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1.
Evolution of the cytochromeb gene of mammals   总被引:98,自引:0,他引:98  
Summary With the polymerase chain reaction (PCR) and versatile primers that amplify the whole cytochromeb gene (∼ 1140 bp), we obtained 17 complete gene sequences representing three orders of hoofed mammals (ungulates) and dolphins (cetaceans). The fossil record of some ungulate lineages allowed estimation of the evolutionary rates for various components of the cytochromeb DNA and amino acid sequences. The relative rates of substitution at first, second, and third positions within codons are in the ratio 10 to 1 to at least 33. For deep divergences (>5 million years) it appears that both replacements and silent transversions in this mitochondrial gene can be used for phylogenetic inference. Phylogenetic findings include the association of (1) cetaceans, artiodactyls, and perissodactyls to the exclusion of elephants and humans, (2) pronghorn and fallow deer to the exclusion of bovids (i. e., cow, sheep, and goat), (3) sheep and goat to the exclusion of other pecorans (i. e., cow, giraffe, deer, and pronghorn), and (4) advanced ruminants to the exclusion of the chevrotain and other artiodactyls. Comparisons of these cytochromeb sequences support current structure-function models for this membrane-spanning protein. That part of the outer surface which includes the Qo redox center is more constrained than the remainder of the molecule, namely, the transmembrane segments and the surface that protrudes into the mitochondrial matrix. Many of the amino acid replacements within the transmembrane segments are exchanges between hydrophobic residues (especially leucine, isoleucine, and valine). Replacement changes at first and second positions of codons approximate a negative binomial distribution, similar to other protein-coding sequences. At four-fold degenerate positions of codons, the nucleotide substitutions approximate a Poisson distribution, implying that the underlying mutational spectrum is random with respect to position.  相似文献
2.
用桑蚕(包括不同生态地理品种59个及野桑蚕)和桑属植物(包括12个种和2个变种)两类截然不同的材料,探讨了分子系统学研究中RAPD分子位点数与遗传差异信息可靠性间的关系。发现:(1)所分析的位点数多少与所能提供系统信息的量及可靠性之间有明显的关系;(2)当位点数在20以下时,得到的遗传差异的结果极不可靠,随着位点数的增加所提供的信息量及可靠性增加。当位点数超过70个时,所提供的信息可靠性趋于稳定;(3)对桑蚕和桑属植物两种截然不同的材料的分析,均得相似结果。由此推论:在用RAPD进行生物系统学研究中,以分析70个左右位点数为好;这一结论受研究对象的影响小,在其它类似的研究中或许具有一定的参考价值。 Abstract:We studied the correlation between the number of RAPD-loci investigated and the reliability of the information on genetic variation analysis using quite different two-kind materials,silkworms(including 59 geographic varieties of Bombyx mori belonging to different ecotype,as well as Bombyx mandarina M.)and mulberries(including 12 species and 2 varieties).The results showed as follows:(1)There was obvious correlation between the numbers of RAPD-loci investigated and the reliability of the information on genetic variation analysis.(2)The data were not suitable for the genetic variation analysis when the number of RAPD-loci in vestigated was smaller than 20.The more RAPD loci were analyzed,the more accurate genetic diversity would be identified when the number of the locus was varied from 20 to 70.Furthermore,the stable information to be available is shown when the number exceeded 70.(3)The similar regularities mentioned above were observed in both silkworm and mulberry.In order to get reliable information of genetic variation in molecular phylogenetic studies,at least 70 RPD loci would be investigated.And the results obtained in this study might be referential for AFLP and RFLP analysis.  相似文献
3.
