全文获取类型
收费全文 | 3422篇 |
免费 | 202篇 |
国内免费 | 371篇 |
专业分类
林业 | 62篇 |
农学 | 779篇 |
基础科学 | 2篇 |
204篇 | |
综合类 | 1125篇 |
农作物 | 480篇 |
水产渔业 | 220篇 |
畜牧兽医 | 643篇 |
园艺 | 411篇 |
植物保护 | 69篇 |
出版年
2024年 | 17篇 |
2023年 | 60篇 |
2022年 | 72篇 |
2021年 | 96篇 |
2020年 | 143篇 |
2019年 | 112篇 |
2018年 | 62篇 |
2017年 | 104篇 |
2016年 | 180篇 |
2015年 | 176篇 |
2014年 | 190篇 |
2013年 | 187篇 |
2012年 | 239篇 |
2011年 | 265篇 |
2010年 | 250篇 |
2009年 | 270篇 |
2008年 | 274篇 |
2007年 | 265篇 |
2006年 | 195篇 |
2005年 | 143篇 |
2004年 | 131篇 |
2003年 | 106篇 |
2002年 | 77篇 |
2001年 | 69篇 |
2000年 | 58篇 |
1999年 | 35篇 |
1998年 | 22篇 |
1997年 | 27篇 |
1996年 | 34篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 27篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1981年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有3995条查询结果,搜索用时 125 毫秒
71.
对家蚕多星纹基因ms的SSR标记定位分析 总被引:1,自引:0,他引:1
对家蚕幼虫斑纹突变多星纹基因ms进行分子标记定位,有益于对多星纹性状的分子标记辅助选择和对该基因的定位克隆研究。利用家蚕雌性染色体在减数分裂过程中不发生交换的特点,采用幼虫斑纹为素斑(p)的家蚕品系C108,幼虫斑纹为多星纹(ms)的家蚕品系g02,组配正反交群体(g02×C108)F1♀×g02♂和g02♀×(g02×C108)F1♂,分别记作BC1F和BC1M,利用已经构建的家蚕SSR分子标记连锁图谱中第12连锁群上的18对SSR标记引物在亲本间进行多态性筛选。BC1F群体中的普通斑个体均表现出与(g02×C108)F1相同的杂合型带型;而所有多星纹个体的带型与亲本g02一致,为纯合型。结果筛选出S1206、S1208、S1210、C5553S3共4个与家蚕ms连锁的SSR标记。利用BC1M群体构建家蚕ms及其连锁的SSR标记遗传连锁图,连锁图的图距为34.5 cM,4个SSR标记及ms的排列次序为S1206—S1208—S1210—C5553S3—ms,ms位于34.5 cM处,与ms最近的标记为C5553S3,遗传距离为12.4 cM。依据该SSR标记遗传连锁图谱可对ms进一步精确定位。 相似文献
72.
73.
AIM: To investigate the protective role of heat-shock protein 70 (HSP70) in the pathogenesis of gastric mucosal damage in cirrhotic rats with portal hypertensive gastropathy (PHG).METHODS: The rat model of liver cirrhosis with PHG was established by injection with tetrachloride.The animals were divided into normal control group, PHG group, PHG+heat treatment group, PHG+BPI21 group and PHG+endotoxin groups.The endotoxin used in the experiment was at the dose of 3 mg/kg and endotoxin antagonist BPI21 was at the dose of 2 mg/kg.HSP70 was induced by pre-treating the animals with mild whole-body heating.The levels of HSP70 and tumor necrosis factor alpha (TNF-α) in the gastric mucosa were measured by ELISA.Furthermore, the pathological changes of the gastric mucosa were observed under microscope with HE staining.RESULTS: Compared with the normal control rats, the rats in PHG group showed obvious gastric pathological lesion, decrease in HSP70 production and increase in TNF-α level in the gastric mucosa, and increased endotoxin concentration in the plasma.Compared with PHG+endotoxin group, the gastric mucosal lesion in PHG+BPI21 group was significantly attenuated, accompanied by the increase in HSP70 production and decrease in TNF-α level in the gastric mucosa.Heat treatment increased HSP70 production and decreased TNF-α concentration in the PHG rats, thus attenuating the gastric mucosal damage.CONCLUSION: HSP70 alleviates the gastric mucosal lesion induced by endotoxin in cirrhotic rats with PHG and decreases the concentration of TNF-α in gastric mucosa, indicating a protective role of HSP70 in the pathogenesis of gastric mucosal damage in PHG. 相似文献
74.
林木遗传工程及木质素的生物合成调节(英文) 总被引:1,自引:0,他引:1
林木遗传工程有利于保存林木遗传资源,改善全球气候,减轻自然林的过度采伐和满足人类日益增长的林木产品需求。控制林木真菌、病毒病、虫害和杂草的遗传工程方法正被广泛地研究和应用。尽管转基因林木的历史不长,种类不多,但它有广泛的应用前景。目前,抗除草剂基因、抗虫基因以及和木材质量相关的基因已被分离并应用于林木遗传工程。植物分子生物学和基因组学中的新技术使得高效林木遗传改良成为可能并将促进这些技术的商业化应用。木质素的应用已有一百年的历史,但木质素生物合成的全过程并不完全清楚。有关松树自然突变体和转基因林木的最新研究结果表明,木质素的生物合成是一个可以调节的过程。这些发现对完善木质素的生物合成途径、加深对木质素前体生物合成途径的理解和通过遗传工程改善木材质量有促进作用。本文综述了林木遗传工程在这些领域中取得的一些进展。 相似文献
75.
