全文获取类型
收费全文 | 99752篇 |
免费 | 19340篇 |
国内免费 | 31011篇 |
专业分类
林业 | 9444篇 |
农学 | 8423篇 |
基础科学 | 9844篇 |
36734篇 | |
综合类 | 44439篇 |
农作物 | 8072篇 |
水产渔业 | 7309篇 |
畜牧兽医 | 13259篇 |
园艺 | 5150篇 |
植物保护 | 7429篇 |
出版年
2024年 | 1240篇 |
2023年 | 1735篇 |
2022年 | 2962篇 |
2021年 | 2700篇 |
2020年 | 4180篇 |
2019年 | 7352篇 |
2018年 | 6709篇 |
2017年 | 8147篇 |
2016年 | 8413篇 |
2015年 | 9042篇 |
2014年 | 8246篇 |
2013年 | 8823篇 |
2012年 | 9570篇 |
2011年 | 8597篇 |
2010年 | 7372篇 |
2009年 | 6661篇 |
2008年 | 5629篇 |
2007年 | 5433篇 |
2006年 | 4674篇 |
2005年 | 4017篇 |
2004年 | 3474篇 |
2003年 | 2785篇 |
2002年 | 2485篇 |
2001年 | 2079篇 |
2000年 | 1823篇 |
1999年 | 1479篇 |
1998年 | 1253篇 |
1997年 | 1252篇 |
1996年 | 1107篇 |
1995年 | 1169篇 |
1994年 | 1149篇 |
1993年 | 907篇 |
1992年 | 931篇 |
1991年 | 782篇 |
1990年 | 600篇 |
1989年 | 590篇 |
1988年 | 531篇 |
1987年 | 396篇 |
1986年 | 402篇 |
1985年 | 212篇 |
1984年 | 196篇 |
1983年 | 190篇 |
1982年 | 191篇 |
1981年 | 231篇 |
1980年 | 192篇 |
1979年 | 150篇 |
1978年 | 130篇 |
1975年 | 109篇 |
1965年 | 137篇 |
1964年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Destruction of Trichinella spiralis spiralis during the preparation of the "dry cured" pork products proscuitto, proscuittini and Genoa salami 总被引:1,自引:1,他引:0 下载免费PDF全文
Genoa salami, proscuittini and proscuitto were prepared from pork carcasses that were heavily infected experimentally with Trichinella spiralis spiralis. Genoa salami was prepared with salt concentrations of 2.0%, 2.75% and 3.3%. Proscuitto was prepared by two procedures approved by Agriculture Canada. At various times postpreparation, samples of the various cured products were taken and examined by pepsin digestion and rat bioassay for the presence of viable trichinae. Water activity and pH of the cured meat were also determined. Curing of the various products was shown to destroy the Trichinella larvae. Pepsin digestion revealed that larvae progressively became loosely coiled, uncoiled and more subject to digestion (ghost larvae) during the curing process. Rat bioassay revealed the presence of viable trichinae in the proscuitto prepared using a sodium chloride salt mixture at day 34 but not at day 48 postpreparation. All other bioassays carried out on Genoa salami between 13 and 42 days postpreparation, on proscuittini between days 27 and 69 and on proscuitto between days 34 and 69 were negative for viable trichinae. Under the conditions of this study, preparing Genoa salami with salt concentrations as low as 2% did not appear to affect the destruction of Trichinella larvae. 相似文献
62.
64.
Daniel J. Burba DVM Michael A. Collier DVM Lawrence E. Default PhD Olivia Hanson-Painton PhD Harold C. Thompson Jr. Claude L. Holder 《Journal of Equine Veterinary Science》1993,13(12):696-703
The uptake and distribution of intramuscularly (IM) administered tritium-labeled polysulfated glycosaminoglycan (3H-PSGAG) in serum, synovial fluid, and articular cartilage of eight horses was quantitated, and hyaluronic acid (HA) concentration of the middle carpal joint was evaluated in a pharmacokinetic study. A full-thickness articular cartilage defect, created on the distal articular surface of the left radial carpal bone of each horse served as an osteochondral defect model. 3H-PSGAG (500 mg) was injected IM, between 14 and 35 days after creation of the defects. Scintillation analysis of serum and synovial fluid, collected from both middle carpal joints at specific predetermined times up to 96 hours post-injection, revealed mean 3H-PSGAG concentrations peaked at 2 hours post-injection. 3H-PSGAG was detected in cartilage and subchondral bone 96 hours post-injection in samples from all eight horses. There were no statistically significant differences in 3H-PSGAG concentration of synovial fluid or cartilage between cartilage defect and control (right middle carpal) joints.
