全文获取类型
收费全文 | 105549篇 |
免费 | 5431篇 |
国内免费 | 52篇 |
专业分类
林业 | 4309篇 |
农学 | 3040篇 |
基础科学 | 729篇 |
11682篇 | |
综合类 | 20721篇 |
农作物 | 4294篇 |
水产渔业 | 4619篇 |
畜牧兽医 | 54328篇 |
园艺 | 1195篇 |
植物保护 | 6115篇 |
出版年
2018年 | 1204篇 |
2017年 | 1331篇 |
2016年 | 1284篇 |
2015年 | 1090篇 |
2014年 | 1260篇 |
2013年 | 3931篇 |
2012年 | 2564篇 |
2011年 | 3184篇 |
2010年 | 2077篇 |
2009年 | 2054篇 |
2008年 | 3205篇 |
2007年 | 2937篇 |
2006年 | 2801篇 |
2005年 | 2637篇 |
2004年 | 2744篇 |
2003年 | 2678篇 |
2002年 | 2622篇 |
2001年 | 3273篇 |
2000年 | 3289篇 |
1999年 | 2440篇 |
1998年 | 1070篇 |
1997年 | 1081篇 |
1995年 | 1251篇 |
1994年 | 1164篇 |
1993年 | 1121篇 |
1992年 | 2362篇 |
1991年 | 2530篇 |
1990年 | 2438篇 |
1989年 | 2493篇 |
1988年 | 2272篇 |
1987年 | 2349篇 |
1986年 | 2484篇 |
1985年 | 2394篇 |
1984年 | 1920篇 |
1983年 | 1773篇 |
1982年 | 1165篇 |
1981年 | 1123篇 |
1980年 | 1025篇 |
1979年 | 1762篇 |
1978年 | 1424篇 |
1977年 | 1146篇 |
1976年 | 1130篇 |
1975年 | 1165篇 |
1974年 | 1524篇 |
1973年 | 1610篇 |
1972年 | 1584篇 |
1971年 | 1515篇 |
1970年 | 1408篇 |
1969年 | 1262篇 |
1967年 | 1094篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
991.
Sidibe M Boly H Lakouetené T Leroy P Bosma RH 《Tropical animal health and production》2004,36(1):95-100
Peri-urban dairy cattle farms within 50 km of Bobo-Dioulasso were studied to assess herd type, disease incidence, management, feeding and breeding strategy. Out of 417 cattle farmers, 42% had dairy objectives and were studied. Among these peri-urban dairy farmers, 60% were settled, 36% semi-settled, and 4% transhumant. In total, they held 4558 dairy cows, of which 32% lactated during the study. The prevalence of mastitis (55%) increased (p<0.05) with herd size. Advanced strategies for supplementary feeding and breeding were most frequent in small herds (<30 cattle). None of the large herds (>60 cattle) had advanced breeding strategies. Bulls and cows were culled at younger ages in herds with better breeding strategy. Overall, this resulted in higher individual milk offtake in small herds (2.46 L/day) compared with large herds (1.25 L/day). Pure breeds were rarely used, and the presence of Bos taurus baoulé naturally selected for trypanotolerance was low. The prevalence of trypanosomosis (40%) in herds dominated by Bos indicus zebu and Méré (Zebu x Baoulé) is an argument for maintenance of biodiversity and selection of Baoulé for milk production. 相似文献
992.
