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1.
Interaction specificity of the anthracycline antibiotics violamycin BI and violamycin BII in respect to A.T and G.C pairs was investigated. For comparison denaturation of complexes with A.T and G.C specific ligands distamycin A and actinomycin D are presented. Making use of the least squares hyperchromic spectra measured in the course of thermal denaturation were partitioned into the components corresponding to the melting of A.T and G.C base pairs and dissociation of ligand. The mutual dependence of AT and GC denaturation allows one to draw conclusions about specificity of interaction. In case of both violamycins only slight preference of interaction with AT-rich regions was detected. The dissociation of violamycin BII in the latest stage of thermal denaturation was found to be cooperative. 相似文献
2.
Valéria Marques Gabriel Riaño Miguel A. Carretero Iolanda Silva-Rocha Catarina Rato 《Acta zoologica》2023,104(3):419-433
Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change. 相似文献
3.
Phytoplankton production and biomass at frontal zones in the Atlantic sector of the Southern Ocean 总被引:4,自引:3,他引:1
A high resolution study of chlorophyll a and primary production distribution was carried out in the Atlantic sector of the Southern Ocean during the austral summer of 1990–91. Primary production (14C assimilation) and photosynthetic capacity levels at frontal systems were among the highest recorded during the cruise (2.8–6.3 mgC·m–3·h–1, and 1.3–4.7mgC·mgChl a
–1·h–1, respectively). Blooms at ocean fronts were strongly dominated by specific size classes and species. This suggests that the increase in biomass was probably the result of an enhancement of in situ production by selected components of the phytoplankton assemblage, rather than accumulation of cells through hydrographic forces. This hypothesis is supported by the high variability of photosynthetic capacities at adjacent stations along the transects. Blooms (ca 2.7–3.5 mg Chl a·m–3) were found at three oceanic fronts (the Subtropical, Subantarctic and Antarctic Polar Fronts) during the early summer. These were equivalent to, or denser than, blooms in the Marginal Ice Zone and at the Continental Water Boundary. Seasonal effects on phytoplankton community structure were very marked. In early summer (December), netphyto-plankton (>20 m) was consistently the major component of the frontal blooms, with the chain-forming diatoms Chaetoceros spp. and Nitzschia spp. dominating at the Subantarctic and Antarctic Polar Fronts, respectively. During late summer (February), nanophytoplankton (1–20 m) usually dominated algal communities at the main frontal areas. Only at the Antarctic Polar Front did netphytoplankton dominate, with the diatom component consisting almost exclusively of Corethron criophilum. An early to late summer shift of maximum phytoplankton biomass from north to south of the Antarctic Polar Front was observed. Spatial covariance between silicate levels and water-column stability appeared to be the main factor controlling phytoplankton production at the Antarctic Polar Front. Low silicate concentrations may have limited diatom growth at the northern edge of the front, while a deep mixed layer depth reduced production at the southern edge of the front. 相似文献
4.
Summary In a sibship of ten children descending from a first cousin's marriage, two sibs were affected by Kartagener's syndrome with the typical symptoms of situs inversus, bronchiectasis, and polyposis nasi. Clinical investigation of the entire family revealed chronic infections of the paranasal sinus in five sibs and the mother, two of whom had bronchiectasis as well. Immunologically, a persistent cellular or humoral defect could not be detected in any of the family members. In the HLA system, only the two sibs with Kartagener's syndrome had identical HLA types; all other family members had different combinations. A linkage between the loci for the HLA system and Kartagener's syndrome is discussed. 相似文献
5.
