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91.
Genetic relationship between Mongolian and Norwegian horses? 总被引:3,自引:0,他引:3
Human populations of Central Asian origin have contributed genetic material to northern European populations. It is likely that migrating humans carried livestock to ensure food and ease transportation. Thus, eastern genes could also have dispersed to northern European livestock populations. Using microsatellite data, we here report that the essentially different genetic distances DA and (deltamu)2 and their corresponding phylogenetic trees show close associations between the Mongolian native horse and northern European horse breeds. The genetic distances between the northern European breeds and Standardbred/Thoroughbred, representing a southern-derived source of horses, were notably larger. We suggest that contribution of genetic material from eastern horses to northern European populations is likely to have occurred. 相似文献
92.
After substantial investments in research, the Atlantic halibut Hippoglossus hippoglossus is now being cultivated commercially in Norway, Iceland, Scotland and Canada. As with other domesticated species, disease problems have been experienced. This review summarizes the current state of knowledge of diseases of the Atlantic halibut, and their diagnosis, prophylaxis and treatment. In economic terms, the most important losses have been suffered at the larval and juvenile stages. The most important infections are caused by nodaviruses, causative agents of Viral Encephalopathy and Retinopathy (VER), which are the major reason why Norway's production of halibut fry has been level since 1995. An aquatic birnavirus, Infectious Pancreatic Necrosis Virus, is also an important agent of mortality. Vibrio anguillarum, Flexibacter ovolyticus and atypical Aeromonas salmonicida are the major bacterial pathogens. The protozoan parasites recorded include Ichthyobodo sp., the microsporidium Enterocytozoon sp., Trichodina hippoglossi, and the metazoan pathogens include myxozoans, helminths, Entobdella hippoglossi, Lepeophtheirus hippoglossi and other parasitic copepods. Experimental vaccines have been tested against V anguillarum and atypical A. salmonicida, with good results. A recombinant vaccine against nodaviruses is under development. A few trials have been carried out on non-specific immunostimulants, but no such treatment is currently available. A number of efficacy and pharmacokinetic trials with various antibacterial agents have also been published. 相似文献
93.
The histone gene H1t is expressed exclusively in pachytene spermatocytes of the testis. In this report we have eliminated the single copy H1t gene by homologous recombination from the mouse genome to analyse the function of the H1t protein during spermatogenesis. Mice homozygous for the mutated H1t gene locus developed normally and showed no anatomic abnormalities until the adult stage. In addition, H1t-deficient mice were fertile and reproduced as wild-type mice. The process of spermatogenesis and the testicular morphology remained unchanged in the absence of H1t. RNase protection analysis demonstrated that H1.1, H1.2 and H1.4 histone gene expression is enhanced during spermatogenesis in H1t-deficient mice. 相似文献
94.
RNA performs a remarkable range of functions in all cells. In addition to its central role in information transfer from DNA to protein, it is essential for functions as diverse as RNA processing, chromosome end-maintenance and dosage compensation. The versatility of RNA derives from its unique ability to use direct readout via base-pairing for sequence specific targeting (or templating) in combination with its capacity to form elaborate three dimensional structures. Such structures can perform catalysis or serve as protein recognition surfaces. In this short review, we attempt to give a flavor for the diversity of functional RNAs in the cell and highlight, using selected examples, two quite distinct activities, catalysis and sequence specific targeting. Within each section, we discuss how the lessons we have learned from these systems may apply to other, less well understood, RNAs. 相似文献
95.
Sister chromatid cohesion and recombination in meiosis 总被引:10,自引:0,他引:10
Sister chromatids are associated from their formation until their disjunction. Cohesion between sister chromatids is provided
by protein complexes, of which some components are conserved across the kingdoms and between the mitotic and meiotic cell
cycles. Sister chromatid cohesion is intimately linked to other aspects of chromosome behaviour and metabolism, in particular
chromosome condensation, recombination and segregation. Recombination, sister chromatid cohesion and the relation between
the two processes must be regulated differently in mitosis and meiosis. In meiosis, cohesion and recombination are modified
in such a way that reciprocal exchange and reductional segregation of homologous chromosomes are ensured.
Received: 11 October 1999; in revised form: 3 December 1999 / Accepted: 6 December 1999 相似文献
96.
