全文获取类型
收费全文 | 1618篇 |
免费 | 49篇 |
国内免费 | 153篇 |
专业分类
林业 | 172篇 |
农学 | 239篇 |
基础科学 | 119篇 |
260篇 | |
综合类 | 418篇 |
农作物 | 93篇 |
水产渔业 | 46篇 |
畜牧兽医 | 307篇 |
园艺 | 57篇 |
植物保护 | 109篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 52篇 |
2021年 | 46篇 |
2020年 | 45篇 |
2019年 | 68篇 |
2018年 | 41篇 |
2017年 | 70篇 |
2016年 | 49篇 |
2015年 | 61篇 |
2014年 | 52篇 |
2013年 | 99篇 |
2012年 | 124篇 |
2011年 | 107篇 |
2010年 | 81篇 |
2009年 | 92篇 |
2008年 | 58篇 |
2007年 | 65篇 |
2006年 | 83篇 |
2005年 | 72篇 |
2004年 | 48篇 |
2003年 | 46篇 |
2002年 | 29篇 |
2001年 | 28篇 |
2000年 | 35篇 |
1999年 | 49篇 |
1998年 | 45篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 31篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1820条查询结果,搜索用时 15 毫秒
71.
对28只(♀16,♂12)成年普通利猬(Erinaceuseuropaeus)的骨骼标本进行了解剖学研究,结果表明,普通刺猬全身骨骼有316~317枚,其中头骨48枚,脊椎骨43~44杖,椎式为C7T15L6S3Cy12~13,肋骨15对,胸骨5枚,前肢骨每侧47杖,后肢骨每侧48枚。普通刺猬骨骼存在有性别差异并表现出与刺猬生活习性相适应的一些特征。 相似文献
72.
Promoter anchored amplified polymorphism based on random amplified polymorphic DNA (PAAP-RAPD) in cotton 总被引:1,自引:0,他引:1
Non-coding sequences account for a majority of the higher plant genome, some of which have important effects in gene regulation
and plant development. In an effort to develop molecular marker systems to search for polymorphisms associated with high fiber
yield and quality in cotton, we have developed a methodology that could specifically target the regulatory regions of the
cotton genome. In this study we designed 10-nucleotide degenerate promoter primers based on conserved core promoter sequences
and tested their applicability in PCR amplifications in combination with 10-mer random amplified polymorphic DNA (RAPD) primers.
The amplified markers are called promoter anchored amplified polymorphism based on RAPD (PAAP-RAPD). Forty cotton genotypes
with diverse genetic and geographical backgrounds were used to test the PAAP-RAPD system using polyacrylamide gel electrophoresis.
Based on PAAP-RAPD markers amplified from 12 primer combinations, the 40 genotypes were classified into five distinctive groups:
two Upland cotton (Gossypium hirsutum) groups from China, another two Upland cotton groups from the USA, and one group from American Pima cotton (G. barbadense). The groupings are in general consistent with their genetic and geographical origins. Thirty-six PAAP-RAPD and RAPD fragments
were cloned and four of them were further subjected to sequence analysis. Signal scanning using software PLACE confirmed that
they contained an array of cis-regulatory sequences in addition to the core promoter sequences. The results demonstrate the
potential application of PAAP-RAPD as a new marker system specifically targeting regulatory regions of the plant genome. 相似文献
73.
74.
75.
痣鳞鳃金龟二年发生一代 ,此虫在砂质土壤的林地密度大 ,为害严重。造林时在每株根际施 5g 3 %呋喃丹颗粒剂 ,可有效地控制此虫的危害并兼治其它地下害虫和造林初期的食叶害虫。 相似文献
76.
重组质粒pP18PH3上含有SINPV的部分蛋白激酶基因。SINPV部分的蛋白激酶氨基酸序列与HaN-PV、HzNPV、SpliNPV、AfNPV、AcNPV、LdNPV蛋白激酶的氨基酸序列的同源性分别为45%、89%、37%、44%、38%和37%,其上含有蛋白激酶特征序列IVHANDVKLENVL。 相似文献
77.
体积管是检定流量计的标准器。YTG型双向体积管,其外型尺寸、主体结构、检定速度、日常管理等方面,均比单向体积管有明显的优点,并具有独特的容积补偿性,给体积管的管理、使用带来极大方便。介绍了YTG型双向体积管的结构、技术指标及其优越性,并建议在条件允许的情况下,尽可能使用双向体积管。 相似文献
78.
Myocardial and pancreatic lesions induced by sublethal doses of T-2 toxin in swine were characterized by light and electron microscopy. Toxin was given intravenously to six 17- to 18-week-old pigs. Pigs were killed 24 or 48 hours after treatment. Grossly, subendocardial hemorrhages, multifocal pinpoint white foci in myocardium, and pancreatic edema occurred in one treated pig. Histologic changes in myocardium of treated pigs consisted of multifocal edema, mononuclear cell infiltration, myofiber hyalinization, vacuolation, and contraction bands with nuclear pyknosis. Ultrastructurally, there were areas of edema, myofibrillar disorganization, dilation of sarcoplasmic reticulum, and formation of hypercontraction bands. Myocardial mineralization was seen in the pig with gross lesions. Pancreatic changes in treated pigs consisted of multifocal acinar degeneration and necrosis. Ultrastructural changes included irregular dilation of rough endoplasmic reticulum and abnormal zymogen granules. Thus, in addition to radiomimetic lesions of the gastrointestinal tract and lymphoid organs, heart and pancreas are target organs of T-2 toxin in swine. 相似文献
80.