全文获取类型
收费全文 | 11082篇 |
免费 | 646篇 |
国内免费 | 1007篇 |
专业分类
林业 | 888篇 |
农学 | 507篇 |
基础科学 | 538篇 |
1199篇 | |
综合类 | 5375篇 |
农作物 | 852篇 |
水产渔业 | 591篇 |
畜牧兽医 | 1465篇 |
园艺 | 875篇 |
植物保护 | 445篇 |
出版年
2024年 | 83篇 |
2023年 | 231篇 |
2022年 | 501篇 |
2021年 | 466篇 |
2020年 | 439篇 |
2019年 | 457篇 |
2018年 | 282篇 |
2017年 | 508篇 |
2016年 | 344篇 |
2015年 | 459篇 |
2014年 | 526篇 |
2013年 | 675篇 |
2012年 | 944篇 |
2011年 | 981篇 |
2010年 | 946篇 |
2009年 | 843篇 |
2008年 | 859篇 |
2007年 | 803篇 |
2006年 | 618篇 |
2005年 | 549篇 |
2004年 | 337篇 |
2003年 | 191篇 |
2002年 | 220篇 |
2001年 | 170篇 |
2000年 | 184篇 |
1999年 | 51篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1987年 | 2篇 |
1981年 | 2篇 |
1962年 | 2篇 |
1956年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
为探究烤烟油菜轮作及平衡施肥对土壤有机碳(SOC)含量的影响,通过田间小区试验,采用双因素裂区设计,测定烤烟与3个油菜品种(‘重蓉油1号’、‘德油早1号’和‘GSX-1’)轮作以及平衡施肥(减氮和增磷)下油菜季与烤烟季土壤的总有机碳(TOC)和可溶性有机碳(DOC)含量。结果表明,从油菜移栽初期到收获,SOC含量均有不同程度的上升,上升幅度为7.7%~166.49%;轮作处理的TOC含量和DOC含量相较对照有所增加,且收获期(180天)的TOC含量和DOC含量以‘重蓉油1号’最高,分别为对照处理的1.26和4.78倍。在烤烟整个生育期内,除个别处理外,其他土壤DOC含量呈下降趋势,TOC含量有所增加。此外,就施肥模式而言,减氮处理效果最佳。在烤烟收获期,除‘德油早1号’外,土壤TOC含量均以减氮处理最高,分别为常规施肥处理的1.20、1.44和1.02倍。综上‘,重蓉油1号’油菜与烤烟轮作、减施氮肥时SOC含量较高,是当地较优的种植模式。 相似文献
62.
为做好重庆重要特色经济作物茎瘤芥的产量预报,本研究耦合光、温、水与茎瘤芥产量形成的供需关系,以预报日前不同生育期气象资料作为参考数据集,基于气候适宜度指数与气象产量指数,建立茎瘤芥产量动态预报模型。结果表明:茎瘤芥幼苗—瘤茎膨大期气候适宜指数与气象产量指数相关性优于仅考虑瘤茎膨大期的分析结果。采取幼苗—瘤茎膨大期以及仅瘤茎膨大期两类参考数据集建立茎瘤芥瘤茎产量丰歉动态预报模型,幼苗—瘤茎膨大期作为参考数据集的计算模型表现更佳,不同起报时间瘤茎产量预报准确率平均值92.0%;归一化均方根误差平均值0.196;丰歉趋势准确率平均值68.2%。说明幼苗期气象条件对茎瘤芥瘤茎产量形成有一定贡献,考虑幼苗期气象要素的气候适宜指数能够更好地解释气象条件对茎瘤芥产量形成的影响。利用2017—2019年气象数据和产量数据对产量丰歉预报模型进行检验,各年度产量预报准确率基本在90%以上。基于气候适宜度指数的茎瘤芥产量动态预报方法能够以较高准确性和稳定性对茎瘤芥产量进行预测。 相似文献
63.
64.
AIM: To study the expression and its kinetics of rice phenylalanine ammonia-lyase gene encoding into E. coli as the basis of treatment for phenylketouria. METHODS: The phenylalanine ammonia-lyase-1-cDNA(rPAL-1-cDNA) from rice was recombined into E. coli high expression vector pET-28c and transformed into E. coli host strain BL21DE3. Engineering bacteria was then inducted by isopropyl-β-D-thiogalactoside (IPTG) for 1, 3, 5, 7 hours, in order to obtain high level expression. RESULTS: After induction, the expression level of fusion protein was 21.40%, 30.60%, 35.40%, 35.43% respectively. The fusion protein exhibited a band of 78.6 kD on SDS-PAGE analysis, but was not found in controls.The target protein was mainly existed in the form of inclusion body. CONCLUSION:Rice PAL gene expressing E. coli was established by gentic engineering technique. 相似文献
65.
AIM: To observe the effect of high temperature on the delayed rectifier K+ channel(IK) in hypothalamus neurons METHODS: The kinetic properties of I K were measured by cell-attached mode of patche-clamp technique RESULTS: The conductance, long-term open constant(τ o2) and open probability(Po) of IK increased with increase of temperature (P <0.05), while more burst open and multi-order open were recorded Many types of currents occurred after heat stress at 43℃,and voltage-dependent property reduced and even depressed CONCLUSIONS: The activating action of IK might be affected obviously by high temperature, the coupling between I K and body fever or heatstroke remained to be established. 相似文献
66.
