全文获取类型
| 收费全文 | 9107篇 |
| 免费 | 545篇 |
| 国内免费 | 598篇 |
专业分类
| 林业 | 470篇 |
| 农学 | 638篇 |
| 基础科学 | 213篇 |
| 1245篇 | |
| 综合类 | 2557篇 |
| 农作物 | 633篇 |
| 水产渔业 | 538篇 |
| 畜牧兽医 | 2849篇 |
| 园艺 | 437篇 |
| 植物保护 | 670篇 |
出版年
| 2024年 | 34篇 |
| 2023年 | 106篇 |
| 2022年 | 184篇 |
| 2021年 | 231篇 |
| 2020年 | 220篇 |
| 2019年 | 234篇 |
| 2018年 | 228篇 |
| 2017年 | 296篇 |
| 2016年 | 259篇 |
| 2015年 | 262篇 |
| 2014年 | 331篇 |
| 2013年 | 476篇 |
| 2012年 | 566篇 |
| 2011年 | 641篇 |
| 2010年 | 548篇 |
| 2009年 | 478篇 |
| 2008年 | 525篇 |
| 2007年 | 519篇 |
| 2006年 | 427篇 |
| 2005年 | 359篇 |
| 2004年 | 325篇 |
| 2003年 | 365篇 |
| 2002年 | 494篇 |
| 2001年 | 479篇 |
| 2000年 | 321篇 |
| 1999年 | 197篇 |
| 1998年 | 44篇 |
| 1997年 | 47篇 |
| 1996年 | 35篇 |
| 1995年 | 46篇 |
| 1994年 | 46篇 |
| 1993年 | 39篇 |
| 1992年 | 50篇 |
| 1991年 | 40篇 |
| 1990年 | 54篇 |
| 1989年 | 52篇 |
| 1988年 | 36篇 |
| 1987年 | 40篇 |
| 1986年 | 31篇 |
| 1985年 | 34篇 |
| 1984年 | 51篇 |
| 1983年 | 27篇 |
| 1982年 | 26篇 |
| 1979年 | 28篇 |
| 1978年 | 28篇 |
| 1977年 | 27篇 |
| 1975年 | 25篇 |
| 1974年 | 37篇 |
| 1972年 | 30篇 |
| 1971年 | 37篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
71.
种植耐盐性强的桑树品种是土壤盐渍化地区生态修复的技术途径之一.选择桂桑优12、桂桑优62、抗青283×抗青10、桂桑5号、桂桑6号、桑特优2号共6个桑树品种的实生苗供试,将供试桑苗种植于质量浓度分别为0 g/L(CK)、2 g/L、4 g/L、6 g/L的NaCl溶液中,在历时28 d的盐胁迫试验期,每隔7d测定和统计各处理组桑苗的枝高、叶片数量、最大叶长、最大叶宽、受害叶片数量和枯死植株数量等,初步评价供试桑品种实生苗对盐胁迫的耐受能力.结果表明:在不同浓度盐胁迫处理组桑苗生长均较好的桑树品种是桂桑优12和桑特优2号;桑苗受盐害指数和死亡率最低的桑树品种均是桂桑优12.试验结果提示,6个供试桑树品种中桂桑优12是耐盐性最强的品种. 相似文献
72.
为研究不同利用方式对藏北高寒草甸建植一年生燕麦（Avena sativa Linn.）人工草地的土壤理化性质及土壤细菌群落的影响,本试验于8月份植物生长旺季,在持续利用人工草地（AG）、撂荒人工草地（AC）和对照天然草地（NG）采集土壤样品,分析了土壤理化性质、土壤细菌群落组成和结构特征变化。结果表明,AG样地土壤有机质、全钾含量和pH与NG样地相比无显著性变化,土壤全氮、速效氮和速效钾含量显著降低;AC样地与NG样地相比土壤pH显著升高,土壤有机质、全氮、速效氮和速效钾含量显著降低。AG样地土壤细菌群落Chao1,Shannon和Pielou均匀度指数显著高于NG样地,AC样地酸杆菌门和变形菌门丰度显著升高。土壤理化性质是土壤细菌群落结构组成门、属相对丰度变化主要影响因子。综上所述,高寒草甸一年生燕麦人工草地长期利用应科学补充肥料,保持土壤肥力;草地撂荒需谨慎,应及时采取恢复措施避免草地发生退化。 相似文献
73.
