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   62篇
  免费   1篇
林业   2篇
农学   2篇
基础科学   1篇
  5篇
综合类   34篇
农作物   1篇
水产渔业   11篇
畜牧兽医   2篇
园艺   5篇
  2024年   1篇
  2023年   2篇
  2021年   1篇
  2020年   2篇
  2019年   1篇
  2017年   1篇
  2015年   1篇
  2014年   1篇
  2013年   3篇
  2012年   7篇
  2011年   7篇
  2010年   7篇
  2009年   7篇
  2008年   1篇
  2007年   5篇
  2006年   5篇
  2005年   1篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  1998年   1篇
  1996年   2篇
  1994年   1篇
  1991年   1篇
  1988年   1篇
排序方式: 共有63条查询结果,搜索用时 15 毫秒
1.
随着高校资金总量的不断增加,以现金的方式进行结算已不能满足财务管理的需求,需要寻找出一种既安全又高效的方式予以替代。基于国内外非现金结算方面的成功经验及其与国内高校财务管理不适应的分析,构建了高校财务管理运用商务借记卡、贷记卡双卡捆绑组合的结算模式,从而既方便了高校教职工的资金使用,又提高了高校财务管理和资金支付的水平。  相似文献   
2.
Larvae of Haliotis discus hannai were induced to settle and metamorphose by exposure to seawater supplemented with bromomethane. The settlement and metamorphosis of veliger larvae were observed with bromomethane concentrations of 300, 600, 900, 1200, 1500 ppm on the benthic diatom plates. The highest settlement and metamorphosis rates of larvae were observed in bromomethane concentrations of 600 ppm.

Abalone larvae were induced to settle and metamorphose by exposure to seawater supplemented with potassium chloride. The settlement and metamorphosis of veliger larvae was observed in potassium chloride concentrations of 14, 19, 24 and 29 mM on the benthic diatom plates. The highest settlement and metamorphosis rates of larvae were observed in potassium chloride concentrations of 14–19 mM.  相似文献   

3.
This paper presents the first laboratory study investigating larval settlement and metamorphosis of Pinctada maxima in response to both natural and artificial inducers. Natural biofilms induced larval settlement and the inductive effect appears to be closely associated with the bacteria in the biofilm. This result indicates that, in nature, bacteria may play an important role in the settlement of P. maxima larvae. Various pharmacological agents were also tested in this study and the results were generally similar to those found with other marine invertebrates, particularly molluscs. The results show that some pharmacological agents are potent artificial inducers of larval settlement for P. maxima. The findings of this study provide valuable information for understanding the mechanism of the larval settlement of this species, which is useful information for the hatchery industry of this pearl oyster.  相似文献   
4.
"空心村"的出现是中国在新农村建设过程中最为普遍的问题,其不仅浪费了农村中宅基地资源,而且对村落整体环境造成了不良影响。通过对"空心村"产生的多方面因素进行分析,提出增加农村基础建设设施;调整村落中心布局;转变中心村功能;完善居住环境等规划措施,用以解决"空心村"带来的问题。  相似文献   
5.
摘要:从聚落景观研究入手,对国内乡村聚落景观研究的基础理论、研究内容、研究方法和技术以及综述聚落景观研究的主要流派等进行介绍,指出在研究方法上侧重于定性描述,采用定量分析研究少,没有形成一个很好的古村落景观研究的评价体系。  相似文献   
6.
巴蜀城镇聚落形态保护研究   总被引:4,自引:2,他引:2  
李红  周波 《安徽农业科学》2010,38(3):1583-1584
结合实例详细解读了巴蜀城镇聚落形态的特征,并针对当前城市建设给聚落形态带来的负面影响,提出尊重自然生态环境、选择空间发展模式、保护历史风貌特色、挖掘文化内涵等措施,以此实现保护城镇聚落形态的目的。  相似文献   
7.
