全文获取类型
收费全文 | 24314篇 |
免费 | 388篇 |
国内免费 | 58篇 |
专业分类
林业 | 4821篇 |
农学 | 1502篇 |
基础科学 | 198篇 |
4066篇 | |
综合类 | 1437篇 |
农作物 | 2316篇 |
水产渔业 | 2120篇 |
畜牧兽医 | 4694篇 |
园艺 | 1290篇 |
植物保护 | 2316篇 |
出版年
2023年 | 51篇 |
2022年 | 79篇 |
2021年 | 100篇 |
2020年 | 133篇 |
2019年 | 93篇 |
2018年 | 2890篇 |
2017年 | 2823篇 |
2016年 | 1369篇 |
2015年 | 243篇 |
2014年 | 174篇 |
2013年 | 428篇 |
2012年 | 1141篇 |
2011年 | 2446篇 |
2010年 | 2305篇 |
2009年 | 1393篇 |
2008年 | 1603篇 |
2007年 | 1915篇 |
2006年 | 361篇 |
2005年 | 369篇 |
2004年 | 372篇 |
2003年 | 402篇 |
2002年 | 283篇 |
2001年 | 162篇 |
2000年 | 192篇 |
1999年 | 125篇 |
1998年 | 52篇 |
1992年 | 104篇 |
1991年 | 118篇 |
1990年 | 133篇 |
1989年 | 153篇 |
1988年 | 128篇 |
1987年 | 104篇 |
1986年 | 104篇 |
1985年 | 101篇 |
1984年 | 95篇 |
1983年 | 76篇 |
1979年 | 105篇 |
1978年 | 76篇 |
1977年 | 72篇 |
1976年 | 51篇 |
1975年 | 72篇 |
1974年 | 86篇 |
1973年 | 93篇 |
1972年 | 76篇 |
1971年 | 82篇 |
1970年 | 81篇 |
1969年 | 89篇 |
1968年 | 72篇 |
1967年 | 66篇 |
1965年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Karin Themann Sabine Werres R. Lüttmann H.-A. Diener 《European journal of plant pathology / European Foundation for Plant Pathology》2002,108(4):337-343
Samples of water and sediment were taken from drains, reservoirs and wells from four commercial hardy ornamental nurseries with water recirculation systems. The samples were taken on seven different dates throughout a single year from August 1994 to July 1995. The samples were screened for Phytophthora species using five different methods: direct plating, three bait tests (using lupin seedlings, apples and Rhododendron leaves) and a DAS-ELISA (double-antibody sandwich enzyme-linked immunosorbent-assay) with two antisera. In the nurseries with old water recirculation systems, Phytophthora species were detected in the drains and in the reservoirs. In the nursery with a new recirculation system, the pathogens were only present in the drains. None of the water samples from wells in any of the nurseries were contaminated. Phytophthora species were present in the water as well as in the sediment samples from drains and reservoirs. They were detected in the water recirculation systems irrespective of the season. The number of isolates increased about sevenfold between late summer and spring. At least 12 different Phytophthora species were identified: some isolates were previously unrecorded species. The epidemiology of the pathogens in outdoor water recirculation systems as well as the importance of the results for commercial nurseries is discussed. 相似文献
52.
A. Sambade L. Rubio S. M. Garnsey N. Costa G. W. Müller M. Peyrou J. Guerri P. Moreno † 《Plant pathology》2002,51(3):257-265
The population of sequence variants of Citrus tristeza virus (CTV) isolates of different geographic origins and pathogenicity properties was characterized by single-strand conformation polymorphism (SSCP) analysis of cDNA of the genes p18, p13, p20 and p23. The mild isolates analysed here usually yielded a SSCP profile with two DNA bands, suggestive of a predominant sequence variant, whereas the SSCP profile of the most virulent isolates contained more than two DNA bands, indicating that their viral populations are likely to be more complex. The set of SSCP profiles of the four genes allowed identification of individual isolates, but no profile characteristic of a geographic area or a biogroup was found. Sweet orange plants singly inoculated with a mild or with a severe isolate yielded the SSCP profile characteristic of each isolate, whereas the SSCP profile of plants successively inoculated with both isolates was a composite of the two individual profiles. The SSCP profile of plants singly inoculated remained constant, but the profile of doubly inoculated plants varied with time. Plants in which the SSCP profile of the severe isolate became predominant showed stem pitting, and those in which the predominant profile corresponded to the mild isolate remained symptomless. The results indicate that SSCP analysis can be used to study changes in RNA populations of doubly inoculated plants and to monitor cross-protection between mild and severe isolates. 相似文献
53.
In a nematode survey of Tylenchida carried out in groundnut (Arachis hypogaea L.) growing areas in the Mediterranean region of Turkey, 15 species were determined as belonging to ten genera of eight families within the superfamilies Tylenchoidea, Dolichodoroidea, Hoplolaimoidea and Anguinoidea. Each of them constitutes a new record on groundnut in Turkey, andScutylenchus tumensis Skwiercz andPratylenchus brachyurus (Godfrey) are reported for the first time in the nematofauna of Turkey. 相似文献
54.
55.
56.
Eiji Tanaka Chihiro Tanaka Atsushi Ishihara Yasumasa Kuwahara Mitsuya Tsuda 《Journal of General Plant Pathology》2003,69(1):1-6
Aciculosporium take (Ascomycota; Clavicipitaceae) is a causal agent of witches' broom of
bamboo plants. The symptoms of this disease are believed to be induced by plant
hormones, particularly auxins. Indole-3-acetic acid (IAA) was identified in
cultures of this fungus in an l-tryptophan-supplemented liquid medium.
IAA production was confirmed on 30 isolates of A. take from various
hosts and locations at levels up to 1 mg/l. The biosynthetic pathway of
IAA in A. take culture was examined by analyzing intermediate products
and by feeding experiments. The results showed that the indole-3-pyruvic acid
pathway (l-tryptophan → indole-3-pyruvic acid → indole
acetaldehyde → IAA) was the dominant pathway in A. take.
Received: June 3, 2002 / Accepted: July 25, 2002 相似文献
57.
Hiromitsu Furuya Tsutomu Matsumoto Shin-ichi Fuji Hideki Naito 《Journal of General Plant Pathology》2003,69(2):115-119
Rice seedling growth, estimated by plant height and root development and discoloration, was better in pasteurized soil than
in unpasteurized soil obtained from a flooded rice field. Rice seedlings also grew better in sterilized soil modified by adding
roots harvested from the pasteurized soil than in soil modified by adding roots harvested from the unpasteurized soil. The
results demonstrate that seedling growth in the rice field soil was inhibited by soil microorganisms, even though no typical
symptoms such as seedling blight or damping-off appeared. Pythium aristosporum is suggested to be involved in the inhibition. Thus, it appears that inconspicuous restraint of rice seedling growth could
occur in soils of rice paddy fields.
Received: May 20, 2002 / Accepted: October 16, 2002
Acknowledgments The authors thank Dr. T. Ichitani, former professor at Osaka Prefectural University, for providing an isolate of Pythium aristosporum for comparison, and Mr. Mitsuaki Sato of Akita Prefectural College of Agriculture for technical assistance. 相似文献
58.
59.
60.