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991.
Gajanan T Behere Wee Tek Tay Derek A Russell David G Heckel Belinda R Appleton Keshav R Kranthi Philip Batterham 《BMC evolutionary biology》2007,7(1):117
Background
Helicoverpa armigera and H. zea are amongst the most significant polyphagous pest lepidopteran species in the Old and New Worlds respectively. Separation of H. armigera and H. zea is difficult and is usually only achieved through morphological differences in the genitalia. They are capable of interbreeding to produce fertile offspring. The single species status of H. armigera has been doubted, due to its wide distribution and plant host range across the Old World. This study explores the global genetic diversity of H. armigera and its evolutionary relationship to H zea. 相似文献992.
993.
The global role of ppGpp synthesis in morphological differentiation and antibiotic production in <Emphasis Type="Italic">Streptomyces coelicolor</Emphasis> A3(2) 下载免费PDF全文
Background
Regulation of production of the translational apparatus via the stringent factor ppGpp in response to amino acid starvation is conserved in many bacteria. However, in addition to this core function, it is clear that ppGpp also exhibits genus-specific regulatory effects. In this study we used Affymetrix GeneChips to more fully characterize the regulatory influence of ppGpp synthesis on the biology of Streptomyces coelicolor A3(2), with emphasis on the control of antibiotic biosynthesis and morphological differentiation. 相似文献994.
Bianca Altvater Silke Landmeier Sibylle Pscherer Jaane Temme Heribert Juergens Martin Pule Claudia Rossig 《Cancer immunology, immunotherapy : CII》2009,58(12):1991-2001
Regulatory NK cell receptors can contribute to antigen-specific adaptive immune responses by modulating T cell receptor (TCR)-induced
T cell activation. We investigated the potential of the NK cell receptor 2B4 (CD244) to enhance tumor antigen-induced activation
of human T cells. 2B4 is a member of the CD2 receptor subfamily with both activating and inhibitory functions in NK cells.
In T cells, its expression is positively associated with the acquisition of a cytolytic effector memory phenotype. Recombinant
chimeric receptors that link extracellular single-chain Fv fragments specific for the tumor-associated surface antigens CD19
and GD2 to the signaling domains of human 2B4 and/or TCRζ were expressed in non-specifically activated peripheral blood T cells by
retroviral gene transfer. While 2B4 signaling alone failed to induce T cell effector functions or proliferation, it significantly
augmented the antigen-specific activation responses induced by TCRζ. 2B4 costimulation did not affect the predominant effector
memory phenotype of expanding T cells, nor did it increase the proportion of T cells with regulatory phenotype (CD4+CD25hiFoxP3+). These data support a costimulatory role for 2B4 in human T cell subpopulations. As an amplifier of TCR-mediated signals,
2B4 may provide a powerful new tool for immunotherapy of cancer, promoting sustained activation and proliferation of gene-modified
antitumor T cells. 相似文献
995.
Aaron G. Carfagnini F. Helen Rodd Kayin B. Jeffers Ashley E. E. Bruce 《Environmental Biology of Fishes》2009,86(3):403-409
Female zebrafish housed in aquaria with spatial complexity (plastic plants) over a 13–16-week period showed reduced levels
of aggressive behavior compared to females in bare tanks. In tanks with plants, there was no relationship between levels of
aggression and fecundity but, in bare tanks, females experiencing the highest levels of aggression showed reduced fecundity.
Our results suggest that it may be beneficial, when maintaining zebrafish at moderate to high densities or working with especially
aggressive strains, to house them in spatially complex conditions. 相似文献
996.
