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排序方式: 共有406条查询结果,搜索用时 343 毫秒
71.
Joseph M. Hayes Anastassia L. Kantsadi Demetres D. Leonidas 《Phytochemistry Reviews》2014,13(2):471-498
Glycogen phosphorylase (GP) (EC 2.4.1.1) is an important therapeutic target for the potential treatment of type 2 diabetes. The search for potent, selective and drug-like GP inhibitors which may eventually lead to hypoglycaemic agents has to date uncovered a number of natural product inhibitors with both pharmaceutical and nutraceutical potential. GP is an allosteric protein with at least six different ligand binding sites that modulate its enzymatic activity. Hence, inhibitors with considerable structural diversity can be designed. This review is focused on advances in the discovery of natural products and their derivatives as GP inhibitors. 相似文献
72.
M. A. Zenkova N. L. Chumakova A. V. Vlassov N. I. Komarova A. G. Venyaminova V. V. Vlassov V. N. Silnikov 《Molecular Biology》2000,34(3):390-394
The mechanism of hydrolysis of RNA substrates—diribonucleoside monophosphate CpA and decaribonucleotide UUCAUGUAAA—by chemical
constructs functionally mimicking ribonuclease A was studied. It is shown that RNA cleavage by chemical RNases 2L2 and 2D3
proceeds similar to the RNase A-induced RNA hydrolysis through 2′,3′-cyclophosphate as an intermediate product. A comparison
of hydrolyses of CpA in water and D2O revealed an isotope effect (K
H/K
D=2.28), which implies acid-base catalysis at the limiting stage of the reaction. Two feasible mechanisms of RNA hydrolysis
by chemical RNases (linear and adjacent) are discussed. 相似文献
73.
Investigations showed that Rhodococcus erythropolis E-15 and Arthrobacter globiformis 2F cells respond to osmotic shock by increasing the synthesis of free amino acids, primarily glutamic acid (80% of the intracellular free amino acid pool). The osmoprotective role of glutamic acid follows from its beneficial effect on the growth of bacteria in high-salinity media. It was found that the addition of this amino acid to the growth medium at a concentration of 2 mM shortened the lag phase and increased the growth rate and biomass yield of either of the two bacteria. The addition of another osmoprotectant, trehalose, to the high-salinity growth medium of R. erythropolis E-15 at the same concentration (2 mM), restored the growth parameters of this bacterium to the control values. 相似文献
74.
75.
Anastassia Kanavarioti T. Brian Hurley Eldon E. Baird 《Journal of molecular evolution》1995,41(2):161-168
Evidence is presented for complexation of guanosine 5-monophosphate 2-methylimidazolide (2-MeImpG) with polycytidylate (poly(C)) at pH 8.0 and 23°C in the presence of 1.0 M NaCl and 0.2 M MgCl2 in water. The association of 2-McImpG with poly(C) was investigated using UV-vis spectroscopy as well as by monitoring the kinetics of the nucleophilic substitution reaction of the imidazole moiety by amines. The results of both methods are consistent with moderately strong poly(C) · 2-McImpG complexation and the spectrophotometric measurements allowed the construction of a binding isotherm with a concentration of 2-McImpG equal to 5.55 ± 0.15 mM at half occupancy. UV spectroscopy was employed to establish the binding of other guanosine derivatives on poly(C). These derivatives are guanosine 5-monophosphate (5GMP), guanosine 5monophosphate imidazolide (ImpG), and guanosine 5monophosphate morpholidate (morpG). Within experimental error these guanosine derivatives exhibit the same affinity for poly(C) as 2-McImpG. 相似文献
76.
