全文获取类型
收费全文 | 1503篇 |
免费 | 65篇 |
国内免费 | 52篇 |
专业分类
林业 | 595篇 |
农学 | 19篇 |
基础科学 | 8篇 |
136篇 | |
综合类 | 567篇 |
农作物 | 9篇 |
水产渔业 | 17篇 |
畜牧兽医 | 177篇 |
园艺 | 76篇 |
植物保护 | 16篇 |
出版年
2024年 | 10篇 |
2023年 | 34篇 |
2022年 | 41篇 |
2021年 | 43篇 |
2020年 | 50篇 |
2019年 | 54篇 |
2018年 | 18篇 |
2017年 | 40篇 |
2016年 | 57篇 |
2015年 | 45篇 |
2014年 | 93篇 |
2013年 | 101篇 |
2012年 | 123篇 |
2011年 | 177篇 |
2010年 | 143篇 |
2009年 | 141篇 |
2008年 | 99篇 |
2007年 | 108篇 |
2006年 | 95篇 |
2005年 | 37篇 |
2004年 | 39篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1984年 | 1篇 |
排序方式: 共有1620条查询结果,搜索用时 15 毫秒
81.
西宁市林业站结合《抗旱造林综合技术集成与示范项目》,将青海云杉、油松、祁连圆柏、青杨雄株、小叶杨、银中杨、山杏、丁香,和引种培育试验区栽植的美国稠李、新疆忍冬、杜梨、文冠果、香茶藨子、海棠,共14种树种种植到海拔 2210~2750米区域,经试验研究:7个树种具有良好的适应性,可以作为西宁高海拔干旱地区林相改造选择树种。就上述14个树种生长情况的初步调查进行了成活率和生长量分析,并提出了相关建议,供参考。 相似文献
82.
Tim E. Carpenter Victor L. Coggins Clinton McCarthy Chans S. O’Brien Joshua M. O’Brien Timothy J. Schommer 《Preventive veterinary medicine》2014
Bighorn sheep currently occupy just 30% of their historic distribution, and persist in populations less than 5% as abundant overall as their early 19th century counterparts. Present-day recovery of bighorn sheep populations is in large part limited by periodic outbreaks of respiratory disease, which can be transmitted to bighorn sheep via contact with domestic sheep grazing in their vicinity. In order to assess the viability of bighorn sheep populations on the Payette National Forest (PNF) under several alternative proposals for domestic sheep grazing, we developed a series of interlinked models. Using telemetry and habitat data, we characterized herd home ranges and foray movements of bighorn sheep from their home ranges. Combining foray model movement estimates with known domestic sheep grazing areas (allotments), a Risk of Contact Model estimated bighorn sheep contact rates with domestic sheep allotments. Finally, we used demographic and epidemiologic data to construct population and disease transmission models (Disease Model), which we used to estimate bighorn sheep persistence under each alternative grazing scenario. Depending on the probability of disease transmission following interspecies contact, extirpation probabilities for the seven bighorn sheep herds examined here ranged from 20% to 100%. The Disease Model allowed us to assess the probabilities that varied domestic sheep management scenarios would support persistent populations of free-ranging bighorn sheep. 相似文献
83.
L. Del Río L. Chitimia A. Cubas I. Victoriano P. De la Rúa X. Gerrikagoitia M. Barral C.I. Muñoz-García E. Goyena D. García-Martínez R. Fisa C. Riera L. Murcia M. Segovia E. Berriatua 《Preventive veterinary medicine》2014
Leishmania spp. infection was investigated in tissue samples of wild carnivores from the Spanish Basque Country (BC), by PCR and DNA sequencing. The region is at the northern periphery of Leishmania infantum endemic Iberian Peninsula and infection in the dog (reservoir) or other species has not been previously reported. Leishmania kinetoplast DNA was detected by real-time PCR (rtPCR) in 28% (44/156) of animals. Specifically, in 26% of Eurasian badgers (n = 53), 29% of foxes (n = 48), 29% of stone martens (n = 21) and in 25–50% of less numerous species including genets, wild cats, pole cats, European mink and weasels. Infected animals particularly badgers, were most prevalent in the southernmost province of the BC (Araba) in areas dominated by arable land. Subsequent amplification and sequencing of a fragment of the rRNA internal transcribed spacer 2 (ITS2) from a subset of rtPCR positives samples confirmed the species as L. infantum, showing a high sequence homogeneity with ITS2 sequences of L. infantum from dogs and humans from southern Spain. In summary, this study reports for the first time L. infantum infection in wild carnivores from the BC including in stone martens, pole cats and minks in which infection has not been previously described. It supports the need to study infection in dogs and people in this region and is an example of the value of infection surveillance in wildlife to assess potential risks in the domestic environment and their role in spreading infections in non-endemic areas. 相似文献
84.
