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   372篇
  免费   9篇
林业   27篇
农学   2篇
  31篇
综合类   74篇
农作物   4篇
水产渔业   10篇
畜牧兽医   218篇
园艺   3篇
植物保护   12篇
  2021年   3篇
  2018年   7篇
  2017年   5篇
  2015年   2篇
  2014年   8篇
  2013年   8篇
  2012年   15篇
  2011年   15篇
  2010年   4篇
  2009年   7篇
  2008年   14篇
  2007年   10篇
  2006年   12篇
  2005年   21篇
  2004年   25篇
  2003年   15篇
  2002年   15篇
  2001年   17篇
  2000年   14篇
  1999年   8篇
  1997年   3篇
  1996年   5篇
  1995年   3篇
  1994年   3篇
  1993年   3篇
  1992年   6篇
  1991年   4篇
  1990年   7篇
  1989年   3篇
  1988年   4篇
  1987年   7篇
  1986年   15篇
  1985年   9篇
  1984年   4篇
  1983年   4篇
  1982年   3篇
  1981年   4篇
  1980年   2篇
  1979年   6篇
  1976年   2篇
  1975年   3篇
  1972年   3篇
  1971年   3篇
  1970年   2篇
  1969年   8篇
  1968年   6篇
  1966年   3篇
  1963年   3篇
  1948年   2篇
  1934年   2篇
排序方式: 共有381条查询结果,搜索用时 31 毫秒
91.
Stomatitis is a common problem in lizards, and the etiologies of stomatitis in lizards are not well understood. Four green tree monitor lizards (Varanus prasinus) from two different collections were evaluated because of proliferative stomatitis. Degenerate PCR primers targeting a conserved region of herpesvirus DNA-dependent DNA polymerase were used to amplify and sequence a product from gingival tissue of three of four lizards (cases 1, 3, and 4). DNA in situ hybridization of tissues from three lizards was positive for herpesvirus in the oral mucosa of all three lizards tested (cases 1-3) and the brain of two lizards (cases 1 and 3). Comparative sequence analysis suggests that this virus is a novel member of the subfamily alpha-herpesvirinae, and is here termed varanid herpesvirus 1.  相似文献   
92.
OBJECTIVE: To describe the gross cross-sectional anatomy of green turtles (Chelonia mydas) and evaluate magnetic resonance imaging (MRI) for detection of internal tumors in green turtles with cutaneous fibropapillomatosis. DESIGN: Prospective study. ANIMALS: 3 dead green turtles, 1 healthy green turtle, and 8 green turtles with cutaneous fibropapillomatosis. PROCEDURES: Gross cross-sectional anatomy of a dead turtle was described. Each live turtle underwent a complete physical examination, and dorsoventral whole-body survey radiographic views were obtained. Magnetic resonance imaging was performed in dorsal and transverse planes. Radiographs and magnetic resonance images were examined for evidence of internal nodules. Results were compared with necropsy findings in 5 of 8 turtles. RESULTS: Nodules in the lungs of 2 turtles were detected via radiography, whereas pulmonary nodules were detected in 5 turtles via MRI. No other visceral nodules were detected via radiography; however, masses in the stomach and adjacent to the bladder and kidneys were detected in 1 turtle via MRI. Other extrapulmonary abnormalities observed at necropsy were not detected on MR images. CONCLUSIONS AND CLINICAL RELEVANCE: MRI may be valuable for detection of internal tumors in green turtles with cutaneous fibropapillomatosis. Nodules were more apparent in the lungs than in other organs. Results of MRI may serve as prognostic indicators for sea turtles undergoing assessment, treatment, and rehabilitation. Clinical application may be limited by cost and availability of MRI technology.  相似文献   
93.
The pharmacokinetics of enrofloxacin administered orally and i.v. to American alligators (Alligator mississippiensis) at 5 mg/kg was determined. Plasma levels of enrofloxacin and its metabolite ciprofloxacin were measured using high-performance liquid chromatography and the resulting concentration versus time curve analyzed using compartmental modeling techniques for the i.v. data and noncompartmental modeling techniques for the oral data. A two-compartment model best represented the i.v. data. Intravenous administration of enrofloxacin resulted in an extrapolated mean plasma concentration of 4.19 +/- 4.23 microg/ml at time zero, with average plasma drug levels remaining above 1.0 microg/ml for an average of 36 hr. Plasma volume of distribution for i.v. enrofloxacin was 1.88 +/- 0.96 L/kg, with a harmonic mean elimination half-life of 21.05 hr and mean total body clearance rate of 0.047 +/- 0.021 L/hr/kg. Plasma levels of p.o. enrofloxacin remained below 1.0 microg/ml in all test animals, and average concentrations ranged from 0.08 to 0.50 microg/ml throughout the sampling period. Oral administration of enrofloxacin achieved a mean maximum plasma concentration of 0.50 +/- 0.27 microg/ml at 55 +/- 29 hr after administration, with a harmonic mean terminal elimination half-life of 77.73 hr. Minimal levels of ciprofloxacin were detected after both oral and i.v. enrofloxacin administration, with concentrations below minimum inhibitory concentrations for most susceptible organisms. On the basis of the results of this study, enrofloxacin administered to American alligators at 5 mg/kg i.v. q 36 hr is expected to maintain plasma concentrations that approximate the minimum inhibitory concentration for susceptible organisms (0.5 microg/ml). Enrofloxacin administered to American alligators at 5 mg/kg p.o. is not expected to achieve minimum inhibitory values for susceptible organisms.  相似文献   
94.
