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1.
Modern nutritional studies have found that diverse diets are linked to lower infant mortality rates and longer life expectancies in humans. This is primarily because humans require more than fifty essential nutrients for growth and cell maintenance and repair; most of these essential nutrients must come from outside food sources rather than being manufactured by the body itself; and a diversity of food types is required to consume the full suite of essential nutrients necessary for optimal human health. These principles and their related affects on human adaptations and demography are the hallmarks of a theoretical paradigm defined as nutritional ecology. This essay applies concepts derived from nutritional ecology to the study of human evolution. Principles of nutritional ecology are applied to the study of the Middle‐to‐Upper Paleolithic transition in order to broadly illustrate the interpretive ramifications of this approach. At any stage in human evolution, those hominid populations that chose to diversify their subsistence base may have had a selective advantage over competitors who restricted their diet principally to one food type, such as terrestrial mammals. 相似文献
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The regenerating scale and tissues comprising the scale pocket of Fundulus olivaceus were examined microscopically at specific intervals. Scale removal resulted in a thickening of the epidermis which persisted through the early stages of regeneration. This thickening was due in part to the appearance of columnar basal cells which divided producing cells that became mucous cells and squamous cells. The scale regenerated as a relatively large plate of bone which first appeared between layers of scleroblasts on the floor of the scale pocket and then grew producing circuli and radii. By the fourth day of regeneration, calcium was observed in the cytoplasm of the scleroblasts and at randomly distributed foci in the osseous portion of the scale. The osseous layer was completely calcified by 15 days of regeneration. 相似文献
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The genetic diversity at the ELA DQβ locus was investigated using polymerase chain reaction and DNA sequencing. Based upon serological methods 16 class II homozygous animals were selected and their genomic DNA was used. A DQβ gene from an equine cDNA library was also sequenced. Our methology and the similarity between the genomic and the cDNA sequences suggest that the studied locus is expressed on equine lymphocytes. In the predicted amino acid sequence the most extensive variation is located at residues 56–60. The pattern of these five amino acids is strongly correlated to the serological ELA class II specificities (W13, W22, W23, Be200). The alleles corresponding to the W23 specificity are the most divergent among the equine DQβ alleles and also from other mammalian DQβ sequences. 相似文献
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Human noroviruses (HuNoV) are a major cause of nonbacterial gastroenteritis worldwide, yet details of the life cycle and replication of HuNoV are relatively unknown due to the lack of an efficient cell culture system. Studies with murine norovirus (MNV), which can be propagated in permissive cells, have begun to probe different aspects of the norovirus life cycle; however, our understanding of the specific functions of the viral proteins lags far behind that of other RNA viruses. Genome-wide functional profiling by insertional mutagenesis can reveal protein domains essential for replication and can lead to generation of tagged viruses, which has not yet been achieved for noroviruses. Here, transposon-mediated insertional mutagenesis was used to create 5 libraries of mutagenized MNV infectious clones, each containing a 15-nucleotide sequence randomly inserted within a defined region of the genome. Infectious virus was recovered from each library and was subsequently passaged in cell culture to determine the effect of each insertion by insertion-specific fluorescent PCR profiling. Genome-wide profiling of over 2,000 insertions revealed essential protein domains and confirmed known functional motifs. As validation, several insertion sites were introduced into a wild-type clone, successfully allowing the recovery of infectious virus. Screening of a number of reporter proteins and epitope tags led to the generation of the first infectious epitope-tagged noroviruses carrying the FLAG epitope tag in either NS4 or VP2. Subsequent work confirmed that epitope-tagged fully infectious noroviruses may be of use in the dissection of the molecular interactions that occur within the viral replication complex. 相似文献
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A novel assay of single-cell exogenous beta-galactosidase activity in Saccharomyces cerevisiae has been developed. Intracellular fluorescence due to the hydrolysis of resorufin-beta-D-galactopyranoside attains a steady state between production of resorufin and its subsequent leakage from the cell. The cells are permeabilized with Triton X-100, and the assay is performed at 0 degrees C. These conditions were chosen to minimize intercellular fluorescence communication. Free resorufin in the extracellular space is bound by bovine serum albumin to prevent its uptake by cells. Two regimes of fluorescence accumulation are observed, one limited by the rate of diffusion of substrate into the cell, and one limited by the rate of enzymatic cleavage of the substrate. A quantitative correlation between fluorescence and beta-galactosidase activity is obtained under optimized assay conditions. 相似文献
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Bryan M. Turner 《Chromosoma》1982,87(3):345-357
A mouse monoclonal IgM antibody against the core histone H2B has been shown, by indirect immunofluorescence, to stain metaphase chromosomes from a variety of cultured cell types. Experiments carried out with human HeLa cells showed that the intensity of staining varied along the length of chromosome arms giving in some cases a rudimentary banded staining pattern. Considerable variation in staining intensity was noted between individual chromosomes and between different metaphase spreads. It was noted that chromosomes having a more swollen appearance stained more intensely than those with a more compact structure, which were often unstained. Preincubation of unfixed metaphase chromosomes in buffered salt solutions virtually eliminated the cell to cell and chromosome to chromosome variation in staining, even when no visible effect on chromosome morphology was caused by such treatment. It is concluded that the determinant recognised by antibody HBC-7 is ubiquitous but is inaccessible in some chromosomes or chromosome regions. Digestion of purified chromatin (primarily interphase) with DNAase 1 or micrococcal nuclease resulted in a several-fold increase in the binding of antibody HBC-7 measured by solid-phase radioimmunoassay. This increase was abolished by subsequent treatment with trypsin, which suggests that the antigenic determinant recognised by antibody HBC-7 lies in the trypsin-sensitive N-terminal region of nucleosomal H2B. As the cationic N-terminal regions of the core histones are involved in DNA binding, it is likely that the accessibility of the determinant recognised by antibody HBC-7 is influenced by the relationship between the core histones and their associated DNA. 相似文献
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Abstract Immunoblotting profiles of whole or protease-K-digested organisms with homologous antisera demonstrated the presence of a characteristic ladder pattern of smooth LPS in Treponema phagedenis . Periodic acid silver staining of SDS-PAGE gels confirmed these findings. However, when heterologous or homologous serum was reacted with Treponema pallidum , no such pattern or cross-reactions were observed. The significance of apparent absence of LPS in T. pallidum is discussed. 相似文献
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Simultaneous growth and riboflavin overproduction were investigated using a previously developed stoichiometric model of Bacillus subtilis metabolism. A fit of model predictions to experimental data was used to obtain estimates of fundamental energetic parameters of B. subtilis. Although multiple solutions describe the experimental data, evidence for a P-to-O ratio of about 1(1/3) mole of ATP produced per atom of oxygen consumed in oxidative phosphorylation was provided by genomic analysis of electron transport components, because no homologue of the proton-translocating NADH dehydrogenase I was found in the B. subtilis genome database. These results allow us to devise a rational metabolic engineering strategy to improve riboflavin production. The potential influence of increased energy coupling in oxidative phosphorylation on riboflavin yield is discussed. Higher coupling is most significant under carbon-limiting conditions in slow-growing cells, that is, in fed-batch processes of industrial interest. 相似文献