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51.
Dmitri E. Andreev Sergey E. Dmitriev Ilya M. Terenin Vladimir S. Prassolov William C. Merrick Ivan N. Shatsky 《Nucleic acids research》2009,37(18):6135-6147
Many mammalian mRNAs possess long 5′ UTRs with numerous stem-loop structures. For some of them, the presence of Internal Ribosome Entry Sites (IRESes) was suggested to explain their significant activity, especially when cap-dependent translation is compromised. To test this hypothesis, we have compared the translation initiation efficiencies of some cellular 5′ UTRs reported to have IRES-activity with those lacking IRES-elements in RNA-transfected cells and cell-free systems. Unlike viral IRESes, the tested 5′ UTRs with so-called ‘cellular IRESes’ demonstrate only background activities when placed in the intercistronic position of dicistronic RNAs. In contrast, they are very active in the monocistronic context and the cap is indispensable for their activities. Surprisingly, in cultured cells or cytoplasmic extracts both the level of stimulation with the cap and the overall translation activity do not correlate with the cumulative energy of the secondary structure of the tested 5′ UTRs. The cap positive effect is still observed under profound inhibition of translation with eIF4E-BP1 but its magnitude varies for individual 5′ UTRs irrespective of the cumulative energy of their secondary structures. Thus, it is not mandatory to invoke the IRES hypothesis, at least for some mRNAs, to explain their preferential translation when eIF4E is partially inactivated. 相似文献
52.
Stefanie Müller Anatoly A. Bobrov Lutz Schirrmeister Andrei A. Andreev Pavel E. Tarasov 《Palaeogeography, Palaeoclimatology, Palaeoecology》2009,271(3-4):301-315
Our study aims to look for testate amobae (TA) in the surface and fossil sediments from the Cape Mamontov Klyk (73°60′–73°63′ N, 116°88′–117°18′ E), southern coast of the Laptev Sea, ca 150 km west of the Lena Delta and to discuss the potential of TA analysis for Glacial/Interglacial environmental reconstructions in Arctic Siberia. The radiocarbon age determination suggests that the studied sediments accumulated between ca 45,000 14C yr BP and present. A total of 98 TA taxa were identified in the 10 recent surface and 59 fossil samples. Results of taxonomical identification and ecological analysis of TA in the modern and fossil samples suggest that major changes in the soil moisture conditions took place. Our results show that soil-living taxa dominated the TA assemblages at the study sites during the past 45,000 years. The environmental conditions of the study area were most favourable (relatively warm and humid) during the Kargin Interstadial (ca 45,000–25,000 14C yr BP). An opposite situation is reconstructed for the Sartan Stadial (ca. 25,000–15,000 14C yr BP). During the Kargin Interstadial, optimum conditions occurred between ca 44,000 and 40,000 14C yr BP characterised by highest TA abundances and taxa diversity. This initial optimal phase was followed by the interval with drier and colder conditions about 40,000–30,000 14C yr BP. The sediments dated between ca. 24,000 and 18,000 14C yr BP show low TA abundances and diversity, in agreement with the much colder and drier environments during the maximum phase of the Last Glacial. The onset of the Holocene is indicated by a broad representation of obligate hydrophilic taxa, especially from genus Difflugia, suggesting wet and relatively warm conditions. By comparison with other environmental proxies used in the studied sections as well as from the neighbouring arctic regions our results suggest that TA analysis can provide valuable information, contributing to the better understanding of the Late Quaternary climate and environments in Arctic Siberia. 相似文献
53.
S. A. Kozlov Ya A. Andreev A. N. Murashev D. I. Skobtsov I. A. D’yachenko E. V. Grishin 《Russian Journal of Bioorganic Chemistry》2009,35(6):711-719
Two new polypeptide components which exhibited an analgesic effect in experiments on mice were isolated from the Heteractis crispa sea tropical anemone by the combination of chromatographic methods. The APHC2 and APHC3 new polypeptides consisted of 56
amino acid residues and contained six cysteine residues. Their complete amino acid sequence was determined by the methods
of Edman sequencing, mass spectrometry, and peptide mapping. An analysis of the primary structure of the new peptides allowed
for their attribution to a large group of trypsin inhibitors of the Kunitz type.
An interesting biological function of the new polypeptides was their analgesic effect on mammals, which is possibly realized
via the modulation of the activity of the TRPV1 receptor and was not associated with the residual inhibiting activity towards
trypsin and chymotrypsin. The analgesic activity of the APHC3 polypeptide was measured on the hot plate model of acute pain
and was significantly higher than that of APHC2. Methods of preparation of the recombinant analogues were created for both
polypeptides. 相似文献
54.
ANDRÉIA SILVA FLORES RÉA M. CORRÊA ELIANA R. FORNI-MARTINS ANA M. G. AZEVEDO TOZZI 《Botanical journal of the Linnean Society. Linnean Society of London》2006,151(2):271-277
Chromosome numbers were counted for 23 species of Crotalaria native to Brazil. Among these data there were new counts for 15 taxa, and some confirmed previous reports or represented numbers that were different from those cited previously. The chromosome numbers most frequently found were 2 n = 16 and 2 n = 32. Only C. incana L. had 2 n = 14 and C. tweediana Benth. had 2 n = 54. The counts 2 n = 32 and 54 were found in species of section Calycinae and 2 n = 16 and 14 in species of section Chrysocalycinae . The data revealed the importance of chromosomal parameters in the characterization of sections Calycinae and Chrysocalycinae in Brazil. We discuss the systematic significance and evolutionary aspects for the genus, comparing the results with the two sections that are native in Brazil. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 271–277. 相似文献
55.
