全文获取类型
收费全文 | 20781篇 |
免费 | 1212篇 |
国内免费 | 1878篇 |
专业分类
林业 | 1467篇 |
农学 | 977篇 |
基础科学 | 984篇 |
2029篇 | |
综合类 | 10612篇 |
农作物 | 1723篇 |
水产渔业 | 879篇 |
畜牧兽医 | 2803篇 |
园艺 | 1555篇 |
植物保护 | 842篇 |
出版年
2024年 | 186篇 |
2023年 | 444篇 |
2022年 | 975篇 |
2021年 | 925篇 |
2020年 | 858篇 |
2019年 | 856篇 |
2018年 | 556篇 |
2017年 | 962篇 |
2016年 | 671篇 |
2015年 | 972篇 |
2014年 | 1132篇 |
2013年 | 1331篇 |
2012年 | 1680篇 |
2011年 | 1741篇 |
2010年 | 1647篇 |
2009年 | 1509篇 |
2008年 | 1465篇 |
2007年 | 1400篇 |
2006年 | 1269篇 |
2005年 | 961篇 |
2004年 | 627篇 |
2003年 | 364篇 |
2002年 | 375篇 |
2001年 | 397篇 |
2000年 | 357篇 |
1999年 | 128篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1981年 | 3篇 |
1965年 | 1篇 |
1962年 | 3篇 |
1956年 | 5篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
972.
脂肪型脂肪酸结合蛋白基因多态性与鸡肉品质性状的关系研究 总被引:5,自引:3,他引:5
采用PCR-SSCP技术分析了A-FABP基因在北京油鸡、矮脚鸡、泰和乌骨鸡、崇仁麻鸡、鹿苑鸡、霞烟鸡等6个地方品种鸡和AA肉鸡中的多态性,发现的3个多态位点的基因型频率和等位基因频率在不同品种之间存在显著差异。测序分析表明:多态位点的产生分别是由碱基C→T、G→A以及C→T的变异引起的。在北京油鸡、矮脚鸡群体中对各多态位点不同基因型与体重、肌内脂肪、腹脂率等脂肪相关性状进行关联分析,结果显示不同基因型间在部分肉品质相关性状上差异显著。 相似文献
973.
974.
姬松茸ISSR特异扩增体系的研究 总被引:1,自引:0,他引:1
为了建立稳定的姬松茸(Agaricus blazei Murill)简单序列重复区间(Inter-Simple Sequence Repeats,ISSR)分子标记技术体系,笔者通过单因子试验分别研究了模板DNA、Mg2 浓度、dNTP、引物浓度和Taq酶用量对姬松茸ISSR-PCR扩增的影响,确定了姬松茸ISSR分析的最佳PCR条件为:25μL反应体系中,模板DNA20ng,引物0.75μmol/L,dNTP200μmol/L,Mg2 2.0mmol/L,Taq DNA polymerase 1.5U。并应用该优化体系筛选到6个适合姬松茸ISSR-PCR扩增的引物,为利用ISSR标记技术研究姬松茸的种质资源提供了参考。 相似文献
975.
976.
香蕉A基因组品种间遗传关系的SSR检测 总被引:3,自引:2,他引:3
应用SSR技术,对32个香蕉A基因组类型品种(系)的遗传关系进行了检测。40对SSR引物在32个品种(系)中分别扩增带数在3~15个,平均每个SSR座位可检测2.99个多态性带;引物的多态信息量(PIC)在0.00~0.88,平均0.62。依据SSR数据计算的品种间遗传距离在0.00%~34.27%,平均12.45%,大多数品种间的遗传变异非常有限,但也存在着遗传差异突出的品种:FHIA25、Yangambi KM5、Pisang Jari Buaya、Rose和皇帝蕉。依据26%的遗传距离,除了FHIA25和Pisang Jari Buaya单独化成1组外,其它30个品种可以分为2组:品种间遗传差异相对较高的组I和品种间遗传差异相对较低的组Ⅱ。Williams与引进的洪都拉斯3号、M931之间,洪都拉斯1号和洪都拉斯2号之间,高脚青芽蕉和高脚顿地雷分别没有区分开来,这可能是同物异名,也可能是同一品种未能分辨的突变体。 相似文献
977.
978.
