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901.
Diolaiti D Bernardoni R Trazzi S Papa A Porro A Bono F Herbert JM Perini G Della Valle G 《Experimental cell research》2007,313(14):2980-2992
902.
903.
Beta-lactamases are the most widespread resistance mechanism to beta-lactam antibiotics, such as the penicillins and cephalosporins. Transition-state analogues that bind to the enzymes with nanomolar affinities have been introduced in an effort to reverse the resistance conferred by these enzymes. To understand the origins of this affinity, and to guide design of future inhibitors, double-mutant thermodynamic cycle experiments were undertaken. An unexpected hydrogen bond between the nonconserved Asn289 and a key inhibitor carboxylate was observed in the X-ray crystal structure of a 1 nM inhibitor (compound 1) in complex with AmpC beta-lactamase. To investigate the energy of this hydrogen bond, the mutant enzyme N289A was made, as was an analogue of 1 that lacked the carboxylate (compound 2). The differential affinity of the four different protein and analogue complexes indicates that the carboxylate-amide hydrogen bond contributes 1.7 kcal/mol to overall binding affinity. Synthesis of an analogue of 1 where the carboxylate was replaced with an aldehyde led to an inhibitor that lost all this hydrogen bond energy, consistent with the importance of the ionic nature of this hydrogen bond. To investigate the structural bases of these energies, X-ray crystal structures of N289A/1 and N289A/2 were determined to 1.49 and 1.39 A, respectively. These structures suggest that no significant rearrangement occurs in the mutant versus the wild-type complexes with both compounds. The mutant enzymes L119A and L293A were made to investigate the interaction between a phenyl ring in 1 and these residues. Whereas deletion of the phenyl itself diminishes affinity by 5-fold, the double-mutant cycles suggest that this energy does not come through interaction with the leucines, despite the close contact in the structure. The energies of these interactions provide key information for the design of improved inhibitors against beta-lactamases. The high magnitude of the ion-dipole interaction between Asn289 and the carboxylate of 1 is consistent with the idea that ionic interactions can provide significant net affinity in inhibitor complexes. 相似文献
904.
Dardonville C Rinaldi E Hanau S Barrett MP Brun R Gilbert IH 《Bioorganic & medicinal chemistry》2003,11(14):3205-3214
The synthesis and biological evaluation of three series of 6-phosphogluconate (6PG) analogues is described. (2R)-2-Methyl-4,5-dideoxy, (2R)-2-methyl-4-deoxy and 2,4-dideoxy analogues of 6PG were tested as inhibitors of 6-phosphogluconate dehydrogenase (6PGDH) from sheep liver and also Trypanosoma brucei where the enzyme is a validated drug target. Among the three series of analogues, seven compounds were found to competitively inhibit 6PGDH from T. brucei and sheep liver enzymes at micromolar concentrations. Six inhibitors belong to the (2R)-2-methyl-4-deoxy series (6, 8, 10, 12, 21, 24) and one is a (2R)-2-methyl-4,5-dideoxy analogue (29b). The 2,4-dideoxy analogues of 6PG did not inhibit both enzymes. The trypanocidal effect of the compounds was also evaluated in vitro against T. brucei rhodesiense as well as other related trypanosomatid parasites (i.e., Trypanosoma cruzi and Leishmania donovani). 相似文献
905.
Gagliardi MC Starnino S Teloni R Mariotti S Dal Conte I Di Carlo A Stefanelli P 《FEMS immunology and medical microbiology》2011,61(1):129-132
Neisseria gonorrhoeae is the etiological agent of gonorrhoea, an infectious disease characterized by acute inflammation of the urogenital tract with a massive infiltration of neutrophils. Polymorphonuclear leukocyte recruitment is one of the activities of the recently described interleukin-17A (IL-17A); thus, we analyzed the serum concentration of IL-17A, together with IL-23 and interferon-γ (IFN-γ), in 27 patients with gonorrhoea. The concentration of these cytokines in patients' sera was significantly higher than that detected in healthy controls and an inverse correlation was found between the concentrations of IL-17A and IFN-γ. This is the first report showing a significant increase of IL-17A and IL-23 serum levels in patients with gonorrhoea, suggesting new players in the immune response to N. gonorrhoeae. 相似文献
906.