研究张掖国家湿地公园附植硅藻群落现状,为保护寒、旱区湿地水生植物与生物多样性提供理论依据。2017年夏、秋从张掖国家湿地公园浅水湖泊采集12种常见水生植物,采集植物上附植硅藻,并在水质富营养化评价的基础上进一步分析硅藻的种类分布、优势种、多样性和聚类性。结果表明,张掖国家湿地公园水体轻度富营养化;共检出附植硅藻39属158种(含变种),其中舟形藻属种类最多(18种),其次为菱形藻属(16种)、桥弯藻属(15种)和脆杆藻属(13种);Achnanthedium minutissimum为分布最为广泛的优势种,其次为Ulnaria acus和Encyonopsis subcryptocephala;Shannon-Weaver多样性指数在1.41~3.13,Pielou均匀度指数在0.58~1.07,均是秋季显著高于夏季(P0.05,t-test);Cody指数与聚类分析表明,在同一时期内附植硅藻种类组成的相似程度和优势种分布对部分宿主植物的选择趋于一致,但也有部分宿主植物之间附植硅藻群落结构仍然存在较大差异。 相似文献
85.
基于绿色健身新模式的城市体育公园空间景观营造研究——以晋中体育公园空间景观设计为例 总被引:1,自引:0,他引:1
绿色健身空间将人们的健身活动融入了自然环境的美妙景观中,能够达到绿色生态健身的效果。笔者以晋中体育公园的空间景观营造为例,在分析了体育公园空间景观营造原则和设计目标的基础上,重点针对体育公园的体育文化内涵营造进行探讨,提出了城市体育公园空间景观营造的方法。 相似文献
86.
文章对整个公园植物空间布局情况以及公园内园林植物所形成的开敞空间、半开敞空间、覆盖空间和垂直空间4种景观空间的造景特点、植物构成进行分析。尝试摆脱以园林植物为审美主体的静态观赏模式,提出园林植物应从装饰性的栽植配角转变为景观空间营造的主角,即营造舒适自然环境和游憩境域,才能达到园林营建的真正目的。 相似文献
87.
88.
89.
介绍了临时绿地建设的概念,西宁市建成区实施临时绿地建设的重要意义。通过阐述西宁市临时绿地建设项目中采取的设计理念与技术措施及开展临时绿地建设项目后取得的成绩,提出了临时绿地建设项目在西宁地区建成区绿化中可行性。 相似文献
90.
- 1. The Solitary Islands Marine Park (SIMP) in New South Wales (NSW), Australia, has strong cross‐shelf patterns of reef fish assemblages on shallow reefs (<25 m). While the SIMP also contains reef at depths of up to 75 m, marine communities below 25 m are poorly described. The Habitat Classification System (HCS) used for planning the arrangement of zones in this marine park included three depth categories for reef: shallow (<25 m); intermediate (25–60 m); and deep (>60 m). However, these had not been tested to determine if they adequately reflect biotic patterns.
- 2. Using baited remote underwater video (BRUV), fish assemblages were surveyed at 56 sites spread across shallow, intermediate, and deep reefs within the SIMP to examine spatial variation between depth categories. Relationships between assemblage patterns, depth, and four additional factors considered likely to affect assemblage patterns (distance from shore, reef type, dominant benthos, and latitude), were subsequently explored using multivariate statistical methods.
- 3. Reef fish assemblages differed significantly among the depth categories. Assemblage patterns for fish were strongly correlated with depth and moderately correlated with the dominant benthic assemblage. Correlations with the other factors were generally weak. Three distinct assemblages occurred on reefs <25 m, 25–50 m and >50 m. Shallow (<25 m) reefs also displayed strong cross‐shelf patterns, supporting the results from other studies. Weaker cross‐shelf patterns were evident at intermediate depths (25–50 m).
- 4. Depth‐based and cross‐shelf categories are clearly fundamental components for a HCS that will adequately represent reef fish assemblages for conservation planning in the SIMP. Further refining the depth criteria for the intermediate/deep boundary (to 50 m) improves this representation. Further research is required to determine the wider application of the refined HCS to other marine parks in NSW and to determine how well it represents other components of biodiversity. Copyright © 2011 John Wiley & Sons, Ltd.