首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   726篇
  免费   68篇
  国内免费   130篇
安全科学   90篇
废物处理   26篇
环保管理   160篇
综合类   334篇
基础理论   125篇
污染及防治   56篇
评价与监测   26篇
社会与环境   86篇
灾害及防治   21篇
  2024年   4篇
  2023年   8篇
  2022年   32篇
  2021年   28篇
  2020年   32篇
  2019年   35篇
  2018年   29篇
  2017年   40篇
  2016年   40篇
  2015年   35篇
  2014年   29篇
  2013年   56篇
  2012年   49篇
  2011年   70篇
  2010年   36篇
  2009年   48篇
  2008年   32篇
  2007年   61篇
  2006年   48篇
  2005年   32篇
  2004年   25篇
  2003年   24篇
  2002年   20篇
  2001年   21篇
  2000年   18篇
  1999年   12篇
  1998年   10篇
  1997年   7篇
  1996年   8篇
  1995年   4篇
  1994年   7篇
  1993年   1篇
  1992年   4篇
  1991年   1篇
  1988年   2篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1981年   1篇
  1980年   3篇
  1978年   1篇
  1977年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有924条查询结果,搜索用时 15 毫秒
101.
Purpose. The aim was to adjust the positive health behaviours scale (PHBS) to make it suitable for use by nurses, and to validate the new version of the tool. Methods. A previously formulated PHBS was modified. The scale comprises 29 statements describing certain positive health behaviours in four subscales: nutrition, physical activity, relaxation and behaviours related to mental health, and preventive behaviours. The scale was enriched with items on avoiding risky behaviours and a question regarding respondents’ own assessment of their care for health. Analyses were conducted of reliability, construct validity, criterion validity and dimensionality of subscales. The questionnaire was completed by 1017 nurses. Results. Cronbach's α reached 0.844 for the entire scale and 0.623–0.761 for specific subscales. Empirical data did not confirm theoretical assumptions regarding the existence of a four-element structure of the PHBS. The scale's diagnostic criteria were validated on the basis of positive results of correlation and trend analysis. Only one of the subscales proved homogeneous and could be considered unidimensional. Conclusions. The results confirmed the high internal consistency of the scale and its subscales. The factor structure of the PHBS was equivocal. The PHBS could be used in workplace-based health promotion programmes designed for nurses.  相似文献   
102.
Group foraging allows the co-existence of a strategy (producer) that involves searching for food, and its alternative (scrounger) exploiting the food of the producer. The use of producer and scrounger strategies has been modelled as an alternative-option scramble which assumes strong negative frequency-dependence of the scrounger's pay-offs. We tested this assumption in a flock feeding situation by manipulating the proportion of scroungers in flocks of spice finches, Lonchura punctulata. In a first experiment we found that: (1) the food intake of scroungers, and to a lesser extent producers, was negatively affected by an increase in the proportion of scroungers; (2) the food intake of producers and scroungers was equal when the proportion of scroungers was small, suggesting that producers, who exploited 35.4% of their patches by scrounging were opportunistically adjusting their use of the strategies until the pay-offs equalized. In a second experiment we tested whether finches could vary their use of the two strategies in response to changes in foraging conditions brought about by an increase in the cost of producing. As predicted by the game, finches reduced their use of the producer strategy and increased their use of the scrounger strategy when the cost of producing increased. These results suggest that spice finches can alter their allocation to each foraging alternative by experience and that the producer-scrounger game is a realistic model for predicting group foraging decisions. Correspondence to: L.-A. Giraldeau  相似文献   
103.
大空间尺度上物种多样性的分布规律   总被引:5,自引:0,他引:5  
物种多样性是生物多样性在物种水平上的表现形式.由于全球性保护行动的开展和多学科的相互渗透,把物种多样性研究推向大时空尺度方向发展,一些新的研究领域得到拓展.本文综述了物种多样性在大空间尺度上的经典研究(包括梯度变化格局、个体大小频次分布格局和物种-面积关系),同时着重探讨了经典研究的新认识及一些新领域内所揭示的新格局,主要有:生物类群间物种数的协同变化、物种和高级分类阶元的关系、局域物种多样性与区域物种多样性关系以及全球变化影响等等.参79  相似文献   
104.
Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources. White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together, these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness.  相似文献   
105.
106.
Rethinking Community-Based Conservation   总被引:34,自引:0,他引:34  
Abstract:  Community-based conservation (CBC) is based on the idea that if conservation and development could be simultaneously achieved, then the interests of both could be served. It has been controversial because community development objectives are not necessarily consistent with conservation objectives in a given case. I examined CBC from two angles. First, CBC can be seen in the context of paradigm shifts in ecology and applied ecology. I identified three conceptual shifts—toward a systems view, toward the inclusion of humans in the ecosystem, and toward participatory approaches to ecosystem management—that are interrelated and pertain to an understanding of ecosystems as complex adaptive systems in which humans are an integral part. Second, I investigated the feasibility of CBC, as informed by a number of emerging interdisciplinary fields that have been pursuing various aspects of coupled systems of humans and nature. These fields—common property, traditional ecological knowledge, environmental ethics, political ecology, and environmental history—provide insights for CBC. They may contribute to the development of an interdisciplinary conservation science with a more sophisticated understanding of social-ecological interactions. The lessons from these fields include the importance of cross-scale conservation, adaptive comanagement, the question of incentives and multiple stakeholders, the use of traditional ecological knowledge, and development of a cross-cultural conservation ethic.  相似文献   
107.
We examined the preference of Atlantic molly females (Poecilia mexicana) to associate with a well-fed or a starved male in simultaneous choice tests. Females from three different populations were tested in three treatments: (1) the females could choose on the basis of multiple cues from the males (visual plus non-visual); (2) only non-visual cues could be perceived in darkness, (3) only visual cues were presented. The three tested populations differ clearly in their ecology: one population occurs in a typical river habitat, the second one in a milky sulfur creek outside a cave, and the third population occurs in a cave habitat (cave molly). In the river-dwelling population, females never showed a preference. In the population from the sulfur creek, females preferred to associate with the well-nourished male when visual cues from the males were available. Only cave molly females exhibited a strong preference for well-nourished males in all treatments. A morphological comparison demonstrated that wild-caught males from river habitats are typically in a good nutritional state. In the sulfur creek, males showed signs of starvation. Cave molly males were in an even worse nutritional state. In the cave population, saturated males probably indicate high fitness, thereby driving the evolution of the preference for good male nutritional state.Communicated by K. Lindström  相似文献   
108.
历史时期黄河下游河道演变规律与淮河灾害治理   总被引:9,自引:0,他引:9  
王庆 《灾害学》1998,13(1):57-61
历史时期黄河下游河道演变规律表明,河流从沿程淤积到河口延伸、再到溯源淤积的自适应过程,在1000a、100a、50a、10a等各种时间尺度上均可能发生,这对淮河水系改造的可行性论证、方案设计等有重要指导意义。  相似文献   
109.
城市小区气象条件与污染扩散精细预报研究   总被引:3,自引:0,他引:3  
从城市小区气象条件与污染扩散精细预报的科研需求和城市大气环境应急响应的应用需求出发,利用新一代全球/区域同化预报系统、城市小区尺度气象和污染扩散模式以及城市尺度污染扩散模式,对城市小区气象条件与污染扩散进行了精细预报试验,并进一步研究了城市小区尺度气象和污染扩散的精细模拟对城市尺度污染扩散模拟的影响.初步建立了城市小区气象条件与污染扩散精细预报方法,即:气象部分由全球到小区逐级单向嵌套、污染部分由小区到城市逐级单向嵌套的方法.预报试验结果表明,这种方法是合理可行的.小区尺度精细模拟对城市尺度污染扩散模拟的影响较大,但其模拟效果还有待利用观测资料进一步验证.  相似文献   
110.
简要介绍了工业循环冷却水缓蚀阻垢剂的发展概况 ,阐述了低磷聚合物及新型无磷缓蚀阻垢剂的研究现状 ,并指出了今后的发展方向。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号