全文获取类型
收费全文 | 1497篇 |
免费 | 98篇 |
国内免费 | 174篇 |
专业分类
林业 | 140篇 |
农学 | 148篇 |
基础科学 | 139篇 |
250篇 | |
综合类 | 587篇 |
农作物 | 80篇 |
水产渔业 | 45篇 |
畜牧兽医 | 208篇 |
园艺 | 103篇 |
植物保护 | 69篇 |
出版年
2024年 | 14篇 |
2023年 | 26篇 |
2022年 | 82篇 |
2021年 | 111篇 |
2020年 | 93篇 |
2019年 | 103篇 |
2018年 | 54篇 |
2017年 | 85篇 |
2016年 | 56篇 |
2015年 | 101篇 |
2014年 | 92篇 |
2013年 | 110篇 |
2012年 | 128篇 |
2011年 | 124篇 |
2010年 | 113篇 |
2009年 | 94篇 |
2008年 | 49篇 |
2007年 | 67篇 |
2006年 | 47篇 |
2005年 | 35篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 32篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1769条查询结果,搜索用时 46 毫秒
1.
为了进一步研究甜菜谷胱甘肽转移酶BvGSTU9 (LOC104894060)在重金属胁迫过程中的功能。本研究以‘780016B/12优’为实验材料,对该基因序列特征、结构、功能进行预测分析,并利用qPCR检测该基因在不同浓度镉胁迫下的表达量变化。结果显示甜菜BvGSTU9基因全长925 bp,开放阅读框675 bp,编码了由224个氨基酸组成的不稳定膜外蛋白。BvGSTU9与菠菜、藜麦的氨基酸序列相似性较高,与系统发育进化树分析结果基本相符。二级和三级结构预测表明该基因主要由α-螺旋、β-折叠、延伸链及无规则卷曲组成。qPCR显示BvGSTU9基因在不同浓度的镉胁迫下均受到不同程度的诱导,因此可以推断甜菜BvGSTU9基因无论从结构还是功能上,与镉逆境胁迫存在着一定的应答关系。研究结果也为甜菜耐重金属镉机制研究提供参考依据。 相似文献
2.
3.
4.
Six shipments totaling 3452 mummies of the blackmargined aphid,Monellia caryella (Fitch), parasitized withAphelinus perpallidus Gahan, were obtained by air freight during the years 1982-1985 from Texas A&M Research Center, El Paso, Texas. About two-thirds of the mummies did not yield parasites. A colony ofA. perpallidus was established in the laboratory. Under laboratory conditions the percentage of emerged parasites was higher than that in the imported mummies, and the parasite had very limited impact on the aphid population. Field releases of the parasite were made but no establishment ofA. perpallidus was observed through the years. 相似文献
5.
Willem A. Man in 't Veld Arthur W.A.M. de Cock Elena Ilieva C. André Lévesque 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(1):51-62
Isozyme analysis and sequence analysis of the internal transcribed spacer regions (ITS-1 and ITS-2) and the 5.8S subunit of the ribosomal DNA gene repeat were used to examine whether isolates of Phytophthora porri from Allium and Brassica represent a single homogeneous species. Twenty-six strains of P. porri, 16 strains isolated from the genus Allium, and 10 strains isolated from the genus Brassica, were analyzed using malate dehydrogenase (MDH), isocitrate dehydrogenase (IDH) and lactate dehydrogenase (LDH), represented altogether by four putative loci (Mdh-2, Idh-1, Idh-2, and Ldh-2). Isozyme analysis revealed that strains isolated from Allium contained five private alleles at three isozyme loci (Ldh-2
83, Ldh-2
104, Idh-1
108, Idh-1
112, and Idh-2
98), whereas six different alleles were observed at four isozyme loci (Ldh-2
85, Ldh-2
100, Ldh-2
114, Idh-1
100, Idh-2
100, and Mdh-2
111) in strains obtained from Brassica. The heterozygosity at the Ldh-2 locus, differing in allele composition, however, between strains from Allium and Brassica, was present in all strains, indicating that it is probably fixed. Sequence analysis of the ITS regions and the 5.8S subunit showed consistent differences between isolates from Allium and isolates from Brassica. Based on isozyme data, ITS sequence analysis and formerly published differences in restriction enzyme patterns of mitochondrial DNA, morphology and pathogenicity, it was concluded that the isolates of P. porri Foister did not represent a homogeneous species. Isolates from Brassica constitute a distinct species which is described here as P. brassicae sp. nov. It was inferred from isozyme patterns, which were in no case intermediate between the two species, that P. porri and P. brassicae do not hybridize and are reproductively isolated by barriers to gene flow. 相似文献
6.
