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71.
Lyudmila A Baratova Nataliya V Fedorova Eugenie N Dobrov Elena V Lukashina Andrey N Kharlanov Vitaly V Nasonov Marina V Serebryakova Stanislav V Kozlovsky Olga V Zayakina Nina P Rodionova 《European journal of biochemistry》2004,271(15):3136-3145
The primary structures of N-terminal 19-mer peptides, released by limited trypsin treatment of coat protein (CP) subunits in intact virions of three potato virus X (PVX) isolates, were analyzed. Two wild-type PVX strains, Russian (Ru) and British (UK3), were used and also the ST mutant of UK3 in which all 12 serine and threonine residues in the CP N-terminal segment were replaced by glycine or alanine. With the help of direct carbohydrate analysis and MS, it was found that the acetylated N-terminal peptides of both wild-type strains are glycosylated by a single monosaccharide residue (galactose or fucose) at NAcSer in the first position of the CP sequence, whereas the acetylated N-terminal segment of the ST mutant CP is unglycosylated. Fourier transform infrared spectra in the 1000-4000 cm(-1) region were measured for films of the intact and in situ trypsin-degraded PVX preparations at low and high humidity. These spectra revealed the presence of a broad-band in the region of valent vibrations of OH bonds (3100-3700 cm(-1)), which can be represented by superposition of three bands corresponding to tightly bound, weakly bound, and free OH groups. On calculating difference ('wet' minus 'dry') spectra, it was found that the intact wild-type PVX virions are characterized by high water-absorbing capacity and the ability to order a large number of water molecules on the virus particle. This effect was much weaker for the ST mutant and completely absent in the trypsin-treated PVX. It is proposed that the surface-located and glycosylated N-terminal CP segments of intact PVX virions induce the formation of a columnar-type shell from bound water molecules around the virions, which probably play a major role in maintaining the virion surface structure. 相似文献
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Summary The Vendian-Cambrian interval on the Siberian Platform contains thick carbonate and evaporite sequences formed in extensive
shallow-water basins. The carbonate sequences are characterized by a cyclic composition. Finegrained dolomites, undulated
algal dolomites, flat pebble conglomerates, storm breccias and solution-collapse breccias form the base of each cycle. These
rocks are characterized by an increased clay content which can be high enough to form argillites. Short sedimentation breaks
reflected by mudcracks or silicification horizons are present as well as small cross-bedded tidal channels. Peloidal grainstones
with algal overgrowth dominate in the central parts of the cycles. These members are often recrystallized and dolomitized.
Micritic dolomites, undulous laminated dolomites, storm breccias and columnar stromatolites with abundant mud cracks form
the upper members of the cycles. These sequences are free of clay but contain abundant anhydrite crystals and nodules. In
the uppermost parts of some cycles massive layered anhydrite beds are present. The cycles vary in thickness, but usually they
are between 15 and 20 m thick.
The lower cycle member documents extreme shallow-water deposits. They formed in tidal and partially also supratidal zones
not far from the mainland, from where fine clayey material was washed in. These parts of the sequence reflect a slow transgression.
The central member of a cycle was deposited during the maximal transgression in a shallow basin with normal salinity and rather
active hydrodynamics.
Sedimentation of the upper part of the cycles reflects a regression stage (tidal and especially sabkha environments). The
final layered anhydrite beds formed most probably in relict lakes on the sabkha plain. During sea-level falls some sequences
of the central parts of the cycles were subaerially exposed and underwent partial dolomitization.
The Vendian-Cambrian sabkhas are partly comparable with their recent counterparts. 相似文献
75.
Quantitative understanding of the kinetics of lymphocyte proliferation and death upon activation with an antigen is crucial for elucidating factors determining the magnitude, duration and efficiency of the immune response. Recent advances in quantitative experimental techniques, in particular intracellular labeling and multi-channel flow cytometry, allow one to measure the population structure of proliferating and dying lymphocytes for several generations with high precision. These new experimental techniques require novel quantitative methods of analysis. We review several recent mathematical approaches used to describe and analyze cell proliferation data. Using a rigorous mathematical framework, we show that two commonly used models that are based on the theories of age-structured cell populations and of branching processes, are mathematically identical. We provide several simple analytical solutions for a model in which the distribution of inter-division times follows a gamma distribution and show that this model can fit both simulated and experimental data. We also show that the estimates of some critical kinetic parameters, such as the average inter-division time, obtained by fitting models to data may depend on the assumed distribution of inter-division times, highlighting the challenges in quantitative understanding of cell kinetics. 相似文献
76.
