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211.
Naoki Kamo Tohru Yoshioka Mizuko Yoshida Tohru Sugita 《The Journal of membrane biology》1973,12(1):193-205
Summary A model membrane composed of a filter paper and dioleylphosphate was studied by applying various kinds of external stimuli. When the concentration in the external solution was varied successively, the physico-chemical properties of the membrane changed drastically at a certain valueC
t
. The relationships between the electrical response and the external stimuli studied are as follows: (1) The membrane potential oscillates spontaneously in a spikelike fashion when the concentration of the external solution is suddenly changed. (2) The current through the membrane oscillates in spikelike fashion for a duration of about 50 msec when the constant external voltage, V larger than a certain value V
c
, is applied across the membrane. (3) The electric resistance sharply decreases, and a kind of action potential similar to that observed in living tissues is produced when a short rectangular electric stimulus, whose magnitude is higher than a critical value V
p
, is applied. (4) If a hydrostatic pressure difference across the membrane is applied with appropriate salt conditions, the value of the membrane potential varies with time, as in the case of (3). The observed changes in emf and electric resistance are discussed in connection with the conformational change of DOPH molecules in the membrane. 相似文献
212.
Luo Yao-Hua; Steinberg Leonel; Suda Shoichiro; Kumazawa Shuzo; Mitsui Akira 《Plant & cell physiology》1991,32(6):897-900
Cyanobacteria, having primary photosynthetic reactions similarto higher plants, are capable of producing large quantitiesof molecular hydrogen by nitrogenase and/or hydrogenase deliveringelectrons to hydrogen ions via ferredoxin or oxidation of NADPH.We measured the deuterium/hydrogen (D/H) ratios of the hydrogengas photoproduced by Synechococcus sp. Miami BG 043511 and Anabaenasp. TU 37-1, and demonstrate that D values of their hydrogengas are extremely low (about 600%) when compared withthat of available water (7%).This depletion gives a meanfractionation factor (a) of 0.43, which is similar to that calculatedfor hydrogen ions at equilibrium with water (0.35) and hydrogenproduced by electrolysis of water (0.24) but significantly differentfrom those of carbon bound hydrogens (>0.83). Thus hydrogenions available for protonation of NADP+ may be extremely deuteriumdepleted. Our results may explain why D/H ratios of nitratedcellulose or lipids from most plants are always depleted relativeto water available for photosynthesis.
3 On leave from School of Marine Science and Technology, TokaiUniversity, 3-20-1 Orido, Shimizu, 424 Japan (Received April 1, 1991; Accepted June 21, 1991) 相似文献
213.
K Sugita Y Torimoto Y Nojima J F Daley S F Schlossman C Morimoto 《Journal of immunology (Baltimore, Md. : 1950)》1991,147(5):1477-1483
We developed a new mAb, anti-1A4, which recognizes an epitope on the CD27 molecule distinct from those recognized by several known anti-CD27 mAb. Although it has been suggested that the CD27 molecule is a T cell activation Ag, there was little direct evidence that the structure was involved in the T cell activation process. In this study, we showed that anti-1A4 inhibited anti-CD2, anti-CD3, mitogens, or soluble Ag-induced T cell proliferation as well as PWM-driven B cell IgG synthesis. Interestingly, anti-1A4 inhibited IL-2 secretion without affecting IL-2R expression. In addition, pretreatment of T cells with anti-1A4 inhibited the normally sustained intracellular calcium mobilization seen after triggering of T cells via the CD2 or CD3 pathways. Thus, binding of anti-1A4 to the CD27 molecule appears to induce a negative effect on T cell activation. This may be due to either a direct signal to T cells or the blocking of an interaction between T cells and accessory cells or both. These findings support the notion that the CD27 molecule plays an integral role in the process of T cell activation. 相似文献
214.
1. A Suc-APA-MCA hydrolytic activity was significantly decreased in murine erythroleukemia cells during DMSO-induced differentiation, but not in DMSO-resistant cells. 2. The Suc-APA-MCA hydrolytic enzyme was purified by ion exchange, adsorption, gel filtration and affinity chromotographies. The results of the chromatographies showed that only one enzyme hydrolyzed Suc-APA-MCA in MEL cells. 3. This enzyme is more sensitive to hydrolysis by Suc-GPLGP-MCA than Suc-APA-MCA at slightly acidic pH, and its activity is stimulated by 2-mercaptoethanol. 4. A cysteine proteinase inhibitor did not affect the activity, but a specific inhibitor of prolyl endopeptidase, Z-thioprothiazolidine, completely inhibited it. These results suggest that the Suc-APA-MCA hydrolytic enzyme is identical to a prolyl endopeptidase. 相似文献
215.
