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141.
Se?Bok?Jang Mi?Suk?Jeong Lance?C.?Seefeldt John?W.?PetersEmail author 《Journal of biological inorganic chemistry》2004,9(8):1028-1033
The structures of nitrogenase Fe proteins with defined amino acid substitutions in the previously implicated nucleotide-dependent signal transduction pathways termed switch I and switch II have been determined by X-ray diffraction methods. In the Fe protein of nitrogenase the nucleotide-dependent switch regions are responsible for communication between the sites responsible for nucleotide binding and hydrolysis and the [4Fe-4S] cluster of the Fe protein and the docking interface that interacts with the MoFe protein upon macromolecular complex formation. In this study the structural characterization of the Azotobacter vinelandii nitrogenase Fe protein with Asp at position 39 substituted by Asn in MgADP-bound and nucleotide-free states provides an explanation for the experimental observation that the altered Fe proteins form a trapped complex subsequent to a single electron transfer event. The structures reveal that the substitution allows the formation of a hydrogen bond between the switch I Asn39 and the switch II Asp125. In the structure of the native enzyme the analogous interaction between the side chains of Asp39 and Asp125 is precluded due to electrostatic repulsion. These results suggest that the electrostatic repulsion between Asp39 and Asp125 is important for dissociation of the Fe protein:MoFe protein complex during catalysis. In a separate study, the structural characterization of the Fe protein with Asp129 substituted by Glu provides the structural basis for the observation that the Glu129-substituted variant in the absence of bound nucleotides has biochemical properties in common with the native Fe protein with bound MgADP. Interactions of the longer Glu side chain with the phosphate binding loop (P-loop) results in a similar conformation of the switch II region as the conformation that results from the binding of the phosphate of ADP to the P-loop. 相似文献
142.
Hwang KC Lim S Kwon HM Bae YS Kang SM Chung KH Graham RM Rhee SG Jang Y 《The Journal of steroid biochemistry and molecular biology》2004,91(3):131-138
Ischemia and simulated ischemic conditions cause intracellular Ca2+ overload in the myocardium. The relationship between ischemia injury and Ca2+ overload has not been fully characterized. The aim of the present study was to investigate the expression and characteristics of PLC isozymes in myocardial infarction-induced cardiac remodeling and heart failure. In normal rat heart tissue, PLC-delta1 (about 44 ng/mg of heart tissue) was most abundant isozymes compared to PLC-gamma1 (6.8 ng/mg) and PLC-beta1 (0.4 ng/mg). In ischemic heart and hypoxic neonatal cardiomyocytes, PLC-delta1, but not PLC-beta1 and PLC-gamma1, was selectively degraded, a response that could be inhibited by the calpain inhibitor, calpastatin, and by the caspase inhibitor, zVAD-fmk. Overexpression of the PLC-delta1 in hypoxic neonatal cardiomyocytes rescued intracellular Ca2+ overload by ischemic conditions. In the border zone and scar region of infarcted myocardium, and in hypoxic neonatal cardiomyocytes, the selective degradation of PLC-delta1 by the calcium sensitive proteases may play important roles in intracellular Ca2+ regulations under the ischemic conditions. It is suggested that PLC isozyme-changes may contribute to the alterations in calcium homeostasis in myocardial ischemia. 相似文献
143.
