全文获取类型
收费全文 | 2586篇 |
免费 | 135篇 |
国内免费 | 307篇 |
专业分类
林业 | 378篇 |
农学 | 431篇 |
基础科学 | 225篇 |
519篇 | |
综合类 | 623篇 |
农作物 | 145篇 |
水产渔业 | 114篇 |
畜牧兽医 | 358篇 |
园艺 | 56篇 |
植物保护 | 179篇 |
出版年
2024年 | 4篇 |
2023年 | 25篇 |
2022年 | 57篇 |
2021年 | 97篇 |
2020年 | 106篇 |
2019年 | 80篇 |
2018年 | 44篇 |
2017年 | 73篇 |
2016年 | 80篇 |
2015年 | 117篇 |
2014年 | 130篇 |
2013年 | 137篇 |
2012年 | 174篇 |
2011年 | 197篇 |
2010年 | 151篇 |
2009年 | 149篇 |
2008年 | 154篇 |
2007年 | 155篇 |
2006年 | 136篇 |
2005年 | 148篇 |
2004年 | 58篇 |
2003年 | 69篇 |
2002年 | 41篇 |
2001年 | 39篇 |
2000年 | 43篇 |
1999年 | 77篇 |
1998年 | 71篇 |
1997年 | 57篇 |
1996年 | 65篇 |
1995年 | 57篇 |
1994年 | 37篇 |
1993年 | 36篇 |
1992年 | 29篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有3028条查询结果,搜索用时 234 毫秒
141.
Effects of dietary lipid level on growth performance,body composition and digestive enzymes activity of juvenile sea cucumber,Apostichopus japonicus 下载免费PDF全文
Ming‐Ling Liao Tong‐Jun Ren Wei Chen Yu‐Zhe Han Chen‐Min Liu Zhi‐Qiang Jiang Fu‐Qiang Wang 《Aquaculture Research》2017,48(1):92-101
A feeding trial aimed to determine the effects of dietary lipid level on growth performance, body composition and digestive enzymes activity of juvenile sea cucumber, Apostichopus japonicus. Diets with six crude lipid levels (1.9, 13.8, 29.1, 43.6, 59.6 and 71.6 g kg?1) were fed to sea cucumbers (initial weights 0.65 ± 0.01 g) at a density of 30 juveniles, once a day. After 60 days, body weight gain (BWG), specific growth rate (SGR), feed intake (FI) and protein efficiency ratio (PER) decreased with increasing dietary lipid levels. The sea cucumbers fed 1.9 g kg?1 crude lipid showed significantly higher (P < 0.05) BWG than those of the sea cucumbers fed 59.6 and 71.6 g kg?1 crude lipid. Intestinal protease and lipase activities generally increased with increasing dietary lipid levels. Eicosapentaenoic acid (EPA) content of body walls generally increased with increasing dietary lipid levels. Docosahexaenoic acid (DHA) content of body walls reached the maximum value at a dietary lipid level of 13.8 g kg?1. N‐3 highly unsaturated fatty acid content followed the same pattern of DHA. According to the growth performance and body composition of sea cucumbers, it can be indicated that the optimum dietary lipid level for juvenile sea cucumbers is between 1.9 and 13.8 g kg?1. 相似文献
142.
143.
西藏马铃薯育种现状、存在问题及发展方向 总被引:1,自引:0,他引:1
马铃薯是我区仅次于青稞、小麦、油菜之后的第四大作物,近年来,我区马铃薯生产发展迅速,种植面积逐年增加,各类马铃薯生产加工企业不断兴起。与此同时,生产中品种用途单一,专用品种缺乏的矛盾也逐步显露,这些都对我区马铃薯育种工作提出新的要求。 相似文献
144.
水稻白叶枯病抗性杂种优势 总被引:2,自引:0,他引:2
本试验采用双列式杂交方法,观察了以IR26、IR36等为代表的抗性品种的杂交优势。结果表明:杂交组合F1代在分蘖末期抗性无优势,穗期抗性优势明显;F2代两期鉴定正负向均有优势;F1和F2代均表现出正负向完全显性,部份显性,少数组合无显性。其中大都属于部份显性。优势指数分析也证明,对抗性亲本,优势指数d ≥ 1;对感病亲本,优势指数d<1。抗感品种杂交,其子代的抗性一般界于双亲值之间。这种优势可依亲本的抗性进行预测。 相似文献
146.
147.
