全文获取类型
收费全文 | 4553篇 |
免费 | 427篇 |
国内免费 | 1篇 |
专业分类
林业 | 405篇 |
农学 | 183篇 |
基础科学 | 35篇 |
1141篇 | |
综合类 | 160篇 |
农作物 | 281篇 |
水产渔业 | 609篇 |
畜牧兽医 | 1680篇 |
园艺 | 97篇 |
植物保护 | 390篇 |
出版年
2024年 | 8篇 |
2023年 | 49篇 |
2022年 | 75篇 |
2021年 | 151篇 |
2020年 | 163篇 |
2019年 | 186篇 |
2018年 | 234篇 |
2017年 | 261篇 |
2016年 | 246篇 |
2015年 | 183篇 |
2014年 | 226篇 |
2013年 | 297篇 |
2012年 | 341篇 |
2011年 | 387篇 |
2010年 | 213篇 |
2009年 | 174篇 |
2008年 | 288篇 |
2007年 | 242篇 |
2006年 | 210篇 |
2005年 | 180篇 |
2004年 | 147篇 |
2003年 | 144篇 |
2002年 | 137篇 |
2001年 | 104篇 |
2000年 | 84篇 |
1999年 | 46篇 |
1998年 | 18篇 |
1997年 | 23篇 |
1996年 | 8篇 |
1995年 | 21篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1970年 | 2篇 |
1934年 | 2篇 |
1926年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有4981条查询结果,搜索用时 0 毫秒
11.
Pigatto JA Andrade MC Laus JL Santos JM Brooks DE Guedes PM Barros PS 《Veterinary ophthalmology》2004,7(3):205-208
The objective of this study was to examine the endothelial surface morphology and to perform morphometric analysis of the corneal endothelial cells of Yacare caiman (Caiman yacare) using scanning electron microscopy. Morphometric analysis with regard to polygonality, mean cell area, cell density and coefficient of variation of mean cell area was performed. Cell areas were measured using image analysis software. The normal corneal endothelium of Yacare caiman consisted of polygonal cells of uniform size and shape with interdigitations of the cell borders. Microvilli appeared as protrusions on the cellular surface. The average cell area was 270 +/- 24 microm(2) and the endothelial cell density was 3704 +/- 324 cells/mm(2). The coefficient of variation of cell area was 0.22. This study demonstrates that the Yacare caiman corneal endothelium is similar to those described in other vertebrates. 相似文献
12.
Genetic diversity,anti‐microbial resistance,plasmid profile and frequency of the Vi antigen in Salmonella Dublin strains isolated in Brazil 下载免费PDF全文
F. P. Vilela M. R. Frazão D. P. Rodrigues R. G. Costa M. R. T. Casas S. A. Fernandes J. P. Falcão F. Campioni 《Zoonoses and public health》2018,65(1):e34-e43
Salmonella Dublin is strongly adapted to cattle causing enteritis and/or systemic disease with high rates of mortality. However, it can be sporadically isolated from humans, usually causing serious disease, especially in patients with underlying chronic diseases. The aim of this study was to molecularly type S. Dublin strains isolated from humans and animals in Brazil to verify the diversity of these strains as well as to ascertain possible differences between strains isolated from humans and animals. Moreover, the presence of the capsular antigen Vi and the plasmid profile was characterized in addition to the anti‐microbial resistance against 15 drugs. For this reason, 113 S. Dublin strains isolated between 1983 and 2016 from humans (83) and animals (30) in Brazil were typed by PFGE and MLVA. The presence of the capsular antigen Vi was verified by PCR, and the phenotypic expression of the capsular antigen was determined serologically. Also, a plasmid analysis for each strain was carried out. The strains studied were divided into 35 different PFGE types and 89 MLVA‐types with a similarity of ≥80% and ≥17.5%, respectively. The plasmid sizes found ranged from 2 to >150 kb and none of the strains studied presented the capsular antigen Vi. Resistance or intermediate resistance was found in 23 strains (20.3%) that were resistant to ampicillin, ciprofloxacin, chloramphenicol, imipenem, nalidixic acid, piperacillin, streptomycin and/or tetracycline. The majority of the S. Dublin strains studied and isolated over a 33‐year period may descend from a common subtype that has been contaminating humans and animals in Brazil and able to cause invasive disease even in the absence of the capsular antigen. The higher diversity of resistance phenotypes in human isolates, as compared with animal strains, may be a reflection of the different anti‐microbial treatments used to control S. Dublin infections in humans in Brazil. 相似文献
13.
