全文获取类型
收费全文 | 801篇 |
免费 | 52篇 |
国内免费 | 33篇 |
专业分类
林业 | 77篇 |
农学 | 73篇 |
基础科学 | 11篇 |
24篇 | |
综合类 | 195篇 |
农作物 | 161篇 |
水产渔业 | 70篇 |
畜牧兽医 | 259篇 |
园艺 | 14篇 |
植物保护 | 2篇 |
出版年
2024年 | 4篇 |
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 22篇 |
2020年 | 31篇 |
2019年 | 16篇 |
2018年 | 22篇 |
2017年 | 26篇 |
2016年 | 21篇 |
2015年 | 28篇 |
2014年 | 43篇 |
2013年 | 43篇 |
2012年 | 31篇 |
2011年 | 33篇 |
2010年 | 32篇 |
2009年 | 56篇 |
2008年 | 43篇 |
2007年 | 69篇 |
2006年 | 42篇 |
2005年 | 28篇 |
2004年 | 33篇 |
2003年 | 24篇 |
2002年 | 19篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 22篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有886条查询结果,搜索用时 7 毫秒
881.
Yingying Liu Xiangfeng Kong Guoli Jiang Bi’e Tan Jinping Deng Xiaojian Yang Fengna Li Xia Xiong Yulong Yin 《畜牧与生物技术杂志(英文版)》2015,6(1)
Background
The protein/energy ratio is important for the production performance and utilization of available feed resources by animals. Increased protein consumption by mammals leads to elevated feed costs and increased nitrogen release into the environment. This study aimed to evaluate the effects of dietary protein/energy ratio on the growth performance, carcass traits, meat quality, and plasma metabolites of pigs of different genotypes.Methods
Bama mini-pigs and Landrace pigs were randomly assigned to two dietary treatment groups (Chinese conventional diet with low protein/energy ratio or National Research Council diet with high protein/energy ratio; n = 24 per treatment) in a 2 × 2 factorial arrangement. Blood and muscle samples were collected at the end of the nursery, growing, and finishing phases.Results
We observed significant interactions (P < 0.05) between breed and diet for total fat percentage, intramuscular fat (IMF) content, protein content in biceps femoris (BF) muscle, and plasma urea nitrogen (UN) concentration in the nursery phase; for average daily gain (ADG), average daily feed intake (ADFI), dry matter, IMF content in psoas major (PM) muscle, and plasma total protein and albumin concentrations in the growing phase; and for drip loss and plasma UN concentration in the finishing phase. Breed influenced (P < 0.05) growth performance, carcass traits, and meat quality, but not plasma metabolites. Throughout the trial, Landrace pigs showed significantly higher (P < 0.05) ADG, ADFI, dressing percentage, lean mass rate, and loin-eye area than did Bama mini-pigs, but significantly lower (P < 0.05) feed/gain ratio, fat percentage, backfat thickness, and IMF content. Dietary protein/energy ratio influenced the pH value, chemical composition of BF and PM muscles, and plasma activities of glutamic-pyruvic transaminase and gamma-glutamyl transpeptidase, and plasma concentration of UN.Conclusions
Compared with Landrace pigs, Bama mini-pigs showed slower growth and lower carcass performance, but had better meat quality. Moreover, unlike Landrace pigs, the dietary protein/energy ratio did not affect the growth performance of Bama mini-pigs. These results suggest that, in swine production, low dietary protein/energy ratio may be useful for reducing feed costs and minimizing the adverse effects of ammonia release into the environment.Electronic supplementary material
The online version of this article (doi:10.1186/s40104-015-0036-x) contains supplementary material, which is available to authorized users. 相似文献882.
Quantitative trait loci mapping of forage stover quality traits in six mapping populations derived from European elite maize germplasm 下载免费PDF全文
Pengfei Leng Milena Ouzunova Matthias Landbeck Gerhard Wenzel Joachim Eder Birte Darnhofer Thomas Lübberstedt 《Plant Breeding》2018,137(2):139-147
Four forage maize stover quality traits were analysed including in vitro digestibility of organic matter (IVDOM), neutral detergent fibre (NDF), water‐soluble carbohydrates (WSC) and digestibility of NDF (DNDF). We mapped quantitative trait loci (QTL) in three DH (doubled haploid) populations (totally 250–720 DH lines): one RIL population (358 lines) and two testcross (TC) populations, based on field phenotyping at multiple locations and years for each. High phenotypic and genotypic correlations were found for all traits and significant (p < .01) at two locations, and NDF was negatively correlated with the other traits. QTL analyses were conducted by composite interval mapping. A total of 33, 23, 32 and 25 QTL were identified for IVDOM, NDF, WSC and DNDF, respectively, with three, four, five and two major QTL for each. Few consistent QTL for IVDOM, WSC and DNDF were detected in more than two populations. This study contributed to the identification of key QTL associated with forage maize digestibility traits and is beneficial for marker‐assisted breeding and fine mapping of candidate genes associated with forage maize quality. 相似文献
883.
