全文获取类型
收费全文 | 2124篇 |
免费 | 123篇 |
国内免费 | 62篇 |
专业分类
林业 | 240篇 |
农学 | 69篇 |
基础科学 | 23篇 |
380篇 | |
综合类 | 184篇 |
农作物 | 115篇 |
水产渔业 | 214篇 |
畜牧兽医 | 841篇 |
园艺 | 76篇 |
植物保护 | 167篇 |
出版年
2024年 | 4篇 |
2023年 | 24篇 |
2022年 | 34篇 |
2021年 | 64篇 |
2020年 | 48篇 |
2019年 | 44篇 |
2018年 | 93篇 |
2017年 | 85篇 |
2016年 | 81篇 |
2015年 | 47篇 |
2014年 | 77篇 |
2013年 | 151篇 |
2012年 | 119篇 |
2011年 | 131篇 |
2010年 | 102篇 |
2009年 | 92篇 |
2008年 | 102篇 |
2007年 | 106篇 |
2006年 | 77篇 |
2005年 | 99篇 |
2004年 | 56篇 |
2003年 | 95篇 |
2002年 | 98篇 |
2001年 | 95篇 |
2000年 | 64篇 |
1999年 | 47篇 |
1998年 | 21篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 29篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1972年 | 5篇 |
1967年 | 9篇 |
1966年 | 6篇 |
排序方式: 共有2309条查询结果,搜索用时 15 毫秒
951.
Oilseed rape was grown under irrigated conditions at equal plant density per unit area in PVC cylinders of 1 m length with different diameter (0.11, 0.16 and 0.20m). The influence of soil volume, expressed as cylinder diameter, was found not to be significant on root dry weight, root length, root surface area or the shoot: root ratio. However, a significant influence was found on shoot and seed dry weights. It was concluded that cylinders with a length of 1 m and a diameter of a minimum of 0.11 m are appropriate for the study of container-grown root systems. 相似文献
952.
用微量乳酸脱氢酶(LDH)释放法分别观察了淫羊藿-蜂胶佐剂(以下简称“淫蜂佐剂”)对小鼠脾脏和雏鸡外周血中自然杀伤细胞(NK细胞)活性的影响。结果:小鼠NK细胞活性在淫蜂佐剂(Ⅰ)组、生理盐水对照(Ⅳ)组、淫蜂+环磷酰胺(Ⅱ)组和环磷酰胺(Ⅲ)组的上述各组间差异显著或极显著(P<0.05或P<0.01)(Ⅱ组和Ⅳ组间差异不显著,P>0.05),这种差异在4周龄小鼠较8周龄小鼠更为明显。雏鸡NK细胞活性,35日龄时,注射淫蜂佐剂雏鸡极显著高于注射生理盐水雏鸡,0.4mL/羽组明显高于0.2mL/ 羽组。上述结果表明,淫蜂佐剂能提高实验动物NK细胞活性,并拮抗环磷酰胺对NK细胞活性的抑制作用。淫蜂佐剂的这种作用在适龄的幼年动物中表现更为显著,并存在一定的量效关系。 相似文献
953.
Three experiments were performed with mice intoxicated with trichothecene-contamined feed or directly into the stomach. Lipid peroxidation was estimated by the TBA value from liver samples, but since such a test seldom provided reliable results, lipid hydroperoxides and total carbonyl were also analyzed. The formation of aldehydes and ketones was compared in vivo and in vitro. The same investigations were conducted on chickens, rainbow trouts and numerous fur animals suspected of chronic intoxication by trichothecenes. The vitamin A concentration was used as a parameter to detect alterations caused in chickens by trichothecenes. Our investigation provided evidence that lipid peroxidation is associated with trichothecene poisoning. The T-2 toxin, even in small concentrations, seems to induce strong lipid peroxidation. When DON and 3-AcDON were given together at a dosage of 180 micrograms/kg feed, 1 week's feeding caused clear lipid peroxidation in mice. Particular attention should be paid to the fact that mycotoxins may already be present in the feed before any experiment is conducted. 相似文献
954.
L B?ckstr?m D C Hoefling A C Morkoc R P Cowart 《Journal of the American Veterinary Medical Association》1985,187(7):712-715
Influence of atrophic rhinitis (AR) on mean daily weight gain (MDG) was studied in hogs randomly selected from 7 farrow-to-finish herds in Illinois. Herds were selected to obtain a wide range of clinical signs and lesions of the disease; thus, prevalence of clinical signs of AR in finishing hogs ranged from 0% to 20% among herds, and in hogs examined at slaughter the proportion of hogs with turbinate lesions ranged from 5% to 92%. None of the herds investigated had any obvious problems with pneumonia; nevertheless, hogs with moderate to severe pneumonic lesions were excluded from the study, to minimize any combined effect of AR and pneumonia. In 3 herds, MDG in AR-free pigs was 15% to 18% better than in pigs with severe AR lesions. Prevalence of clinical signs ranged from 5% to 20%, and of turbinate lesions, from 66% to 92%. In 4 herds in which MDG appeared to be unaffected by AR, prevalence of clinical signs of the disease ranged from 0% to 5%, and of turbinate lesions, from 5% to 74%. No consistent pattern of influence on AR lesions was found for bacterial infections, as determined by culturing of nasal swab specimens on MacConkey agar and blood agar. 相似文献
955.
