全文获取类型
收费全文 | 5877篇 |
免费 | 302篇 |
国内免费 | 672篇 |
专业分类
林业 | 686篇 |
农学 | 708篇 |
基础科学 | 427篇 |
861篇 | |
综合类 | 1961篇 |
农作物 | 437篇 |
水产渔业 | 228篇 |
畜牧兽医 | 1013篇 |
园艺 | 205篇 |
植物保护 | 325篇 |
出版年
2024年 | 22篇 |
2023年 | 96篇 |
2022年 | 187篇 |
2021年 | 225篇 |
2020年 | 224篇 |
2019年 | 189篇 |
2018年 | 161篇 |
2017年 | 211篇 |
2016年 | 177篇 |
2015年 | 227篇 |
2014年 | 236篇 |
2013年 | 299篇 |
2012年 | 383篇 |
2011年 | 399篇 |
2010年 | 370篇 |
2009年 | 318篇 |
2008年 | 289篇 |
2007年 | 269篇 |
2006年 | 256篇 |
2005年 | 277篇 |
2004年 | 169篇 |
2003年 | 225篇 |
2002年 | 368篇 |
2001年 | 297篇 |
2000年 | 202篇 |
1999年 | 139篇 |
1998年 | 84篇 |
1997年 | 81篇 |
1996年 | 58篇 |
1995年 | 61篇 |
1994年 | 51篇 |
1993年 | 51篇 |
1992年 | 39篇 |
1991年 | 60篇 |
1990年 | 41篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1962年 | 1篇 |
1958年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有6851条查询结果,搜索用时 45 毫秒
941.
QIU Chui-yuan TANG Wen-jie DAI Yun WU Yue-heng SUN Fen-yong CHEN Qiong-yu LI Ling-song△ HONG An 《园艺学报》2005,21(7):1378-1383
AIM: To screen the cytotoxicity of degradable calcium metaphosphate (dCMP) compared with hydroxyapatite (HA). The proliferation and differentiation abilities of human marrow mesenchymal stem cells (MSC) were used to exhibit the cytotoxicity. METHODS: The cell morphology of MSC was analysed after direct contact with dCMP at different time points by scanning electron microscopy analysis. The degradation products of dCMP and HA were analysed with inductively coupled plasma torch and ion chromatography. The cytotoxic effect of degradation products of dCMP was evaluated by FACS, quantitative assay of ALP and ARS, respectively. RESULTS: dCMP enhanced the proliferation of MSC, but didn't interfere the osteogenic differentiation process of MSC and its mineralization. HA inhibited the proliferation of MSC and the mineralization of osteogenic differentiated MSC, while it did not interfere the osteogenic differentiation process of MSC. CONCLUSION: dCMP had a better cytocompatibility with MSC than HA, which might allow for its use as skeleton scaffolds. 相似文献
942.
ZHANG Zhan JIA Li-ting HOU Lei WANG Xue-mei CHANG Cai-hong YANG Ru-jing ZHANG Xi LIU Sheng-hong ZHENG Fang GONG Fei-li 《园艺学报》2005,21(12):2457-2461
AIM: To detect the effects of NK cells on the etiology of severe pre-eclampsia. METHODS: The peripheral blood and umbilical blood from severe pre-eclamptic patients and normal late pregnant women were collected. NK cells were seperated in percoll and counted by SAP. The proliferating ability of NK cells was measured by MTT and killing power of NK cells was determined by [51Cr] releasing test. The immunohistochemistry method was used to detect the quantity of NK cells and the expression of HLA-G in placenta of them. RESULTS: (1) Compared with that in normal late pregnant women, the counts of the NK cells in peripheral blood, umbilical blood and decidua of severe pre-eclamptic patients were significantly higher (all P<0.05). (2) Compared with that in normal late pregnant women, proliferating and killing ability of NK cells in peripheral blood and umbilical blood of severe pre-eclamptic patients were significantly higher. (3) The expression of HLA-G protein in placenta of severe pre-eclampsia group was lower than that in normal group (P<0.05). CONCLUSION: The quantity of NK cells in severe pre-eclamptic patients is increased with stronger biologic function. They may be related with the pathogenesis of severe pre-eclampsia. 相似文献
943.
