收费全文 | 694229篇 |
免费 | 70533篇 |
国内免费 | 377篇 |
765139篇 |
2018年 | 7215篇 |
2017年 | 7020篇 |
2016年 | 9340篇 |
2015年 | 11122篇 |
2014年 | 13650篇 |
2013年 | 19733篇 |
2012年 | 22296篇 |
2011年 | 22984篇 |
2010年 | 15711篇 |
2009年 | 14223篇 |
2008年 | 20246篇 |
2007年 | 20960篇 |
2006年 | 19730篇 |
2005年 | 18886篇 |
2004年 | 18726篇 |
2003年 | 17976篇 |
2002年 | 17443篇 |
2001年 | 34320篇 |
2000年 | 34137篇 |
1999年 | 26535篇 |
1998年 | 8276篇 |
1997年 | 8721篇 |
1996年 | 8059篇 |
1995年 | 7427篇 |
1994年 | 7153篇 |
1993年 | 7080篇 |
1992年 | 20855篇 |
1991年 | 20255篇 |
1990年 | 19617篇 |
1989年 | 19273篇 |
1988年 | 17630篇 |
1987年 | 16474篇 |
1986年 | 15286篇 |
1985年 | 15209篇 |
1984年 | 12377篇 |
1983年 | 10362篇 |
1982年 | 7540篇 |
1981年 | 6694篇 |
1980年 | 6429篇 |
1979年 | 11467篇 |
1978年 | 8777篇 |
1977年 | 8070篇 |
1976年 | 7482篇 |
1975年 | 8463篇 |
1974年 | 9184篇 |
1973年 | 8972篇 |
1972年 | 8116篇 |
1971年 | 7454篇 |
1970年 | 6457篇 |
1969年 | 6191篇 |
Histological examination of healing lesions at different stages showed that there was a primary invasion of cuboidal epithelium over the collagen scar followed by a phase of disorganized proliferation which eventually organized itself into normal epithelium. Melanocytes were very obvious in the dermis of healing lesions. 相似文献
On the taxonomy of Rhodopseudomonas palustris
Summary Strains of Rhodopseudomonas palustris isolated from different habitats were compared with respect to their taxonomic features. All strains grew very well on formiate, acetate, propionate, butyrate, aspartate, inositol, ethanol, fructose, and p-amino-benzoate, respectively, as single carbon source. Most of the strains were able to use benzoic acid or glucose, too. But alanine was not found to be a good substrate. The maxima of the bacteriochlorophyll in-vivo-absorption spectra were estimated to be 376, 589, 802–805, and 858–875 nm. The shift of the infrared peak in the different strains is loosely correlated with the change of the carotenoid in vivo spectrum, the maxima of which were measured to be 470–480 nm (shoulder) 495–505 nm, and 520–545 nm (shoulder). Antisera were prepared against the strains 1e5 and 11/1. It was demonstrated that these antisera were directed against the lipopolysaccharides (O-antigen) of these bacteria. The antigen of 1e5 does not cross react with the antigen of 11/1. Strain 1e5 is the only one of 17 strains tested which is sensitive to the bacteriophage Rp1. The antigen of this strain cross reacted only with the antigen of strain K1. In contrast, the antigen of strain 11/1 cross reacted in some degree with most of the tested strains of Rps. palustris. No or very weak cross reaction was observed between the antigens of Rps. palustris (1e5, 11/1) and Rps. capsulata, Rps. spheroides, or R. rubrum, respectively. In contrast to 11/1 only heat-killed cells of strain 1e5 were agglutinated by anti-1e5.
Im Text verwendete Abkürzungen LPS Lipopolysaccharid - R Rhodospirillum - Rps. Rhodopseudomonas - i.m. intramuskulär - s.c. subcutan - i.v. intravenös 相似文献
Extracting biomedical information from large metabolomic datasets by multivariate data analysis is of considerable complexity. Common challenges include among others screening for differentially produced metabolites, estimation of fold changes, and sample classification. Prior to these analysis steps, it is important to minimize contributions from unwanted biases and experimental variance. This is the goal of data preprocessing. In this work, different data normalization methods were compared systematically employing two different datasets generated by means of nuclear magnetic resonance (NMR) spectroscopy. To this end, two different types of normalization methods were used, one aiming to remove unwanted sample-to-sample variation while the other adjusts the variance of the different metabolites by variable scaling and variance stabilization methods. The impact of all methods tested on sample classification was evaluated on urinary NMR fingerprints obtained from healthy volunteers and patients suffering from autosomal polycystic kidney disease (ADPKD). Performance in terms of screening for differentially produced metabolites was investigated on a dataset following a Latin-square design, where varied amounts of 8 different metabolites were spiked into a human urine matrix while keeping the total spike-in amount constant. In addition, specific tests were conducted to systematically investigate the influence of the different preprocessing methods on the structure of the analyzed data. In conclusion, preprocessing methods originally developed for DNA microarray analysis, in particular, Quantile and Cubic-Spline Normalization, performed best in reducing bias, accurately detecting fold changes, and classifying samples.
相似文献