全文获取类型
收费全文 | 2483篇 |
免费 | 88篇 |
国内免费 | 248篇 |
专业分类
林业 | 203篇 |
农学 | 242篇 |
基础科学 | 46篇 |
191篇 | |
综合类 | 1249篇 |
农作物 | 144篇 |
水产渔业 | 136篇 |
畜牧兽医 | 429篇 |
园艺 | 80篇 |
植物保护 | 99篇 |
出版年
2024年 | 8篇 |
2023年 | 30篇 |
2022年 | 56篇 |
2021年 | 58篇 |
2020年 | 60篇 |
2019年 | 76篇 |
2018年 | 51篇 |
2017年 | 92篇 |
2016年 | 114篇 |
2015年 | 89篇 |
2014年 | 140篇 |
2013年 | 147篇 |
2012年 | 233篇 |
2011年 | 204篇 |
2010年 | 159篇 |
2009年 | 149篇 |
2008年 | 147篇 |
2007年 | 152篇 |
2006年 | 133篇 |
2005年 | 115篇 |
2004年 | 72篇 |
2003年 | 62篇 |
2002年 | 56篇 |
2001年 | 46篇 |
2000年 | 56篇 |
1999年 | 43篇 |
1998年 | 29篇 |
1997年 | 43篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有2819条查询结果,搜索用时 0 毫秒
1.
Abstract – Otoliths were used to explore the timing of annulus formation in Barbus sclateri. Lapillus exhibited opaque and translucent zones whose combination was formed once a year. Opaque zones appeared formed from July and January, and the translucent ones from February to June. We describe a procedure to assess age by using the number of annulii, the condition of the otolith's edge and the capture date. The use of otoliths for age determination in this cyprinid endemic to the Iberian Peninsula provides a useful alternative to the traditional methods of scale reading. Note 相似文献
2.
3.
P. Laffaille A. Acou J. Guillouët B. Mounaix A. Legault 《Ecology of Freshwater Fish》2006,15(4):583-588
Abstract – Changes in the numbers and size-class structure of European silver eels, Anguilla anguilla , in the River Frémur (France) were examined over a 9-year period after installation of downstream eel passes. The number of silver eels migrating downstream peaked in 1999, then decreased strongly and steadily after 2000, reaching relatively low levels. At the same time, a gradual shift in the silver eel sex ratio from a dominance of males (size from 270 to 442 mm, age from 3 to 6 years) to females (size from 366 to 1112 mm, age from 4 to 9 years) was recorded. Possible explanations for the escapement patterns observed are environmental sex determination and the installation of eel passes on the main hydraulic engineering structures in 1992 and 1996. 相似文献
4.
辣椒素类物质的测定、提取及应用研究进展 总被引:4,自引:0,他引:4
本文介绍了辣椒果实中辣椒素类物质的化学组成与结构,综述了国内外在辣椒素类物质的测定、提取及应用方面的研究情况。 相似文献
5.
Shahrbanou Hosseini Bertram Brenig Jens Tetens Ahmad Reza Sharifi 《Reproduction in domestic animals》2019,54(3):435-444
Ambient temperature during early stages of life has a substantial effect on physiological processes, eliciting phenotypic plasticity during zebrafish developmental stages. Zebrafish are known to possess a noteworthy ability to modify their phenotype in dependence of environmental factors. However, there is a poor understanding of the effects of temperature during embryogenesis, which influences the biological functions such as survival ability and masculinization in later developmental stages. Since the middle embryonic phase (pharyngula period) is genetically the most conserved stage in embryogenesis, it is very susceptible to embryonic lethality in developmental processes of vertebrates. Here, we tested the effect of transient perturbations (heat shock) during early development (5–24 hr post‐fertilization; hpf) at 35°C compared to control group at 28°C, on survival ability of zebrafish to study the embryonic and post‐embryonic mortality. We studied the variation of heat‐induced masculinization among and across the families in response to high temperature. Furthermore, morphometric traits of adult zebrafish at different developmental time points were measured in order to estimate the temperature × sex interaction effect. We found the highest embryonic mortality around the gastrula and segmentation periods in both experimental groups, with significantly lower survival ability in the temperature‐treated group (73.30% ± 0.58% vs. 70.19% ± 0.57%, respectively). A higher hatching success was observed in the control group (71.08% ± 0.61%) compared to the heat‐induced group (67.95% ± 0.60%). A distinct reduction in survival ability was also observed in both experimental groups during the first two weeks after hatching, followed by a reduced level of changes thereafter. We found sex ratio imbalances across all families, with 25.2% more males under temperature treatment. Our study on growth performance has shown a positive effect of increased temperature on growth plasticity, with a greater impact on female fish in response to high ambient temperature. 相似文献
6.
摘要:目的:为了开发灵芝黄酒,并提高南阳黄酒的知名度,本文测定了绍兴黄酒、南阳黄酒、和两种灵芝黄酒中基本营养元素的含量,并对其含量进行了比较。方法:用氨基酸自动分析仪对四种黄酒中的17种氨基酸进行了全面的定量分析;利用荧光法对四种黄酒中的维生素B1、维生素B2进行了定量分析;采用2,4-二硝基苯肼法检测不同黄酒中的维生素C的含量。结论:四种黄酒在基本营养成分含量上各有所长。 相似文献
7.
8.
9.
10.
草地植被冠层截留是草地生态系统对降水再分配的主要过程,属于草地生态系统蒸散发的组分之一。由于草地植被冠层截留常在草地生态系统水量平衡研究中被忽略而导致蒸散发组分的划分中存在误差。因此,讨论草地植被冠层截留对草地生态水文学的研究具有重要的理论意义和实用价值。本论文通过对目前草地植被冠层截留研究的现状和存在问题,从草地植被冠层截留的测定方法和主要的影响因素(环境因子和植被特征)2方面论述草地植被冠层截留的研究进展。分析发现,草地植被冠层截留的影响因素研究主要集中在降水特征、气象条件、放牧和植被特征等方面,各因素的综合影响研究仍然非常缺乏,测定方法的准确性有待评估。 相似文献