Kumiko TAKEDA Masahiro SATOH Shreeram P. NEOPANE Bahadur S. KUWAR Hari D. JOSHI Nanda P. SHRESTHA Hiroshi FUJISE Mariko TASAI Takahiro TAGAMI Hirofumi HANADA 《Animal Science Journal》2004,75(2):103-110
Dwarf Lulu cattle, the only Bos Taurus type of cattle in Nepal, are raised under severe environments in the mountainous zone of that country. In the present study, the body measurement traits, cytogenetic and molecular genetic characteristics of the Lulu cattle are investigated. Blood samples were collected from 31 animals in four villages (altitudes 2590–3550 m) in the southern part of Mustang. The Lulu cattle had a normal karyotype with 2n = 60, XY or XX. Only one male examined had a large submetacentric X‐chromosome and a small submetacentric taurine type Y‐chromosome. The mitochodrial DNA (mtDNA) genotypes were analyzed by PCR mediated restriction fragment length polymorphisms, displacement (D)‐loop region PCR mediated single strand conformation polymorphisms, and D‐loop region sequences. Many base substitutions were found in the D‐loop region, suggesting that the Lulu cattle originated from at least 10 maternal lines. Three types of mtDNA from these cattle were found, the Bos taurus type (n = 23), the Bos indicus type (n = 6), and the Bos grunniens type (n = 2). In the village at the lowest altitude, four of the five cows were of the Bos indicus type. These results indicated that mtDNA types of the Lulu cattle mostly belong to Bos taurus, but have been hybridized with Bos indicus cattle in lower‐elevation regions in their maternal lineage. 相似文献
7.
8.
2017年7月7日,农业部决定对全国家禽开展H7亚型流感免疫。为了掌握重组禽流感病毒(H5+H7)二价灭活苗的免疫效果,2017年8—9月,重庆市动物疫病预防控制中心进行了控制性试验和大面积临床监测。控制试验结果表明:首免15 d后,H7亚型禽流感抗体合格率可达70.00%,H5亚型抗体合格率仅为10.00%;首免22 d后,H7亚型禽流感抗体合格率达到93.33%,H5亚型抗体合格率达到60.00%;该疫苗未出现严重免疫副反应;H7亚型禽流感抗体产生的时间早于H5亚型。随机选取5个区县,采集414份免疫血清进行监测。结果显示:二价灭活苗免疫21 d后,H5和H7亚型禽流感抗体平均合格率分别为92.27%和76.00%;5个区县的抗体水平存在差异;蛋鸡抗体水平高于肉鸡。控制试验及临床监测结果提示,该疫苗免疫效果确实,但部分区县仍存在免疫抗体水平不高的养禽场。因此,在新旧疫苗交替使用期间,各地应高度重视高致病性H5和H7亚型禽流感防治工作,尤其是肉鸡。 相似文献
9.
10.
研究并设计了一种基于VB的温室温湿度实时监测上位机系统。该系统能实现对现场采集的温湿度数据进行实时监测,并针对不同的作物,当环境温湿度参数越限时,启动声音报警,以便管理员介入进行自动或手动调控。提供温室作物最佳的温湿度生长环境,提高温室的自动化程度和生产效率。该系统应用软件工程的设计思想,以Microsoft Visual Basic 6.0为开发环境,Microsoft Access为后台数据库,采用模块化的设计方法,利用面向对象、数据库等技术完成系统数据的实时显示、信息和数据的存储、历史数据查询、统计分析、打印和异常报警等功能,实现了上位机系统的监测任务。介绍了系统的总体设计和各功能模块的设计,说明了该系统的主要功能,并给出了系统的运行界面和部分代码,在系统和数据库安全方面也采取了一定措施。 相似文献