首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2616篇
  免费   307篇
  国内免费   155篇
林业   29篇
农学   56篇
基础科学   6篇
  27篇
综合类   828篇
农作物   31篇
水产渔业   285篇
畜牧兽医   1765篇
园艺   40篇
植物保护   11篇
  2024年   2篇
  2023年   38篇
  2022年   48篇
  2021年   108篇
  2020年   123篇
  2019年   169篇
  2018年   83篇
  2017年   143篇
  2016年   162篇
  2015年   120篇
  2014年   130篇
  2013年   133篇
  2012年   164篇
  2011年   201篇
  2010年   137篇
  2009年   151篇
  2008年   103篇
  2007年   128篇
  2006年   114篇
  2005年   102篇
  2004年   110篇
  2003年   70篇
  2002年   50篇
  2001年   52篇
  2000年   48篇
  1999年   33篇
  1998年   46篇
  1997年   34篇
  1996年   21篇
  1995年   36篇
  1994年   38篇
  1993年   21篇
  1992年   19篇
  1991年   23篇
  1990年   21篇
  1989年   31篇
  1988年   10篇
  1987年   9篇
  1986年   6篇
  1985年   3篇
  1984年   5篇
  1982年   4篇
  1980年   7篇
  1979年   5篇
  1978年   2篇
  1977年   2篇
  1975年   2篇
  1974年   3篇
  1973年   4篇
  1956年   2篇
排序方式: 共有3078条查询结果,搜索用时 109 毫秒
991.
The disposition kinetics and urinary excretion of gentamicin sulphate were studied in young buffalo bulls following a single intramuscular administration of the drug at 5 mg kg-1 body weight. The time course of the serum gentamicin concentration was adequately described by the one-compartment open model. The values of the absorption and elimination halflives were 12.2±2.2 and 167.0±29.7 min respectively. The apparent volume of distribution was 0.29±0.01 L kg-1. During the first 12 h, 63% of the total administered dose was excreted in urine. On the basis of the kinetic data, a satisfactory intramuscular dosage regimen for gentamicin sulphate would be at least 6 mg kg-1 body weight repeated at 8 h intervals.  相似文献   
992.
The levels of antimony, arsenic, cadmium, copper, lead, mercury, molybdenum, selenium and zinc were determined in liver of moose, reindeer and red deer from differen localities in Norway. Reindeer had considerably higher levels of mercury, lead and arsenic than moose and red deer. These findings are considered to be related to differences in feeding habits since reindeer on highland plateaus feed mainly on lichens which have been shown to accumulate trace elements. The levels of arsenic, and to some extent also selenium and cadmium, in moose and reindeer liver showed a north-south gradient closely related to the regional distribution of these elements in the forest moss. As regards lead, a north-south gradient and a relationship to moss levels, were found in moose liver only. It therefore seems that atmospheric deposition of the elements mercury, lead, arsenic, cadmium and selenium contribute to the body burden of these elements in cervides in Norway. There was no evidence of these elements accumulating to toxic levels.  相似文献   
993.
应用ND来活苗与弱毒苗联合及单独弱毒苗对1日龄火鸡进行早期免疫,于第60日进行ND强毒攻击。分别在第7、14、21、35和日龄检测外周血液的免疫学变化。结果表明,1日龄火鸡疫苗接种后其外周血液中T细胞、B淋巴细胞和淋巴细胞数量、血清IgG,IgM,IgA含量及HI抗体滴度均明显升高,可获得良好的免疫保护效应,其中活苗与死苗联合免疫组优于单独活苗免疫组。  相似文献   
994.
通过对11匹实验马的血气、酸碱值分析,结果表明以12g/100kg体重的水合氯醛麻醉后,实验马的Po2、Sat·O2、C-O2三项指标均显著降低,PA-aDO2显著增加;而pH、Pco2、T-CO2、AB、SB、BEb六项指标无显著变化。说明该剂量的水合氯醛对马的呼吸功能有一定影响,且主要影响与氧有关的指标。  相似文献   
995.
Jensen, A. L., A. B. Olesen and J. Arnbjerg: Distribution of feline blood types detected in the Copenhagen area of Denmark. Acta vet. scand., 1994, 35, 121-124.–The purpose of the present study was to make the first survey of the distribution of feline AB blood types in the Copenhagen area of Denmark. A total of 244 cats (139 purebred cats and 105 Domestic Shorthair cats) were tested. 93% of all tested cats had blood type A. Neither an AB nor an O type cat was detected and thus, the frequency of blood type B among all tested cats was 7%. Most type B cats were purebred cats (Birman, British Shorthair and Persian cats). No association between sex and blood type could be demonstrated among British Shorthair and Persian cats. Thus, the present study indicates that cats in Denmark predominantly have blood type A, and that blood type B cats are rare, except for certain breeds such as Birman and British Shorthair cats.  相似文献   
996.