Simone Guglielmetti Ivan Zanoni Silvia Balzaretti Matteo Miriani Valentina Taverniti Ivano De Noni Ilaria Presti Milda Stuknyte Alessio Scarafoni Stefania Arioli Stefania Iametti Francesco Bonomi Diego Mora Matti Karp Francesca Granucci 《Applied and environmental microbiology》2014,80(17):5170-5177
Bifidobacteria are Gram-positive inhabitants of the human gastrointestinal tract that have evolved close interaction with their host and especially with the host''s immune system. The molecular mechanisms underlying such interactions, however, are largely unidentified. In this study, we investigated the immunomodulatory potential of Bifidobacterium bifidum MIMBb75, a bacterium of human intestinal origin commercially used as a probiotic. Particularly, we focused our attention on TgaA, a protein expressed on the outer surface of MIMBb75''s cells and homologous to other known bacterial immunoactive proteins. TgaA is a peptidoglycan lytic enzyme containing two active domains: lytic murein transglycosylase (LT) and cysteine- and histidine-dependent amidohydrolase/peptidase (CHAP). We ran immunological experiments stimulating dendritic cells (DCs) with the B. bifidum MIMBb75 and TgaA, with the result that both the bacterium and the protein activated DCs and triggered interleukin-2 (IL-2) production. In addition, we observed that the heterologous expression of TgaA in Bifidobacterium longum transferred to the bacterium the ability to induce IL-2. Subsequently, immunological experiments performed using two purified recombinant proteins corresponding to the single domains LT and CHAP demonstrated that the CHAP domain is the immune-reactive region of TgaA. Finally, we also showed that TgaA-dependent activation of DCs requires the protein CD14, marginally involves TRIF, and is independent of Toll-like receptor 4 (TLR4) and MyD88. In conclusion, our study suggests that the bacterial CHAP domain is a novel microbe-associated molecular pattern actively participating in the cross talk mechanisms between bifidobacteria and the host''s immune system. 相似文献
907.
Alma Balestrazzi Silvia Botti Samantha Zelasco Stefania Biondi Cinzia Franchin Paolo Calligari Milvia Racchi Adelaide Turchi Guido Lingua Graziella Berta Daniela Carbonera 《Plant cell reports》2009,28(8):1179-1192
Marker-free transgenic white poplar (Populus alba L., cv ‘Villafranca’) plants, expressing the PsMT
A1
gene from Pisum sativum for a metallothionein-like protein, were produced by Agrobacterium tumefaciens-mediated transformation. The 35SCaMV-PsMT
A1
-NosT cassette was inserted into the ipt-type vector pMAT22. The occurrence of the abnormal ipt-shooty phenotype allowed the visual selection of transformants, while the yeast site-specific recombination R/RS system was
responsible for the excision of the undesired vector sequences with the consequent recovery of normal marker-free transgenic
plants. Molecular analyses confirmed the presence of the 35SCaMV-PsMT
A1
-NosT cassette and transgene expression. Five selected lines were further characterized, revealing the ability to withstand
heavy metal toxicity. They survived 0.1 mM CuCl2, a concentration which strongly affected the nontransgenic plants. Moreover, root development was only slightly affected
by the ectopic expression of the transgene. Reactive oxygen species were accumulated to a lower extent in leaf tissues of
multi-auto-transformation (MAT)-PsMTA1 plants exposed to copper and zinc, compared to control plants. Tolerance to photo-oxidative stress induced by paraquat was
another distinctive feature of the MAT-PsMTA1 lines. Finally, low levels of DNA damage were detected by quantifying the amounts of 8-hydroxy-2′-deoxyguanosine in leaf
tissues of the transgenic plants exposed to copper. 相似文献
908.