经克隆测序获得我国七丝鲚(Coilia grayii)、凤鲚(Cmystus)、刀鲚(C.nasus)和短颌鲚(C.brachygnathus)以及太湖湖鲚(C.nasus taihuensis)等4个种和1亚种32尾个体的mtDNAD.100pN全序列,以日本鲲(Engraulisjaponicus)和秘鲁鳗(E.ringens)为外类群构建了中国鲚属的分子系统发育树,并讨论了短颌鲚和湖鲚的物种有效性。结果显示,七丝鲚的D-loop区全序列长1,208bp,凤鲚1,279-1,361bp,刀鲚1,252-1,290bp,短颌鲚1,214-1,252bp,湖鲚1,252-1,442bp,除七丝鲚外的其他种类个体问均表现出序列长度的多态性。短颌鲚、刀鲚和湖鲚三者问的平均K2.P遗传距离仅为0.011-10.020,明显小于它们与风鲚、七丝鲚及外类群问的遗传距离(0.051-0.349)。以邻接法和最大简约法构建的系统发育树表明,刀鲚、短颌鲚及湖鲚均未各自构成单系,而是共同构成一个单系群,三者并未发生显著分化。研究表明,短颌鲚和湖鲚为刀鲚的淡水生态型种群,并非有效物种。系统发育分析表明,中国鲚属3个有效物种问以风鲚最为原始,刀鲚和七丝鲚为姐妹群,处于较进化的位置。推测风鲚可能是鲚属祖先种最早从起源中心扩散到西北太平洋的后裔,而刀鲚和七丝鲚则是凤鲚在演化过程中分别适应寒冷和温暖气候而分化出的物种。  相似文献
4.
5.
从12S rRNA基因序列研究中国蛙科24种的进化关系   总被引:23,自引:0,他引:23  
测定了中国蛙科动物24种和蟾蜍科的中华大蟾蜍线粒体12S rRNA基因长约400bp片段的序列。采用邻接法,对其数据的系统发生分析表明24种可分成3个支系:第一个支系包括棘腹蛙、合江棘蛙、棘胸蛙、大头蛙、虎纹蛙、倭蛙、泽陆蛙共7种,其中3种棘蛙组成一个单系;第二个支系由3种湍蛙,即戴云湍蛙、华南湍蛙和武夷湍蛙组成,应属于湍蛙亚科;第三支系包含余下的14种蛙,其中5种林蛙和4种臭蛙分别组成一个单系;2种侧褶蛙先聚合后,再与弹琴水蛙聚合,2种粗上先聚合在一起,再与由林蛙组成的单系群聚合。第三支系首先与第二支系相聚,然后它们与第一支系形成姐妹群,即由蛙亚科的7个物种组成的第一支系,不与蛙亚科另14个物种组成的第三支系直接聚合,表明第一支系的物种可能不属于蛙亚科。此外,分子证据提示把陆蛙属、大头蛙属、虎纹蛙属、棘棘属、臭蛙属、粗皮蛙属和侧褶蛙属从原来的蛙属分出有其合理性。、  相似文献
6.
矮岩羊的分类地位从它被发现后就一直存在着争议。本文测定了分别来自四川和青海的岩羊(Pseudois nayaur)和矮岩羊(Pseudois schaeferi)共7个个体的Cyt b基因全序列(1140bp),结合山羊(Capra hircus)、北山羊(Capra ibex)、绵羊(Ovis aries)和盘羊(Ovis ammon)同源DNA序列进行比较,分析了碱基组成和变异情况以及核苷酸序列差异。用简约法和距离距阵法构建了分子系统树,得到了相同的拓扑结构。结果显示:岩羊和矮岩羊互为单系群,有着较山羊、北山羊、绵羊和盘羊间更近的亲缘关系,它们之间的序列差异(Cyt b=3.2%)低于牛科不同种间的序列差异水平(8.3%-12.1%),明显高于种内个体的序列差异,而处于牛科亚种的序列差异范围内。因此,推测矮岩羊与岩羊之间的差异可能已经达到了亚种的水平。它们的分歧时间为l-3百万年[动物学报49(2):198—204,2003]。  相似文献
7.
