全文获取类型
收费全文 | 24219篇 |
免费 | 1344篇 |
国内免费 | 2526篇 |
专业分类
林业 | 2568篇 |
农学 | 2609篇 |
基础科学 | 1542篇 |
3381篇 | |
综合类 | 9218篇 |
农作物 | 1558篇 |
水产渔业 | 1088篇 |
畜牧兽医 | 3327篇 |
园艺 | 1361篇 |
植物保护 | 1437篇 |
出版年
2024年 | 78篇 |
2023年 | 365篇 |
2022年 | 891篇 |
2021年 | 1093篇 |
2020年 | 980篇 |
2019年 | 956篇 |
2018年 | 664篇 |
2017年 | 995篇 |
2016年 | 807篇 |
2015年 | 1196篇 |
2014年 | 1201篇 |
2013年 | 1458篇 |
2012年 | 1835篇 |
2011年 | 1898篇 |
2010年 | 1779篇 |
2009年 | 1700篇 |
2008年 | 1536篇 |
2007年 | 1503篇 |
2006年 | 1270篇 |
2005年 | 1052篇 |
2004年 | 625篇 |
2003年 | 455篇 |
2002年 | 464篇 |
2001年 | 467篇 |
2000年 | 426篇 |
1999年 | 414篇 |
1998年 | 296篇 |
1997年 | 270篇 |
1996年 | 224篇 |
1995年 | 181篇 |
1994年 | 169篇 |
1993年 | 178篇 |
1992年 | 152篇 |
1991年 | 126篇 |
1990年 | 105篇 |
1989年 | 89篇 |
1988年 | 57篇 |
1987年 | 34篇 |
1986年 | 28篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 7篇 |
1970年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1956年 | 5篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
81.
XU Rui ZHANG Yun ZHANG Mei GE Zhi-ming CHEN Wen-qiang LI Xiu-chang CAI Heng ZHU Hui 《园艺学报》2003,19(5):642-644
AIM:To elucidate the relationship between the intracellular calcium concentration changes and left ventricular hypertrophy and function in the spontaneously hypertensive rats (SHR).METHODS:Intracellular free calcium concentrations were measured by Fura 2 methodology and left ventricular function quantitated by cardiac catheterization in 20 SHR aged 10, 22, and 34 weeks and 20 age-matched Wistar-kyoto (WKY) rats.RESULTS:(1) The systolic blood pressure(SBP), intracellular calcium concentrations and left ventricular mass / body weight index (LVM/BW) were significantly higher in all three age groups of SHR than the corresponding groups of WKY; (2) Compared with age-matched WKY groups, the peak left ventricular pressure descending rate(-dp/dtmax) decreased while left ventricular relaxation time constant (τ)increased significantly in SHR aged 22 and 34 weeks. The peak left ventricular pressure ascending rate(dp/dtmax) and the left ventricular contractility index were significantly increased only in the 34 weeks SHR; (3) Intracellular calcium concentrations showed a positive correlation with LVM/BW,SBP,-dp/dtmax and τ(r=0.47-0.83,P<0.01)and a negative correlation with dp/dtmax and the left ventricular contractility index (r=-0.46,P<0.05 and r=-0.81, P<0.01).CONCLUSION:Intracellular calcium overload is one of the potential mechanisms in the induction of left ventricular hypertrophy as well as of systolic and diastolic dysfunction. 相似文献
82.
AIM:To explore the effect of brain ischemia injury on cell proliferation and nestin expression in cortex and subependymal zone (SEZ).METHODS:Using a local brain ischemia model(MCAO), BrdU positive cells of cortex and subependymal zone (SEZ), also nestin positive cells, were observed by immunohistochemistry.RESULTS:BrdU and nestin positive cells in SEZ of MCAO rats were obviously increased. In cortex, only nestin positive cells were observed.CONCLUSION:Neural stem cells in SEZ and cortex were activated after brain ischemia, it may be related with neural recovery after brain ischemia injury. 相似文献
83.
84.
85.
86.
番石榴果实发育的初步研究 总被引:7,自引:0,他引:7
以东山月拔和二十一世纪这2个品种为试材,研究了番石榴(Psidium guajava L)果实的发育动态规律。结果表明:番石榴的果实发育呈现双“S”型;果实重量和果核重量的发育呈显著的正相关;推测果实发育后期为进行果实产期调控的关键时期;建议以果实发育的直径大小以及果实转蒂下垂作为确定进行产期调控的田间依据。 相似文献
87.
CPPU在柿试管繁殖中的应用 总被引:6,自引:0,他引:6
对CPPU和ZT在柿试管繁殖中的应用价值进行了比较研究,结果表明:CPPU是一种可代替ZT的特效细胞分裂素,添加有CPPU0.2mg/L的MS(1/2N)培养基能促进芽的增殖和生长,且用此培养基继代培养的试管苗生根能力也有所提高。 相似文献
88.
ZHENG Hui LI Hong-yi WANG Zi-neng ZHAO Ying-she YU Li HE Si-cun BAI Zhi-quan ZHOU Zuo-yan YAO Ping WANG Yue-chun 《园艺学报》2002,18(5):553-555
AIM: The purpose of the present study was to explore the relationship between interleukin-6 mRNA expression and endometriosis. METHODS: Using the rat model, IL-6 mRNA expression in the endometrium was examined by RT-PCR. RESULTS: The expression of IL-6 mRNA in control rats did not change at 2, 4, 6 and 8 weeks after sham operation (P>0.05), but in model rats it gradually increased at 2, 4, 6 and 8 weeks after endometriosis (P<0.01). The expression of IL-6 mRNA in uterine endometrium with endometriosis was lower than in endometriotic tissue, but higher than in endometrium from healthy controls. CONCLUSION: The IL-6 mRNA expression may contribute to the development of endometriosis . The increase in IL-6 mRNA expression may promote the implantation and growth of endometriotic tissue. 相似文献
89.
The abnormality of the central noradrenergic system in Alzheimer's disease has two cases: decrease or increase. The former is easy to be understood, because it is resulted from the outstanding forfeit of the noradrenergic neurons in the nucleus locus ceruleus (nLC); but the noradrenalin concentration does not change and enen increase, it seems to disagree with the loss of the noradrenergic neurons in the nLC. This article put emphasis on it, enumerated the related evidence and analyzed the possible causes. At present time, the drugs to increase noradrenalin is used mostly in clinic. This paper summarized it and put forth our own opinions. 相似文献
90.