献
3.
4.
5.
E Enan I G Berberian S el-Fiki M el-Masry O H Enan 《Journal of environmental science and health. Part. B》1987,22(2):149-170
Male Baladi rabbits were acutely and sub-chronically intoxicated with cyanofenphos and profenophos. The levels of cholesterol, triglycerides, B-lipoproteins and total proteins were determined in the serum, brain, spinal cord and sciatic nerve of rabbits. Moreover, the activities of alkaline phosphatase, acid phosphatase and glutamic-pyruvic transaminase were determined in the liver of the animals. The whole studies revealed that the biochemical constituents were highly affected by the tested insecticides. Also, the liver function suffered from adverse effects of the tested insecticides. 相似文献
6.
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
7.
Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones. 相似文献
8.
When combined in the lining and covering of waste-containment facilities, soil and geosynthetic components protect the environment by acting as a hydraulic barrier. Equipment loading may significantly increase the tensile stress induced in geosynthetic components, leading to a potential stability problem. Large equipment loadings may also result in a localized circular slip surface during construction operations. New analytical method based on discrete element modelling is proposed for estimating the distribution of tensile force developed in the individual geosynthetic components of the lining system and for evaluating the safety factor of slope failure due to equipment loading. The analytical results of an example are presented to demonstrate the applicability of the analytical method for the lining system of a waste landfill. The analyses of the example show that equipment loading provide a substantial increase in the tensile forces of the geosynthetic components of a lining system and that the possibility of shallow failure due to equipment loading increases as the slope becomes steeper. This method is a useful tool for analysing the lining system of waste landfills with complex lining components. 相似文献
9.
In the past 20 years a variety of indices have been suggested for measuring the severity of trauma, however none of them meets the requirement of being a simple and objective instrument that can be utilized efficiently by lay persons and providers of health services without previous experience in triaging. A new system has been proposed which meets this requirement and which has been validated with 197 injured persons at the emergency ward of the Valle University Hospital in Call, Colombia. The instrument showed a high level of concordance with the conventional triaging method and classifies victims into four categories: critical with recovery unlikely, critical but recoverable, moderately serious, and ambulatory. There is discussion on the reliability of this instrument and it is recommended that it be validated with victims from larger disasters. Regardless, it has the advantage of being specific and free of the subjectivity that characterizes other indices. 相似文献
10.
Winer N 《Disasters》1989,13(1):1-8
Food security in Ethiopia is discussed in the context of the repeated famines and the international responses both to them and to the socialist agricultural policies being pursued by Ethiopia. Increasing concern has been expressed by the international donor community regarding the ability of Ethiopia to absorb development funds without a major shift in emphasis in agricultural policy-making. The background to Ethiopia's present vulnerability is shown both in terms of the size of the vulnerable population and in terms of the poor performance of the agricultural sector in the last decade. The author looks at the present agricultural and marketing policy reforms and questions whether they are sufficient to generate the sort of international response needed to create the level of food security that would be required to avert future famines. 相似文献