Burkholder WJ Lees GE LeBlanc AK Slater MR Bauer JE Kashtan CE McCracken BA Hannah SS 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2004,18(2):165-175
Young adult heterozygous (carrier) female dogs with X-linked hereditary nephropathy (XLHN) have glomerular proteinuria but are otherwise healthy. Because data regarding dietary influences on the magnitude of proteinuria in dogs with spontaneous glomerular disease are not available, 12 such dogs were studied in a double crossover experiment intended to determine effects of altering dietary protein intake for up to 6 weeks. Dogs were blocked by urine protein : creatinine ratio (UPC) and randomly assigned to receive 2 diets: high protein (34.6% dry matter [DM], HP) or low protein (14.1% DM, LP) fed in HP-LP-HP or LP-HP-LP sequence. Food intake was measured daily, body weight (BW) was measured twice weekly, and UPC, plasma creatinine, blood urea nitrogen, phosphorus, albumin, and protein concentrations were measured at 2-week intervals. Nutrient digestibility was measured during the third treatment period. Diet had a significant effect (P < .0001) on all measured variables except plasma phosphorus (P > .5), but unintended differences in digestibility of protein and energy (P < or = .01) prevented assignment of the diet effect exclusively to protein. Proteinuria was greater (UPC 4.7 +/- 2.2 versus 1.8 +/- 1.1, P < .0001) when the HP diet was fed, but the LP diet did not maintain starting BW or plasma albumin concentration within the normal reference range. Diet greatly affects the magnitude of proteinuria in XLHN carrier females. Dietary protein restriction can reduce proteinuria in dogs with glomerular disease, but BW and blood protein concentrations may not be maintained if the restriction is too severe. 相似文献
993.
Wakeley PR Turner JL Ibata G King DP Sandvik T Howard P Drew TW 《Veterinary microbiology》2004,102(1-2):19-24
Two genotypes of bovine viral diarrhoea virus (BVDV) are recognised. Type 2 was first recognised when virulent strains caused significant losses among cattle in North America. Subsequently, BVDV type 2 has been found in many other countries, but recent studies have shown that only type 1 BVDV is circulating in the UK herds (sheep and cattle) with type 1a predominating. During routine genotyping of UK BVDV isolates, a type 2 isolate was identified. Phylogenetic analysis of the 5'-untranslated region of the viral genome showed it to be a BVDV type 2a, most similar to a low virulent US strain of BVDV type 2. Antigenic typing with a panel of monoclonal antibodies verified this classification. This is the first confirmed isolation of BVDV type 2 found circulating in the UK. 相似文献
994.
Necrotising fasciitis and necrotising myositis are rare but serious life threatening conditions reported mainly in human beings and dogs. Most cases to date have been caused by beta-haemolytic streptococci of Lancefield groups A, B, C or G. Necrotising fasciitis has been reported only twice in cats and necrotising myositis has never been described. This paper describes a fatal case of necrotising fasciitis and myositis with pneumonia and septicaemia in a nine-year-old cat. The cat had been undergoing treatment for a suspected tear of the cranial cruciate ligament, but on the seventh day of treatment it suddenly deteriorated and died. On postmortem examination, there was an area of hair loss from its left hindlimb and discoloration of the underlying fascia and biceps femoris muscle. Severe necrotising fasciitis and myositis, with numerous intralesional Gram-positive coccoid bacteria, was diagnosed histologically. Other findings included necrotising pneumonia, pleuritis, focal encephalitis, myocarditis and nephritis. Culture of the affected tissues yielded a pure, heavy growth of Streptococcus canis. 相似文献
995.
