全文获取类型
收费全文 | 355篇 |
免费 | 45篇 |
国内免费 | 1篇 |
专业分类
401篇 |
出版年
2023年 | 1篇 |
2022年 | 11篇 |
2021年 | 11篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 27篇 |
2017年 | 19篇 |
2016年 | 20篇 |
2015年 | 25篇 |
2014年 | 28篇 |
2013年 | 31篇 |
2012年 | 32篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 8篇 |
2007年 | 17篇 |
2006年 | 18篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1975年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有401条查询结果,搜索用时 0 毫秒
391.
Eight populations of Hemerocallis thunbergii, H. middendorffii , and H. exaltata from Japan were analyzed by starch gel electrophoresis to measure genetic variation at ten allozyme loci. The former two species are widely distributed in eastern Asia, whereas H. exaltata is restricted to the Tobishima and Sado Islands in western Japan. Populations of the three species maintain high levels of allozyme variation: mean expected heterozygosities were 0.288, 0.209, and 0.169, respectively. The UPGMA phenogram obtained from Nei's genetic distance values indicated that H. exaltata is allozymically the most distinct species, whereas populations of H. thunbergii and H. middendorffii are closely related. However, based on gross morphology H. exaltata and H. middendorffii are closely related. This discrepancy and the observed high levels of allozyme variation within populations of the three Hemerocallis species in Japan may in part be due to genetic change among populations of the two Japanese archipelago species. 相似文献
392.
Jung Hae Yoon Gi Hyuck Ryu Paul Finch Joon Shick Rhee 《Journal of Molecular Catalysis .B, Enzymatic》2001,15(4-6)
Enzymatic synthesis of 3-O-methyl-4-O-β-
-galactopyranosyl-
-glucose (3-O-methyl-lactose) has been attempted using both galactosyltransferase and galactosidase activities. The transferase-catalysed reaction produces exclusively the desired product in β-1,4-glycosidic linkage whereas the galactosidase-catalysed reactions predominantly form a 1,6-linked disaccharide. With galactosidase, in order to change the regioselectivity, blocking of the 6-position of 3-O-methyl-
-glucose and anomeric modification of the acceptor structure were investigated. Although acetylation of the 6-position of 3-O-methyl glucose catalysed by lipase was successful, the synthesis of the desired disaccharide did not occur. 相似文献
393.
We collected basic data on the physiological characteristics ofPanax ginseng in order to identify the forest stands that provide the best growth environment. Our research sites included oak, pine, and
mixed-forest stands, in which ginseng seed had been sown several years earlier. Heights and dry weights of forest ginseng
were better under oak trees than in the pine or mixed stands. In addition, photosynthetic rates for ginseng were highest in
the oak forest, particularly at a light intensity of 200 μmol m-2 sec-1. 相似文献
394.
Jong‐Ho Lee Hyoungchul Kim Sung Moon Kim Tae‐Wook Noh Hwa‐Young Jung Hyun‐Yup Lim Hun‐Gi Jung Ji‐Won Son Hae‐Ryoung Kim Byung‐Kook Kim Hae‐June Je Jae‐Chun Lee Huesup Song Hae‐Weon Lee 《Liver Transplantation》2012,2(4):461-468
Glass‐based seals for planar solid‐oxide fuel‐cell (SOFC) stacks are open to uncontrolled deformation and mechanical damages, limiting both sealing integrity and stack reliability, particularly in thermal cycle operations. If the glass‐based seals work like an elastomer‐based compressive seal, SOFC stacks may survive unprecedented numbers of thermal cycles. A novel composite sealing gasket is successfully developed to mimic the unique features of the elastomer‐based compressive seal by controlling the composition and packing behavior of binary ceramic fillers. A single‐cell SOFC stack undergoes more than 100 thermal cycles with little performance loss, during which the sealing integrity is lost/recovered repeatedly upon cooling and reheating, corresponding to unloading/loading of the elastomer‐based compressive seal. The thermal‐cycle responses of the SOFC stack are explained in sequence by the concurrent events of elastic deformation/recovery of ceramic filler network and corresponding redistribution of sealing glass. 相似文献
395.
396.
Sanghee Kim Mi‐Hyun Park Jae‐Ho Jung Dong‐Ha Ahn Tahera Sultana Sejoo Kim Joong‐Ki Park Han‐Gu Choi Gi‐Sik Min 《Zoologica scripta》2012,41(3):281-292
Kim, S., Park, M.‐H., Jung, J.‐H., Ahn, D.‐H., Sultana, T., Kim, S., Park, J.‐K., Choi, H.‐G. & Min, G.‐S. (2012). The mitochondrial genomes of Cambaroides similis and Procambarus clarkii (Decapoda: Astacidea: Cambaridae): the phylogenetic implications for Reptantia. —Zoologica Scripta, 41, 281–292. We determined the complete mitochondrial (mt) genome sequences of two northern hemisphere freshwater crayfish species, Cambaroides similis and Procambarus clarkii (Decapoda: Astacidea: Cambaridae). These species have an identical gene order with typical metazoan mt genome compositions. However, their gene arrangement was very distinctive compared with the pan‐crustacean ground pattern because of the presence of a long inverted block, which included 19 coding genes and a control region (CR). Because the CR was inverted, their nucleotide frequencies showed a reversed strand‐specific bias compared with the other decapods. Based on a comparative analysis of mt genome arrangements between southern and northern hemisphere crayfish and their putative close marine relative (Homarus americanus, a true clawed lobster), we postulated that the ancestor of freshwater crayfish had a typical pan‐crustacean mtDNA gene order, similar to its marine relatives. Based on this assumption, we traced the most parsimonious gene rearrangement scenario of the northern hemisphere crayfish. In a phylogenetic study on the infraordinal relationships in reptan decapods, the lineage Lineata [Thalassinidea (Brachyura, Anomura)] was well supported, while the infraorder positions of Achelata and Astacidea remained unidentified. 相似文献
397.
