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   427篇
  免费   35篇
  国内免费   2篇
林业   19篇
农学   12篇
基础科学   3篇
  108篇
综合类   22篇
农作物   20篇
水产渔业   33篇
畜牧兽医   203篇
园艺   17篇
植物保护   27篇
  2023年   2篇
  2022年   6篇
  2021年   16篇
  2020年   23篇
  2019年   29篇
  2018年   16篇
  2017年   14篇
  2016年   19篇
  2015年   10篇
  2014年   17篇
  2013年   22篇
  2012年   41篇
  2011年   46篇
  2010年   18篇
  2009年   19篇
  2008年   27篇
  2007年   29篇
  2006年   24篇
  2005年   21篇
  2004年   16篇
  2003年   14篇
  2002年   12篇
  2001年   5篇
  2000年   1篇
  1999年   6篇
  1997年   4篇
  1993年   1篇
  1988年   1篇
  1975年   1篇
  1973年   1篇
  1972年   2篇
  1968年   1篇
排序方式: 共有464条查询结果,搜索用时 15 毫秒
51.
In the literature, studies of Chlamydia infection in birds have usually been confined to the search for Chlamydia (C., formerly Chlamydophila) psittaci, so that little is known about the presence of other chlamydial agents. In the present study, cloacal swabs and faeces samples of urban pigeons have been examined by real-time PCR, DNA microarray assays and partial ompA sequencing. Whilst C. psittaci was the predominant chlamydial agent in this pigeon population (75.8% of all Chlamydiaceae positives), the combined use of highly specific and sensitive molecular assays facilitated the detection of atypical serovars of C. psittaci, as well as other species of Chlamydia, such as C. abortus. Detection of C. pecorum and C. trachomatis from an avian host is reported here for the first time. Rather unexpectedly, 19.5% of all Chlamydiaceae-positive cases turned out to be infected with non-classified organisms. The considerable prevalence of these novel agents raises the question of their epidemiological importance and possible role as pathogens. Future surveys in domestic and wild birds will have to take the extended variety of chlamydial organisms into account.  相似文献   
52.
ObjectiveTo determine constant rate infusion (CRI) protocols for romifidine (R) and romifidine combined with butorphanol (RB) resulting in constant sedation and romifidine plasma concentrations.Study designBlinded randomized crossover study.AnimalsTen adult research horses.MethodsPart I: After determining normal height of head above ground (HHAG = 100%), loading doses of romifidine (80 μg kg?1) with butorphanol (RB: 18 μg kg?1) or saline (R) were given intravenously (IV). Immediately afterwards, a butorphanol (RB: 25 μg kg?1 hour?1) or saline (R) CRI was administered for 2 hours. The HHAG was used as marker of sedation depth. Sedation was maintained for 2 hours by additional romifidine (20 μg kg?1) whenever HHAG > 50%. The dose rate of romifidine (μg kg?1 hour?1) required to maintain sedation was calculated for both treatments. Part II: After loading doses, the romifidine CRIs derived from part I were administered in parallel to butorphanol (RB) or saline (R). Sedation and ataxia were evaluated periodically. Romifidine plasma concentrations were measured by HPLC-MS-MS at 0, 5, 10, 15, 30, 45, 60, 90, 105, and 120 minutes. Data were analyzed using paired t-test, Fisher's exact test, Wilcoxon signed rank test, and two-way anova for repeated measures (p < 0.05).ResultsThere was no significant difference in romifidine requirements (R: 30; RB: 29 μg kg?1 hour?1). CRI protocols leading to constant sedation were developed. Time to first additional romifidine bolus was significantly longer in RB (mean ± SD, R: 38.5 ± 13.6; RB: 50.5 ± 11.7 minutes). Constant plasma concentrations of romifidine were achieved during the second hour of CRI. Ataxia was greater when butorphanol was added.ConclusionRomifidine bolus, followed by CRI, provided constant sedation assessed by HHAG. Butorphanol was ineffective in reducing romifidine requirements in unstimulated horses, but prolonged the sedation caused by the initial romifidine bolus.Clinical relevanceBoth protocols need to be tested under clinical conditions.  相似文献   
53.
An 8‐month‐old intact male English Setter was presented with bilateral shoulder lameness. Radiographic and CT examinations demonstrated bilateral irregular margination and separation of the supraglenoid tubercle from the scapula, with involvement of the cranial articular surface of the glenoid cavity. After 30 days of cage rest, complete fusion of proximal portions of both supraglenoid tubercles and persistent un‐united cranial portions of both glenoid cavities were evident. Histopathologic findings from biopsies of glenoid cavity defects were consistent with osteochondrosis or focal chondrodysplasia.  相似文献   
54.