Synovial fluid proteins in degenerative joint disease in dogs 总被引:1,自引:0,他引:1
H Str?m S Alexandersen O M Poulsen J Hau 《Veterinary immunology and immunopathology》1989,22(2):187-196
Concentrations of three immunoglobulins, albumin, ceruloplasmin, alpha-2 macroglobulin and pregnancy zone protein were estimated by immunoelectrophoresis in paired samples of synovial fluid and serum from 12 dogs with degenerative joint disease (DJD) and six normal dogs. The ratios of synovial fluid to serum concentrations (SF/S) of the four non-immunoglobulins showed an almost inverse linear relationship with their molecular weight in both groups. The SF/S were higher in the DJD synovial fluid than in normal synovial fluid. The difference increased with increasing molecular weight and was highly significant for the largest molecules, reflecting an increased permeability and inflammation in the synovial membrane of DJD joints. The SF/S ratios of the three immunoglobulins studied were compared to the diffusion curves of the four non-immunoglobulins. The SF/S ratios of IgM from dogs with DJD exceeded those calculated from the molecular weights. The present observations support the concept that DJD should be considered an inflammatory disease and suggest that immunologic processes may initiate and/or sustain the inflammation. 相似文献
956.
Comparison of conventional and long-acting oxytetracyclines in prevention of induced Actinobacillus (Haemophilus) pleuropneumoniae infection of growing swine. 下载免费PDF全文
A L Kiorpes L R Bckstrm M T Collins G O Kruse 《Canadian journal of veterinary research》1989,53(4):400-404
These experiments tested the hypothesis that long-acting oxytetracycline (oxytetracycline-LA) was more effective than regular oxytetracycline in preventing porcine pleuropneumonia when administered either 24 or 48 h prior to experimental challenge with virulent strains of Actinobacillus pleuropneumoniae. Two experiments (1 and 2) were conducted using growing pigs (average weight 12-15 kg). Antibiotic treatments were administered once intramuscularly at 20 mg/kg body weight; controls received an equivalent volume of saline. Clinical signs were recorded over seven days, and mortality rates and pathological lesions were analyzed using analysis of variance. Serum oxytetracycline levels were compared 48 and 72 h postinjection. All pigs developed clinical disease following experimental infection. Actinobacillus pleuropneumoniae was recovered from 42% of experiment 1 pigs and all of experiment 2 pigs. The data showed that both oxytetracycline and oxytetracycline-LA given at the same dose protected pigs against experimental infection when given 24 h prior to challenge, and there was no difference between the efficacy of the two drugs in this experiment. When administered 48 h prior to challenge, only oxytetracycline-LA reduced the clinical signs and pathological changes following A. pleuropneumoniae challenge. Between 48 and 72 h postinjection, oxytetracycline-LA blood levels were significantly greater compared to oxytetracycline-treated pigs. 相似文献
957.
958.
959.
960.
OBJECTIVE: To describe a surgical technique for, and outcome after, treatment of radial fractures with biodegradable self-reinforced polylactide plates and metal screws, and external coaptation. STUDY DESIGN: Prospective clinical study. SAMPLE POPULATION: Eleven Toy breed dogs. METHODS: Radial fractures were repaired by application of a single or 2 stacked biodegradable self-reinforced polylactide plates (poly-L/D, L-lactide, stereocopolymer [LL-and DL-lactide ratio 70/30]; SR-PLA (70/30) implants) secured with metal screws, and light-weight external coaptation. Healing was evaluated clinically and by radiography at 2, 4, 6, 8, 9, 12, 24-26 weeks, and at 1 and 2 years. Owners were interviewed 3 years after surgery. RESULTS: Radial fracture lines disappeared within 4-14 weeks in 10 dogs; an implant failed in 1 dog. Ambulation was excellent for healed fractures. Excessive skin tension led to removal of implants in 1 dog and suture repair in another dog. No foreign body reaction from implant degradation was observed and the plate was usually no longer palpable at 2 years. One dog had a fracture through a screw hole at 1 year. CONCLUSION: Healing and complication rates after repair of radial fractures with SR-PLA (70/30) plates were considered similar or better than reported after repair with metallic plates or external fixation in Toy breed dogs. No radiographic signs of osteopenia were identified under the plate during follow-up. CLINICAL RELEVANCE: Biodegradable polylactide plates could be considered as an alternative to metal plates for radial fracture repair in Toy breed dogs, however available plates are likely not strong enough when used as a single plate. Implant removal is usually not needed. 相似文献