全文获取类型
收费全文 | 28186篇 |
免费 | 1582篇 |
国内免费 | 2785篇 |
专业分类
林业 | 2365篇 |
农学 | 2898篇 |
基础科学 | 1882篇 |
3589篇 | |
综合类 | 11339篇 |
农作物 | 1778篇 |
水产渔业 | 1174篇 |
畜牧兽医 | 4186篇 |
园艺 | 1795篇 |
植物保护 | 1547篇 |
出版年
2024年 | 160篇 |
2023年 | 475篇 |
2022年 | 1191篇 |
2021年 | 1367篇 |
2020年 | 1201篇 |
2019年 | 1168篇 |
2018年 | 860篇 |
2017年 | 1264篇 |
2016年 | 1004篇 |
2015年 | 1342篇 |
2014年 | 1515篇 |
2013年 | 1751篇 |
2012年 | 2237篇 |
2011年 | 2335篇 |
2010年 | 2131篇 |
2009年 | 1888篇 |
2008年 | 1808篇 |
2007年 | 1595篇 |
2006年 | 1347篇 |
2005年 | 1109篇 |
2004年 | 616篇 |
2003年 | 539篇 |
2002年 | 601篇 |
2001年 | 503篇 |
2000年 | 476篇 |
1999年 | 335篇 |
1998年 | 260篇 |
1997年 | 207篇 |
1996年 | 201篇 |
1995年 | 166篇 |
1994年 | 174篇 |
1993年 | 131篇 |
1992年 | 137篇 |
1991年 | 92篇 |
1990年 | 103篇 |
1989年 | 78篇 |
1988年 | 60篇 |
1987年 | 30篇 |
1986年 | 21篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 17篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1962年 | 3篇 |
1956年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
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
83.
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
84.
AIM:To investigate therapeutic effects of recombinant human growth hormone(rhGH) on rat sepsis and its possible mechanisms.METHODS:Mean arterial pressure (MAP), levels of plasma TNFα, IL-1β and endotoxin, leukocyte count and survival rate within 1 week were determined after E. coli injection among control group, sepsis group and sepsis+rhGH group.RESULTS:(1)rhGH diminished the decrease of MAP, reduced plasma endotoxin and TNFα levels and increased neutrophil ratio in total leukocytes in sepsis rat. rhGH increased survival rate within 1 week on sepsis rat. (2)No changes were found in IL-1β level among the three groups.CONCLUSION:rhGH showed desirable beneficial effects on rat sepsis, which may attribute to: improving circulatory function;maintaining intestinal mucosa barrier, attenuating bacteria/endotoxin translocation and inhibiting the production and release of TNFα. 相似文献
85.
AIM:To investigate the effects of fibronectin (FN) on the proliferation and collagen synthesis in cultured rat cardiac fibroblasts (CFb) derived from SHR (CFbSHR) and WKY (CFbWKY). METHODS:CFb derived from 12-week-old spontaneously hypertensive rat (SHR) and WKY was cultured by outgrowth of tissue block. Cell proliferation of CFb was measured by cell number counting and[3H]-TdR incorporation using 24-well plates pre-coated with 5 μg/cm2 of FN. Collagen synthesis was determined by [3H]-proline incorporation. RESULTS:As compared with control, the cell number of fibroblasts derived from SHR and WKY were significantly increased to 163.75% and 170.42% respectively after 72 h incubation with FN in the presence of 0.4% FCS from a intial cell density of 1×104 cells/mL. DNA synthesis of CFb was markedly promoted by FN. FN induced an increased in [3H]-proline incorporation in both CFbSHR and CFbWKY. CONCLUSION:FN is able to promote cell proliferation and collagen synthesis of CFb derived both from SHR and WKY. 相似文献
86.
十种常用农药与球孢白僵菌的生物学相容性 总被引:24,自引:2,他引:24
球孢白僵菌孢子粉与10种常用农药相容性的测定结果显示,随着孢子浓度上升,所试农药对孢子的抑制作用均有不同程度的增强。在1/10田间常规使用浓度下,百菌清和代森锰锌均能抑制或杀死孢子(萌发率<1%)。除阿维菌素外,所有杀虫剂均与白僵菌孢子相容,在常规使用浓度的10倍稀释液中孢子萌发率达90%以上。吡虫啉、蚜虱灵、灭多威和氟虫腈与孢子的相容性最好,其中吡虫啉和蚜虱灵对孢子萌发率的影响不明显随药剂浓度的变化而变化,即使在田间常规使用浓度下孢子萌发率也在95%以上,而阿维菌素与白僵菌的相容性极差。因此,应用白僵菌制剂防治害虫,选择生物学相容性好的农药以低剂量与白僵菌制剂混用,既可使菌剂增效,又可大幅度降低化学药剂用量。 相似文献
87.
88.
89.
90.