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904.
Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification 总被引:1,自引:0,他引:1
Meredith RW Janečka JE Gatesy J Ryder OA Fisher CA Teeling EC Goodbla A Eizirik E Simão TL Stadler T Rabosky DL Honeycutt RL Flynn JJ Ingram CM Steiner C Williams TL Robinson TJ Burk-Herrick A Westerman M Ayoub NA Springer MS Murphy WJ 《Science (New York, N.Y.)》2011,334(6055):521-524
Previous analyses of relations, divergence times, and diversification patterns among extant mammalian families have relied on supertree methods and local molecular clocks. We constructed a molecular supermatrix for mammalian families and analyzed these data with likelihood-based methods and relaxed molecular clocks. Phylogenetic analyses resulted in a robust phylogeny with better resolution than phylogenies from supertree methods. Relaxed clock analyses support the long-fuse model of diversification and highlight the importance of including multiple fossil calibrations that are spread across the tree. Molecular time trees and diversification analyses suggest important roles for the Cretaceous Terrestrial Revolution and Cretaceous-Paleogene (KPg) mass extinction in opening up ecospace that promoted interordinal and intraordinal diversification, respectively. By contrast, diversification analyses provide no support for the hypothesis concerning the delayed rise of present-day mammals during the Eocene Period. 相似文献
905.
Chapman MR Robinson LS Pinkner JS Roth R Heuser J Hammar M Normark S Hultgren SJ 《Science (New York, N.Y.)》2002,295(5556):851-855
Amyloid is associated with debilitating human ailments including Alzheimer's and prion diseases. Biochemical, biophysical, and imaging analyses revealed that fibers produced by Escherichia coli called curli were amyloid. The CsgA curlin subunit, purified in the absence of the CsgB nucleator, adopted a soluble, unstructured form that upon prolonged incubation assembled into fibers that were indistinguishable from curli. In vivo, curli biogenesis was dependent on the nucleation-precipitation machinery requiring the CsgE and CsgF chaperone-like and nucleator proteins, respectively. Unlike eukaryotic amyloid formation, curli biogenesis is a productive pathway requiring a specific assembly machinery. 相似文献
906.
Ivens PA Matthews D Webb K Newton JR Steward K Waller AS Robinson C Slater JD 《Equine veterinary journal》2011,43(3):359-364
Reasons for performing study: Strangles is the most commonly diagnosed and important infectious disease of horses worldwide. Very little is known about the temporo‐spatial and molecular epidemiology of strangles. The disease is not notifiable in the UK and there are few published data on the geographical locations of outbreaks. Objective: To investigate whether typing of a surface protein (SeM) of Streptococcus equi ssp. equi (S. equi), the causative agent of strangles, is a useful epidemiological tool. Methods: The variable region of the SeM gene was amplified from 145 isolates of S. equi by PCR and sequenced. Different SeM gene alleles were assigned based on the SeM database, grouped into phylogenetic clusters using split decomposition analysis and plotted against the submitting veterinary practices. Results: In this study 21 S. equi SeM alleles were found, including 9 previously unidentified alleles and representing 4 phylogenetic groups. S. equi containing SeM alleles 9 and 7 were the most commonly isolated and there was a high number of low frequency alleles. The occurrence of an outbreak cluster in the north‐west of the UK is also reported. Conclusions: Strangles outbreaks can be differentiated on the basis of their SeM allele sequences. The data provide further evidence of SeM mutation leading to the emergence of novel, but related SeM alleles that are geographically linked. Sequencing of the SeM gene is a useful tool for the elucidation of strangles epidemiology at a regional and a national level. Potential relevance: This technique may allow differentiation or linkage of strangles outbreaks and as such may be an effective tool for local as well as national and international disease surveillance. 相似文献
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Throughout the United States, opportunities to experience noise-free intervals are disappearing. Rapidly increasing energy
development, infrastructure expansion, and urbanization continue to fragment the acoustical landscape. Within this context,
the National Park Service endeavors to protect acoustical resources because they are essential to park ecology and central
to the visitor experience. The Park Service monitors acoustical resources in order to determine current conditions, and forecast
the effects of potential management decisions. By community noise standards, background sound levels in parks are relatively
low. By wilderness criteria, levels of noise audibility are remarkably high. A large percentage of the noise sources measured
in national parks (such as highways or commercial jet traffic) originates outside park boundaries and beyond the management
jurisdiction of NPS. Many parks have adopted noise mitigation plans, but the regional and national scales of most noise sources
call for conservation and management efforts on similar scales. 相似文献
909.
Robinson T 《Science (New York, N.Y.)》1974,184(4135):430-435
910.
The South pole region of the moon as seen by clementine 总被引:2,自引:0,他引:2
The Clementine mission has provided the first comprehensive set of high-resolution images of the south pole region of the moon. Within 5 degrees of latitude of the pole, an area of an estimated 30,000 square kilometers remained in shadow during a full lunar rotation and is a promising target for future exploration for ice deposits. The Schr?dinger Basin (320 kilometers in diameter), centered at 75 degrees S, is one of the two youngest, least modified, great multiring impact basins on the moon. A large maar-type volcano localized along a graben within the Schr?dinger Basin probably erupted between 1 and 2 billion years ago. 相似文献