全文获取类型
| 收费全文 | 10150篇 |
| 免费 | 1036篇 |
| 国内免费 | 827篇 |
专业分类
| 林业 | 1352篇 |
| 农学 | 1467篇 |
| 基础科学 | 851篇 |
| 1555篇 | |
| 综合类 | 3455篇 |
| 农作物 | 730篇 |
| 水产渔业 | 413篇 |
| 畜牧兽医 | 1173篇 |
| 园艺 | 400篇 |
| 植物保护 | 617篇 |
出版年
| 2025年 | 3篇 |
| 2024年 | 135篇 |
| 2023年 | 157篇 |
| 2022年 | 338篇 |
| 2021年 | 420篇 |
| 2020年 | 403篇 |
| 2019年 | 372篇 |
| 2018年 | 275篇 |
| 2017年 | 419篇 |
| 2016年 | 372篇 |
| 2015年 | 418篇 |
| 2014年 | 439篇 |
| 2013年 | 512篇 |
| 2012年 | 605篇 |
| 2011年 | 637篇 |
| 2010年 | 632篇 |
| 2009年 | 631篇 |
| 2008年 | 584篇 |
| 2007年 | 556篇 |
| 2006年 | 556篇 |
| 2005年 | 454篇 |
| 2004年 | 249篇 |
| 2003年 | 225篇 |
| 2002年 | 259篇 |
| 2001年 | 256篇 |
| 2000年 | 207篇 |
| 1999年 | 244篇 |
| 1998年 | 252篇 |
| 1997年 | 189篇 |
| 1996年 | 165篇 |
| 1995年 | 172篇 |
| 1994年 | 156篇 |
| 1993年 | 160篇 |
| 1992年 | 123篇 |
| 1991年 | 104篇 |
| 1990年 | 81篇 |
| 1989年 | 88篇 |
| 1988年 | 62篇 |
| 1987年 | 38篇 |
| 1986年 | 18篇 |
| 1985年 | 6篇 |
| 1984年 | 11篇 |
| 1983年 | 7篇 |
| 1982年 | 7篇 |
| 1981年 | 9篇 |
| 1980年 | 5篇 |
| 1979年 | 1篇 |
| 1964年 | 1篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
991.
Lichao Zhai Lihua Zhang Yongzeng Cui Lifang Zhai Mengjing Zheng Yanrong Yao Jingting Zhang Wanbin Hou Liyong Wu Xiuling Jia 《农业科学学报》2024,23(4):1179-1194
Adjusting agronomic measures to alleviate the kernelposition effect in maize is important for ensuring high yields. In order to clarify whether the combinedapplication of organic fertilizer and chemical fertilizer (CAOFCF) canalleviate the kernel position effect of summer maize, field experiments wereconducted during the 2019 and 2020 growing seasons, and five treatments wereassessed: CF, 100% chemical fertilizer; OFCF1, 15% organic fertilizer+85%chemical fertilizer; OFCF2, 30% organic fertilizer+70% chemical fertilizer;OFCF3, 45% organic fertilizer+55% chemical fertilizer; and OFCF4, 60% organicfertilizer+40% chemical fertilizer. Compared with the CF treatment, the OFCF1 and OFCF2 treatmentssignificantly alleviated the kernel position effect by increasing the weightratio of inferior kernels to superior kernels and reducing the weight gapbetween the superior and inferior kernels. These effects were largely due to the improved filling and starchaccumulation of inferior kernels. However, there were no obvious differences in the kernel position effectamong plants treated with CF, OFCF3, or OFCF4 in most cases. Leaf area indexes, post-silkingphotosynthetic rates, and net assimilation rates were higher in plants treatedwith OFCF1 or OFCF2 than in those treated with CF, reflecting an enhancedphotosynthetic capacity and improved post-silking dry matter accumulation (DMA)in the plants treated with OFCF1 or OFCF2. Compared with the CF treatment, the OFCF1 and OFCF2 treatments increasedpost-silking N uptake by 66.3 and 75.5%, respectively, which was the majorfactor driving post-silking photosynthetic capacity and DMA. Moreover, the increases in root DMA andzeatin riboside content observed following the OFCF1 and OFCF2 treatmentsresulted in reduced root senescence, which is associated with an increasedpost-silking N uptake. Analyses showedthat post-silking N uptake, DMA, and grain yield in summer maize werenegatively correlated with the kernel position effect. In conclusion, the combined application of15–30% organic fertilizer and 70–85% chemical fertilizer alleviated the kernelposition effect in summer maize by improving post-silking N uptake andDMA. These results provide new insightsinto how CAOFCF can be used to improve maize productivity. 相似文献
992.
