全文获取类型
收费全文 | 13369篇 |
免费 | 829篇 |
国内免费 | 1513篇 |
专业分类
林业 | 1358篇 |
农学 | 1321篇 |
基础科学 | 780篇 |
2642篇 | |
综合类 | 5792篇 |
农作物 | 809篇 |
水产渔业 | 528篇 |
畜牧兽医 | 1320篇 |
园艺 | 378篇 |
植物保护 | 783篇 |
出版年
2024年 | 89篇 |
2023年 | 259篇 |
2022年 | 496篇 |
2021年 | 546篇 |
2020年 | 555篇 |
2019年 | 627篇 |
2018年 | 432篇 |
2017年 | 662篇 |
2016年 | 780篇 |
2015年 | 757篇 |
2014年 | 774篇 |
2013年 | 840篇 |
2012年 | 1033篇 |
2011年 | 1094篇 |
2010年 | 867篇 |
2009年 | 870篇 |
2008年 | 700篇 |
2007年 | 832篇 |
2006年 | 582篇 |
2005年 | 452篇 |
2004年 | 357篇 |
2003年 | 300篇 |
2002年 | 200篇 |
2001年 | 207篇 |
2000年 | 164篇 |
1999年 | 146篇 |
1998年 | 143篇 |
1997年 | 114篇 |
1996年 | 125篇 |
1995年 | 121篇 |
1994年 | 109篇 |
1993年 | 89篇 |
1992年 | 91篇 |
1991年 | 65篇 |
1990年 | 67篇 |
1989年 | 46篇 |
1988年 | 42篇 |
1987年 | 25篇 |
1986年 | 18篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1962年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
LI Yan-jun SONG Shao-rui GUO Ya-fen LAN Gan-qiu CHEN Bao-jian YAN Xue-yu WU Yan-jun JIANG Qin-yang 《中国畜牧兽医》2015,42(7):1770-1776
The atherosclerosis (AS) model was prepared in Guangxi Bama mini-pig,and the atherosclerosis index (AI) was preliminarily identified in occurrence of AS to provide the basis for the preparation of related models.20 Guangxi Bama mini-pigs were randomly divided into control group and experimental group which were fed with high fat and cholesterol diet to prepare the AS model.Blood biochemical indexes were detected in the process of model preparation and the correlation between AI and the results of vascular slices was analyzed to initially draw up AI of AS.The results of vascular slices showed that the incidence rates of AS of Guangxi Bama mini-pigs in experimental group and control group were 20% and 0,respectively.The association analysis between the results of vascular slices and AI in the pathogenic Guangxi Bama mini-pigs preliminarily suggested that AI was above 3.8 and lasted for more than 3 months during the attack. 相似文献
72.
在日内高频环境下检验基于兼容法的柯尔莫哥洛夫熵、样本熵和模糊熵等复杂度测算方法对我国沪深300股票指数的测算效率,并运用筛选后的有效算法分阶段研究和比较了序列复杂度的变化过程与变化幅度.结果表明,模糊熵算法是一种更适用于我国沪深300股票指数的有效复杂度测算方法,其对相似容忍度的敏感性更低,测度值连续性更好.随时间推移,我国沪深300股票指数复杂度整体呈上升趋势,而相较于发达市场甚至周边新兴市场其复杂度偏低. 相似文献
73.
74.
