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Miguel López-Estepa Ana Ardá Martin Savko Adam Round William E. Shepard Marta Bruix Miquel Coll Francisco J. Fernández Jesús Jiménez-Barbero M. Cristina Vega 《PloS one》2015,10(4)
Cyclic N6-threonylcarbamoyladenosine (‘cyclic t6A’, ct6A) is a non-thiolated hypermodification found in transfer RNAs (tRNAs) in bacteria, protists, fungi and plants. In bacteria and yeast cells ct6A has been shown to enhance translation fidelity and efficiency of ANN codons by improving the faithful discrimination of aminoacylated tRNAs by the ribosome. To further the understanding of ct6A biology we have determined the high-resolution crystal structures of CsdL/TcdA in complex with AMP and ATP, an E1-like activating enzyme from Escherichia coli, which catalyzes the ATP-dependent dehydration of t6A to form ct6A. CsdL/TcdA is a dimer whose structural integrity and dimer interface depend critically on strongly bound K+ and Na+ cations. By using biochemical assays and small-angle X-ray scattering we show that CsdL/TcdA can associate with tRNA with a 1:1 stoichiometry and with the proper position and orientation for the cyclization of t6A. Furthermore, we show by nuclear magnetic resonance that CsdL/TcdA engages in transient interactions with CsdA and CsdE, which, in the latter case, involve catalytically important residues. These short-lived interactions may underpin the precise channeling of sulfur atoms from cysteine to CsdL/TcdA as previously characterized. In summary, the combination of structural, biophysical and biochemical methods applied to CsdL/TcdA has afforded a more thorough understanding of how the structure of this E1-like enzyme has been fine tuned to accomplish ct6A synthesis on tRNAs while providing support for the notion that CsdA and CsdE are able to functionally interact with CsdL/TcdA. 相似文献
33.
C. A. Arce Marta E. Hallak J. A. Rodriguez H. S. Barra R. Caputio 《Journal of neurochemistry》1978,31(1):205-210
Abstract— Incorporation of [14 C]tyrosine into the C-terminal position of α-tubulin of rat brain cytosol was 10-fold higher for non-assembled than for assembled tubulin. The incorporation into tubulin from disassembled microtubules was higher than into non-assembled tubulin; therefore, the low incorporation into microtubules was not due to a lower acceptor capacity of their tubulin constituent.
[14 C]Tyrosine was released from assembled and non-assembled [14 C]tyrosinated tubulin by the action of an endogenous carboxypeptidase. Release from non-assembled tubulin was shown by incubating a tubulinyl-[14 C]tyrosine preparation in the presence of CaCl2 at a concentration that abolished microtubule formation. Release from microtubules was inferred from the observation that the percentages of [14 C]tyrosine released and the decrease of the specific radioactivity of the recovered microtubules were practically identical and did not change after a 10-fold dilution of the incubated microtubules.
[3 H]Phenylalanine was released from a preparation of tubulinyl-[3 H]phenylalanine also by an enzymatic activity.
The capacity of a tubulin preparation to incorporate tyrosine was increased 43% by pre-treatment with endogenous carboxypeptidase.
Tubulin tyrosinated in vitro was assembled to the same extent as native tubulin. After a mixture of tubulinyl-[14 C]tyrosine and tubulinyl-[3 H]phenylalanine was partially assembled, the ratio of 14 C/3 H found in the microtubules was the same as in the non-assembled tubulin fraction. 相似文献
[
[
The capacity of a tubulin preparation to incorporate tyrosine was increased 43% by pre-treatment with endogenous carboxypeptidase.
Tubulin tyrosinated in vitro was assembled to the same extent as native tubulin. After a mixture of tubulinyl-[
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We studied the aggregation state of Photosystem II in stacked and unstacked thylakoid membranes from spinach after a quick
and mild solubilization with the non-ionic detergent n-dodecyl-α,D-maltoside, followed by analysis by diode-array-assisted gel filtration chromatography and electron microscopy.
The results suggest that Photosystem II (PS II) isolates either as a paired, appressed membrane fragment or as a dimeric PS
II-LHC II supercomplex upon mild solubilization of stacked thylakoid membranes or PS II grana membranes, but predominantly
as a core monomer upon mild solubilization of unstacked thylakoid membranes. Analysis of paired grana membrane fragments reveals
that the number of PS II dimers is strongly reduced in single membranes at the margins of the grana membrane fragments. We
suggest that unstacking of thylakoid membranes results in a spontaneous disintegration of the PS II-LHC II supercomplexes
into separated PS II core monomers and peripheral light-harvesting complexes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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de Melo AC d'Avila-Levy CM Branquinha MH Vermelho AB 《Experimental parasitology》2002,102(3-4):150-156
The extracellular metalloproteinases of the insect trypanosomatid Crithidia guilhermei were characterized through the incorporation of different protein substrates (gelatin, casein, haemoglobin, and bovine serum albumin) into SDS-PAGE. Two gelatinases (60 and 80 kDa) showed ability to degrade casein as well and a 67-kDa enzyme presented the broadest specificity since it was also able to degrade casein and haemoglobin. Besides the 67-kDa extracellular proteinases detected on haemoglobin-SDS-PAGE, a 43-kDa haemoglobinase was only observed with this substrate. All C. guilhermei proteinases were incapable of using bovine serum albumin. C. guilhermei was also grown in four different culture media and the best proteinase production was reached using yeast extract-peptone medium containing glucose as the major carbon source. The results point to the importance of the use of distinct culture media and proteinaceous substrates on the characterization of extracellular proteolytic activities in trypanosomatids, since alterations in growth conditions and methods of detection could lead to distinct proteolytic profiles. 相似文献
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