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   1112篇
  免费   112篇
林业   55篇
农学   24篇
基础科学   1篇
  208篇
综合类   86篇
农作物   49篇
水产渔业   65篇
畜牧兽医   595篇
园艺   32篇
植物保护   109篇
  2023年   12篇
  2022年   5篇
  2021年   36篇
  2020年   27篇
  2019年   46篇
  2018年   29篇
  2017年   31篇
  2016年   24篇
  2015年   26篇
  2014年   41篇
  2013年   50篇
  2012年   80篇
  2011年   87篇
  2010年   44篇
  2009年   44篇
  2008年   85篇
  2007年   77篇
  2006年   64篇
  2005年   58篇
  2004年   57篇
  2003年   44篇
  2002年   51篇
  2001年   15篇
  2000年   9篇
  1999年   9篇
  1998年   6篇
  1997年   6篇
  1996年   6篇
  1995年   9篇
  1993年   5篇
  1989年   6篇
  1988年   4篇
  1985年   4篇
  1984年   5篇
  1983年   6篇
  1980年   4篇
  1979年   3篇
  1978年   3篇
  1977年   5篇
  1967年   6篇
  1966年   4篇
  1964年   3篇
  1963年   4篇
  1962年   5篇
  1961年   5篇
  1960年   8篇
  1959年   7篇
  1958年   5篇
  1955年   8篇
  1932年   4篇
排序方式: 共有1224条查询结果,搜索用时 31 毫秒
1.
Landscape Ecology - Several case studies investigated the role of ecosystem services in participatory planning processes. However, no systematic study exists that cuts across a large number of...  相似文献   
2.
1. The fear levels of broilers arriving from slaughter at 4 commercial processing plants were assessed using tonic immobility (TI) tests. The relative effects of selected variables were also examined.

2. Neither the position of the birds on the lorry, nor their sex, nor the ambient temperature nor the identity of the experimeter exerted any significant effects on tonic immobility reactions.

3. Although the longest and shortest immobility responses followed transportation in the fixed crates and metal modules respectively, system comparisons may be confounded by variations in the birds’ genetic and/or experiential backgrounds.

4. Both journey duration and waiting time before transport bore an unambiguous and positive linear relationship with mean TI duration. The duration of transit was the major factor determining fear levels following both commercial and simulated journeys.  相似文献   

3.
4.
1. A time‐lapse photographic technique has been developed which enables routine recording of the hatching times of up to 192 chicken embryos.

2. Storage of eggs for 14 d caused a delay of 134 h in the mean total incubation period.

3. Female embryos hatched about 3 h earlier than males in the non‐stored eggs but there was no difference between the sexes in eggs stored for 14 d.

4. Rate of weight loss during incubation was similar in both non‐stored and stored eggs: there was no relationship between weight loss at 19 d incubation and total incubation period.

5. Hatchability of fertile eggs was 19.5% lower in eggs stored for 14 d and proportionately more embryos died between 4 d and 18 d incubation than in the non‐stored eggs.  相似文献   

5.
6.
Convivial and playful, the ferret has cohabited with humans for hundreds of years. Maintenance of this mustelid's health and quality of life is paramount for the endurance of the human-animal bond. This review article for veterinary care givers, veterinarians, and staff, encompasses discussions on: husbandry, clinical techniques, prevalent diseases, history taking, physical examination, vaccination, and pain recognition. This article also enables the veterinary community to contribute to the care and welfare of ferret patients by offering facts to distinguish these animals from dogs and cats.  相似文献   
7.
8.
Genetic selection for carcass traits is paramount to maximize the profitability and long‐term sustainability of any meat‐producing livestock species. The main objectives of this research were to evaluate the efficiency of indicator traits for the genetic improvement of lamb carcass traits and to determine the value of including carcass traits into terminal sire selection indexes for the Canadian sheep industry. The carcass traits included hot carcass weight (HCW), fat depth at the GR site (FATGR) and average carcass conformation score (AVGCONF), and were measured on heavy lambs (slaughter age less than 365 days and HCW greater than 16.3 kg) in commercial abattoirs. Growth traits were found to be moderately efficient indicator traits for the genetic improvement of HCW but selection on ultrasound traits was necessary to substantially improve the carcass quality traits (FATGR and AVGCONF). Economic selection indexes were designed by adding various combinations of carcass traits into the Canadian Sheep Genetic Evaluation System terminal indexes. Records measured on individuals and progeny were assumed to be the sources of information for live animal and carcass traits, respectively. The changes in index accuracy, efficiency and expected correlated response were used to assess the value of their inclusion. HCW was found to have a large economic value, and its inclusion into terminal selection indexes was expected to substantially increase their accuracy (0.08–0.12 points) and efficiency (20%–30%). However, further including FATGR (measured 110 mm from the carcass midline over the 12th rib) and AVGCONF had little impact on the accuracy (≤0.03) and efficiency (1%–7%) of the proposed indexes. Thus, the inclusion of carcass traits into the existing terminal selection indexes could be beneficial for the genetic improvement of HCW, but further research is needed to determine optimal methods of increasing carcass fatness and muscularity.  相似文献   
9.
10.
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