Szabó MP Mangold AJ João CF Bechara GH Guglielmone AA 《Veterinary parasitology》2005,130(1-2):131-140
In this work, the biology, mitochondrial DNA and fertility of hybrids from two strains of Rhipicephalus sanguineus, from Brazil and Argentina, were compared. Engorged larvae, nymphs and adults from Argentina weighed more and the engorgement period of adult females was significantly longer than those of their Brazilian counterparts, whereas adult female tick yield rate was higher for the Brazilian strain. High intraspecific divergence of mitochondrial DNA was detected between R. sanguineus from Brazil and Argentina. On the other hand, a strong genetic relationship was detected between European and Argentinean R. sanguineus populations while the Brazilian population appeared to be related to the African Rhipicephalus turanicus. Adult hybrid females laid eggs, which were mostly unviable, whereas a mean of more than 1400 larvae hatched per egg mass from pure Brazilian and Argentinean strains. These results showed that differences between these strains are greater than previously assumed and that the biosystematic status of R. sanguineus ticks from South America should be re-evaluated. Wide variations, such as these might account for the reported worldwide differences in biology and vector capacity of this species. 相似文献
14.
Genetic parameters, breeding values, and genetic trends of hip dysplasia in Estrela Mountain Dogs were estimated using a linear model (LM) and a threshold model (TM). A database with 313 animals was used. Right and left hip joints were individually scored, according to the Fédération Cynologic Internationale grading rules of the canine hip dysplasia system, as normal (1), borderline (2), slight (3), moderate (4), and severe (5 and 6). The estimate of repeatability was lower in LM (0.86) than in TM (0.90). The same tendency was verified with the heritability because its estimate in LM was 0.38 and in TM was 0.43. However, these results did not establish any statistical differences between the models. The genetic trend of canine hip dysplasia for LM and TM showed a similarity in shape, but considerable individual differences were found in the EBV ranking lists. Therefore, the selection of breeding animals would not be the same with the 2 methodologies. To select the best method for genetic evaluation of hip dysplasia, further studies using more data and other dog breeds are required. 相似文献
15.
Canine monocytic ehrlichiosis (CME) is a tick-borne disease caused by the rickettsia Ehrlichia canis. Ocular lesions are a common feature of the disease and can be present in all stages. The purpose of this retrospective study was to determine the prevalence, type and response to treatment of ocular lesions associated with monocytic ehrlichiosis in 46 affected dogs presented to the Autonomous University of Barcelona-Veterinary Teaching Hospital (UAB-VTH) from January 2000 to December 2002. Dogs were included in the study only if they had a positive serologic test for E. canis and information about the clinical outcome was available. Eighteen breeds were represented, with the German Shepherd dog (n = 6) being the most common. There were 25 intact and three castrated males, and 16 intact and two neutered females. Twenty dogs (43.4%) were between 5 and 10 years old. Seventeen dogs (37% of all cases of monocytic ehrlichiosis diagnosed during the study period) had ocular signs, and 11 dogs (64.7% of the ocular cases) had only ocular lesions without apparent systemic signs. Exudative retinal detachment was the most common ocular manifestation; other prevalent findings included anterior exudative uveitis and optic neuritis. Five of the 17 cases with ocular lesions (29.4%) had ocular bleeding disorders (hyphema or retinal hemorrhages). All the dogs with ocular disease presented with bilateral signs. Dogs with posterior segment disease had titers against E. canis that were > or = 1 : 320, while lower titers were noted in dogs with anterior exudative uveitis. Two dogs presented with chronic autoimmune panuveitis after ehrlichiosis treatment. Canine ehrlichiosis should be considered in the differential diagnosis of exudative retinal detachment and anterior uveal inflammatory lesions. 相似文献
16.