The stabilization properties of aged refuse in five year old semi aerobic and anaerobic landfills were compared, such as volatile solid (VS), total organic carbon content (TOC), humic matters, and so on. It was found that VS and TOC content in aged refuse were obviously lower than those in fresh refuse after five years disposal. However, the VS and TOC content of aged refuse in semi aerobic landfill were slightly lower than anaerobic ones, whilst the difference was not significant. Surface settlements of semi aerobic landfills were higher than that of anaerobic ones (P<0.05). Moreover, there was negative correlation between VS content and surface settlements. Both leachate and water recycling methods did not lead to significant VS content difference, while leachate recycling would cause obviously uneven surface settlement. Biological degradable materials (BDM) value of aged refuse in semi aerobic landfill and anaerobic one was similar. Furthermore, BDM value increased with the increase of air pipe distance and depth. The greater the air pipe distance is, the bigger the difference of BDM value between the layers is. In addition, total extraction ratios of humic matters and HA/FA in semi aerobic and anaerobic landfill aged refuse had no significant differences.  相似文献   
8.
天峻县2009年游牧民定居工程,在3镇7乡的无房户或危房户中实施,建设分县城集中、乡镇所在地集中、村社适当集中三种定居建设模式。截至到年底共完成1036户,建设总面积6.94×104m2。  相似文献   
9.
In the Swifterbant area in The Netherlands, a complete Neolithic landscape is preserved, buried in a wetland environment. A dozen sites (dating from ca. 4300–4000 cal. BC) on levees of a former creek system are characterized by a black layer containing large amounts of carbonized plant remains, burnt bone, flint and pottery. These sites are usually interpreted as occupation sites with accumulated refuse of a society in transition from a Mesolithic to a Neolithic lifestyle (hunting and herding), in an area that was too wet for crops.In the context of a new research campaign in the area, we investigated the site- and land-use on two locations (S2 and S4) using micromorphological techniques.On S2, the soil matrix in the archaeological horizon has a heterogeneous, non-sedimentary appearance due to the ubiquitous presence of rounded and subrounded aggregates. These aggregates indicate that the sediment was disturbed after deposition, but it is unclear by what human activity. This disturbance is not restricted to the archaeological site horizon, but extends also into the under- and overlying layers.On S4, three layers can be distinguished. Only the lower and central parts are usually regarded as archaeological layers. The lower layer shows thorough mixing of the (partly decalcified) groundmass and the incorporation of anthropogenic materials (carbonized plant remains, burnt bone, etc.). Most probably, the thorough mixing is a result of tillage. The central layer consists of thinly laminated phytoliths and carbonized plant remains with ample fragments of (burnt) bone, angular sediment clods and some dog coprolites. Mineral sediments are absent. Apparently, the layer was formed by human activities that resulted in a massive accumulation of burnt organic materials and anthropogenic debris. The preservation of the micro-layering formed by phytoliths and carbonized is remarkable, since trampling would have deformed or disturbed the layering. The surprising conclusion therefore has to be that this location was not the main settlement area—as was implicitly thought until now. Rather, the area should be interpreted as a location where specific activities resulted in the accumulation of burnt plant material, e.g. a waste dump. The upper layer again has indications of anthropogenic soil disturbance. Samples from the basin adjacent to the levee site show sediments that are deformed by trampling. The transition of the site to the channel shows no signs of trampling, but rather interfingering of site layers with channel sediments. Lack of trampling in the central zone of S4 and the adjacent channel shore is at odds with the classical interpretation that the site represents a settlement area. The black layers that up till now were thought to encompass a complete settlement, could very well be a very prominent part of larger sites with remains of human activities during the Neolithic.  相似文献   
10.
Australia's environments have been dramatically transformed by immigrant communities who were impelled by a simple utilitarian dream and obliged by geographical and historical circumstance to contend with accumulating uncertainties, including those connected with the operation of Nature's own independent dynamic. With the exception of a few critical junctures and significant but highly localized settings which are reasonably well supplied with primary material, the historical records are scarcely satisfactory for fine-textured reconstructions of changing physical landscapes. There is certainly some potential for very broad ‘indicative’ stocktaking, but unavoidable imprecisions and the irritating problem of discontinuities rule out the most ambitious of International Geosphere-Biosphere Programme (IGBP) style studies. Therefore a major premise of this discussion is the acceptance that we are obviously better placed to offer a range of underpinning social, political and economic analyses than to launch into the production of confident, large-scale reconstructions of the past ‘faces’ of Australia. The bulk of this paper explores that proposition and is confined to such analyses. On the other hand, it also suggests that the time is ripe for tailoring novel co-operative research into landscape change in the ‘European’ era, especially by combining physical and documentary evidence in the investigation of carefully selected sites and situations.  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