Dexamethasone treatment causes resistance to insulin-stimulated cellular potassium uptake in the rat 总被引:1,自引:0,他引:1
Rhee MS Perianayagam A Chen P Youn JH McDonough AA 《American journal of physiology. Cell physiology》2004,287(5):C1229-C1237
Patients treated with glucocorticoids have elevated skeletal muscle ouabain binding sites. The major Na+-K+-ATPase (NKA) isoform proteins found in muscle, 2 and 1, are increased by 50% in rats treated for 14 days with the synthetic glucocorticoid dexamethasone (DEX). This study addressed whether the DEX-induced increase in the muscle NKA pool leads to increased insulin-stimulated cellular K+ uptake that could precipitate hypokalemia. Rats were treated with DEX or vehicle via osmotic minipumps at one of two doses: 0.02 mg·kg1·day1 for 14 days (low DEX; n = 5 pairs) or 0.1 mg·kg1·day1 for 7 days (high DEX; n = 6 pairs). Insulin was infused at a rate of 5 mU·kg1·min1 over 2.5 h in conscious rats. Insulin-stimulated cellular K+ and glucose uptake rates were assessed in vivo by measuring the exogenous K+ infusion () and glucose infusion (Ginf) rates needed to maintain constant plasma K+ and glucose concentrations during insulin infusion. DEX at both doses decreased insulin-stimulated glucose uptake as previously reported. Ginf (in mmol·kg1·h1) was 10.2 ± 0.6 in vehicle-treated rats, 5.8 ± 0.8 in low-DEX-treated rats, and 5.2 ± 0.6 in high-DEX-treated rats. High DEX treatment also reduced insulin-stimulated K+ uptake. (in mmol·kg1·h1) was 0.53 ± 0.08 in vehicle-treated rats, 0.49 ± 0.14 in low-DEX-treated rats, and 0.27 ± 0.08 in high-DEX-treated rats. DEX treatment did not alter urinary K+ excretion. NKA 2-isoform levels in the low-DEX-treated group, measured by immunoblotting, were unchanged, but they increased by 38 ± 15% (soleus) and by 67 ± 3% (gastrocnemius) in the high-DEX treatment group. The NKA 1-isoform level was unchanged. These results provide novel evidence for the insulin resistance of K+ clearance during chronic DEX treatment. Insulin-stimulated cellular K+ uptake was significantly depressed despite increased muscle sodium pump pool size. skeletal muscle; sodium pump; Na+-K+-ATPase 相似文献
144.
Two enzymes in one; two yeast peroxiredoxins display oxidative stress-dependent switching from a peroxidase to a molecular chaperone function 总被引:20,自引:0,他引:20
Jang HH Lee KO Chi YH Jung BG Park SK Park JH Lee JR Lee SS Moon JC Yun JW Choi YO Kim WY Kang JS Cheong GW Yun DJ Rhee SG Cho MJ Lee SY 《Cell》2004,117(5):625-635
Although a great deal is known biochemically about peroxiredoxins (Prxs), little is known about their real physiological function. We show here that two cytosolic yeast Prxs, cPrxI and II, which display diversity in structure and apparent molecular weights (MW), can act alternatively as peroxidases and molecular chaperones. The peroxidase function predominates in the lower MW forms, whereas the chaperone function predominates in the higher MW complexes. Oxidative stress and heat shock exposure of yeasts causes the protein structures of cPrxI and II to shift from low MW species to high MW complexes. This triggers a peroxidase-to-chaperone functional switch. These in vivo changes are primarily guided by the active peroxidase site residue, Cys(47), which serves as an efficient "H(2)O(2)-sensor" in the cells. The chaperone function of these proteins enhances yeast resistance to heat shock. 相似文献
145.
The peptide HP (2-20), derived from the N-terminal sequence of Helicobacter pylori ribosomal protein L1 (RPL1), has a nematicidal activity against eggs and worms of Caenorhabditis elegans. Eggs treated with HP (2-20) (69%) has a higher fluorescence intensity with propidium iodide staining, which was similar to that of melittin (82%) but higher than untreated cells (5.7%). Confocal microscopy showed that the peptides were located in the shell of the eggs and the inner and outer surfaces of the worms. HP (2-20) therefore may exert its antinematodal activity by disrupting the structure of the egg's shell and the cell membrane via pore formation or by direct interaction with the lipid bilayers in a detergent-like manner. 相似文献
146.
Extracts ofPhellinus gilvus andPhellinus baumii inhibit pulmonary inflammation induced by lipopolysaccharide in rats 总被引:7,自引:0,他引:7
Jang BS Kim JC Bae JS Rhee MH Jang KH Song JC Kwon OD Park SC 《Biotechnology letters》2004,26(1):31-33
Compared to saline-challenged rats, rats exposed to 50 microg intratracheal lipopolysaccharide showed an increase of total white cells (from 0.3 x 10(6) to 2.4 x 10(6)), neutrophils (from 0.09 x 10(6) to 1.8 x 10(6)), the levels of tumor necrosis factor (TNF)-alpha (from 200 pg ml(-1) to 1200 pg ml(-1)), and interleukin (IL)-1beta (from 220 pg ml(-1) to 650 pg ml(-1)) in the bronchial lavage fluid. However, after pretreatment with extracts of Phellinus gilvus and Phellinus baumii, the total white cells, neutrophils, and the level of IL-1beta in lipopolysaccharide-challenged rats were similar to those in saline-challenged rats, except for TNF-alpha. The results indicate that extracts of P. gilvus and P. baumii may be useful in preventing acute pulmonary inflammation in human diseases. 相似文献
147.