为研究复方中草药添加剂对稻鸭共作模式下成都麻鸭生长性能、血清生化指标、抗氧化指标及免疫指标的影响,试验选取体重相近、体况健康的15日龄成都麻鸭240只,随机分为4组,每组5个重复,每个重复12只。4组为对照组饲喂基础饲粮;试验1、2、3组在基础饲粮中按照质量比分别添加0.5%(低剂量组)、1%(中剂量组)、2%(高剂量组)的复方中草药,试验期90 d。结果显示:(1)试验1、2、3组的平均日增重分别较对照组提高2.19%、4.34%、4.98%(P<0.05);试验2、3组的料重比分别较对照组降低3.37%、3.63%(P<0.05);(2)试验2组和3组的总蛋白(TP)分别较对照组提高4.20%、6.08%(P<0.05);试验2组和3组的尿素氮(BUN)分别较对照组降低12.72%、16.36%(P<0.05);试验2组和3组的谷草转氨酶(ALT)分别较对照组降低15.84%、19.22%(P<0.05);试验3组的谷丙转氨酶(AST)较对照组降低19.34%(P<0.05);(3)试验2组和3组超氧化物歧化酶(SOD)分别较对照组提高15.80%、20.00%(P<0.05);试验3组的总抗氧化能力(T-AOC)较对照组提高22.37%(P<0.05);(4)三个试验组的IgA、IgM、IgG、IFN-γ、IL-2显著高于对照组(P<0.05),试验2组的肿瘤坏死因子-α(TNF-α)较对照组提高10.06%(P<0.05),试验2组和3的组溶菌酶(LZM)分别较对照组提高6.79%、5.66%(P<0.05)。综上,中草药添加剂能有效提高稻鸭共作模式下成都麻鸭的生长性能、血清生化指标、抗氧化指标及免疫指标,本试验条件下,最佳饲喂剂量为1%。 相似文献
75.
基于农作制分区的1985—2015年中国小麦生产时空变化 总被引:4,自引:0,他引:4
BAI Bing YANG Yu-Hao WANG Xiao-Hui JIA Hao WU Yao SHI Lei-Gang YIN Xiao-Gang CHEN Fu 《作物学报》2019,45(10):1554-1564
Comparing spatio-temporal variation characteristics of China’s wheat production, yield, sown area and yield-area-contribution in different farming zones in the past 30 years could help improving wheat planting layout and adjusting planting structure. Concentration index, rate of change, moving of gravity and resolution of yield-area-contribution were used to analyze spatio-temporal changes of China’s wheat production and yield-area-contribution based on county wheat production statistics including sown area, production and yield from 1985 to 2015. The wheat sown area decreased obviously in Northeast farming region, Northwest farming region and South farming region and increased rapidly in Huang-Huai-Hai farming region and Yangtze Plain farming region. In Huang-Huai-Hai farming region, the concentration indexes of Haihe Plain farming region, Huang-huai Plain farming region and Fenwei Basin farming region reached to 20.64%, 25.77%, and 21.65% respectively in 2015. Wheat production increased significantly by more than 48 milliontons in Huang-Huai-Hai farming region, and nearly 8 million tons Yangtze Plain farming region but decreased by more than 2.6 million tons in Northeast farming region. In Huang-Huai-Hai farming region, wheat production was concentrated in Haihe Plain farming region, Huang-huai Plain farming region and Yuxi Hill farming region. The average wheat yield continuously improved during the study period, Huang-Huai-Hai farming region and Northwest farming region had the yield increase up to 103.5 kg hm -2 and 92.9 kg hm -2 each year. Wheat yield in Yuxi Hill farming region, Fenwei Basin farming region and Haihe Plain farming region was relatively high in Huang-Huai-Hai farming region. The yield-reduced area was mainly caused by the decreasing of sown area, while the yield-area-contribution rate was different in yield-increased area. Yield-dominant counties were reduced, area-dominant counties were increased and yield-area-dominant counties were relatively steady. In production increased area, yield-dominant and yield-area-dominant counties were the main types in Huang-Huai-Hai Farming region, area-dominant and yield-area-dominant counties were the main types in Yangtze Plain farming region. Chinese wheat production was increasingly concentrated in Huang-Huai-Hai farming region which has high and rapid increase of wheat yield over the past three decades. Haihe Plain farming region, Huang-huai Plain farming region and Fenwei Basin farming region were the most concentrated areas in Huang-Huai-Hai farming region for wheat production during this period. Wheat yield and sown area jointly promoted the increase of wheat production in Huang-Huai-Hai farming region, wheat sown area was the crucial factor to increase wheat production in Yangtze Plain farming region, especially in the north of Jiangsu, Anhui province and greater part of Xinjiang. 相似文献
76.