Genomic Analysis Reveals Chromosomal Variation in Natural Populations of the Uncultured Psychrophilic Archaeon Cenarchaeum symbiosum 总被引:3,自引:0,他引:3 下载免费PDF全文
Christa Schleper Edward F. DeLong Christina M. Preston Robert A. Feldman Ke-Ying Wu Ronald V. Swanson 《Journal of bacteriology》1998,180(19):5003-5009
Molecular phylogenetic surveys have recently revealed an ecologically widespread crenarchaeal group that inhabits cold and temperate terrestrial and marine environments. To date these organisms have resisted isolation in pure culture, and so their phenotypic and genotypic characteristics remain largely unknown. To characterize these archaea, and to extend methodological approaches for characterizing uncultivated microorganisms, we initiated genomic analyses of the nonthermophilic crenarchaeote Cenarchaeum symbiosum found living in association with a marine sponge, Axinella mexicana. Complex DNA libraries derived from the host-symbiont population yielded several large clones containing the ribosomal operon from C. symbiosum. Unexpectedly, cloning and sequence analysis revealed the presence of two closely related variants that were consistently found in the majority of host individuals analyzed. Homologous regions from the two variants were sequenced and compared in detail. The variants exhibit >99.2% sequence identity in both small- and large-subunit rRNA genes and they contain homologous protein-encoding genes in identical order and orientation over a 28-kbp overlapping region. Our study not only indicates the potential for characterizing uncultivated prokaryotes by genome sequencing but also identifies the primary complication inherent in the approach: the widespread genomic microheterogeneity in naturally occurring prokaryotic populations. 相似文献
97.
Elena I. Mikhailova Tomás Naranjo Ken Shepherd Jannie Wennekes-van Eden Christa Heyting J. Hans de Jong 《Chromosoma》1998,107(5):339-350
The Ph1 locus in wheat influences homo(eo)logous chromosome pairing. We have analysed its effect on the behaviour and morphology
of two 5RL rye telosomes in a wheat background, by genomic in situ hybridisation (GISH), using rye genomic DNA as a probe.
Our main objective was to study the effect of different alleles of the Ph1 locus on the morphology and behaviour of the rye telosomes in interphase nuclei of tapetal cells and in pollen mother cells
at early stages of meiosis. The telosomes, easily detectable at all stages, showed a brightly fluorescing chromomere in the
distal region and a constriction in the proximal part. These diagnostic markers enabled us to define the centromere and telomere
regions of the rye telosomes. In the presence of functional copies of Ph1, the rye telosomes associated at pre-leptotene, disjoined and reorganised their shape at leptotene, and became fully homologously
paired at zygotene – pachytene. In plants without functional alleles (ph1bph1b), the rye telosomes displayed an aberrant morphology, their premeiotic associations were clearly disturbed and their pairing
during zygotene and pachytene was reduced and irregular. The Ph1 locus also influenced the behaviour of rye telosomes in the interphase nuclei of tapetal cells: in Ph1Ph1 plants, the rye telosomes occupied distinct, parallel-oriented domains, whereas in tapetal nuclei of ph1bph1b plants they were intermingled with wheat chromosomes and showed a heavily distorted morphology. The results shed new light
on the effect of Ph1, and suggest that this locus is involved in chromosome condensation and/or scaffold organisation. Our explanation might account
for various apparently contradictory and pleiotropic effects of this locus on both premeiotic associations of homologues,
the regulation of meiotic homo(eo)logous chromosome pairing and synapsis, the resolution of bivalent interlockings and centromere
behaviour.
Received: 27 April 1998; in revised form: 5 August 1998 / Accepted: 11 August 1998 相似文献
98.
Ribosomal DNA from eight species of microsporidians infecting fish have been sequenced. Seven of these species infect the skeletal muscle of fish ( Pleistophora spp.) and one species infects migratory mesenchyma cells ( Glugea anomala ). These sequences, in addition to other available microsporidian rDNA sequences from a broad range of host taxa, have been used in phylogenetic analysis. This analysis revealed that muscle-infecting microsporidians from fish are a polyphyletic group, indicating that characters supposed to be important in the classification of the genus Pleistophora have to be re-evaluated. One character that probably has a polyphyletic origin is the amorphous coat, which has been extensively used in the definition of this genus. Furthermore, our results showed that the insect parasitizing Pleistophora spp. are not related to the true pleistophorans parasitic in skeletal muscle of fish. Phylogenetic analysis of small subunit rDNA sequences revealed disagreements between the molecular phylogeny and classifications based upon ultrastruclure. Many of the morphological characters claimed to be important in microsporidian classifications appeared to have arisen several times during evolution: for example, the diplokaryon and sporophorous vesicles. 相似文献
99.
Abrotanella forsterioides afrorded euparin, 6-hydroxytremetone and three 6-hydroxytoxol esters, one of them not being isolated previously. Furthermore a seco-triterpene was isolated. The tribal position of the genus Abrotanella in the Compositae is still an unsolved problem. Morphological investigations suggest that this genus should be transferred from the tribe Anthemideae to the Senecioneae [1,2]. So far two species have been studied chemically; one atforded ent-kaurane derivatives, while both contained euparin and hydroxytremetone [3]. 相似文献
100.
Rasmus Skern-Mauritzen Petter Frost Sussie Dalvin Bj?rn Olav Kvamme Ingunn Sommerset Frank Nilsen 《BMC molecular biology》2009,10(1):44