首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   17593篇
  免费   1083篇
  国内免费   1661篇
林业   1242篇
农学   829篇
基础科学   690篇
  1857篇
综合类   9091篇
农作物   1377篇
水产渔业   851篇
畜牧兽医   2319篇
园艺   1343篇
植物保护   738篇
  2024年   143篇
  2023年   389篇
  2022年   767篇
  2021年   782篇
  2020年   698篇
  2019年   690篇
  2018年   570篇
  2017年   840篇
  2016年   587篇
  2015年   836篇
  2014年   878篇
  2013年   1070篇
  2012年   1564篇
  2011年   1580篇
  2010年   1497篇
  2009年   1253篇
  2008年   1338篇
  2007年   1177篇
  2006年   1000篇
  2005年   814篇
  2004年   470篇
  2003年   327篇
  2002年   314篇
  2001年   299篇
  2000年   258篇
  1999年   89篇
  1998年   17篇
  1997年   15篇
  1996年   6篇
  1995年   6篇
  1994年   5篇
  1993年   5篇
  1992年   7篇
  1991年   4篇
  1990年   10篇
  1989年   3篇
  1987年   6篇
  1986年   2篇
  1985年   1篇
  1981年   5篇
  1965年   1篇
  1962年   5篇
  1956年   5篇
  1955年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
AIM:To investigate the effects of p21-activated kinase 6 (PAK6) on the invasive and migratory abilities of human non-small-cell lung cancer A549 cells. METHODS:The expression of PAK6 mRNA in A549 cells, human bronchial epithelial (HBE) cells, non-small-cell lung cancer tissues and paired adjacent non-tumor tissues was measured by real-time PCR. After A549 cells were transfected with siRNA-PAK6 (siPAK6) or negative control (NC) for 48 h, the expression of PAK6 at mRNA and protein levels was measured by real-time PCR and Western blotting, respectively. The invasion and migration of A549 cells were detected by Matrigel invasion assay and Transwell migration assay. The cytoskeletal changes were observed with FITC-phalloidin staining under confocal microscope. RESULTS:The level of PAK6 mRNA in A549 cells was higher than that in HBE cells (3.50±1.16 vs 1.12±0.42, P<0.05). The level of PAK6 mRNA in non-small-cell lung cancer tissues was higher than that in paired adjacent non-tumor tissues (5.13±1.33 vs 1.08±0.37, P<0.05). The expression of PAK6 protein decreased by 72% in A549 cells transfected with siPAK6 (P<0.05), and the level of PAK6 mRNA significantly decreased in A549 cells transfected with siPAK6 (3.72±0.75 vs 0.69±0.21, P<0.05). Matrigel invasion assay and Transwell migration assay demonstrated that knockdown of PAK6 markedly attenuated the invasion and migration of A549 cells (P<0.05). The cytoskeletal actin remodeling and reduction of stress fibers in A549 cells transfected with siPAK6 were observed under confocal microscope. CONCLUSION:PAK6 may affect the invasive and migratory abilities of non-small-cell lung cancer cells by cytoskeletal actin remodeling.  相似文献   
952.
选取3年生"蓝丰"、"北陆"、"美登"蓝莓品种为试验材料,采用石蜡切片法和"指甲油法"观察了3个蓝莓品种叶片解剖结构和气孔特性。结果表明:3个品种的叶片的角质层、表皮细胞、栅栏组织、海绵组织等组织厚度都存在着差异,其中"蓝丰"的角质层、表皮、栅栏组织、海绵组织厚度最大,"北陆"次之,"美登"最小;从叶片组织紧密度来看,"美登"的最大,"北陆"次之,"蓝丰"最小;栅海比参数比较中,"北陆"最大,"美登"次之,"蓝丰"最小;从蓝莓叶片气孔特性来看,"蓝丰"气孔长度和宽度最大,"北陆"次之,"美登"最小,而气孔的密度呈现相反的结果。  相似文献   
953.
为筛选出防治辣椒疫病的高效低毒新药剂,以遵辣6号为供试品种,选择68.75%银法利、58%甲霜灵猛锌、69%烯酰吗啉·锰锌、72%霜霉疫净及70%安泰生5种药剂进行防效试验,并对施药后辣椒的农艺性状和产量进行调查。结果表明,68.75%银法利、58%甲霜灵锰锌、69%烯酰吗啉·锰锌、72%霜霉疫净及70%安泰生对辣椒疫病的防治效果分别为80.12%、73.2%、59.84%、40.05%和19.88%,用药后辣椒产量分别比对照增产18.39%、15.33%、13.8%、8.05%和6.51%。这5种药剂的综合表现依次为68.75%银法利58%甲霜灵锰锌69%烯酰吗啉·锰锌72%霜霉疫净70%安泰生。  相似文献   
954.
‘赣猕6号’系从野生毛花猕猴桃(Actinidia eriantha)自然变异群体中选育而成的新品种。果实长圆柱形,果面密被白色短茸毛。果实中大,平均单果质量72.5 g,最大单果质量96 g。果肉墨绿,可溶性固形物含量13.6%,可滴定酸含量0.87%,干物质含量为17.3%。维生素C含量7.23 mg·g-1。果实成熟期为10月下旬。果实后熟达食用状态时易剥皮,肉质细嫩清香,风味酸甜适度。  相似文献   
955.
