全文获取类型
收费全文 | 1628篇 |
免费 | 141篇 |
国内免费 | 2篇 |
专业分类
1771篇 |
出版年
2022年 | 14篇 |
2021年 | 35篇 |
2020年 | 15篇 |
2019年 | 22篇 |
2018年 | 31篇 |
2017年 | 28篇 |
2016年 | 40篇 |
2015年 | 69篇 |
2014年 | 79篇 |
2013年 | 99篇 |
2012年 | 121篇 |
2011年 | 113篇 |
2010年 | 70篇 |
2009年 | 63篇 |
2008年 | 86篇 |
2007年 | 90篇 |
2006年 | 81篇 |
2005年 | 70篇 |
2004年 | 74篇 |
2003年 | 72篇 |
2002年 | 71篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 17篇 |
1998年 | 24篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 20篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1974年 | 7篇 |
1968年 | 6篇 |
1964年 | 6篇 |
排序方式: 共有1771条查询结果,搜索用时 0 毫秒
191.
Marian Kacerovsky Peter Celec Barbora Vlkova Kristin Skogstrand David M. Hougaard Teresa Cobo Bo Jacobsson 《PloS one》2013,8(3)
Objective
This study aimed to evaluate the amniotic fluid protein profiles and the intensity of intraamniotic inflammatory response to Ureaplasma spp. and other bacteria, using the multiplex xMAP technology.Methods
A retrospective cohort study was undertaken in the Department of Obstetrics and Gynecology, University Hospital Hradec Kralove, Czech Republic. A total of 145 pregnant women with preterm prelabor rupture of membranes between gestational age 24+0 and 36+6 weeks were included in the study. Amniocenteses were performed. The presence of Ureaplasma spp. and other bacteria was evaluated using 16S rRNA gene sequencing. The levels of specific proteins were determined using multiplex xMAP technology.Results
The presence of Ureaplasma spp. and other bacteria in the amniotic fluid was associated with increased levels of interleukin (IL)-6, IL-8, IL-10, brain-derived neurotropic factor, granulocyte macrophage colony stimulating factor, monocyte chemotactic protein-1, macrophage inflammatory protein-1, and matrix metalloproteinasis-9. Ureaplasma spp. were also associated with increased levels of neurotropin-3 and triggering receptor expressed on myeloid cells-1.Conclusions
The presence of Ureaplasma spp. in the amniotic fluid is associated with a slightly different protein profile of inflammatory response, but the intensity of inflammatory response to Ureaplasma spp. is comparable with the inflammatory response to other bacteria. 相似文献192.
193.
Three forms of cytochrome c oxidase, fully oxidized CcO (CcO-O), oxidized CcO complexed with cyanide (CcO.CN), and mixed valence CcO, in which both heme a(3) and Cu(B) are reduced and stabilized by carbon monoxide (MV.CO), were investigated by optical spectroscopy, MCD, and stopped-flow for the pH sensitivity of spectral features. In the pH range between pH 5.7 and 9.0, both heme a and heme a(3) in CcO-O interact with a single protolytic group. From the variation of the position of the Soret peak with changes in pH, a pK(a) of 6.6 +/- 0.2 was determined for this group. The pH sensitivity of heme a(3) is lost in the CcO.CN complex, and only heme a responds to pH changes. In MV.CO the spectra of both hemes are almost independent of pH between 5.7 and 11.0. The stoichiometry of proton uptake in the conversion of CcO-O both to MV.CO and to fully reduced CcO was determined between pH 5.8 and pH 8.2. Formation of MV.CO from CcO-O was accompanied by the uptake of approximately two protons, and this value was almost independent of pH. Full reduction of oxidized CcO was associated with the uptake of approximately 2 H(+) at basic pH, and this value increases with decreasing pH. On the basis of these proton uptake measurements, it is concluded that the pK(a) of the group is independent of the redox state of CcO. It is suggested that Glu60 of subunit II, located at the entrance of the proton conducting K-channel, is the protolytic residue that interacts with both hemes through a hydrogen-bonding network. 相似文献
194.
