全文获取类型
收费全文 | 1397篇 |
免费 | 130篇 |
国内免费 | 2篇 |
专业分类
1529篇 |
出版年
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 33篇 |
2020年 | 26篇 |
2019年 | 36篇 |
2018年 | 47篇 |
2017年 | 28篇 |
2016年 | 43篇 |
2015年 | 81篇 |
2014年 | 75篇 |
2013年 | 100篇 |
2012年 | 91篇 |
2011年 | 123篇 |
2010年 | 73篇 |
2009年 | 62篇 |
2008年 | 79篇 |
2007年 | 110篇 |
2006年 | 83篇 |
2005年 | 65篇 |
2004年 | 84篇 |
2003年 | 58篇 |
2002年 | 60篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 18篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1958年 | 2篇 |
1957年 | 3篇 |
1954年 | 1篇 |
1951年 | 1篇 |
1934年 | 1篇 |
1930年 | 1篇 |
1927年 | 1篇 |
1924年 | 2篇 |
排序方式: 共有1529条查询结果,搜索用时 0 毫秒
951.
Dobard C Sharma S Martin A Pau CP Holder A Kuklenyik Z Lipscomb J Hanson DL Smith J Novembre FJ García-Lerma JG Heneine W 《Journal of virology》2012,86(2):718-725
A vaginal gel containing 1% tenofovir (TFV) was found to be safe and effective in reducing HIV infection in women when used pericoitally. Because of the long intracellular half-life of TFV and high drug exposure in vaginal tissues, we hypothesized that a vaginal gel containing TFV may provide long-lasting protection. Here, we performed delayed-challenge experiments and showed that vaginal 1% TFV gel protected 4/6 macaques against vaginal simian-human immunodeficiency virus (SHIV) exposures occurring 3 days after gel application, demonstrating long-lasting protection. Despite continued gel dosing postinfection, neither breakthrough infection had evidence of drug resistance by ultrasensitive testing of SHIV in plasma and vaginal lavage. Analysis of the active intracellular tenofovir diphosphate (TFV-DP) in vaginal lymphocytes collected 4 h to 3 days after gel dosing persistently showed high TFV-DP levels (median, 1,810 fmol/10(6) cells) between 4 and 24 h that exceed the 95% inhibitory concentration (IC(95)), reflecting rapid accumulation and long persistence. In contrast to those in peripheral blood mononuclear cells (PBMCs) following oral dosing, TFV-DP levels in vaginal lymphocytes decreased approximately 7-fold by 3 days, exhibiting a much higher rate of decay. We observed a strong correlation between intracellular TFV-DP in vaginal lymphocytes, in vitro antiviral activity, and in vivo protection, suggesting that TFV-DP above the in vitro IC(95) in vaginal lymphocytes is a good predictor of high efficacy. Data from this model reveal an extended window of protection by TFV gel that supports coitus-independent use. The identification of protective TFV-DP concentrations in vaginal lymphocytes may facilitate the evaluation of improved delivery methods of topical TFV and inform clinical studies. 相似文献
952.
Hygromycin resistance as an efficient selectable marker for wheat stable transformation 总被引:23,自引:0,他引:23
Juan Pablo A. Ortiz Martín I. Reggiardo Ricardo A. Ravizzini Silva G. Altabe Gerardo D. L. Cervigni Marcelo A. Spitteler Mónica M. Morata Fernando E. Elias Rubén H. Vallejos 《Plant cell reports》1996,15(12):877-881
Summary A highly efficient method for stable wheat transformation using hygromycin resistance as a selectable marker is described. Young embryogenic calli growing from immature wheat embryos were transformed using a gunpowder-driven microparticle accelerator. Transgenic wheat plants were determined by PCR amplification of transgene fragments and confirmed by Southern hybridization, activity of the transgene expression and by analysis of the progeny. The hpt gene was as good as or a better selectable marker than the bar gene with an average efficiency (number of transgenic plants relative to the number of bombarded calli) of 5.5% compared with 2.6% for the bar gene. 相似文献
953.
