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901.
5'-Methylbenzimidazolyl-cobamides are the corrinoids from some sulfate-reducing and sulfur-metabolizing bacteria 总被引:3,自引:0,他引:3
The sulfate-reducing bacteria Desulfobacterium autotrophicum, Desulfobulbus propionicus and Archaeoglobus fulgidus (VC-16) and the sulfur-metabolizing archaebacteria Desulfurolobus ambivalens and Thermoplasma acidophilum were found to contain considerable amounts of corrinoids, that were isolated and crystallized in their Co beta-cyano form. In three other sulfur-metabolizing archaebacteria, Thermoproteus neutrophilus, Pyrodictium occultum and Staphylothermus marinus significant amounts of corrinoids were not detected under the isolation methods used. The samples from the three sulfate-reducers were identified with Co alpha-[alpha-(5'-methylbenzimidazolyl)]-Co beta-cyanocobamide. This corrinoid was also obtained from a 5-methylbenzimidazole-supplemented Propionibacterium fermentation and was structurally characterized by ultraviolet/visible, CD, fast-atom-bombardment MS, 1H-and 13C-NMR spectroscopy. Also the major corrinoid from T. acidophilum was (tentatively) analyzed as a 5'-methylbenzimidazolyl-cobamide, whereas the main corrinoid from D. ambivalens was indicated to be vitamin B12 (a 5',6'-dimethylbenzimidazolyl-cobamide). The 5'-methylbenzimidazolylcobamides are found here as the common corrins of some sulfate-reducing and sulfur-metabolizing bacteria. The structural diversity due to the differing nucleotide bases of the corrins examined here and in methanogenic and acetogenic bacteria appears not to correlate to the biological function(s) of the corrins, but rather to be determined by biosynthetic properties of these organisms under natural growth conditions. 相似文献
902.
When calf aortic tissue, preincubated under organ culture conditions in the presence of [35S]sulfate, was submitted to a sequential collagenase and elastase digestion and guanidinium chloride extraction, the bulk of proteoheparan sulfate was obtained in the elastase fraction. Ion-exchange chromatography on DEAE-cellulose of the elastase digest under dissociative conditions yielded a proteoglycan fraction that contained heparan sulfate as the sole glycosaminoglycan. The proteoheparan sulfate fraction was resolved into a high-molecular-mass (P-HS 1) and a low-molecular-mass (P-HS 2) fraction by gel filtration on Sephacryl S-400. P-HS 1 has a Mr of 175,000 and possesses four heparan sulfate side-chains (Mr 32,000) covalently bound to the protein core via a galactose- and xylose-containing polysaccharide-protein binding region. The protein core (Mr 38,000), which was obtained after deglycosylation of PG-HS 1 with trifluormethane sulfonic acid, contained in addition a few N-glycosidically linked oligosaccharide units representing a complex type with terminal neuraminic acid residues. P-HS 2 is a single-chain peptidoheparan sulfate of Mr of 38,000 containing one heparan sulfate chain (Mr 32,000) linked to a polypeptide (Mr 6000). The ratio of specific radioactivities of P-HS 1 and P-HS 2 was 1:0.66. 相似文献
903.
E Benedikt A Gossauer H P K?st W Miki K Yamaguchi 《European journal of biochemistry》1988,175(3):643-648
The ovaries of the marine snail Turbo cornutus contain a number of pigments. So far, the presence of carotenoids and a chromoprotein with a bile pigment, called turboverdin (= 3(2)-hydroxy-mesobiliverdin IX alpha), as its prosthetic group are known. The present work describes the isolation and structure elucidation of two further bile pigments, biliverdin IX delta and neobiliverdin IX delta. This is the first report of naturally occurring bile pigments with IX delta structure. 相似文献
904.
