全文获取类型
收费全文 | 25437篇 |
免费 | 1407篇 |
国内免费 | 2547篇 |
专业分类
林业 | 2972篇 |
农学 | 3381篇 |
基础科学 | 1893篇 |
4130篇 | |
综合类 | 8057篇 |
农作物 | 1639篇 |
水产渔业 | 1231篇 |
畜牧兽医 | 3337篇 |
园艺 | 1048篇 |
植物保护 | 1703篇 |
出版年
2024年 | 65篇 |
2023年 | 345篇 |
2022年 | 788篇 |
2021年 | 1045篇 |
2020年 | 1004篇 |
2019年 | 989篇 |
2018年 | 714篇 |
2017年 | 950篇 |
2016年 | 920篇 |
2015年 | 1237篇 |
2014年 | 1184篇 |
2013年 | 1463篇 |
2012年 | 1758篇 |
2011年 | 1831篇 |
2010年 | 1659篇 |
2009年 | 1464篇 |
2008年 | 1465篇 |
2007年 | 1318篇 |
2006年 | 1241篇 |
2005年 | 1072篇 |
2004年 | 625篇 |
2003年 | 466篇 |
2002年 | 413篇 |
2001年 | 419篇 |
2000年 | 498篇 |
1999年 | 602篇 |
1998年 | 555篇 |
1997年 | 477篇 |
1996年 | 386篇 |
1995年 | 396篇 |
1994年 | 335篇 |
1993年 | 346篇 |
1992年 | 280篇 |
1991年 | 261篇 |
1990年 | 188篇 |
1989年 | 156篇 |
1988年 | 147篇 |
1987年 | 96篇 |
1986年 | 50篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1968年 | 6篇 |
1964年 | 6篇 |
1963年 | 6篇 |
1956年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 37 毫秒
11.
12.
13.
为明确垦稻26和龙粳31高产优质栽培的株行距和穴苗数处理,采取裂区设计进行试验研究。结果表明,最优群体因品种而异,垦稻26在株距10cm、行距30cm、5苗/穴产量最佳,龙粳31则以株距13.3cm、行距27cm、9苗/穴产量最佳;垦稻26在5苗/穴、行株距30cm×10cm处理,有利于提高稻米的碾磨品质,不利于改善稻米的外观品质,营养品质较低,利于改善稻米的食味品质,且食味评分值高达86.5,显著高于最低处理;龙粳31在5苗/穴、行株距27cm×13.3cm处理,碾磨品质较高,不利于营养品质和外观品质的改善,食味品质得到明显改善,食味评分值高达86.0,与最低处理差异达显著水平。因此,高产优质栽培要因品种选择适宜的穴苗数和株行距,是实现水稻高产优质最为快捷、最为经济有效的措施。 相似文献
14.
15.
16.
以光肩星天牛的发生规律和危害特征为基础,应用引诱剂对其成虫进行动态监测,根据监测数据并结合其生活习性确定防治适期和防治方法,为光肩星天牛的监测和防治提供参考。 相似文献
17.
李超 《农业图书情报学刊》2018,30(9):100-105
大数据环境的变化,不仅改变了用户的信息行为,也使得数字图书馆服务朝着越加个性化、知识化、多元化的角度不断发展,由此带动了数字图书馆资源特征与服务特征的适应性的变化,促使数字图书馆朝着创新服务模式、融合服务元素、拓展服务功能、知识化建设、精确化服务等角度的转型发展,也包括数字图书馆自身对于服务力量的不断强化和服务展现形式的多元化等方面的转型发展,推动数字图书馆不断改变原有的服务范式而朝着更加个性化、知识化和技术化的角度不断发展。 相似文献
18.
Shi-Zhi Wang Guang-Xin E Yan Zeng Yan-Guo Han Yong-Fu Huang Ri-Su Na 《Reproduction in domestic animals》2021,56(6):936-941
The aim of this study was to analyse the association between single-nucleotide polymorphisms within INHA and ACVR2B and litter size in Dazu black goats. In total, twenty-two SNPs were genotyped in 190 individuals by SNaPshot and resequencing. The results showed that three SNPs (SNP_1, SNP_12 and SNP_13 in this study) were detected to have significant additive genetic effect on the recorded goat litter size (p < .05). The SNP_1 (NC_030809.1), a non-synonymous substitution of G for T at chr2-g. 28314990 in the exon 2 of INHA gene (NM_001285606.1), resulted in homozygote 2 (HOM2) contributed 0.25 and heterozygote (HET) contributed 0.12 larger litter than homozygote 1 (HOM1). Meanwhile, SNP_12 (Chr22-g. 11721225 A > T) and SNP_13 (Chr22-g. 11721227 A > C) (NC_030829.1) simultaneously mutated at the first and third position of a triplet AAA (lysine, K) in the exon 4 of ACVR2B gene (XM_018066623.1) had estimated genetic effects of HOM1 (0.00) and HOM2 (0.03) larger than HET (−0.12). In conclusion, one SNPs (chr2-g. 28314990 T > G) within the exon 2 of INHA and two SNPs (Chr22-g. 11721225 A > T and Chr22-g. 11721227 A > C) i n the exon 4 of ACVR2B gene were highly recommended as candidate markers of litter size in Dazu black goats. A large-scale association study to assess the impact of these variants on litter size is still necessary. 相似文献
19.
20.
Ruimin Chao Chengqiang Xia Caixia Pei Wenjie Huo Qiang Liu Chunxiang Zhang Youshe Ren 《Journal of animal physiology and animal nutrition》2021,105(1):26-34
The objective of this study was to investigate the characteristics of ruminal microbial communities of alpacas (Lama pacos) and sheep (Ovis aries) fed three diets with varying ratios of roughage (corn stalk) to concentrate, 3:7 (LS), 5:5 (MS) and 7:3 (HS). Six alpacas (one-year-old and weighing 29.5 ± 7.1 kg) and six sheep (one-year-old and weighing 27.9 ± 2.7 kg) were used in this study, in a replicated 3 × 3 Latin square experiment. Total protozoa concentration was determined under the microscope; total fungi and methanogens were assessed using quantitative polymerase chain reaction and expressed as a percentage of total bacterial 16S rRNA gene copies; bacterial communities were investigated by targeted 16S rRNA gene (V3–V4 region) sequencing. The percentage of fungi was significantly higher in alpacas than in sheep under the LS diet, while the concentration of protozoa was significantly lower in alpacas under HS, MS and LS diets. The alpha diversity including Shannon, Chao l and ACE indices of bacterial communities was higher in alpacas than in sheep, under the LS diet. A total of 299 genera belonging to 22 phyla were observed in the forestomach of alpaca and sheep, with Bacteroidetes and Firmicutes dominating both animal species. Phyla Armatimonadetes and Fusobacteria, as well as 64 genera, were detected only in alpacas, whereas phyla Acidobacteria and Nitrospira, as well as 44 genera, were found only in sheep. The abundance of cellulolytic bacteria, including Butyrivibrio and Pseudobutyrivibrio, was higher in alpacas than in sheep under all three diets. These differences in the forestomach microbial communities partly explained why alpacas displayed a higher poor-quality roughage digestibility, and a lower methane production. Results also revealed that the adverse effects of high-concentrate diets (70%) were lesser in alpacas than in sheep. 相似文献