全文获取类型
收费全文 | 723篇 |
免费 | 72篇 |
国内免费 | 1篇 |
专业分类
796篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 12篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 12篇 |
2015年 | 15篇 |
2014年 | 33篇 |
2013年 | 32篇 |
2012年 | 51篇 |
2011年 | 45篇 |
2010年 | 29篇 |
2009年 | 22篇 |
2008年 | 32篇 |
2007年 | 24篇 |
2006年 | 37篇 |
2005年 | 25篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 21篇 |
2001年 | 23篇 |
2000年 | 22篇 |
1999年 | 21篇 |
1998年 | 22篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 19篇 |
1991年 | 29篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 10篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有796条查询结果,搜索用时 0 毫秒
51.
Magnus Kjaergaard Ann‒Beth Nørholm Ruth Hendus‒Altenburger Stine F. Pedersen Flemming M. Poulsen Birthe B. Kragelund 《Protein science : a publication of the Protein Society》2010,19(8):1555-1564
Structural characterization of intrinsically disordered proteins (IDPs) is mandatory for deciphering their potential unique physical and biological properties. A large number of circular dichroism (CD) studies have demonstrated that a structural change takes place in IDPs with increasing temperature, which most likely reflects formation of transient α-helices or loss of polyproline II (PPII) content. Using three IDPs, ACTR, NHE1, and Spd1, we show that the temperature-induced structural change is common among IDPs and is accompanied by a contraction of the conformational ensemble. This phenomenon was explored at residue resolution by multidimensional NMR spectroscopy. Intrinsic chemical shift referencing allowed us to identify regions of transiently formed helices and their temperature-dependent changes in helicity. All helical regions were found to lose rather than gain helical structures with increasing temperature, and accordingly these were not responsible for the change in the CD spectra. In contrast, the nonhelical regions exhibited a general temperature-dependent structural change that was independent of long-range interactions. The temperature-dependent CD spectroscopic signature of IDPs that has been amply documented can be rationalized to represent redistribution of the statistical coil involving a general loss of PPII conformations. 相似文献
52.
Mette Kristensen Francesco Savorani Gitte Ravn-Haren Morten Poulsen Jaroslaw Markowski Flemming H. Larsen Lars O. Dragsted Søren B. Engelsen 《Metabolomics : Official journal of the Metabolomic Society》2010,6(1):129-136
Risk of cardiovascular disease is related to cholesterol distribution in different lipoprotein fractions. Lipoproteins in
rodent model studies can only reliably be measured by time- and plasma-consuming fractionation. An alternative method to measure
cholesterol distribution in the lipoprotein fractions in rat plasma is presented in this paper. Plasma from two rat studies
(n = 68) was used in determining the lipoprotein profile by an established ultracentrifugation method and proton nuclear magnetic
resonance (NMR) spectra of replicate samples was obtained. From the ultracentrifugation reference data and the NMR spectra,
an interval partial least-square (iPLS) regression model to predict the amount of cholesterol in the different lipoprotein
fractions was developed. The relative errors of the prediction models were between 12 and 33% and had correlation coefficients
(r) between 0.96 and 0.84. The models were tested with an independent test set giving prediction errors between 19 and 46%
and r between 0.96 and 0.76. Prediction of High, Low and Very Low Density Lipoprotein (HDL, LDL and VLDL) and total cholesterol
was conducted in a study where rats had been supplemented with two doses of air-dried apple-powder. No significant difference
in LDL, VLDL and total cholesterol was observed between the groups. The high apple-powder (20%) group had significantly lower
HDL cholesterol (11%, P = 0.0452) than the control group. It is concluded that the iPLS approach yielded excellent regression models and thus univocal
established chemometric analysis of NMR spectra of rat plasma as a strong and efficient way to quantify lipoprotein fractions
in rat studies. 相似文献
53.
Irina Borodina Bettina M Jensen Ib Søndergaard Lars K Poulsen 《Microbial cell factories》2010,9(1):74
Background
Yeast surface display is a technique, where the proteins of interest are expressed as fusions with yeast surface proteins and thus remain attached to the yeast cell wall after expression. Our purpose was to study whether allergens expressed on the cell surface of baker's yeast Saccharomyces cerevisiae preserve their native allergenic properties and whether the yeast native surface glycoproteins interfere with IgE binding. We chose to use the major allergens from the common wasp Vespula vulgaris venom: phospholipase A1, hyaluronidase and antigen 5 as the model. 相似文献54.