Levels of 7 alpha-hydroxy-4-cholesten-3-one in plasma reflect rates of bile acid synthesis in man 总被引:2,自引:0,他引:2
A method for analysis of 7 alpha-hydroxy-4-cholesten-3-one in plasma is described. Following solid-phase extraction/purification the compound is determined by high-performance liquid chromatography using a UV detector. The median concentration in healthy subjects was 12 ng/ml (range 3-40). The levels were lower in diseases associated with a low bile acid production: extrahepatic cholestasis, less than 1.5 ng/ml (range less than 0.9-3); liver cirrhosis less than 1.5 ng/ml (range less than 0.9-38), and higher in diseases associated with a high bile acid production: cholestyramine treatment, 188 ng/ml (range 54-477); ileal resection 397 ng/ml (range 128-750). The levels were essentially normal in patients with colon resection. The results are consistent with a strong positive correlation between the levels of 7 alpha-hydroxy-4-cholesten-3-one in plasma and the rate of bile acid synthesis. 相似文献
905.
The kinetics of complex formation between recombinant hirudin or recombinant hirudin mutants with thrombin were analyzed. In order to elucidate the inhibitor's reactive site peptide bond predetermined amino acid substitutions were introduced at positions of basic amino acid residues by means of site-directed mutagenesis of a hirudin gene. In comparison to recombinant hirudin (Ki = 19 pM) only those mutant inhibitors which were modified at amino acid position Lys47 showed a higher Ki value for their complexes with thrombin. The observed effects are mainly due to increased koff rate constants. 相似文献
906.
Trypanosoma cruzi: origin of metacyclic trypomastigotes in the urine of the vector Triatoma infestans 总被引:1,自引:0,他引:1
Population density and percentage of the different stages of an established infection of Trypanosoma cruzi were determined for two parts of the excretory system and for the rectum of fifth instars of Triatoma infestans unfed and 4 hr after feeding. These data were also evaluated for feces and urine of the fed bugs. In the first unfed group only small populations of the flagellate occurred in the Malpighian tubules and ampullae and not in all bugs. The three rectal populations (rectal lumen and anterior and posterior rectal wall) consisted of approximately equal numbers. About 10% were spheromastigotes and about 10% were stages intermediate to epimastigotes. Significantly fewer epimastigotes and more trypomastigotes were present on the rectal wall than in the lumen. Two intermediate forms leading to the trypomastigote stage occurred in similar numbers. In nearly all bugs the initial excretion (feces) contained the highest number of flagellates as compared to the following drops of urine. More flagellates were excreted through the urine than were contained in the excretory system of unfed bugs. The population in the feces reflected the percentage of forms present in the rectal lumen of unfed bugs, but in the urine the percentage of trypomastigotes increased up to 100%. Four hours after blood uptake, dissection of bugs still showed parasites in the Malpighian tubules and ampullae; the total number of parasites in the rectum was reduced by more than 50%. This reduction was more pronounced in the rectal lumen and on the posterior rectal wall. In stained smears from all three rectal populations there were rarely spheromastigotes but high percentages of epimastigotes. The intermediate stages leading to trypomastigotes mainly originated from short epimastigotes. Comparison of the T. cruzi populations before and after feeding demonstrates that the trypomastigotes in the urine should originate from the rectal wall, especially from the posterior part. 相似文献
907.
Expression of the chemically synthesized gene for ribonuclease T1 in Escherichia coli using a secretion cloning vector 总被引:3,自引:0,他引:3
R Quaas Y McKeown P Stanssens R Frank H Bl?cker U Hahn 《European journal of biochemistry》1988,173(3):617-622
The gene for ribonuclease T1 from Aspergillus oryzae has been chemically synthesized using the segmental support technique. An Escherichia coli clone producing the ribonuclease at high levels was constructed by linking the gene downstream to the region coding for the signal peptide of the OmpA protein (a major outer membrane protein of E. coli), using the secretion cloning vector pIN-III-ompA2. This strategy was employed in order to circumvent a possible toxic effect of the gene product on the host cell. Active ribonuclease containing four additional amino acids at the N-terminus could be isolated from the periplasmic fraction of the host. The final yield after purification was 20 mg enzyme/l liquid culture. With respect to immunological, catalytic and specific behaviour, no qualitative differences could be detected between the enzyme from the over-producing E. coli strain and ribonuclease T1 isolated from A. oryzae. 相似文献
908.
