全文获取类型
收费全文 | 96429篇 |
免费 | 3659篇 |
国内免费 | 9162篇 |
专业分类
林业 | 13247篇 |
农学 | 14196篇 |
基础科学 | 7774篇 |
16089篇 | |
综合类 | 24581篇 |
农作物 | 5991篇 |
水产渔业 | 4597篇 |
畜牧兽医 | 12037篇 |
园艺 | 3811篇 |
植物保护 | 6927篇 |
出版年
2024年 | 220篇 |
2023年 | 859篇 |
2022年 | 2242篇 |
2021年 | 3160篇 |
2020年 | 2946篇 |
2019年 | 2877篇 |
2018年 | 4489篇 |
2017年 | 5246篇 |
2016年 | 3818篇 |
2015年 | 3623篇 |
2014年 | 3469篇 |
2013年 | 4291篇 |
2012年 | 5785篇 |
2011年 | 7558篇 |
2010年 | 7181篇 |
2009年 | 6090篇 |
2008年 | 5993篇 |
2007年 | 6173篇 |
2006年 | 4551篇 |
2005年 | 4037篇 |
2004年 | 2018篇 |
2003年 | 1869篇 |
2002年 | 1449篇 |
2001年 | 1549篇 |
2000年 | 1823篇 |
1999年 | 2027篇 |
1998年 | 2018篇 |
1997年 | 1674篇 |
1996年 | 1530篇 |
1995年 | 1449篇 |
1994年 | 1282篇 |
1993年 | 1219篇 |
1992年 | 1035篇 |
1991年 | 852篇 |
1990年 | 744篇 |
1989年 | 639篇 |
1988年 | 493篇 |
1987年 | 287篇 |
1986年 | 184篇 |
1985年 | 86篇 |
1984年 | 78篇 |
1983年 | 66篇 |
1982年 | 54篇 |
1981年 | 48篇 |
1980年 | 32篇 |
1979年 | 23篇 |
1977年 | 11篇 |
1965年 | 14篇 |
1964年 | 15篇 |
1963年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
RFamide‐related peptide‐3 (RFRP‐3), the mammalian ortholog of gonadotropin‐inhibiting hormone, has been implicated as a mediator between reproduction and energy balance. This study aimed to investigate the physiological effects of RFRP‐3 on the process of ovarian development in food‐restricted pre‐pubertal ewes. The results showed that food restriction significantly inhibited the ovarian development and follicular growth. The data of qPCR in the hypothalamic–pituitary–ovarian (HPO) axis showed that food restriction not only upregulated RFRP‐3 mRNA expression but also downregulated the mRNA expression of gonadotropin‐releasing‐hormone receptor, follicle‐stimulating hormone receptor and luteinizing hormone receptor (LHR). Immunohistochemistry of RFRP‐3 in the ovaries suggested that RFRP‐3 may regulate the follicular development. These results suggested that the changes of RFRP‐3 in response to food restriction might influence the HPO axis and inhibit ovarian development. 相似文献
92.
93.
<正>纤维素酶具有破坏植物细胞壁,促进营养物质的消化和吸收,消除抗营养因子,提高饲料营养价值等多种功能,因而成为饲料工业研究的热点。目前用于纤维素酶生产和研究的菌株多为霉菌。棘孢木霉是我国新记录的木霉种[1],目前国内尚未见该菌种产纤维素酶的文献报道。 相似文献
94.
不同铁源对仔鸡生长的影响 总被引:3,自引:0,他引:3
选取1日龄罗曼蛋公鸡90只,随机分为3组,每组30只。以玉米、大豆分离蛋白为主要成分的半纯合基础日粮,在基础日粮中分别添加硫酸亚铁(含铁30%)、蛋氨酸铁(含铁10%)和甘氨酸铁(含铁10%)3种铁源,使铁含量各为80mg/kg,组成对照组和试验Ⅰ组、Ⅱ组。试验期为28d。28日龄时停饲24h后称重屠宰,取内脏器官,结果表明,蛋氨酸铁促进仔鸡体重的增加和内脏器官的发育,在21和28日龄时体重比对照组分别提高了10.57%和14.94%;甘氨酸铁组与对照组相比,差异不显著,但在一定程度上可以促进仔鸡体重的增加和内脏器官的发育。 相似文献
95.