944.
以吐鲁番7年生‘无核白’为试验材料,研究不同密度光伏板对‘无核白’叶幕微气候、叶片质量以及果实品质的影响,旨在找到合适的光伏板密度,为葡光互补新型栽培模式的推广提供科学依据。结果表明:随着光伏板密度的增大,叶幕空气温度降低,空气相对湿度增大,光照强度显著降低。‘无核白’葡萄叶片质量、果实品质随着光伏板密度的增大呈现出先上升后下降的变化趋势,中度遮阴条件下,‘无核白’叶片的纵、横径,叶绿素含量和果实中可溶性固形物含量均表现最佳。在吐鲁番地区采用光伏板遮阴对‘无核白’葡萄叶幕微气候有显著影响,适度遮阴有利于缓解夏季高温强光对葡萄生长发育的危害,但过度遮阴会产生负面影响。在吐鲁番地区推广葡光互补栽培模式时,建议选择光伏板的间隔为1.0 m。 相似文献
945.
本试验旨在研究玉米一豆粕型无鱼粉日粮中不同牛磺酸的添加量对笼养后备蛋鸭机体抗氧化功能的影响.试验采用单因素完全随机分组设计,选择12周龄、健康、体重相近的金定蛋鸭180只,随机分为5组,每组6个重复,每个重复6只.Ⅰ组为对照组,饲喂玉米一豆粕无鱼粉日粮,Ⅱ、Ⅲ、Ⅳ、Ⅴ组在基础日粮的基础上分别添加0.05%、0.10%、0.15%和0.20%的牛磺酸,试验期为6周.结果表明,与对照组相比,在日粮中添加0.15%牛磺酸可以显著提高血清还原型谷胱甘肽酶(GSH-Px)、超氧化物歧化酶(SOD)、总抗氧化能力(T-AOC)和过氧化氢酶(CAT)活性(P<0.05),并且显著降低了丙二醛(MDA)含量(P<0.05);在日粮中添加0.10%和0.15%牛磺酸可以显著提高肝脏GSH-Px、SOD、T-AOC和CAT活性(P<0.05),并且显著降低MDA含量(P<0.05).结果提示,在笼养后备蛋鸭日粮中添加0.10%的牛磺酸,可显著提高机体抗氧化性能,并且经济效益最佳. 相似文献
946.
猕猴桃种间杂交的新种质 总被引:7,自引:1,他引:7
美味猕猴桃26号(ActinidiadeliciosaNo.26)与软枣猕猴桃(Actinidiaarguta)种间杂交,多数杂种F1表现为中间类型偏父本,少数偏母本,由中间类型杂种雌株中选出果大、绿皮、无毛的株系。经染色体鉴定、过氧化物酶同功酶分析和杂种实生苗及其形态特征的观察,确认此种间杂种为猕猴桃属的新种质。 相似文献
947.