The heart and liver functions, blood electrolytes and acid-base balance were studies in halothane-sensitive and nonsensitive pigs. An inhibition of the hyperthermia reaction was attempted by an i.v. injection of propranolol. The pulse rate of sensitive pigs was shown to be elevated already at the beginning of halothane narcosis. No other differences between sensitive and nonsensitive pigs were observed from the electrocardiogram. Ectopic beats and arythmia appeared only in 1 halothane-sensitive pig which died soon after the test. The serum OCT-activity showed no abnormalities. Hyperkalemia and acidosis occurred but the Ga++ was not elevated in halothane-sensitive animals. The slight elevation in Na+ was thought to be caused by hemoconcentration. A propranolol injection only delayed but did not inhibit the halothane reaction.  相似文献   
997.
cDNAs encoding four different canine immunoglobulin G (caIgG) γ chains were identified in this study. One of these IgG γ chain cDNAs, (caIgG-A), represents 92.5% of the IgG γ chain cDNAs in a dog spleen cell cDNA library; a second partial IgG γ chain cDNA (caIgG-B) was also identified in the library. The other two IgG γ chain cDNAs (caIgG-C and caIgG-D) were RT-PCR amplified from canine lymphoma samples. Comparison of the four different canine IgG γ chain cDNAs showed homologies from 83.6 to 89.2% and from 73.1 to 81.8% at nucleotide and amino acid sequence levels, respectively. Despite the high similarity in CH1, CH2 and CH3 domains among the different caIgG γ chains, the hinge regions were distinct, sharing only 19.0–35.2% homology at the amino acid level. No multiple duplication of the hinge region, as reported for human IgG1 and IgG3, was detected in any of the canine IgG γ chains. The numbers of cysteines in the putative hinge regions were found to be 3, 2, 7 and 3 for the four canine IgG heavy γ chains (A, B, C and D), respectively. Specific primers were designed based on caIgG γ chain hinge region DNA sequences and were used in RT-PCR for measuring different caIgG γ chain mRNA levels in canine PBMC samples.  相似文献   
998.
The normal flow velocity profile and duplex Doppler waveform of the major abdominal blood vessels (aorta, caudal vena cava and the portal vein as well as their major branches) were examined by Doppler ultrasound. The flow velocity profile of an artery is largely determined by its diameter. The pulsatility of the waveform is related to the vascular impedance downstream to the point of measurement. Early systolic peak is present in the Doppler pattern of some vessels in some dogs. The waveform of the veins is mainly affected by the pressure conditions of the right atrium and the intrathoracic and intraabdominal pressure changes due to the respiration. Simultaneous electrocardiogram was used to reveal the effect of the heart beats on the Doppler patterns of the veins.  相似文献   
999.
应用门电路心血池显象的勾边轮廓法及相位分析中的振幅图和心室相角程标准差观察38例病毒性心肌炎患者(急性期20例、后遗症期18例)和10例正常人。结果:勾边轮廓法显示左舒缩功能紊乱占92.1%,其中73.7%同时显示局部收缩下降;振幅图显示灰阶不均匀、局部灰度下降占76.3%;左室相角程标准差增宽占60.5%,其参数为10.23±2.93,与正常对照组比较有极显著差异(P<0.01)。对本文结果分析,认为上述门电路心血池显象三种检查,在病毒性心肌炎(包括急性期和后遗症期)诊断中,能较好地反映心肌损害的程度和心功能状态。  相似文献   
1000.
不同硒水平对生长育肥猪血液生化指标的影响   总被引:5,自引:1,他引:4  
试验研究了宁夏常用饲料中不同硒水平对生长育肥猪血液生化指标的影响。结果表明 :(1 )谷胱甘肽过氧化物酶 (GSH PX)活性随饲粮硒水平的增加 ,呈现下降 上升 下降的动态变化趋势。谷胱甘肽硫转移酶可反映缺硒的程度。 (2 )缺硒组仔猪血硒含量和全血中GSH PX均处于缺硒边缘状态 ,在临界值以下 ,不能满足仔猪的代谢需要。 (3)随饲粮硒水平的逐渐增加 ,猪瘟的抗体水平和淋巴细胞转化率明显升高 ,以饲粮中添加硒 0 45mg/kg时达到最高 ,仔猪发病率最低  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号