全文获取类型
收费全文 | 18791篇 |
免费 | 1117篇 |
国内免费 | 1606篇 |
专业分类
林业 | 1231篇 |
农学 | 1660篇 |
基础科学 | 160篇 |
1972篇 | |
综合类 | 6347篇 |
农作物 | 1381篇 |
水产渔业 | 689篇 |
畜牧兽医 | 4171篇 |
园艺 | 2789篇 |
植物保护 | 1114篇 |
出版年
2024年 | 53篇 |
2023年 | 242篇 |
2022年 | 516篇 |
2021年 | 648篇 |
2020年 | 691篇 |
2019年 | 825篇 |
2018年 | 625篇 |
2017年 | 804篇 |
2016年 | 1080篇 |
2015年 | 1003篇 |
2014年 | 1062篇 |
2013年 | 1147篇 |
2012年 | 1537篇 |
2011年 | 1506篇 |
2010年 | 1204篇 |
2009年 | 1176篇 |
2008年 | 1079篇 |
2007年 | 1215篇 |
2006年 | 900篇 |
2005年 | 826篇 |
2004年 | 604篇 |
2003年 | 478篇 |
2002年 | 328篇 |
2001年 | 282篇 |
2000年 | 284篇 |
1999年 | 217篇 |
1998年 | 183篇 |
1997年 | 147篇 |
1996年 | 144篇 |
1995年 | 114篇 |
1994年 | 93篇 |
1993年 | 84篇 |
1992年 | 72篇 |
1991年 | 54篇 |
1990年 | 45篇 |
1989年 | 55篇 |
1988年 | 35篇 |
1987年 | 27篇 |
1986年 | 24篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 19篇 |
1980年 | 8篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1962年 | 6篇 |
1956年 | 12篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
51.
52.
53.
中晚熟杂交一代辣椒镇研3号是以江苏本地羊角椒自交系Y9007为母本,由甘肃酒泉引进的甜椒自交系T9218为父本配制的一代杂交组合。镇研3号为中熟辣椒品种,果形为牛角形,纵径15cm,肩横径5.0cm、肉厚0.40cm,单果平均重42g。果面光滑,青熟果绿色、味微辣,风味佳,适宜在长江流域或南方保护地栽培种植,667m2产量约为4200~5000kg。 相似文献
54.
55.
56.
57.
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
58.
59.
AIM: To study whether Sca-1+ cells from fetal liver can be induced to differentiate into neuronal cells in vitro. METHODS:Sca-1+cells from 14 5-days-old murine fetal liver were isolated with a magnetic cell sorting kit, and were cultured in Dulbecco s modif ied Eagle s medium(DMEM)/F12 supplemented with 10%fetal bovine serum(FBS), and passaged at a rat io of 1 3 when cells reached more than 80%confluence.The 5 passage cells were induced by 10-3mol/Lβ-mercaptoethanol(β-ME)and 5×10-7 mol/L all-trans-retinoic acid(RA)for 24 hours, and then incubated in serum-free medium for 5 hours to 5 days.The characteristics of treated cel s were assayed by immunocytochemistry staining analysis at 5 hours, or 5 days.RESULTS: Cells treated with β-ME and RA exhibited neuronal phenotype and expressed neuron-specific protein such as neuron-specific nuclear protein (NeuN), neuronfilament-M, and neuron-specific tubulin-1 (TuJ-1) but not tau, MAP-2, or the astrocyte-specific marker glial fibrillary acidic protein (GFAP).CONCLUSION: Sca-1+ cells from fetal liver, of which most are regarded as hematopoietic stem cells, could differentiate into early immature neuronal cells in vitro. These findings suggest that Sca-1+ cells from fetal liver may be an alternative source in cell therapy and gene therapy of neural dysfunction. 相似文献
60.
AIM:To explore transdifferentiation potential of Sca-1+ cells from murine fetal liver. METHODS:2×103 of Sca-1+ cells from male murine fetal liver were transfused into female mouse irradiated lethally with γ ray from 60 Co source (10 Gy) via tail vein. Two months later, FISH and immunohistochemistry were used to detect the situation for transdifferentiating of the donor cells (male cells) in tissues of female recipient mouse. RESULTS:The renal tubular epitheliocyte-like and neurocyte-like cells with Y chromosome were found on the sections of renal and brain tissues from female recipient mice. These cells have phenotype characteristics of RCA+/CD45-F4/80- and NueN+/CD45-F4/80-, respectively. CONCLUSION:The evidence is provided for Sca-1+ cells from murine fetal liver to transdifferentiate into both renal and brain tissue cells. 相似文献