全文获取类型
收费全文 | 3672篇 |
免费 | 63篇 |
国内免费 | 33篇 |
专业分类
安全科学 | 204篇 |
废物处理 | 132篇 |
环保管理 | 963篇 |
综合类 | 332篇 |
基础理论 | 902篇 |
环境理论 | 7篇 |
污染及防治 | 830篇 |
评价与监测 | 234篇 |
社会与环境 | 134篇 |
灾害及防治 | 30篇 |
出版年
2023年 | 18篇 |
2022年 | 23篇 |
2021年 | 28篇 |
2020年 | 30篇 |
2019年 | 35篇 |
2018年 | 44篇 |
2017年 | 66篇 |
2016年 | 90篇 |
2015年 | 73篇 |
2014年 | 79篇 |
2013年 | 461篇 |
2012年 | 137篇 |
2011年 | 181篇 |
2010年 | 120篇 |
2009年 | 135篇 |
2008年 | 162篇 |
2007年 | 201篇 |
2006年 | 138篇 |
2005年 | 126篇 |
2004年 | 131篇 |
2003年 | 134篇 |
2002年 | 112篇 |
2001年 | 73篇 |
2000年 | 81篇 |
1999年 | 52篇 |
1998年 | 56篇 |
1997年 | 44篇 |
1996年 | 64篇 |
1995年 | 57篇 |
1994年 | 67篇 |
1993年 | 56篇 |
1992年 | 48篇 |
1991年 | 39篇 |
1990年 | 39篇 |
1989年 | 33篇 |
1988年 | 40篇 |
1987年 | 31篇 |
1986年 | 35篇 |
1985年 | 34篇 |
1984年 | 31篇 |
1983年 | 40篇 |
1982年 | 49篇 |
1981年 | 47篇 |
1980年 | 25篇 |
1979年 | 30篇 |
1978年 | 25篇 |
1977年 | 30篇 |
1976年 | 14篇 |
1974年 | 11篇 |
1972年 | 11篇 |
排序方式: 共有3768条查询结果,搜索用时 15 毫秒
151.
152.
The future supplies of iron ore, coking coal and ferrous scrap are discussed. There is no likelihood of the resources of iron ore being exhausted until well into the twenty-first century. Coking coal, on the other hand, is in shorter supply but it is being eked out by blending with non-coking coal and by making blast furnaces more efficient. Briquettes made completely from non-coking coal will play a part in iron making in the future. To ensure greater flexibility in steel making, hydrocarbons are being considered as possible substitutes for coal. Scrap has always played an important part in steel making and the amount recycled is increasing every year. But more effort is needed, for example, to ensure that the steel in car scrap is fully utilised and that refuse is efficiently recycled. Steel making increasingly demands the scrap to have few impurities and to be in uniform sized pieces. A cryogenic method of preparing such scrap is described. A futuristic way of extracting iron, non-ferrous metals and other saleeable by-products from refuse, by using redundant blast furnaces, is also discussed. 相似文献
153.
154.
Robert L. Wilbur 《Journal of the American Water Resources Association》1974,10(2):372-383
ABSTRACT: Conversion of muck to sand bottom was tested to increase benthic production in two eutrophic Florida lakes, and preliminary results indicate that benthos will be increased in areas converted to sand. Muck removal with a specially designed dredge, or “Mudcat,” was tested in Trout Lake. The Mudcat removed 41,650 cu. yds. of muck and exposed 17 acres of sand bottom, but 10 of those acres developed thin layers of muck, which proved too soft to be picked up by the Mudcat. Consequently, only 7 acres were satisfactorily converted. Bottom redistribution with a suction-type dredge was tested in Lake Carlton, and 14 acres were converted from muck to sand. Sand covered with muck was pumped from midlake areas to more peripheral areas of the lake where water depths were 11 to 13 feet and muck layer about 1.5 feet deep. The bottom was built up to an elevation above the previous muck elevation. Several methods for depositing the sand were tested. Level areas of sand fill developed accumulations of muck from fallout following dredging activity. Piles or dunes provided the best cost-return ratio. The bottom in filled areas changed very little during a 1½ year period following filling. 相似文献
155.
