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   2534篇
  免费   210篇
  国内免费   131篇
林业   177篇
农学   173篇
基础科学   29篇
  116篇
综合类   757篇
农作物   130篇
水产渔业   144篇
畜牧兽医   800篇
园艺   474篇
植物保护   75篇
  2024年   4篇
  2023年   51篇
  2022年   72篇
  2021年   104篇
  2020年   123篇
  2019年   122篇
  2018年   85篇
  2017年   140篇
  2016年   153篇
  2015年   126篇
  2014年   162篇
  2013年   174篇
  2012年   190篇
  2011年   170篇
  2010年   125篇
  2009年   118篇
  2008年   142篇
  2007年   121篇
  2006年   77篇
  2005年   65篇
  2004年   54篇
  2003年   58篇
  2002年   65篇
  2001年   47篇
  2000年   51篇
  1999年   27篇
  1998年   20篇
  1997年   33篇
  1996年   21篇
  1995年   24篇
  1994年   23篇
  1993年   17篇
  1992年   21篇
  1991年   17篇
  1990年   19篇
  1989年   13篇
  1988年   7篇
  1987年   6篇
  1986年   7篇
  1985年   7篇
  1984年   4篇
  1981年   1篇
  1980年   3篇
  1975年   3篇
  1974年   2篇
  1973年   1篇
排序方式: 共有2875条查询结果,搜索用时 15 毫秒
1.
为了探讨添加红枣提取物对促进虹鳟(Oncorhynchus mykiss)机体健康的可能性,选取体长为7.2~8.4 cm的健康虹鳟,随机分成4个试验组,分别投喂红枣提取物添加量为0%(对照组)、0.25%、0.50%和1.00%的等氮等脂饲料,饲养56 d,养殖结束后测定12项血清生化指标和头肾的6个免疫相关基因mRNA表达量。结果显示:与对照组相比较,血清中肌酐(CREA)和尿素氮(BUN)含量三个红枣提取物组均出现极显著下降;谷丙转氨酶(GPT)活性在0.50%和1.00%组极显著下降,谷草转氨酶(GOT)活性也在0.50%和1.00%组出现了一定程度下降,但差异不显著;酸性磷酸酶(ACP)和碱性磷酸酶(AKP)活性无显著变化;总蛋白(TP)和白介素6(IL-6)含量在0.25%组出现显著增加;溶菌酶(LZM)活性三个红枣提取物组均显著升高;超氧化物歧化酶(SOD)活性在0.50%组极显著增加;补体4(C4)和肿瘤坏死因子(TNF-α)含量在0.25%和0.50%组均极显著增加。在头肾中,与对照组相比,SOD、白介素1β(IL-1β)和补体3(C3)基因表达量在0.50%和1.00%组均为显著或极显著上调;Factor H基因表达量在0.50%组显著上调;过氧化氢酶(CAT)和LZM基因表达量在0.50%和1.00%组仅出现差异不显著上调。上述结果表明,在虹鳟饲料中添加一定量的红枣提取物,可以起到促进肾功能,保护肝脏和提高其非特异性免疫功能的作用。  相似文献   
2.
3.
牛奶葡萄采后SO2双重释放装置辅以CT-1处理不但有效降低了药害发生率,而且提高了贮藏效果。在此基础上辅以采前喷布内含杀菌剂的壳多糖,牛奶葡萄可达到更佳贮藏效果,在1998年生长季发生全国性洪水灾害,田间带菌量剧增,各地葡萄贮藏效果极差情况下,参试的牛奶葡萄腐烂率只有1.6%,果梗鲜绿,褐变指数只有0.4%,药害率仅为1.0%,果肉亚硫酸盐残留仅为0.067 mg/kg。  相似文献   
4.
对蔚县苜蓿根颈冻害后切除冻伤部分处理的比较研究结果表明,处理区的根颈苗数、地上高度、地上生物量、分蘖丛数是对照区的1.6~2倍;处理区苜蓿的各个数量指标的b值大于对照处理苜蓿b值,说明除冻害根颈后苜蓿的生长比不除冻害根颈部分的苜蓿生长更为合理。通过除去苜蓿冻害部位,防止根系继续腐烂,保护了未冻害部分,增加了苜蓿发芽的有效部位。同时,使根系与地面的距离变短或露出地面,增加光照强度,提高地温,促使未冻害苜蓿根系发芽,返青提前增加产量。  相似文献   
5.
A six-year-old arabian stallion was admitted to The Ohio State University Veterinary Hospital for evaluation and repair of a comminuted fracture of the second phalanx. The horse developed impaired arterial oxygenation during surgey and pulmonary edema post-operatively. We postulate that impaired arterial oxygenation resulted from atelectasis of the dependent lung during annesthesia, and the pulmonary edema occurred following re-expansion of the atelectatic of the initiating cause of the edema, removal of excess lung water from the alveoli, and restoration of normal arterial oxygenation. The horse was fully recovered within 12 hours of initiation of clinical signs of respiratory compromise. The horse was fully recovered within 12 hours of initiation of clinical signs of respiratory compromise. This report describes re-expansion pulmonary edema due to reperfusion injury in a horse, treatment of the condition, and a possible explanation of the pathogenesis of this pulmonary pathology.  相似文献   
6.