Colletotrichum species complexes are among the top 10 economically important fungal plant pathogens worldwide because they can infect climacteric and nonclimacteric fruit at the pre and/or postharvest stages. C. truncatum is the major pathogen responsible for anthracnose of green and red bell pepper fruit worldwide. C. brevisporum was recently reported to be a minor pathogen of red bell pepper fruit in Trinidad, but has recently been reported as pathogenic to other host species in other countries. The ability of these phytopathogens to produce and secrete cutinase is required for dismantling the cuticle of the host plant and, therefore, crucial to the necrotrophic phase of their infection strategy. In vitro bioassays using different lipid substrates confirmed the ability of C. truncatum and C. brevisporum isolates from green and red bell peppers to secrete cutinase. The diversity, structure and organization and synteny of the cutinase gene were determined among different Colletotrichum species. Cluster analysis indicated a low level of nucleotide variation among C. truncatum sequences. Nucleotide sequences of C. brevisporum were more related to C. truncatum cutinase nucleotide sequences than to C. gloeosporioides. Cluster patterns coincided with haplotype and there was evidence of significant positive selection with no recombination signatures. The structure of the cutinase gene included two exons with one intervening intron and, therefore, one splice variant. Although amino acid sequences were highly conserved among C. truncatum isolates, diversity “hot spots” were revealed when the 66‐amino acid coding region of 200 fungal species was compared. Twenty cutinase orthologues were detected among different fungal species, whose common ancestor is Pezizomycotina and it is purported that these orthologues arose through a single gene duplication event prior to speciation. The cutinase domain was retained both in structure and arrangement among 34 different Colletotrichum species. The order of aligned genomic blocks between species and the arrangement of flanking protein domains were also conserved and shared for those domains immediately located at the N‐ and C‐terminus of the cutinase domain. Among these were an RNA recognition motif, translation elongation factor, signal peptide, pentatricopeptide repeat, and Hsp70 family of chaperone proteins, all of which support the expression of the cutinase gene. The findings of this study are important to understanding the evolution of the cutinase gene in C. truncatum as a key component of the biotrophic–necrotrophic switch which may be useful in developing gene‐targeting strategies to decrease the pathogenic potential of Colletotrichum species. 相似文献
6.
Margaret von Faber Gerda M. van der Weele Geertje van der Geest Jeanet W. Blom Nicolette van der Zouwe Ria Reis Roos C. van der Mast Jacobijn Gussekloo 《Tijdschrift voor gerontologie en geriatrie》2016,47(6):249-257
Background
To gain new insights for support for older people with low mood, we explored the perceptions of ‘screenpositive’ older people on underlying causes and possible solutions.Design and method
We conducted two in-depth interviews with 38 participants (≥77 years) who screened positive for depressive symptoms in general practice. To investigate the influence of the presence of complex health problems, we included 19 persons with and 19 without complex problems. Complex problems were defined as a combination of functional, somatic, psychological or social problems.Results
All participants used several cognitive, social or practical coping strategies. Four patterns emerged: mastery, acceptance, ambivalence, and need for support. Some participants, especially those with complex problems, were ambivalent about possible interventions.Conclusion
Most older participants perceived their coping strategies as sufficient. General practitioners can support self-management by exploring the (effectiveness of) personal coping strategies, providing information, elaborating on perceptions of risks and discussing alternative options with older persons.7.
Wolmarans P Laubscher JA van der Merwe S Kriek JA Lombard CJ Marais M Vorster HH Tichelaar HY Dhansay MA Benadé AJ 《The Journal of nutritional biochemistry》1999,10(10):598-608
In this two-phase crossover study, 39 hypercholesterolemic subjects followed a prudent diet with either lean red meat or fish and skinless chicken (treatment groups), and 13 subjects (reference group) followed their habitual diet. Fasting blood samples were analyzed for plasma total cholesterol, triacylglycerol (TAG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein one- and two-cholesterol, apolipoprotein-B, very low density lipoprotein cholesterol, and very low density lipoprotein TAG, and fatty acid composition of plasma TAG and cholesteryl ester (CE). Body mass and blood pressure were determined. Seven-day dietary records were kept once at baseline and twice during the treatment periods. Significant differences were observed in dietary intake between the baseline and treatment diets and between the two treatment diets. HDL-C (P < 0.05) and diastolic blood pressure (P < 0.01) were higher in patients on the red meat diet than in those on the chicken-fish diet. No other significant differences in lipoproteins were observed between the effects of the two treatment diets. The linoleic acid (%), eicosapentaenoic acid (%), and the eicosapentaenoic acid/arachidonic acid ratios in TAG and CE were higher (P < 0.01) in subjects on the chicken-fish diet than in those on the red meat diet. In conclusion, this study showed that the effect of two lipid-lowering diets containing either lean red meat or skinless chicken and fish on the atherogenic lipoproteins did not differ significantly. A prudent diet with skinless chicken and fish, however, had a more favorable effect on the fatty acid composition of the plasma TAG and the CE than did the lean red meat diet. 相似文献
8.