Xiaogang He Zirong Li Sicheng Guo Xingfei Zheng Chunhai Liu Zijie Liu Yongxin Li Zheming Yuan Lanzhi Li 《农业科学学报》2024,23(8):2541-2556
Marker-assisted selection (MAS) and genomic selection (GS) breeding have greatly improved the efficiency of rice breeding. Due to the influences of epistasis and gene pleiotropy, ensuring the actual breeding effect of MAS and GS is still a difficult challenge to overcome. In this study, 113 indica rice varieties (V) and their 565 testcross hybrids (TC) were used as the materials to investigate the genetic basis of 12 quality traits and nine agronomic traits. The original traits and general combining ability of the parents, as well as the original traits and mid-parent heterosis of TC, were subjected to genome-wide association analysis. In total, 381 primary significantly associated loci (SAL) and 1,759 secondary SALs that had epistatic interactions with these primary SALs were detected. Among these loci, 322 candidate genes located within or nearby the SALs were screened, 204 of which were cloned genes. A total of 39 MAS molecular modules that are beneficial for trait improvement were identified by pyramiding the superior haplotypes of candidate genes and desirable epistatic alleles of the secondary SALs. All the SALs were used to construct genetic networks, in which 91 pleiotropic loci were investigated. Additionally, we estimated the accuracy of genomic prediction in the parent V and TC by incorporating either no SALs, primary SALs, secondary SALs or epistatic effect SALs as covariates. Although the prediction accuracies of the four models were generally not significantly different in the TC dataset, the incorporation of primary SALs, secondary SALs, and epistatic effect SALs significantly improved the prediction accuracies of 5 (26%), 3 (16%), and 11 (58%) traits in the V dataset, respectively. These results suggested that SALs and epistatic effect SALs identified based on an additive genotype can provide considerable predictive power for the parental lines. They also provide insights into the genetic basis of complex traits and valuable information for molecular breeding in rice. 相似文献
993.
Qing Liu Bingjin M Yijing Meng Linmei Yu Zirui Wang Tao Jia Wenbin Zheng Wenwei Gao Shichen Xie Xingquan Zhu 《农业科学学报》2024,23(1):239-250
994.
Gang Lu Feiyan Zheng Yuqing Xiao Ran Shao Jiajun Ou Xin Yin Shoujun Li Guihong Zhang 《农业科学学报》2024,23(9):3145-3158
Recently, increasing natural infection cases and experimental animal challenge studies demonstrated domestic cats are susceptible to multiple subtypes influenza A virus (IAV) infections. Notably, some subtype IAV strains could circulate in domestic cats after cross-species transmission and even infected humans, posing a threat to public health. Host factors related to viral polymerase activity could determine host range of IAV and acidic nuclear phosphoprotein 32 (ANP32) is the most important one among them. However, role of cat-derived ANP32 on viral polymerase activity and host range of IAV is still unknown. In the present study, a total of 10 feline ANP32 (feANP32) splice variants (including 5 feANP32A, 3 feANP32B, and 2 feANP32E) were obtained from domestic cats by RT-PCR. Sequence alignment results demonstrated amino acid deletions and/or insertions occurred among feANP32 variants, but all feANP32 proteins were primarily localized to cell nucleus. Minigenome replication systems for several representative IAV strains were established and the support ability of feANP32 on IAV polymerase activity was estimated. The results indicated that most feANP32A and feANP32B splice variants were able to support all the tested IAV strains, though the support activity of a single feANP32 protein on polymerase activity varied among different IAV strains. In addition, the role of feANP32 in supporting H3N2 canine influenza virus was determined by investigating viral replication in vitro. Collectively, our study systematically investigated the support activity of feANP32 on IAV, providing a clue for further exploring the mechanism of susceptibility of cats to IAV. 相似文献
995.
Qichao Chai Meina Zheng Yanli Li Mingwei Gao Yongcui Wang Xiuli Wang Chao Zhang Hui Jiang Ying Chen Jiabao Wang Junsheng Zhao 《农业科学学报》2024,23(10):3343-3357
996.
Aim at the problem that the EO imaging tracking system is inconsistent with the model of probabilistic data association with amplitude information (PDA AI), which supposes that the greater the amplitude value is, the greater the probability of being the tracked target will be, a modified PDA AI (MPDA AI) is presented . Based on the fact that the amplitude and the motion of the interested target are consistent in a short period, the MPDA AI models the amplitude information and the motion information of the target as well as their consistency with Markov stationary signal to analyze the association procedure of motion and amplitude. The lower bounds of Cramer Rao estimation error for PDA AI and MPDA AI are calculated and discussed in detail. The theoretical analysis and experimental results show that estimating the target motion with the MPDA AI will be more accurate and more reliable than estimating with the original PDA AI. 相似文献
997.