Kano  R.  Kubota  A.  Nakamura  Y.  Watanabe  S.  Hasegawa  A. 《Veterinary research communications》2001,25(8):615-622
Using cDNA from a CRFK cell line as a template, PCR amplification was performed with the Ub1S and poly(dT) primers to isolate feline ubiquitin genes. Sequencing of the 495 bp PCR fragment revealed that the putative amino acids induced by this fragment gave a fusion protein consisting of a ubiquitin polypeptide (76 amino acids) and an extension protein of ribosomal proteins L40 (52 amino acids). The putative amino acid sequence of ubiquitin was identical to those of humans, rats and pigs.The recombinant glutathione S-transferase (GST)–feline ubiquitin fusion proteins were produced in Escherichia coli and purified. The fusion proteins had a molecular weight of about 42 kDa and were detected by immunoblot assay with rabbit anti-ubiquitin antiserum.The mRNAs from heat-shocked and non-heat-shocked cells were subjected to RT-PCR (Ub1S and poly(dT) primers) analysis. The molecular weights of the ubiquitinated proteins in heat-shocked CFRK cells were between 18 kDa and 24 kDa by immunoblot assay.These results suggested that there were more ubiquinated proteins in the heat-shocked CRFK cells than in the pre-heat-shocked cells.  相似文献   
7.
低氧适应动物喜马拉雅旱獭的组织学观察   总被引:2,自引:1,他引:1  
对生活在青藏高原(海拔3200-3400m)喜马拉雅旱獭的肝脏、肺、肾、卵巢、甲状腺等器官结构进行了组织学观察。  相似文献   
8.
橡胶树低温伤害的生理反应   总被引:4,自引:1,他引:3  
在人工零上低温下,巴西橡胶树(Hevea brasiliensis)叶质膜透性随低温处理时间的延长而持续上升,抗冷品系的上升速率比不抗冷品系慢。呼吸强度和ATP含量均随处理时间的延长而持续下降,抗冷品系下降速率比不抗冷品系慢。叶绿体Mg~(++)—ATPase活性也表现出明显抗性差异。可见,低温下叶组织的质膜透性、呼吸强度、ATP含量以及Mg~(++)—ATPase活性的变化与品系抗冷性有关。低温下呼吸强度、ATP含量与质膜透性变化呈负相关,质膜透性的变化与供能有关。  相似文献   
9.
AIM:To study influence of ischemia-reperfusion(IR) on apoptosis and expression of apoptosis-related genes Fas-L, Bax and Bcl-2 of sinoatrial node(SAN) cells in rabbits in vivo. METHODS:Ninety healthy adult rabbits were divided randomly into control group, ischemia groups (I10 min, I30 min, I60 min and I120 min) and IR groups (I10 minR4h, I30 minR4h, I60 minR4hand I120 minR4h). IR injury model of SAN was established by occluding and loosening the start section of right coronary artery. The apoptosis of SAN cells was detected by TUNEL staining. The expression of Fas-L, Bax and Bcl-2 of SAN cells was detected by immunohistochemistry. RESULTS:①No obvious apoptosis of SAN cells was observed in control group, I10 min and I30 min groups. Apoptosis of different degrees in SAN cells were found in 68.3%(41/60) rabbits in I60 min, I120 min and 4 subgroups of IR. ②The highest expression of Fas-L and Bax was observed in I120 min group and that of Bcl-2 was in I60 min group. ③The highest expression of Fas-L and Bax was observed in I60 minR4h group. The peak level of Bcl-2 was observed in I30 minR4h group. ④The expression of Fas-L and Bax was significant higher in IR group than that in ischemic group at the same time point. CONCLUSION:Ischemia and IR induced apoptosis of SAN cells in rabbit in vivo. Fas-L、Bax、Bcl-2 may participate in the regulation of apoptosis and the injury during IR aggravates the apoptosis of SAN cells.  相似文献   
10.
AIM:To study the relationship between myocardial HSP70 and PKC during myocardial ischemic preconditioning(IPC). METHODS: PKC inhibitor, polymyxin B(PMB) and PKC activator, phorbol 12-myristate 13-acetate(PMA) were applied to the models of myocardial ischemia/reperfusion in vivo and in vitro in rabbits, respectively, and the ventricular functions, PLA2 in the serum, and the expression of mycardial HSP70 mRNA were examined. RESULTS:IPC decreased PLA2 activity, improved the left ventricular function and increased the expression of myocardial HSP70 mRNA. Howerer, all these effects of IPC could be blocked by PMB. Interestingly, PMA mimicked IPC with attenuating the injuries of cardial myocytes and increasing myocardial HSP70 mRNA expression. CONCLUSION:PKC is involved in the myocardial HSP70 expression in case of ischemic preconditioning.  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