AIM To investigate the mechanism of long noncoding RNA (lncRNA) FEZF1-AS1 regulating microRNA-363-3p (miR-363-3p) on the viability and apoptosis of lipopolysaocharide (LPS)-induced vascular endothelial cells. METHODS Human umbilical vein endothelial cells (HUVECs) were cultured in vitro . pcDNA-NC, pcDNA-FEZF1-AS1, anti-miR-NC, anti-miR-363-3p, miR-NC and miR-363-3p mimics were transfected into the HUVECs and LPS stimulation was applied for 24 h. RT-qPCR was used to detect the expression of FEZF1-AS1 and miR-363-3p. The cell viability was measured by MTT assay. The apoptotic rate was analyzed by flow cytometry. The dual-luciferase reporter experiment was used to verify the targeted regulation of FEZF1-AS1 and miR-363-3p. Western blot was used to determined the expression of cyclin D1, Ki67 and cleaved caspase-3. RESULTS Compared with control group, the expression level of FEZF1-AS1 in LPS group was significantly reduced (P <0.05), and the expression level of miR-363-3p was significantly increased (P <0.05). Compared with pcDNA-NC+LPS group, the cell viability in pcDNA-FEZF1-AS1+LPS group was significantly increased (P <0.05), the apoptotic rate was significantly reduced (P <0.05), the protein levels of cyclin D1 and Ki67 were significantly increased (P <0.05), and the protein level of cleaved caspase-3 was significantly reduced (P <0.05). Compared with anti-miR-NC+LPS group, the cell viability in anti-miR-363-3p+LPS group was significantly increased (P <0.05), the apoptotic rate was significantly reduced (P <0.05), the protein levels of cyclin D1 and Ki67 were significantly increased (P <0.05), and the protein level of cleaved caspase-3 was significantly reduced (P <0.05). Dual-luciferase reporter experiment confirmed that FEZF1-AS1 targeted miR-363-3p. Compared with miR-NC+pcDNA-FEZF1-AS1+LPS group, the cell viability in miR-363-3p+pcDNA-FEZF1-AS1+LPS group was significantly reduced (P <0.05), the apoptotic rate was significantly increased (P <0.05), the protein levels of cyclin D1 and Ki67 were significantly reduced (P <0.05), and the protein level of cleaved caspase-3 was significantly increased (P <0.05). CONCLUSION Over-expression of FEZF1-AS1 promotes the viability and inhibits apoptosis of LPS induced vascular endothelial cells by inhibiting the expression of miR-363-3p. 相似文献
67.
68.
69.
单细胞凝胶电泳检测除虫脲光解产物对小鼠肝脏DNA损伤研究 总被引:1,自引:0,他引:1
采用单细胞凝胶电泳法对不同浓度除虫脲经紫外光照射后的混合物可能导致小鼠肝脏细胞DNA损伤的作用进行了研究,应用CASP软件分析彗星图像,得出彗星尾部DNA百分含量、彗星尾长、尾距和Olive尾距4个指标.通过SPSS软件分析表明,其光降解混合物导致的彗星拖尾现象与空白组有显著区别,且在一定浓度范围呈现剂量-效应关系,表明不同浓度除虫脲经光降解后其混合物具有一定的致突、致癌性,且毒性随着浓度的降低而减小. 相似文献
70.
不同基因型菜心-土壤系统中邻苯二甲酸二(2-乙基己基)酯的分布特征研究 总被引:3,自引:0,他引:3
在邻苯二甲酸二(2-乙基己基)酯(DEHP)不同污染程度的水稻土上盆栽8种不同基因型菜心,应用GC/MS技术,研究DEHP在不同基因型菜心-土壤系统中的累积效应和分布规律。结果表明,不同基因型菜心茎叶和根系对DEHP的吸收累积存在明显差异,其中新选45天油菜心和油青60天菜心茎叶中DEHP的含量相对较高,特青60天菜心和新选油青四九菜心茎叶中DEHP的含量相对较低;亚蔬全年油绿甜菜心、油青60天菜心和四九-19菜心根系中DEHP的含量相对较高。新种油青四九-31菜心和新选油青四九菜心、特青60天菜心根系中DEHP的含量相对较低。各基因型菜心根系中DEHP的含量均高于其茎叶,其含量高低关系较复杂,部分基因型菜心茎叶中DEHP的含量与叶面积大小存在一定的正相关关系,且与污染程度有关。盆栽后新选油青四九菜心和特青60天菜心土壤中DEHP的残留量较高,盆栽佰顺811菜心、亚蔬全年油绿甜菜心、油青60天菜心和新选45天油菜心土壤中DEHP的残留量较低。总体上,油青60天菜心茎叶和根系中DEHP的含量均较高,而土壤中DEHP的残留量较低;新选油青四九菜心茎叶和根系中DEHP的含量均较低。土壤中DEHP的残留量却较高。 相似文献