全文获取类型
收费全文 | 202篇 |
免费 | 9篇 |
国内免费 | 11篇 |
专业分类
林业 | 9篇 |
农学 | 7篇 |
基础科学 | 8篇 |
39篇 | |
综合类 | 70篇 |
农作物 | 7篇 |
水产渔业 | 46篇 |
畜牧兽医 | 14篇 |
园艺 | 20篇 |
植物保护 | 2篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 30篇 |
2012年 | 16篇 |
2011年 | 19篇 |
2010年 | 14篇 |
2009年 | 19篇 |
2008年 | 14篇 |
2007年 | 16篇 |
2006年 | 18篇 |
2005年 | 8篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有222条查询结果,搜索用时 15 毫秒
1.
Chloride channels distribute widely in the body, and participate in many physiological actions and regulatory processes. Based on their physiological roles and molecular structures, six kinds of chloride channels have been identified: (1) The chloride channels family; (2) Cystic fibrosis transmembrane conductance regulator; (3) Swelling-activated chloride channels; (4) Calcium-activated chloride channels; (5) The p64 (CLIC) gene family; (6) γ-aminobutyric acid and glycine receptors. The chloride channels do exist in platelets, and their appearances are dependent on the presence of intracellular calcium. Blocking agents of chloride channels inhibit the thrombin-activated platelet aggregation and the elevation of the intracellular calcium concentration in a dose-dependent manner. It is suggested that chloride channels play a role in the activation of platelets. In addition, chloride channels act on both the cell volume regulation and the intracellular pH regulation in platelets. 相似文献
2.
2018年8月开始,非洲猪瘟在我国快速多点发生,该病是高度接触性传染性疾病,目前无有效的疫苗和药物控制,各大公司和养殖户开始了猪场生物安全体系的升级改造。两年后我国大部分猪场的成功复产,全国生猪出栏量的大幅提升,证明了生物安全措施巨大效力;同时在严格的生物安全措施下创新了精准剔除、快速复产等操作,进一步证明了生物安全措施的有效作用。文章主要介绍猪场生物安全体系中入口(大门)和出口(后门)最为关键防线处的通道设计,方便所有的生物安全操作能够高效落实,切断病原轻易进出猪场的途径。 相似文献
3.
Steven G. Hall James Finney R. Paul Lang Terrence R. Tiersch 《Aquacultural Engineering》2002,26(4):277-289
A control system was designed to raise and maintain water temperatures within 0.03-ha earthen ponds to a range conducive for spawning (24–30 °C) channel catfish Ictalurus punctatus. Heating was done during February 2001 to April 2001, when temperatures would have otherwise prohibited spawning (<24 °C). Temperature was increased from 10 °C (ambient) by 2 °C per day, and maintained at 27 °C, by the addition of geothermally warmed water (36 °C). The control system substantially increased the controllability and precision of heating ponds compared to manual operation. Systems were designed to control sets of four ponds. In designing this control system, consideration of biological constraints was essential. Reproduction in channel catfish is most strongly influenced by temperature. Because cold fronts are common during the winter and early spring (January–March), it was essential to ensure that pond temperatures did not fall below the range for spawning. Constraints on the heating rate and temperature variability to maintain fish health and stimulate spawning behavior were considered. Components of the control system included temperature measurement devices (type-T thermocouples), a central electronic control unit, electronic switches and electrically actuated ball valves. In response to the temperature sensed by each thermocouple, the controller sent a message to close or open the valve. When the valve was opened, warm water was added to the pond to increase the average pond temperature. Hardware and algorithm design and initial system testing were the major components of this project. The final design incorporated information on relevant biological parameters and safety features including peak pond temperature, independent aeration and water pressure control mechanisms. Initial results indicate successful control of this biological system, and ongoing studies suggest similar mechanisms may be used for additional control objectives. In particular, this system could be used to vary pond temperatures to study biological responses and to cool ponds by addition of well water during summer months. 相似文献
4.
非饱和土壤水分扩散率是研究土壤水分运动规律必不可少的基本参数之一。本文应用水平土柱入渗法测定了科尔沁沙地沙质农田表层土壤的非饱和水分扩散率,并对氯化钴试纸在测定水分扩散率中的应用作了初步尝试和研究。主要结论如下:沙质农田表层土壤湿润锋迁移速率随着入渗距离的增大而减小,呈幂函数关系;波尔兹曼参数与土壤含水量呈直线关系;土壤水分扩散率与土壤含水量之间的关系,符合经验公式并呈指数函数变化。在应用水平土柱法测定非饱和土壤水分扩散率的过程中,氯化钴试纸法可以用于测定湿润锋的位置,特别是在高土壤含水量时,相比目视法而言更能显示其优势,在一定程度上可以提高测定结果的可靠性。 相似文献
5.
氯化胆碱对干旱胁迫下玉米幼苗叶片膜结构保护机制的研究 总被引:11,自引:1,他引:11
用300 m g/L氯化胆碱(CC)浸种与叶面喷施相结合作预处理,然后用15% PEG- 6000 模拟干旱胁迫。发现CC在干旱条件下可减缓CAT、POD活力和类胡罗卜素含量的降低, 特别是改变了SOD活力在干旱胁迫下通常呈波浪式变化的规律, 使其在实验条件下一直呈上升趋势。这些可能是膜结构得到保护, 从而使膜脂过氧化产物MDA 产生及细胞电解质渗漏都明显减少的主要原因。 相似文献
6.
7.
《Journal Of Applied Aquaculture》2013,25(1-2):95-103
Abstract The passive sock grading method used by commercial channel catfish, Ictalurus punctatus, farmers to grade and reduce the number of under-sized fish delivered to processing plants was assessed on an experimental scale. The assessment was conducted at the Aquaculture Research Station at the University of Arkansas, Pine Bluff in 0.1-ha earthen ponds. A rectangular holding sock was fabricated with dimensions of 0.9 m in width, 2.4 m in length, and 1.2 m in depth. The mesh size of the sock was 4.4 cm and the mesh material was nylon netting, 0.64 cm in diameter. Seventeen groups of channel catfish, were graded, with group weights ranging from approximately 115 to 370 kilograms. Fish were held in the sock for approximately three hours (±0.27 hours). The water temperature during the trials ranged from 7.3°C to 28.7°C. The percent removal of fish less than 0.45 kg during the three-hour holding period ranged from 27.6% to 73.3%. Overall, sock grading efficiency increased with increasing water temperature and at water temperatures above 15°C a greater percentage of fish less than 0.45 kg were not retained in the socks. 相似文献
8.
9.
外源氯对番茄幼苗生长及养分吸收、利用的影响 总被引:6,自引:0,他引:6
研究了不同水平外源氯处理对番茄(Lycopersicon esculentum L. ) 干物质积累、叶绿素含量、Cl- 、NO3- 、氮、磷、钾、钙和镁含量的影响。结果表明: 一定范围( 6.25~100 nmol·L - 1 ) 的外源氯处理, 不降低番茄生物量甚至促进生物量, 并可明显提高番茄幼苗对钾、镁、磷的吸收和氮素利用效率, 而200、300 mmol·L - 1 Cl- 处理的幼苗干物质积累极显著下降。 相似文献
10.
渠道是农田水利建设的一个重要工程,渠道测量在渠道兴、改、扩建中具有重要的地位和作用。仅就施工过程中如何快捷恢复渠道中线的测量方法作了探讨,并对恢复中线的精度作了相应分析。 相似文献