全文获取类型
收费全文 | 127441篇 |
免费 | 6823篇 |
国内免费 | 11771篇 |
专业分类
林业 | 9060篇 |
农学 | 7157篇 |
基础科学 | 6526篇 |
12829篇 | |
综合类 | 60701篇 |
农作物 | 8560篇 |
水产渔业 | 5811篇 |
畜牧兽医 | 20521篇 |
园艺 | 9047篇 |
植物保护 | 5823篇 |
出版年
2024年 | 996篇 |
2023年 | 2617篇 |
2022年 | 5759篇 |
2021年 | 5595篇 |
2020年 | 5332篇 |
2019年 | 5257篇 |
2018年 | 3706篇 |
2017年 | 6056篇 |
2016年 | 4051篇 |
2015年 | 6109篇 |
2014年 | 6424篇 |
2013年 | 7779篇 |
2012年 | 10553篇 |
2011年 | 10966篇 |
2010年 | 10549篇 |
2009年 | 9396篇 |
2008年 | 9383篇 |
2007年 | 8374篇 |
2006年 | 6867篇 |
2005年 | 5486篇 |
2004年 | 3373篇 |
2003年 | 2123篇 |
2002年 | 2325篇 |
2001年 | 2094篇 |
2000年 | 1918篇 |
1999年 | 865篇 |
1998年 | 271篇 |
1997年 | 231篇 |
1996年 | 186篇 |
1995年 | 200篇 |
1994年 | 192篇 |
1993年 | 160篇 |
1992年 | 154篇 |
1991年 | 145篇 |
1990年 | 97篇 |
1989年 | 58篇 |
1988年 | 72篇 |
1987年 | 56篇 |
1986年 | 45篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 26篇 |
1976年 | 5篇 |
1965年 | 6篇 |
1964年 | 11篇 |
1962年 | 31篇 |
1956年 | 38篇 |
1955年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Yufei Guo Chanjuan Shen Anchun Cheng Mingshu Wang Na Zhang Shun Chen Yi Zhou 《Veterinary microbiology》2009,138(3-4):258-265
Anatid herpesvirus 1 (AHV-1) CH virulent strain was first isolated from an infected duck and it was found that this virus strain could induce cytopathic effect (CPE) in duck embryo fibroblast (DEF). Following AHV-1 infection, DEF showed morphological changes such as cell rounding, improved refractivity and detachment from the culture surface. However, its pathological characteristics were not adequately known. Related studies were performed and the results showed that syncytium formation could be observed as the other type of CPE in AHV-1 infection. Hematoxylin-eosin staining and 4’, 6-diamidino-2-phenylindole (DAPI) staining of infected DEF were each used to visualize the shape and distribution of chromatin within nuclei and nuclear fragmentation was observed. Chromatin condensation and margination, as well as formation of apoptotic bodies were observed by transmission electron microscopy (TEM). DNA ladder formation was detected in AHV-1 infected cells and apoptosis of the infected DEF was also detected by flow cytometry analysis of Annexin V-FITC/PI staining method. Therefore, it was suggested that AHV-1 virulent strain can induce syncytium and apoptosis in DEF. Syncytium formation and apoptosis observed in this study may contribute to the elucidation of AHV-1 pathogenesis. 相似文献
82.
