全文获取类型
收费全文 | 41350篇 |
免费 | 2410篇 |
国内免费 | 4438篇 |
专业分类
林业 | 2922篇 |
农学 | 3260篇 |
基础科学 | 2496篇 |
4703篇 | |
综合类 | 18467篇 |
农作物 | 2798篇 |
水产渔业 | 1529篇 |
畜牧兽医 | 6939篇 |
园艺 | 2894篇 |
植物保护 | 2190篇 |
出版年
2024年 | 277篇 |
2023年 | 856篇 |
2022年 | 2032篇 |
2021年 | 2023篇 |
2020年 | 1850篇 |
2019年 | 1855篇 |
2018年 | 1305篇 |
2017年 | 1933篇 |
2016年 | 1461篇 |
2015年 | 2098篇 |
2014年 | 2198篇 |
2013年 | 2550篇 |
2012年 | 3495篇 |
2011年 | 3525篇 |
2010年 | 3290篇 |
2009年 | 2949篇 |
2008年 | 2877篇 |
2007年 | 2575篇 |
2006年 | 2110篇 |
2005年 | 1651篇 |
2004年 | 1017篇 |
2003年 | 631篇 |
2002年 | 745篇 |
2001年 | 660篇 |
2000年 | 631篇 |
1999年 | 337篇 |
1998年 | 169篇 |
1997年 | 128篇 |
1996年 | 124篇 |
1995年 | 115篇 |
1994年 | 135篇 |
1993年 | 101篇 |
1992年 | 108篇 |
1991年 | 73篇 |
1990年 | 85篇 |
1989年 | 63篇 |
1988年 | 42篇 |
1987年 | 28篇 |
1986年 | 19篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 5篇 |
1981年 | 14篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1965年 | 3篇 |
1963年 | 3篇 |
1962年 | 10篇 |
1956年 | 12篇 |
1955年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
为研究不同加工方式对芒果干制过程中保鲜类农药残留量的影响,以芒果干的加工过程为例,研究清洗、去皮、护色、硬化、热烫及干燥等各个加工环节对芒果中常用保鲜类农药咪鲜胺、多菌灵、甲基硫菌灵及代谢物2-氨基苯并咪唑残留量变化规律的影响。结果表明:在芒果干制的过程中,随着加工环节的增加,芒果中常用保鲜类农药总体呈逐渐下降的趋势;去皮对咪鲜胺的影响最大,降解率达94.82%;干燥脱水的过程使得芒果干中4种农药的残留量增加,与真空干燥相比,恒温干燥箱干燥可以较大程度的去除芒果干制过程中的大部分农药残留,农药去除效果较好。 相似文献
992.
993.
玉米单倍体育种技术加倍率低的问题是单倍体育种技术应用限制条件。本研究以雄穗低自然加倍材料DHL287为母本、雄穗高自然加倍材料吉Gjb335DH3为父本,构建单倍体雄穗高自然加倍群体。根据集群分离分析法(BSA,Bulked segregant analysis),结合SNP标记,使用滑动窗口分析3组BSA混池基因型数据,最终在1、3、4、5、7号染色体上筛选出23个与雄穗高自然加倍相关的QTL位点。其中,3组BSA混池结果都在1、3、4号染色体上定位到4个共有的显著QTL区段,说明4个QTL区段具有很强的重演性。同时,在5、7号染色体上分别定位到3个、2个与单倍体雄穗高自然加倍相关的QTL位点。 相似文献
994.
995.
运用PCR和RACE技术从巴西橡胶树中克隆出了一个域重排甲基转移酶(Domains rearranged methyltransferase,DRM)基因(HbDRM)。HbDRM全长为2 245 bp,含有1 917 bp的阅读框,145 bp的5′-UTR和176 bp 3′-UTR,编码638个氨基酸,分子量为71.39 ku,等电点为4.90。HbDRM的氨基酸序列与可可、葡萄、黄瓜、鹰嘴豆、番茄、拟南芥DRM家族成员的同源性分别为77%、74%、72%、67%、64%和52%。定量RT-PCR分析表明HbDRM在巴西橡胶树的根、树皮、叶、花、胶乳、胚和愈伤组织中均有表达,其中在花和愈伤组织中表达量较高,在胶乳中表达量最低,此外HbDRM在橡胶树自根幼态无性系的胶乳中表达比其供体胶乳中的表达低。HbDRM的克隆和表达分析为下一步研究HbDRM在巴西橡胶树自根幼态无性系高产中的作用打下基础。 相似文献
996.
以湖南省10份自育烤烟品系为材料进行区域试验,并对试验结果进行丰产性及稳定性分析。结果表明,在湖南省4个烟区,品系V10(0522)产值最高,达到了42918.57元/hm2,品系(种)与地点互作方差和变异度值最小,且回归系数小于1,高产的同时稳定性也好,适应性强;品系 V8(CZ-24)的产值和稳定性均高于对照 V11(K326),有推广利用的价值;品系V2(C72-6-2)、V7(0511)的产值均高于对照V11(K326),其产值分别为39941.37元/hm2、37536.23元/hm2,但其稳定性表现均不理想;其余品系丰产性及稳定性均不如对照V11(K326)。 相似文献
997.
