全文获取类型
收费全文 | 3185篇 |
免费 | 237篇 |
国内免费 | 1篇 |
出版年
2023年 | 22篇 |
2022年 | 15篇 |
2021年 | 123篇 |
2020年 | 59篇 |
2019年 | 92篇 |
2018年 | 73篇 |
2017年 | 67篇 |
2016年 | 123篇 |
2015年 | 194篇 |
2014年 | 199篇 |
2013年 | 218篇 |
2012年 | 285篇 |
2011年 | 237篇 |
2010年 | 146篇 |
2009年 | 121篇 |
2008年 | 146篇 |
2007年 | 144篇 |
2006年 | 149篇 |
2005年 | 140篇 |
2004年 | 121篇 |
2003年 | 122篇 |
2002年 | 109篇 |
2001年 | 15篇 |
2000年 | 19篇 |
1999年 | 18篇 |
1998年 | 21篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 24篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 21篇 |
1984年 | 23篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1973年 | 11篇 |
1972年 | 8篇 |
1968年 | 8篇 |
1967年 | 7篇 |
1963年 | 9篇 |
1959年 | 6篇 |
排序方式: 共有3423条查询结果,搜索用时 156 毫秒
41.
Summary The rDNA content in Drosophila hydei has been compared in wild-type and in two translocation genotypes possessing only one nucleolus organizer. In highly polyploid salivary glands where rDNA is underreplicated, an independent polytenization of the rDNA occurs resulting in about the same rDNA level in each genotype independently of the number of nucleolous organizers present in the genome. Thus, the situation in the salivary glands of D. hydei is similar to that in D. melanogaster (Spear and Gall 1973).In tetraploid thoracic muscle where rDNA is not underreplicated, the rDNA percentage in the two translocation genotypes is also considerably increased, although the wild-type level is not completely attained. This result shows that rDNA replication is independently controlled even in a non-underreplicating tissue.In larval diploid brain the situation in the two translocation stocks is dissimilar: in one genotype the rDNA content remains unaltered whereas in the other it is increased. This demonstrates for the first time that a gene compensation does occur in a diploid tissue.Supported by a grant from the Deutsche Forschungsgemeinschaft (Ku 282/7) 相似文献
42.
43.
44.
Dane Bicanic Darko Dimitrovski Svjetlana Luterotti Ksenija Marković Charlotte van Twisk Josephus G. Buijnsters Otto Dóka 《Food biophysics》2010,5(1):24-33
The trans-lycopene content of fresh tomato homogenates was assessed by means of the laser photoacoustic spectroscopy, the laser optothermal
window, micro-Raman spectroscopy, and colorimetry; none of these methods require the extraction from the product matrix prior
to the analysis. The wet chemistry method (high-performance liquid chromatography) was used as the absolute quantitative method.
Analytical figures of merit for all methods were compared statistically; best linear correlation was achieved for the chromaticity
index a* and chroma C*. 相似文献
45.
Under the same solution conditions, the apparent weight average sedimentation coefficient, swa, and some quantities obtained from it can be combined with the equilibrium constant or constants, Ki, and the monomer concentration, cI, obtained from sedimentation equilibrium, light scattering or osmotic pressure experiments on the same self-associating solute, so that the individual sedimentation coefficients, si, of the self-associating species, and also the hydrodynamic concentration dependence parameter,g or , can be evaluated. Using two different models for the hydrodynamic concentration parameter, four different methods are presented for the evaluation of the si's. Methods for evaluating g or , once the si's are known, are presented. A method for obtaining the number average sedimentation coefficient, sN, and its application to self-associations is presented. Methods are shown for the evaluation of Z average properties, xzc, as well as number average properties,xNc, of a self-associating solute from its weight average properties, xwc. 相似文献
46.
47.
48.
49.
50.
Maria Tsekoura Evdokia Billis Elias Tsepis Sofia Lampropoulou Charlotte Beaudart Olivier Bruyere Ozlem Yilmaz Gullistan Bahat John Gliatis 《Journal of musculoskeletal & neuronal interactions》2020,20(4):505
Objective:To translate and validate into Greek, the SARC-F questionnaire, a screening tool for sarcopenia.Methods:Questionnaire was back-translated and culturally adapted into Greek according to guidelines proposed by the World Health Organization. A convenience sample of 197 Greek elderly people (71.6±7.8 years, 68.5% women) was recruited, 64 of which were classified as persons at risk of sarcopenia according to the SARC-F. Internal consistency, test-retest and inter-rater reliability were evaluated. Validity (sensitivity, specificity, predictive positive value and predictive negative value) was assessed against the definition from the European Working Group of Sarcopenia in Older People (EWGSOP2), which is considered gold standard. Receiver-operating characteristic analysis was also performed to calculate the area under the curve.Results:SARC-F demonstrated high internal consistency (Cronbach’s alpha of 0.93) and excellent inter-rater and test-retest reliability, with intraclass correlation coefficient (ICC) of 0.91 (95% CI 0.79-0.96), and 0.93 (95% CI 0.91-0.95), respectively. According to the definition of sarcopenia from the EWGSOP2, 53 (26.85) participants were identified as probable sarcopenic and 23 (11.6%) as sarcopenic. Sensitivity of the tool for sarcopenia was 34.4 and specificity was 93.2. Positive predictive values were 26.4 and negative predictive values were 66.6%.Conclusion:Τhe SARC-F was successfully adapted into Greek language. The Greek SARC-F revealed low sensitivity but high specificity with EWGSOP2 sarcopenia definitions, indicating that it can detect with precision the absence of sarcopenia. 相似文献