全文获取类型
收费全文 | 528篇 |
免费 | 1篇 |
国内免费 | 6篇 |
专业分类
安全科学 | 10篇 |
废物处理 | 12篇 |
环保管理 | 32篇 |
综合类 | 306篇 |
基础理论 | 80篇 |
环境理论 | 1篇 |
污染及防治 | 80篇 |
评价与监测 | 9篇 |
社会与环境 | 5篇 |
出版年
2021年 | 5篇 |
2013年 | 13篇 |
2012年 | 17篇 |
2011年 | 10篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 9篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 8篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 13篇 |
2000年 | 18篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1990年 | 11篇 |
1984年 | 5篇 |
1975年 | 5篇 |
1969年 | 6篇 |
1968年 | 6篇 |
1966年 | 6篇 |
1965年 | 6篇 |
1964年 | 6篇 |
1963年 | 9篇 |
1962年 | 6篇 |
1961年 | 11篇 |
1960年 | 13篇 |
1959年 | 9篇 |
1958年 | 13篇 |
1957年 | 8篇 |
1955年 | 11篇 |
1954年 | 6篇 |
1943年 | 5篇 |
1941年 | 5篇 |
1938年 | 5篇 |
1937年 | 4篇 |
1935年 | 4篇 |
1934年 | 4篇 |
1928年 | 5篇 |
1923年 | 6篇 |
1919年 | 5篇 |
1914年 | 6篇 |
1913年 | 5篇 |
排序方式: 共有535条查询结果,搜索用时 0 毫秒
211.
Plants as transmission channels for insect vibrational songs 总被引:6,自引:0,他引:6
Axel Michelsen Flemming Fink Matija Gogala Dieter Traue 《Behavioral ecology and sociobiology》1982,11(4):269-281
Summary The vibrational songs of several species of cydnid bugs and small cicadas (leafhoppers and planthoppers) living on various types of plants are recorded by means of laser vibrometry. The recorded vibrational songs are analysed with respect to amplitude, frequency spectrum and structure in the time domain (Figs. 2–5).The emission of vibrational songs from singing insects on plants is simulated. A small magnet is glued to the surface of the plant and moved by means of an electromagnet about one cm away (Fig. 1). The vibrations are recorded by means of laser vibrometry. The propagation velocity of the vibrations increases with the square root of frequency, i.e. in the way expected for bending waves.The mechanical properties of plants ranging from soft bean plants to stiff reeds and maples are measured. The results are used for calculating the theoretical propagation velocities of bending waves. The measured and the calculated values are rather close (Table 1). Although the mechanical properties of the plants studied vary widely, the propagation velocities at a certain frequency are of the same order of magnitude (Table 1).In all the plants studied, only little vibrational energy is lost by friction at frequencies below some kHz. Communication by means of bending waves is possible over distances of some meters. The bending waves are reflected with little loss of energy both from the root and from the top of the plant. The vibration signals may therefore travel up and down the plant several times before decaying completely (Fig. 7). The vibration at a certain spot on the plant depends not only on the distance to and nature of the emitter, but also on the modes of vibration of the plant. The amplitude of vibration does not decrease monotonically with distance from the emitter (Fig. 6).These filtering properties of the plants mean that it is essentially impossible to predict which frequencies in the signals will be amplified or attenuated in the plant at the location of the receiving animal. The vibrational signals recorded from the animals cover wide frequency bandwidths. The signals are therefore well adapted to the filtering properties of the plants, but the signals of the species studied here do not appear to be particularly adapted to specific properties of the host plants.The muscular power needed for communication by means of various types of vibrational signals is calculated. The result of this calculation supports the conclusion that the signals recorded here are carried by means of bending waves.The communication strategies open to small insects are considered. Vibrational signals appear to be an efficient means of communication, but only certain types of signals are suited, because the plants cause a considerable distortion of the signals. One kind of distortion, the dispersive property, may — in theory — be used by the listening animals to obtain information about the direction and distance to the singing animals.Dedicated to Dr. F. ossiannilsson, whose pioneering studies led to the suggestion that small insects may use plants as transmission channels for their songs 相似文献
212.
213.
214.
215.
216.
217.
218.
来自印度Adayar河的重金属:渗透进入相邻的地下水含水层 总被引:1,自引:0,他引:1
Dirk Walther Samuel Prebha Poovagounder Selvapathy Dieter Beck 《Ambio-人类环境杂志》2003,32(2):153-157
引言 Adayar河是一条很短的河流(40km长),向西南方向流去,流经Chennai(北纬13°05',东经80°15'),从这里蜿蜒曲折大约13km后汇入孟加拉湾(图1).在河口地带它变得很宽,河口宽达2km.汇水面积约有800km2,其中大多数地方地势平坦,有岩层的露头. 相似文献
219.
220.