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   949篇
  免费   116篇
  国内免费   26篇
林业   31篇
农学   27篇
基础科学   1篇
  33篇
综合类   228篇
农作物   29篇
水产渔业   19篇
畜牧兽医   655篇
园艺   58篇
植物保护   10篇
  2024年   3篇
  2023年   17篇
  2022年   39篇
  2021年   36篇
  2020年   47篇
  2019年   59篇
  2018年   46篇
  2017年   61篇
  2016年   53篇
  2015年   39篇
  2014年   69篇
  2013年   49篇
  2012年   62篇
  2011年   69篇
  2010年   48篇
  2009年   43篇
  2008年   37篇
  2007年   52篇
  2006年   35篇
  2005年   27篇
  2004年   34篇
  2003年   21篇
  2002年   21篇
  2001年   17篇
  2000年   20篇
  1999年   12篇
  1998年   12篇
  1997年   7篇
  1996年   5篇
  1995年   8篇
  1994年   7篇
  1993年   6篇
  1992年   5篇
  1991年   3篇
  1990年   7篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   1篇
  1984年   2篇
  1982年   1篇
  1979年   1篇
  1978年   1篇
排序方式: 共有1091条查询结果,搜索用时 0 毫秒
61.
Objective – To evaluate the tolerance of a continuous positive airway pressure (CPAP) mask in tranquilized dogs and compare PaO2 in arterial blood in dogs receiving oxygen with a regular face mask or CPAP mask set to maintain a pressure of 2.5 or 5 cm H2O. Design – Prospective, randomized clinical study. Setting – University teaching hospital. Animals – Sixteen client‐owned dogs without evidence of cardiopulmonary disease were studied. Interventions – Eight animals were randomly assigned to each of 2 treatment groups: group A received 2.5 cm H2O CPAP and group B received 5 cm H2O CPAP after first receiving oxygen (5 L/min) by a regular face mask. Animals were tranquilized with acepromazine 0.05 mg/kg, IV and morphine 0.2 mg/kg, IM. An arterial catheter was then placed to facilitate blood sampling for pHa, PaO2, and PaCO2 determinations before and after treatments. Direct mean arterial pressure, heart rate, respiratory rate, and temperature were also recorded after each treatment. Measurements and Main Results – CPAP administration was well tolerated by all animals. The mean arterial pressure, heart rate, respiratory rate, temperature, PaCO2, and pHa, did not differ at any time point between groups. Differences were seen in oxygenation; in group A, PaO2 significantly increased from a mean of 288.3±47.5 mm Hg with a standard mask to a mean of 390.3±65.5 mm Hg with the CPAP mask and in group B, PaO2 increased similarly from 325.0±70.5 to 425.2±63.4 mm Hg (P<0.05); no differences were detected between the 2 CPAP treatments. Conclusions – In healthy tranquilized dogs noninvasive CPAP is well tolerated and increases PaO2 above values obtained when using a regular face mask.  相似文献   
62.
油-稻-稻三熟制下双季稻高产品种特征研究   总被引:1,自引:1,他引:1  
