全文获取类型
收费全文 | 7315篇 |
免费 | 375篇 |
国内免费 | 870篇 |
专业分类
林业 | 948篇 |
农学 | 1226篇 |
基础科学 | 568篇 |
1288篇 | |
综合类 | 2070篇 |
农作物 | 443篇 |
水产渔业 | 336篇 |
畜牧兽医 | 884篇 |
园艺 | 254篇 |
植物保护 | 543篇 |
出版年
2024年 | 18篇 |
2023年 | 54篇 |
2022年 | 212篇 |
2021年 | 297篇 |
2020年 | 279篇 |
2019年 | 293篇 |
2018年 | 178篇 |
2017年 | 260篇 |
2016年 | 235篇 |
2015年 | 309篇 |
2014年 | 290篇 |
2013年 | 379篇 |
2012年 | 453篇 |
2011年 | 466篇 |
2010年 | 455篇 |
2009年 | 452篇 |
2008年 | 386篇 |
2007年 | 389篇 |
2006年 | 447篇 |
2005年 | 437篇 |
2004年 | 204篇 |
2003年 | 149篇 |
2002年 | 119篇 |
2001年 | 134篇 |
2000年 | 153篇 |
1999年 | 219篇 |
1998年 | 172篇 |
1997年 | 158篇 |
1996年 | 131篇 |
1995年 | 114篇 |
1994年 | 106篇 |
1993年 | 107篇 |
1992年 | 102篇 |
1991年 | 71篇 |
1990年 | 81篇 |
1989年 | 74篇 |
1988年 | 55篇 |
1987年 | 40篇 |
1986年 | 25篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有8560条查询结果,搜索用时 93 毫秒
941.
烤烟易烤性QTL定位分析 总被引:1,自引:0,他引:1
利用易烤性好的烤烟品种云烟85和易烤性差的烤烟品种大白筋599杂交所得到的F2群体为作图群体,借助SSR分子标记技术,在群体中共获得91个多态性标记,利用Mapmaker3.0作图软件,构建了一个含17个连锁群、75个标记的烤烟遗传连锁图。利用该图谱和易烤性表型数据,通过复合区间作图法进行QTL检测,共检测到与易烤性相关的4个QTL,分别位于1、8、9连锁群上,可解释的表型变异分别为9.26%、8.87%、7.57%和7.83%。4个QTL的加性效应值均为正值,说明易烤性增加的效应均来自母本云烟85。 相似文献
942.
943.
“十月桔”黄化与正常植株的矿质养分及果实品质比较 总被引:1,自引:0,他引:1
广东省“十月桔”(沙糖桔)叶片黄化现象目前有增加的趋势.以同一果园中正常树和严重黄化树为试材,测定分析其根际土壤和叶片矿质养分、叶片养分的DRIS值及果实品质.结果表明,与正常树果实相比,黄化树果实变小,着色变差,可滴定酸、维生素C和还原糖的含量提高,风味偏酸;供试果园土壤偏酸并处于缺镁、缺钙和缺锌状态,正常树与黄化树根际土壤矿质元素差异以有效钙最大;黄化树叶片中钙与锌的含量显著低于正常树,其余无显著差异;在叶片镁明显不足的背景下,再严重缺钙和一定程度缺锌是导致黄化的主要原因. 相似文献
944.
945.
为探讨酸化处理及钙对酸化处理下平邑甜茶根系抗氧化酶活性及线粒体功能的影响,将平邑甜茶幼苗分2组分别置于pH3,4,5,6(对照)的1/2Hoagland营养液中及3个钙离子浓度梯度(10,20,30mmol·L-1)的pH值为3的1/2Hoagland营养液中,于第0,2,3,4天分别测定抗氧化酶活性及线粒体指标。结果表明:与对照相比,各处理的SOD,CAT酶活性在处理的第2天达到最大值,POD酶活性变化不一,pH3与pH4处理在第2天达到最大值,pH5处理在第3天达到最大值;根系线粒体膜通透性、膜电位及细胞色素c/a随着酸度增加和时间的延长逐渐降低;H2O2含量先降低后升高。低浓度外源钙(10,20mmol·L-1)处理能提高SOD,CAT,POD酶活性并维持一定时间,缓解线粒体各项功能的伤害,抑制H2O2的积累,主要表现在与单独酸处理相比H2O2含量降低了6.78%,13.43%,且20mmol·L-1钙离子缓解效果最好;30mmol·L-1钙离子处理却加剧了酸化伤害,H2O2含量上升了8.96%。酸化处理会对平邑甜茶根系造成伤害而营养液适量加钙可以缓解其伤害。 相似文献
946.
Four new sesquiterpenes, myrrhterpenoids K-N (1-4) have been isolated from the resin of Commiphora myrrha. Their structures and relative configurations were elucidated by spectroscopic methods (IR, ESIMS, HR-ESIMS, 1D and 2D NMR). Compounds 1 and 4 showed neuroprotective effects against MPP(+)-induced neuronal cell death in SH-SY5Y cells. 相似文献
947.
948.
Human-wildlife conflict (HWC) is a conservation concern that increasingly threatens the continued existence of some of the world's most endangered species. With an increase in human population, urban sprawl and subsequent encroachment on wild land, human and wildlife interaction has become inevitable. In the majority of cases, this interaction results in a negative outcome for humans, wildlife or both. In China, these key elements, along with a decrease in wild prey species, have resulted in the expansion of HWC encounters, and the need for alleviating this conflict has become a conservation priority. Loss of human life, livestock and/or crops is most often the catalysts that fuel HWC. Techniques to alleviate conflict around the world have included preventative measures and mitigation techniques, such as financial compensation and other incentive programs. Both types of measures have had variable success. We review the current status of human-carnivore conflict management in China, and, drawing lessons from around the globe, we make recommendations for improving conservation management in China. For example, an increase in law enforcement in nature reserves is vital to reducing human disturbance in prime carnivore habitat, thereby reducing conflict encounters. Also, modifications to current wildlife compensation programs, so that they are linked with preventative measures, will ensure that moral hazards are avoided. Furthermore, investigating the potential for a community self-financed insurance scheme to fund compensation and increasing efforts to restore wild prey populations will improve the outcome for wildlife conservation. Ultimately, HWC management in China will greatly benefit from an integrative approach. 相似文献
949.
Two clonal trial stands of Chinese Fir (Cunninghamia lanceolata) were used in this study, one was 19-year-old stand which included 38 clones, and the other was 17-year-old stand including 102 clones.The statistical analyses showed that there were very significant genetic variations in height, DBH,volume and ratio of heartwood(Rhw),wood basic density(ρb ) of the clones in the two stands. The repeatability of clones was in median to high level,and the genetic CV was different over the all five traits.There were very significant phenotypic and genetic correlations among height,DBH and volume,and negative correlations among growth, Rhw andρb.The selection method experiment indicated that index selection could improve volume, Rhw andρb,showing synthetically superior selection effects compared to any individual trait selection methods. 相似文献
950.