全文获取类型
收费全文 | 376篇 |
免费 | 37篇 |
国内免费 | 1篇 |
专业分类
414篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 13篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 23篇 |
2013年 | 17篇 |
2012年 | 26篇 |
2011年 | 20篇 |
2010年 | 20篇 |
2009年 | 13篇 |
2008年 | 23篇 |
2007年 | 17篇 |
2006年 | 22篇 |
2005年 | 22篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1966年 | 2篇 |
1962年 | 2篇 |
1961年 | 2篇 |
1960年 | 1篇 |
1950年 | 1篇 |
1949年 | 1篇 |
1938年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有414条查询结果,搜索用时 0 毫秒
1.
Sensitivity of some marine bacteria, a moderate halophile, and Escherichia coli to uncouplers at alkaline pH. 总被引:4,自引:2,他引:2
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The inhibitory effects of uncouplers on amino acid transport into three marine bacteria, Vibrio alginolyticus 118, Vibrio parahaemolyticus 113, and Alteromonas haloplanktis 214, into a moderate halophile, Vibrio costicola NRC 37001, and into Escherichia coli K-12 were found to vary depending upon the uncoupler tested, its concentration, and the pH. Higher concentrations of all of the uncouplers were required to inhibit transport at pH 8.5 than at pH 7.0. The protonophore carbonyl cyanide m-chlorophenylhydrazone showed the greatest reduction in inhibitory capacity as the pH was increased, carbonyl cyanide p-trifluoromethoxyphenylhydrazone showed less reduction, and 3,3',4',5-tetrachlorosalicylanilide was almost as effective as an inhibitor of amino acid transport at pH 8.5 as at pH 7.0 for all of the organisms except A. haloplanktis 214. Differences between the protonophores in their relative activities at pHs 7.0 and 8.5 were attributed to differences in their pK values. 3,3',4',5-Tetrachlorosalicylanilide, carbonyl cyanide m-chlorophenylhydrazone, 2-heptyl-4-hydroxyquinoline-N-oxide, and NaCN all inhibited Na+ extrusion from Na+-loaded cells of V. alginolyticus 118 at pH 8.5. The results support the conclusion that Na+ extrusion from this organism at pH 8.5 occurs as a result of Na+/H+ antiport activity. Data are presented indicating the presence in V. alginolyticus 118 of an NADH oxidase which is stimulated by Na+ at pH 8.5. 相似文献
2.
Electrophoretic analysis of polyphenoloxidase isoenzymes from a variety of angiosperms and from mushroom revealed that the enzymes remain active in the presence of 0.1 % sodium dodecylsulfate. Electrophoresis in the presence of sodium dodecylsulfate allows the detection of latent enzyme forms of polyphenoloxidase, and can also convert slower migrating enzyme forms to faster migrating forms. Electrophoresis in the absence of sodium dodecylsulfate followed by incubation in the presence of sodium dodecylsulfate can also be used to detect latent forms of polyphenoloxidase. Together, these approaches provide a method for screening latent enzymes and give some insight into the mechanism of activation by sodium dodecylsulfate. 相似文献
3.
Summary Molar tooth germs from three-day-old rats were cultured successfully for fourteen days, permitting the study of the development in vitro of both extracellular matrix and cellular elements such as odontoblasts and ameloblasts. The ultrastructure of the cultured tooth germs was compared with the ultrastructure of tooth germs in vivo at a comparable developmental stage. Progenitor cells of odontoblasts and ameloblasts were found to differentiate in vitro. Odontoblasts seemed to contain more lysosome-like bodies and fewer secretory granules than in vivo. They formed normally mineralizing dentine or a thick layer of dense, unmineralized predentine with incidentally some amorphous, extracellular material. Enamel was exclusively present opposite well developed dentine. It was often hyperor hypomineralized and enamel rods were not as regularly shaped as in vivo. In places where no enamel formation had taken place, large amounts of amorphous extracellular material were sometimes seen. From these observations it can be concluded that cellular development in cultured tooth germs appeared more or less normal, but extracellular matrix formation and mineralization were sometimes disturbed. 相似文献
4.
Ellen Whited Collisson Birger Andersson Marika Rönnholm Eddie W. Lamon 《Cellular immunology》1983,79(1):44-55
Modulation of antibody responses induced by IgM directed against the immunogen was investigated. When IgM directed against ox erythrocytes (ORBC) was given together with trinitrophenyl (TNP)-ORBC, the subsequent antibody response to the carrier, ORBC, as well as the response to the hapten, TNP, was potentiated. In contrast, IgG with carrier specificity inhibited both responses. The hapten-specific potentiation was found in both direct and indirect plaques, and was antigen-dose dependent, i.e., no potentiation was found with the lowest antigen doses. The response to 2,4-dinitrophenyl (DNP)-labeled proteins was potentiated by a monoclonal IgM with specificity for the hapten. The effects were observed both in primary and secondary responses. One strict requirement for IgM potentiation to occur was observed. The determinant against which potentiation was achieved had to be physically linked to the determinant against which the IgM was directed, be it hapten or carrier determinants. Thus, irrelevant IgM-antigen complexes were incapable of potentiating the responses. Similar specificity requirements were found for IgG induced suppression of antibody responses. Experiments with nude mice and their euthymic littermates showed that IgM potentiation of antibody production is T-cell dependent. Furthermore, passive transfer of carrier-primed spleen cells together with antigen challenge suggests that IgM potentiation of secondary antibody responses is dependent on specific carrier-primed immune T cells. 相似文献
5.