DING Xuedong WANG Guohua PAN Xiangchen LIU Dongdong LUO Xuedong MA Yuan LI Maolin CUI Qi ZHANG Qijin 《中国畜牧兽医》2007,47(12):3815-3824
The purpose of this study was to investigate the variation of Orf virus (ORFV) immune related genes after infection with different species.The ORFV genomes of sheep and camel were extracted and named ORFV-Y and ORFV-LT,respectively.Based on ORFV genome sequence published in GenBank (accession No.:KF234407.1),three pairs of specific primers were designed and synthesized to amplify the B2L,F1L and VIR gene fragments of ORFV-Y and ORFV-LT,respectively,and the amplified fragments were cloned into pMD19-T vector,transformed into E.coli DH5α competent cells.The recombinant plasmid was identified,and positive clones were selected for sequencing,DNAStar software was used to analyze the homology,amino acid sequence and phylogenetic tree of 13 ORFV genome sequences published on NCBI.The results showed that the nucleotide homology of B2L,F1L and VIR genes were 92.8% to 99.2%,95.7% to 99.5% and 77.6% to 100%,respectively.After comparing the amino acid sequence between the two genomes and the reference sequence,it was found that there were obvious differences in the immune related genes between the two genomes,and F1L gene had some rules to follow.The phylogenetic analysis of B2L,F1L and VIR genes showed that ORFV-Y was closely related to the Chinese Fujian goat strain,while ORFV-LT was far from the reference strains,and was a separate branch.The results showed that ORFV had obvious difference in immune related genes between sheep and camels,it provided a reference basis for further research on the changes of ORFV gene sequences in different species and the development of vaccines for different species in the future. 相似文献
83.
84.
85.
通过对青岛石老人生态旅游区的植被改造规划的分析,探讨植物不同器官和不同季节的色彩变化在园林景观规划设计中的意义。从生态旅游区的整体色彩效果出发,考虑背景色彩,着重应用原有的绿色基调,调配点缀不同的植物及色彩变化,营造丰富多彩和富于变化的植物色彩景观。 相似文献
86.
AIM:In this article,gastrointestinal tumo r-related historical ar chives of pathology in our hospital were reviewed in order to acknowledge gastro intestinal stromal tumors (GIST).METHODS:These cases were rediagnosed correctly ,these tissues were labeled with some antibodies such as CD117,CD34,α-SMA,S-100,and the ir clinical characteristics were explored.RESULTS:CD117,CD34 were expressed widely in GISTs ,the percen tage of positive expression was CD117 (50/56,89.3%),CD34 (37/56,66.1% ),respectively,α-SMA,S-100 were (17/56,30.4%),(4/56,7.1%),re spe ctively,desmin was negative in these cases.Among them,29 cases were benign a nd borderline,27 cases were malignant.The percentage of occurring in stomach a nd intestine was 91.1%.CONCLUSION:CD117,CD34 are expressed significantly in GIST,t hese might be assistant markers for GIST diagnosis.GISTs mostly occurred in sto mach and intestine. 相似文献
87.
88.
犊牛腹泻是一种常见病、多发病,如治疗及时,治愈率很高,治疗方法也较简单,但如果患畜到了濒死期则很难救治。笔者曾遇到一濒死的腹泻犊牛,经特殊方法救治获愈,现将有关情况介绍如下: 相似文献
89.
Shiva O. MAKAJU Yanqi WU Michael P. ANDERSON Vijaya G. KAKANI Michael W. SMITH Linglong LIU Hongxu DONG Dan CHANG 《农业科学与工程前沿(英文版)》2018,5(1):118
Switchgrass (Panicum virgatum L.), as a model herbaceous crop species for bioenergy production, is targeted to improve biomass yield and feedstock quality. Plant height is a major component contributing to biomass yield. Accordingly, the objectives of this research were to analyze phenotypic variation for biomass and plant height and the association between them and to localize associated plant height QTLs. Two lowland switchgrass mapping populations, one selfed and another hybrid population established in the field at Perkins and Stillwater, Oklahoma, were deployed in the experiment for two years post establishment. Large genetic variation existed for plant biomass and height within the two populations. Plant height was positively correlated with biomass yield in the selfed population (r = 0.39, P<0.0001) and the hybrid population (r = 0.41, P<0.0001). In the selfed population, a joint analysis across all environments revealed 10 QTLs and separate analysis for each environment, collectively revealed 39 QTLs related to plant height. In the hybrid population, the joint analysis across overall environments revealed 35 QTLs and the separate analysis for each environment revealed 38 QTLs. The findings of this research contribute new information about the genetic control for plant height and will be useful for future plant breeding and genetic improvement programs in lowland switchgrass. 相似文献
90.