试验选用1日龄AA肉仔鸡180只,随机分为3组。Ⅰ组为对照组,添加硫酸锰(MnSO4·H2O)120mg/kg;Ⅱ组添加蛋氨酸螫合锰60mg/kg;Ⅲ组分别添加蛋氨酸螯合锰(Met-Mn)30mg/kg和硫酸锰(MnSO4·H2O)60mg/kg。研究不同方式添加锰对肉仔鸡生产性能的影响。结果表明.3种不同方式添加锰对肉仔鸡生产性能无显著影响(P〉0.05).但Ⅲ组的饲料成本有所降低。因此,在肉仔鸡日粮中以第3种方式添加效果最佳。 相似文献
96.
Research in control of tick-borne diseases and trypanosomosis, and their vectors, namely, ticks and tsetse flies respectively,
has been on going for decades. However, very little attention has been paid to the socio-economic factors that are likely
to influence the outcome of the interventions in the control of these diseases. Thus, this study was designed to investigate
these factors, mainly the intra-household factors influencing decision-making in the control of Vector-borne diseases in the
pastoralist areas of Uganda. These factors included: indigenous technical knowledge, household economic factors, and gender.
Both qualitative and quantitative methods were used in the collection and analysis of data. The tools used for data collection
included among others, participatory learning and action (PLA), and Case studies. The findings included the following: In
pastoralist households, a big proportion of the household budget was allocated to vector-borne diseases control. In the male-headed
households, men dominated decision-making on vector-borne diseases control, although the goals and priorities of men and women
in these households were not the same. Also, vector-borne disease control was predominantly by use of modern veterinary drugs,
and pastoralists treated sick cattle by themselves even in situations where there were veterinary personnel. 相似文献
97.
98.
Xiaolong Wang Kehe Huang Jingbao Gao Xiangzhen Shen Chengyi Lin Gengdi Zhang 《Research in veterinary science》1997,62(3):275
The chemical composition and microstructure of seven uroliths and four urinary sediment samples associated with the feeding of high-level cottonseed meal diet to buffalo calves were examined by chemical qualitative analyses, scanning electron microscopy (
), X-ray diffraction, and X-ray energy dispersive spectrometry (
). Struvite was a major component of kidney stones and of some bladder stones. The kidney stone sample appeared cracked under low power under
, aggregated into tiny balls under high power, and as a bladelike structure under even higher power. The bladder stone samples appeared finely granular or granular with various forms of prismatic crystals. The urinary sediments were prismatic crystals, with granules. The newly found prismatic crystals, which were rich in potassium and similar to struvite in crystal structure, were identified as potassium magnesium phosphate (KMgPO4 · 6H2O) in some bladder stones and urinary sediments. However, crystals which contained Mg and P only, which had been used for struvite identification, were not found by
examination in urinary sediments from fresh urine samples of buffalo calves fed the high-level cottonseed meal diet. 相似文献
99.
用从自然感染宿主分离的伊氏锥虫原种JG的克隆JGmc1和JGmc5感染免疫活性正常小鼠和免疫抑制小鼠,24h后,以苏拉灭或贝尼尔治疗,两种药物对免疫抑制小鼠的CD100均明显高于免疫活性正常小鼠,由经受一次苏拉灭或贝尼尔治疗未愈的免疫抑制小鼠分离的锥虫,感染免疫活性正常小鼠,再用原来对该克隆感染的免疫活性正常小鼠CD100的苏拉灭或贝尼尔治疗即无效。用免疫溶解试验分别测定一组免疫抑制和免疫活性正确 相似文献
100.