Drug molecules are typically hydrophobic and small in order to traverse membranes to reach cytoplasmic targets, but we have discovered that more polar molecules can be delivered across membranes using water-soluble, moderately hydrophobic membrane peptides of the pHLIP (pH low insertion peptide) family. Delivery of polar cargo molecules could expand the chemical landscape for pharmacological agents that have useful activity but are too polar by normal drug criteria. The spontaneous insertion and folding of the pHLIP peptide across a lipid bilayer seeks a free energy minimum, and insertion is accompanied by a release of energy that can be used to translocate cell-impermeable cargo molecules. In this study, we report our first attempt to tune the hydrophobicity of a polar cargo, phallacidin, in a systematic manner. We present the design, synthesis, and characterization of three phallacidin cargoes, where the hydrophobicity of the cargo was tuned by the attachment of diamines of various lengths of hydrophobic chains. The phallacidin cargoes were conjugated to pHLIP and shown to selectively inhibit the proliferation of cancer cells in a concentration-dependent manner at low pH. 相似文献
56.
Lutz Schirrmeister Guido Grosse Moritz Schnelle Margret Fuchs Matthias Krbetschek Mathias Ulrich Viktor Kunitsky Mikhail Grigoriev Andrei Andreev Frank Kienast Hanno Meyer Olga Babiy Irina Klimova Anatoly Bobrov Sebastian Wetterich Georg Schwamborn 《Palaeogeography, Palaeoclimatology, Palaeoecology》2011,299(1-2):175-196
The three main Lena Delta terraces were formed during different stages of the late Quaternary. While only the first floodplain terrace is connected with active deltaic processes, the second and third terraces, which dominate the western part of the delta, are erosional remnants of arctic paleolandscapes affected by periglacial processes. The landscape dynamics of the second and the third terraces, and their relationship to each other, are of particular importance in any effort to elucidate the late Quaternary paleoenvironment of western Beringia.Multidisciplinary studies of permafrost deposits on the second terrace were carried out at several sites of the Arga Complex, named after the largest delta island, Arga–Muora–Sise. The frozen sediments predominantly consist of fluvial sands several tens of meters thick, radiocarbon-dated from > 52 to 16 kyr BP. These sands were deposited under changing fluvial conditions in a dynamic system of shifting river channels, and have been additionally modified by synsedimentary and postsedimentary cryogenesis. Later thermokarst processes affected this late Pleistocene fluvial landscape during the Lateglacial and the Holocene. In addition, eolian activity reworked the fluvial sands on exposed surfaces at least since the Lateglacial, resulting in dune formation in some areas. Contrary to the Arga Complex, the third terrace is mainly composed of polygenetic alluvial and proluvial ice-rich permafrost sequences (Ice Complex deposits) radiocarbon-dated from 50 to 17 kyr BP which cover older fluvial sand units luminescence-dated to about 100–50 kyr BP. Paleoecological records reflect tundra-steppe conditions that varied locally, depending on landscape dynamics, during the Marine Isotope Stage (MIS) 4 and 3 periods, and a persistent change to shrub and arctic tundra during Lateglacial and Holocene periods.The study results indicate a continuous fluvial sedimentation environment for the Laptev Sea shelf in the region of the second Lena Delta terrace during the late Pleistocene, and confirm the presence of a dynamic channel system of the paleo-Lena River that flowed at the same time as the nearby subaerial Ice Complex deposits were being formed. 相似文献
57.
Ricci GC De Souza-Kaneshima AM Felismino MF Mendes-Bonato AB Pagliarini MS Do Valle CB 《Journal of genetics》2011,90(2):289-294
A total of 44 accessions of Brachiaria decumbens were analysed for chromosome count and meiotic behaviour in order to identify potential progenitors for crosses. Among them,
15 accessions presented 2n = 18; 27 accessions, 2n = 36; and 2 accessions, 2n = 45 chromosomes. Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In
the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities
were related to irregular chromosome segregation, but chromosome stickiness and abnormal cytokinesis were observed in low
frequency. All abnormalities can compromise pollen viability by generating unbalanced gametes. Based on the chromosome number
and meiotic stability, the present study indicates the apomictic tetraploid accessions that can act as male genitor to produce
interspecific hybrids with B. ruziziensis or intraspecific hybrids with recently artificially tetraploidized accessions. 相似文献
58.
Barrera FN Weerakkody D Anderson M Andreev OA Reshetnyak YK Engelman DM 《Journal of molecular biology》2011,413(2):359-10222
We have used pHLIP® [pH (low) insertion peptide] to study the roles of carboxyl groups in transmembrane (TM) peptide insertion. pHLIP binds to the surface of a lipid bilayer as a disordered peptide at neutral pH; when the pH is lowered, it inserts across the membrane to form a TM helix. Peptide insertion is reversed when the pH is raised above the characteristic pKa (6.0). A key event that facilitates membrane insertion is the protonation of aspartic acid (Asp) and/or glutamic acid (Glu) residues, since their negatively charged side chains hinder membrane insertion at neutral pH. In order to gain mechanistic understanding, we studied the membrane insertion and exit of a series of pHLIP variants where the four Asp residues were sequentially mutated to nonacidic residues, including histidine (His). Our results show that the presence of His residues does not prevent the pH-dependent peptide membrane insertion at ∼ pH 4 driven by the protonation of carboxyl groups at the inserting end of the peptide. A further pH drop leads to the protonation of His residues in the TM part of the peptide, which induces peptide exit from the bilayer. We also find that the number of ionizable residues that undergo a change in protonation during membrane insertion correlates with the pH-dependent insertion into the lipid bilayer and exit from the lipid bilayer, and that cooperativity increases with their number. We expect that our understanding will be used to improve the targeting of acidic diseased tissue by pHLIP. 相似文献
59.