全文获取类型
收费全文 | 2713篇 |
免费 | 190篇 |
国内免费 | 150篇 |
专业分类
林业 | 120篇 |
农学 | 148篇 |
基础科学 | 71篇 |
370篇 | |
综合类 | 753篇 |
农作物 | 166篇 |
水产渔业 | 272篇 |
畜牧兽医 | 940篇 |
园艺 | 44篇 |
植物保护 | 169篇 |
出版年
2024年 | 13篇 |
2023年 | 32篇 |
2022年 | 56篇 |
2021年 | 84篇 |
2020年 | 80篇 |
2019年 | 109篇 |
2018年 | 68篇 |
2017年 | 114篇 |
2016年 | 118篇 |
2015年 | 105篇 |
2014年 | 119篇 |
2013年 | 159篇 |
2012年 | 180篇 |
2011年 | 165篇 |
2010年 | 152篇 |
2009年 | 143篇 |
2008年 | 147篇 |
2007年 | 161篇 |
2006年 | 147篇 |
2005年 | 140篇 |
2004年 | 97篇 |
2003年 | 85篇 |
2002年 | 70篇 |
2001年 | 73篇 |
2000年 | 66篇 |
1999年 | 50篇 |
1998年 | 37篇 |
1997年 | 41篇 |
1996年 | 33篇 |
1995年 | 40篇 |
1994年 | 28篇 |
1993年 | 27篇 |
1992年 | 30篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 2篇 |
排序方式: 共有3053条查询结果,搜索用时 15 毫秒
881.
882.
研究了南疆环塔里木特色林果产区果林行间套种生产牧草的干草产量、根系分布、营养品质及土壤相关性状,探讨林下套种牧草的生产可行性及对果园土壤的影响.结果表明:高大成龄香梨果林套种高羊茅、鸭茅、黑麦草和苏丹草干草产量分别为5.45、3.62、4.71、11.12 t/hm2;低矮红枣果林行间套种草木樨、大叶苜蓿、苏丹草、一年生黑麦草一年内可刈割3次,其干草产量分别达到9.20、8.78、14.33、7.58 t/hm2,且供试牧草地下根量的90%以上都集中在20 cm土层以内,果园生草后土壤有机质和氮磷钾含量均高于清耕区;稀植果林套种牧草可以保证一定的牧草产量和品质,对果林根层土壤性状无明显负面影响. 相似文献
883.
884.
The objective of this study was to determine the efficiency of different plant systems in capturing deep soil nitrate (NO3-) to reduce NO3- leaching in a field plot experiment using 15N labelling. The study was conducted on a calcareous alluvial soil on the North China Plains and the plant systems evaluated included alfalfa (Medicago sativa), American black poplar (Populus nigra) and cocksfoot (Dactylis). ^15N-labelled N fertilizer was injected to 90 cm depth to determine the recovery of ^15N by the plants. With conventional water and nutrient management, the total recovery of ^15N-labeled NO3--N was 23.4% by alfalfa after two consecutive growth years. The recovery was significantly higher than those by American black poplar (12.3%) and cocksfoot (11.4%). The highest proportion of soil residual ~SN from the labeled fertilizer N (%Ndff) was detected around 90 cm soil depth at the time of the 1st year harvest and at 110-130 cm soil depth at time of the 2nd year harvest. Soil %Ndff in 0-80 cm depth was significantly higher in the alfalfa treatment than those in all the other treatments. The soil %Ndff below 100 cm depth was much lower in the alfalfa than those in all the other treatments. These results indicated that ^15N leaching losses in the alfalfa treatment were significantly lower than by those in the black poplar and cocksfoot treatments, due to the higher root density located in nitrate labeling zone of soil profile. In conclusion, alfalfa may be used as a plant to capture deep soil NO3- left from previous crops to reduce NO3- leaching in high intensity crop cultivation systems of North China Plain. 相似文献
885.
