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941.
The Gram‐negative periodontal pathogen Porphyromonas gingivalis produces a family of outer membrane‐anchored proteases, the gingipains, shown to play an essential role in virulence of the organism. The C‐terminal domain (CTD) of gingipains and other secreted proteins is known to be the targeting signal for maturation and translocation of the protein through the outer membrane. The CTD is subsequently cleaved during the secretion process. Multiple alignment of various CTDs failed to define a consensus sequence at the putative CTD processing site. Using mutagenesis, we were able to show that cleavage at the site is not dependent on a specific residue and that recognition of the site is independent of local sequence. Interestingly, length of the junction between the CTD and adjacent Ig‐like subdomain has a critical influence on post‐translational glycan modification of the protein, whereby insertion of additional residues immediately N‐terminal to the cleavage site results in failure of glycan modification and release of soluble protease into the culture medium. Various hypotheses are presented to explain these phenomena. Knowledge of the role CTDs play in maturation of gingipains has broader application for understanding maturation of CTD homologues expressed by bacteria of the Bacteriodetes phylum. 相似文献
942.
Marta Spodzieja Monika Rafalik Aneta Szymańska Aleksandra S. Kołodziejczyk Paulina Czaplewska 《Journal of molecular recognition : JMR》2013,26(9):415-425
Secondary amyloid A (AA) amyloidosis is an important complication of some chronic inflammatory diseases, primarily rheumatoid arthritis (RA). It is a serious, potentially life‐threatening disorder caused by the deposition of AA fibrils, which are derived from the circulatory, acute‐phase‐reactant, serum amyloid A protein (SAA). Recently, a specific interaction between SAA and the ubiquitous inhibitor of cysteine proteases—human cystatin C (hCC)—has been proved. Using a combination of selective proteolytic excision and high‐resolution mass spectrometry, the binding sites in the SAA and hCC sequences were assessed as SAA(86–104) and hCC(96–102), respectively. Here, we report further details concerning the hCC–SAA interaction. With the use of affinity tests and florescent ELISA‐like assays, the amino acid residues crucial for the protein interaction were determined. It was shown that all amino acid residues in the SAA sequence, essential for the formation of the protein complex, are basic ones, which suggests an electrostatic interaction character. The idea is corroborated by the fact that the most important residues in the hCC sequence are Ser‐98 and Tyr‐102; these residues are able to form hydrogen bonds via their hydroxyl groups. The molecular details of hCC–SAA complex formation might be helpful for the design of new compounds modulating the biological role of both proteins. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
943.
Yan Zheng Xiao-quan Shan Peng Sun Long-zhu Jin 《Chemical Speciation and Bioavailability》2013,25(1):30-36
AbstractThe feasibility of using reversed-phase high performance liquid chromatography (RP-HPLC) for the separation of metallothioneins (MTs) and subsequent determination of cadmium in MTs by graphite furnace atomic absorption spectrometry (GFAAS) in rabbit kidney and liver has been studied. RP-HPLC was used to isolate, characterise and quantitate liver and kidney MT isoforms. The MTs were eluted from a radially compressed C18 column with a neutral sodium phosphate buffer and detected by UV absorbance at 254 nm. Rabbit liver MTs was found to be comprised of seven distinct isoforms with five of which were found to be subspecies of the MT-I isoform. Rabbit kidney MTs exhibited only two predominant isoforms. A standard calibration curve was constructed using purified rabbit kidney MT-I and MT-II which demonstrated excellent linear correlation between peak height and the quantity of MT injected into the column. Recovery of MT from RP-HPLC was found to exceed 90%. Kidney and liver tissues from rabbit by feeding low levels of cadmium in diets was assayed using the RP-HPLC analysis of cytosol samples. Feeding stable cadmium in the diet resulted in the deposition of MT in the kidney rather than in the liver. The cadmium content in MT isoforms was determined by GFAAS. Less than 10% of the total cadmium in kidney was associated with MTs. 相似文献
944.
