全文获取类型
收费全文 | 248篇 |
免费 | 7篇 |
国内免费 | 3篇 |
专业分类
林业 | 39篇 |
农学 | 6篇 |
基础科学 | 39篇 |
25篇 | |
综合类 | 113篇 |
水产渔业 | 11篇 |
畜牧兽医 | 16篇 |
园艺 | 9篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 13篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 19篇 |
2013年 | 14篇 |
2012年 | 14篇 |
2011年 | 18篇 |
2010年 | 16篇 |
2009年 | 17篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有258条查询结果,搜索用时 15 毫秒
1.
Traffic has a considerable effect on population and community dynamics through the disruption and fragmentation of habitat
and traffic mortality. This paper deals with a systematic way to acquire knowledge about the probabilities of successful road
crossing by mammals and what characteristics affect this traversability. We derive a model from traffic flow theory to estimate
traffic mortality in mammals related to relevant road, traffic and species characteristics. The probability of successful
road crossing is determined by the pavement width of the road, traffic volume, traversing speed of the mammals and their body
length. We include the traversability model in a simple two-patch population model to explore the effects of these road, traffic
and species characteristics on population dynamics. Analysis of the models show that, for our parameter ranges, traffic volume
and traversing speed have the largest effect on traffic mortality. The population size is especially negatively affected when
roads have to be crossed during the daily movements. These predictions could be useful to determine the expected effectiveness
of mitigating measures relative to the current situation. Mitigating measures might alter the road and traffic characteristics.
The effects of these changes on traffic mortality and population dynamics could be analysed by calculating the number of traffic
victims before and after the mitigating measures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
褚元娟 《农业装备与车辆工程》2007,(3):33-36
轮胎印迹是轮胎在地面上滑动,摩擦生热,使轮胎橡胶产生塑性变形,并产生橡胶微粒,粘附于地面上形成的。事故现场的轮胎印迹分为三种:胎印、擦印和拖印。其中轮胎拖印是事故分析过程中最有价值的资料之一。它不仅反映了事故前后车辆的运动轨迹、轮胎状态、碰撞点的位置和制动措施,而且还可以根据印迹长度和形态分析车辆碰撞分离时刻的速度。 相似文献
3.
4.
Tamas D. Ambrisko Arnon Gal Jesus N. Sarol Ashley Mitek Christina Braun 《Veterinary anaesthesia and analgesia》2021,48(2):205-212
ObjectiveTo evaluate the influence of reservoir bag types, volumes and previous use on the peak pressures (Pmax) and the times to develop 30 cmH2O pressure (P30) within a nonrebreathing system with a closed adjustable pressure-limiting (APL) valve.Study designIn vitro study using three-way factorial design with repeated measure on one factor.SubjectsA total of 75 new anesthesia reservoir bags (five types, three volumes, five bags from each type × volume). The bag types were reusable latex (RL), disposable latex (DL) and three disposable neoprene (DN-1, DN-2 and DN-3).MethodsEach bag was tested three times (treatments): new, after prestretching and 1 week later. The bags were attached to a Bain system and anesthesia machine with closed APL valve and patient port with O2 flow 2 L minute–1 until Pmax was reached. The Pmax and time to reach P30 values were determined from recorded pressure traces. General linear mixed model analysis was used to examine the effects of bag type, volume and treatment. One-sided 95% upper prediction limits of Pmax were calculated to test the null hypothesis that predicted Pmax of new bags would be ≥ 50 cmH2O for each factor combination.ResultsRL bags were the least and DN-3 bags were the most compliant. Prestretching increased compliance in all bag types. Smaller bags of RL, DL and DN-1 were less compliant than larger ones. The predicted Pmax values were < 50 cmH2O only for DN-3 bags after prestretching. The time to reach P30 was critically low when using 0.5 L bags (median 17 seconds).Conclusions and clinical relevanceTo minimize the risk of barotrauma, highly compliant reservoir bags (e.g. DN-3) are recommended and reusable bags should be avoided. Bags should be prestretched before first use, 0.5 L bags should be avoided and fresh gas flow minimized. 相似文献
5.
采用外包角钢加固的钢筋混凝土柱,其加固效果和安全性与诸多因素,如加固设计、加固施工工艺、加固端锚固构造、加固角钢的增钢率与增箍率、原柱所处的应力状态、使用过程中的维护管理等有关。对外包钢加固钢筋混凝土柱过程中影响其加固效果和安全性的诸多因素的安全性防范措施进行了初步的分析研究和探讨。 相似文献
6.
7.
交通事故现场三维数字化信息的获取及再现 总被引:1,自引:0,他引:1
道路交通事故已成为全球共同面临的最为严重的社会公害之一,我国正处于道路交通事故高发期。交通事故现场的勘测对交通事故处理质量和深入分析事故产生的原因有着重要的影响。我们分析了现有的事故现场勘测方法的特点,介绍了利用激光扫描对交通事故现场进行三维数字化信息获取的新技术,论述了激光扫描原理、交通事故现场三维数字化信息获取和处理的过程及数据处理的常用方法,以及该技术的应用与发展趋势。 相似文献
8.
通过对牛鼻山水道自然环境以及近年来各类事故的分析比较,尝试找出事故原因规律和水道自然环境对事故发生的影响,进而提出改进安全管理的建议。 相似文献
9.
崔雷 《吉林农业科技学院学报》2009,18(3):46-48
此文章系为弄清辐射事故对公众心理的影响,充分研究怎样消除辐射事故信息带来的负面影响,使核事业稳步进展并得到公众支持而完成的。我们已经确定,公众甚至事故发生后的救援人员,往往都对“放射性泄漏”普遍存在着恐惧心理,这种负面影响若不采取相应措施予以减轻乃至消除,将极大的限制核事业的发展。经研究判断,辐射事故会对不同人群带来多种影响。针对此影响的成因与解决方案,本文给出了一些初步的研究结果。 相似文献
10.