全文获取类型
收费全文 | 1426篇 |
免费 | 112篇 |
国内免费 | 304篇 |
专业分类
林业 | 56篇 |
农学 | 63篇 |
基础科学 | 391篇 |
385篇 | |
综合类 | 734篇 |
农作物 | 21篇 |
水产渔业 | 36篇 |
畜牧兽医 | 104篇 |
园艺 | 12篇 |
植物保护 | 40篇 |
出版年
2024年 | 80篇 |
2023年 | 203篇 |
2022年 | 229篇 |
2021年 | 172篇 |
2020年 | 136篇 |
2019年 | 116篇 |
2018年 | 57篇 |
2017年 | 37篇 |
2016年 | 46篇 |
2015年 | 40篇 |
2014年 | 54篇 |
2013年 | 57篇 |
2012年 | 73篇 |
2011年 | 80篇 |
2010年 | 67篇 |
2009年 | 63篇 |
2008年 | 67篇 |
2007年 | 55篇 |
2006年 | 34篇 |
2005年 | 37篇 |
2004年 | 27篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有1842条查询结果,搜索用时 593 毫秒
101.
《Scandinavian Journal of Forest Research》2012,27(8):784-796
Corporate social responsibility (CSR) has been a topic of interest to both practitioners and researchers in the forest products sector. However, the existing literature falls short of examining the connections between CSR implementation and firm cultures, a key link to further our understanding for CSR implementation. This current study investigates the relationship between firm cultures and CSR implementation in the global forest, paper & packaging industry companies. Specifically, the authors propose firm cultures, including market orientation, learning orientation and innovativeness potentially support CSR implementation. Also, innovativeness is proposed to mediate the market orientation-CSR and learning orientation-CSR relationships. Data are collected through a mail survey with responses from 58 companies (87 individuals) of the Top 100 global forest, paper & packaging industry companies, identified by PricewaterhouseCoopers in its 2008 Global Forest, Paper & Packaging Industry Survey. Results confirm the hypothesized relationships between market orientation and CSR and learning orientation and CSR. However, the proposed mediating effect of innovativeness is not significant. 相似文献
102.
随着计算机技术和网络技术的发展,传统的计算机辅助教学(CAI)手段与Internet技术的有机 结合,产生了CAI的新形式—基于Internet的分布式CAI,我国对此研究尚处于初级阶段。主要对 这种新形势下的CAI-I课件与传统的CAI课件的特点加以分析和比较,并简要介绍其实现方法。 相似文献
103.
To establish the sublethal concentrations domain, acute and chronic oral tests were conducted on caged honeybee workers (Apis mellifera L) using imidacloprid and a metabolite, 5-OH-imidacloprid, under laboratory conditions. The latter showed a 48-h oral LD50 value (153 ng per bee) five times higher than that of imidacloprid (30 ng per bee). Chronic feeding tests indicated that the lowest observed effect concentrations (LOEC) of imidacloprid and of 5-OH-imidacloprid on mortality of winter bees were 24 and 120 microg kg(-1) respectively. Behavioural effects of imidacloprid and 5-OH-imidacloprid were studied using the olfactory conditioning of proboscis extension response at two periods of the year. Winter bees surviving chronic treatment with imidacloprid and 5-OH-imidacloprid had reduced learning performances. The LOEC of imidacloprid was lower in summer bees (12 microg kg(-1)) than in winter bees (48 microg kg(-1)), which points to a greater sensitivity of honeybees behaviour in summer bees, compared to winter bees. 相似文献
104.
Hymenopterous parasitoids play an important role in the control of insect populations. During oviposition, Hymenopterous parasitoids use cues such as odours from their environment to locate their specific host. Leptopilina heterotoma (parasitoid of Drosophila larvae) locate their host by probing the substrate with the ovipositor. This behaviour can be induced by the odour of the host substrate alone. We analysed the sub-lethal effects of chlorpyrifos at LD20 on the probing activity in response to a fruit odour (banana). The insecticide increased the percentage of females spontaneously probing in response to the odour. Parasitoid females were then conditioned to associate banana odour with the oviposition in host larvae. This conditioning enables parasitoids to memorize the odour and to increase their probing response to this odour. During the olfactory conditioning, females exposed to the insecticide found and oviposited in host larvae more quickly than control females. One hour after the olfactory conditioning, females exposed to the insecticide presented a higher increase of their probing response to the odour than controls. Twenty-four hours after conditioning, the stimulation produced by chlorpyrifos was no longer perceptible, but the level of response of conditioned females was still higher than that of non-conditioned females, showing that odour memory was not impaired by the insecticide treatment. These sub-lethal effects, that stimulate host searching by parasitoids without impairing odour memorization, could increase their parasitic efficiency. 相似文献
105.