Alan Mario Zuffo Fábio Steiner Tiago de Oliveira Sousa Jorge González Aguilera Paulo Eduardo Teodoro Francisco de Alcântara Neto Rafael Felippe Ratke 《Journal of Agronomy and Crop Science》2020,206(6):837-850
The effects of water and salt stress on rate of germination and seedling growth were investigated under laboratory conditions in 46 soya bean genotypes from Central-West region of Brazil to verify how these stresses may limit crop establishment during the initial growth stage and also to identify the most tolerant genotypes to drought and salinity. Mild water and salt stresses were imposed by seed exposure to –0.20 MPa iso-osmotic solutions with polyethylene glycol—PEG 6000 (119.57 g/L) or NaCl (2.357 g/L) for 12 days at 25°C. The germination percentage, seedling length and seedling dry matter were measured, and then, salt or drought tolerance indexes were calculated. The “NS 5909 RG,” “NS 7000 IPRO,” “NS 7338IPRO,” “FPS Solimões RR,” “NS 5151 IPRO,” “SYN 13610 IPRO,” “LG 60177 IPRO,” “NS 6909 IPRO” and “BMX Desafio RR” were identified as the most drought-tolerant genotypes, whereas under salinity conditions, the genotypes “5D 615 RR,” “BMX Desafio RR,” “5D 6215 IPRO” and “BMX Ponta IPRO” were identified as tolerant. The “BMX Desafio RR” is the genotype most adapted to both stress conditions and, therefore, should be used under conditions of water shortage and excess salt in the soil at sowing time. 相似文献
77.
大白菜花青素含量及色差指标相关性研究 总被引:3,自引:0,他引:3
为了探寻大白菜花青素含量快速测定的方法,本文利用pH差计法和色差仪分别测定了‘城阳青’(普通大白菜)、‘秋宝黄’(黄心白菜)和‘彩凤’3个不同叶色大白菜品种花青素含量以及色差指标,并对6个色泽参数与花青素含量进行了相关和回归分析。结果表明:6个色泽参数均能反映白菜叶片间叶色的细微变化,‘城阳青’和‘秋宝黄’不含花青素,紫色白菜‘彩凤’的花青素主要分布于由外向内的第1~4层叶片。色泽参数L,b,h和C分别与花青素含量呈极显著或显著负相关关系(相关系数分别为-0.85**,-0.58**,-0.49*,-0.58**)。以色泽参数值L、a、h与花青素含量建立了多元回归方程:y=90.24-1.07x1+5.65x2-142.71x3(x1为L值,x2为a值,x3为h值,y为花青素含量),该回归方程相关系数为0.9629。通过色差计依据建立的回归方程可快速测定紫色大白菜花青素的含量。 相似文献
78.
79.
《农业科学与技术》2016,(3):544-550
The morphological characters, physiological characters, yield traits and yield per plant of total 49 rice cultivars from Ningxia were investigated under conditions of water stress and non-water stress so as to determine the relationship between each trait and yield per plant under water stress and the relationship between each relative character and drought resistance coefficient under water stress and non-water stress. The correlation, grey correlation, stepwise regression and path analyses showed that the til er number per plant, plant height, grain density, effective panicle number per plant and grain number per pan-icle, total 5 traits, were significantly correlated with the drought resistance of rice, and they could be used to identify the drought resistance of rice in Ningxia. In addition, the drought resistance of rice was graded qualitatively according to the subordinate function value of corresponding drought resistance coefficient. The results showed that among the 49 rice cultivars from Ningxia, 6 rice cultivars were highly drought resistant, and 9 rice cultivars were moderately drought resistant, suggesting that the evalua-tion method was feasible and effective. 相似文献
80.