AIM: To explore the effect of the pretreatment of hypertonic saline (HTS) in hepatic ischemia reperfusion (I/R) injury.METHODS: The rats were divided into sham group (sham group), ischemia reperfusion group (IR group) and pretreatment of hypertonic saline group (HTS group). Partial hepatic ischemia reperfusion model was used. The rats were sacrificed at the time of 1 h, 3 h, 6 h, 12 h and 24 h after reperfusion in each group, respectively. Blood samples were obtained to examine ALT. The expression of the CD11b/CD18 (Mac-1) on the neutrophils was analyzed by flow cytometry. RT-PCR and Western blotting were used to examine the expression of intercellular adhesion molecule-1 (ICAM-1) in livers and chromatometry was performed to detect the activity of myeloperoxidase (MPO) in livers. The morphology of hepatocytes and the structure of sinusoid were observed by histological examinations. RESULTS: ① HTS pretreatment decreased the level of ALT at the time points of 3 h, 6 h and 12 h after reperfusion (P<0.05). ② Mac-1 expression in HTS group was lower at 6 h and 12 h after reperfusion compared with IR group (P<0.05). ③ MPO activity in HTS group was lower at 6 h, 12 h and 24 h compared with IR group (P<0.05). ④ RT-PCR and Western blotting analysis indicated that the pretreatment of HTS inhibited the expression of ICAM-1 in livers after reperfusion. ⑤ Moderate hepatocyte swelling and few neutrophil infiltration were observed in HTS group.CONCLUSION: Pretreatment with HTS has the effect on hepatic ischemia reperfusion injury by inhibiting the expression of Mac-1 on circulating neutrophils and the expression of ICAM-1 in the liver. 相似文献
979.
AIM: To study the expression of nucleostemin (NS) gene in human breast tumor tissues and the relations of NS gene expression level with histological grades,histological types and TNM stages of the tumor.METHODS: Total RNA was isolated from human breast tumor tissue.The methods of electrophoresis and RT-PCR were used in measuring NS gene expression level,and the relations of NS gene expression level with histological grades,histological types and TNM stages of the tumor were analyzed.RESULTS: The results indicated that there was no NS gene expression detected in normal breast tissues,and NS gene expression in malignant breast tumor tissues (P<0.01) was higher than that in the benign breast tumor tissues.The higher histological grades of the breast cancer showed the stronger NS gene expression (P<0.01),the higher TNM stages of the breast cancer showed the stronger NS gene expression (P<0.01),and the level of NS gene expression had not correlation with the histological types (P>0.05).CONCLUSION: It is suggested that there is no relation of NS gene expression level with histological types of the breast cancer,but there is a marked correlation of NS gene expression level with the histological grades and TNM stages. 相似文献
980.
AIM: To explore the changes of excitatory amino acids and N-methyl-D-aspartate receptor (NMDAR) in brain undergoing ischemia-reperfusion injury following hepatic portal occlusion (HPO) in vivo.METHODS: The electrolytes and pH of portal vein blood,the content of Glu and Asp in brain,and the expression of NMDAR mRNA were studied with blood-gas analysis,HPLC and semi-quantitative RT-PCR method in two groups(HPO or sham),respectively.Three time points(6 h,12 h and 24h after reperfusion) were included.RESULTS: HPLC measure showed that the content of cortex Glu and Asp in group HPO elevated significantly after reperfusion compared with sham group, the peaks were at 6 h and 24 h [Glu:(349±145) μg·g-1wt,(456±203) μg·g-1wt vs (238±24) μg·g-1wt,(225±59) μg·g-1wt;Asp:(134±50) μg·g-1wt,(166±50) μg·g-1wt vs (99±24) μg·g-1wt,(71±20) μg·g-1wt].Moreover,semi-quantitative RT-PCR analysis discovered that the expression of NMDAR mRNA increased significantly ,the subunit NR1 mRNA was higher in reperfusion 6 h and last to 12 h(1.63±0.06 vs 1.18±0.05;1.73±0.06 vs 1.17±0.03),the peak of NR2B mRNA was in 12 h (1.75±0.04 vs 1.18±0.05) ,but they did not further increase after reperfusion for 24 h.CONCLUSION: HPO increases the content of Glu and Asp and the expression of NMDAR in brain cortex.The Glu-NMDAR pathway plays a role in the mechanism for the brain injury after HPO.The products of IR injury might be the key factor to cause EAAs acumulation in synapse space. 相似文献