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   1054篇
  免费   87篇
  国内免费   3篇
林业   51篇
农学   27篇
基础科学   3篇
  161篇
综合类   118篇
农作物   26篇
水产渔业   66篇
畜牧兽医   619篇
园艺   23篇
植物保护   50篇
  2023年   11篇
  2022年   11篇
  2021年   27篇
  2020年   24篇
  2019年   23篇
  2018年   20篇
  2017年   35篇
  2016年   32篇
  2015年   36篇
  2014年   39篇
  2013年   43篇
  2012年   57篇
  2011年   77篇
  2010年   53篇
  2009年   51篇
  2008年   76篇
  2007年   77篇
  2006年   77篇
  2005年   47篇
  2004年   62篇
  2003年   48篇
  2002年   48篇
  2001年   19篇
  2000年   19篇
  1999年   17篇
  1998年   9篇
  1997年   6篇
  1996年   4篇
  1995年   8篇
  1994年   7篇
  1993年   2篇
  1992年   7篇
  1991年   4篇
  1990年   4篇
  1989年   7篇
  1986年   3篇
  1985年   2篇
  1983年   3篇
  1982年   2篇
  1980年   2篇
  1977年   2篇
  1972年   2篇
  1971年   4篇
  1970年   4篇
  1969年   5篇
  1968年   4篇
  1967年   4篇
  1966年   2篇
  1963年   2篇
  1939年   2篇
排序方式: 共有1144条查询结果,搜索用时 31 毫秒
91.
Cataracts are among the most common ocular diseases, and are a leading cause of vision loss in humans and dogs. Jack Russell Terriers (JRT) and Labrador Retrievers (LR) are among the most popular canine breeds in the United Kingdom, and also among the most affected by cataracts.This study aimed to analyze the clinical features and the surgical outcome of cataracts in JRT and LR in an ophthalmologic reference Veterinary Hospital in the United Kingdom. For that purpose, medical records from JRT and LR diagnosed with cataracts between January 2015 and December 2016 were retrospectively evaluated. Data related to identification, clinical history, preoperative features, and surgical outcomes were analyzed.Forty-four dogs (81 eyes), including 26 JRT and 18 LR, were enrolled in the study. Mean ages were 10.2 ± 3.2 years in JRT and 8.5 ± 3.7 years in LR. Twenty-eight (63.6%) were females and 16 (36.4%) were males. Most dogs (84.1%) presented with bilateral cataracts. Nuclear and cortical cataracts were the most prevalent type in both breeds (JRT: n?=?30, 61.2%; LR: n?=?16, 50.0%), although subcapsular cataracts were also frequent in LR (n?=?10, 31.3%). Significant differences in cataract location within the lens were detected between the two breeds (P?=?.002).Senile in JRT (n?=?7) and genetic in LR (n?=?7) were the most common etiologies. Concomitant ocular lesions were more frequent in dogs presented with cataracts in advanced stages, and included lens (n?=?18; JRT: n?=?15; LR: n?=?3) and retinal alterations (n?=?8; JRT: n?=?2; LR: n?=?6), and glaucoma (n?=?6; JRT: n?=?5; LR: n?=?1). Thirty-three animals (75.0%, 51 eyes) were submitted to phacoemulsification with intraocular lens placement. Of these, 28 eyes (54.9%; JRT: n?=?21; LR: n?=?7) were visual, 19 eyes (37.3%; JRT: n?=?11; LR: n?=?8) presented impaired vision and four eyes (7.8%; JRT: n?=?0; LR: n?=?4) were blind at last clinical record. Postoperative complications were detected in 11 eyes (21.6%), and were more frequent in dogs presented with cataracts in advanced stages.These results and the multifactorial nature of cataracts call for further studies to identify and characterize the variables in a broader assessment, including other breeds and influencing factors.  相似文献   
92.
93.
Global climate change is expected to influence the distribution of global biodiversity. C4 and C3 perennial grasses co-occur in the fire-prone KwaZulu-Natal uKhahlamba-Drakensberg grasslands, with C3 grass species occurring at cooler locations in the mountain range and C4 grass species at warmer locations. If a warming climate is expected to cause a contraction in the ranges of C3 grasses, evidence of temperature controlling current distributions is required. This study modelled the distribution of five C3 grass species, namely Tenaxia stricta, Tenaxia disticha, Festuca costata, Merxmuellera drakensbergensis and Merxmuellera stereophylla, to temperature-related surrogate variables using presence–absence data collected across the environmental heterogeneity of the mountain range. Distributions of each species, and of all species combined, were modelled using generalised additive models. These temperature-related variables accounted for the distribution of all five species, least so for F. costata. Four species could therefore contract in range in response to climate change, whereas F. costata is least likely to have a range contraction directly related to a warming climate and could experience a range expansion owing to the fertilising effect of increased [CO2].  相似文献   
94.
A 4-month-old female Holstein Friesian calf was referred to the Veterinary Teaching Hospital, University of Berne, Switzerland for evaluation of ataxia, weakness, apathy and stunted growth. Clinical examination revealed generalized ataxia, propioceptive deficits, decreased menace response and sensibility. Postmortem examination did not reveal macroscopic changes of major organs. Histologically, the brain and the spinal cord lesions were characterized by polymicrocavitation, preferentially affecting the white matter fibers at the junction of grey and white matter and by the presence of Alzheimer type II cells. The liver revealed lesions consistent with a congenital portosystemic shunt, characterized by increased numbers of arteriolar profiles and hypoplasia to absence of portal veins. The pathological investigations along with the animal history and clinical signs indicated a hepatic encephalomyelopathy due to a congenital portosystemic shunt.  相似文献   
95.
96.
97.
98.
The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement was first published in 2007 and again in 2014. The purpose of the original STROBE was to provide guidance for authors, reviewers and editors to improve the comprehensiveness of reporting; however, STROBE has a unique focus on observational studies. Although much of the guidance provided by the original STROBE document is directly applicable, it was deemed useful to map those statements to veterinary concepts, provide veterinary examples and highlight unique aspects of reporting in veterinary observational studies. Here, we present the examples and explanations for the checklist items included in the STROBE‐Vet Statement. Thus, this is a companion document to the STROBE‐Vet Statement Methods and process document, which describes the checklist and how it was developed.  相似文献   
99.
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   
100.
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