XING Meng-yao MA Xiao-juan GONG Xue-li Maimaitizunong MAISUER YU Wen-yan ZHANG Xue-mei SUN Zhan 《园艺学报》2018,34(11):2101
AIM: To study the effect of p65 gene silencing by adeno-associated virus type 9 (AAV9)-mediated RNA interference on angiotensin Ⅱ (Ang Ⅱ; 10-6 mol/L for 24 h)-induced apoptosis of rat ventricular H9c2 myocytes, and to elucidate the possible mechanism. METHODS: The H9c2 cells were transfected with rAAV9-eGFP and rAAV9-eGFP-NF-κB p65-siRNA at multiplicity of infection (MOI)=4×106 vg/cell. eGFP expression in the cells was observed under an inverted fluorescence microscope, and the percentage of eGFP positive cells was determined by flow cytometry. The expression of p65 was determined by Western blot. CCK-8 assay was used to measured the viability of transfected H9c2 cells. The apoptosis of the cells transfected with the virus and with Ang Ⅱ stimulation was analyzed by flow cytometry. RESULTS: The cells began to exhibit eGFP expression on the 2nd day after transfection. The fluorescence intensity was increased over the time of transfection. eGFP expression reached the maximum on the 5th day, and the transfection efficiency was (52.7±1.9)% at this time point. Compared with blank control group, no significant effect of AAV9 on the viability of H9c2 cells was observed. In resting state, p65 in the H9c2 cells had a certain activity. After Ang Ⅱ stimulation, the activity of p65 was obviously increased, while transfection of rAAV9-eGFP-NF-κB p65-siRNA effectively inhibited the expression of p65. The apoptosis of H9c2 cells in Ang Ⅱ stimulation group was significantly higher than that in blank control group, while transfection of rAAV9-eGFP-NF-κB p65-siRNA effectively inhibited apoptosis of H9c2 cells. CONCLUSION: Transfection of rAAV9-eGFP-NF-κB p65-siRNA effectively inhibits the expression of p65 gene of NF-κB pathway in the H9c2 cells without causing cell growth inhibition, and reduces the apoptosis induced by Ang Ⅱ. 相似文献
948.
树木对重金属的抗性机理研究进展 总被引:4,自引:0,他引:4
土壤重金属污染问题是当今世界较为严重的环境问题之一。树木生物量高,根系发达,一般不进入食物链,一些树木对环境中重金属具有较强的吸收和积累作用,防止土壤金属污染的扩散。为了深入探索树木应对重金属污染的抗性机理,笔者主要从根系分泌物、内生细菌与菌根、螯合作用、抗氧化系统以及区室化作用等方面综述了近年来,尤其是近5年来树木应对重金属的抗性机制研究进展,发现由于重金属对于树木毒害作用的多方面性,树木重金属抗性机理具有复杂性,因此许多机理仍不清晰,今后还需要利用不断更新的技术手段,研究其不同抗性机理的协同作用,对其机制进行更深入系统的研究。最后,笔者展望了通过生物技术手段的改造,将树木应用于环境修复的前景。 相似文献
949.
中国主栽双孢蘑菇菌株的DNA多态性 总被引:11,自引:3,他引:11
本文以中国双孢蘑菇不同主栽产区的9个具代表性的双孢蘑菇菌株为材料,用20个随机引物对其进行RAPD分析。结果表明,20个随机引物中,有15个随机引物的扩增产物DNA片段表现出明显的多态性,其中每个引物对不同菌株扩增出的DNA片段数目各不相同,而且不同引物扩增出的DNA带谱也不同,差异较大。这15个引物对供试菌株总共扩增出168条DNA片段,其中最大的片段可达6.77kb,最小的DNA片段仪有0.31kb。同时,比较了供试菌株两两间的遗传相似性,发现它们之间的变化不大,其相似系数从0.6891到1.0000,而平均相似系数仅为0.8500,表明供试菌株之间的亲缘关系较近,遗传变异不丰富。另外,采用系统聚类法中的类平均法,对供试菌株相似系数两两间进行聚类分析并生成树状图谱,直观准确地揭示了它们之间的差异。当相似系数为77%时,所有供试菌株都被聚为一大类,说明我国主栽双孢蘑菇菌株的遗传基础较狭窄,可能来源于同一品系,这为进一步开展双孢蘑菇菌种的遗传改良提供了理论依据。 相似文献
950.
不同培养基对香菇菌丝体酯酶同工酶的影响 总被引:2,自引:1,他引:2
本文应用垂直板聚丙烯酰胺凝胶电泳,对在不同培养基上生长的香菇菌丝体进行酯酶同工酶分析。结果表明,不同培养基会导致香菇菌丝体酯酶同工酶酶谱产生差异。 相似文献