全文获取类型
收费全文 | 280337篇 |
免费 | 16026篇 |
国内免费 | 655篇 |
专业分类
林业 | 24250篇 |
农学 | 14179篇 |
基础科学 | 2977篇 |
45451篇 | |
综合类 | 27727篇 |
农作物 | 17595篇 |
水产渔业 | 17645篇 |
畜牧兽医 | 116047篇 |
园艺 | 6399篇 |
植物保护 | 24748篇 |
出版年
2021年 | 2536篇 |
2020年 | 2920篇 |
2019年 | 3702篇 |
2018年 | 4329篇 |
2017年 | 4702篇 |
2016年 | 4994篇 |
2015年 | 4438篇 |
2014年 | 5840篇 |
2013年 | 16403篇 |
2012年 | 7503篇 |
2011年 | 9602篇 |
2010年 | 7911篇 |
2009年 | 8391篇 |
2008年 | 8957篇 |
2007年 | 8170篇 |
2006年 | 8488篇 |
2005年 | 7696篇 |
2004年 | 7513篇 |
2003年 | 7374篇 |
2002年 | 6569篇 |
2001年 | 7507篇 |
2000年 | 7206篇 |
1999年 | 6455篇 |
1998年 | 4246篇 |
1997年 | 4294篇 |
1996年 | 4034篇 |
1995年 | 4598篇 |
1994年 | 4005篇 |
1993年 | 3687篇 |
1992年 | 4990篇 |
1991年 | 5220篇 |
1990年 | 5023篇 |
1989年 | 5025篇 |
1988年 | 4444篇 |
1987年 | 4478篇 |
1986年 | 4337篇 |
1985年 | 4520篇 |
1984年 | 4107篇 |
1983年 | 3818篇 |
1982年 | 3056篇 |
1981年 | 2910篇 |
1980年 | 2860篇 |
1979年 | 3487篇 |
1978年 | 3041篇 |
1977年 | 2812篇 |
1976年 | 2628篇 |
1975年 | 2502篇 |
1974年 | 2670篇 |
1973年 | 2752篇 |
1972年 | 2447篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
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
902.
J L Du Plessis C Gray M F Van Strijp 《The Onderstepoort journal of veterinary research》1992,59(4):337-338
A 3-fold increase in the numbers of Lyt-2+ T cells in the circulating blood of mice infected and re-infected with the Welgevonden stock of Cowdria ruminantium, as determined by flow cytometry, is supportive evidence that immunity in heartwater is cell-mediated. The rise in Lyt-2+ cells only after re-infection of the mice is further evidence that the development of immunity in heartwater is dependent on the unhindered and adequate replication of C. ruminantium. 相似文献
903.
R. Zabielski S. G. Pierzynowski 《Journal of animal physiology and animal nutrition》1992,68(3):146-150
Eine Methode zur langfristigen Lymphsammlung aus der jejunalen Lymphbahn bei Schweinen und Schafen Es wird eine Methode zur langfristigen Lymphsammlung im Dünndarmbereich von Schweinen und Schafen vorgestellt. Mit Hilfe eines chirurgischen Eingriffs wurde ein Silikon-Katheder im truncus lymphaticus jejunalis implantiert. Zusätzlich wurde ein zweiter Katheter in die hintere vena cava in Richtung Herz eingesetzt. Beide Katheter wurden sofort miteinander verbunden, um die Wiedereinführung der jejunalen Lymphe in den Blutkreislauf zu gewährleisten. Der negative Druck in der hinteren vena cava im Thoraxteil förderte den Lymphfluß durch das Katheter im truncus lymphaticus jejunalis. Der preprandiale Lymphfluß des Jéjunums betrug bei Schweinen 0,3 ml/h/kg Körpergewicht und stieg postprandial auf 0,78 ml/h/kg an. Beim Schaf betrug der Basiswert 0,75 ml/h/kg. Er stieg nach intraduodenaler Infusion von Rapsöl auf 4,75 ml/h/kg. Eine mechanische Stimulation der intestinalen Receptoren durch 0,9% NaCl-Lösung stimulierte ebenfalls den Lymphfluß. 相似文献
904.
J.P. Philipov 《Research in veterinary science》1992,53(3):303-398
The effect of ultraviolet irradiation on some biochemical indicators of bone turnover in dairy cows was determined. The irradiation was performed using a stationary system for two months and comprised a regimen of 10 days irradiation followed by 10 days rest. After ultraviolet irradiation, significant differences in the activities of serum alkaline phosphatase (P < 0.001) and bone alkaline phosphatase isoenzyme (P < 0.05) and concentration of osteocalcin (P < 0.01) were demonstrated. The results suggest that supplementary ultraviolet irradiation during winter could be used as a simple but reliable method of preventing the development of generalised metabolic bone disorders in dairy cows. 相似文献
905.
