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   444篇
  免费   7篇
林业   5篇
农学   2篇
  35篇
综合类   201篇
农作物   10篇
水产渔业   6篇
畜牧兽医   171篇
园艺   2篇
植物保护   19篇
  2012年   24篇
  2011年   26篇
  2010年   10篇
  2009年   3篇
  2008年   20篇
  2007年   24篇
  2006年   19篇
  2005年   28篇
  2004年   33篇
  2003年   23篇
  2002年   28篇
  2001年   16篇
  2000年   18篇
  1999年   10篇
  1998年   3篇
  1997年   3篇
  1995年   4篇
  1993年   5篇
  1992年   7篇
  1991年   5篇
  1988年   4篇
  1987年   6篇
  1985年   3篇
  1983年   3篇
  1982年   6篇
  1980年   3篇
  1979年   3篇
  1978年   4篇
  1977年   3篇
  1975年   3篇
  1973年   8篇
  1968年   5篇
  1967年   5篇
  1960年   3篇
  1958年   2篇
  1957年   3篇
  1956年   3篇
  1954年   2篇
  1950年   2篇
  1949年   2篇
  1941年   2篇
  1940年   2篇
  1939年   2篇
  1938年   2篇
  1936年   2篇
  1931年   3篇
  1930年   2篇
  1928年   2篇
  1916年   2篇
  1880年   2篇
排序方式: 共有451条查询结果,搜索用时 15 毫秒
81.
Lactoferrin concentration (LFC) in normal and mastitic milk of dairy goats were examined. LFC in bulk milk collected from 70 dairy goat farms and individual milk samples from 10 goats with mastitis were measured by enzyme-linked immunosorbent assay (ELISA) and their reaction time in methylene blue reduction test (MBRT) monitored. Bulk milk samples were categorized into three grades, such as high, normal and low, based on the reaction time in MBRT. The mean LFC in milk that was considered high quality (167 microg/ml) was significantly lower than that of those graded as normal (218 microg/ml) and low quality (304 microg/ml), while mean LFC in mastitic milk was 587 microg/m l. The correlation coefficient between milk LFC and MBRT time was found to be -0.7. Three goats were inoculated with Staphylococcus aureus into one of their udder halves. The mean milk LFC was found to be significantly higher (1500 microg/ml) than the control (30 microg/ml). These findings suggest that milk LFC may be useful as an index for intramammary infection in goats.  相似文献   
82.
To obtain a global view of functional interactions among genes in a metazoan genome, we computationally integrated interactome data, gene expression data, phenotype data, and functional annotation data from three model organisms-Saccharomyces cerevisiae, Caenorhabditis elegans, and Drosophila melanogaster-and predicted genome-wide genetic interactions in C. elegans. The resulting genetic interaction network (consisting of 18,183 interactions) provides a framework for system-level understanding of gene functions. We experimentally tested the predicted interactions for two human disease-related genes and identified 14 new modifiers.  相似文献   
83.