55.
Accurate measurements of coupling constants from two-dimensional nuclear magnetic resonance spectra of proteins and determination of phi-angles 总被引:6,自引:0,他引:6
A new and simple method to measure 3JHNH alpha coupling constants of proteins by adding and subtracting traces from corresponding two-dimensional nuclear Overhauser enhanced spectroscopy and two-dimensional correlated spectroscopy cross peaks after scaling is proposed. The optimal scaling for the addition and the subtraction of the two traces is obtained by minimizing an error function. The method was proven to give accurate and precise measurements of coupling constants when tested with a series of simulated spectra. The accuracy of the method was better than 0.1 Hz for all test cases including the limiting case of J = 2.0 Hz and line-width = 11.0 Hz. The accuracy of the method was better than 0.1 Hz for all test cases including The 3JHNH alpha coupling constants were measured in two-dimensional nuclear magnetic resonance spectra of the two proteins barley serine proteinase inhibitor (CI-2) and the bacterial ribonuclease (barnase) of Bacillus amyloliquefaciens. The experimentally measured coupling constants were used to calculate the constants in a Karplus equation to be: 3JHNH alpha = 6.7 cos2(phi-60) -1.3 cos(phi-60) +1.5. These constants are in good accordance with those obtained for basic pancreatic trypsin inhibitor (BPTI). In addition, special emphasis is given to the measurements of positive phi-angles, and to the contribution of molecular dynamics on the apparent coupling constants. 相似文献
56.
Coexpression of Notch3 and Rgs5 in the pericyte-vascular smooth muscle cell axis in response to pulp injury 总被引:1,自引:0,他引:1
Lovschall H Mitsiadis TA Poulsen K Jensen KH Kjeldsen AL 《The International journal of developmental biology》2007,51(8):715-721
Recent studies have shown that the pulp of human teeth contains a population of cells with stem cell properties and it has been suggested that these cells originate from pericytes. Molecules of the Notch signaling pathway regulate stem cell fate specification, while Rgs5 represents an excellent marker for pericytes. Pathological conditions such as dental trauma and carious lesion stimulate pulp stem cells to elaborate reparative dentin. Previous studies have shown that genes involved in the Notch pathway are activated in response to pulp injury in rodent and humans. To demonstrate the importance of pericytes as a source of stem cells during dental repair, we have studied Rgs5 and Notch3 mRNA expression by in situ hybridization in developing, adult intact and injured rodent teeth. Furthermore, we have examined the distribution of Notch3 protein in carious and injured human teeth using immunohistochemistry. Overlapping expression patterns of Rgs5 and Notch3 were observed during rodent tooth development as well as immediately after injury. Both genes were expressed in vascular structures during development and in perivascular and single capillary cells of injured teeth. However, the expression patterns of Rgs5 and Notch3 were different during tooth repair, with relatively extensive Rgs5 expression along the pericyte-vascular smooth muscle cell axis in central pulp arterioles. These results show co-expression of Rgs5 and Notch3 in pericytes of developing and injured teeth and furthermore indicate the importance of vascular-derived stem cells during pulp healing. 相似文献
57.
The observation of oscillations in the concentrations of NADH and other intermediates in glycolysis in dense yeast cell suspensions is generally believed to be the result of synchronization of such oscillations between individual cells. The synchrony is believed to be a property of cell density and the question is: does metabolism in each individual yeast cell continue to oscillate, but out of phase, in the absence of synchronization? Here we have used high-sensitivity fluorescence microscopy to measure NADH in single isolated yeast cells under conditions where we observe oscillations of glycolysis in dense cell suspensions. However, we have not been able to detect intracellular oscillations in NADH in these isolated cells, which cannot synchronize their metabolism with other cells. However, addition of acetaldehyde to a single cell as pulses with a frequency similar to the oscillations in dense cell suspensions will induce oscillations in that cell. Ethanol, another product of glycolysis, which has been proposed as a synchronizing agent of glycolysis in cells, was not able to induce oscillations when added as pulses. The experiments support the notion that the intracellular oscillations are associated with the cell density of the yeast cell suspension and mediated by acetaldehyde and perhaps also other substances. 相似文献
58.
