全文获取类型
收费全文 | 611篇 |
免费 | 96篇 |
国内免费 | 62篇 |
专业分类
安全科学 | 261篇 |
废物处理 | 9篇 |
环保管理 | 132篇 |
综合类 | 197篇 |
基础理论 | 103篇 |
环境理论 | 2篇 |
污染及防治 | 18篇 |
评价与监测 | 18篇 |
社会与环境 | 15篇 |
灾害及防治 | 14篇 |
出版年
2024年 | 4篇 |
2023年 | 47篇 |
2022年 | 42篇 |
2021年 | 35篇 |
2020年 | 35篇 |
2019年 | 42篇 |
2018年 | 27篇 |
2017年 | 28篇 |
2016年 | 32篇 |
2015年 | 40篇 |
2014年 | 31篇 |
2013年 | 49篇 |
2012年 | 33篇 |
2011年 | 37篇 |
2010年 | 37篇 |
2009年 | 41篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 37篇 |
2005年 | 22篇 |
2004年 | 9篇 |
2003年 | 14篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有769条查询结果,搜索用时 15 毫秒
651.
Moukaram Tertuliano Jeffery K. Tomberlin Zeljko Jurjevic David Wilson Glen C. Rains W. J. Lewis 《Chemoecology》2005,15(2):89-95
Summary. The parasitic wasp Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) learns to associate odors with food resources and subsequently exhibits a characteristic food-seeking behavior when encountering the learned odor. Wasps so conditioned, learned and subsequently demonstrated an ability to distinguish among aflatoxigenic and non-aflatoxigenic Aspergillus flavus and A. parasiticus strains. The effects of fungal species, strain, age (5, 10-12, 20, and 30 d) and growth media (potato dextrose agar, peanut agar and corn agar) on the learning and recognition responses of the conditioned wasps were examined. The level of differentiation between fungal strains by conditioned wasps was lowest when working with 5-d-old fungal cultures but increased with age and generally peaked with 20-d-old fungi. Wasps responded generally stronger to the fungal strain conditioned to independent of growth media. This ability of parasitic wasps to learn and distinguish fungal odors can open new avenues in insect learning. 相似文献
652.
准确的绝缘节破损预测能够保证铁路运输安全和经济效益。支持向量机算法能够处理轨道电路测试数据,对其进行分类,预测可能存在隐患的绝缘节,但支持向量机预测模型的原始样本多有冗余,基于此,提出了一种基于粗糙集和支持向量机的绝缘节破损预测模型。通过改进主分量启发式属性约简算法,降低样本维数,同时选用模拟退火算法完成SVM自动参数选优。实例分析和仿真结果表明,与单一支持向量机算法相比,属性约简后的粗糙集-支持向量机算法提高了分类器的分类性能,与采用网格搜索技术的SVM预测方法相比,模拟退火算法有效提高了SVM的预测精度。 相似文献
653.
为了实现多环芳烃(PAHs)毒性的有效预测,提出应用定量构效技术对多环芳烃的空气-正辛醇分配系数(KOA)和致癌性进行预测。应用分子描述符和试验值确立构效关系,采用支持向量机算法(SVM)和人工神经网络算法(ANN)分别建立了PAHs的KOA回归预测模型和致癌性分类预测模型。利用网格划分(GS)、遗传算法(GA)、粒子群算法(PSO)对SVM进行参数寻优。应用均方误差(MSE)、拟合决定系数R2和分类准确率(Accuracy)分别对模型进行了验证与评价。结果表明,最佳回归预测模型GS-SVR的MSE为0.059 7,R2为0.913 0;最佳分类预测模型GA-SVC的Accuracy为95%。研究表明:应用SVM所建两种模型的稳定性和预测能力都优于应用ANN建立的模型;参数优化后模型的稳定性和预测能力得到了提高。 相似文献
654.
An Operational Model for Implementing Conservation Action 总被引:10,自引:0,他引:10
655.
在分析传统模压设备的动作原理(程序)的基础上.研究、开发了新型模压设备与工艺.并采用该设备与工艺用于高边墙模压鞋的开发与生产。 相似文献
656.
A. Gumbert 《Behavioral ecology and sociobiology》2000,48(1):36-43
It is usually assumed that the choice behavior of bees for floral colors is influenced by innate preferences only for the
first flower visits prior to any experience. After visits to rewarding flowers bees learn to associate their colors with a
reward. This learning process leads to an acquired preference for the trained colors that has been believed to dominate over
previous experiences and over innate preferences. This work investigates how bumble bees (Bombus terrestris) chose among artificial flowers of different colors after they had been extensively trained to other colors. The bees chose
novel colors according to their similarity to the trained color if the trained color was similar to some of the test colors.
This was true also if trained colors and test colors were well distinguished, so their color choice reflected generalization
between colors. If the test colors were so different from the trained color that no generalization took place, choice behavior
was not affected by the trained color and reflected innate preferences. The differences in choice frequencies could not be
explained by physical properties of the test colors other than the dominant wavelength, a parameter taken to reflect hue perception.
