全文获取类型
收费全文 | 302篇 |
免费 | 34篇 |
国内免费 | 21篇 |
专业分类
安全科学 | 111篇 |
废物处理 | 6篇 |
环保管理 | 35篇 |
综合类 | 101篇 |
基础理论 | 25篇 |
污染及防治 | 15篇 |
评价与监测 | 15篇 |
社会与环境 | 26篇 |
灾害及防治 | 23篇 |
出版年
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 17篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 10篇 |
2017年 | 14篇 |
2016年 | 13篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 20篇 |
2012年 | 20篇 |
2011年 | 26篇 |
2010年 | 22篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 10篇 |
2006年 | 17篇 |
2005年 | 14篇 |
2004年 | 14篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 12篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有357条查询结果,搜索用时 31 毫秒
61.
目的 基于声发射检测原理,探究一种适用于核电安全壳的泄漏定位方法。方法 首先,开展安全壳结构的声波传播特性研究;其次,基于时频分析,对安全壳泄漏产生的声信号进行滤波预处理,基于分布式传感网络,利用互相关系数曲线,估计不同传感器信号时延;最后,采用双曲线法,对泄漏源进行定位,得到定位观测点,对观测点进行离散系数加权,得到预测泄漏源位置。结果 安全壳上波速平均值为3 026.2 m/s,泄漏声信号的频带主要集中在15~80 kHz,没有明显的时域特征。采用该方法对模拟安全壳上的泄漏源进行定位,平均定位误差为4.31 cm。结论 安全壳上周向和轴向的波速差异不大,可近似认为是各项同性的。基于离散系数加权的互相关时差法定位效果良好,满足安全壳结构泄漏定位需求。 相似文献
62.
63.
64.
Hiroe Yasui Toshiharu Akino Midori Fukaya Sadao Wakamura Hiroshi Ono 《Chemoecology》2008,18(4):233-242
Summary. We conducted a series of experiments with the white-spotted longicorn beetle Anoplophora malasiaca (Thomson), and its host plant, Citrus unshiu, to examine the origin of the sesquiterpene hydrocarbons (SHCs; including β-elemene, β-caryophyllene, α-humulene, α-farnesene,
and several unidentified compounds) that are contained in the elytra of the beetles and act as an attractant. In the laboratory,
mechanically wounded citrus branches, as well as those fed upon by A. malasiaca, attracted males more frequently than intact branches. Solid phase microextraction (SPME) and subsequent analyses by gas
chromatography (GC) analyses detected measurable SHCs from the air around both mechanically wounded and beetle-infested branches,
as well as trace amounts from intact branches. The SHCs were also detected for a certain time from beetles that had fed on
the citrus branches, but the amounts decreased rapidly after they were removed from the host. This decrease generally corresponded
with a reduction of attractiveness of the beetles in a behavioural assay. Isolated females acquired the SHCs after exposure
to, but not upon contact with, other females that had fed on C. unshiu branches. We hypothesize that the citrus SHCs are adsorbed in, retained on, and released from the wax layer of the beetle
elytra. Since these compounds are released from branches when beetles feed, they may indirectly signal the presence of beetles
to others in the field. The high response rate to SHCs by males is likely representing mate searching behavior. The SHCs act
as kairomones with a releaser effect in the communication system of A. malasiaca.
Hiroe Yasui, Toshiharu Akino, Midori Fukaya: These authors contributed equally to this article. 相似文献
65.
We develop a stochastic model for the time-evolution of scalar concentrations and temporal gradients in concentration experienced
by observers moving within inhomogeneous plumes that are dispersing within turbulent flows. In this model, scalar concentrations
and their gradients evolve jointly as a Markovian process. Underlying the model formulation is a natural generalisation of
Thomson’s well mixed condition [Thomson DJ (1987) J Fluid Mech 180:529–556]. As a consequence model outputs are necessarily
compatible with statistical properties of scalars observed in experiment that are used here as model input. We then use the
model to examine how insects aloft within the atmospheric boundary-layer can locate odour sources by modulating their flight
patterns in response to odour cues. Mechanisms underlying odour-mediated flights have been studied extensively at laboratory-scale
but an understanding of these flights over landscape scales is still lacking. Insect flights are simulated by combining the
stochastic model with a simple model of insect olfactory response. These simulations show the strong influence of wind speed
on the distributions of the times taken by insects to locate the source. In accordance with experimental observations [Baker
TC, Vickers NJ (1997) In: Insect pheromone research: new directions, pp 248–264; Mafra-Neto A, Cardé RT (1994) Nature 369:142–144],
flight patterns are predicted to become straighter and shorter, and source location is predicted to become more likely as
the mean wind speed increases. The most probable arrival time to the source decreases with the mean wind speed. It is shown
that scale-free movement patterns arising from olfactory-driven foraging stem directly from the power-law distribution of
concentration excursion times above/below a threshold level and are robust with respect to variations in Reynolds number.
Flight lengths are well represented by a power law distribution in agreement with the observed patterns of foraging bumblebees
[Heinrich B (1979) Oecologia 40(3):235–245]. 相似文献
66.
抗滑桩加固后边坡稳定性评价与桩位优化研究进展 总被引:1,自引:0,他引:1
边坡失稳是影响人类工程建设活动安全性的一类常见的地质问题,抗滑桩是边坡治理工程中常用的防治措施之一,但是目前考虑加桩后边坡的稳定性研究较少。针对抗滑桩加固后的边坡稳定性评价和抗滑桩桩位布设优化问题的研究进展进行了概述,重点综述了:抗滑柱加固边坡的稳定性分析方法,即国内外在理论计算、数值模拟和物理模型实验三方面的研究成果,并对比分析了各自的优缺点;目前常用的抗滑桩最优布设分析方法,并指出了各自的适用条件;当前边坡工程中抗滑桩桩位优化研究的现状,并对今后的发展方向进行了展望,可为今后类似研究提供一定借鉴与参考。 相似文献
67.
68.
69.
70.
Unlike other birds, shiny cowbirds (Molothrus bonariensis) must locate host nests where to lay their eggs and then decide whether to parasitise them. They should also synchronise their laying with that of the host to increase the survival of parasite egg and young. Shiny cowbirds can discover nests using host behaviour as a cue, or by searching the habitat without need for the presence of a host. Besides, they can synchronise parasitism with host laying by monitoring nests during building and laying, or directly by assessing the degree of development of embryos through the puncture of host eggs. Alternatively, synchronization can arise by lower nest attentiveness during host laying. We determined the extent of synchronization between laying of shiny cowbirds and chalk-browed mockingbirds (Mimus saturninus) and estimated if parasitism was negatively associated with host nest attentiveness. We also conducted an experiment to test if host activity was necessary to locate nests, and if puncture of host eggs was a cue for deciding parasitism. Shiny cowbirds synchronised parasitism with host laying in 75% of the cases and synchronization was not explained by lower host nest attentiveness during laying. Shiny cowbirds located nests without need for presence of a host, but the decision of parasitising the nest depended on host activity at the nest. The information that shiny cowbirds could obtain through egg punctures was not necessary for deciding parasitism. Our results indicate that shiny cowbirds rely on the precise timing of their eggs and avoid laying in unsuitable nests. 相似文献