Dogs that participate in animal-assisted interventions (AAIs), often called 'therapy dogs', commonly interact with humans whose immune systems are not functioning optimally. The advisability of feeding raw meat (including poultry) to these animals remains a highly contentious issue, in spite of increasing evidence that raw meat is frequently contaminated with Salmonella. We set out to determine if consuming raw meat influences the risk of therapy dogs shedding Salmonella and other pathogens. Two hundred healthy therapy dogs from Ontario and Alberta were enrolled. Between May 2005 and November 2006, fecal specimens were collected from each dog every 2 months for 1 year, along with a log of places visited, antimicrobial use within the home, dog health status and diet. Specimens were cultured for Salmonella, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), extended-spectrum cephalosporinase (ESC) Escherichia coli and Clostridium difficile. Forty (20%) of the dogs were reported to have been fed raw meat at some point during the year. The incidence rate of Salmonella shedding in the raw meat-fed dogs was 0.61 cases/dog-year, compared with 0.08 cases/dog-year in dogs that were not fed raw meat (P < 0.001). Controlling for therapy dog group, the repeated measures, and pig ear consumption and diarrhoea in the 2 months prior to specimen submission, dogs that consumed raw meat were significantly more likely to test positive for Salmonellaat least once during the year than dogs that did not eat raw meat [odds ratio (OR) 22.7; 95% confidence interval (CI) 3.1-58.8; P < 0.001]. Specific Salmonella serovars were more common among dogs that consumed raw meat versus those that did not include S. Typhimurium, S. Heidelberg and S. Kentucky. Raw meat consumption was also significantly associated with shedding ESC E. coli (OR 17.2; 95% CI 9.4-32.3). No associations between C. difficile, MRSA or VRE and consumption of raw meat were detected. We recommend that dogs fed raw meat should be excluded from AAI programmes, particularly when the programmes involve interaction with humans at high risk of infection or adverse sequelae attributable to infection. Furthermore, although AAI dogs may not be representative of the general population of dogs, we also recommend that feeding of raw meat to dogs is to be avoided in homes where immunocompromised people live. 相似文献
996.
Edwards DS Coyne K Dawson S Gaskell RM Henley WE Rogers K Wood JL 《Preventive veterinary medicine》2008,87(3-4):327-339
Feline upper respiratory tract disease (URTD), mainly caused by feline calicivirus (FCV) and feline herpesvirus, is a major cause of disease outbreaks in feline accommodation such as animal shelters, catteries and multi-cat households. We conducted a longitudinal, yearlong study in five UK feline animal shelters to identify risk factors for the time to diagnosis of URTD. We were especially interested in risk factors that could be identified at the time the cat entered the shelter. Shelter staff recorded data for 1434 cats during 2002–2003. Most of the cats were domestic shorthair cats and were from private households, or were stray or abandoned. Sixty cats without clinical signs of URTD at entry had URTD diagnosed (typically within the first month at the centre). We used two multivariable models: one was a Cox proportional-hazards model, and the other a regression analyses with complementary log–log model.The hazard varied substantially between shelters and was considerably lower for the shelter that had a purpose-built admissions unit with its own isolation facilities. The hazard was greater for purebred cats (HR 4.3–5.0) and for neutered cats (HR 2.0). The hazard was also typically greater if the centre had a greater proportion of cats present with URTD. The analyses suggested that the centre-level risk factors were more important in determining hazard than cat-level risk factors. 相似文献
997.
A.R. Elbeltagy Salah Galal A.Z. Abdelsalam F.E. El Keraby M. Blasi Mahasen M. Mohamed 《Livestock Science》2008,114(2-3):341-346
The present study was carried out to investigate genetic diversity in Nile-Delta and Southern-Egypt buffalo populations in comparison with the Italian buffalo utilizing two microsatellite multiplexes. A total of 104 animals classified into three groups were used, 28, 38 and 38 representing the Nile-Delta, Southern-Egypt and Italian buffalo, respectively. The 15 studied microsatellites were CSSM38, CSSM70, CYP21, CSSM42, CSSM60, MAF65, BM0922, CSSM19, INRA006, ETH02, BM1706, BMC1013, CSSM47, INRA026 and CA004. All studied microsatellites showed allelic polymorphism. Number of polymorphic alleles ranged between 4 alleles (CSSM38, CSSM70 and CYP21) and 11 alleles (CA004). Pairwise Chi-square test for Nile Delta and Southern Egypt showed significant differences in allelic distribution at five loci, CSSM70, CSSM38, BM0922, ETH02 and BM1706. Italian buffalo showed the lowest percentage of observed heterozygotes (65%), while the Southern Egypt showed the highest (71%). Both the Italian and the Delta populations deviated significantly (P < 0.05) from HW equilibrium. Italian buffalo is relatively the most inbred population while the Southern-Egypt buffalo is the only outbred population. High level of genetic differentiation (FST estimates) between the Italian group and each of the Delta and Southern-Egypt group (0.083 and 0.076, respectively) was observed while Southern-Egypt group showed a lower level of genetic differentiation with the Delta group (0.014). Italian buffalo had the greatest genetic distance values with the two Egyptian groups (0.25 and 0.23) while much lower values between the Southern-Egypt and the Delta groups (0.06) was observed. Genetic variation between the Italian buffalo and the Egyptian buffalo was detected in 14 (out of 15) microsatellite loci. While a lower level (than that between Egyptian and Italian) of genetic variation between Southern-Egypt and Delta buffalo populations was expressed by 5 loci. It was concluded that the Southern-Egypt buffalo could be considered as distinct population from the Delta buffalo. In addition, Southern-Egypt group, being the only group with non-significant global deviation from HW equilibrium, the most heterozygous, and the only outbred population as well, is expected to respond more favorably to selection. 相似文献
998.