AIM: To investigate the effects of transplantation of bone marrow mesenchymal stem cells (BMSCs) modified by bcl-2 gene on myocardial cell apoptosis, angiogenesis and cardiac function in the rabbit after acute myocardial infarction (MI).METHODS: The rabbit BMSCs were isolated, cultured and purified in vitro. The BMSCs were transfected with adenovirus or adenovirus-Bcl-2. The rabbit model of MI was established by ligation of left anterior descending branch. The rabbits were injected with Ad-Bcl-2-BMSCs (MI+Bcl-2-BMSCs group), Ad-BMSCs (MI+BMSCs group) and DMEM (MI group) in infarction marginal zone 2 weeks after ligation. The cardiac function was evaluated by echocardiography.The apoptosis of myocardial cells was measured by TUNEL. The mRNA expression of VEGF was detected by real-time PCR. The expression of CD31 was examined by immunohistochemical staining, and new blood capillaries were counted at 4 weeks after BMSCs transplantation. The correlation of the above values with cardiac function was analyzed.RESULTS: The cardiac function was better, the apoptotic rate was lower, the mRNA expression of VEGF and the capillary density were higher in both MI+Bcl-2-BMSCs group and the MI+BMSCs group than those in MI group, and those in MI+Bcl-2-BMSCs group increased more obviously.The left ventricular ejection fraction (LVEF) had a negative correlation with the myocardial cell apoptosis rate. A positive correlation with the mRNA expression level of VEGF and the capillary density was also observed.CONCLUSION: The transplantation of BMSCs modified by bcl-2 gene significantly reduces the myocardial cell apoptosis, promotes angiogenesis, improves heart function of the rabbits with MI.  相似文献   
956.
研究了银川市兴庆区掌政乡不同种植年限的节能日光温室土壤养分状况,以期对银川市节能日光温室土壤养分的合理管理提出理论依据.结果表明:银川市日光温室土壤磷、钾肥超标而氮肥不足,化肥施用氮、磷、钾比例失调.建议采取限制磷、钾化肥用量、改进施肥技术等措施.  相似文献   
957.
云南不同花魔芋品种性状相关分析   总被引:2,自引:1,他引:2  
对云南不同生态区域种植的魔花15、楚雄花魔芋2号、丽江花白魔芋、会泽花魔芋、大关花魔芋和富源花魔芋(CK)6个云南花魔芋地方品种的主要性状进行了相关性和聚类分析。分析结果表明,花魔芋种芋大小、干物质含量、球茎高等对球茎质量影响较大;干物质含量、球茎直径、球茎高等与葡甘露聚糖含量呈显著性相关;球茎质量、葡甘露聚糖、球茎直径等与干物质含量呈显著相关。云南花魔芋品种可聚为3个类群,富源花魔芋、会泽花魔芋、大关花魔芋和魔花15分布在第1个类群里,丽江花白魔芋、楚雄花魔芋2号分别聚成另外2个类群。  相似文献   
958.
温度和光照对金边瑞香花芽分化的影响   总被引:5,自引:0,他引:5  
研究了温度和光照对金边瑞香花芽分化的影响,温度是影响金边瑞香花芽分化的主要因子,20 ~ 25 ℃金边瑞香植株可以完成花芽分化的各个过程,10 ~ 18 ℃植株一直处于营养生长状态而未进行花芽分化。金边瑞香花芽分化对光周期不敏感,但散射光比直射光更有利于其花芽分化。  相似文献   
959.
以野生蝉花菌种为试材,采用液体培养法,研究了碳源、氮源、微量营养和pH对野生蝉花菌种生长的影响,以期为标准化、规模化、产业化人工栽培蝉花提供优质种源。结果表明:将野生蝉花菌株接种到液体培养基中,在19℃,转速120r·min-1恒温振荡摇床内培养,蝉花菌种的最适液体培养基组分为可溶性淀粉20g,奶粉10g,磷酸二氢钾0.5g,硫酸镁1g,维生素B1210片,水1 000mL,最适pH 5.0~6.0。  相似文献   
960.
AIM: To explore the expression and significance of fibrinogen-like protein 2 prothrombinase/fibroleukin (fgl2) in a model of rat coronary microthrombosis. METHODS: Seventy-eight Sprague-Dawley male rats were randomly assigned to model group (n=36), sham operation group (n=36) for different time (1 h, 1 d, 1week, 2 weeks, 3 weeks, 4 weeks)(n=6, respectively), and normal control group (n=6). After closing aorta, sodium laurate was injected into aortic root of the animals in model group. The animals in sham operation group were injected with normal saline for control. Microthromb were detected with HE staining and modified martius-sarlet-blue stains (MMSB). von Willebrand factor (vWF) was measured with ELISA. fgl2 mRNA and protein expressions were detected by RT-PCR and immunohistochemistry staining, respectively. RESULTS: Microthromb were observed in rat coronary microvasculature. vWF was increased in plasma. fgl2 was induced in model group compared to sham operation group (P<0.05), no significant changes were observed in sham operation group and normal control group (P>0.05). CONCLUSION: The functional disorder of endothelial cells induces the expression of fgl2 in the coronary microvasculature. fgl2 prompts the thrombosis with platelet and fibrin.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号