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   760篇
  免费   137篇
  国内免费   55篇
林业   7篇
农学   26篇
基础科学   5篇
  8篇
综合类   263篇
农作物   31篇
水产渔业   20篇
畜牧兽医   552篇
园艺   3篇
植物保护   37篇
  2024年   2篇
  2023年   17篇
  2022年   22篇
  2021年   43篇
  2020年   40篇
  2019年   56篇
  2018年   27篇
  2017年   54篇
  2016年   63篇
  2015年   38篇
  2014年   36篇
  2013年   32篇
  2012年   76篇
  2011年   62篇
  2010年   33篇
  2009年   51篇
  2008年   28篇
  2007年   30篇
  2006年   37篇
  2005年   21篇
  2004年   22篇
  2003年   28篇
  2002年   9篇
  2001年   19篇
  2000年   16篇
  1999年   16篇
  1998年   5篇
  1997年   9篇
  1996年   9篇
  1995年   2篇
  1994年   8篇
  1993年   3篇
  1992年   11篇
  1991年   3篇
  1990年   1篇
  1989年   2篇
  1988年   4篇
  1987年   4篇
  1986年   2篇
  1985年   2篇
  1984年   2篇
  1982年   2篇
  1981年   1篇
  1980年   4篇
排序方式: 共有952条查询结果,搜索用时 15 毫秒
21.
22.
犬细小病毒病是由犬细小病毒(cpv)引起的一种急性传染病,发病率和死亡率比较高,达10%~50%,自愈率〈5%.笔者在近一年中的犬病治疗过程中用犬细小病毒快速诊断试纸条确诊为犬细小病毒病的有16例。经过临床治疗得出,除了采用高免血清和对症治疗外,治愈率的高低在很大程度上取决于输液,此外对病犬的护理正确精细与否也有一定的关系。本文重点介绍了犬细小病毒病的临床症状、剖检变化、鉴别诊断、治疗情况及治疗体会。  相似文献   
23.
24.
青贮玉米促生菌的鉴定及生物学特性的研究   总被引:2,自引:0,他引:2  
根据布坎南.R.E等著《伯杰细菌鉴定手册》(第八版),对4株青贮玉米促进菌进行鉴定。结果表明,4株促生菌分属于短芽胞杆菌(Bacillus brevis),蜡质芽孢杆菌(Bacillus cereus),放射形土壤杆菌(Agrobacteria radiobacter)和假单胞杆菌(Pseudomonas sp)。此餐,还对4株促生菌的生物学特性进行了比较观察。  相似文献   
25.
Plasmodiophora brassicae is an obligate biotroph that causes clubroot, one of the most damaging diseases of crucifers. Differential cultivars and random amplified polymorphic DNA markers were used to assess the extent of genetic diversity among nine single-gall populations of P. brassicae and 37 single-spore isolates (SSI) derived from four of those field samples. Isolates were classified into eight pathotypes, and each isolate was associated with a unique molecular genotype. Virulence and DNA polymorphisms were detected within and between field isolates, and among SSIs from different pathotypes, hosts and geographical origins. The relatively high level of genetic diversity among field isolates was similar to that among SSIs derived from a single-club field isolate. Molecular and pathogenicity-based classifications were not clearly correlated, but isolates belonging to pathotype P1 were clustered. Two RAPD markers were specific to pathotype P1. The finding that genetic differences can occur in P. brassicae field isolates will be an important consideration in resistance genetic studies and in choosing breeding strategies to develop durable clubroot resistance.  相似文献   
26.
Eight isolates of Grapevine virus A (GVA), which induced different symptoms in leaves of Nicotiana benthamiana, were recovered from various grapevines. The dsRNA patterns of two isolates, which consistently induced mild vein clearing (referred here as mild isolates of GVA) were similar, but different from those of other isolates of GVA. Analysis based on overall nucleotide (nt) sequence identity in the 3 terminal part of the GVA genome, comprising part of ORF3 (putative movement protein, MP), entire ORF4 (capsid protein, CP), entire ORF5 and part of 3 UTR, revealed that GVA isolates separate into three groups (I, II, III), sharing 91.0–99.8% nt sequence identity within groups and 78.0–89.3% nt sequence identity between groups. Mild isolates of the virus were group III and shared only 78.0–79.6% nt sequence identity with the other isolates. The comparison of predicted amino acid sequences for MP and CP revealed many amino acid alterations, revealing distinct local net charges of these proteins for mild isolates of the virus. Based on both conserved and divergent nt regions in the CP and ORF5, oligonucleotide primers were designed for the simultaneous RT-PCR detection of all GVA isolates and for the specific detection of the most divergent virus variants represented here by mild isolates of the virus.  相似文献   
27.