Four Holstein heifers (360 +/- 22 and 450 +/- 28 kg of BW in Exp. 1 and 2, respectively) fitted with ruminal trocars were used in 4 x 4 Latin square designs to evaluate the effects on ruminal microbial fermentation of the following: Exp. 1, no additive, alfalfa extract (30 g/d, AEX), a mixture of cinnamaldehyde (0.18 g/d) and eugenol (0.09 g/d; CIE1), and AEX and CIE1 in combination; and Exp. 2, no additive, anise oil (2 g/d), capsicum oil (1 g/d), and a mixture of cinnamaldehyde (0.6 g/d) and eugenol (0.3 g/d). Heifers were fed a 90:10 concentrate:barley straw diet (16% CP; 25% NDF) for ad libitum intake. Each period consisted of 15 d for adaptation and 6 d for sampling. On d 16 to 18, DM and water intakes were measured. On d 19 to 21 ruminal contents were sampled at 0, 3, 6, 9, and 12 h after feeding to determine ruminal pH and the concentrations of VFA, L-lactate, large peptides, small peptides plus AA (SPep+AA), and ammonia N. On d 20 and 21, samples of ruminal fluid were collected at 0 and 3 h after feeding to determine protozoal counts. In Exp. 1, CIE1 and AEX decreased (P < 0.05) total DMI, concentrate DMI, and water intake. The increase (P < 0.05) in SPep+AA and the decrease (P < 0.05) in ammonia N when supplementing CIE1 suggest that deamination was inhibited. Treatment AEX increased (P < 0.05) the acetate to propionate ratio, which is less efficient for beef production. Treatment CIE1 increased (P < 0.05) counts of holotrichs. Effects of AEX and CIE1 were not additive for many of the measured metabolites. In Exp. 2, treatments had no effect on ruminal pH, total VFA concentration, and butyrate proportion. The capsicum oil treatment increased (P < 0.05) DMI, water intake, and SPep+AA N concentration and decreased (P < 0.05) acetate proportion, branched-chain VFA concentration, and large peptide N concentration. The cinnamaldehyde (0.6 g/d) and eugenol (0.3 g/d) treatment decreased (P < 0.05) water intake, acetate proportion, branched-chain VFA, L-lactate, and ammonia N concentrations and increased (P < 0.05) propionate proportion and SPep+AA N concentration. The anise oil treatment decreased (P < 0.05) acetate to propionate ratio, branched-chain VFA and ammonia N concentrations, and protozoal counts. The results indicate that at the doses used a mixture of cinnamaldehyde and eugenol, anise oil, and capsicum oil may be useful as modifiers of rumen fermentation in beef production systems.  相似文献   
84.
OBJECTIVE: To evaluate whether a synthetic analogue of feline facial pheromone (FFP) calms cats before, and reduces struggling during intravenous catheterization. DESIGN: Block-randomized, 'blinded' clinical trial. ANIMALS: Seventy-seven healthy cats presented for elective surgery. PROCEDURE: Cats given glycopyrrolate and oxymorphone were assigned to one of four treatments: acepromazine and exposure to FFP (aceFFP); acepromazine and exposure to a placebo (acePlac); exposure to FFP only (FFP) and exposure to placebo only (Plac). The behaviour of cats was recorded on videotape for evaluation by assessors unaware of treatment group. Cats' veins were then catheterized by veterinary students unaware of the study protocol. Based on each cat's response to catheterization, the student independently decided whether intramuscular ketamine was required. RESULTS: Cats in the aceFFP group appeared to be calmer than acePlac cats on the basis of head position and their location in the cage (suggesting benefit from FFP among cats receiving acepromazine) but appeared to be less sedated. Cats in the aceFFP group also appeared to be calmer than FFP cats on the basis of head position and location in the cage. Feline facial pheromone cats were also calmer than Plac cats when compared using body and leg position. Exposure to FFP did not significantly reduce struggling at catheterization, nevertheless, the students were able to catheterize the veins in all cats. CONCLUSION AND CLINICAL RELEVANCE: There were no detrimental behavioural effects associated with either FFP or acepromazine. The FFP had additional calming effects in cats given acepromazine and, to a lesser degree, helped to calm cats that were not given acepromazine. Feline facial pheromone helps to calm cats in unfamiliar surroundings.  相似文献   
85.
Feeding obese dogs a high-fiber food with or without added conjugated linoleic acid (CLA) resulted in reduced caloric consumption, reduced body weight, and a 3.3% reduction in body fat, whereas feeding a low-fiber food resulted in a comparable increase in caloric consumption and a 2.4% gain in body fat. The addition of CLA did not significantly affect food intake, energy intake, final lean body percent, change in lean body percent, or final fat percent. These results suggest that the addition of dietary fiber but not CLA to foods may be helpful in the treatment of canine obesity.  相似文献   
86.
87.
88.
