全文获取类型
收费全文 | 1150篇 |
免费 | 164篇 |
国内免费 | 143篇 |
专业分类
安全科学 | 550篇 |
废物处理 | 12篇 |
环保管理 | 118篇 |
综合类 | 298篇 |
基础理论 | 282篇 |
环境理论 | 2篇 |
污染及防治 | 50篇 |
评价与监测 | 6篇 |
社会与环境 | 77篇 |
灾害及防治 | 62篇 |
出版年
2024年 | 2篇 |
2023年 | 38篇 |
2022年 | 57篇 |
2021年 | 67篇 |
2020年 | 78篇 |
2019年 | 87篇 |
2018年 | 51篇 |
2017年 | 74篇 |
2016年 | 79篇 |
2015年 | 53篇 |
2014年 | 48篇 |
2013年 | 75篇 |
2012年 | 92篇 |
2011年 | 67篇 |
2010年 | 62篇 |
2009年 | 62篇 |
2008年 | 62篇 |
2007年 | 63篇 |
2006年 | 51篇 |
2005年 | 39篇 |
2004年 | 40篇 |
2003年 | 39篇 |
2002年 | 21篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 14篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有1457条查询结果,搜索用时 62 毫秒
221.
222.
江苏省农户秸秆还田的影响因素分析 总被引:3,自引:0,他引:3
农户秸秆还田不仅有利于土壤有机质的增加,实现耕地的可持续利用,而且在发挥我国农田土壤固碳潜力,积极应对气候变化方面具有重要意义.文章以江苏省农户调查数据为基础,建立Logistic模型,对影响农户秸秆还田的因素进行分析,以期为制定促进农户秸秆还田的政策提供科学依据.结果表明,不同地区农户对于秸秆还田的决策存在差异:在较为发达地区,秸秆还田与否,农户更多的是从秸秆处理的边际成本出发;而略欠发达地区,则主要是基于秸秆的利用效益.此外,技术因素也影响农户秸秆还田的行为决策.在制定促进秸秆还田技术应用的激励政策时,要充分考虑地区农业生产以及农户生产经营的基本特征及差异,因地制宜,有效地促进秸秆还田在各地区最大限度地被应用和推广. 相似文献
223.
The driving attitudes and self-reported behaviors of New Zealand adolescents in Year 10 of school (n = 168, mean age = 14.2 years) were compared with students in Year 12 (n = 109, mean age = 16.4 years). School year group differences were found for three out of the eight measures of risky attitudes and behaviors, with the older students having riskier responses in each case. Gender differences were found for four of these measures, with males consistently demonstrating riskier attitudes. Suggestions are made about appropriate interventions and the timing of these. 相似文献
224.
Magne Friberg Namphung Vongvanich Anna-Karin Borg-Karlson Darrell J Kemp Sami Merilaita Christer Wiklund 《Behavioral ecology and sociobiology》2008,62(6):873-886
Animal courtship rituals are important for species recognition, and a variety of cues might be utilized to recognize conspecific
mates. In this paper, we investigate different species-recognition mechanisms between two sympatric butterfly sister species:
the wood white (Leptidea sinapis) and Real’s wood white (Leptidea reali). We show that males of both species frequently court heterospecific females both under laboratory and field conditions.
The long-lasting elaborate courtships impose energetic costs, since the second courtship of males that were introduced to
two subsequent conspecific females lasted on average only one fourth as long as the first courtship. In this paper, we demonstrate
that premating reproductive isolation is dependent on female unwillingness to accept heterospecific mates. We studied female
and male courtship behavior, chemical signaling, and the morphology of the sexually dimorphic antennae, one of the few male
traits visible for females during courtship. We found no differences in ultraviolet (UV) reflectance and only small differences
in longer wavelengths and brightness, significant between-species differences, but strongly overlapping distributions of male
L. sinapis and L. reali antennal morphology and chemical signals and minor differences in courtship behavior. The lack of clear-cut between-species
differences further explains the lack of male species recognition, and the overall similarity might have caused the long-lasting
elaborate courtships, if females need prolonged male courtships to distinguish between con- and heterospecific suitors. 相似文献
225.
Summary. Although terrestrial turtles have served as a model for studies of olfactory neurophysiology, little is known about how they
use chemical information in an ecological sense. We tested whether box turtles (Terrapene carolina) use chemical information to distinguish between predatory and nonpredatory mammals. Box turtles in our study exhibited more
escape behavior when exposed to urine from a predator (coyote, Canis latrans) than when exposed to urine from a nonpredator (white-tailed deer, Odocoileus virginianus) or a blank control. Escape behavior is consistent with an antipredator response. In addition, the turtles decreased their
handling time for food when in the presence of urine from either species of mammal in comparison to the blank, indicating
that chemical cues from mammals in general may result in increased vigilance by terrestrial turtles. Examination of a variety
of response variables may be important for adequate assessment of the ecological role of chemosensory behavior. 相似文献
226.
