全文获取类型
收费全文 | 596篇 |
免费 | 3篇 |
国内免费 | 20篇 |
专业分类
安全科学 | 16篇 |
废物处理 | 15篇 |
环保管理 | 38篇 |
综合类 | 181篇 |
基础理论 | 177篇 |
环境理论 | 4篇 |
污染及防治 | 149篇 |
评价与监测 | 16篇 |
社会与环境 | 21篇 |
灾害及防治 | 2篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 24篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 32篇 |
2012年 | 21篇 |
2011年 | 30篇 |
2010年 | 22篇 |
2009年 | 19篇 |
2008年 | 23篇 |
2007年 | 32篇 |
2006年 | 34篇 |
2005年 | 23篇 |
2004年 | 10篇 |
2003年 | 19篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 21篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1983年 | 6篇 |
1969年 | 3篇 |
1966年 | 7篇 |
1965年 | 4篇 |
1964年 | 8篇 |
1963年 | 7篇 |
1961年 | 5篇 |
1960年 | 6篇 |
1959年 | 3篇 |
1958年 | 3篇 |
1957年 | 6篇 |
1956年 | 3篇 |
1955年 | 5篇 |
1954年 | 4篇 |
1953年 | 7篇 |
排序方式: 共有619条查询结果,搜索用时 15 毫秒
561.
562.
563.
564.
565.
This article investigates the variations of nutrient (phosphorus (P) and potassium (K)) and heavy metal contents in soils. Therefore, selected regions in Eifel and Hunsrueck (region around Trier) were examined. The data base consists of more than 100.000 existing measurements plus own investigations on the main land use classes —field, grassland, vinicultural areas and forest—with regard to their intensities (conventional und biological). The evaluation of the nutrient contents for P and K was made using the manual adequate fertilization for field and grassland. The creation of heavy metal distribution maps is based on the Kriging method. In the past, soils in the region of Trier received a too large amount of P and K—especially in vinicultural areas. Mineral and organic fertilization has a great influence on the heavy metal contents on farmland. The immission of dust contaminated with heavy met|als is important on forest and grassland locations. On vineyards the use of cupreous plant protection agents is critical. The land use classes have had a substantial influence on the nutrient and heavy metal contents of the soil. In contrast to this, the intensities showed less differences. In order to reduce the anthropogenic impact on heavy metals in soils, it is necessary to create specific reduction strategies for each land use class. For example the fertilization has to be limited to the need of the plant, contaminated secondary raw material fertilizer has to be avoid the comparability of analytical methods has to be ensured. 相似文献
566.
Barbara L. Peckarsky Angus R. McIntosh Christopher C. Caudill Jonas Dahl 《Behavioral ecology and sociobiology》2002,51(6):530-537
Large size often confers a fitness advantage to female insects because fecundity increases with body size. However, the fitness benefits of large size for male insects are less clear. We investigated the mating behavior of the mayfly Baetis bicaudatus to determine whether the probability of male mating success increased with body size. Males formed mating aggregations (swarms) ranging from a few to hundreds of individuals, 1-4 m above the ground for about 1.5-2 h in the early morning. Females that flew near swarms were grabbed by males, pairs dropped to the vegetation where they mated and then flew off individually. Some marked males returned to swarms 1, 2 or 3 days after marking. Larger males swarmed near spruce trees at the edges of meadows, but the probability of copulating was not a function of male body size (no large male advantage). Furthermore, the potential fitness advantage of mating with larger, more fecund females was not greater for large males (no size-assortative mating). However, the sizes of copulating males were significantly less variable than those of non-mating males collected at random in swarms. Intermediate male size may be optimal during mating because of trade-offs between flight agility and longevity or competitive ability. Results of this study are consistent with the hypotheses that there is stabilizing selection on adult male body size during mating, and that male body size in this species may be influenced more by selection pressures acting on larvae than on adults. 相似文献
567.
Robert J. Paxton Nicole Weißschuh Wolf Engels Klaus Hartfelder J. Javier G. Quezada-Euan 《Die Naturwissenschaften》1999,86(3):143-146
Queens of the large, pantropical and fully eusocial taxon Meliponinae (stingless bees) are generally considered to be singly
mated. We indirectly estimated queen mating frequency in two meliponids, Melipona beecheii and Scaptotrigona postica, by examining genotypes of workers at microsatellite DNA loci. Microsatellites were highly variable, providing suitable markers
with which to assign patrilinial origin of workers within colonies headed by single queens. Queen mating frequency varied
between 1 and 3 (M. beecheii) and 1 and 6 (S. postica), representing the first clear documentation of polyandry in the Meliponinae. Effective paternity frequency, m
e
, was lower, although above 2 for S. postica. Stingless bees may provide suitable subjects for the testing of recent inclusive fitness arguments describing intracolony
kin conflict in social Hymenoptera.
Received: 26 August 1998 / Accepted in revised form: 18 November 1998 相似文献
568.
569.
Water pumping by means of wind and solar energy becomes more and more attractive by reason of increasing energy prices. Water supply for remote villages especially in developing countries needs hydraulic energy of about 1 to 50 kWh per day. The use of renewable energies like solar and wind seems to be technically successfull and has a good chance to be competitive with conventional energy sources like diesel or electricity in regions with mean wind speeds above 4–5 m/s or high insolation of about 5 kWh/day annual average. 相似文献
570.