金华 《四川畜牧兽医学院学报》2007,5(2):113-115
大学英语的教学目标是培养学生的英语综合运用能力,特别是听说能力。针对目前大学英语听说课中存在的实际问题,文章将以建构主义学习理论为基础探讨如何改进大学英语听说教学。 相似文献
106.
As Forest School has become more widespread throughout Britain an understanding is needed of its impact. This paper outlines a two-phase evaluation project undertaken in Wales and England from 2002 to 2005. The evaluation was undertaken through a partnership between Forest Research and the New Economics Foundation. A methodology was developed to explore the impacts of Forest School on children and this was then used to track changes in 24 children at three case study areas over an 8-month period. The research highlights that children can benefit in a range of ways. Six themes emerged from the data of the positive impacts on children in terms of confidence, social skills, language and communication, motivation and concentration, physical skills and knowledge and understanding. Two further themes highlight the wider impacts of Forest School on teachers, parents, and the extended family. Contact with the natural environment can be limited for children and young people in contemporary society due to concerns about safety outdoors and issues of risk and liability. Forest School provides an important opportunity for children to gain access to and become familiar with woodlands on a regular basis, while learning academic and practical skills. The constructivist theory of learning seems to be particularly suited to the Forest School approach as children make meaning from their direct experiences. The participatory action research approach taken in this study promoted reflective practice amongst the stakeholders involved and provided them with a sense of ownership of the study, as well as an opportunity to learn from each other. 相似文献
107.
Public participation is crucial for sustainable forest management. In particular, in urban forest areas, it is an important tool for overcoming conflicts among diverse needs regarding the forests through collaboration between citizens and governments. Such collaboration requires social learning. Social learning is dependent upon the presence of social networks that serve as an infrastructure for social capital. This study analyses the role of the social network in a participatory forest management approach of the Nopporo Forest Regeneration Project (NFRP) in the urban Nopporo National Forest in Hokkaido, northern Japan, aimed at restoring a typhoon damaged forest.Within the framework of the participatory approach the project hascreated a network of several citizen organizations for exchanging information. Outside this formal NFRP network several additional citizenorganizations are concerned about the Nopporo Forest management. The article describes the overall social network that has evolved around the Nopporo Forest and compares the attitudes and evaluations of the NFRP network organizations and the not formally NFRP related organizations towards their collaboration with government agencies and other citizen organizations. The overall social network around the Nopporo Forest had a multi-nodal character with the National Forest Agency and Hokkaido Prefectural Government acting as main central nodes. Only a few citizen organizations had direct relations to both central nodes; many organizations had links to either the National Forest Agency or the Prefectural Government. The organizations involved in the formal NFRP network had close ties with the National Forest Agency. This contributed to a positive evaluation of present forest management approach and the collaborative activities of the government agencies. In contrast, the organizations that were not involved in the formal NFRP network were found to have fewer ties with the National Forest Agency. The lack of opportunity to form a direct social learning relation hindered the formation of social capital and resulted in a lower evaluation of the participatory management approach as well as of the collaborative activities. Thus, although the participatory forest management approach of establishing formal social networks enhanced collaboration between the National Forest Agency and several citizen organizations and social learning, it was less successful in encouraging a democratic process involving all interested citizen organizations. 相似文献
108.
109.
在解读体验学习基本理论模型和基本特征的基础上,探析了体验学习在网络工程教学实践中的应用,主要包括网络工程教学过程中开展体验学习的基本流程及其常用的活动形式。 相似文献
110.
数学学法指导是数学教学理论研究和实践中的一个重要课题。结合教学实践,对数学学法指导的意义、指导的内容、指导的原则及指导的实施四个方面进行了探讨。 相似文献