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   12786篇
  免费   854篇
  国内免费   1208篇
林业   996篇
农学   958篇
基础科学   697篇
  1525篇
综合类   6009篇
农作物   846篇
水产渔业   577篇
畜牧兽医   1873篇
园艺   776篇
植物保护   591篇
  2024年   70篇
  2023年   226篇
  2022年   541篇
  2021年   570篇
  2020年   509篇
  2019年   543篇
  2018年   371篇
  2017年   547篇
  2016年   430篇
  2015年   632篇
  2014年   599篇
  2013年   779篇
  2012年   1099篇
  2011年   1078篇
  2010年   1012篇
  2009年   923篇
  2008年   895篇
  2007年   806篇
  2006年   660篇
  2005年   533篇
  2004年   366篇
  2003年   280篇
  2002年   357篇
  2001年   327篇
  2000年   229篇
  1999年   112篇
  1998年   56篇
  1997年   54篇
  1996年   44篇
  1995年   42篇
  1994年   32篇
  1993年   33篇
  1992年   21篇
  1991年   11篇
  1990年   14篇
  1989年   13篇
  1988年   9篇
  1987年   4篇
  1986年   7篇
  1984年   2篇
  1982年   1篇
  1979年   1篇
  1976年   1篇
  1966年   1篇
  1965年   1篇
  1962年   6篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
AIM:To investigate whether the bcl-2 antisense oligonucleotide increases the sensitivity of HL60 and K562 cell lines to daunorubicin.METHODS:IC50 for HL60 and K562 was determined with MTT method, the expression levels of Bcl-2 protein were assayed by immunofluorescence using fluoresce isothiocyanate labeling. In addition, apoptosis was detected by morphological observation and flow cytometric analysis of DNA fragmentation.RESULTS:It was found that the two oligonucleotides directed against the coding region and the translation initiation of bcl-2 mRNA, combined respectively with daunorubicin, inhibited expression of bcl-2 protein, increased apoptosis in HL60 and K562 cells, and decreased IC50 of daunorubicin significantly (P<0.05). Compared to the antisense oligonucleotide directed against the translation initiation of bcl-2 mRNA, the antisense oligonucleotide directed against the coding region showed stronger effects in the aspects of increasing the sensitivity of HL60 cells to daunorubicin (P<0.05).CONCLUSIONS:These two antisense sequences in the translation initiation and the coding region of bcl-2 mRNA increased the sensitivity of HL60 and K562 cell lines to daunorubicin in a sequence-specific manner.  相似文献   
32.
AIM:To investigate multi-potential of rat bone marrow mesenchymal stem cells (rBMMSC) and mutation inclination, the rBMMSC were long passaged in vitro. METHODS:Cellular cycles of different passages were assayed by FACSan flow cytometry and karyotypes of passage 6, passage 25 and passage 45 were compared by G-binding analysis. RESULTS:The early passages and long-term passages all showed strong proliferation; passage 6, passage 25 and passage 45 all showed normal karyotype. CONCLUSION:Long-term culture and passage of rBMMSC still remains strong proliferation. With this capability, the mutation inclination is not enhanced.  相似文献   
33.
AIM:To investigate the effect of tea-polyphenols (TP) on the activation of NF-κB and the expression of TGF-β1 mRNA in THP-1 cells (a human acute monocytic leukemia cell line). METHODS:THP-1 cells were incubated with the different concentrations of TP, VLDL, LDL or ox-LDL. In the THP-1 cellls, the nuclear malposition rate of NF-κB was detected with immunohistochemistry technique, the positive index of the TGF-β1 mRNA expression was detected by hybridization in situ, and accumulation of total cholesterol (TC) in cells incubated with 0.4-40 μg/L TP was determined with oxidase assay. RESULTS:The nuclear malposition rate of NF-κB, the positive index of the TGF-β1 mRNA expression and TC in THP-1 cells incubated with 0.4-40 μg/L of TP were lower than those with 0 μg/L of TP in TP-V group, TP-L group and TP-O (P<0.05). The differences of these markers in THP-1 cells incubated with more than 40 μg/L TP in TP-V group, TP-L group and TP-O were not statistically significant, compared with TP-C group (P>0.05). CONCLUSION:TP inhibited the activation of NF-κB, the expression of TGF-β1 mRNA and the foam cell formation in the mono-macrophage.  相似文献   
34.