Terrie K. Boguski Robert G. Hunt William E. Franklin 《Resources, Conservation and Recycling》1994,12(3-4)
Life cycle inventory (LCI) is becoming more widely used as a tool to evaluate the resource and energy use and the environmental releases associated with various products. The methodology for handling different recycling scenarios is also becoming increasingly important. Several different methods exist for handling recycling in an LCI. The method described in this paper uses mathematical models to show that the same basic equations can be used to handle a variety of recycling options for multi-product systems. 相似文献
156.
Gilad Heinisch Aldo Corriero Antonio Medina Francisco J. Abascal Jose-Miguel de la Serna Robert Vassallo-Agius Antonio Belmonte Ríos Antonio García Fernando de la Gándara Christian Fauvel Christopher R. Bridges Constantinos C. Mylonas Saadet F. Karakulak Isik Oray Gregorio De Metrio Hanna Rosenfeld Hillel Gordin 《Marine Biology》2008,154(4):623-630
Atlantic bluefin tuna (BFT; Thunnus thynnus) is a migrating species straddling the North Atlantic Ocean and Mediterranean Sea. It is assumed that this species is divided
into a western and an eastern stock, which spawn in the Gulf of Mexico and the Mediterranean Sea, respectively. To learn more
about the reproductive behavior of the eastern BFT stock, we tracked gonadal development in adult fish that were sampled between
April and July during three consecutive years (2003–2005). Sampling campaigns were carried out using common fishing methods
at selected locations within the Mediterranean Sea, namely Levantine Sea, Malta, and Balearic Islands. An additional sampling
point, Barbate, was situated northwest of the Straits of Gibraltar along the Atlantic coast. Morphometric parameters such
as the total body mass (M
B) and the weights of the gonads (M
G) were recorded, and the respective gonadosomatic index (GSI) values were calculated. The data collected revealed two important
trends: (1) GSI values are higher in fish caught in the eastern rather than the western locations across the Mediterranean
Sea, and (2) the GSI reaches maximum values between late May and early June in Levantine Sea (eastern Mediterranean Sea),
and only 2 and 4 weeks later in the central (Malta) and western (Balearic Islands) locations, respectively. The advanced gonadal
development in BFT correlates well with higher sea surface temperatures. Our findings also distinguish the northern Levantine
Sea BFT population (mean M
B 78.41 ± 4.13 kg), and the Barbate BFT population with the greatest M
B (all fish sampled > 100 kg). These data reflect a situation in which the eastern Mediterranean basin may function as a habitat
for young BFT, until they gain a larger M
B and are able to move to the Atlantic Ocean. However, the existence of genetically discrete BFT populations in the Mediterranean
Sea cannot be ruled out. 相似文献
157.
158.
The authors present an economic justification for extramarket intervention in the markets for secondary materials and briefly discuss the possible impacts of futures trading on the cash market for a commodity. These impacts are applied to the markets for secondary materials and the potential effects are assessed. They conclude with a rationale for public participation in initiating a scrap futures market. 相似文献
159.
Giloteaux L Solé A Esteve I Duran R 《Environmental science and pollution research international》2011,18(7):1147-1159
Introduction
A Microcoleus sp. consortium, obtained from the Ebro delta microbial mat, was maintained under different conditions including uncontaminated, lead-contaminated, and acidic conditions. 相似文献160.
Recreational impact was measured on eight beaches in Glen Canyon National Recreation Area and 15 beaches in Grand Canyon National Park using permanently located transects and plots. Recreational impact indices included densities of human trash and charcoal and a measure of sand discoloration due to charcoal. Significant increases in the indices occurred on several Glen Canyon beaches over a seven-month period. Sand discoloration became significantly higher over all Glen Canyon beaches during the same time period. All indices were significantly higher in Glen Canyon than on similar Grand Canyon beaches. These differences are probably due to differences in: (a) level of impacts tolerated by the respective management regimes and, (b) in the number of user days among the two National Park Service administrative units. Management alternatives are presented for reversing the present trends of recreational impact on Glen Canyon beaches. 相似文献