Eleven native sheep, 1–2 years old, of both sexes were randomly divided into two groups, 6 sheep being allocated to the experimental group and 5 serving as controls. The sheep in the experimental group were fed 80% Tribulus terrestris and 20% alfalfa hay and wheat straw, while the control sheep were given a mixture of 40% alfalfa hay and 60% wheat straw. Clinical signs of hepatogenous photosensitivity were observed from day 11, including reddening and crust formation on the muzzle, nose, ears and eyelids, depression, weight loss, icterus, conjunctivitis, and yellow discoloration of the urine. Laboratory findings on weekly samples indicated significant differences (p<0.05) in white blood cell count, total plasma protein and fibrinogen, total and direct bilirubin, blood urea nitrogen and creatinine concentrations, and aspartate aminotransferase and alkaline phosphatase activities. There were no significant differences in the packed cell volume, in the neutrophil, lymphocyte or eosinophil counts, or in the serum calcium, phosphorus, potassium, sodium or chloride concentrations. At necropsy of the experimental animals, there were various degrees of generalized icterus and the livers were swollen and discolored by bile pigment. Histopathological examination revealed varying amounts of crystalloid material in the bile ducts and renal tubules, hepatocellular degeneration, biliary fibrosis and proliferation, renal tubular necrosis and focal necrosis of cardiac muscle.  相似文献   
28.
The accuracy of clinical observations was estimated using Bayesian latent-class models with two or more independent tests. Four veterinarians carried out systematic independent clinical examinations on 155 pigs in three herds. Based on the results of binary recordings of clinical observations on dullness, poor body condition (PBC), skin lesions, lameness, respiratory disease, and diarrhea, a latent disease state for each clinical disease was estimated using Gibbs sampling.

The accuracy of the clinical observations differed for the four observers and for different clinical signs. Population parameters were estimated from a Bayesian hierarchical model, and the accuracy of a random observer was calculated. We concluded that the accuracy of the veterinarians in this study substantiated the need to pursue more-precise definitions of the clinical findings and that larger sample sizes would be needed to provide reasonable variance estimates. Finally, we concluded that the uncertainty in the clinical decision-making process (starting with the clinical examination) needs to be represented fully.  相似文献   

29.
Genotyping of bovine leucocyte antigen DRB3.2 (BoLA-DRB3.2) in a total of 523 Norwegian Red (NR) cows from two groups selected for high protein yield and low clinical mastitis, respectively, identified 27 previously reported BoLA-DRB3.2 alleles across the groups. Significant differences in BoLA-DRB3.2 allele frequencies were found between the selection groups. Alleles *13, *18, *22 and *27 had a significantly higher frequency in cows selected for low clinical mastitis, while alleles *3, *9, *11 and *26 had a higher frequency in cows selected for high protein yield. Associations between BoLA-DRB3.2 alleles and clinical mastitis were analysed based on mastitis data from 741,072 first-lactation NR cows, of which 452 were genotyped. Alleles *22 and *26 were found to be associated with increased clinical mastitis, while alleles *7, *11, *18 and *24 had a favourable effect on mastitis resistance. Contradictory results from different studies investigating associations between BoLA-DRB3.2 alleles and mastitis indicate that future studies should focus on associations of mastitis with BoLA haplotypes rather than with single BoLA genes.  相似文献   
30.
Objective: To provide evidence that naturally occurring sepsis in dogs provides a unique opportunity to test new therapies in clinically relevant settings. Data sources: Human and veterinary literature. Human data synthesis: Sepsis is a devastating condition responsible for most intensive care unit deaths. Most clinical trials targeting inflammatory mediators of sepsis have failed to improve outcome in clinical patients despite promising results in laboratory animal models. Animal models of sepsis fail to reproduce the clinical syndrome and therefore lead to conclusions that may not be relevant to clinical care. Veterinary data synthesis: Sepsis is recognized but not well‐characterized in companion animal species. Despite some species variability, the cardiopulmonary response to sepsis in dogs is similar to humans. Additionally, inflammatory and coagulation changes that accompany canine sepsis are consistent with those documented in humans. Sepsis secondary to canine parvoviral infection offers the advantages of relative population homogeneity, predictable course, and easy early diagnosis. The disadvantages of canine parvovirus are that it affects a predominantly young and healthy population and results in low mortality with aggressive supportive care. Septic peritonitis and pneumonia have high mortality but can be challenging to diagnose, have a variable course, and affect a heterogeneous population, which can be an advantage or a disadvantage. Conclusions: Similar to trials currently being performed in canine cancer patients, veterinary clinical trials of new sepsis therapeutics may provide a unique opportunity to advance the treatment of sepsis in dogs, humans, and other species. Spontaneous sepsis from canine parvovirus, peritonitis, and pneumonia are common clinical conditions in which therapeutics can be tested.  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