S. Avendaño J.A. Woolliams & B. Villanueva 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2005,122(5):302-308
This study describes a general framework for predicting the accuracy of Mendelian sampling terms when truncation selection is applied on best linear unbiased prediction (BLUP) estimated breeding values. A selection index approach is followed. The pseudo‐BLUP index is extended to include terms related to the Mendelian sampling term. Predicted accuracies are compared with those obtained through stochastic computer simulation. Good predictions for the accuracy of the Mendelian sampling term were obtained both at selection time and at convergence of long‐term contributions of selected candidates for a range of heritabilities and population structures. The prediction approach developed provides a key tool for obtaining predictions of genetic response from quadratic optimization that maximizes the rate of genetic progress while restricting the rate of inbreeding. 相似文献
17.
Gremião I Schubach T Pereira S Rodrigues A Honse C Barros M 《Australian veterinary journal》2011,89(9):346-351
OBJECTIVE To describe the use of intralesional amphotericin B in localised lesions for the treatment of 26 cats from Rio de Janeiro, Brazil, with sporotrichosis refractory to oral itraconazole. DESIGN Uncontrolled intervention study. METHOD The 26 cats in this study were diagnosed with sporotrichosis, confirmed by isolation of Sporothrix schenckii, and presented residual localised skin lesions refractory to treatment with oral itraconazole for a minimum period of 8 weeks. The animals received weekly applications of intralesional amphotericin B in conjunction with oral itraconazole. In cases of owner unavailability, a maximum of 2 weeks between the infiltrations was accepted. RESULTS Twenty-two (84.6%) of the 26 treated cats achieved clinical remission, 16 (72.7%) of which were cured, and in the remaining six (27.3%) the lesions recurred at the same site. Lack of clinical response was observed in one animal and three owners abandoned treatment. CONCLUSION The proposed therapeutic regimen is an adjunctive treatment option for cats with sporotrichosis presenting as residual skin lesions refractory to itraconazole. 相似文献
18.
Hartwell Birgitte Wiedemann Iñiguez Luis Mueller Joaquin Wurzinger Maria Knaus W. F. 《Tropical animal health and production》2010,42(7):1573-1578
Intensive lamb fattening systems are evolving in developing Middle Eastern countries due to high demand for lambs at favorable
prices; however, little is known about their characteristics and constraints. A survey was conducted in Syria involving 241
farmers to characterize the fattening production systems and main constraints, with emphasis on feeding, management, labor,
and marketing. Most farmers (90%) considered the income from fattening to be from medium to high, and 57% expressed that lamb
fattening along with alternative income sources compose the family's livelihood strategies. Fattening systems offer employment
to family members. Market price was the main decision factor to buy and sell lambs, but this was only part of various marketing
aspects. Male lambs usually bought at markets at the mean age of 4 months (mean weight of 31 kg) are sold after fattening
at a 50–60 kg weight range. The average yearly fattening cycle was 2.7 batches, and the average number of lambs per batch
was 232. For 65% (n = 241) of the farmers the major constraint to fattening was feeding cost, and for about a half of farmers (51%, n = 241), disease outbreaks and prices for veterinarian services constituted the second important constraint. Research on least-cost
fattening diets and curbing disease problems to increase farmer's income margins is needed. It is expected that due to existing
commonalities, the information emerging from this study regarding major constraints to Awassi lamb fattening systems could
be useful for an across-synthesis on Awassi fattening production in the region. 相似文献
19.
This paper reviews the epidemiology of bovine, swine, ovine, caprine, and canine brucellosis in Brazil. The zoonotic aspects of Brucella infection in Brazil is also discussed. Emphasis is given to the new program for the control of brucellosis in cattle and buffaloes that is likely to provide important insights into the prospects and strategies for controlling brucellosis in developing countries. 相似文献
20.