Rational perioperative management improves the success rate of abdominal surgery. Important aspects of management are discussed, including principles of fluid therapy, nutrition, intravenous catheterization, antimicrobial prophylaxis, and the use of nonsteroidal anti-inflammatory medication. Current advances in the area of immunotherapy are mentioned. 相似文献
906.
907.
The incidence and severity of foliar anthracnose, caused by Colletotrichum gloeosporioides , were recorded for seven fields of yams ( Dioscorea alata var. White Lisbon) in Barbados over a complete growing season. A scoring system was developed to estimate severity, placing the emphasis on the earliest, least visible stages of the disease. Disease progress curves were described in terms of the logistic model and the effects of site and leaf age on the parameters as well as on disease at tuber bulking were analysed. Differences between sites indicated that disease was more severe in areas of higher rainfall. In severe epidemics, disease predominated on young leaves. Fungicides applied sufficiently early can delay the onset of disease and slow the rate of disease progress. 相似文献
908.
L H Southwick D J Wilson P M Sears 《Journal of the American Veterinary Medical Association》1992,201(3):441-444
A dairy farm located in central New York was visited because of complaints of electrical shock in the farmhouse shower and the milk house sink. As much as 2 volts AC of potential difference was measured between the waterline and the cow platform (cow-contact voltage). Voltage was coming from the primary neutral wire. The farm's electrical service was modified so that the farmstead could be connected or disconnected from the primary neutral wire at 2-week intervals for 12 weeks. When connected to the primary neutral wire, voltage between waterline and floor ranged between 0 and 1.8 volts, producing estimated current flow through cows of 3.6 to 4.9 mA; when disconnected from primary neutral wire, voltage between waterline and floor was less than 0.1 volt. There was no difference in mean milk production, bulk tank milk somatic cell count, or water consumption among periods when cows were exposed or unexposed to voltage. Despite statistical nonsignificance, the values for somatic cell count were lower and water consumption was higher when cows were exposed to voltage than when they were not. 相似文献
909.
910.
Summary Cattle feed sources were studied at village level in Pabna district, Bangladesh. A large quantity of feed was offered. In
the monsoon the average amount of DM fed to a mature animal of 210kg was 7·1kg d−1, consisting of about equal amounts of straw, weeds and leaves. In winter animals grazed for an average of 3·7hd−1 and were supplemented with 3·9kgDMd−1 (two-thirds straw). In summer they were offered 5·4kgDMd−1 (one-third straw and two-thirds weeds and leaves) and they grazed for 0·5hd−1. The major limiting constraint on cattle production is the quality of the feed offered, particularly in the monsoon period
when animals cannot graze. In future, feed quality will become even more of a problem because grazing lands are gradually
disappearing.
Resumen Se estudiaron las fuentes de alimentos para el ganado a nivel de villorrio en el distrito de Pabna, Bangladesh. Se ofreció gran cantidad de alimento. En la época de monsones, la cantidad promedio de materia seca (MS) suministrada a un animal maduro de 210kg fue 7·1kgd−1, la que consistió en cantidades iguales de paja, malezas y hojas. En invierno los animales pastorearon un promedio de 3·7hd−1 y fueron suplementados con 3·9kgMSd−1 (dos tercios paja). En verano se ofrecieron 5·4kgMSd−1 (un tercio paja y dos tercios malezas y hojas), pastoreando los animales 0·5hd−1. La mayor limitante encontrada, fue la calidad del alimento ofrecido, particularmente en la época de monsones, cuando los animales no pueden pastorear. En el futuro, la calidad del alimento empeorará, ya que las pasturas están desapareciendo gradualmente.
Résumé Les disponibilités alimentaires du bétail ont été étudiées dans le district de Pabna (Bangladesh), au sein d'un village. Une grande quantité de nourriture fut offerte. Lors de la mousson, la quantité moyenne de matière sèche présentée à un adulte de 210kg était de 7,1kg/j, consistant en proportion à peu près équivalente de paille, mauvaises herbes et feuilles. En hiver, les animaux paturaient en moyenne 3,7kg/j et recevaient un supplément de 3,9kg/j de matières sèchs (deux tiers de paille). En été, on leur a distribué 5,4kg/j de matières sèches (un tiers de pailles, deux tiers de mauvaises herbes et de feuilles) et ils paturaient pendant une demi-heure (0,5h/j). Le facteur majeur limitant réside dans la qualité nutritive offerte, particulièrement pendant la mousson, période où les animaux ne peuvent pas paturer. La qualité de l'alimentation risque de devenir encore plus problématique du fait de la disparition progressive des paturages.相似文献