Separation of optical isomers obtainable from trans‐norborn‐5‐ene‐2,3‐dicarboxylic acid methyl and tert‐butyl monoesters was performed by crystallization of the respective salts prepared with (R)‐ and (S)‐1‐phenylethylamine. Starting from racemic endo‐monomethyl ester of trans‐norborn‐5‐ene‐2,3‐dicarboxylic acid, prepared by partial hydrolysis of the cyclopentadiene‐dimethyl fumarate adduct, the corresponding (2R,3R)‐endo‐monoester was isolated in 97% enantiomeric excess (ee) yield after seven repeated crystallizations from tetrachloromethane. Starting from exo‐mono‐tert‐butyl ester of the same acid, prepared by alcoholysis of the cyclopentadiene‐maleic anhydride adduct followed by isomerization, (2R,3R)‐exo‐monoester was isolated in >98% ee yield after four repeated crystallizations from ethanol. Crystallization of the acids from the mother liquor containing (S)‐1‐phenylethylamine yielded products with inverse stereochemical configuration. Chirality 27:151–155, 2015. © 2014 Wiley Periodicals, Inc. 相似文献
77.
Nikolay I. Zhurilo Mikhail V. Chudinov Andrey V. Matveev Olga S. Smirnova Irina D. Konstantinova Anatoly I. Miroshnikov Alexander N. Prutkov Lyubov E. Grebenkina Natalya V. Pulkova Vitaly I. Shvets 《Bioorganic & medicinal chemistry letters》2018,28(1):11-14
The novel isosteric ribavirin analogues were synthesized by two different ways. Some of them showed significant antiviral action against hepatitis C virus (HCV), herpes simplex (HCV-1) and influenza A virus comparable to that of ribavirin itself. The data obtained confirm the proposed theory of the ribavirin possible antiviral activity mechanism related with bioisosterism. 相似文献
78.
Vitaly N. Nikandrov Oleg N. Murashko Galina V. Vorobyova Nelly S. Pyzhova Natalie V. Kvyatkovskaya Oksana A. Bartalevich 《International journal of peptide research and therapeutics》1997,4(4-6):497-502
Summary The formation of stable equimolar complexes of streptokinase or plasminogen with muscle lactate dehydrogenase or pyruvate
kinase, heart mitochondrial malate dehydrogenase and hepatic catalase at pH 7.4, 3.0 and 10.0 was first detected by differential
spectroscopy methods. All complexes, except those of plasminogen with dehydrogenases, were resistant to 6 M urea. Judging
from circular dichroism spectra, tertiary and secondary structures were considerably changed in the complexes. These changes
were significantly dependent upon the nature of interacting proteins; in some cases their structures were more ordered. NAD
(but not NADH) hampered the formation of streptokinase complexes with dehydrogenases. The plasminogen-activating function
of streptokinase and the ability of plasminogen to be activated by streptokinase in the complexes with oxidoreductases were
essentially unchanged. Pyruvate kinase induced a moderate (by 35%) increase in the streptokinase activating function. It is
assumed that the formation of complexes of streptokinase or plasminogen with enzymes may serve as a link in metabolic regulation
and/or intercellular interactions. 相似文献
79.
Raf kinases: function, regulation and role in human cancer 总被引:3,自引:0,他引:3
Leicht DT Balan V Kaplun A Singh-Gupta V Kaplun L Dobson M Tzivion G 《Biochimica et biophysica acta》2007,1773(8):1196-1212
The Ras-Raf-MAPK pathway regulates diverse physiological processes by transmitting signals from membrane based receptors to various nuclear, cytoplasmic and membrane-bound targets, coordinating a large variety of cellular responses. Function of Raf family kinases has been shown to play a role during organism development, cell cycle regulation, cell proliferation and differentiation, cell survival and apoptosis and many other cellular and physiological processes. Aberrations along the Ras-Raf-MAPK pathway play an integral role in various biological processes concerning human health and disease. Overexpression or activation of the pathway components is a common indicator in proliferative diseases such as cancer and contributes to tumor initiation, progression and metastasis. In this review, we focus on the physiological roles of Raf kinases in normal and disease conditions, specifically cancer, and the current thoughts on Raf regulation. 相似文献
80.