An outbreak of cryptosporidiosis occurred in a mixed sheep/cattle farm of Central Italy in October 2011. A total of 450 ovines (250 sheep and 200 lambs) and 140 bovines (130 cows and 10 calves) were housed in two separated units, at the time of the outbreak. About half of the lambs had diarrhea due to Cryptosporidium sp. with a mortality rate of 80%; calves were not infected. Genomic DNA was extracted from an archived slide and from fecal specimens, and the parasite was identified as Cryptosporidium parvum by PCR and sequence analysis at the CpA135 gene. Genotyping at the GP60 gene showed the presence of a very rare genotype, IIaA20G2R1. Shortly after the outbreak was identified, the son of the farm's owner, aged 18 months, experienced an acute gastroenteritis and was hospitalized due to recurrent episodes of diarrhea, fever, vomiting and lack of appetite. The feces tested negative for bacteria and viruses, whereas cryptosporidiosis was diagnosed by microscopy and an immunochromatographic test. Molecular typing identified the C. parvum genotype IIaA20G2R1 in the feces of the child. This is the first case of transmission of cryptosporidiosis in Italy involving lambs as source of oocysts infectious to humans.  相似文献   
55.
The n-butanol fraction (BF) obtained from the crude extract of the marine sponge Petromica citrina, the halistanol-enriched fraction (TSH fraction), and the isolated compounds halistanol sulfate (1) and halistanol sulfate C (2), were evaluated for their inhibitory effects on the replication of the Herpes Simplex Virus type 1 (HSV-1, KOS strain) by the viral plaque number reduction assay. The TSH fraction was the most effective against HSV-1 replication (SI = 15.33), whereas compounds 1 (SI = 2.46) and 2 (SI = 1.95) were less active. The most active fraction and these compounds were also assayed to determine the viral multiplication step(s) upon which they act as well as their potential synergistic effects. The anti-HSV-1 activity detected was mediated by the inhibition of virus attachment and by the penetration into Vero cells, the virucidal effect on virus particles, and by the impairment in levels of ICP27 and gD proteins of HSV-1. In summary, these results suggest that the anti-HSV-1 activity of TSH fraction detected is possibly related to the synergic effects of compounds 1 and 2.  相似文献   
56.
While several population viability analyses (PVAs) have been performed on anadromous salmonids, less attention has been given to stream-living salmonids. In this work, we explore the role of PVA as a tool in the recovery of threatened stream-living salmonid species. The analysis has been performed with reference to marble trout Salmo marmoratus, a salmonid with a limited geographic distribution and at risk of extinction due to hybridization with the non-native introduced brown trout. Demographic parameters, such as survival, fecundity and density-dependent patterns were estimated from an eight year on-going monitoring program of two translocated marble trout populations in pristine, previously fishless streams (Zakojska and Gorska) in the Soca and Idrijca river basins (Slovenia). To explore the importance of disturbance events such as floods on marble trout population dynamics, we performed a PVA under three scenarios: (1) occurrence of both severe and moderate floods; (2) occurrence of only moderate floods; (3) no flood events. Our analysis shows that population viability is threatened only by severe flood events, otherwise the two populations prove to be fairly stable with population abundance fluctuating around stream carrying capacity. A sensitivity analysis performed on model parameters highlighted that density-dependence in first-year survival and the magnitude of reduction in population size after a severe flood are the two most crucial parameters affecting population abundance and quasi-extinction probability, respectively. While only extreme floods can drive the population to extinction, the increase in juvenile survival when population abundance collapses after a major flood may allow the populations to quickly recover from few reproductive individuals back to stream carrying capacity.  相似文献   
57.