Inhibition of Helicobacter pylori Infection in Humans by Lactobacillus reuteri ATCC 55730 and Effect on Eradication Therapy: A Pilot Study 总被引:3,自引:0,他引:3
Ruggiero Francavilla Elena Lionetti Stefania Paola Castellaneta Anna Maria Magistà Giovanni Maurogiovanni Nunzia Bucci Angela De Canio Flavia Indrio Luciano Cavallo Enzo Ierardi Vito Leonardo Miniello 《Helicobacter》2008,13(2):127-134
Background: Several studies report an inhibitory effect of probiotics on Helicobacter pylori .
Aim: To test whether Lactobacillus reuteri ATCC 55730 reduces H. pylori intragastric load in vivo, decreases dyspeptic symptoms, and affects eradication rates after conventional treatment.
Materials and Methods: In a double-blind placebo-controlled study, 40 H. pylori -positive subjects were given L. reuteri once a day for 4 weeks or placebo. All underwent upper endoscopy,13 C-urea breath test, and H. pylori stool antigen determination at entry and 13 C-urea breath test and H. pylori stool antigen (used as both qualitative and semiquantitative markers) after 4 weeks of treatment. Sequential treatment was administered subsequently to all.
Results: In vivo, L. reuteri reduces H. pylori load as semiquantitatively assessed by both13 C-urea breath test δ -value and H. pylori stool antigen quantification after 4 weeks of treatment ( p < .05). No change was shown in patients receiving placebo. L. reuteri administration was followed by a significant decrease in the Gastrointestinal Symptom Rating Scale as compared to pretreatment value ( p < .05) that was not present in those receiving placebo ( p = not significant). No difference in eradication rates was observed.
Conclusions: L. reuteri effectively suppresses H. pylori infection in humans and decreases the occurrence of dyspeptic symptoms. Nevertheless, it does not seem to affect antibiotic therapy outcome. 相似文献
Aim: To test whether Lactobacillus reuteri ATCC 55730 reduces H. pylori intragastric load in vivo, decreases dyspeptic symptoms, and affects eradication rates after conventional treatment.
Materials and Methods: In a double-blind placebo-controlled study, 40 H. pylori -positive subjects were given L. reuteri once a day for 4 weeks or placebo. All underwent upper endoscopy,
Results: In vivo, L. reuteri reduces H. pylori load as semiquantitatively assessed by both
Conclusions: L. reuteri effectively suppresses H. pylori infection in humans and decreases the occurrence of dyspeptic symptoms. Nevertheless, it does not seem to affect antibiotic therapy outcome. 相似文献
909.
910.
Tryptophan-based radical in the catalytic mechanism of versatile peroxidase from Bjerkandera adusta 总被引:1,自引:0,他引:1
Pogni R Baratto MC Giansanti S Teutloff C Verdin J Valderrama B Lendzian F Lubitz W Vazquez-Duhalt R Basosi R 《Biochemistry》2005,44(11):4267-4274
Versatile peroxidase (VP) from Bjerkandera adusta is a structural hybrid between lignin (LiP) and manganese (MnP) peroxidase. This hybrid combines the catalytic properties of the two above peroxidases, being able to oxidize typical LiP and MnP substrates. The catalytic mechanism is that of classical peroxidases, where the substrate oxidation is carried out by a two-electron multistep reaction at the expense of hydrogen peroxide. Elucidation of the structures of intermediates in this process is crucial for understanding the mechanism of substrate oxidation. In this work, the reaction of H(2)O(2) with the enzyme in the absence of substrate has been investigated with electron paramagnetic resonance (EPR) spectroscopy. The results reveal an EPR signal with partially resolved hyperfine structure typical of an organic radical. The yield of this radical is approximately 30%. Progressive microwave power saturation measurements indicate that the radical is weakly coupled to a paramagnetic metal ion, suggesting an amino acid radical in moderate distance from the ferryl heme. A tryptophan radical was identified as a protein-based radical formed during the catalytic mechanism of VP from Bjerkandera adusta through X-band and high-field EPR measurements at 94 GHz, aided by computer simulations for both frequency bands. A close analysis of the theoretical model of the VP from Bjerkandera sp. shows the presence of a tryptophan residue near to the heme prosthetic group, which is solvent-exposed as in the case of LiP and other VPs. The catalytic role of this residue in a long-range electron-transfer pathway is discussed. 相似文献