【目的】在早稻-晚稻-套播早熟油菜(油-稻-稻)三熟制下,筛选生育期适宜的高产水稻品种,系统研究早、晚稻高产品种特征,以期为油稻稻三熟制下水稻高产品种的选育与栽培提供理论参考。【方法】以9个早稻品种和10个晚稻品种为材料,通过系统聚类分析和方差分析等方法对油稻稻三熟制下双季稻高产品种特征进行研究。【结果】(1)与低产和中产类型双季稻相比,高产类型双季稻有效穗数、结实率、千粒重、生育期差异不显著,但每穗粒数、总颖花量、产量及日均产量显著高于低产类型。(2)高产类型与低产及中产类型双季稻的分蘖增长率、分蘖下降率及高峰苗数差异不显著,但成穗率显著高于低产类型,高产类型分蘖呈稳增缓降的发展态势。(3)早稻抽穗期干物质量及各生育时期平均单茎干物质量不同类型间无显著差异,结实期与全生育期干物质量随产量水平的提高呈增加趋势,高产类型显著高于低产类型;晚稻各生育时期干物质量及平均单茎干物质量不同类型间差异较大,高产类型均显著高于低产类型,但与中产类型差异不显著;各产量类型品种收获指数差异不显著。(4)随产量水平的提高,双季稻抽穗期和成熟期群体叶面积(LAI)和单茎叶面积呈增加趋势,灌浆结实期叶面积下降率则呈降低趋势,高产类型与低产类型均存在显著差异;粒叶比随产量水平的提高而增大,其中早稻高产类型与低产类型差异显著,而晚稻差异不明显。【结论】在油稻稻三熟制条件下,高产类型双季稻具有分蘖力中等、成穗率较高、全生育期特别是花后干物质生产量及单茎干物质量大、中后期LAI及单茎叶面积较高、每穗粒数较多、总颖花量大、粒叶比协调和日产量高等基本特征。高产类型早稻品种生育期为105-110 d,日产量75-78 kg·hm-2·d-1,每穗粒数125-140粒,千粒重26-28 g;高产类型晚稻品种生育期约115 d,日产量77-81 kg·hm-2·d-1,每穗粒数140-160粒,千粒重24-28 g。  相似文献   
63.
季淮 《安徽农学通报》2008,14(20):81-82
伴随着后工业时代的来临,许多传统工业衰落,基地沦为弃置地。这些工业弃置地用途单一、功能过时,但它们是具有严格逻辑的再生资源、景观特色和历史价值,其改造、更新和开发实践的成功与失败引起了广泛的关注和研究。中国中小城市的后工业景观设计实践比较迟,且设计改造大于保留,如何更好的利用这些资源,需要合理的思路。本文分析探讨了一些具体措施,用于工业废弃地的保护和利用。  相似文献   
64.
目的探讨Von Hipple—Lindau病的诊断及治疗.方法报道VonHippie—Lindau病1例,总结延髓血管母细胞瘤手术的经验教训,结果患者于术后1个月临床死亡.结论通过详细的综合检查及治疗,并及时总结延髓血管母细胞瘤手术方法,从而提高对该病的诊治水平.  相似文献   
65.
OBJECTIVE: To determine if screw loosening in triple pelvic osteotomies (TPO) is minimized when screws cranial to the ilial osteotomy had maximal sacral purchase. STUDY DESIGN: Prospective study. ANIMALS: Forty-six dogs with decreased acetabular coverage of the femoral head and minimal degenerative joint changes. METHODS: TPOs were performed where screws cranial to the ilial osteotomy were inserted to maximally engage sacral bone. Data collected were: use of ilial and ischial cerclage wire, screw length, ventrodorsal radiographic sacral width (most caudal aspect), pelvic canal diameter, and sacral penetration of the 3 cranial screws. On all subsequent radiographs, changes in screw position, pelvic canal diameter, and sacral purchase were noted. RESULTS: For 69 TPOs, 414 screws were used. Mean radiographic cranial screw length was 34.54 mm. Combined sacral depth of all 3 screws was 93.3% of sacral width. All osteotomies healed uneventfully. Twenty-four screws (6%) loosened with 12 being in the most cranial positions. Use of ischial or ilial cerclage wires did not statistically influence screw loosening. Pelvic diameter decreased by a mean of 7.79% from postoperative radiographs to the last radiographic recheck. CONCLUSIONS: By sufficiently engaging the sacrum with screws cranial to the ilial osteotomy, implant failures can be avoided and screw loosening minimized when a 6-hole TPO plate is used. CLINICAL RELEVANCE: To minimize screw-loosening in TPO, screws inserted cranial to the ilial osteotomy should be inserted to maximum sacral depth without penetrating the vertebral canal.  相似文献   
66.
The potential of bacteriophage therapy to control bacterial disease in farmed fish was tested using, as an example, furunculosis of Atlantic salmon, caused by Aeromonas salmonicida subsp. salmonicida.

