全文获取类型
收费全文 | 2016篇 |
免费 | 93篇 |
国内免费 | 402篇 |
专业分类
林业 | 128篇 |
农学 | 85篇 |
基础科学 | 617篇 |
387篇 | |
综合类 | 669篇 |
农作物 | 85篇 |
水产渔业 | 50篇 |
畜牧兽医 | 394篇 |
园艺 | 50篇 |
植物保护 | 46篇 |
出版年
2024年 | 10篇 |
2023年 | 20篇 |
2022年 | 30篇 |
2021年 | 50篇 |
2020年 | 60篇 |
2019年 | 65篇 |
2018年 | 42篇 |
2017年 | 82篇 |
2016年 | 95篇 |
2015年 | 79篇 |
2014年 | 135篇 |
2013年 | 138篇 |
2012年 | 196篇 |
2011年 | 174篇 |
2010年 | 134篇 |
2009年 | 145篇 |
2008年 | 126篇 |
2007年 | 144篇 |
2006年 | 129篇 |
2005年 | 106篇 |
2004年 | 104篇 |
2003年 | 86篇 |
2002年 | 69篇 |
2001年 | 40篇 |
2000年 | 31篇 |
1999年 | 34篇 |
1998年 | 22篇 |
1997年 | 33篇 |
1996年 | 27篇 |
1995年 | 26篇 |
1994年 | 17篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有2511条查询结果,搜索用时 15 毫秒
161.
Isotype-specific antibodies in horses and dogs with immune-mediated hemolytic anemia 总被引:1,自引:1,他引:0
Wilkerson MJ Davis E Shuman W Harkin K Cox J Rush B 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2000,14(2):190-196
Classes of antibody bound to erythrocytes were determined using direct immunofluorescence (DIF) flow cytometry in 3 horses and 12 dogs with immune-mediated hemolytic anemia (IMHA). Background levels of antibody binding were determined in samples from 12 horses and 12 dogs that were free of clinical disease. The range of nonspecific binding of a fluorescein isothiocyanate (FITC)-conjugated goat anti-equine immunoglobulin G (IgG) was 19.9–36.7%, but was eliminated by the use of the F(ab)2 fragment of FITC-conjugated goat anti-equine IgG. Background binding by other class-specific antibodies to equine and canine erythrocytes was negligible. The DIF results were compared to the direct antiglobulin (Coombs) test in 5 horses and 20 dogs with anemia. The former assay was more sensitive in dogs with IMHA than was the Coombs' test (100% versus 58%). In contrast, the Coombs' test had better specificity than the DIF assay (100% versus 87.5%, respectively). Using clinical parameters or response to therapy as the comparison, the positive and negative predictive values for the DIF test were 92% and 100% compared to the values of the Coombs' test of 100% and 62%. The DIF assay detected low levels of cells bound with antibody (<30%) in 5 dogs that were Coombs' test-negative. For both species, performance of the DIF test was independent of the prozone effect. Five dogs with IMHA had IgG and IgM on erythrocytes, 5 had IgG, and 2 had IgM. Three horses had surface-bound IgG, including a horse with suspected penicillin-induced IMHA, a foal with neonatal isoerythrolysis, and a foal with clostridial septicemia. The DIF method was valuable in monitoring the response to therapy in the foal with neonatal isoerythrolysis. 相似文献
162.
为了研究阿维菌素长效注射液(油悬剂)对绵羊痒螨疗效,将60只自然感染痒螨绵羊随机分为3组,每组20只。第1组每千克体重颈部皮下注射1 mg的阿维菌素油悬剂,第2组注射0.2 mg的阿维菌素普通注射液,第3组为不给药对照组。在给药后第7、14、21、28、35、42、49、56、63、70天对所有绵羊进行螨虫检查和计数,每天观察病变。结果表明:给自然感染痒螨的绵羊皮下注射1 mg/kg的阿维菌素长效注射液(油悬剂)可在给药后7 d内将痒螨完全杀灭,在给药后63 d内防止绵羊被痒螨再感染,其持效期远长于阿维菌素普通注射液(约为14 d)。 相似文献
163.
A complete diallel cross involving two rabbit sire lines (C and R) was carried out to estimate the crossbreeding genetic parameters of seminal traits. 2140 ejaculates from 153 males were analyzed. The traits studied were: presence of gel plugs (G), urine (U), and calcium carbonate deposits (CC), number of useful ejaculates (UE), pH, volume (V), mass and individual motility (Mm, Mi), useful Mi (UM), concentration (Cn), number of spermatozoa per ejaculate (TSE), percentage of viable spermatozoa (Vi), spermatozoa with normal apical ridge (NAR), normal spermatozoa (Nr), spermatozoa with morphological abnormalities of head (H), neck-midpiece (Nm), and tail (T), presence of proximal and distal cytoplasmic droplet (Dp, Dd).
Estimates of heterosis, direct and maternal genetic effects were obtained from the solutions of the mixed model. There were major differences in direct genetic effects between lines, which were favourable to line C for Cn and TSE, and unfavourable for CC, Nm and Dp. Smaller differences were also observed in Vi and NAR favourable to line R. Differences between lines with respect to the maternal genetic effects were relevant and favourable to line C for V and to line R for U, UM, Cn, TSE, Nm, Mi, and Mm. Individual heterosis was high for Dp and Dd. 相似文献
164.
《Scandinavian Journal of Forest Research》2012,27(6):651-660
A set of hypotheses was formulated on the basis of available knowledge about non-industrial private forest (NIPF) owners' risk preferences. The empirical material used for testing the hypotheses was gathered in telephone interviews with 130 randomly selected NIPF owners. The results confirm that direct economic risks such as price and cost changes are seen by this group as much more important than indirect economic risks such as biological damage. The forest owners regarded forest holdings as a safer investment than stocks or bank savings. The results on risk attitudes were ambiguous. However, when larger amounts of money were at stake, the forest owners could be considered risk averters and a decrease in absolute and relative risk aversion could be confirmed. 相似文献
165.
以喷油助燃再生方式为例,基于柴油机微粒捕集器(DPF)过滤体孔道热再生模型,对喷油助燃再生装置在不同工作参数下即喷油压力、喷油率、补气量等单因素变化时对再生过程过滤体排气背压、孔道内微粒层厚度及壁面峰值温度等变化规律进行了研究与分析.结果表明:燃烧器的工作参数喷油压力、喷油率、补气量等对再生过程有显著影响.随着喷油压力的提高,过滤体孔道再生壁面峰值温度升高,加快再生速率提高喷油率可加大燃烧器的功率,再生过程壁面峰值温度增幅较大,从过滤体的安全耐热温度来看应加以控制,但喷油率提高到一定程度后,使排气中氧含量不足,燃烧器燃烧效率下降,且影响微粒的氧化速度,导致再生速率随之下降.适当补气可增加排气中氧含量,可加快再生过程,但进一步加大补气量后由于对流传热散失作用加强将减缓再生过程. 相似文献
166.
根据近期发生的柴油着火爆炸事故,系统分析了柴油发生燃烧和爆炸的危险性,指出并分析了当前柴油存储方面存在的问题,提出了安全存储柴油的措施. 相似文献
167.
168.
169.
根据活塞环功能对材料的要求及活塞环的工作状况袁对合金铸铁、球墨铸铁、粉末冶金材料尧青铜、钢材等多种材料的性能特点进行分析,由此为活塞环材料的选择提供理论依据。 相似文献
170.