全文获取类型
收费全文 | 253篇 |
免费 | 31篇 |
国内免费 | 1篇 |
出版年
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 12篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1972年 | 1篇 |
1969年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1959年 | 1篇 |
1933年 | 1篇 |
1931年 | 1篇 |
1924年 | 1篇 |
1920年 | 1篇 |
1918年 | 1篇 |
1917年 | 1篇 |
排序方式: 共有285条查询结果,搜索用时 312 毫秒
61.
62.
63.
Wingfield BD; Grant WS; Wolfaardt JF; Wingfield MJ 《Molecular biology and evolution》1994,11(3):376-383
The genus Ceratocystis sensu stricto includes important fungal pathogens of
woody and herbaceous plants. This genus is distinguished from species in
Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore
shape has been used extensively in delineating Ceratocystis taxa, which
show a large variety of ascospore shapes. Sequence analysis of one region
of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA
subunit showed that there was a majority of multiple substitutions at
nucleotide sites and that there was a low transition/transversion ratio, T
= 0.72. Both of these results suggest that these are well established, old
species. Ascospore morphology, for the most part, was not congruent with
the molecular phylogeny, and the use of morphological characters may be
misleading in the taxonomy of these species.
相似文献
64.
The action of sodium amobarbital is studied during the patterning effect in rats selectively bred for low and high emotionality. The drug disrupts patterned running in the goal section of the alley in Maudsley non-reactive but not in Maudsley reactive rats for the last five trial-pairs. Sodium amobarbital also affects the behavior of these strains in a differential manner, in start and run sections, during the first trial-pair. The results show that a function-related physiological change has taken place in the Maudsley strains of rats. 相似文献
65.
L H Phylip A D Richards J Kay J Kovalinka P Strop I Blaha J Velek V Kostka A J Ritchie A V Broadhurst 《Biochemical and biophysical research communications》1990,171(1):439-444
Kinetic constants (Km,Kcat) are derived for the hydrolysis of a number of chromogenic peptide substrates by the aspartic proteinase from HIV-2. The effect of systematic replacement of the P2 residue on substrate hydrolysis by HIV-1 and HIV-2 proteinases is examined. 相似文献
66.
MJ Doughty 《Biotechnic & histochemistry》2016,91(8):501-509
Goblet cells were visualized in impression cytology specimens from bulbar conjunctiva of the rabbit eye using Giemsa staining. Highly magnified images were used to generate outlines of the goblet cells and their characteristic eccentric nuclei. Using sets of 10 cells from 15 cytology specimens, I found that the longest dimension of the goblet cells averaged 16.7 ± 2.3 μm, the shortest dimension averaged 14.4 ± 1.8 μm and the nucleus averaged 6.3 ± 0.8 μm. The goblet cells were ellipsoid in shape and the longest:shortest cell dimension ratio averaged 1.169 ± 0.091. The goblet cell areas ranged from 108 to 338 μm2 (average 193 ± 50 μm2). The area could be predicted reliably from the longest and shortest dimensions (r2 = 0.903). The areas of goblet cell nuclei were 15–58 μm2 (average 33 ± μm2) and the nucleus:cytoplasm area fraction was predictably greater in smaller goblet cells and less in the larger goblet cells (Spearman correlation = 0.817). The nuclei were estimated to occupy an average of 9.5% of the cell volume. The differences in size, shape and nucleus:cytoplasm ratio may reflect differences in goblet cell maturation. 相似文献
67.
68.
Modifications to reduce bycatch in prawn trawls: A review and framework for development 总被引:13,自引:0,他引:13
The incidental capture of non-target species fromprawn trawling has recently attracted worldwide attention. Primarily, concerns arisefrom the perception that prawn trawls catch anddiscard large numbers of juveniles of species that,when larger, are targeted in other commercial andrecreational fisheries. While several managementoptions are available, the majority of fisheries inthe world have attempted to address this issue throughphysical modifications to trawls, designed to improveselectivity. The types of modifications used reflectfishery-specific characteristics; however, mostcan be broadly classified into twocategories, including: (1) those that separate speciesby differences in behaviour; and (2) those thatmechanically exclude unwanted organisms according totheir size. In the present paper, I provide achronological review of publications in the primaryliterature that describe experiments examiningmodifications within these categories. This reviewshows that inherent variabilities among differentfisheries greatly influence the types of designs thatneed to be applied and although some designs have thepotential for application across different fisheries,significant modification and re-evaluation are oftenrequired. By collating information from previousstudies, I also propose a framework encompassingthe various stages involved in developing and applyingsuccessful modifications in prawn-trawl fisheries. The key stages identified include: (1) quantificationof bycatches and accumulation of fishery-relatedinformation; (2) examination and re-evaluation ofmodifications; (3) assessment of damage inflicted onescaping individuals; and (4) promotion of recommendeddesigns. 相似文献
69.
70.
Linda Broadhurst Martin Driver Lydia Guja Tom North Bindi Vanzella Graham Fifield Stephen Bruce David Taylor David Bush 《Ecological Management & Restoration》2015,16(1):29-32
It has been almost 15 years since concerns about the limited capacity of remnant native vegetation to supply the volumes of seed required to meet increasing restoration demands were first raised. Since that time little progress has been made towards addressing this constraint with the ongoing decline of native vegetation communities, especially since 2000, further challenging seed supply. We provide examples of the size of this demand for seed, as well as major issues associated with seed sourcing. We also discuss how invoking the concept of market forces to drive seed supply and demand is inappropriate and highlight the need for an industry body to oversee seed collection and utilisation standards. We further propose key actions that are required to secure the seed supply chain within the next 20 years to meet existing and future restoration targets. We argue that concerted, coordinated action at Commonwealth, State and regional levels are required to underpin effective future restoration outcomes. 相似文献