Tetsuya Sakamaki 《Primates; journal of primatology》2009,50(4):321-332
Chimpanzees (Pan troglodytes) form multi-male and multi-female unit groups with fission–fusion grouping patterns. Short-range interaction (SRI) plays
an important role in the unity of these groups and in maintaining social bonds among members. This study evaluated three models
of chimpanzee social structure that differed according to the emphasis each placed on social bonds between the sexes, i.e.,
the male-only, the bisexual, and the male-bonded unit-group model. I investigated differences in SRI between the sexes among
group members in well-habituated wild chimpanzees in Mahale Mountains National Park, Tanzania. I followed six focal adult
males and six females, and quantified their respective SRI with other chimpanzees. Except between subordinate males and adult
females, adults in general engaged in SRI with about 60–90% of the individuals with whom they made visual contact each day,
whether in large or small parties. Although the number of social grooming (SGR) partners was limited, male–male SGR networks
were wider than were either male–female or female–female SGR networks among adults. The number of contact-seeking behavior
(CSB) partners was also limited, but dominant males had more CSB partners. Adult females mainly interacted by pant-grunt greeting
(PGG) with adult males, but tended to do so mainly with the highest-ranking male(s) within visual contact. These results indicated
that the social bonds among adult males were essential to group unity. Because of clear male dominance, adult females established
peaceful coexistence with all group members despite less frequent SRI with subordinate males by maintaining affiliative social
bonds with dominant males, thereby supporting the male-bonded unit-group model. Adult females had many female SRI partners,
but these interactions did not involve performing conspicuous behaviors, suggesting that females maintain social bonds with
other females in ways that differ from how such bonds are maintained with and between adult males. 相似文献
997.
Learning involves a usually adaptive response to an input (an external stimulus or the organism℉s own behaviour) in which
the input-response relation is memorized; some physical traces of the relation persist and can later be the basis of a more
effective response. Using toy models we show that this characterization applies not only to the paradigmatic case of neural
learning, but also to cellular responses that are based on epigenetic mechanisms of cell memory. The models suggest that the
research agenda of epigenetics needs to be expanded. 相似文献
998.
Background
Head and neck cancers (HNC) are relatively common and often very serious diseases in both dogs and humans. Neoplasms originating in the head and neck region are a heterogeneous group. HNC often has an unfavourable prognosis and the proximity of the tissue structures renders extirpation of tumours with sufficient margins almost incompatible with preservation of functionality. In humans oral malignant melanoma (OMM) is extremely rare, but represents a particular challenge since it is highly aggressive as is the canine counterpart, which thus may be of interest as a spontaneous animal model. 相似文献999.
Maurecilne Lemes da Silva Daniela Lopes Paim Pinto Miguel Pedro Guerra Eny Iochevet Segal Floh Cláudio Horst Bruckner Wagner Campos Otoni 《Plant Cell, Tissue and Organ Culture》2009,99(1):47-54
The objective of the present work was to induce somatic embryogenesis from zygotic embryos of Passiflora cincinnata Masters. Zygotic embryos formed calli on media with different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and
4.5 μM benzyladenine (BA) after 30 days of in vitro culture. A concentration of 18.1 μM 2,4-D resulted in the largest number
of somatic embryos. Embryogenic calli were yellowish and friable, forming whitish proembryogenic masses. Morphologically,
embryogenic cells were small and had large nuclei and dense cytoplasm, whereas non-embryogenic cells were elongated, with
small nuclei and less dense cytoplasm. Calli cultured under white light on basal Murashige and Skoog’s medium with activated
charcoal produced embryos in all developmental stages. There were differences among the treatments, with some leading to the
production of calli with embryos and some only to callus formation. Some abnormalities were associated with somatic embryos,
including fused axes, fused cotyledons and polycotyledonary embryos. Production of secondary somatic embryos occurred in the
first cycle of primary embryo development. Secondary embryos differentiated from the surface of the protodermal layer of primary
embryos with intense cell proliferation, successive mitotic divisions in the initial phase of embryoid development, and a
vascular system formed with no connection to the parental tissue. This secondary embryogenic system of P. cincinnata is characterized by intense proliferation and maintenance of embryogenic competence after successive subcultures. This reproducible
protocol opens new prospects for massive propagation and is an alternative to the current organogenesis-based transformation
protocol. 相似文献
1000.