Joseph J. Nocera Philip D. Taylor Laurene M. Ratcliffe 《Behavioral ecology and sociobiology》2008,62(11):1769-1777
Migrating animals face numerous mortality risks, such as novel predators with which they may not be accustomed. Most animals
can recognize predators innately; however, additional predator information can be collected to enhance familiarity. Because
migrating birds rarely participate in mobs, they may seek alternative information sources such as cues provided by other birds
that can provide information on predator location, identity, and degree of threat. We predicted that Nearctic–Neotropical
migrants (hereafter, “migrants”) would react to vocal antipredator cues (e.g., mob-calls) of species residing in areas through
which they migrate. To test this, we conducted experiments in Belize during spring migration, using playbacks of mob-calls
of black-capped chickadees (Poecile atricapillus) and blue-gray tanagers (Thraupis episcopus); tanagers are familiar to all birds in Belize; chickadees are novel to residents but familiar to migrants. This also allowed
us to assess response to novel and out-of-context antipredator signals. Resident birds did not respond to novel chickadee
mob-calls, but did respond to familiar tanager calls. Birds overwintering south of our study area, which were migrating during
our study, responded most strongly to chickadee playbacks. Conversely, individuals of species that include our study area
in their winter range did not respond to either playback. This is the first evidence that birds react to vocal antipredator
cues during migration, which may be a strategy used by migrants to learn about predators. Although residents failed to recognize
a foreign cue, migrating birds responded most strongly to the out-of-context chickadee cue, associated with breeding grounds
>2,000 km northward.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
227.
In many salmonid species, males exhibit morphological dimorphism associated with alternative mating behaviors. ”Precocious
males” have a small body size with little or no development of sexual characters and adopt sneaking to gain access to females,
while ”migratory males” of large body size and well-developed secondary sexual characters fight. We quantified selection on
precocious male parr of masu salmon (Oncorhynchus masou) under simulated natural conditions to examine the contribution of morphology to sneaking success. In contrast to the prediction
that sneaking behavior favors small body size, we detected selection favoring relatively large body size for sneaking success.
This selection pressure was caused by the dominance hierarchy within parr and may have been facilitated by indifference of
dominant migratory males to parr. Unlike the secondary sexual characters exhibited by migratory male salmon, such as the hooked
snout and humped back, no morphological characters other than body size contributed to the reproductive success of masu salmon
parr. This non-contribution may have been responsible for the lack of development of sexual characters in precocious males.
Received: 15 November 1999 / Accepted: 20 May 2000 相似文献
228.
We examined the behavior of individual mature female Mediterranean fruit flies (medflies), Ceratitis capitata (Wiedemann), transferred from a holding cage without fruit to a clean host kumquat fruit already occupied by another medfly
female engaged in ovipositional behavior. A significantly greater proportion of transferred (=test) ovipositionally naive
females initiated ovipositor boring into a fruit in the presence than in the absence of an occupying medfly. Moreover, test
females commenced boring significantly sooner in the presence than in the absence of another medfly. Interestingly, similar
results occurred when a test medfly was transferred to a kumquat occupied by an ovipositing female oriental fruit fly, Bactrocera dorsalis Hendel. In contrast, there was no enhancement of propensity to bore when a test medfly was transferred to a kumquat occupied
by a female Biosteres arisanus (Sonan), a parasitoid attacking medfly eggs. The principal proximate stimulus giving rise to the higher tendency to oviposit
of a test medfly in the presence of an occupying medfly or oriental fruit fly appeared to be wing-waving by the occupant during
an encounter. We consider our findings to be good evidence of socially facilitated ovipositional behavior in ovipositionally
naive medflies, and suggest that such females may benefit from acquisition of a cue demonstrating the acceptability of a host
for oviposition.
Received: 7 July 1997 / Accepted after revision: 30 August 1997 相似文献
229.
230.
目前,钢混凝土组合梁由于其具有截面高度小、自重轻、延性好等优点而广泛应用于高层建筑和桥梁结构中。钢混凝土组合梁中,钢梁和混凝土板通过剪力连接件共同作用,钢混凝土组合梁的性能很大程度上依赖于剪力连接件的性能,因此剪力连接件是组合梁中的关键部位。栓钉是目前最常用的柔性剪力连接件。本文采用有限元软件ABAQUS,较系统地研究了高温下组合梁中栓钉破坏形态、破坏机理、抗剪承载力和荷载—滑移规律性能,为高温下组合梁抗火性能研究提供基础。模型中混凝土、栓钉和钢梁采用实体单元模拟,材料的力学特性和热工特性参数根据欧洲规范(EN 1994-1-2)。本文先用文献中的试验结果验证了数值模型的可靠性,并进一步研究了不同栓钉直径和不同混凝土强度等级时的高温下栓钉承栽力折减系数。研究表明,欧洲规范中高温下栓钉承栽力的计算公式是合理的,能较准确地预测栓钉在高温下的承栽力。 相似文献