本试验旨在探明绵羊感染16型蓝舌病病毒（Bluetongue virus type 16,BTV16）后细胞因子IFN-γ、IL-2、IL-4和IL-10的消长特点。用实时荧光定量PCR检测方法对感染BTV16后3只绵羊上述4种因子mRNA进行检测,同时设立阴性对照绵羊,并以0 d mRNA为基准,计算mRNA的相对表达量,同时检测病毒抗体效价、测量绵羊体温。结果显示,接种BTV16的3只绵羊均不同程度产生抗体和体温症状,4种细胞因子的mRNA在接种病毒2~4 d内均出现显著上升,其中IFN-γ峰值在2.58~27.84倍之间,IL-2峰值在5.24~17.19倍之间,IL-4峰值在2.16~3.43倍之间,IL-10峰值在15.78~48.77倍之间,个体上升幅度存在显著差异,4种细胞因子均在高水平持续6 d左右后逐渐下降。对照绵羊上述参数在正常范围内波动。本研究阐明了接种BTV16后绵羊细胞因子IFN-γ、IL-2、IL-4、IL-10在转录水平上的消长特点,为进一步深入开展BTV感染特征、宿主机体免疫机制研究提供参考。 相似文献
74.
为确定奶牛垫料中是否含有病原菌并深入了解垫料中优势生长菌的类型、耐药性及致病性等情况,本试验进行了细菌分离培养、革兰染色镜检、生化试验鉴定、16S rDNA序列分析及同源性比对、药敏试验、小鼠致病性试验。结果显示,分离菌在普通营养琼脂平板上形成圆形、表面光滑的白色菌落,血琼脂平板上形成黏稠、较大的白色菌落。革兰染色镜检结果显示,分离菌为革兰阳性,球型,呈葡萄串状排列,或单个散落。生化试验结果显示,分离菌对木糖、葡萄糖、麦芽糖、果糖、乳糖、硝酸盐还原等呈阳性反应,而蜜二糖、木糖醇、山梨醇、尿素、V-P反应等呈阴性反应。16S rDNA序列分析结果显示,扩增的16S rDNA序列长度为1 298 bp,与松鼠葡萄球菌的核苷酸同源性达99.85%~100%;系统进化树结果显示,分离菌与松鼠葡萄球菌处于同一分支。动物试验结果表明,分离菌株对试验小鼠有较强的致病性,以0.2 mL/只（7.9×108 CFU/mL）菌液的剂量接种小鼠,在48 h内死亡率为60%（3/5）。药敏特性分析结果显示,分离菌株对复方新诺明、氨苄西林等7种药物敏感,对克林霉素、头孢噻肟和头孢呋辛中度敏感,对青霉素、红霉素和林可霉素耐药。本研究为奶牛源松鼠葡萄球菌的分离鉴定及防控提供了参考依据。 相似文献
75.