In vivo testing with Atlantic salmon and rainbow trout (Oncorhynchus mykiss Walbaum) showed no adverse effects, with bacteriophage generally cleared within 96 h of administration by either intraperitoneal (i.p.) injection or oral in-feed.

Juvenile Atlantic salmon were administered a combination of bacteriophage O, R and B (1.9 × 108 pfu fish− 1) by i.p. injection, after they had been challenged with A. salmonicida subsp. salmonicida 78027, also by i.p. injection. The fish that were injected with bacteriophage immediately after challenge died at a significantly slower rate then those that were either not treated with bacteriophage, or treated 24 h post-challenge. However, the end result (100% mortality) was not affected.

In further experiments the effects of oral (1.88 × 105 pfu g− 1 fish− 1 daily for 30 days), bath (1.04 × 105 ml− 1 daily for 30 days) and i.p. (6.25 × 107 pfu fish− 1) phage treatment to control furunculosis in experimentally infected Atlantic salmon were compared with antibiotherapy (treatment with 10 mg kg− 1 bw− 1 day− 1 oxolinic acid for 10 days), using an indirect cohabitation challenge. No protection was offered by any of the bacteriophage treatments, compared to the positive challenge group, although significant protection was offered by the oxolinic acid treatment. Analysis of samples taken from the trials demonstrated that bacteriophage were correctly administered to the fish and, on occasion, were isolated from fish that had succumbed to furunculosis. It was also shown that bacteriophage resistant A. salmonicida subsp. salmonicida isolates could be recovered from mortalities in all the treatment groups.

The results suggest that, although there were no safety problems associated with the approach, furunculosis in Atlantic salmon is not readily controllable by application of bacteriophage.  相似文献   

67.
农田土壤中残留和滋生多种病原菌会对人体健康和生态环境带来显著的安全隐患,开展针对性的生物修复研究十分迫切。噬菌体疗法靶向灭活土壤中病原菌的技术为修复此类污染土壤提供了全新途径。本研究以南京城郊某奶牛场牛粪堆积池周边,粪肠杆菌和假单胞菌复合污染农田土壤为例,首先筛选和纯化获得两株专一型噬菌体(YSZ1和YSZ5),再人为加速其宿主谱的表达过程,获得对应的多价噬菌体(YSZ1R和YSZ5K),并进行生物学特性(形态、核酸、最佳感染复数、一步生长曲线等)鉴定,结果表明:在水相和污染土壤中不同噬菌体对于同步灭活病原菌的能力依次为YSZ5KYSZ1RYSZ5YSZ1,并且施用多价噬菌体疗法有助于维护和改善修复后土壤微生物生态功能多样性与稳定性。本研究结果可为噬菌体疗法靶向灭活土壤中多种病原菌提供切实可行的修复技术。  相似文献   
68.
日本森林疗法及启示   总被引:4,自引:8,他引:4  
森林疗法是基于实证实验,科学利用森林浴效果,达到增进身心健康和预防疾病目标的替代疗法。文中介绍了森林疗法的起源、基本含义和机理,综述了日本森林疗法的发展历程、证实研究的最新进展和森林疗法线路设计理念,分析了日本森林疗法基地认证和森林理疗师资格考试制度,还对北京市引进与开展森林疗法进行了展望,认为推动森林疗法对增进居民健康、提高森林经营水平和发展区域经济都具有重要作用。  相似文献   
69.
选择搭配具有疗养功效的园艺植物进行屋顶花园设计,能够充分发挥植物的景观效果和功能特性,从而达到家庭保健的功能。综述了园艺疗法的作用原理和优势,详细介绍了针对老年人、康复人群及亚健康人群的屋顶花园设计方法。  相似文献   
70.
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