全文获取类型
收费全文 | 40422篇 |
免费 | 2306篇 |
国内免费 | 3808篇 |
专业分类
林业 | 3759篇 |
农学 | 3750篇 |
基础科学 | 2180篇 |
4347篇 | |
综合类 | 17467篇 |
农作物 | 2834篇 |
水产渔业 | 1590篇 |
畜牧兽医 | 6074篇 |
园艺 | 2638篇 |
植物保护 | 1897篇 |
出版年
2024年 | 204篇 |
2023年 | 646篇 |
2022年 | 1575篇 |
2021年 | 1737篇 |
2020年 | 1616篇 |
2019年 | 1697篇 |
2018年 | 1134篇 |
2017年 | 1721篇 |
2016年 | 1374篇 |
2015年 | 1982篇 |
2014年 | 2075篇 |
2013年 | 2416篇 |
2012年 | 3346篇 |
2011年 | 3398篇 |
2010年 | 3337篇 |
2009年 | 3011篇 |
2008年 | 2784篇 |
2007年 | 2518篇 |
2006年 | 2140篇 |
2005年 | 1669篇 |
2004年 | 963篇 |
2003年 | 744篇 |
2002年 | 852篇 |
2001年 | 743篇 |
2000年 | 644篇 |
1999年 | 453篇 |
1998年 | 277篇 |
1997年 | 263篇 |
1996年 | 203篇 |
1995年 | 180篇 |
1994年 | 155篇 |
1993年 | 140篇 |
1992年 | 120篇 |
1991年 | 120篇 |
1990年 | 67篇 |
1989年 | 62篇 |
1988年 | 52篇 |
1987年 | 33篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1979年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1962年 | 6篇 |
1956年 | 15篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
ZHANG Li-rong XIANG Peng XIA Wen-jie CHEN Zhen-guang ZHANG Xiu-ming LI Yan LI Shu-nong 《园艺学报》2002,18(8):896-899
AIM: To investigate the effects of PD98059 on the differentiation from mesenchymal stem cells to osteoblasts.METHODS: hMSC were separated from human marrow and expanded in cuture medium. hMSC were induced with dexamethasone, β-glycerophosphate, vitamin C which acted as osteoblast differentiation inducer. PD98059 was added into the osteoblasts induction medium. The cells were assayed with cell morphology, alkaline phosphatase (AP) activity and calcium deposition. RESULTS: The isolated cultured MSC comprised a single phenotypic population and displayed a fibroblast-like morphology. After induced with osteoblasts induction medium, the cells showed changes in cell morphology from spindle-shape to cuboidal and polygonal. The AP activity increased gradually and reached the peak in 12 days, then decreased. Many scattered tangerice calcium nodes were observed. PD 98059 significantly inhibited AP activity and calcium deposition in a dose-dependent manner. A striking observation of the present study was that a few adipocytes appeared in cultures that were treated with PD 98059 and osteogenic differentiation medium. CONCLUSION: These results indicated that osteogenic diferentiation from the hMSCs was related to the activation of the ERK. 相似文献
122.
AIM: To study the electrophysiological characteristics of ion channels of stem cell derived cardiomyocytes(SCDC) of mouse. METHODS: Embryonic stem cells of D3 line(ES-D3) were cultured on the MEF feeder layer with BRL conditioned medium, and fetal mouse heart cells(FMHC)were cultured in vitro. Then ES-D3 cells were induced to differentiate into many kinds of cells. SCDC were harvested on day 12 after differentiation initiating and identified by electro-microscope and immunocytochemistry. SCDC and FMHC were prepared for the patch-clamp research. Sodium and calcium currents together were elicited and compared between SCDC and FMHC. RESULTS: The current characteristics of sodium and calcium channels of SCDC were very similar to FMHC. CONCLUSION: The functional expression of ion channels occurred during ES-D3 cells differentiation and the electrophysiological characteristics of sodium and calcium channels of SCDC are very similar to FMHC. 相似文献
123.
LIN Jun SUN Jie ZHOU Yan HUANG Xing XIONG Ping WANG Ya-ping DENG Chang-sheng 《园艺学报》2002,18(9):1112-114
AIM: To probe into the genetic susceptibility of HLA-DRB1 alleles to esophageal neoplasm in Hubei Han Chinese. METHODS: HLA-DRB1 gene polymorphism in 42 patients with esophageal neoplasm and 136 normal control subjects was studied by PCR and sequence. RESULTS: Allele frequency of HLA-DRB1 *0901 allele was significantly higher in esophageal cancer patients than those in normal controls(0.2500 vs 0.1397, P =0.028; the odds ratiO2.053; etiologic fraction 0.1282).There were no association between the rested HLA-DRB1 alleles with patients. CONCLUSION: Individuals carrying HLA-DRB1 *0901 may be susceptible to esophagealo carcinoma, its nucleotide sepuence approachs to the corresponded allele sequence(exoN2)published in GenBank. 相似文献
124.
125.
126.
127.
128.
研究了两种β-环糊精的衍生物甲基-β-环糊精(MCD)和羟丙基-β-环糊精(HPCD)对甲基对硫磷的增溶作用和对紫外光降解的影响。结果表明:MCD和HPCD能增强甲基对硫磷的水溶性,在25℃下,20 g/L的MCD和HPCD溶液中,甲基对硫磷溶解度比在纯水中分别提高了21.91和17.92倍;另外,3 g/L、6 g/L MCD和HPCD分别处理的甲基对硫磷,其光降解速率分别加快了4.87~6.85倍。增溶作用和光敏效应主要是由于MCD和HPCD与甲基对硫磷形成包合物引起的。 相似文献
129.
热胁迫对辣椒花柱细胞中Ca2+ 分布的影响 总被引:5,自引:0,他引:5
用焦锑酸钾沉淀法研究了热胁迫对辣椒开花前后柱头和花柱细胞中Ca2+分布的影响。结果表明: 常温下Ca2+ 分布在柱头细胞表面、花柱引导组织细胞间隙等质外体系统中, 且在花粉管上呈先增加后减少的规律性变化; 热胁迫后, 除细胞间隙等质外体系统外, 细胞质和细胞核中也出现Ca2+, 花柱引导组织中通过的花粉管发生扭曲、变形, 这可能与Ca2+ 的异常分布有关。 相似文献
130.
大豆疫病的种子处理技术研究 总被引:2,自引:0,他引:2
本试验用不同浓度的瑞毒锰锌、杀毒矾和克露进行大豆种子处理试验,结果表明,500ppm瑞毒锰锌对大豆疫病具有很好的治疗作用,而用杀毒矾以种子重量0.4—0.5%的剂量闷种,能显著地抑制大豆疫霉菌的侵入 相似文献