转 Bt基因抗虫棉对棉大卷叶螟抗性的研究   总被引:7,自引:0,他引:7  
:转Bt基因抗虫棉对棉铃虫有很好的抗性,对棉大卷叶螟(SyleptaderogataFabricius)的抗性未见报道。作者研究表明,棉大卷叶螟在棉田为聚集分布型,低龄幼虫有集中为害习性;抗虫棉对其有很好的抗性,平均虫株率为2.2%,较常规棉中棉所12降低96.6%;百株虫量为133.8头,较常规棉降低88.4%。  相似文献   
35.
该文通过分析巴旦杏在甘肃河西地区引种培育过程中出现的问题,总结出用容器育苗和大田开沟点播相结合来培育接穗,以山桃为砧木嫁接巴旦杏的引种驯化技术.结果表明,容器培育接穗比直接大田点播出苗率、成活率分别提高了10%和15%;巴旦杏与山桃嫁接表现出极好的亲和性,嫁接成活率为90%.  相似文献   
36.
姬松茸与双孢蘑菇不同菌株的RAPD扩增研究   总被引:6,自引:1,他引:6  
以4个姬松茸菌株和2个双孢蘑菇菌株为材料,用20个随机引物对它们进行RAPD扩增,通过对供试菌株遗传相似系数的估算和系统聚类分析,构建姬松茸和双孢蘑菇遗传相关树状聚类图谱,结果表明,进行RAPD扩增的20个随机引物中,有12个能产生三种带型,当遗传相似系数升至0.8713时,这6个菌株被分为3类,第一类为菌株18和26,第二类为菌株13和12,第三类为菌株33和45。  相似文献   
37.
AIM:To explore the expressive profile of nestin protein in the focal ischemic brain and to study the recovery mechanism of brain focal infarct.METHODS:Cellular morphology,time-course and distribution pattern of nestin positive response were immunohistochemically examined in different brain regions of 36 adult male SD rats. RESULTS:Nestin positive response of different brain regions in sham operated rats was present in small- and micro-vasculartures and the third ventricle bottom and ependyma. A large number of nestin positive cells were detected in ischemic brain, and were more remarkable in the cortical areas of parietal lobe and preoptic area as well as ischemic caudoputamen. Stellate nestin positive cells were located in the deep layer of ischemic cortex, but fibrillary cells were located in the shallow layer. Nestin positive cells in the ischemic caudoputamen showed the same changes of morphology as those cells in the deep layer of ischemic cortex. Morphological and number alterations of nestin positive cells were the most remarkable at 1 weeks post-ischemia, which showed more hypertrophy and proliferation in morphology, and a marked increase in number was present in the ischemic cerebral cortex and the ischemic caudoputamen. These alterations of nestin positive cells persisted up to 6 weeks post-ischemia, and then, the nestin positive response in the ischemic brain decreased gradually.CONCLUSION:Focal cerebral ischemia induces nestin re-expression on reactive astrocytes, which may be very important to the self-recovery of cerebral infarct.  相似文献   
38.
39.
 ‘渝红6号’番茄是新育成的一代杂种, 自封顶类型, 生长势强, 叶片肥大, 叶色浓绿, 不卷叶, 不早衰; 果面光滑, 无绿果肩, 成熟果红色, 平均单果质量230 g; 可溶性固形物含量5. 24%, 维生素C 含量0. 181 mg / g; 皮厚, 耐贮运; 中抗TMV, 抗枯萎病; 耐低温, 耐弱光; 适宜长江流域早熟大棚栽培和春秋露地栽培。  相似文献   
40.
黄花蒿粗提物对几种害虫拒食性的初步研究   总被引:10,自引:0,他引:10  
以黄花镐为原料进行浸提,经生物活性测定,结果表明黄花蒿Artenisia annua L.粗提物对供试的6种害虫均具有拒食性。其中对黑翅土白蚁Odontotermes formosanus Shiraki、赤拟谷盗Thibolium castaneum Herbst、谷蠹Rhizopertha dominica Fabricius拒食性极强,对棉蚜Aphis gossypii Glover、棉红蜘蛛Tetranychus urticae Koch及豇豆荚螟Etiella zinckenella Treitschke 也具有较强的巨食性。使用黄花蒿粗提物时,以稀释500倍和800倍效果最好,处理与对照之间有极显著差异。  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