Patrice M Mich Lisa L Wolfe Tracey M Sirochman Michael A Sirochman Tracy R Davis William R Lance Michael W Miller 《Journal of zoo and wildlife medicine》2008,39(3):480-487
Chemical immobilization of wildlife often includes opioids or cyclohexamines. These substances are problematic as a result of their required storage, handling, and record-keeping protocols. A potentially useful alternative sedation protocol includes a combination of butorphanol, azaperone, and medetomidine (BAM: 0.43 mg/kg butorphanol, 0.36 mg/kg azaperone, 0.14 mg/kg medetomidine). One risk of wildlife immobilization with any drug combination is hypoxemia. This may be of particular importance when using an alpha 2 agonist such as medetomidine because of its powerful vasoconstrictive effect. In this prospective study, the BAM combination was evaluated for chemical immobilization of white-tailed deer. Additionally, selected physiologic parameters associated with BAM immobilization, including oxygen saturation via pulse oximetry and arterial blood gas measurement, with and without nasal insufflation of oxygen at a relatively low flow of 3 L/min, were evaluated. The BAM combination resulted in a predictable onset of sedation, with a mean induction time to lateral recumbency of 9.8 +/- 3.6 min. All deer recovered smoothly within a range of 5-20 min after reversal with intramuscular administration of naltrexone, atipamazole, and tolazoline (NAT). Clinically relevant decreases in arterial partial pressure of oxygen (PaO2) and oxygen saturation (SpO2) were observed in animals not receiving supplemental oxygen, while both parameters significantly improved for oxygen-supplemented deer. Pulse oximetry with this protocol was an unreliable indicator of oxygen saturation. In this study, altitude, recumbency, hypoventilation, butorphanol- and medetomidine-specific effects, as well as the potential for alpha 2 agonist-induced pulmonary changes all may have contributed to the development of hypoxemia. Overall, capture of white-tailed deer with the BAM/NAT protocol resulted in excellent chemical immobilization and reversal. Because the BAM combination caused significant hypoxemia that is unreliably detected by pulse oximetry but that may be resolved with nasal oxygen insufflation, routine use of oxygen supplementation is recommended. 相似文献
999.
R. Vivancos D. Showell B. Keeble S. Goh M. Kroese A. Lipp J. Battersby 《Zoonoses and public health》2011,58(2):126-130
Avian influenza is a highly infectious disease in poultry and although the risk of human infection is low, concerns exist that it could evolve into a new human strain of pandemic potential if reassortment with a human influenza virus occurs. In January 2007, the UK government introduced a programme to vaccinate poultry workers to reduce the potential of such an event. This study evaluates the delivery, uptake and costs of the programme in three counties of England. A questionnaire survey was completed by consultants in public health in all the Primary Care Trusts in Norfolk, Suffolk and Cambridgeshire in May 2007. The delivery of the programme varied between Primary Care Trusts, including being delivered in some cases by clinics in primary care, by general practitioners and occupational health services in others. The uptake of vaccination was low ranging from 7% to 29% at a cost of £29 to £132 per person vaccinated. Vaccination of poultry workers as a public health measure to prevent an influenza pandemic is likely to be ineffective with the level of coverage found in this evaluation in our region. 相似文献
1000.