全文获取类型
收费全文 | 6144篇 |
免费 | 263篇 |
国内免费 | 1篇 |
专业分类
林业 | 451篇 |
农学 | 140篇 |
基础科学 | 49篇 |
1037篇 | |
综合类 | 1146篇 |
农作物 | 351篇 |
水产渔业 | 383篇 |
畜牧兽医 | 2150篇 |
园艺 | 231篇 |
植物保护 | 470篇 |
出版年
2023年 | 34篇 |
2022年 | 42篇 |
2021年 | 118篇 |
2020年 | 118篇 |
2019年 | 127篇 |
2018年 | 112篇 |
2017年 | 94篇 |
2016年 | 121篇 |
2015年 | 110篇 |
2014年 | 143篇 |
2013年 | 266篇 |
2012年 | 327篇 |
2011年 | 392篇 |
2010年 | 210篇 |
2009年 | 176篇 |
2008年 | 403篇 |
2007年 | 395篇 |
2006年 | 397篇 |
2005年 | 403篇 |
2004年 | 414篇 |
2003年 | 401篇 |
2002年 | 362篇 |
2001年 | 78篇 |
2000年 | 60篇 |
1999年 | 67篇 |
1998年 | 49篇 |
1997年 | 39篇 |
1996年 | 68篇 |
1995年 | 53篇 |
1994年 | 48篇 |
1993年 | 50篇 |
1992年 | 52篇 |
1991年 | 32篇 |
1990年 | 49篇 |
1989年 | 42篇 |
1988年 | 33篇 |
1987年 | 34篇 |
1986年 | 29篇 |
1985年 | 42篇 |
1984年 | 43篇 |
1983年 | 39篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1977年 | 29篇 |
1976年 | 20篇 |
1975年 | 22篇 |
1974年 | 25篇 |
排序方式: 共有6408条查询结果,搜索用时 15 毫秒
1.
George J. Brewer MD William Schall DVM Robert Dick BS Vilma Yuzbasiyan-Gurkan PhD Michael Thomas DVM George Padgett DVM 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(1):41-43
Inherited canine copper toxicosis is a serious problem in Bedlington terriers and West Highland White terriers, and may also be a problem in other less-studied breeds. Affected dogs become ill at midlife with progressive and ultimately fatal liver disease. Treatments for removal of copper and prevention of copper accumulation are available, but are most effective if begun before the dog becomes ill. Until recently diagnosis has not been available until the dog is 1 year of age, and then only by an invasive liver biopsy with determination of liver copper concentration. The authors studied the use of 64copper for early diagnosis of canine copper toxicosis. Two procedures were evaluated. The first involved measuring the concentration of 64copper in blood 24 hours after oral administration of the radioisotope. At this time, 64copper was associated primarily with ceruloplasmin secreted into the blood by the liver. This procedure is useful in the diagnosis of the human counterpart, Wilson's disease. However, the authors found it to be nondiscriminatory between affected and unaffected dogs. In contrast, the second procedure, which involved measuring 64copper excreted in stool during 48 hours after an intravenous dose of radioisotope, yielded results that differentiated most affected and unaffected dogs. 相似文献
2.
3.
Edwin H. Robinson JamesA. Steeby J. Robert Brent 《Journal of the World Aquaculture Society》1989,20(4):256-260
Two 7 day feeding trials were conducted with channel catfish swim-up fry to evaluate growth, feed conversion ratio, and body composition of fish fed one of the following feeds: salmon starter, catfish starter, or trout starter. Fish fed the salmon or trout starter feeds gained 50–75% more weight, converted feed more efficiently, and had higher body fat stores than fish fed the catfish starter feed. This may be related to the higher protein and energy content of these two feeds. It may be advantageous to feed salmonid starter feeds to hatchery reared catfish fry; however, it is not known whether or not the improved performance observed in the hatchery continues once the fish are stocked into nursery and grow out ponds. 相似文献
4.
5.
Benny J. Woody DVM MS Michael J. Murphy DVM PhD AIlen C. Ray PhD Robert A. Green DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(1):23-28
The clinical signs and laboratory changes of brodifacoum (BDF) intoxicated dogs and their response to vitamin K1 treatment were examined. Brodifacoum, a second-generation anticoagulant rodenticide, was fed to four dogs for 3 consecutive days producing a cumulative dose of 1.1 mg BDF/kg body weight. Clinical observations of the animals were made daily throughout the study. Monitored laboratory parameters included: one-stage prothrombin time (OSPT), activated partial thromboplastin time (APTT), activated coagulation time (ACT), complete blood counts, thrombocyte counts, and serum chemistry values. Response to vitamin K1 therapy was evaluated clinically and by laboratory tests. Serum BDF concentrations were monitored. Inappetence and hemorrhagic tendencies were exhibited by day 5 postrodenticide exposure. One-stage prothrombin time, APTT, and ACT were 25% greater than time zero values at 24, 24, and 72 hours postdosing, respectively. All laboratory parameters returned to normal within 48 hours of initiating vitamin K1 therapy (0.83 mg/kg orally, TID for 5 days). Serum brodifacoum concentrations were highest (1065-1215 ng/mL) during the 3 days after BDF dosing and were detectable (3.0-7.5 ng/mL) until day 24 postexposure. A mean BDF elimination half-life of 6 +/- 4 days was observed. 相似文献
6.
Cytochrome P-450, A- and B-esterase, amidase, and glutathione S-aryl transferase were assayed in the postmitochondrial centrifugal fraction, microsomes, and supernatant of rat liver, lungs, kidneys, and testes. Liver microsomes contained the highest P-450 levels and A-esterase activity. B-esterase activity was more generally distributed and higher in the microsomal tissue fractions. Microsomal amidase activity was highest in rat lung and lowest in the liver (per mg protein). Glutathione S-aryl transferase activity was highest in the liver. The in vitro metabolism of carbaryl, phosphamidon, and chlorotoluron by the various centrifugal fractions revealed many differences. Carbaryl metabolism was greater in the liver microsomal fractions than in any other preparation. 1-Naphthol was the major metabolite in all tissue fractions. Although very little metabolism of phosphamidon occurred in the rat, metabolism in the rat liver postmitochondrial fraction was slightly higher with respect to the production of metabolites than in the supernatant and microsomes combined. Chlorotoluron was not metabolized by any of the tissue fractions of the rat. At least a low level of activity toward some compounds was observed in all tissues, but this study confirmed that the liver was the most active metabolizing tissue as well as having the highest levels of enzymatic activity usually associated with pesticide metabolism. 相似文献
7.
8.
9.
10.
One way to disperse waste from large commercial feedlots is to spread large amounts of the waste on limited areas nearby. The effects of this practice on the soil microbial populations was assessed. Feedlot waste (FLW) was applied for 5 yr at rates of 0, 22, 67, 134, and 269 t ha?1 yr?1. Additional treatments were 538 t ha?1 yr?1 for 1 and 3 years and applications of N and NPK fertilizer. Soil cores from plots were sampled for microbial analysis before, during, and after the fifth growing season. April, July. and December soil samples were analyzed to 180-, 20-, and 480-cm depths, respectively. The following utritional and physiological groups of microorganisms were counted: soil fungi on Rose Bengal agar; bacteria on a basal mineral salts medium, on nutrient agar (both aerobically and in BBL GasPak jars), and on EMB agar (Escherichia coli-type colonies and total counts); and nitrifying and denitrifying organisms. Little effect due to FLW application rates was found, and organisms producing coliform-type colonies on EMB agar did not persist in the soil. The results indicated that applying large amounts of feedlot waste will not deleteriously affect soil microorganisms. 相似文献