全文获取类型
收费全文 | 311篇 |
免费 | 9篇 |
国内免费 | 6篇 |
专业分类
林业 | 6篇 |
农学 | 33篇 |
基础科学 | 3篇 |
39篇 | |
综合类 | 134篇 |
农作物 | 16篇 |
水产渔业 | 6篇 |
畜牧兽医 | 71篇 |
园艺 | 10篇 |
植物保护 | 8篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 10篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 18篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 20篇 |
2008年 | 25篇 |
2007年 | 27篇 |
2006年 | 29篇 |
2005年 | 12篇 |
2004年 | 20篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 13篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1981年 | 1篇 |
排序方式: 共有326条查询结果,搜索用时 46 毫秒
1.
2.
Differential gene expression of Eph‐ephrin A1 and LEPR‐LEP with high or low number of embryos in pigs during implantation 下载免费PDF全文
The objective of this study was to ascertain whether mRNA and protein expressions of implantation‐related genes (erythropoietin‐producing hepatocellular receptor–ligand A1, Eph‐ephrin A1 and leptin receptor–leptin, LEPR‐LEP) differed between pigs with high and low number of embryos, and whether these differences in gene expression might affect embryo implantation. Experimental pig groups (n = 24) for high and low number of embryos were prepared by altering the number of eggs ovulated in pre‐pubertal gilts treated with 1.5 × (High) or 1.0 × (Low) PG600 ([400 IU PMSG + 200 IU hCG]/dose, AKZO‐NOBEL). Gilts expressing oestrus were artificially inseminated twice and maintained in breeding and gestation until the reproductive tract was collected on day 22 of pregnancy. At slaughter, the reproductive tracts from each pregnant gilt from each treatment were immediately processed to collect samples for RNA and protein analysis. Within each gilt, three conceptus points were sampled, one from each horn and then a random conceptus within the tract. At each conceptus point, endometrial attachment site, chorion–allantois and embryo were collected and immediately frozen in liquid nitrogen. Number of corpus luteum (CL) (35.4 vs. 12.6) and total embryo number (18.8 vs. 10.2) were greater in the high‐embryo compared to the low‐embryo group, respectively (p < .05). Real‐time qPCR results showed that Eph‐ephrin A1 mRNA expression was less in the high‐embryo (p < .05) compared to the low‐embryo group. In addition, Western blotting analysis indicated that Eph‐ephrin A1 and LEP protein expression at endometrial attachment site in high‐embryo was less (p < .05) compared to low‐embryo group. It was also noted that mRNA expression of Eph‐ephrin A1 and LEPR‐LEP was greater in pregnant than non‐pregnant gilts (p < .05). Moreover, mRNA expression of Eph‐ephrin A1 (p < .05) and LEPR‐LEP was greatest at endometrial attachment site among all three tissues. There was a positive correlation between expressions of Eph‐ephrin A1, LEPR‐LEP and embryo length with the correlation coefficient 0.31–0.59. For Eph‐ephrin A1, the highest correlation coefficient appeared between Eph A1 expression and normal embryo number, between ephrin A1 expression and embryo length. For LEPR‐LEP, the highest correlation coefficient appeared between LEPR‐LEP expression and ovary weight (0.79 for both, p < .05), followed by embryo length and weight. The results of this study suggest that low expression of Eph‐ephrin A1 and LEPR‐LEP is somehow related to increased embryo number during implantation and that endometrial attachment site might be the main target tissue of these gene products. Yet, the increased expression of Eph‐ephrin A1 and LEPR‐LEP appeared associated with increased embryo growth (length and weight) and ovary weight, Eph‐ephrin A1 and LEPR‐LEP might play roles in the regulation of embryo implantation in pigs. 相似文献
3.