76.
工能基因组学:T-DNA介导的基因诱捕和植物基因鉴定(英文) 总被引:2,自引:0,他引:2
拟南芥菜、水稻、蕃茄、土豆、玉米、小麦和大豆的全基因组测序为植物细胞和发育生 物学研究提供了许多有用的信息。基因组学的中心任务是利用这些信息去探索蛋白质的功能 和鉴定与发育有关的重要基因。尽管依赖于毁坏基因和产生可识别的突变表型的经典遗传学 方法仍然是极为成功的基因鉴定方法,借助于报告基因结构,随机插入植物基因组的T-DNA 介导的基因诱捕正发展成为植物细胞和发育生物学研究的极强有力的技术。本文描述了基因 诱捕、启动子诱捕和增强子诱捕在植物生物学中的应用,并且希望这些基因鉴定方法有助于 植物分子生物学家和生物技术工作者的研究。 相似文献
77.
Four populations representing the entire natural distribution range of Pinus brutia (Ten.) in Crete (Greece) were sampled to determine: (1) Altitudinal variation within populations of Lassithi, Vorizia, Koustagerako, and Samaria, and; (2) Longitudinal variation among the four populations, based on morphological and anatomical differences in cone, needle and seed characteristics. Samples were collected from 10 trees per altitude, at three altitudes in each population. A total of 12 morphological and anatomical traits from needles, cones and seeds were analyzed to assess the altitudinal and longitudinal variations of the species in the island. The number of teeth per cm showed significant (P<0.01) differences between altitudes in Samaria, Vorizia and Lassithi, while needle length, width and the number of resin canals showed significant differences (P<0.01) between altitudes in Koustagerako. Cone width showed patterns of variation along the altitudinal gradient in Koustagerako, Samaria and Vorizia. Most traits had their highest means at the middle altitudes (650masl) in all the four populations. Overall, no clear altitudinal differentiation was detected, probably due to high rate of gene flow. Longitudinal variability showed a clear pattern of differentiation along the east–west climatic gradient. Needle length, width, sheath length, number of teeth per cm and the number of resin canals were the most useful traits for determining the climatic gradient clines. 相似文献
78.
GAO Qing LI Shu-ren XUN Li-ying YUAN Ke-xin XIE Yue-tao ZHANG Qian-hui HAO Qing-qing DANG Yi QI Xiao-yong 《园艺学报》2015,31(4):640-646
AIM: To investigate the effects of transplantation of bone marrow mesenchymal stem cells (BMSCs) modified by bcl-2 gene on myocardial cell apoptosis, angiogenesis and cardiac function in the rabbit after acute myocardial infarction (MI).METHODS: The rabbit BMSCs were isolated, cultured and purified in vitro. The BMSCs were transfected with adenovirus or adenovirus-Bcl-2. The rabbit model of MI was established by ligation of left anterior descending branch. The rabbits were injected with Ad-Bcl-2-BMSCs (MI+Bcl-2-BMSCs group), Ad-BMSCs (MI+BMSCs group) and DMEM (MI group) in infarction marginal zone 2 weeks after ligation. The cardiac function was evaluated by echocardiography.The apoptosis of myocardial cells was measured by TUNEL. The mRNA expression of VEGF was detected by real-time PCR. The expression of CD31 was examined by immunohistochemical staining, and new blood capillaries were counted at 4 weeks after BMSCs transplantation. The correlation of the above values with cardiac function was analyzed.RESULTS: The cardiac function was better, the apoptotic rate was lower, the mRNA expression of VEGF and the capillary density were higher in both MI+Bcl-2-BMSCs group and the MI+BMSCs group than those in MI group, and those in MI+Bcl-2-BMSCs group increased more obviously.The left ventricular ejection fraction (LVEF) had a negative correlation with the myocardial cell apoptosis rate. A positive correlation with the mRNA expression level of VEGF and the capillary density was also observed.CONCLUSION: The transplantation of BMSCs modified by bcl-2 gene significantly reduces the myocardial cell apoptosis, promotes angiogenesis, improves heart function of the rabbits with MI. 相似文献
79.
80.
采用国产硅胶Gk254(60型)代替进口Glass bead的改良方法抽提土壤微生物DNA,然后设计了一对扩增木聚糖酶基因片段的新简并引物,对抽提的土壤微生物DNA进行PCR扩增。扩增片段连接pMD18T载体,转化大肠杆菌,重组片段通过酶切进行RFLP分析后,测序分析得到10个木聚糖酶基因片段。对所得片段翻译的氨基酸序列进行BLAST分析表明有8个片段与来自放线菌的木聚糖酶具有较高的同源性,2个与假单胞菌的木聚糖酶具有较高的同源性。所得10个木聚糖酶片段的氨基酸序列同源性比较显示,第27个氨基酸均为天冬酰胺(N),暗示这些来自土壤微生物DNA的基因片段编码耐碱的木聚糖酶。通过构建系统进化树,发现扩增的木聚糖酶片段之间的相似性均在70%以上。 相似文献