对柳枝稷种子休眠破除方法及7个品种的生物学特性和生产性能进行了研究.结果表明,湿种子在4℃冰箱沙埋层积5 d,种子发芽率最高达到90%以上,干种子在4℃沙埋层积10 d,种子发芽率最高达到87%,发芽率较对照均有显著提高,都能有效的破除柳枝稷种子休眠.7个品种在宁夏引黄灌区的适应性有明显的差别,品种 Gave-in-Rock 在株高、生长速度、分蘖数、草产量和种子产量等性状都显著优于其他品种,为宁夏引黄灌区种植的首选品种;Shawnee、Blackwell和Dakota次之;Trailblazer和Pathfinder牧草产量和种子产量相对较低, Alamo品种不能安全越冬,因此,这3个品种不适宜在宁夏引黄灌区推广种植. 相似文献
886.
887.
E. M. Yu B. H. Liu G. J. Wang D. G. Yu J. Xie Y. Xia W. B. Gong H. H. Wang Z. F. Li N. Wei 《Journal of animal physiology and animal nutrition》2014,98(4):755-765
Grass carp (Ctenopharyngodon idellus) are important Chinese freshwater fish, and in China, the faba bean has been used as the sole food source for grass carp to transform them into crisp grass carp. Because of this, crisp grass carp has become an economically important fish because of its increased muscle hardness. To study the nutritional regulation of type I collagen in faba bean‐fed grass carp, we isolated type I collagen alpha 2 (COL1A2) on the basis of our isolation of COL1A1. The COL1A2 cDNA was found to be 4899 bp in length and included a 4059‐bp coding sequence (CDS) and encoded a polypeptide of 1352 AA. The protein peptide molecular weight was 127.39 kD, and the theoretical isoelectric point was 9.37. The COL1A2 protein possessed five α‐helixes, eight β‐sheets, 16 regions of triple helical repeats, 21 low‐complexity regions, 10 function domains and two zinc‐binding sites; however, no calcium‐binding sites were observed. The mRNA expression of COL1A1 and COL1A2 was assessed in eight tissues (muscle, hepatopancreas, intestine, gills, skin, fin, kidney and spleen) from grass carp and crisp grass carp by semi‐quantitative RT‐PCR. Expression of COL1A1 in the muscle, intestines and skin of crisp grass carp was higher than that in grass carp, and expression of COL1A2 in the muscle, gills, fin and skin of crisp grass carp was higher than that in grass carp. In the muscle of crisp grass carp, expression of COL1A1 and COL1A2 was higher than that in grass carp, which was further confirmed by real‐time PCR, and collagen content also was enhanced. These results demonstrated that type I collagen was closely related to the increased muscle hardness of faba bean‐fed grass carp. 相似文献
888.
饲草饲料是保证畜牧业健康快速发展的物质基础。本文主要通过重点对清水、张家川、甘谷、武山4个草产业重点县的调研,针对我市草产业发展不适应畜牧业快速发展的突出问题,对我市当前及今后草产业的发展提出了一些对策和建议。 相似文献
889.
本文以2003版《草原法》为基本依据,结合酒泉市2010~2011在基本草原划定过程中工作实际,概括提出了生态草地这个新概念,并且从概念的提出、范围的界定、存在的争议、区划中的应用、监管保护效果等五个方面进行了全面论述,最后得出生态草地是指以调节气候、涵养水源、保持水土、防风固沙、生物多样性保护等生态功能为主的、无放牧利用价值的、严重沙化、退化、荒漠化、必须封育保护的、盖度在5%以下的草地.生态草地概念的提出应用使多部门管理的边缘模糊地类管理权限得到明确,为生态草原管理提供了法律依据,促进了草原生态保护和恢复,概念应用价值显著. 相似文献
890.
Domenico Caivano Antonello Bufalari Maria Elena Giorgi Maria Beatrice Conti Maria Chiara Marchesi Giovanni Angeli Francesco Porciello Francesco Birettoni 《Veterinary radiology & ultrasound》2014,55(5):561-564
A 3‐year‐old English Setter dog was presented for an acute onset of coughing. Tracheobronchoscopic examination allowed localization and removal of one grass awn foreign body. A second migrated grass awn was suspected to be present in the left caudal lung lobe. Transesophageal ultrasound revealed an area of pulmonary consolidation in the dorsomedial portion of left caudal lobe and a linear hyperechoic structure consistent with a grass awn foreign body within the area of consolidation. Transesophageal ultrasonography was also used to provide anatomical landmarks that facilitated successful thoracoscopic removal of the foreign body. 相似文献