Application of a sensomics approach on the water-soluble extract of a matured Gouda cheese including gel permeation chromatography, ultrafiltration, solid phase extraction, preparative RP-HPLC, and HILIC combined with analytical sensory tools enabled the comprehensive mapping of bitter-tasting metabolites. LC-MS-TOF and LC-MS/MS, independent synthesis, and sensory analysis revealed the identification of a total of 16 bitter peptides formed by proteolysis of caseins. Eleven previously unreported bitter peptides were aligned to beta-casein, among which 6 peptides were released from the sequence beta-CN(57-69) of the N terminus of beta-casein and 2 peptides originated from the C-terminal sequence beta-CN(198-206). The other peptides were liberated from miscellaneous regions of beta-casein, namely, beta-CN(22-28), beta-CN(74-86), beta-CN(74-77), and beta-CN(135-138), respectively. Six peptides were found to originate from alpha(s1)-casein and were shown to have the sequences alpha(s1)-CN(11-14), alpha(s1)-CN(56-60), alpha(s1)-CN(70/71-74), alpha(s1)-CN(110/111-114), and alpha(s1)-CN(135-136). Sensory evaluation of the purified, synthesized peptides revealed that 12 of these peptides showed pronounced bitter taste with recognition thresholds between 0.05 and 6.0 mmol/L. Among these peptides, the decapeptide YPFPGPIHNS exhibited a caffeine-like bitter taste quality at the lowest threshold concentration of 0.05 mmol/L.  相似文献   
58.
Enzymatic transformation of humic acids (HA), fulvic acids (FA) and indole was examined using naphthalene 1,2-dioxygenase (NDO). NDO was used as a model for dioxygenase enzymes found in various microbial species. Indole was used as a model substrate for NDO-catalyzed reactions resulting in condensation products. Although NDO is not classified as a soil enzyme, all HA and FA tested were susceptible to NDO-induced transformation. The extent of NDO-specific NADH oxidation in solutions containing HA and FA paralleled the percent aromaticity of the HA and FA. Furthermore, the UV–Vis absorptive properties of NDO-treated HA and FA were altered in a manner suggesting condensation reactions similar to the formation of indigo from indole. Condensation reactions were enhanced in NDO-treated mixtures containing indole and an FA. NDO retained activity for 2 weeks under ambient conditions, and retained some enzymatic activity for 9 days based on detection of specific metabolites by HPLC, suggesting prolonged extracellular activity. Humic substances have not previously been known to be substrates for dioxygenases; even more significant was that dioxygenase enzymes can facilitate condensation reactions between indole-like functional groups well-known to be present in HA and FA. These results illustrate how dioxygenases can be potential humic-modifying enzymes when released into the environment upon microbial death and concurrent cell lysis which could alter the bioavailability of organic contaminants associated with dissolved organic matter through specific modulation of enzyme activity involving substrate competition.  相似文献   
59.
The aim of this study was to evaluate the course of urethral obstruction in cats. Forty-five male cats with urethral obstruction or lower urinary tract signs referable to urethral obstruction were included in the study. Follow-up information was gained by telephone interview in most cases and was available in 39 cats. Of the 22 cats with idiopathic urethral obstruction, eight (36%) re-obstructed after 3-728 days (median 17 days). Of 10 cats with urolithiasis, three (30%) re-obstructed after 10, 13 and 472 days, respectively. Of the seven cats with urethral plugs, three (43%) re-obstructed after 4, 34 and 211 days, respectively. Recurrent signs of lower urinary tract disease including obstruction were common in cats with urethral obstruction (20/39; 51%) and occurred in the same frequency irrespective of the primary cause of the obstruction. Recurrent obstruction (14/39; 36%) was the most common reason for euthanasia and was performed in 8/39 (21%) cats.  相似文献   
60.
A 9‐year‐old mixed breed 13 kg spayed female dog was presented for evaluation of two masses in the right abdominal mammary gland region. Surgery was conducted to excise the masses. A grade I complex mammary gland carcinoma and high grade (grade III) mast cell tumor with an inguinal lymph node metastasis were diagnosed. Forty‐seven days after the surgical procedure, the mast cell tumor relapsed, and neoadjuvant treatment with lomustine (81 mg/m2) was prescribed. Thirteen days from initiation of lomustine therapy, the dog was re‐presented to the hospital with bloody diarrhea, hematemesis, epistaxis, an elevated rectal temperature, depression, severe dehydration, and marked dyspnea. The CBC showed severe thrombocytopenia and leukopenia. According to the owner, lomustine (45mg per os [PO]) was mistakenly administered daily for 10 consecutive days (total dose, 810 mg/m2). The dog died and a necropsy was performed. The main gross lesions consisted of severe multifocal hemorrhages in multiple organs, especially in the digestive system. Histopathologic evaluation revealed disseminated hemorrhages, as well as marked bone marrow aplasia. This report describes the clinical, hematologic, gross, and histologic findings in a fatal case of lomustine overdose in a dog.  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