为研究甘油超临界水气化制氢过程及转化动力学,采用正交试验和单因素试验,在连续式反应器中,分析不同工艺参数对甘油超临界水气化气体产物分布和气化转化效率的影响,对气体产物进行气相色谱分析。利用集总动力学研究方法,优化甘油超临界水气化转化动力学模型,增加CO2甲烷化反应路径,探讨甘油超临界水气化过程中动力学参数和气相产物生成及消耗路径。结果表明：甘油超临界水气化制氢的最佳工况为温度600 ℃、甘油浓度0.015 mol/L、压力27 MPa和停留时间18 s,此时H2产量为2.411 mol/mol,气化效率为76.49 %。单因素试验结果可知,较高反应温度和压力、较低原料浓度和适当延长停留时间有利于提高H2产量和甘油气化效率。反应速率常数随着温度的升高而增加,甘油热解路径Ⅱ和中间体蒸汽重整路径Ⅰ的活化能分别高于甘油热解路径Ⅰ和中间体蒸汽重整路径Ⅱ。H2主要通过甘油热解和水气变换反应生成,CO2主要通过甘油热Ⅰ和水气变换反应生成,CO2甲烷化是H2和CO2消耗的主要路径。中间体热解是CO和CH4的主要生成路径,CO的主要消耗路径是水气变换反应。 相似文献
998.
WANG Hao-quan DAI Wei-min ZHANG Zi-xu LI Meng-shuo MENG Ling-chao ZHANG Zheng LU Huan SONG Xiao-ling QIANG Sheng 《农业科学学报》2023,22(1):149-169
Rice, the main food crop in China, has been sporadically reported to suffer from weedy rice infestation. However, the overall occurrence and distribution pattern of Chinese weedy rice remains unclear because a systematic survey has not been conducted. In order to reveal the infestation of Chinese weedy rice, a field survey was conducted in 999 sampling sites all over the rice-growing regions in China from 2009 to 2016 using seven-scale visual scoring of the level of weed infestation. Weedy rice was found 39% occurrence incidence in a total of 387 sites. The sampling sites with 50% or higher overall weedy rice infestation index mainly radiated from Jiangsu, Heilongjiang, Ningxia and Guangdong to the whole East China, Northeast China, Northwest China and South China. A total of 45 morphological characters from 287 populations (collected simultaneously with the field survey) out of those occurred sites were observed and analyzed using multivariate analysis in common gardens with the same cultivation conditions in 2017 and 2019. Canonical correlation analysis showed that 45 morphological characters were significantly related to the latitude, mean temperature, minimum temperature, precipitation and mean diurnal range factors. The 287 weedy rice populations were divided into three morphological groups with climate-dependent geographical differentiation: strong tiller type only in Jiangsu, large leaf type in South China and Central China and large grain type mainly in North China. Weedy rice seriously infested rice fields and had a geography, climate and cultivated rice type-dependent morphological and biotype differentiation in China. It is suggested to pay attention to the harmfulness of weedy rice and adopt comprehensive control strategies. 相似文献
999.
以滇西北千湖山为研究区,使用1995—2019年的Landsat系列影像资料提取小微水体的空间分布,分析1995—2019年该区域小水体和微水体的景观特征变化规律,并探讨了气候变化对它们的影响。结果表明：小水体和微水体的平均分布海拔分别为3953.1 m和3987.8 m,小水体和微水体分布区的坡度分别为9°～14°和6°～13°,2种水体主要分布在千湖山的东坡和北坡,南坡分布得最少。小水体的斑块面积大于微水体,趋于聚集分布;微水体斑块数量多于小水体,趋于离散分布。1995—2019年,小水体和微水体的斑块面积、斑块数量和分离度指数均呈先增加后减少的趋势。 1995—2019年,千湖山地区气候整体呈暖干化趋势。海拔和坡度对小微水体的景观特征有显著影响;气温升高对小微水体斑块数量、斑块面积增加有正向作用,但会导致斑块破碎度增加;降水减少对小微水体景观特征的影响与气温升高相反。本研究表明,在千湖山地区,地形因素（海拔和坡度）控制着小微水体的空间分布,气候暖干化对小微水体的景观特征变化有显著影响,微水体对环境变化的敏感性高于小水体。 相似文献
1000.
在1998～1999年对北京地区室外家蝇种群乙酰胆碱酯酶 (ACh E)的不敏感基因表现型进行了检测。以敏感品系为标准 ,海淀区 (A)、海淀区 (B)、丰台区、朝阳区家蝇种群具有的对敌敌畏不敏感基因表现型频率分别为 11%、34%、56%和24% ;对灭多威不敏感基因表现型频率为4%、4%、8%和20 %。ACh E对敌敌畏和灭多威的不敏感基因表现型 ,北京地区家蝇可分成4种 :1)对敌敌畏和灭多威均敏感型 ;2 )对敌敌畏不敏感 ,对灭多威敏感型 ;3)对敌敌畏敏感 ,对灭多威不敏感型 ;4 )对敌敌畏和灭多威均不敏感型。目前 ,在北京地区以对敌敌畏和灭多威均敏感的 ACh E表现型为主 ,其次为第二种类型 ,第三和第四种类型的频率不高。 相似文献