An interaction between cytochrome a in oxidized cytochrome c oxidase (CcO) and anions has been characterized by EPR spectroscopy. Those anions that affect the EPR g = 3 signal of cytochrome a can be divided into two groups. One group consists of halides (Cl-, Br-, and I-) and induces an upfield shift of the g = 3 signal. Nitrogen-containing anions (CN-, NO2-, N3-, NO3-) are in the second group and shift the g = 3 signal downfield. The shifts in the EPR spectrum of CcO are unrelated to ligand binding to the binuclear center. The binding properties of one representative from each group, azide and chloride, were characterized in detail. The dependence of the shift on chloride concentration is consistent with a single binding site in the isolated oxidized enzyme with a Kd of approximately 3 mm. In mitochondria, the apparent Kd was found to be about four times larger than that of the isolated enzyme. The data indicate it is the chloride anion that is bound to CcO, and there is a hydrophilic size-selective access channel to this site from the cytosolic side of the mitochondrial membrane. An observed competition between azide and chloride is interpreted by azide binding to three sites: two that are apparent in the x-ray structure plus the chloride-binding site. It is suggested that either Mg2+ or Arg-438/Arg-439 is the chloride-binding site, and a mechanism for the ligand-induced shift of the g = 3 signal is proposed. 相似文献
195.
196.
197.
198.
Sean V. Murphy Rebecca Lim Philip Heraud Marian Cholewa Mark Le Gros Martin D. de Jonge Daryl L. Howard David Paterson Courtney McDonald Anthony Atala Graham Jenkin Euan M. Wallace 《PloS one》2012,7(9)
Cystic fibrosis, an autosomal recessive disorder caused by a mutation in a gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), remains a leading cause of childhood respiratory morbidity and mortality. The respiratory consequences of cystic fibrosis include the generation of thick, tenacious mucus that impairs lung clearance, predisposing the individual to repeated and persistent infections, progressive lung damage and shortened lifespan. Currently there is no cure for cystic fibrosis. With this in mind, we investigated the ability of human amnion epithelial cells (hAECs) to express functional CFTR. We found that hAECs formed 3-dimensional structures and expressed the CFTR gene and protein after culture in Small Airway Growth Medium (SAGM). We also observed a polarized CFTR distribution on the membrane of hAECs cultured in SAGM, similar to that observed in polarized airway cells in vivo. Further, hAECs induced to express CFTR possessed functional iodide/chloride (I−/Cl−) ion channels that were inhibited by the CFTR-inhibitor CFTR-172, indicating the presence of functional CFTR ion channels. These data suggest that hAECs may be a promising source for the development of a cellular therapy for cystic fibrosis. 相似文献
199.
200.
Gladys E. Deibler Russell E. Martenson Henry C. Krutzsch† Marian W. Kies 《Journal of neurochemistry》1984,43(1):100-105
This paper proposes a tentative amino acid sequence of guinea pig myelin basic protein obtained by comparison of peptide fragments of the guinea pig and bovine proteins. Analyses of the tryptic peptides confirmed the known sequence differences in the NH2-terminal half of the molecule and showed that in the COOH-terminal half of the guinea pig protein Ser131 was missing, Ala136 - His137 was deleted, Leu140 was replaced by Phe, and an extra Ala was inserted somewhere within sequence 142-151 (tryptic peptide T23 ). Sequence determination of guinea pig tryptic peptides corresponding to residues 130-134 ( T20 ), 135-138 ( T21 ), and 142-151 ( T23 ) of the bovine protein confirmed the above sequence changes and placed the extra Ala between Gly142 and His143 . The sequence of the region corresponding to bovine residues 130-143 is thus Ala-Asp-Tyr-Lys-Ser-Lys-Gly-Phe-Lys-Gly-Ala-His. No species differences were observed in the amino acid compositions of the remaining tryptic peptides obtained from the COOH-terminal half of the molecule. Based upon these results, the guinea pig basic protein contains 167 amino acid residues and has a molecular weight of 18,256. 相似文献