Woo Young Bang Sam Woong Kim Seul Gi Kwon Jung Hye Hwang Tae Wan Kim Moon‐Suck Ko In‐Cheol Cho Young Kuk Joo Kwang Keun Cho Jin Young Jeong Chul Wook Kim 《Animal genetics》2013,44(4):463-466
Using a methyl‐DNA immunoprecipitation technique in combination with next‐generation deep sequencing, we conducted comprehensive DNA methylation profiling of liver genomes from three pig breeds: Berkshire, Duroc and Landrace. The profiles revealed that the distribution patterns of methylation signals along the genome are conserved among the three pig breeds. Specifically, many signals in coding genes were found in introns, and most signals in the repetitive elements were identified in non‐long terminal repeat (LTR) retrotransposons such as long and short interspersed repetitive elements, implying a significant association with alternative splicing and expression of retrotransposable elements respectively. Differentially methylated regions among the three pig breeds were identified in the non‐LTR retrotransposons, suggesting that they may lead to differential retrotransposable element activity. Altogether, this study provides advanced swine methylome data and valuable resources for understanding the function of DNA methylation in the evolutionary divergence of different pig breeds. 相似文献
398.
Taeho Kim Jiyeon Kim Soowon Cho Gi‐Sik Min Chungoo Park Ramon A. Carreno Steven A. Nadler Joong‐Ki Park 《Zoologica scripta》2014,43(3):289-303
We determined the complete mitochondrial genome sequence of Rhigonema thysanophora, the first representative of Rhigonematomorpha, and used this sequence along with 57 other nematode species for phylogenetic analyses. The R. thysanophora mtDNA is 15 015 bp and identical to all other chromadorean nematode mtDNAs published to date in that it contains 36 genes (lacking atp8) encoded in the same direction. Phylogenetic analyses of nucleotide and amino acid sequence data for the 12 protein‐coding genes recovered Rhigonematomorpha as the sister group to the heterakoid species, Ascaridia columbae (Ascaridomorpha). The organization of R. thysanophora mtDNA resembles the most common pattern for the Rhabditomorpha+Ascaridomorpha+Diplogasteromorpha clade in gene order, but with some substantial gene rearrangements. This similarity in gene order is in agreement with the sequence‐based analyses that indicate a close relationship between Rhigonematomorpha and Rhabditomorpha+Ascaridomorpha+Diplogasteromorpha. These results are consistent with certain analyses of nuclear SSU rDNA for R. thysanophora and some earlier classification systems that asserted phylogenetic affinity between Rhigonematomorpha and Ascaridomorpha, but inconsistent with morphology‐based phylogenetic hypotheses that suggested a close (taxonomic) relationship between rhigonematomorphs and oxyuridomorphs (pinworms). These observations must be tempered by noting that few rhigonematomorph species have been sequenced and included in phylogenetic analyses, and preliminary studies based on SSU rDNA suggest the group is not monophyletic. Additional mitochondrial genome sequences of rhigonematids are needed to characterize their phylogenetic relationships within Chromadorea, and to increase understanding of mitochondrial genome evolution. 相似文献
399.
400.
Mi Yoon Chung John D. Nason Byung-Yun Sun Myung-Ok Moon Jae Min Chung Chong-Wook Park Myong Gi Chung 《Biochemical Systematics and Ecology》2010
We investigated allozyme variation in 16 populations of the rare monotypic fern Mankyua chejuense and 11 populations of a closely related, widespread fern Botrychium ternatum. Genetic diversity was extremely low in the critically endangered M. chejuense (%Ps = 10%, As = 1.13, and Hes = 0.007) relative to that found in B. ternatum (%Ps = 22.7%, As = 1.23, and Hes = 0.026). We detected homozygous genotypes for alternative alleles at a few loci, which suggests occurrence of intragametophytic self-fertilization. High degrees of population differentiation were found in both M. chejuense (FST = 0.245) and B. ternatum (FST = 0.414).The extremely low levels of genetic diversity in M. chejuense would be attributable to inbreeding coupled with random genetic drift and rarity. In situ protection of habitats of standing populations and ex situ preservation of several populations are suggested for the development of conservation strategies for M. chejuense. 相似文献