Preferred dominant wavelengths correspond to those observed in naive bumble bees and honeybees. Thus bumble bees show innate
preferences for certain colors not only prior to color learning but also after intensive learning when choosing among very
different novel colors. Color choice among similar colors, however, is controlled by generalization from the learned color.
Received: 9 November 1999 / Received in revised form: 19 March 2000 / Accepted: 31 March 2000 相似文献
657.
从某正样机的鉴定试验谈可靠性试验设计 总被引:1,自引:1,他引:0
介绍了在正样机定型质量控制过程中,强化鉴定试验可靠性设计方法研究。从编制鉴定试验大纲、方案评审、试验程序控制、试验数据分析、试验过程组织和技术能力提高等关键环节入手。确定正样机置信水平,得出正样机功能及主要性能满足战术技术指标要求。 相似文献
658.
提出了一种基于关联向量机回归的水质时间序列预测模型,并以该模型对氢离子浓度指数(p H值)、溶解氧(DO)、高锰酸盐指数(CODMn)和氨氮(NH3-N)4种重要水质指标进行预测.首先采用国家环保部发布的四川攀枝花龙洞水质自动监测数据进行实验,对该模型的有效性进行了验证;然后将关联向量机回归预测模型与支持向量机回归预测模型进行比较.为了比较不同核函数的预测效果,实验中预测模型的核函数分别采用了线性函数和高斯函数.实验结果表明,关联向量机回归模型的预测效果不亚于支持向量机回归模型;且在给出预测值时,还能同时给出预测结果的可信程度. 相似文献
659.
The relevance of the integration of preimaginal and eclosion experiences on the subsequent habitat preferences and mate finding
by the adult has been rarely tested in holometabolous insects. In this work, the effect of larval and early adult experiences
on the behavioural responses of adult males of the aphid parasitoid, Aphidius ervi, towards volatiles from the host–plant complex (HPC) and from conspecific females were evaluated. Two experience factors
were considered: host diet (normal diet=ND; artificial diet=AD), and eclosion, i.e. extraction or non-extraction of the parasitoid
larva from the parasitised aphid (extracted=EX; non-extracted=NE). Thus, four treatments were set up: ND/NE, ND/EX, AD/NE
and AD/EX. Glass Y-tube olfactometers were used to investigate the responses of adult A. ervi males to the odour sources used. Males from the ND/NE treatment showed a shorter latency to the first choice of olfactometer
arms, displayed a marked preference towards the HPC olfactometer arm, and spent more time in the HPC arm than males from the
other treatments. Only the interaction of host diet and eclosion experiences proved to be relevant in explaining the differences
in latency to first choice, time spent in olfactometers arms, and behaviours displayed in the olfactometer arms. These results
show the importance of the integration of larval and eclosion experiences in the development of stereotyped responses of the
adults. This process may involve memory retention from the preimaginal and emergence period, but further research is needed
to disentangle the contribution of each stage. The response to conspecific females was much less affected by the treatments
in relation to first arm choice and times in olfactometer arms, suggesting a pheromone-mediated behaviour, even though a prompter
and more intense wing fanning courtship behaviour was registered in the ND/NE males compared to males from the AD/NE treatment.
These results show that sexual behaviours are less affected by early experiences than behaviours related with finding a HPC
for foraging or oviposition. Taken together, our results demonstrate for first time that larval and eclosion experiences affect
in a differential way the early responses of the adult towards environment-derived cues and mate related cues. 相似文献
660.
Molly S. Cross Patrick D. McCarthy Gregg Garfin David Gori Carolyn A.F. Enquist 《Conservation biology》2013,27(1):4-13
Natural resource managers are seeking tools to help them address current and future effects of climate change. We present a model for collaborative planning aimed at identifying ways to adapt management actions to address the effects of climate change in landscapes that cross public and private jurisdictional boundaries. The Southwest Climate Change Initiative (SWCCI) piloted the Adaptation for Conservation Targets (ACT) planning approach at workshops in 4 southwestern U.S. landscapes. This planning approach successfully increased participants’ self‐reported capacity to address climate change by providing them with a better understanding of potential effects and guiding the identification of solutions. The workshops fostered cross‐jurisdictional and multidisciplinary dialogue on climate change through active participation of scientists and managers in assessing climate change effects, discussing the implications of those effects for determining management goals and activities, and cultivating opportunities for regional coordination on adaptation of management plans. Facilitated application of the ACT framework advanced group discussions beyond assessing effects to devising options to mitigate the effects of climate change on specific species, ecological functions, and ecosystems. Participants addressed uncertainty about future conditions by considering more than one climate‐change scenario. They outlined opportunities and identified next steps for implementing several actions, and local partnerships have begun implementing actions and conducting additional planning. Continued investment in adaptation of management plans and actions to address the effects of climate change in the southwestern United States and extension of the approaches used in this project to additional landscapes are needed if biological diversity and ecosystem services are to be maintained in a rapidly changing world. Acelerando la Adaptación del Manejo de Recursos Naturales para Atender el Cambio Climático 相似文献