全文获取类型
收费全文 | 1329篇 |
免费 | 80篇 |
国内免费 | 1篇 |
专业分类
林业 | 73篇 |
农学 | 36篇 |
基础科学 | 8篇 |
134篇 | |
综合类 | 335篇 |
农作物 | 86篇 |
水产渔业 | 46篇 |
畜牧兽医 | 588篇 |
园艺 | 21篇 |
植物保护 | 83篇 |
出版年
2023年 | 10篇 |
2022年 | 14篇 |
2021年 | 25篇 |
2020年 | 27篇 |
2019年 | 36篇 |
2018年 | 30篇 |
2017年 | 27篇 |
2016年 | 28篇 |
2015年 | 32篇 |
2014年 | 26篇 |
2013年 | 43篇 |
2012年 | 52篇 |
2011年 | 53篇 |
2010年 | 33篇 |
2009年 | 27篇 |
2008年 | 58篇 |
2007年 | 49篇 |
2006年 | 41篇 |
2005年 | 40篇 |
2004年 | 39篇 |
2003年 | 37篇 |
2002年 | 36篇 |
2001年 | 22篇 |
2000年 | 34篇 |
1999年 | 20篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1992年 | 31篇 |
1991年 | 21篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 20篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1979年 | 12篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 12篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1971年 | 15篇 |
1970年 | 19篇 |
1969年 | 29篇 |
1968年 | 38篇 |
1967年 | 35篇 |
1966年 | 21篇 |
排序方式: 共有1410条查询结果,搜索用时 343 毫秒
21.
Nelson B 《Science (New York, N.Y.)》1968,162(3854):653-655
22.
Nelson B 《Science (New York, N.Y.)》1970,169(3945):567-569
23.
Metabolism stall for male equine 总被引:1,自引:0,他引:1
24.
25.
Nelson B 《Science (New York, N.Y.)》1967,155(3769):1521-1525
26.
Davis MS Willard MD Nelson SL Mandsager RE McKiernan BS Mansell JK Lehenbauer TW 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(3):311-314
Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large. 相似文献
27.
28.
Campylobacter jejuni, a foodborne pathogen closely associated with market poultry, is considered to be the most frequent agent of human gastroenteritis in the United States. The pathways involved in the contamination of poultry flocks, vertical transmission and/or horizontal transmission, are unclear. In this study, Campylobacter isolates from two independent commercial broiler breeder flocks, as well as from their respective progeny, were characterized and compared by PstI ribotype analysis and by DNA sequence analysis of the short variable region (SVR) of the flaA gene (flaA SVR). Campylobacter isolates originating from one set of breeder hens and the feces from their respective progeny demonstrated identical ribotype patterns as well as identical flaA SVR DNA sequences, thereby suggesting that these isolates were clonal in origin. Ribotype analysis of Campylobacter isolates from the second set of breeder hens and processed carcasses from their offspring resulted in two patterns. Sequence analysis placed these isolates into two closely related groups and one distant group, similar to the ribotype analysis. These results demonstrate that Campylobacter isolates from commercial broiler breeder flocks and from the respective broiler progeny may be of clonal origin and that breeder hens can serve as a source for Campylobacter contamination in poultry flocks. 相似文献
29.
Jankowski MK Ogilvie GK Lana SE Fettman MJ Hansen RA Powers BE Mitchener KM Lovett SD Richardson KL Parsley L Walton JA 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2002,16(1):105-108
Matrix metalloproteinases (MMPs) are enzymes that play key roles in angiogenesis, tumor invasion, and metastasis in a wide variety of species. The purpose of this study was to evaluate pro and active MMP 2 and 9 concentrations in tumor, normal stromal tissue, and serum from tumor-bearing cats. We hypothesized that serum concentrations of pro and active forms of MMPs 2 and 9 would be predictive of MMP concentrations in tumor tissue and that these MMP concentrations would correlate with the histopathologic grade of the malignancies. Pro and active forms of MMPs 2 and 9 were determined by gelatin zymography and subsequent computerized densitometry from tumor and nearby stromal tissue and serum from 49 cats with various malignancies. The serum concentrations of MMPs from these tumor-bearing cats were compared with serum concentrations of MMPs from 44 normal cats of similar age and gender. Measurable concentrations of MMPs 2 and 9 were found within tumor, stromal, and serum samples. Mean concentrations of total pro and active MMPs 2 and 9 within tumor tissue were significantly higher (P values <.0001, .0031, <.001, and .0064, respectively) when compared with stromal tissue from the same animals. Serum MMP concentrations from tumor-bearing cats were higher than those from normal cats. Poor correlation was found between serum MMP concentrations and tissue MMP concentrations of increasing histologic grades of malignancies. 相似文献
30.
Ajwa HA Trout T Mueller J Wilhelm S Nelson SD Soppe R Shatley D 《Phytopathology》2002,92(12):1349-1355
ABSTRACT Strawberry fields in California (9,500 ha annually) are pre-plant fumigated with methyl bromide and chloropicrin to prevent serious soil pest and disease problems. Although soil fumigation with methyl bromide has ensured stability of strawberry production, its use is being discontinued because of its effect on stratospheric ozone. The likely short-term alternatives such as 1,3-dichloropropene, chloropicrin, and metham sodium, although not ozone depleters, are potentially hazardous to the environment and humans if applied improperly. Water-soluble formulations of alternative fumigants can be applied through drip irrigation systems established to irrigate crops. In comparison to conventional shank methods of injection, application of soluble formulations through drip irrigation systems would be economical and environmentally friendly, reduce worker exposure, and allow for simultaneous or sequential application of a combination of fumigants. This paper discusses techniques developed to apply alternative fumigants through drip irrigation systems, and reviews ongoing studies to determine optimum application rates, soil conditions, plastic mulches, and amount of irrigation water used to apply these alternative fumigants. 相似文献