为探究肌生长抑制素（myostatin,MSTN）基因对牛肌肉发育的具体调控机制,本研究选取同一牛场健康鲁西黄牛10头,其中通过转基因技术得到的基因编辑牛MSTN-/-和同种非转基因野生型牛各5头。分别采集两组牛腿臀肌肉样品,利用IIlumina HiSeq高通量测序技术进行转录组测序分析,通过生物信息学方法比较两组样本间的差异表达基因,并进行GO和KEGG富集分析,最后利用实时荧光定量PCR验证转录组测序数据。结果显示,基因编辑型牛和野生型牛之间共检测到18 071个基因。在log2|FoldChange|≥ 1.48条件下,筛选出406个差异表达基因,其中347个显著上调,59个显著下调。GO功能富集分析显示,MSTN基因编辑后显著影响915个功能类别（P<0.05）,差异基因主要参与结合、生物系统调节、免疫系统等相关功能。KEGG通路富集分析结果共涉及211个通路,差异基因主要富集在细胞黏附分子、趋化因子信号通路、细胞因子互作等信号通路上,进一步从中筛选出可能参与细胞生长、肌肉发育的差异基因（CD14、KIT、CSF1R、FBP1、DUSP4、ULBP21、PRKCB、SPN、CHAD、SRC）。实时荧光定量PCR检测结果显示,所选差异基因表达水平与转录组表达水平一致,证明测序结果的可靠性。本研究结果表明,MSTN基因发挥作用后可以介导多个下游基因表达,从而影响相关信号通路及生物学过程;同时,所筛选出的差异表达基因可作为进一步研究骨骼肌调控机制的候选靶标。 相似文献
76.
M. Muoz‐Rojas A. Jordn L. M. Zavala D. De la Rosa S. K. Abd‐Elmabod M. Anaya‐Romero 《Land Degradation \u0026amp; Development》2015,26(2):168-179
During the last few decades, land use changes have largely affected the global warming process through emissions of CO2. However, C sequestration in terrestrial ecosystems could contribute to the decrease of atmospheric CO2 rates. Although Mediterranean areas show a high potential for C sequestration, only a few studies have been carried out in these systems. In this study, we propose a methodology to assess the impact of land use and land cover change dynamics on soil organic C stocks at different depths. Soil C sequestration rates are provided for different land cover changes and soil types in Andalusia (southern Spain). Our research is based on the analysis of detailed soil databases containing data from 1357 soil profiles, the Soil Map of Andalusia and the Land Use and Land Cover Map of Andalusia. Land use and land cover changes between 1956 and 2007 implied soil organic C losses in all soil groups, resulting in a total loss of 16·8 Tg (approximately 0·33 Tg y−1). Afforestation increased soil organic C mostly in the topsoil, and forest contributed to sequestration of 8·62 Mg ha−1 of soil organic C (25·4 per cent). Deforestation processes implied important C losses, particularly in Cambisols, Luvisols and Vertisols. The information generated in this study will be a useful basis for designing management strategies for stabilizing the increasing atmospheric CO2 concentrations by preservation of C stocks and C sequestration. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
77.
Arginine is one of the most important amino acids for animals,and participates in the synthesis and metabolism of many nutrients,plays a role in the development and function of the gastrointestinal tract.Intestinal barrier function is one of the most functions for intestine.The article will summarize the effect of arginine on intestinal barrier.It was explicated the influence on inteseinal immunity of Toll-like receptor.This research provided some references for further study of arginine regulation on animal production. 相似文献
78.
Effects of dietary lysozyme levels on growth performance,intestinal morphology,non‐specific immunity and mRNA expression in weanling piglets 
下载免费PDF全文
下载免费PDF全文 Jiatao Zhu Xiaoxue Pang Zhengfeng Fang Yan Lin Lianqiang Che Shengyu Xu Jian Li Yiming Huang Xiang Su De Wu 《Animal Science Journal》2016,87(3):411-418
The aim of the present study was to determine the effect of dietary lysozyme levels on growth performance, gut health and non‐specific immunity of weanling piglets. A total of 150 weanling piglets were allocated to six treatments. The piglets were fed the same basel diet supplemented with 0, 30, 60, 90 and 120 mg/kg lysozyme as well as antibiotics for 28 days. From day 14 to day 28 of dietary treatment, piglets fed 90 mg/kg lysozyme had greater average daily gain than piglets fed control diet. During the whole experimental period, piglets fed 120 mg/kg lysozyme tended to have greater average daily gain than piglets fed control diet. Compared with piglets fed control diet, piglets fed diets containing antibiotics and 90 mg/kg lysozyme had greater villus height to crypt depth ratio in duodenum and jejunum. Additionally, dietary supplementation of 60 and 90 mg/kg lysozyme as well as antibiotics enhanced the phagocytic activity of peritoneal macrophages in piglets. In conclusion, dietary lysozyme can accelerate the growth of weanling piglets by improving gut health and non‐specific immunity and supplementing 90 mg/kg lysozyme is as effective as antibiotics (20 mg/kg colistin sulphate + 50 mg/kg kitasamycin) in improving the growth performance of weanling piglets. 相似文献
79.