Jin Sun Xiao-Li Hu Guo-Wei Le Yong-Hui Shi 《World journal of microbiology & biotechnology》2013,29(2):209-216
Iron (Fe) can promote hydrogen peroxide (H2O2) and hydroxyl radical generation in the colonic surface and promote growth of Fe-dependent bacteria. Some Lactobacillus strains are resistant to oxygen free-radicals, allowing them to survive in a Fe-modulated mucosal environment and influence colon microbial ecology and redox state. Here, we investigated the capacity of lactobacilli with different antioxidant abilities to modify the bacterial profile and prevent oxidative stress in the colon of Fe-overloaded mice. Survival time of Lactobacillus rhamnosus LGG (LGG) in the presence of H2O2 and hydroxyl radical was significantly longer compared with the mid- and non-antioxidative strains, Lactobacillus paracasei Fn032 and Lactobacillus plantarum Fn001, respectively. Different Lactobacillus strains are specific in free-radical scavenging activities of their cell-free extracts, which increased to varying extent depending on strains when bacteria were exposed to simulated gastric and pancreatic juice. Fe-overloaded mice showed increased colonic luminal ferrous Fe content, Enterococcus and Escherichia coli concentrations, mucosal malondialdehyde and free-radicals, and decreased mucosal total antioxidative capacity and oxidative enzymatic activity. Translocation of endotoxin to the liver was also significantly increased (P < 0.05). Lactobacilli inhibited ferrous Fe accumulation, especially in LGG and Fn032. LGG significantly inhibited the increase of colonic mucosal free-radicals and malondialdehyde content (P < 0.05). Fn032 only inhibited malondialdehyde (P < 0.05). LGG and Fn032 significantly inhibited increases in colonic Enterococcus (P < 0.05). Fn001 showed no significant antioxidative ability in vivo. The difference of these effects in vivo were well agreed with scavenging activities against reactive oxygen species (ROS) of simulated gastrointestinals fluid pretreated cells in vitro. In conclusion, ROS scavenging activities was essential for Lactobacillus to prevent oxidative stress in vivo and inhibition of ROS-producing bacterial growth and mucosal barrier injury. 相似文献
945.
946.
Water stress and nutrient deficiency are considered to be the main environmental factors limiting plant growth and species interaction in semiarid regions. However, less is known about the interactive effects of soil water, nitrogen and phosphorus on native species growth and relative competitive ability. A replacement series design method was used with 12 mixed plants of Bothriochloa ischaemum and Lespedeza davurica grown in a pot experiment under three water regimes and four fertility treatments. Intercropping systems were assessed on the basis of indices such as biomass production and allocation, relative competitive ability, aggressivity, relative yield total and water use efficiency (WUE). Water stress decreased significantly the total biomass production for each species, either in monoculture or in mixtures. N, P, or NP application can significantly improve biomass production of the two species in their mixtures. There was no obvious change trend in root/shoot ratio of B. ischaemum or L. davurica in different mixture proportions. Relative yield total (RYT) values ranged from 0.98 to 1.39. Aggressivity values of B. ischaemum to L. davurica were positive in all water regimes and fertilizations, implying that B. ischaemum was the dominant species. Relative competition intensity values of B. ischaemum (i.e., RCIB) were less than zero, while greater than zero for L. davurica (i.e., RCIL), indicating that the effects of intraspecific competition with L. davurica were stronger for B. ischaemum, and the opposite for L. davurica. WUE increased gradually as the proportion of B. ischaemum increased in mixtures, and a 10:2 B. ischaemum:L. davurica mixture proportion had significantly higher WUE. Results suggest that it is advantageous to grow the two species together to maximize biomass production and the recommended mixture ratio was 10:2 of B. ischaemum to L. davurica because it gave higher RYT and significantly higher WUE under conditions of water deficit. 相似文献
947.
