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   1805篇
  免费   187篇
林业   112篇
农学   55篇
基础科学   3篇
  340篇
综合类   153篇
农作物   82篇
水产渔业   119篇
畜牧兽医   920篇
园艺   45篇
植物保护   163篇
  2023年   17篇
  2022年   16篇
  2021年   62篇
  2020年   58篇
  2019年   95篇
  2018年   56篇
  2017年   53篇
  2016年   61篇
  2015年   60篇
  2014年   72篇
  2013年   85篇
  2012年   139篇
  2011年   151篇
  2010年   74篇
  2009年   65篇
  2008年   117篇
  2007年   121篇
  2006年   94篇
  2005年   91篇
  2004年   87篇
  2003年   76篇
  2002年   80篇
  2001年   18篇
  2000年   12篇
  1999年   10篇
  1998年   9篇
  1997年   12篇
  1996年   11篇
  1995年   12篇
  1994年   5篇
  1993年   7篇
  1992年   5篇
  1989年   6篇
  1988年   8篇
  1985年   4篇
  1984年   5篇
  1983年   7篇
  1980年   4篇
  1978年   4篇
  1977年   6篇
  1967年   6篇
  1966年   4篇
  1963年   4篇
  1962年   6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1992条查询结果,搜索用时 31 毫秒
1.
2.
A cohort of 53 swine seronegative to Aujeszky's disease virus (ADV) was monitored in a 1 year study of a chronically infected commercial Swedish weaner pig producing herd. Serum samples were acquired from all 134 adult swine and analyzed by enzyme-linked immmunosorbent assay (ELISA). Animals testing negative, along with introduced replacement gilts, were followed serologically every second month. Movements of animals were recorded for 319 days and exposure to seropositive animals was calculated for each seronegative pig in the cohort. The accumulated daily pig contact between the 53 ADV-non-infected swine and 43 infected swine was 35 660 days and the median number of days in contact for the non-infected swine with infected was 222. Despite the frequent contact with seropositive pigs, no seronegative animals seroconverted during the first 11 months of observation. Forty-six of 53 pigs seroconverted after a clinical outbreak during the twelfth month of observation.  相似文献   
3.
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   

4.
5.
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   

6.
Laparoscopic surgery in adult cattle.   总被引:6,自引:0,他引:6  
Laparoscopy in cattle is a promising tool for clinical diagnosis and treatment. The lower cost of the materials available in addition to the possibility of an intervention on an animal that is sedated does not entail more costs than an exploratory laparotomy. The application of this tool during abdominal explorations and biopsies allows the avoidance of invasive and often useless surgical interventions and even with the diagnosis and prognosis of certain conditions. Surgical techniques currently are limited to abomasopexies; however, never-ceasing progress and improvements in human surgery are expected to affect the future of bovine surgery.With the advancements in the multimedia technology used by universities, the use of laparoscopy as a pedagogic tool definitely has a promising future. Endoscopic exploration of the thorax is possible using the same material as for laparoscopy. In addition, diagnostic and biopsy applications are useful. The use of the laparoscope in different body cavities and for different applications would make the purchase of the required materials more cost-effective.  相似文献   
7.
To better characterise at the molecular level the nature of plant responses to infection by Rhodococcus fascians PCR-based differential display patterns of Atropa belladonna leafy gall (LG) and non-infected plant tissues were compared. Six differentially expressed genes were identified and their altered expression was confirmed by RT-PCR. Three of them corresponded to up-regulated genes which encode proteins involved in plant defence. The three remaining cDNA fragments which correspond to down-regulated genes in LG, encoded proteins with similarity to a multicystatin, a miraculin and a methallothionein-like protein, respectively. Upon elimination of the bacteria from infected plant tissue, the expression of up-regulated genes was maintained, whereas expression of down-regulated genes resumed suggesting a potential role of these up-regulated genes in plant growth and development.  相似文献   
8.
9.
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   
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