Vincent De Guire Maxime Caron Nicolas Scott Catherine Ménard Marie-France Gaumont-Leclerc Pascal Chartrand Fran?ois Major Gerardo Ferbeyre 《Nucleic acids research》2010,38(13):e140
MicroRNAs (miRNAs) are naturally occurring small RNAs that regulate the expression of several genes. MiRNAs’ targeting rules are based on sequence complementarity between their mature products and targeted genes’ mRNAs. Based on our present understanding of those rules, we developed an algorithm to design artificial miRNAs to target simultaneously a set of predetermined genes. To validate in silico our algorithm, we tested different sets of genes known to be targeted by a single miRNA. The algorithm finds the seed of the corresponding miRNA among the solutions, which also include the seeds of new artificial miRNA sequences potentially capable of targeting these genes as well. We also validated the functionality of some artificial miRNAs designed to target simultaneously members of the E2F family. These artificial miRNAs reproduced the effects of E2Fs inhibition in both normal human fibroblasts and prostate cancer cells where they inhibited cell proliferation and induced cellular senescence. We conclude that the current miRNA targeting rules based on the seed sequence work to design multiple-target artificial miRNAs. This approach may find applications in both research and therapeutics. 相似文献
954.
Fulciniti F La Vecchia F Staiano M Tatangelo F De Rosa V Rocco G La Rocca A Botti G 《Acta cytologica》2007,51(2):227-230
BACKGROUND: Spindle cell neuroendocrine carcinomas of the lung may be frequently observed on fine needle cytology (FNC) samples and often pose stimulating differential diagnostic problems. CASE: The cytopathologic findings from FNC performed on a long-standing coin lesion of the lung in a 54-year-old woman were analyzed in view of the data and long clinical history. CONCLUSION: A final diagnosis of low grade spindle cell neuroendocrine carcinoma was reached by combining cytopathologic and immunocytochemical information. The main lesions considered in the differential diagnosis were intrapulmonary inflammatory myofibroblastic tumor (fibrohistiocytic variant) and spindle cell thymoma. 相似文献
955.
Study of the interactions between lysozyme and a fully-fluorinated surfactant in aqueous solution at different surfactant-protein ratios 总被引:2,自引:0,他引:2
Ruso JM González-Pérez A Prieto G Sarmiento F 《International journal of biological macromolecules》2003,33(1-3):67-73
The interactions of a fluorinated surfactant, sodium perfluorooctanoate, with lysozyme, have been investigated by a combination of UV absorbance, electrical conductivity and dynamic light scattering to detect and to characterize the conformational transitions of lysozyme. By using difference spectroscopy, the transition was followed as a function of surfactant concentration, and the data were analyzed to obtain the Gibbs energy of the transition in water (DeltaGw(o)) and in a hydrophobic environment (DeltaGh(o)) for saturated protein-surfactant complexes. Electrical conductivity was used to determine the critical micelle concentration of the surfactant in the presence of different lysozyme concentration. From these results, the average number of surfactant monomer per protein molecule was calculated. Finally, dynamic light scattering show that only changes in the secondary structure of the protein can be observed. 相似文献
956.
Tania Escalante Juan J. Morrone Gerardo Rodríguez‐Tapia 《Biological journal of the Linnean Society. Linnean Society of London》2013,110(3):485-499
Since the 19th Century, two regions have been recognized for North American mammals, which overlap in Mexico. The Nearctic region corresponds to the northern areas and the Neotropical region corresponds to the southern ones. There are no recent regionalizations for these regions under the criterion of endemism. In the present study, we integrate two methods to regionalize North America, using species distribution models of mammals: endemicity analysis (EA) and parsimony analysis of endemicity (PAE). EA was used to obtain areas of endemism and PAE was used to hierarchize them. We found 76 consensus areas from 329 sets classified in 146 cladograms, and the strict consensus cladogram shows a basal polytomy with 14 areas and 16 clades. The final regionalization recognizes two regions (Nearctic and Neotropical) and a transition zone (Mexican Transition Zone), six subregions (Canadian, Alleghanian, Californian‐Rocky Mountain, Pacific Central America, Mexican Gulf‐Central America, and Central America), two dominions (Californian and Rocky Mountain), and 23 provinces. Our analysis show that North America is probably more complex than previously assumed. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 485–499. 相似文献
957.
958.
959.
960.