Ikuo Matsui Toshiyuki Kameyama Kunio Oishi Ko Aida 《Bioscience, biotechnology, and biochemistry》2013,77(3):833-835
The inhibitory effects of 3-nitro-2,4,6-trihydroxybenzamide derivatives on human 5-lipoxygenase (5-LO), a key enzyme in arachidonic acid cascades, were examined using 5-LO produced by Escherichia coli. Some of the tested compounds inhibited the conversion of arachidonic acid to 5-hydroperoxy-6,8,11,14-eicosatetraenoic acid (5-HPETE), and in particular the N-phenylbutyl derivative was about 30 times more active (IC50 = 35 μm) than caffeic acid (IC50 = 1000 μm), a known selective 5-LO inhibitor. 相似文献
948.
Shinji Iijima Oh Man Jin Takashi Saiki Teruhiko Beppu 《Bioscience, biotechnology, and biochemistry》2013,77(3):773-774
A structural study of the water-soluble dextran made by Leuconostoc mesenteroides strain C (NRRL B-1298) was conducted by enzymic degradation and subsequent 13C-NMR analysis of the native dextran and its limit dextrins. The α-l,2-debranching enzyme removed almost all of the branched D-glucose residues, and gave a limit dextrin having a much longer sequence of the internal chain length (degree of linearity: n = 24.5 compared with the value of n = 3.3 for the native dextran). The degree of hydrolysis with debranching enzyme corresponded to the content of α-1,2-linkages determined by chemical methods, which suggested that most of the α-l,2-linkages in the dextran B-1298 constituted branch points of a single D-glucose residue. A synergistic increase of susceptibility of the dextran B-1299 was observed by simultaneous use of debranching enzyme and endodex-tranase. 13C-NMR spectral analysis indicated the similarity of structure of dextran B-1298 to that of B-1396, rather than that of B-1299. Occurrence of α-l,3-linkages in the limit dextrin was supported by a newly visualized chemical shift at 83.7 ppm. 相似文献
949.
The α-d-galactosidases of six Streptomyces strains were examined on their inducer susceptibility, substate specificity, and inhibitor susceptibility. In all strains examined, α-d-galactosidase was induced by d-galactose, but neither by d-fucose nor by l-arabinose. α-d-Fucosidase activity was always induced accompanying with α-d-galactosedase activity. β-l-Arabinosidase activity, however, was never observed. These α-d-galactosidases were purified to electrophoretically pure degree by successive ammonium sulfate and ethanol precipitation, and ion exchange and gel filtration chromatography. The purified preparations from six strains were different from each other in their chromatographic behaviors and in some physical properties, but they all showed strong α-d-fucosidase activity as well. The α-d-galactosidase activities were strongly inhibited by d-galactose and l-arabinose, but scarcely by d-fucose. On the other hand, their α-d-fucosidase activities were inhibited by d-fucose as well as by d-galactose and l-arabinose. 相似文献
950.
l-Glutamic acid was formed from d-, l-, and dl-PCA with cell-free extract of Pseudomonas alcaligenes ATCC-12815 grown in the medium containing dl-PCA as a sole source of carbon and nitrogen. The enzyme(s) involved in this conversion reaction was distributed in the soluble fraction within the cell and in 0.5 saturated fraction at the fractionation procedure with the saturation of ammonium sulfate. Optimum pH of this enzyme(s) lied at pH 8.5 and optimum temperature was 30°C. Cu (5 × 10?3 m) inhibited the reaction considerably while Ca or Fe accelerated it. PALP (1×10?3 m) also gave an enhanced activity to some extent. The enzyme preparation converted dextro-rotatory enan-thiomorph of PCA to its laevo-rotatory one which in turn was not converted to the opposite rotation direction by this enzyme. Furthermore, the preparation did not, if any, show d-glutamic acid racemase activity. Isotopic experiments with using dl-PCA-1-14C revealed that l-glutamic acid-1-14C was formed by the cleavage of –CO–NH– bond of pyrrolidone ring of PCA. It was concluded that dl-PCA when assimilated by the present bacterium is at first transformed to l-PCA by the optically isomerizing enzyme and subsequently is cleaved to l-glutamic acid probably by the PCA hydrolysing enzyme. 相似文献