为探索不同离子源对杉木种子发芽生理及保护酶活性的影响,采用氮、钛2种离子源,以当年生杉木优良种子为试材开展种子发芽生理及保护酶活性变化规律的研究.结果表明:氮、钛2种离子注入杉木种子后,均能显著提高种子的发芽质量,其中发芽率提高18.85%~20.00%,发芽整齐性提高16.83%~34.67%,种子活力指数提高43.47%~57.44%;对种子的质膜透性及酶活性影响,钛离子注入的效果强于氮离子注入,MDA含量、SOD、POD活性分别比氮离子注入处理高出16.82%、29.22%、12.29%,而CAT含量相对降低了7.69%,均存在显著性差异. 相似文献
4.
低能离子注入麻黄种子生物效应初步研究 总被引:12,自引:0,他引:12
本文初步研究了离子束注入麻黄种子后的当代生物效应 ,研究表明 :离子注入对麻黄种子的生长起良好的生物效应。注入剂量为 4× 1 0 1 6 N+ / cm2 时 ,伊吾蓝麻黄种子发芽率最高为 76 % ,相对空白增长 4 3.4 % ;在注入剂量为 4× 1 0 1 6 N+ / cm2 ,伊吾蓝麻黄种子的发芽 3天时呼吸速率达 1 .1 4 0 mg/ g· h。这也表明发芽率高的剂量下 ,种子的呼吸速率增加 ,注入剂量为 1 2× 1 0 1 6 N+ / cm2 ,伊吾蓝麻黄种子的盆栽出土率最大为 2 2 .7%。 4× 1 0 1 6 N+ / cm2 剂量离子注入和硕蓝麻黄种子时 ,其盆栽出土率最大为 4 2 .3% ,比对照增加了 6 4 %。 相似文献
5.
6.
7.
对6个尾叶桉和巨桉的全同胞和半同胞家系进行种子离子注入后,观察萌发和苗期生长,结果表明:(1)离子注入对种子发芽有刺激作用,既促进也抑制;(2)离子注入促进树高和侧根数生长,而抑制地径、叶长、叶宽和根生长,表明通过注入有可能获得生产中所需要的目的性状或品种;(3)离子注入的各家系平均生物量低于对照,但差异不显著;离子注入的家系平均叶比重、叶体积、叶肉体积和叶含水量均低于对照;(4)按突变临界值筛选,离子注入苗中共33株入选,突变率为5.323%;按各家系分别筛选,突变率在7.50%~30.00%. 相似文献
8.
9.
人工催熟日本鳗鲡精子的显微和超微结构 总被引:5,自引:0,他引:5
对经人工催产获得的日本鳗鲡(Anguilla japonica)精子的显微和超微结构进行了观察。光镜下观察,日本鳗鲡精子有两种形态结构,一种精子的细胞核为圆形或近
似圆形,这精子较小,细胞核长径为(2.57±0.62) μm,短径为(2.11±0.59) μm,鞭毛长度为(38.35±7.71) μm;另外一种精子的细胞核为“眉形”或“新月形”,精子较大,细胞核长径为(7.66±1.09) μm,短径为(2.54±0.46) μm,鞭毛长度为(38.35±9.02) μm。透射电镜观察结果显示:圆形精子头部的顶端无顶体,植入窝位于细胞核底端的中间,由细胞核向内凹陷而成,呈一沟状,其走向与精子的长轴平行。中心粒复合体位于植入窝内。细胞核的下端有2~3个线粒体。基体的头端呈筒状,由电子致密物构成。基体的尾端分裂成9束。尾部从袖套腔中伸出且细长,轴丝始端与基体的尾端相连,微管多呈电子致密状,轴丝为典型的“9+2”结构。圆形精子为日本鳗鲡正常成熟的精子。“眉形”或“新月形”精子头部细胞核弯曲,在弯曲处有一圆形的球状物,球状物内含有线粒体和中心粒复合体,轴丝为“9+0”结构。这种精子可能存在发育缺陷或没有达到完全正常成熟。 相似文献
10.