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   20109篇
  免费   1267篇
  国内免费   3311篇
林业   787篇
农学   3022篇
基础科学   475篇
  1951篇
综合类   8609篇
农作物   4956篇
水产渔业   332篇
畜牧兽医   2441篇
园艺   1640篇
植物保护   474篇
  2024年   146篇
  2023年   404篇
  2022年   585篇
  2021年   702篇
  2020年   694篇
  2019年   781篇
  2018年   708篇
  2017年   743篇
  2016年   1160篇
  2015年   1396篇
  2014年   1528篇
  2013年   1483篇
  2012年   1574篇
  2011年   1390篇
  2010年   1247篇
  2009年   1262篇
  2008年   1130篇
  2007年   1377篇
  2006年   1275篇
  2005年   1030篇
  2004年   593篇
  2003年   448篇
  2002年   379篇
  2001年   375篇
  2000年   371篇
  1999年   256篇
  1998年   239篇
  1997年   201篇
  1996年   184篇
  1995年   171篇
  1994年   152篇
  1993年   116篇
  1992年   109篇
  1991年   89篇
  1990年   90篇
  1989年   69篇
  1988年   55篇
  1987年   30篇
  1986年   23篇
  1985年   29篇
  1984年   17篇
  1983年   10篇
  1982年   7篇
  1981年   22篇
  1980年   12篇
  1979年   5篇
  1978年   3篇
  1977年   3篇
  1975年   3篇
  1963年   7篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
101.
为研究运输方式对生菜采后生理及保鲜效果的影响,以‘橡生2号’生菜为研究对象,选择3种常见的运输方式:保温箱包装常温运输(A)、保温箱加制冷剂包装在常温下运输(B)、PE包装袋加纸箱包装在0℃下运输(C)进行试验。结果表明,采用C方式在0℃冷藏条件下运输的生菜,其失重率和呼吸强度均低于另外2组,VC含量和感官评价高于另外2组。因此在运输时间在12 h内可以采用A方式运输,在24 h内可以采用B方式运输,如超过24 h则最好使用C方式运输来保证生菜的货架期及品质。  相似文献   
102.
冠春5号是以高代自交系327作母本,以自交系186作父本配制而成的苦瓜一代杂种。植株生长势旺盛,早熟,从播种至始收82 d(天)。主侧蔓均可结果,主蔓第1雌花节位为第7~8节。瓜长棒形,瓜长25~35 cm,横径5~7 cm,肉厚0.9~1.0 cm,单瓜质量420 g左右。果表皮浅绿色,点状突起与短条状突起相间瘤状物,尾部钝,果肉脆,苦味淡。早春栽培一般每667 m~2产量约3 000 kg,田间对白粉病和疫病的抗性优于对照新农村油绿苦瓜。适宜四川、重庆等地种植。  相似文献   
103.
为进一步探究春化基因VRN1在小麦发育进程中的功能,利用荧光定量PCR分析了VRN1基因在不同发育特性小麦品种新春2号、京841中的表达情况。结果表明,随着生育进程的推进,VRN1基因在新春2号叶片和茎尖中表达量均呈上升趋势,VRN1基因在京841叶片中呈波动上升趋势,在茎尖中表达量趋于0;以p FGC5941载体为基础构建含有VRN1反向重复序列的RNA干扰载体,利用农杆菌介导的茎尖转化法转化新春2号获得了再生植株,并通过PCR法检测获得了转基因阳性植株,为从分子水平上实现小麦发育特性遗传改良和创育小麦新种质奠定了基础。  相似文献   
104.
红宝玉是以10R15 为母本、10R8 为父本选育而成的中熟厚皮甜瓜一代杂种。植株长势稳健,抗病抗逆性强。全生育期95~110 d(天),果实发育期30~35 d(天)。果实短椭圆形,成熟后果面乳白色,单果质量约1.5 kg,果肉橘红色,肉厚3.5~4.0 cm,腔小不发酵,中心可溶性固形物含量17.5%,肉质紧脆,不脱蒂,耐贮耐运。平均每667 m2产量3 600 kg 左右。适宜在山东、河北、陕西、安徽等地春季保护地设施栽培。  相似文献   
105.
湘紫薯174 是以浙紫薯1 号为母本、浙紫薯3 号为父本杂交选育而成的食用型紫心甘薯新品种,薯块纺锤形,薯皮 紫红色,薯肉紫色,结薯较集中整齐,单株结薯4~5 个,大中薯率82.7% 以上,熟食味好,抗黑斑病,中抗根腐病、茎线 虫病和薯瘟病;每667 m2 鲜薯产量1 913~2 359 kg,薯干产量549~736 kg;花青素含量为714.5 mg · kg-1(FW)。适宜在湖 南、湖北、江西、江苏、浙江等地春夏薯区种植。  相似文献   
106.