Five laboratories participated in a study to evaluate sources of variation in results from an enzyme-linked immunosorbent assay (ELISA) for antibodies against Mycobacterium avium subsp. paratuberculosis. Each laboratory repeatedly tested duplicates of a negative, positive (P), and high-positive (HP) serum sample, which were supplied by the United States Department of Agriculture: Animal and Plant Health Inspection Service: Veterinary Services, National Veterinary Services Laboratories, Ames, IA, on all 96-well microtiter plates when routinely testing other samples for M. avium subsp. paratuberculosis antibodies. These 3 sera were aliquoted and sent to the 5 participating laboratories. This study focused on variation in test results because of assay reagents and laboratory techniques and did not account for biologic variability associated with the time course of infection in cattle. Overall, results from 868 microtiter plates were used in the study. For each sample a sample-to-positive (S/P) ratio was calculated according to the manufacturer's directions. The S/ P ratio for the P sample ranged from 0.06 to 1.039 (mean = 0.466 and 0.484 for wells 1 and 2, respectively) and those for the HP sample ranged from 2.446 to 8.727 (mean = 4.027 and 3.980 for wells 1 and 2, respectively). The majority of the variation in S/P ratio for the P sample was attributed to kit lot (37.5%), followed by random (unexplained) error (27.0%), laboratory (18.3%), and kit lot by laboratory (11.9%). By eliminating plates in which the separation between negative and positive control ODs was less than 0.4, the proportion of variation attributed to laboratory was reduced markedly. These results confirm that there is variability in M. avium subsp. paratuberculosis ELISA results and that several sources contribute to the observed variability. The study gives a relative estimate of the contribution of various sources to the overall variability observed in the M. avium subsp. paratuberculosis ELISA results with kit lot being a primary contributor. Similar data for other ELISA tests for antibodies to M. avium subsp. paratuberculosis or other antigens also should be developed.  相似文献   
95.
A 2.5-yr-old, intact male Japanese macaque (Macaca fuscata) was observed to have a thickened ileum during exploratory laparotomy. Lawsonia intracellularis-associated proliferative enteritis was diagnosed using histopathology (Warthin-Starry stain), immunohistochemistry, and polymerase chain reaction analysis of the ileal biopsy. The animal developed transient diarrhea and severe hypoproteinemia 16 days after surgery but recovered with intensive treatment using azithromycin. Given the fact that very specific tests are required for identifying this organism, L. intracellularis may be underdiagnosed in nonhuman primates.  相似文献   
96.
A method to accelerate and quantitate retrogradation of starch pastes using a freeze-thaw cycle (FTC) process and turbidometric analysis has been developed. Using this method and differential scanning calorimetry (DSC), it was determined that the rate of retrogradation in 2.5% waxy maize pastes was inversely correlated to the rate of freezing, and that the thawing temperature affected perfection of the crystallites in retrograded amylopectin. DSC and X-ray diffraction were used to determine whether the crystallites formed during the FTC process were the same as those formed in starch pastes held isothermally at 4°C. Analysis of retrogradation of pastes of starches from various botanical sources indicated that the method reflects retrogradation in higher concentration pastes. Retrogradation rates were reduced by the addition of sodium dodecyl sulfate. Microstructures of freeze-thaw processed waxy maize and common corn starch pastes were examined.  相似文献   
97.
98.
Results of commercially available diagnostic test kits and commercial laboratory test results were compared for ability to detect FeLV antigen. Results of the immunofluorescent antibody (IFA) test were compared with test kit ELISA results and with results of a system in which samples were applied to an absorbent material, dried, sent to a laboratory, eluted, and assayed by a plate ELISA. Test kits were generally highly sensitive and specific, compared with the IFA test performed at a commercial laboratory. Feline heterophile antibody, specific for mouse immunoglobulin, was detected in approximately 0.14 to 0.57% of the cat population. Test kits B, E, and D contain reagents that correct for antimouse antibodies. During 1989 and 1990, 2,229 feline serum samples were tested for FeLV antigen (gsa p27); positive ELISA results were obtained for 204 (9%) of the samples. Results for 32 (1.4%) samples were interpreted as equivocal (color development slightly exceeded that of the negative control, but was much less than that of the positive control). Collectively, the data indicate that when testing serum or saliva, a negative test result may be a good predictor that a cat is not infected. In populations of cats in which FeLV prevalence is low, a positive test result may not be reliable and thus, a confirmatory test should be performed.  相似文献   
99.
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