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   3772篇
  免费   414篇
林业   39篇
农学   17篇
基础科学   1篇
  60篇
综合类   103篇
农作物   31篇
水产渔业   28篇
畜牧兽医   3853篇
园艺   16篇
植物保护   38篇
  2023年   47篇
  2022年   8篇
  2021年   7篇
  2020年   134篇
  2019年   13篇
  2018年   99篇
  2017年   101篇
  2016年   57篇
  2015年   114篇
  2014年   161篇
  2013年   177篇
  2012年   150篇
  2011年   144篇
  2010年   144篇
  2009年   224篇
  2008年   127篇
  2007年   96篇
  2006年   101篇
  2005年   78篇
  2004年   116篇
  2003年   95篇
  2002年   143篇
  2001年   116篇
  2000年   76篇
  1999年   90篇
  1998年   107篇
  1997年   84篇
  1996年   86篇
  1995年   96篇
  1994年   68篇
  1993年   109篇
  1992年   125篇
  1991年   125篇
  1990年   121篇
  1989年   80篇
  1988年   98篇
  1987年   84篇
  1986年   77篇
  1985年   60篇
  1984年   48篇
  1983年   51篇
  1982年   25篇
  1981年   11篇
  1980年   10篇
  1978年   7篇
  1977年   7篇
  1973年   9篇
  1971年   10篇
  1970年   6篇
  1967年   6篇
排序方式: 共有4186条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
996.
997.
In bright beers, the formation of haze is a serious quality problem, which places limitations on the storage life of the product. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) immunoblot analysis using an antiserum that was raised against a silica eluate (SE) protein fraction (obtained from silica gel, used for the colloidal stabilisation of beer), detected a range of protein bands in barley, malt, beer and haze. A polymorphism was observed in which some barley varieties contained a molecular weight (MW) 12,000 band (SE +ve) while in other varieties this band was absent (SE −ve). A survey of 219 Australian and international barley varieties, including a comprehensive selection of current and past malting varieties, identified 181 varieties as SE +ve, and 38 varieties as SE −ve. Previous pilot brewing trials demonstrated that SE −ve varieties are desirable as the beer brewed from the malt of these varieties formed less haze after accelerated ageing than beers brewed using SE +ve malt varieties. The genetic basis for the absence of the SE protein was conferred by a recessive allele at a single locus. Interval mapping analysis showed that the MW 12,000 band mapped to the short arm of chromosome 3H.  相似文献   
998.
BACKGROUND: Lactoferrin is a colostral glycoprotein with antimicrobial properties. HYPOTHESES: (1) Serum lactoferrin and immunoglobulin G (IgG) concentrations are correlated and increase in healthy foals after ingestion of colostrum; (2) compared to healthy foals, ill foals will have lower lactoferrin concentrations that correlate with their IgG concentration, neutrophil count, the diagnosis of sepsis, and survival; and (3) plasma concentrations of lactoferrin will be less than serum concentrations. ANIMALS: Healthy foals (n = 16), mature horses (n = 10), and ill foals 1-4 days old (n = 111) that were examined for suspected sepsis were used for blood collection. Colostrum was obtained from 10 healthy mares unrelated to the foals. METHODS: Blood was obtained from the healthy foals at birth and 1-3 days of age and from the ill foals at admission. Serum IgG was quantified by single radial immunodiffusion (SRID). Lactoferrin concentrations in colostrum and blood were determined by an enzyme-linked immunosorbant assay. The sepsis score, blood culture results, neutrophil counts, and survival were obtained on ill foals. RESULTS: The mean colostral lactoferrin concentration was 21.7 microg/mL. Compared to values at birth, serum IgG (18+/-2 versus 2,921+/-245 mg/dL, SEM) and lactoferrin (249+/-39 versus 445+/-63 ng/mL, SEM) concentrations were significantly greater in healthy foals 1-3 days old. Serum lactoferrin concentration in 1-3-day-old healthy foals was not different from mature horses or ill foals. IgG and lactoferrin concentrations were significantly correlated only in healthy foals. Serum lactoferrin concentrations were significantly lower in ill neutropenic foals. The serum IgG concentration was significantly lower in ill foals as compared to healthy foals. Only serum IgG was significantly less in ill foals with a positive sepsis score and in nonsurvivors, Plasma lactoferrin concentrations were lower than serum concentrations, although values were significantly correlated. CLINICAL IMPORTANCE: Although both serum IgG and lactoferrin concentrations increase in healthy foals after ingestion of colostrum, only serum IgG is significantly correlated with the sepsis score and outcome.  相似文献   
999.
Birth in all higher vertebrates is at the center of the critical window of development in which newborns transition from dependence on innate immunity to dependence on their own adaptive immunity, with passive maternal immunity bridging this transition. Therefore we have studied immunological development through fetal and early neonatal life. In swine, B cells appear earlier in fetal development than T cells. B cell development begins in the yolk sac at the 20th day of gestation (DG20), progresses to fetal liver at DG30 and after DG45 continues in bone marrow. The first wave of developing T cells is gammadelta cells expressing a monomorphic Vdelta rearrangement. Thereafter, alphabeta T cells predominate and at birth, at least 19 TRBV subgroups are expressed, 17 of which appear highly homologous with those in humans. In contrast to the T cell repertoire and unlike humans and mice, the porcine pre-immune VH (IGHV-D-J) repertoire is highly restricted, depending primarily on CDR3 for diversity. The V-KAPPA (IGKV-J) repertoire and apparently also the V-LAMBDA (IGLV-J) repertoire, are also restricted. Diversification of the pre-immune B cell repertoire of swine and the ability to respond to both T-dependent and T-independent antigen depends on colonization of the gut after birth in which colonizing bacteria stimulate with Toll-like receptor ligands, especially bacterial DNA. This may explain the link between repertoire diversification and the anatomical location of primary lymphoid tissue like the ileal Peyers patches. Improper development of adaptive immunity can be caused by infectious agents like the porcine reproductive and respiratory syndrome virus that causes immune dysregulation resulting in immunological injury and autoimmunity.  相似文献   
1000.
Over the last ten years a fatal syndrome associated with immunodeficiency and severe anaemia has been reported in young Fell pony foals in the UK. Affected foals are usually normal at birth but from the age of 2-4 weeks they progressively lose condition and become severely anaemic. Signs of immunodeficiency become apparent at around 3-4 weeks of age. Morbidity is low but mortality is 100% despite intensive treatment. Affected foals die or are euthanized usually before they reach the age of 3 months. A single autosomal recessive gene is suggested to be on the basis of the syndrome. Recently, affected Fell pony foals have been identified in the Netherlands and between June 2003 and August 2005, six affected Fell pony foals were referred to the Faculty of Veterinary Medicine for investigation.  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