Eleven grape cultivars were analysed to explore the variety differences of fresh grape phenolic profiles. The results showed that free phenolics were predominant in grape skins and pulps, and showed the higher antioxidant activities than bound. In 11 cultivars, Muscat Kyoho extracts had the highest total phenolic content in skins(10.525 mg GAE g~(–1) FW) and pulps(1.134 mg GAE g~(–1) FW), and exhibited the highest DPPH radical scavening capacity(EC_(50)=11.7 μg mL~(–1)) and oxygen radical absorbance capacity(ORAC) value(190.57 μmol TE g~(–1) FW) of free phenolic in skin. In addition, the most abundant phenolics in grape skins were found to be flavonoids such as kaempferol in Kyoho skin(541.2 μg g~(–1) FW), rutin, catechin and epicatechin in Muscat Kyoho skin(262.3, 86.3 and 70.0 μg g~(–1) FW, respectively). Furthermore, the principal component analysis showed a strong difference of phenolic profiles with the cultivars, existing forms and distributions. Pearson correlation coefficient analysis showed a significant linear correlation between total phenolic content and antioxidant activity(P0.05). Therefore, both skins and pulps were rich sources of bioactive phenolic compounds, and Muscat Kyoho was the ideal source among all samples.  相似文献   
107.
对辽宁省不同熟期水稻品种品质性状进行综合分析,为水稻优质育种和栽培提供参考。以辽宁省中早熟、中熟、中晚熟和晚熟4个熟期65个品种(系)为试验材料,分析辽宁省不同熟期水稻品种(系)品质性状差异及其相关关系。结果表明,垩白粒率、垩白度、透明度的变异系数较大,不同熟期间表现基本一致。4个熟期中中早熟品种(系)的品质性状整体较好,只有垩白度的优质米达标率较低,说明垩白性状是今后水稻品质改良的重点。相关分析表明,垩白粒率、垩白度均与直链淀粉含量呈极显著正相关,与胶稠度呈显著负相关,糙米率与精米率、整精米率、胶稠度呈极显著正相关。辽宁省水稻优质育种可通过合理调整直链淀粉含量,降低垩白粒率和垩白度,提高整精米率,实现品质的整体改善。  相似文献   
108.
AIM: To observe the treatment effect and its immune regulation of human amnion epithelial cells (hAECs) on Alzheimer's disease (AD)-like pathology rat model. METHODS: The hAECs were isolated from amnion with trypsin digestion, and the phenotype of hAECs was analyzed by flow cytometry. SD rats (n=48) were randomly divided into sham control group, model group, medium group and hAECs group. AD-like pathology rat model was induced by bilateral intraventricular injection of lipopolysaccharide (LPS). hAECs (5×105) were injected into the hippocampus of the AD-like pathology rats. At 2 weeks after transplantation, the animals were tested by Morris water maze to observe the function of learning and memory. The pathological change of the brain was observed by HE staining. The expression of amyloid β-protein 42(Aβ42) and Tau protein and the level of acetylcholine (ACh) in the injury brain were determined by immunohistochemistry. The survival and differentiation of hAECs in the hippocampus were measured by immunofluorescent technique. The percentages of lymphocyte subsets in the peripheral blood mononuclear cells were analyzed by flow cytometry. The contents of serum cytokines were detected by cytometric bead array. RESULTS: Compared with model group and medium group, hAECs group showed shortened escape latency (P<0.01), increased frequency of going through the platform (P<0.05), reduced loss of hippocampal neurons, decreased expression of Tau protein and Aβ42 in the hippocampus (P<0.05), increased ACh level in the hippocampus (P<0.05), decreased percentages of Th1 and Th17 subsets, increased percentages of Th2 and Treg cells (P<0.05), decreased concentrations of IFN-γ and IL-2 in the serum, and increased concentration of IL-4(P<0.05). CONCLUSION: hAECs improve the cognitive learning and memory function and alleviate pathologic damage of hippocampus through immune regulation in AD-like pathology rats.  相似文献   
109.
AIM: To explore the mechanism by which over-expression of enhancer of zeste homolog 2 (EZH2) in a panel of gastric cancer cell lines is involved in tumorigenesis of gastric cancer. METHODS: Real-time PCR and Western blot were employed to examine the mRNA and protein levels of EZH2, respectively. MTS assay, cell migration and soft agar assay were performed to investigate the role of EZH2 in the regulation of stomach cancer behaviors. The effect of EZH2 on NF-κB target gene expression was determined by Luciferase reporter and real-time PCR. Co-immunoprecipitation was used to analyze the interaction of EZH2 and p65 in HEK293T cells. RESULTS: The expression levels of EZH2 were significantly increased in the gastric cancer cells compared with normal gastric epithelial cells. Pharmacological inhibition by DZNep or knockdown of EZH2 significantly compromised AGS and SNU-16 cell activity, cell migration and anchorage-independent cell growth. Moreover, siRNA knockdown of EZH2 impaired NF-κB downstream targets, such as IL-8, CXCL5 and CCL20. In addition, the interaction of EZH2 and p65 was detected. CONCLUSION: EZH2 mediates the growth of gastric cancer cells through the regulation of NF-κB downstream gene expression.  相似文献   
110.
为提高草莓单产低问题,以具有代表性的草莓品种‘丰香’作为研究对象,在相同营养液中,研究草莓在7种不同基质配方处理下的生长和结果情况,旨在为草莓栽培寻找出一种最佳的基质配方。用SPSS数据处理软件对草莓营养生长时期的各项指标进行方差分析,对差异显著的作进一步多重比较。结果表明:(1)菇渣+珍珠岩+蛭石(C_3)产量最高(781.56 g/株),其次为菇渣+蛭石C_2(745.61 g/株),二者之间差异不显著;C_3平均单果最大19.21 g优于对照处理(草炭+蛭石),二者之间差异显著。(2)C_3风味最好,糖酸比为13.69,其次是C_2,优于对照。综上,C_3优于其他基质,且可以利用工业上的废料,在生产上具有长远的应用价值。  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