全文获取类型
收费全文 | 88907篇 |
免费 | 4713篇 |
国内免费 | 9066篇 |
专业分类
林业 | 8623篇 |
农学 | 8587篇 |
基础科学 | 5409篇 |
11787篇 | |
综合类 | 34933篇 |
农作物 | 6205篇 |
水产渔业 | 4308篇 |
畜牧兽医 | 12579篇 |
园艺 | 5233篇 |
植物保护 | 5022篇 |
出版年
2024年 | 533篇 |
2023年 | 1471篇 |
2022年 | 3391篇 |
2021年 | 3808篇 |
2020年 | 3444篇 |
2019年 | 3464篇 |
2018年 | 2507篇 |
2017年 | 3750篇 |
2016年 | 2841篇 |
2015年 | 4034篇 |
2014年 | 4085篇 |
2013年 | 4838篇 |
2012年 | 6307篇 |
2011年 | 6724篇 |
2010年 | 6445篇 |
2009年 | 5823篇 |
2008年 | 5793篇 |
2007年 | 5568篇 |
2006年 | 4763篇 |
2005年 | 4211篇 |
2004年 | 2374篇 |
2003年 | 1748篇 |
2002年 | 1588篇 |
2001年 | 1637篇 |
2000年 | 1662篇 |
1999年 | 1552篇 |
1998年 | 1122篇 |
1997年 | 946篇 |
1996年 | 923篇 |
1995年 | 817篇 |
1994年 | 754篇 |
1993年 | 742篇 |
1992年 | 603篇 |
1991年 | 538篇 |
1990年 | 441篇 |
1989年 | 359篇 |
1988年 | 279篇 |
1987年 | 182篇 |
1986年 | 144篇 |
1985年 | 83篇 |
1984年 | 49篇 |
1983年 | 42篇 |
1982年 | 41篇 |
1981年 | 57篇 |
1980年 | 32篇 |
1979年 | 25篇 |
1965年 | 11篇 |
1964年 | 13篇 |
1963年 | 11篇 |
1956年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
饲粮中添加抗菌肽对肉鸭增重及血清尿素氮、总蛋白水平的影响 总被引:12,自引:1,他引:12
240只1日龄肉鸭随机成分4组,每组设3个重复,对照组用基础日粮,试验组在基础日粮上每千克分别添加1、2、3mL抗菌肽制剂。结果显示:1)2、3mL/kg添加量组增重效果显著(P<0.05),3mL/kg添加量组最佳;净肉率升高,达到显著水平(P<0.05),其中主要是胸肌率上升;腹脂率降低但差异不显著(P>0.05);料重比无显著变化(P>0.05)。2)血清总蛋白浓度差异不显著(P>0.05),但尿素氮浓度下降,2、3mL/kg添加量组达显著水平(P<0.05),3mL/kg添加量组最低。 相似文献
82.
83.
本文论述了中国山羊的起源、品种遗传资源及其遗传多样性的研究进展。最新调查 显示中国的山羊品种达50个,其中43个为地方品种,4个培育品种,3个引入品种,许多品种 具有独特的生产性能或适应能力。大量研究表明,我国山羊遗传多样性较为丰富。 相似文献
84.
ZHOU Shu-lu YE Ren-gao LIU Xiao-bo ZHANG Hong XU Han-shi DU Yong LI You-ji YANG Nian-sheng YANG Xiao YU Xue-qing 《园艺学报》2003,19(6):782-785
AIM:To detect the association between the polymorphism of Fc receptor γ chain gene at position-29 in promoter and systemic lupus erythematosus(SLE).METHODS:The genotypes at position -29 in promoter of Fc receptor γ chain gene were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method in 180 patients with SLE and 140 ethnically matched controls in southern China.RESULTS:The frequencies of TT genotype(33.3%) and T allele (54.4%) at position -29 in patients with SLE were significantly higher than those in controls (17.2% and 42.9%, respectively), whereas, the frequencies of GG genotype (24.4%) and G allele (45.6%) in patients with SLE were remarkably lower than those in controls (31.4% and 57.1%, respectively) (P<0.05). The TT genotype and T allele at position -29 were not associated with lupus nephritis in SLE patients (P>0.05).CONCLUSION:Our results indicate that the T allele at position -29 in promoter of Fc receptor gene probably contributes to the susceptibility to SLE, but does not play a role in the occurrence of lupus nephritis. 相似文献
85.
JIANG An-li KANG Lu-dong ZHAO Chun-hua BI Wen-xiang HU Xiao-yan KONG Feng XU Song-de 《园艺学报》2003,19(1):55-58
AIM: In order to evaluate the applicable value of LDL as a targeted vehicle for chemotherapeutic agents, we investigated and compared the inhibitory effects of LDL-ACM complex and free ACM on nude mice's subcutaneous implanted tumors derived from gastric cancer cell lines, SGC-7901 and NKM-45. METHODS: LDL-ACM complex was prepared and the tumor model of nude mice was established by subcutaneous implantation of SGC-7901 and NKM-45. Then, the groups of nude mice developed subcutaneous implanted tumors were received either LDL-ACM complex or free ACM. Subsequently, the tumor size, weight and leukemia cell counts were measured and the rates of tumor-inhibition and the survival were compared among the groups. RESULTS: The inhibitory effects of LDL-ACM complex on the tumors, especially on SGC-7901 implanted tumors were much more obvious than that of free ACM. It was also indicated that the action of LDL-ACM complex was mediated by LDL receptor. CONCLUSION: These results showed that LDL-ACM complex had significant inhibitory effects on the implanted tumors and the effect might be mediated by LDL receptor. 相似文献
86.
AIM:To investigate the expression of soluble guanylate cyclase protein and its mRNA in rat pulmonary artery after exposure to hypoxia and hypercapnia.METHODS:Male Sprague-Dawley rats were randomly split into 4 group, which were hypoxic hypercapnic (HH 1 week, HH 2 weeks, HH 4 weeks) group and control group, to copy pulmonary hypertensive animal model. The expression of sGCα1 and β1 subunits protein of medial and small pulmonary artery was performed by immunohistochemistry with a polycolonal antibody. In situ hybridization was performed on the rat lung tissue using sGC oligonuclear probe to assay the expression of sGCα1subunit mRNA.RESULTS:The sGCα1 and β1 subunits protein and sGCα1 subunit mRNA were faint staining in the pulmonary small and medium artery in HH1 week, HH 2 weeks and HH 4 weeks groups compared with control group (all P<0.01).CONCLUSION:sGC subunit mRNA and protein expression in pulmonary small and medium artery were decreased after exposure to hypoxia and hypercapnia, which took part in the development of the pulmonary hypertension. 相似文献
87.
88.
89.
90.
AIM:To explore the changes of L-selectin expression on peripheral blood polymorphonuclear leukocytes (PMNs) and their significance in rats with acute lung injury (ALI). METHODS:ALI model in rat was established by intravonous injection of E. coli endotoxin (ET). The expression of L-selectin on peripheral blood PMNs was measured by immunofluorescence and flow cytometry.RESULTS:The contribution of L-selectin fluorescence signal was on the surface of PMNs membrane. The expression of L-selectin on poeripheral blood PMN was significantly lower at 5 min after injection of ET and the lowest during 15 min to 30 min, then gradually increased, but the expression of L-selectin on PMN was lower at 60 min after injection of ET than that of control animal.CONCLUSION:In physiological state, L-selectin were expressed on the surface of PMN membrane. The protein expression of L-selectin on PMNs reduced rapidly after injection of ET and the lowest at 15 min, then gradually increased. L-selectin may play a role in the development of ALI. 相似文献