全文获取类型
收费全文 | 56942篇 |
免费 | 4157篇 |
国内免费 | 11篇 |
出版年
2023年 | 388篇 |
2022年 | 527篇 |
2021年 | 1070篇 |
2020年 | 901篇 |
2019年 | 991篇 |
2018年 | 1613篇 |
2017年 | 1413篇 |
2016年 | 2108篇 |
2015年 | 2962篇 |
2014年 | 3034篇 |
2013年 | 3874篇 |
2012年 | 4852篇 |
2011年 | 4558篇 |
2010年 | 2630篇 |
2009年 | 2126篇 |
2008年 | 3430篇 |
2007年 | 3310篇 |
2006年 | 3132篇 |
2005年 | 2670篇 |
2004年 | 2618篇 |
2003年 | 2385篇 |
2002年 | 2180篇 |
2001年 | 1130篇 |
2000年 | 1204篇 |
1999年 | 762篇 |
1998年 | 392篇 |
1997年 | 255篇 |
1996年 | 268篇 |
1995年 | 271篇 |
1994年 | 243篇 |
1993年 | 230篇 |
1992年 | 328篇 |
1991年 | 266篇 |
1990年 | 242篇 |
1989年 | 227篇 |
1988年 | 188篇 |
1987年 | 173篇 |
1986年 | 156篇 |
1985年 | 169篇 |
1984年 | 196篇 |
1983年 | 118篇 |
1982年 | 131篇 |
1981年 | 106篇 |
1980年 | 98篇 |
1979年 | 123篇 |
1978年 | 93篇 |
1976年 | 102篇 |
1975年 | 102篇 |
1974年 | 82篇 |
1973年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
51.
52.
Fátima H. Vaz Patrícia M. Machado Rita D. Brand?o Cátia T. Laranjeira Joana S. Eugénio Aires H. Fernandes Saudade P. André 《The journal of histochemistry and cytochemistry》2007,55(11):1105-1113
Only 20-25% of families screened for BRCA1/2 mutations are found positive. Because only a positive result is informative, we studied the role of BRCA1/2 immunohistochemistry as an additional method for patient selection. From 53 high-risk-affected probands, 18 (34%) had available paraffin blocks of their tumors and were selected for this study. Mutation screening was done by conformation-sensitive gel electrophoresis and multiplex ligation-dependent probe amplification. For immunohistochemistry, 21 neoplastic specimens (15 breast carcinomas, 5 ovary neoplasms, and 1 rectal adenocarcinoma) were analyzed with BRCA1 (monoclonal antibody, Ab-1, oncogene) and BRCA2 (polyclonal antibody, Ab-2, oncogene) antibodies. Absence of the BRCA1 protein was confirmed in negative tumors by Western blotting. Seven patients were positive for BRCA1/2 mutations: 5 for BRCA1 and 2 for BRCA2. Four out of five positive patients had tumors negative for BRCA1 immunostaining, and the remaining 13 BRCA1-negative patients had positive BRCA1 immunostaining in all tumor samples. Sensitivity to predict for BRCA1 mutation carriers was 80%, and specificity was 100%, with a positive predictive value of 100% and a negative predictive value of 93%. This correlation was statistically significant (p=0.001). No correlation was observed for BRCA2. If larger studies confirm these results, high-risk patients with BRCA1-negative tumors should be screened first for this gene. 相似文献
53.
Blanco Pablo J. Müller Lucas O. Watanabe Sansuke M. Feijóo Raúl A. 《Biomechanics and modeling in mechanobiology》2020,19(5):1663-1678
Biomechanics and Modeling in Mechanobiology - The goal of this work is to assess the impact of vascular anatomy definition degree in the predictions of blood flow models of the arterial network. To... 相似文献
54.
55.
Hervé Seitz 《Current biology : CB》2010,20(3):R108-R110
56.
Chromosome characterization in Acestrorhynchinae and Cynopotaminae (Pisces, Characidae) 总被引:1,自引:0,他引:1
The karyotypes of six species of Acestrorhynchinae ( Acestrorhynchus alus, A. lacustris, Oligosarcus hepsetus, O. jenynsii, O. macrolepis and O. pinloi ) and of one species of Cynopotaminae ( Galeocharax knerii ) were studied. The six Acestrorhynchinae species have 2 n = 50, while Galeocharax knerii has 2 n = 52 chromosomes. Some chromosomal characteristics were detected which permit establishing some karyotypic relationships among the different species investigated. Thus, among the Acestrorhynchinae, the four Oligosarcus species are relatively more related to one another than the two Acestrorhynchus species, at least with respect to the cytogenetic data considered. On the basis of the methods used, no sex chromosome heteromorphism was detected in the species for which a comparative study between male and female specimens was possible. 相似文献
57.
Jos L. Holuby 《Plant Systematics and Evolution》1879,29(1):33-34
Ohne Zusammenfassung 相似文献
58.
59.
How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls'' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates. 相似文献