HA assay of synovial fluid revealed concentrations significantly increased at 24, 48, and 96 hours post-injection in both joints. The concentration nearly doubled 48 hours post-injection. However, no statistically significant differences were found between synovial concentrations of HA in cartilage defect and control joints.
3H-PSGAG administered IM to horses, was distributed in the blood, synovial fluid, and articular cartilage. HA concentrations in synovial fluid increased after IM administration of polysulfated glycosaminoglycan. 相似文献
65.
66.
In vitro viability of cryopreserved equine embryos following different freezing protocols. 下载免费PDF全文
P Poitras P Guay D Vaillancourt N Zidane M Bigras-Poulin 《Canadian journal of veterinary research》1994,58(4):235-241
The main objective of this study was to evaluate two freezing protocols and the effect of agar embedding on survival of day 6.5 equine embryos. A total of 133 embryos were used, in one group (n = 51), embryos were first embedded in agar before the freezing protocol was started. A freezing protocol to -30 degrees C or -33 degrees C was used before plunging embryos into liquid nitrogen (LN2). The embryos were thawed in water at 37 degrees C, evaluated and placed in culture. After 24 h culture, the embryos were evaluated for their morphology and development. No differences were observed between embryos plunged at -30 degrees or at -33 degrees C in LN2. The analysis of the morphology and development after thawing showed that the diameter and developmental stage at freezing correlated with embryo survival. Morula and early blastocyst stages of development were associated with better quality after freezing and thawing and had a better potential to survive after in vitro culture (p < 0.05) compared to more advanced stages. The agar failed to protect embryos from zona pellucida damage, but a tendency to prevent rupture was observed in larger embedded embryos. 相似文献
67.
68.
Effects of aminoglycoside antibiotics on renal antioxidants, malondialdehyde levels, and some serum biochemical parameters 下载免费PDF全文
Enver Yazar Muammer Elmas Vahdettin Altunok Abdullah Sivrikaya Esma Oztekin Yavuz Osman Birdane 《Canadian journal of veterinary research》2003,67(3):239-240
Effects of amikacin, gentamicin, kanamycin, and streptomycin on renal tissue superoxide dismutase, glutathione peroxidase, glutathione and malondialdehyde, serum creatinine, potassium, sodium, total protein, glucose, uric acid, and total bilirubin levels were investigated. All aminoglycoside antibiotics decreased renal tissue glutathione levels. 相似文献
69.
家兔选育性状典型相关分析 总被引:3,自引:0,他引:3
选择日本大耳白和新西兰两个品种家兔的生长、繁殖、以及体尺3组共17个性状,应用多元统计方法进行了典型相关分析,结果表明;日本大耳白兔的初生重、初生窝重、21日龄重、泌乳力、胸围等5个性状,新西兰兔的产活仔数、初生重、21日龄重、泌乳力、断奶窝重、母兔体重等6个性状为主要性状。 相似文献
70.
JEV、PPV、PRRSV、PRV多联PCR的应用研究 总被引:3,自引:0,他引:3
用 JEV、PRRSV二联 PCR,PPV、PRV二联 PCR以及这 4种病毒 4联 PCR对来自内蒙、广州、广西、天津、北京、吉林病料进行检测 ,共检了 1 4 6份病料。其中 PRRSV阳性 7份 ,PPV阳性 1 2份 ,PRV阳性 2 1份 ,PRV和 PPV混合感染 4份。并对 5份人工接种 JEV小鼠病料检测 ,其中 4份为阳性。随后对部分阳性 PCR扩增产物进行点杂交和核苷酸测序鉴定 ,证实了 PCR扩增准确性。对内蒙 PRRSV阳性扩增带测序结果显示 ,我国流行 PRRSV为美洲型 ,在扩增片段的核苷酸序列上有 3个碱基差异 相似文献