J. H. Wisse Anneke Zweers J. F. Jongkind W. S. Bont H. Bloemendal 《The Biochemical journal》1966,99(1):179-188
1. A new procedure is described for the purification of alpha-crystallin, including: preparative zone electrophoresis, density-gradient centrifugation and gel filtration. The total amino acid composition of highly purified samples prepared according to this procedure has been determined. 2. Evidence is presented for the presence of intermediates in the urea-induced splitting of alpha-crystallin into sub-units. A possible mechanism for this splitting is proposed. 3. The recombination of sub-units has been studied by polyacrylamide-gel electrophoresis and ultracentrifugal analysis. As judged from these criteria, only a partial recovery of starting material was obtained. 4. The origin of the minor bands in the electrophoretic pattern of alpha-crystallin on 7m-urea-polyacrylamide gel has been investigated. No evidence was found that their presence is due to carbamoylation or sulphide-disulphide interchange. They probably arise from isomerization. 5. The mean molecular weight of the sub-units was calculated to be 24000 (Archibald's method). Determination of the sedimentation-diffusion equilibrium revealed a value of 21000 at the meniscus. Assuming that all sub-units contain one cysteine residue/molecule, 23000 can be derived for the mean molecular weight. 相似文献
6.
7.
Summary Dentine phosphoprotein (DPP) was localized on thin frozen sections of fixed rat tooth germs by indirect immunogold staining. Antisera were directed against DPP and against glutaraldehyde-treated DPP and were characterized by immuno-electroblotting. In odontoblasts, DPP was found to be localized in the cisternae of the rough endoplasmic reticulum (RER) and the Golgi apparatus and in Golgi-associated vesicles. Odontoblastic processes were moderately positive for DPP and dentine was intensely labeled on frozen sections of unfixed tissue. Predentine showed a slight immunoreactivity. These results indicate the synthesis of DPP in the RER, its accumulation in the Golgi apparatus and its vesicular transport and secretion via the odontoblastic processes into dentine. The close association of the gold particles with the dentinal collagen fibres makes a role of DPP in linking mineral to collagen conceivable. Matrix vesicles were negative for DPP, suggesting that the protein is not present at the sites of matrix vesicleassociated nucleation. 相似文献
8.
Electrically induced calcium elevation,activation, and parthenogenetic development of bovine oocytes
Philippe Collas Rafael Fissore James M. Robl Eddie J. Sullivan Frank L. Barnes 《Molecular reproduction and development》1993,34(2):212-223
The influence of electrical stimulation on the level of intracellular Ca2+ in bovine oocytes, as well as activation and extent of parthenogenetic development, was investigated. Mature oocytes were electrically stimulated at 29 hr of maturation, and intracellular Ca2+ concentration was determined with the Ca2+ indicator fura-2 dextran (fura-2 D). The Ca2+ response of oocytes to a given electrical pulse was variable. Oocytes responded with either no Ca2+ rise from baseline (≈? 12 nM), a short-duration Ca2+ rise (from 12 nM to 300 nM) that returned to baseline within 2 min of the pulse, or a long-duration Ca2+ rise (from 12 nM to 1,000–2,000 nM) that never returned to baseline during the 8 min period over which the oocytes were monitored. In these oocytes, Ca2+ level returned to baseline when oocytes were removed from 0.30 M mannitol and placed in an ionic medium. Increasing field strength or pulse duration tended to increase the proportion of oocytes displaying a Ca2+ rise, and at 1.0 kVcm?1 for 40 μsec, all oocytes displayed a long-duration Ca2+ elevation. Direct transfer of oocytes from culture medium to mannitol also triggered a Ca2+ rise. Multiple stimulations, either electrical or by transferring to mannitol, produced multiple Ca2+ rises. This mannitol-induced Ca2+ rise could be inhibited by first washing the oocytes in medium containing equal parts of 0.30 M mannitol and phosphate buffered saline (PBS). The level of Ca2+ stimulation affected activation and development of oocytes. Insufficient, or, conversely, excessive Ca2+ stimulation impaired development. Optimum development was obtained with (1) three pulses of 0.2 kVcm?1 for 20 μsec, each pulse 22 min apart, after direct transfer of oocytes from culture medium to mannitol (22% blastocysts) or (2) three pulses of 1.0 kVcm?1 for 20 μsec after transfer of oocytes from culture medium to medium containing equal parts mannitol and PBS, then to mannitol (24% blastocysts). This procedure avoided induction of a Ca2+ rise prior to the pulse. The results indicate that the level of Ca2+ stimulation can be regulated by incubation conditions prior to the pulse and, to some extent, by field strength and pulse duration. The level of electrical stimulation influenced oocyte Ca2+ response, activation, and parthenogenetic development. © 1993 Wiley-Liss, Inc. 相似文献
9.
Effector studies with two isoenzymes (I and IV) of glucose-6-phosphate dehydrogenase (G6PDH) from tobacco suspension culture WR-132 revealed that chlorogenic acid, at 0.4 mM, inhibited both isoenzymes almost 100%, with the inhibition decreasing as the concentration of the acid was reduced. At 0.3 and 0.4 mM, the coumarin glucosides scopolin and esculin were inhibitory, whereas their aglucones scopoletin and esculetin were less inhibitory, and at low concentrations of glucose-6-phosphate (G6P), the latter two were actually stimulatory for G6PDH I. Of the possible effectors studied, only scopoletin and esculetin exhibited a significant activation of G6PDH I under these conditions. However, with G6PDH IV these two effectors do not show the same marked activation at the low G6P concentrations. The phenolic acids, caffeic and ferulic, were less inhibitory than the coumarins tested. The activation of G6PDH I by scopoletin, a compound which accumulates in tobacco under certain stress conditions, gives a possible clue as to the resulting enhanced activity of the hexose monophosphate pathway that has been reported for some plants subjected to stress conditions. 相似文献
10.