A 9‐month‐old male Great Dane had progressive generalized nodular dermatopathy for several months. There were > 100 raised, alopecic, firm, painful nodules throughout the skin. Aspirates from several lesions yielded moderate numbers of irregularly round or polygonal to spindle‐shaped cells with mild to moderate anisocytosis and few inflammatory cells, and the cytologic interpretation was proliferation of mesenchymal or histiocytic cells. On histopathologic examination, nodules were composed of densely packed sheets of round to spindle‐shaped cells with mild anisokaryosis and low mitotic activity. Multifocal histiocytic sarcoma with a spindle‐cell pattern was diagnosed based on morphologic features and intense expression of CD18. Additional immunophenotypic analysis on frozen sections of tissue confirmed the diagnosis of histiocytic sarcoma; expression of CD18, CD45, CD1a, CD11b, and CD11c, limited expression of Thy‐1 (CD90) and CD80, and lack of expression of CD4, CD11d, and CD86 indicated that the cells were likely interstitial dendritic cells; a review of reactive and neoplastic dendritic cells is provided. Based on staging, internal organs were not affected. Sequential treatment with lomustine and doxorubicin failed to prevent progression of the cutaneous lesions, and the dog died 3 months after initial diagnosis. At necropsy, a focus of neoplastic cells was present in one lymph node, but except for skin other organs were not involved. The clinical presentation of histiocytic sarcoma may be unusual, and neoplastic cells may lack overt features of malignancy on cytologic and histopathologic examination. In some instances, immunophenotyping is required to differentiate histiocytic sarcoma from other histiocytic disorders.  相似文献   
89.
Objective The aim of this study was to evaluate whether the Bichon Frise population in the UK is at the same risk of developing retinal detachment in association with cataract formation and following phacoemulsification as described in reports from the USA. Procedures The medical records of Bichon Frises which were presented for cataract assessment and of those which were treated with phacoemulsification at Willows Referral Service between 1997 and 2009 were reviewed. Results Forty eyes (26 dogs) with unilateral or bilateral cataracts were included in the study. There was no evidence of retinal detachment associated with the cataracts at initial presentation. Phacoemulsification was performed on 34 eyes (20 dogs). Clinically evident lens‐induced uveitis was treated preoperatively in 17/34 eyes. Artificial lens implantation was carried out in 30/34 eyes; automated anterior vitrectomy was performed in 7/34 eyes. The mean follow‐up time was 16.6 months (range 1.5–73 months). At the last re‐examination, 31/34 eyes (91.2%) were visual. Three eyes (8.8%) were blind – two (in the same dog) because of presumptive bilateral optic nerve disease and one because of uveitis and secondary glaucoma. There was no evidence of retinal detachment following phacoemulsification in any of the 34 eyes. Conclusion This study suggests that the Bichon Frise population in the UK does not appear to have a predisposition for retinal detachment in association with cataract formation or following cataract surgery. Prophylactic random transscleral laser retinopexy or transscleral cryopexy cannot therefore be routinely recommended for Bichon Frises with cataracts in the UK.  相似文献   
90.
Clostridium perfringens which is a causative agent of several diseases in animals and humans is capable of producing a variety of toxins. Isolates are typed into five types on the basis of the presence of one or more of the four major toxins genes, i.e. cpa, cpb, etx, and iap. A decade ago another toxin termed beta2 (beta2) and its gene (cpb2) were identified. Two alleles of cpb2 are known and a possible link between differences in gene expression and allelic variation has been reported. A correlation between the level of expression and the origin of the isolates has also been suggested. The demonstration and typing of the cpb2 gene in the genome of isolates can be seen as a vital part of research on the role of the beta2 toxin in the pathogenesis of disease. This study describes a PCR with a single primer set which in contrast to published primer sets recognizes both alleles. Subsequent restriction enzyme analysis of the PCR product enables typing of the alleles. Applying this protocol on a total of 102 isolates, a sub-variant was found which occurred only in C. perfringens isolates from pigs and appeared to be the predominant variant found in C. perfringens isolates from this species.  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