Exploring the molecular basis for variability among patients with Becker muscular dystrophy: dystrophin gene and protein studies. 总被引:35,自引:9,他引:26
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A H Beggs E P Hoffman J R Snyder K Arahata L Specht F Shapiro C Angelini H Sugita L M Kunkel 《American journal of human genetics》1991,49(1):54-67
Becker muscular dystrophy (BMD) often results from in-frame mutations of the dystrophin gene that allow production of an altered but partially functional protein. To address potential structure-function relationships for the various domains of dystrophin, we examined both the dystrophin gene and protein in 68 patients with abnormal dystrophin. Eighty-six percent of BMD patients with dystrophin of altered size have deletions or duplications, and the observed sizes of dystrophin fit well with predictions based on DNA data. Deletions within the amino-terminal domain I tended to result in low levels of dystrophin and a more severe phenotype. The phenotypes of patients with deletions or duplications in the central rod domain were more variable. This region can be divided into three portions based on differences in clinical presentations of patients. Deletions around exons 4553 were most common and generally caused typical BMD; however, phenotypic variability among patients with similar mutations suggests that epigenetic and/or environmental factors play an important role in determining the clinical progression. In contrast, deletions or duplications in the proximal portion of this domain tended to cause severe cramps and myalgia. Finally, loss of the middle of this region probably causes a very mild phenotype, as only one such patient was found and his only symptom was elevated serum creatine phosphokinase levels. 相似文献
216.
Isao Matsui Shuzo Otani Masaharu Kamei Seiji Morisawa 《Chemico-biological interactions》1984,51(2):141-149
Effect of sodium butyrate on DNA synthesis and the induction of ornithine decarboxylase (EC 4.1.1.17), a rate-limiting enzyme of polyamine biosynthesis, was studied in phytohemagglutinin(PHA)-stimulated bovine lymphocytes. Millimolar concentrations of butyrate completely inhibited the incorporation of [3H] thymidine into the acid-insoluble fraction and reversibly suppressed the induction of ornithine decarboxylase. Other shortchain fatty acids were much less active than butyrate. These results suggest that the suppression of ornithine decarboxylase activity may be one of the reasons for the inhibition of DNA synthesis with butyrate in bovine lymphocytes, because our previous experimental results have shown that the induction of ornithine decarboxylase closely correlates with the DNA synthesis in growth-stimulated cells. 相似文献
217.
Two forms of cytochrome b5, a soluble erythrocyte form and a membrane-bound liver form, were purified from pig and human, and structural differences between them were analyzed. Porcine and human erythrocyte cytochrome b5 consisted of 97 amino acid residues and contained the same catalytic domain structure (residues 1-96) as that of the corresponding liver cytochrome b5, but had one amino acid replacement at the C-terminus (residue 97). These results suggest that erythrocyte cytochrome b5 is not derived from the liver protein by proteolysis but a translational product from another distinct mRNA of cytochrome b5. 相似文献
218.
Specific and high titer antisera against 4-O-methylglucuronic acid-containing glycosphingolipid (Lipid IV) from spermatozoa of the fresh-water bivalve, Hyriopsis schlegelii, were raised in rabbits. The antisera were found to agglutinate spermatozoa of three fresh-water bivalves, H. schlegelii, Anodonta woodiana, and Cristaria plicata (Palaeoheterodonta), but they did not agglutinate those of Corbicula sandai (Heterodonta). The specificity of the agglutination was examined by an inhibition test using various carbohydrates, from which it was concluded that an antigenic determinant is GlcA4Me-Fuc. Immunohistochemical studies indicated that Lipid IV exists on the cell surface of the spermatozoa. 相似文献
219.
Cloning and characterization of the mutated threonine operon (thrA(1)5A(2)5BC) of Serratia marcescens 总被引:3,自引:0,他引:3
The entire threonine operon (thrA(1)5A(2)5BC) of Serratia marcescens TLr156, which lacks threonine-mediated feedback inhibition of both aspartokinase I (AK I) and homoserine dehydrogenase I (HD I), was cloned on a multicopy plasmid pLG339. Hybrid plasmid pSK301 carried a 6.5-kb chromosomal DNA. Several derivatives of pSK301 with Tn1000 insertions were obtained. By examining the phenotypes and the physical maps of these plasmids, we could define the loci of the thrA(1)5A(2)5, thrB, and thrC genes. The thrA(1)5A(2)5 and thrC gene products were identified by the maxicell method as proteins with Mrs of 85,000 and 43,000, respectively. The thrA(1)5A(2)5 genes encode a single polypeptide similar to the thrA1A2 genes of Escherichia coli. Plasmid pSK301 was introduced into S. marcescens T-1112, in which both AK I and HD I are produced constitutively. The resulting transformant carried five to six copies of pSK301 per chromosome and produced the AK I and HD I enzymes at three to four times higher level than control strain T-1112[pLG339]. Strain T-1112[pSK301] produced four times higher levels of threonine than strain T-1112[pLG339], yielding about 35 mg of threonine per ml of a medium containing sucrose and urea. 相似文献
220.
The bacterial flora in the intestinal tract of goldfish (Carassius auratus) was investigated at different stages of fish development. The floras of the diets and the water and sediment of a culture pond were also analyzed. The total counts in the intestine ranged from 2.2 × 106–2.1 × 108 cells g–1 wet weight.Aeromonas hydrophila, A. punctata, Pseudomonas, Bacteroidaceae andClostridium species were the common components in the intestinal tract of goldfish from larvae to adult stage.Bacteroides type A appeared at 44 days with a density of 103 cells g–1 and then predominated with densities of 105–107 cells g–1. The intestinal microflora of goldfish become relatively stable after 67 days of hatching. These observations suggest that the intestinal microflora of adult goldfish becomes established approximately 2 months after hatching. 相似文献