Rohlena J Kolkman JA Boertjes RC Mertens K Lenting PJ 《The Journal of biological chemistry》2003,278(11):9394-9401
When blood coagulation factor IX is converted to activated factor IX (factor IXa), it develops enzymatic activity and exposes the binding sites for both activated factor VIII and the endocytic receptor low density lipoprotein receptor-related protein (LRP). In the present study we investigated the interaction between factor IXa and LRP in more detail, using an affinity-purified soluble form of LRP (sLRP). Purified sLRP and full-length LRP displayed similar binding to factor IXa. An anti-factor IX monoclonal antibody CLB-FIX 13 inhibited factor IXa.sLRP complex formation. Both the antibody and a soluble recombinant fragment of LRP (i.e. cluster IV) interfered with factor IXa amidolytic activity, suggesting that the antibody and LRP share similar binding regions near the active site of factor IXa. Next, a panel of recombinant factor IXa variants with amino acid replacements in the surface loops bordering the active site was tested for binding to antibody CLB-FIX 13 and sLRP in a solid phase binding assay. Factor IXa variants with mutations in the region Phe(342)-Asn(346), located between the active site of factor IXa and factor VIII binding helix, showed reduced binding to both antibody CLB-FIX 13 and sLRP. Surface plasmon resonance analysis revealed that the variant with Asn(346) replaced by Asp displayed slower association to sLRP, whereas the variant with residues Phe(342)-Tyr(345) replaced by the corresponding residues of thrombin showed faster dissociation. Recombinant soluble LRP fragment cluster IV inhibited factor IXa-mediated activation of factor X with IC(50) values of 5 and 40 nm in the presence and absence of factor VIII, respectively. This inhibition thus seems to occur via two mechanisms: by interference with factor IXa.factor VIIIa complex assembly and by direct inhibition of factor IXa enzymatic activity. Accordingly, we propose that LRP may function as a regulator of blood coagulation. 相似文献
9.
Ria F van den Elzen P Madakamutil LT Miller JE Maverakis E Sercarz EE 《Current molecular medicine》2001,1(3):297-304
T lymphocytes play a central role in the pathogenesis of a large number of human conditions including autoimmunity and graft rejection. Although T cells are key players in mounting immune responses, the assessment of T cell repertoires has yet to find an important role in clinical decision making. In this review, we discuss the "immunoscope" technique and its potential diagnostic role in a variety of clinical scenarios. This is an RT-PCR based approach that subdivides a bulk T cell population (i. e. from blood, lymph, spleen, or tissue) into approximately 2800 groups based upon rearranged variable beta (Vbeta)/joining beta (Jbeta) gene segments and the resulting length of the T cell receptor's (TCR's) third complementarity determining region (CDR-3). This extensive subdivision, or focusing, allows clonal expansions to be directly observed. Such a fine-tuned analysis has revealed previously unappreciated aspects of the T cell repertoire. For instance, an antigen-specific immune response can be divided into both public and non-public components. The non-public repertoire contains the majority of the expanding T cells which are unique to the individual (private), or shared by only some (semi-private), while "public" T cells can be found responding to the antigenic determinant in every individual. Although they are often a minority of the response, the public T cell repertoire seems to play a more important role in defining, as well as driving, the overall immune phenotype in the animal. Immunoscope analysis has identified public and non-public responses in human pathologies, such as multiple sclerosis. The ability to characterize the driver T cells dictating the state of immunity/autoimmunity in individual patients will be an important step towards understanding autoimmunity and designing effective treatment for a variety of conditions including rheumatoid arthritis and multiple sclerosis. We review the current literature involving public and non-public repertoires and discuss the prospect that immunoscope analysis may play a central role in the study and perhaps the management of human autoimmune diseases, and cancer. 相似文献
10.
Heuberger EH Veenhoff LM Duurkens RH Friesen RH Poolman B 《Journal of molecular biology》2002,317(4):591-600
Blue native electrophoresis is used widely for the analysis of non-dissociated protein complexes with respect to composition, oligomeric state and molecular mass. However, the effects of detergent or dye binding on the mass and stability of the integral membrane proteins have not been studied. By comparison with analytical ultracentrifugation, we have evaluated whether the oligomeric state of membrane transport proteins is reflected reliably with blue native electrophoresis. For the analysis we have used two well-characterized transporters, that is, the major facilitator superfamily protein LacS and the phosphotransferase system EII(Mtl). For another member of the major facilitator superfamily, the xyloside transporter XylP from Lactobacillus pentosus, the complete analysis of the quaternary structure determined by analytical ultracentrifugation and freeze-fracture electron microscopy is presented.Our experiments show that during blue native electrophoresis the detergent bound to the proteins is replaced by the amphipathic Coomassie brilliant blue (CBB) dye. The mass of the bound CBB dye was quantified. Provided this additional mass of bound CBB dye is accounted for and care is taken in the choice and concentration of the detergent used, the mass of LacS, XylP and EII(Mtl) and four other membrane (transport) proteins could be deduced within 10 % error. Our data underscore the fact that the oligomeric state of many membrane transport proteins is dimeric. 相似文献