The phylogenetic relationships of 106 European cyprinid taxa were determined based on the complete nucleotide sequence (1140 bp) of the mitochondrial cytochrome b gene. The molecular phylogeny was used (1) to revise the current systematics of European cyprinids, (2) to establish the phylogenetic utility of traditional morphological characters that are widely used in Cyprinidae systematics, and (3) to discuss alternative hypotheses on the biogeography of the family in Europe. The age of the major lineages within European cyprinids was tentatively estimated with a molecular clock and showed full agreement with the fossil record of the group. Moreover, the results provided unambiguous evidence for a close phylogenetic affinity of some Caucasian and Greek endemic cyprinid taxa (e.g., B. capito and B. brachycephalus and Leuciscus keadicus, Barbus graecus, and B. albanicus, respectively) to Iberian and North African, but not Central European, cyprinids. The existence of such unexpected phylogenetic relationships refutes the classical hypothesis on the biogeography of European cyprinids, which assumes a dispersal of the cyprinid fauna from central Europe to southern Europe and northern Africa during the Miocene (and, hence, predicts a close phylogenetic relationship of all Caucasian, Greek, Iberian, and North African cyprinids to central European taxa). Instead, the existence of a Mediterranean realm independent of the central European route seems plausible based on the molecular evidence. It is likely that the new biogeographical scenario proposed here might apply to other primary freshwater European animals with low dispersal abilities, including fish, amphibians, and invertebrates. Received: 2 February 1999 / Accepted: 16 March 1999  相似文献
8.
蝗总科部分种类16S rDNA的分子系统发育关系   总被引:20,自引:0,他引:20  
将自测的我国直翅目蝗总科8科8个种和从互联网GenBank中检索到相关物种的线粒体基因组:16S rDNA序列片段进行同源性比较,计算核苷酸使用频率,并构建分子系统树。在获得的480bp的序列中。A T约占70.7%,G C为29.3%,颠换取代(transversion)的速率大于或接近转换取代(transition)的速率,其中188个核苷酸位点存在变异。研究结果表明:在直翅目蝗总科有差异的188bp中,属内种间的碱基序列差异仅为1.5%,科内属间为3.5%~3.6%,科间差异为4.8%~15.8%,亚目间差异达到15.2%~25.6%。分子系统树表明:科内的属和属内的种均优先聚在一起;蝗总科8科的起源关系为:锥头蝗科→瘤锥蝗科→癞蝗科→斑翅蝗科→剑角蝗科→网翅蝗科和槌角蝗科→斑腿蝗科;锥头蝗科与瘤锥蝗科关系较近,是蝗总科内最原始的类群;槌角蝗科和网翅蝗科互为姐妹群,与最进化的斑腿蝗科关系较近;蚤蝼科为独立的一支,最先分出,似为一个亚目,与现用的分类系统有明显差别;哈螽科(螽嘶总科)和蟋蟀科聚在一起为剑瓣亚目(Ensifera),蚱科和蝗总科的8科组成短瓣亚目(Caehfera),同现用的分类系统。  相似文献
9.
Wink M 《Phytochemistry》2003,64(1):3-19
Secondary metabolites, at least the major ones present in a plant, apparently function as defence (against herbivores, microbes, viruses or competing plants) and signal compounds (to attract pollinating or seed dispersing animals). They are thus important for the plant's survival and reproductive fitness. Secondary metabolites therefore represent adaptive characters that have been subjected to natural selection during evolution. Molecular phylogenies of the Fabaceae, Solanaceae and Lamiaceae were reconstructed and employed as a framework to map and to interpret the distribution of some major defence compounds that are typical for the respective plant families; quinolizidine alkaloids and non-protein amino acids for legumes; tropane and steroidal alkaloids for Solanaceae, and iridoids and essential oils for labiates. The distribution of the respective compounds appears to be almost mutually exclusive in the families studied, implying a strong phylogenetic and ecological component. However, on a closer look, remarkable exceptions can be observed, in that certain metabolites are absent (or present) in a given taxon, although all the neighbouring and ancestral taxa express (or do not express, respectively) the particular trait. It is argued that these patterns might reflect differential expression of the corresponding genes that have evolved earlier in plant evolution. The inconsistent secondary metabolite profiles mean that the systematic value of chemical characters becomes a matter of interpretation in the same way as traditional morphological markers. Thus, the distribution of secondary metabolites has some value for taxonomy but their occurrence apparently reflects adaptations and particular life strategies embedded in a given phylogenetic framework.  相似文献
10.
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