Phosphoimidazolide activated ribomononucleotides (*pN) are useful substrates for the non-enzymatic synthesis of polynucleotides. However, dilute neutral aqueous solutions of *pN typically yield small amounts of dimers and traces of polymers; most of *pN hydrolyzes to yield nucleoside 5-monophosphate. Here we report the self-condensation of nucleoside 5-phosphate 2-methylimidazolide (2-MeImpN with N = cytidine, uridine or guanosine) in the presence of Mg2+ in concentrated solutions, such as might have been found in an evaporating lagoon on prebiotic Earth. The product distribution indicates that oligomerization is favored at the expense of hydrolysis. At 1.0 M, 2-MeImpU and 2-MeImpC produce about 65% of oligomers including 4% of the 3,5-linked dimer. Examination of the product distribution of the three isomeric dimers in a self-condensation allows identification of reaction pathways that lead to dimer formation. Condensations in a concentrated mixture of all three nucleotides (U,C,G mixtures) is made possible by the enhanced solubility of 2-MeImpG in such mixtures. Although percent yield of internucleotide linked dimers is enhanced as a function of initial monomer concentration, pyrophosphate dimer yields remain practically unchanged at about 20% for 2-MeImpU, 16% for 2-MeImpC and 25% of the total pyrophosphate in the U,C,G mixtures. The efficiency by which oligomers are produced in these concentrated solutions makes the evaporating lagoon scenario a potentially interesting medium for the prebiotic synthesis of dimers and short RNAs. 相似文献
77.
L. A. Komarova 《Entomological Review》2016,96(2):255-262
The taxonomy of the genus Leptosciarella Tuomikoski, 1960 in the Altai Area within Altai Territory and the Altai Republic was studied. Eleven species were recognized, including three new species which are described and illustrated here: Leptosciarella (L.) ulagana Komarova sp. n., L. (L.) angustistylus Komarova sp. n., L. (L.) senex Komarova sp. n. Additionally, L. (L.) fuscipalpa (Mohrig et Mamaev 1979) and L. (L.) truncata (Tuomikoski 1960) are recorded from Altai for the first time. A key to the Altai species is provided. 相似文献
78.
Osteoclasts are responsible for physiological bone remodeling as well as pathological bone destruction in osteoporosis, periodontitis and rheumatoid arthritis, and thus represent a pharmacological target for drug development. We aimed to characterize and compare the cytokine-induced osteoclastogenesis of bone marrow and spleen precursors. Established protocols used to generate osteoclasts from bone marrow were modified to examine osteoclastogenesis of the spleen cells of healthy mice. Osteoclast formation was successfully induced from spleen precursors using receptor activator of nuclear factor κB ligand (50 ng/ml) and macrophage colony stimulating factor (50 ng/ml). Compared to bone marrow cultures, differentiation from spleen required a longer cultivation time (9 days for spleen, as compared to 5 days for marrow cultures) and a higher plating density of non-adherent cells (75,000/cm2 for spleen, as compared to 50,000/cm2 for bone marrow). Osteoclasts generated from spleen precursors expressed osteoclast marker genes calcitonin receptor, cathepsin K and matrix metalloproteinase 9 and were capable of resorbing hydroxyapatite. The differentiation capacity of spleen and bone marrow precursors was comparable for BALB/c, C57BL/6 and FVB mice. We also developed and tested a cryopreservation protocol for the osteoclast precursors. While 70–80 % of cells were lost during the first week of freezing, during the subsequent 5 weeks the losses were within 2–5 % per week. Osteoclastogenesis from the recovered bone marrow precursors was successful up to 5 weeks after freezing. Spleen precursors retained their osteoclastogenic capacity for 1 week after freezing, but not thereafter. The described protocol is useful for the studies of genetically modified animals as well as for screening new osteoclast-targeting therapeutics. 相似文献
79.
M P Filatova N A Krit O M Komarova V N Orekhovich S Reissmann 《Bioorganicheskaia khimiia》1986,12(1):59-70
To investigate conformations of peptide inhibitors of the angiotensin-converting enzyme in the enzyme-inhibitor complex, the synthesis, studies of inhibitory activity, and conformational calculations of analogues of bradykinin-potentiating peptides with N-methylalanine or D-alanine in place of L-proline or L-alanine residues have been carried out. All the analogues showed a sharp decrease of inhibitory activity in comparison with the natural peptides, that might be considered as an indirect confirmation of the earlier proposed "conformation of inhibition" of the above-mentioned peptides. 相似文献
80.
Lipophilic biopolymers from the cell walls of saprophytic mycobacteria were shown to stimulate the process of hydrocarbon assimilation by Pseudomonas aeruginosa cells. This should be attributed to the fact that bacterial peptidoglycolipids emulsify a hydrocarbon facilitating the contact between it and the cells. It has been found experimentally that P. aeruginosa cells growing in the medium with n-alkanes release a factor into the medium. The factor appears to contain peptide chains and is responsible for hydrocarbon emulsification. 相似文献