Fibrinolysis, the body's ability to degrade fibrin, is an integrated part of hemostasis. Overactivity in the fibrinolytic system causes bleeding and underactivity causes thrombosis. Tissue plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1), alpha 2-antiplasmin (alpha 2-AP) and plasminogen are definitely involved in fibrinolysis because: (1) these components can be assigned a fibrinolytic role in purified systems, i.e. in vitro, and (2) abnormal structural variants and abnormal levels of these components give rise to bleeding or to thrombosis. The biological control of tPA-mediated fibrinolysis is both cellular and humoral. The cellular regulation compasses synthesis of tPA and PAI-1 and release/uptake of these components. The humoral regulation involves: (1) the reaction between tPA and PAI-1; (2) the fibrin-stimulated plasminogen activation; (3) the reaction between plasmin and alpha 2-AP and (4) plasmin degradation of fibrin. The highly developed biological control of tPA-mediated fibrinolysis is indicative of its physiological importance. 相似文献
909.
Cytology, DNA and host-symbiont relationships of x-like endosymbionts from Paramecium caudatum are described. The symbionts (Caedibacter caryophila, sp. nov.) live in the macronuclei of their hosts. They confer the killer trait upon their hosts and appear well adapted to their endonucleobiotic way of life. R bodies (proteinaceous ribbons associated with killing) are produced, but differ significantly from any of the four R-body classes previously described. C. caryophila and their R bodies were isolated. DNA was extracted from purified symbionts and used to demonstrate that one P. caudatum line harbors a natural mutant which is deficient in R-body production. Melting studies indicate a GC content of 34.6%. No sequence homology between the C. caryophila DNA and the coding sequence for type 51 R-body production was observed. C. caryophila is parasitic, causing the death of its hosts in starving cultures. 相似文献
910.
Immortalized differentiated hepatocyte lines derived from transgenic mice harboring SV40 T-antigen genes 总被引:9,自引:0,他引:9
D Paul M H?hne C Pinkert A Piasecki E Ummelmann R L Brinster 《Experimental cell research》1988,175(2):354-362
Hepatocytes of transgenic mouse fetuses harboring SV40 virus transforming gene sequences in the SV delta e-MGH fusion gene construct 202 driven by the mouse metallothionein (MT-I) enhancer [R. D. Palmiter, H. Y. Chen, A. Messing, and R. L. Brinster (1985) Nature (London) 316, 457-460] were cultured at Day 19 of gestation and established as a differentiated line expressing albumin and alpha-fetoprotein (AFP) mRNAs. Hepatocyte line FMH-202 contains integrated SV40 sequences, expresses SV40 T-antigen genes, and exhibits unlimited growth potential because it has been cultured 18 months without apparent decrease in cell viability or in growth rate that could suggest the occurrence of a crisis period. Immortalized cells multiply in chemically defined medium deficient in arginine with transferrin plus insulin, whereas EGF, insulin, and transferrin are obligatory requirements for fetal or newborn mouse hepatocyte multiplication in primary cultures. Cells did not grow in agar and were not tumorigenic in nude mice. Their immortalized, nonmalignant phenotype was further documented by low saturation densities of confluent monolayers showing no overgrowth, and by growth arrest in the absence of insulin with subsequent induction of DNA synthesis and resumption of cell growth in response to insulin. Thus, it appears that immortalized SV40 T-antigen-expressing hepatocytes are present in the liver of the transgenic mice. However, at later points in liver development the transforming activity of T-antigen becomes apparent and leads to hepatocellular carcinoma formation in vivo. 相似文献