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11.
Isolation and biochemical characterization of partially transformation-defective mutants of avian myelocytomatosis virus strain MC29: localization of the mutation to the myc domain of the 110,000-dalton gag-myc polyprotein 总被引:10,自引:11,他引:10 下载免费PDF全文
Recently, we isolated three mutants of MC29 virus which, although able to transform fibroblasts with the same efficiency as wild-type MC29, were 100-fold less efficient at transforming macrophages. In this study we found that MC29-transformed quail producer cell line Q10 was able to generate these partially transformation defective mutants at a high frequency. Using tryptic peptide mapping, we determined that the smaller gag-myc polyproteins encoded by the transformation-defective viruses had lost myc-specific tryptic peptides. This suggested that the mutations which resulted in the transformation-defective viruses being inefficient at transforming macrophages were located in the v-myc sequence and thus directly implicated v-myc and the gag-myc polyprotein in transformation by MC29. 相似文献
12.
13.
Single anion channels reconstituted from cardiac mitoplasts 总被引:4,自引:0,他引:4
Ion channels from sheep cardiac mitoplast (inverted inner mitochondrial membrane vesicle) preparations were incorporated into
voltage-clamped planar lipid bilayers. The appearance of anion rather than cation channels could be promoted by exposing the
bilayers to osmotic gradients formed by Cl− salts of large, relatively imperment, cations at a pH of 8.8. Two distinct activities were identified. These comprised a
multisubstate anion channel of intermediate conductance (∼60 pS in 300vs. 50mm choline Cl, ∼100 pS in symmetric 150mm KCl), and a lower-conductance anion channel (∼25 or ∼50 pS in similar conditions), which only displayed two well-defined
substates, at ∼25 and ∼50% of the fully open state. The larger channels were not simple multiples of the lower-conductance
channels, but both discriminated poorly, and to a similar extent, between anions and cations (PCl
−/Pcholine
+ ∼12, PCl
−/PK
+∼8). The lower-conductance channel was only minimally selective between different anions (PNO
3
−
(1.0)=PCl
−>PBr
−>PI
−>PSCN
−(0.8)), and its conductance failed to saturate even in high (>1.0 M) activities of KCl. The channels were not obviously voltage
dependent, and they were unaffected by 0.5 mM SITS, H2O2, propranolol, quinine or amitriptyline, or by 2 mM ATP, or by variations in pH (5.5–8.8). Ca2+ and Mg2+ did not alter single channel activity, but did modify single current amplitudes in the lower-conductance channel. This effect,
together with voltage-dependent substate behavior, is described in the following paper. 相似文献
14.
Abnormal B-cell responses to chemokines, disturbed plasma cell localization, and distorted immune tissue architecture in Rgs1-/- mice 下载免费PDF全文
Normal lymphoid tissue development and function depend upon chemokine-directed cell migration. Since chemokines signal through heterotrimeric G-protein-coupled receptors, RGS proteins, which act as GTPase-activating proteins for Galpha subunits, likely fine tune the cellular responses to chemokines. Here we show that Rgs1(-/-) mice possess B cells that respond excessively and desensitize improperly to the chemokines CXCL12 and CXCL13. Many of the B-cell follicles in the spleens of Rgs1(-/-) mice have germinal centers even in the absence of immune stimulation. Furthermore, immunization of these mice leads to exaggerated germinal center formation; partial disruption of the normal architecture of the spleen and Peyer's patches; and abnormal trafficking of immunoglobulin-secreting cells. These results reveal the importance of a regulatory mechanism that limits and desensitizes chemokine receptor signaling. 相似文献
15.
Michael J. Hayman Gary M. Ramsay Keith Savin Gay Kitchener Thomas Graf Hartmut Beug 《Cell》1983,32(2):579-588
Avian erythroblastosis virus causes erythroid leukemia and sarcomas in chickens. The viral oncogene responsible for these diseases, erb, is divided into two regions known as erbA and erbB, and recent evidence suggests that it is the erbB gene that is responsible for the transforming activity. From rats bearing avian erythroblastosis virus-induced sarcomas, we have obtained antisera which are specific for the erb gene products. Using such antisera, we have been able to characterize the erbB gene product as a 68,000 molecular weight protein. Pulse-chase and cell-free in vitro translation experiments show that the initial product is a 62,500 dalton protein which is initially modified to a 66,000 dalton protein, and then further modified to a 68,000 dalton form. These modifications could be shown to be associated with glycosylation and phosphorylation. Cell fractionation experiments revealed that the 66,000 and 68,000 dalton proteins were located in cell membrane fractions, and immunofluorescence results showed the erbB gene product to be expressed on the cell surface. 相似文献
16.
The oncoprotein Ski represses transforming growth factor (TGF)-beta signaling in an N-CoR-independent manner. However, the molecular mechanism(s) underlying this event has not been elucidated. Here, we identify an additional domain in Ski that mediates interaction with Smad3 which is important for this repression. This domain is distinct from the previously reported N-terminal Smad3 binding domain in Ski. Individual alanine substitution of several residues in the domain significantly affected Ski-Smad3 interaction. Furthermore, combined mutations within this domain, together with those in the previously identified Smad3 binding domain, can completely abolish the interaction of Ski with Smad3, while mutation in each domain alone retained partial interaction. By introducing those mutations that abolish direct interaction with Smad3 or Smad4 individually, or in combination, we show that interaction of Ski with either Smad3 or Smad4 is sufficient for Ski-mediated repression of TGF-beta signaling. Furthermore our results clearly demonstrate that Ski does not disrupt Smad3-Smad4 heteromer formation, and recruitment of Ski to the Smad3/4 complex through binding to either Smad3 or Smad4 is both necessary and sufficient for repression. 相似文献
17.
Parallel mosaicism of supernumerary chromosomes and sex chromosomes in Echymipera kalabu (Marsupialia) 总被引:1,自引:0,他引:1
Echymipera kalabu (Peramelidae: Marsupialia) does not have the full chromosome complement in all its adult somatic tissues. The chromosomes missing are the Y-chromosome in the male and an X-chromosome in the female. The full complement is present in the corneal epithelium and the reproductive tissue. A parallel mosaicism to this exists with respect to small supernumerary chromosomes which are found in certain animals of this species. These supernumeraries must be subject to the same control system as that which is responsible for the elimination of the sex chromosomes. 相似文献
18.
19.
O Restif DT Hayman JR Pulliam RK Plowright DB George AD Luis AA Cunningham RA Bowen AR Fooks TJ O'Shea JL Wood CT Webb F Adler 《Ecology letters》2012,15(10):1083-1094
Infectious disease ecology has recently raised its public profile beyond the scientific community due to the major threats that wildlife infections pose to biological conservation, animal welfare, human health and food security. As we start unravelling the full extent of emerging infectious diseases, there is an urgent need to facilitate multidisciplinary research in this area. Even though research in ecology has always had a strong theoretical component, cultural and technical hurdles often hamper direct collaboration between theoreticians and empiricists. Building upon our collective experience of multidisciplinary research and teaching in this area, we propose practical guidelines to help with effective integration among mathematical modelling, fieldwork and laboratory work. Modelling tools can be used at all steps of a field-based research programme, from the formulation of working hypotheses to field study design and data analysis. We illustrate our model-guided fieldwork framework with two case studies we have been conducting on wildlife infectious diseases: plague transmission in prairie dogs and lyssavirus dynamics in American and African bats. These demonstrate that mechanistic models, if properly integrated in research programmes, can provide a framework for holistic approaches to complex biological systems. 相似文献
20.