Effect of support medium,hydraulic loading rate and plant density on water quality and growth of halophytes in marine aquaponic systems 下载免费PDF全文
Suzanne E Boxman Michael Nystrom Joseph C Capodice Sarina J Ergas Kevan L Main Maya A Trotz 《Aquaculture Research》2017,48(5):2463-2477
The development of marine intensive land‐based aquaculture systems has been limited due to the absence of methods to manage saline wastewater. Aquaponic systems, although commonly applied to freshwater aquaculture, can potentially manage nutrient wastes while providing a secondary product. The aim of this study was to evaluate both the capacity for water treatment and the production requirements of two saltwater‐tolerant plant species (Sesuvium portulacastrum and Batis maritima) when grown hydroponically in a marine aquaponic system. The presence of plants was found to significantly contribute to nitrate removal, such that mean nitrate concentrations were 10.1 ± 5.4 and 12.1 ± 6.1 mg/L NO3?‐N in planted and unplanted treatments respectively. The use of coconut fibre as a planting medium also significantly contributed to nitrate removal, such that mean nitrate concentrations were 9.78 ± 5.4 and 12.4 ± 6.0 mg/L NO3?‐N in coconut fibre and expanded clay treatments respectively. Daily nitrogen removal was greatest in the coconut fibre/plants treatment, ranging from ?18% to 67%. Hydraulic loading rate, plant species and plant density did not significantly affect water quality or plant growth. The low flow/saltwort/low density treatment had the greatest mean daily nitrogen removal, ranging from 25% to 172%. The results indicate that the main nitrogen removal mechanisms were simultaneous nitrification–denitrification in the hydroponic plant beds and nitrogen removal through plant growth. This study demonstrates that marine aquaponics could be an effective way to manage nutrient removal in marine land‐based aquaculture systems. 相似文献
884.
Hesam A. Seifi Mehrdad Mohri Nima Farzaneh Shima Vahidi Nejhad 《Research in veterinary science》2010,89(1):72-77
The objectives of this study were to determine the effects of a pre-partum diet with lower than recommended (DCAD = −82 mEq/kg of dietary DM) amounts of anionic salts on metabolism, health, reproductive performance and milk production in dairy cows. Sixty Holstein multiparous cows were enrolled 21 days prior to expected calving date. The animals were randomly assigned to receive one of two rations: 30 cows received anionic ration [−82 mEq (NA + K − Cl − S)/kg of DM] for 21 d to parturition and the other group (n = 30) were fed a usual dry period ration (+192 mEq/kg of DM). Serum samples obtained at days −21, +3 and +21 relative to calving were analyzed for β-hydroxybutyrate (BHBA), non-esterified fatty acids (NEFA), glucose, calcium (Ca), inorganic phosphorus, magnesium, chloride, sodium, potassium, cholesterol, urea, creatinine, total protein, albumin, and aspartate aminotransferase (AST). Urine pH declined from 8.4 at 21 d before calving (pre-treatment) to 6.2 at day 7 pre-partum in the treatment group. Repeated-measure mixed model analysis indicated that the concentrations of Ca were significantly increased and creatinine, and AST were significantly decreased by lowering DCAD. The concentrations of BHBA, NEFA and glucose were not affected by treatment. The incidence of milk fever and culling were 5 and 11 times higher in the control group in comparison with the treatment group, respectively. The intervals from calving to first breeding and to pregnancy were not influenced by treatment. There was no group effect on average daily milk yield or fat percentage. 相似文献
885.
Maternal dietary linoleic acid supplementation promotes muscle fibre type transformation in suckling piglets 下载免费PDF全文
X. H. Zhou X. F. Yu J. Huang D. Y. Yu X. X. Wang Y. Z. Wang 《Journal of animal physiology and animal nutrition》2017,101(6):1130-1136
As meat quality is basically dependent on muscle fibre characteristics, it is important to know how muscle fibres are regulated and transformed. This study aimed to investigate the effect of maternal dietary supplementation on muscle fibre types using 3% saturated fatty acid (palmitic acid, PA) or 3% unsaturated fatty acid (linoleic acid, LA) from 80 days of gestation to the weaning of offspring (25 days post‐natal). The results indicated that higher mRNA levels of MyHCI type genes were found in the soleus muscles of piglets that suckled from LA‐supplemented sows than from PA‐supplemented sows. In addition, LA treatment increased the gene expression of the type I muscle fibre marker troponin I (p < 0.01), suggesting that LA promoted muscle fibre type transformation to type I fibres. Moreover, PGC‐1α (p < 0.01) and MEF2c (p < 0.05) mRNA levels were higher in the piglets from the LA treatment group than in those from the PA treatment group. Furthermore, LA supplementation also significantly increased AMP‐activated protein kinase (AMPK) mRNA levels (p < 0.05), which is an upstream regulator of PGC‐1α. Collectively, these findings demonstrated that maternal dietary LA supplementation promoted muscle fibre transformation to type I fibre and that this process may be mediated through an AMPK‐dependent pathway. 相似文献
886.
麦麸膳食纤维对有机磷农药的吸附作用 总被引:8,自引:0,他引:8
为探明依靠食物防止和缓和农药毒害的可能性,进行了麦麸膳食纤维对2种有机磷农药甲胺磷和敌敌畏的吸附试验研究,结果表明,麦麸水不溶性膳食纤维对农药具有一定的吸附能力,且不同组分对农药的吸附作用存在很大差异,木质素的吸附能力较强,能将农药剂量吸附安全水平,降低农药引家蝇死亡率,而麦殖水溶性膳食纤维无此作用。 相似文献