Rearing conditions affected responses of weaned pigs to organic acids showing a positive effect on digestibility,microflora and immunity 下载免费PDF全文
下载免费PDF全文 Yalin Zhang Yumo Song Xiaoling Zhang Yan Lin Lianqiang Che Shengyu Xu De. Wu Bai Xue Zhengfeng Fang 《Animal Science Journal》2016,87(10):1267-1280
Three experiments were conducted to assess the response of weaned pigs to organic acid SF3, which contains 34% calcium formate, 16% calcium lactate, 7% citric acid and 13% medium chain fatty acids. Dietary treatments had no effect on growth performance of piglets (21‐day weaning) fed the commercial prestart diet for 1 week before receiving the experimental diets supplemented with SF3 at 0, 3 or 5 g/kg diet (Exp. 1), whereas diarrhea frequency averaged across a week was decreased by SF3 supplementation (5 g/kg diet) in piglets fed the experimental diets immediately after weaning (Exp. 2). In Exp. 3, piglets (28‐day weaning) were fed the control (containing pure colistin sulfate and enramycin, respectively, at 20 mg/kg diet) for 1 week and then were fed the control or SF3‐supplemented (5 g/kg diet) diet for 2 weeks. The SF3‐fed piglets had greater apparent ileal digestibility of calcium and dry matter, while also demonstrating greater overall gross energy, up‐regulated jejunal expression of sodium‐glucose cotransporter‐1 and transforming growth factor‐β, down‐regulated jejunal expression of tumor necrosis factor (TNF)‐α, higher ileal Lactobacillus, with lower total bacteria content, lower plasma TNF‐α but higher IgG levels than the control‐fed piglets. Collectively, SF3 consumption improved diarrhea resistance of weaned pigs by improving nutrient digestibility, piglet immunity and intestinal bacteria profile. © 2016 Japanese Society of Animal Science 相似文献
80.
S. Sartore P. Sacchi D. Soglia S. Maione A. Schiavone M. De Marco 《British poultry science》2016,57(4):435-443
The objective of this study was to determine the genetic structure and variability of Bionda Piemontese and Bianca di Saluzzo (Piedmont, Northwest Italy) using an international set of microsatellite loci (AVIANDIV-FAO). Differences compared with commercial lines and other Italian breeds were verified to justify the implementation of conservation programmes.
Flock contribution to genetic variability was assessed following the approach implemented in the MolKin software. Comparison was performed using the fixation index and the Reynolds genetic distance. The most likely number of different populations was estimated using the clustering procedure implemented in STRUCTURE.
The molecular information suggests that management practices could have prevented random mating and produced inbreeding and heterogeneity across flocks. In this respect, Bionda and Bianca show substructuring and are more similar to British breeds than other continental European breeds.
Bionda and Bianca fit into the European breeds provided with the highest number of alleles and expected heterozygosity. There is a clear distinction between the Piedmont breeds and the other populations. The Piedmont poultry differ from both commercial lines and other Italian breeds and retain a high level of genetic variability.
As for other indigenous breeds, Bionda and Bianca could make an original contribution to the industry in the future. A collective planned approach to restoration is essential, because the flocks are managed with poor regulation. Enhancing connection between breeders with an efficient replacement interchange and mating plan is the right way of controlling inbreeding, preventing substructuring and increasing variability within the flocks.