The Changes of Organic Carbon and Its Fractions in Yellow Paddy Soils Under Long-Term Fertilization 总被引:3,自引:0,他引:3
WANG XiaoLi GUO Zhen DUAN JianJun ZHOU ZhiGang LIU YanLing ZHANG YaRong 《中国农业科学》2017,50(23):4593-4601
998.
Xiang ZHANG Qiu-zhi RUI Pan-pan LIANG Chen-hua WEI Guo-qiang DENG Yuan CHEN Yuan CHEN Zhao-di DONG De-hua CHEN 《农业科学学报》2018,17(9):1991-1998
This study was conducted to investigate the effects of alternating high temperature on Cry1Ac protein content on Bt cotton cultivars Sikang 1(SK-1,a conventional cultivar)and Sikang 3(SK-3,a hybrid cultivar).In 2011 and 2012,cotton plants were subjected to high temperature treatments ranging from 32 to 40℃ in climate chambers to investigate the effects of high temperature on boll shell insecticidal protein expression.The experiments showed that significant decline of the boll shell insecticidal protein was detected at temperatures higher than 38℃ after 24 h.Based on the results,the cotton plants were treated with the threshold temperature of 38℃ from 6:00 a.m.to 6:00 p.m.followed by a normal temperature of 27℃ during the remaining night hours(DH/NN)in 2012 and 2013.These treatments were conducted at peak boll growth stage for both cultivars in study periods of 0,4,7,and 10 d.Temperature treatment of 32℃ from 6:00 a.m.to 6:00 p.m.and 27℃ in the remaining hours was set as control.The results showed that,compared with the control,after the DH/NN stress treatment applied for 7 d,the boll shell Cry1Ac protein content level was significantly decreased by 19.1 and 17.5% for SK-1 and by 15.3 and 13.7% for SK-3 in 2012 and 2013,respectively.Further analysis of nitrogen metabolic physiology under DH/NN showed that the soluble protein content and the glutamic pyruvic transaminase(GPT)activities decreased slightly after 4 d,and then decreased sharply after 7 d.The free amino acid content and the protease content increased sharply after 7 d.The changes in SK-1 were greater than those in SK-3.These results suggest that under DH/NN stress,boll shell Cry1Ac protein content decline was delayed.Reduced protein synthesis and increased protein degradation in the boll shell decreased protein content,including Bt protein,which may reduce resistance to the cotton bollworm. 相似文献
999.
Maize rough dwarf disease (MRDD) is a viral disease caused by brown planthopper infestation, and leads to great yield loss, especially in China. Comparative proteomics was performed using maize inbred line Zheng 58 and LN 287. MRDD pathogen was detected as rice black-streaked dwarf virus (RBSDV) by quantitative real time PCR (qRT-PCR) in Shandong Province, China. The modified trichloroacetic acid (TCA)/acetone method was used for soluble protein extraction from leaves. Two-dimensional electrophoresis (2-DE) analysis was performed on 24-cm long, pH 4–7 linear immobilized pH gradient (IPG) strips, and gels were stained with silver and coomassie brilliant blue. We identified 944 proteins expressed in RBSDV infected maize leaves by proteomics approaches. Among these, 44 protein spots that revealed a 1.5-fold difference in intensity were identified by mass spectrometry between mock-inoculated and RBSDV infected samples. Among these, 17 and 26 spots were up-regulated, and 27 and 18 spots were down-regulated in the virus infected samples of Zheng 58 and LN 287, respectively. Differential protein spots were analyzed by mass spectrometry identification, which could be divided into six categories. Furthermore, the expression of stress-related proteins was detected and confirmed by qRT-PCR. This study lays the foundation for further investigations, enabling the enhancement of MRDD resistance in maize. 相似文献
1000.
茶尺蠖核型多角体病毒(Ectropis obliqua nucleopolyhedrosis virus,EoNPV)是一种重要的病原微生物,为进一步明确该病毒对茶尺蠖两近缘种的毒力差异,采用叶盘法对3龄茶尺蠖和灰茶尺蠖幼虫进行了EoNPV的毒力测定。研究显示,EoNPV对灰茶尺蠖的半致死剂量LD50(median lethal dose)为茶尺蠖的28.9倍,EoNPV对灰茶尺蠖的致死中时间LT50(median lethal time)大于茶尺蠖。结果表明,EoNPV对茶尺蠖两近缘种间的毒力存在差异,EoNPV对茶尺蠖具有更高的致病力,研究结果对EoNPV田间防治茶尺蠖两近缘种具有现实指导意义。 相似文献