Rho J Shin JH Song JW Park MR Kee SJ Jang SJ Park YK Suh SP Ryang DW 《Journal of microbiology (Seoul, Korea)》2004,42(2):80-86
Pulsed-field gel electrophoresis (PFGE) typing was applied to the epidemiological investigation of 21 Candida tropicalis isolates collected from urine specimens of 11 patients and one healthcare worker, in an intensive care unit (ICU) over a 4-month period. Seventeen epidemiologically unrelated strains from 14 patients were also tested to determine the discriminatory power of PFGE. PFGE typing consisted of electrophoretic karyotyping (EK) and restriction endonuclease analysis of genomic DNA (REAG), using two restriction enzymes (BssHII and SfiI). The EK pattern was the same in all 38 isolates, while REAG using SfiI separated the isolates into nine types. However, 16 different PFGE types were identified by REAG with BssHII, and the same results were obtained when the results of both REAG tests were combined. In serial urinary isolates from 10 patients, all strains from each patient had the same PFGE pattern. While the epidemiologically unrelated strains from 14 patients consisted of 13 different PFGE types, the 20 isolates from the 11 ICU patients fell into only two PFGE types (types C1 and C2), and these apparently originated from the two different outbreaks. All strains of type C1 (n = 12) were isolated from six patients, between November 1999 and January 2000, and all of the type C2 strains (n=8) were isolated from five patients, during January and February 2000. This study shows two consecutive clusters of C. tropicalis candiduria in an ICU, defined by PFGE typing, and also demonstrates that a PFGE typing method using BssHII is perhaps the most useful method for investigating C. tropicalis candiduria. 相似文献
148.
149.
Kyung?Mi?Lee Sun-Hee?Hwang Soon?Duck?Ha Jae-Hyuk?Jang Dong-Jung?Lim Jai-Yul?KongEmail author 《Biotechnology and Bioprocess Engineering》2004,9(4):267-273
The optimization of culture conditions for the bacteriumPseudomonas aeruginosa BYK-2 KCTC 18012P, was performed to increase its rhamnolipid production. The optimum level for carbon, nitrogen sources,
temperature and pH, for rhamnolipid production in a flask, were identified as 25 g/L fish oil, 0.01% (w/v) urea, 25 and pH
7.0, respectively. Optimum conditions for batch culture, using a 7-L jar fermentor, were 200 rpm of agitation speed and a
2.0 L/min aeration rate. Under the optimum conditions, on fish oil for 216 h, the final cell and rhamnolipid concentrations
were 5.3 g/L and 17.0 g/L respectively. Fed-batch fermentation, with different feeding conditions, was carried out in order
to increase, cell growth and rhamnolipid production by thePseudomonas aeruginosa, BYK-2 KCTC 18012P. When 2.5 g of fish oil and 100 mL basal salts medium, containing 0.01% (w/v) urea, were fed intermittently
during the fermentation, the final cell and rhamnolipid concentrations at 264 h, were 6.1 and 22.7 g/L respectively. The fed-batch
culture resulted in a 1.2-fold increase in the dry cell mass and a 1.3-fold increase in rhamnolipid production, compared to
the production of the batch culture. The rhamnolipid production-substrate conversion factor (0.75 g/g) was higher than that
of the batch culture (0.68 g/g). 相似文献
150.
To investigate the pathology of gastric disorders, we compared the proteomic patterns of gastric juice from patients with various gastric disorders. In healthy subjects pepsin A, pepsin B and gastric lipase were the major proteins detected by two-dimensional gel electrophoresis. These digestive enzymes were not detected in 60% of gastric cancer cases (18 out of 30 analyzed cases). Interestingly, an extraordinary amount of alpha(1)-antitrypsin was observed in these cases. In contrast to gastric cancer cases, alpha(1)-antitrypsin was detected in only 5% of patients (three out of 56) with chronic atrophic gastritis, and the detection frequency went up as the disease developed (one of four intestinal metaplasia cases, two of seven tubular adenoma cases, a single examined case of hyperplastic polyp and 60% of gastric cancer). Zymography showed that a 60 kDa protease strongly associated with alpha(1)-antitrypsin and mass spectrometric analysis revealed that the gastric alpha(1)-antitrypsin was a protease-cleaved form. Our data suggest that alpha(1)-antitrypsin and 60 kDa protease may serve as good diagnostic and prognostic markers for conditions associated with gastric cancer. 相似文献