The authors describe a homogeneous, sensitive, and rapid bead-based sandwich immunoassay with a broad analytical range for quantifying insulin in human plasma. The assay was performed as a 2-step reaction by incubating the sample with a mixture of biotinylated anti-insulin antibody and beads covalently coated with anti-insulin antibody for 1 h. This was followed by incubation with beads covalently coated with streptavidin for 30 min. After the incubation steps, light generated from a chemiluminescent reaction within the beads was quantitated. The assay was run in 384-well plates with a sample volume of 5 microL. The analytical range extended from 1 to 10,000 pM. Intra-assay precision (% coefficient of variation) ranged from 1.9% to 3.8% for various insulin concentrations. Interassay precision ranged from 4.6% to 7.3%. Assay detection limit was 0.3 pM. There was no interference from moderate hemolysis (with hemoglobin up to 375 mg/dL), bilirubin (up to at least 50 mg/dL), triglyceride (up to at least 1000 mg/dL), biotin (up to at least 7.7 ng/mL), or ascorbic acid (up to 100 mg/dL). However, gross hemolysis did affect the assay. Comparable results were obtained for plasma (ethylenediamine tetra-acetic acid, citrate, and heparin treated) and serum. The correlation with enzyme-linked immunosorbent assay (ELISA) was good (y = 1.25x + 1.19, R(2) = 0.98). This method is convenient and represents an alternative to ELISA. 相似文献
59.
The gestation length (GL) of Tenrecs (Tenrecinae, Afrotheria) is still uncertain. This lack of knowledge also applies to the lesser hedgehog tenrec, Echinops telfairi, the species most commonly bred and maintained in captivity. The animals used in this study were held under controlled conditions (light, temperature and humidity). In order to determine the GL, groups of female tenrecs were subjected to various mating procedures followed by isolation periods of different lengths. A total of n=249 pregnancies were analysed and the number of offspring per litter was 3.29+/-0.09. The length of gestation could be determined in n=199 pregnancies and a mean GL of 67.53+/-0.36 days was calculated. Initial attempts with isolation periods of less than 16 days did not allow to accurately define the GL. Experiments with longer isolation periods and females subjected to only one mating procedure (n=10) revealed a variation in the GLs of 57-79 days. However, in one female a GL of only 50 days was also observed indicating an even greater range in GL variation. There was a statistically significant tendency for shorter GLs in the animals that conceived later in the mating season, but no statistical evidence was found that age, parity or litter size played an essential role in determining the GL. In conclusion, an unexpected high variability in gestation length in E. telfairi was demonstrated although the study animals were kept under controlled environmental conditions. The factors and mechanisms regulating this high intra-species variability in gestation length need further investigations. 相似文献
60.
CAF01 potentiates immune responses and efficacy of an inactivated influenza vaccine in ferrets 总被引:1,自引:0,他引:1
Martel CJ Agger EM Poulsen JJ Hammer Jensen T Andresen L Christensen D Nielsen LP Blixenkrone-Møller M Andersen P Aasted B 《PloS one》2011,6(8):e22891
Trivalent inactivated vaccines (TIV) against influenza are given to 350 million people every year. Most of these are non-adjuvanted vaccines whose immunogenicity and protective efficacy are considered suboptimal. Commercially available non-adjuvanted TIV are known to elicit mainly a humoral immune response, whereas the induction of cell-mediated immune responses is negligible. Recently, a cationic liposomal adjuvant (dimethyldioctadecylammonium/trehalose 6,6'-dibehenate, CAF01) was developed. CAF01 has proven to enhance both humoral and cell-mediated immune responses to a number of different experimental vaccine candidates. In this study, we compared the immune responses in ferrets to a commercially available TIV with the responses to the same vaccine mixed with the CAF01 adjuvant. Two recently circulating H1N1 viruses were used as challenge to test the vaccine efficacy. CAF01 improved the immunogenicity of the vaccine, with increased influenza-specific IgA and IgG levels. Additionally, CAF01 promoted cellular-mediated immunity as indicated by interferon-gamma expressing lymphocytes, measured by flow cytometry. CAF01 also enhanced the protection conferred by the vaccine by reducing the viral load measured in nasal washes by RT-PCR. Finally, CAF01 allowed for dose-reduction and led to higher levels of protection compared to TIV adjuvanted with a squalene emulsion. The data obtained in this human-relevant challenge model supports the potential of CAF01 in future influenza vaccines. 相似文献