JIA Zhan-jun YU Xue-qing WANG Xin LI Xiao-yan CHEN Wen-fang PENG Wen-xing DOU Xian-rui HAO Wen-ke SUN Liao ZHENG Zhi-hua YIN Pei-da 《园艺学报》2005,21(7):1298-1304
AIM: To observe the effect of antibiotic treatment on the inflammatory mediator expression in peritoneum and the peritoneal transport function in rats with acute peritonitis, and explore its mechanisms. METHODS: Eighty-six SD rats were randomly divided into three groups. Control group (n=28) were treated with PBS (ip), peritonitis group (n=28) and treatment group (n=28) were challenged with the E.coli (ip), but at 3 h and 9 h gentamicin was given (ip) in treatment group. Seven rats of every group were randomly sacrificed at 24 h, 48 h, 72 h and 7 d. Peritoneal equilibration test (PET) was did before they were killed. Leukocyte count, pathological changes and the expression of CD45, NF-κB, IL-1β, TNF-α in peritoneum were examined. RESULTS: (1)The blood leukocytes in peritonitis group decreased strikingly, but did not change obviously in other two groups. The peritoneal fluid leukocytes in peritonitis group increased significantly from 24 h to 72 h, while in treatment group, it enhanced more strikingly than peritonitis group at 24 h, and recovered earlier. (2) Both in peritonitis group and treatment group, the expression of activated NF-κB, IL-1β, TNF-α and CD45 increased significantly, but the treatment group was lower than model group at 48 h and 72 h. The mRNA level of IL-1β and TNF-α had the same trend as their protein expression. (3) Compared with the control group, UF and D/D0 Glu decreased significantly in model group and treatment group, and D/PTP increased dramatically. The D/P TP in treatment group lowered obviously compared with peritonitis group, while the net UF and D/D0 Glu had not significant difference between treatment group and model group. CONCLUSION: Antibiotic treatment can partly decrease the expression of inflammatory mediators in peritoneum of rats with acute peritonitis and also can improve the protein transport ability to some extent, but can not improve the peritoneal ultrafiltration and the glucose transport function. 相似文献
148.
11999年小麦条锈病流行特点 1)见病早,侵染时间长。秋苗上病害始见期早于常年,一般提早10d到3个月。 2)扩散蔓延速度快。1月4日统计全省发病面积为3.0万hm2,到1月底即发展到6.7万hm2。3月3日达16.7万hm2,3月底增至38万hm2,4月23日为58.5万hm2。其扩散蔓延速度之快实属历史罕见。 3)病害垂直扩散迅速,病情严重。乐至县3月初调查,病田率为64.3%,病株率平均11.9%,病叶率平均3.85%,分别较1周前上升2.0倍、20.0倍、24.7倍。3月23日调查,病株率又上升1.6倍,病叶率上升3.6倍,平均严重程度达21.8%。 4)流行区域大,所… 相似文献
149.
美国优良牧草引种及其利用初探 总被引:1,自引:0,他引:1
本文论述从美国俄勒岗淋巴恩布莱格公司引进36个优良牧草品种,并在福建省上杭县试种筛选的过程。探索在本地区栽培管理这批优良牧草技术及预测在我国南方利用发展前景。 相似文献
150.
Protective effects of oral microencapsulated Mycoplasma hyopneumoniae vaccine prepared by co-spray drying method 总被引:2,自引:0,他引:2
Lin JH Weng CN Liao CW Yeh KS Pan MJ 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2003,65(1):69-74
The efficacy of Mycoplasma hyopneumoniae oral vaccine was investigated in microsphere dosage form. A co-spray drying process was used to apply an encapsulating material, Eudragit L30 D-55, to microspheres containing Mycoplasma hyopneumoniae antigens. The microspheres were generally effective (>93%) with protein release at pH 7.4, but almost none were released at pH 1.2, for 3 hr in an in vitro dissolution test. An SPF-swine model was used to evaluate the effectiveness of the microspheres as an oral vaccine, and the related immune responses. The serum's systemic IgG against M. hyopneumoniae was evoked by ELISA analysis, after a 2nd immunization of all pigs. The vaccinated groups' mean lesion score was significantly lower after the Mycoplasma hyopneumoniae challenge than that of the nonvaccinated/challenged groups (P<0.05). This study strongly suggests that the oral microspheres vaccine prepared by a co-spray drying method can provide effective protection against M. hyopneumoniae infection in pigs. 相似文献