全文获取类型
收费全文 | 6353篇 |
免费 | 594篇 |
国内免费 | 3篇 |
出版年
2023年 | 26篇 |
2022年 | 44篇 |
2021年 | 123篇 |
2020年 | 66篇 |
2019年 | 86篇 |
2018年 | 109篇 |
2017年 | 100篇 |
2016年 | 165篇 |
2015年 | 282篇 |
2014年 | 325篇 |
2013年 | 405篇 |
2012年 | 436篇 |
2011年 | 476篇 |
2010年 | 285篇 |
2009年 | 268篇 |
2008年 | 393篇 |
2007年 | 381篇 |
2006年 | 318篇 |
2005年 | 337篇 |
2004年 | 312篇 |
2003年 | 319篇 |
2002年 | 311篇 |
2001年 | 49篇 |
2000年 | 34篇 |
1999年 | 53篇 |
1998年 | 77篇 |
1997年 | 50篇 |
1996年 | 54篇 |
1995年 | 40篇 |
1994年 | 45篇 |
1993年 | 49篇 |
1992年 | 38篇 |
1991年 | 37篇 |
1990年 | 34篇 |
1989年 | 32篇 |
1988年 | 27篇 |
1987年 | 33篇 |
1983年 | 30篇 |
1982年 | 37篇 |
1981年 | 26篇 |
1980年 | 25篇 |
1979年 | 29篇 |
1978年 | 32篇 |
1976年 | 24篇 |
1974年 | 27篇 |
1973年 | 25篇 |
1972年 | 28篇 |
1970年 | 20篇 |
1967年 | 29篇 |
1966年 | 20篇 |
排序方式: 共有6950条查询结果,搜索用时 31 毫秒
71.
72.
73.
74.
Intact stamens of Tradescantia were fixed, dehydrated, and infiltrated with an epoxy resin. Each stamen was then put into a drop of resin on a microscope slide, which was transferred to the stage of a dissecting microscope so that individual hairs could be detached from the filament with fine tungsten needles. The detached hairs were transferred to drops of resin ca. 2 mm in diameter (6 or 7 in each of two rows) lying on a slide heavily coated with evaporated carbon. Polymerization was carried out in an oven until the resin attained a degree of viscosity that permitted orientation of the isolated hairs (by using a compound microscope) without their subsequent dislocation. When the small drops of resin had hardened after further polymerization, the positions of the hairs were marked by circumscribing the cells with India ink. The block was pried from the slide after rapid cooling with solid CO2, and was then trimmed and sectioned. Cells suspended in culture medium were embedded in much the same way; they were centrifuged to obtain a pellet, which was fixed, dehydrated, and infiltrated. A small fragment of the pellet with a little resin was placed on a microscope slide, where the cells were dissociated under a dissecting microscope at ca. 100 × magnification. Individual cells were then picked up with tungsten needles and transferred to droplets of resin on a carbon-coated slide. The subsequent steps were similar to those described for the staminate hairs. Pieces of tissue in the 50-500 μ range were also handled by the foregoing technique. However, after infiltration they were put into large drops of resin on a slide coated with silicone mold-release rather than on a surface coated with carbon. 相似文献
75.
Clostridium putrefaciens: A Neglected Anaerobe 总被引:2,自引:1,他引:1
Helen E. Ross 《Journal of applied microbiology》1965,28(1):49-51
76.
Embryonal carcinoma (EC) cells are developmentally pluripotential cells which can be induced to differentiate in cell culture to form a wide variety of cell types. To investigate the lineage relationships between cells of different types, we set out to isolate cell lines with multiple but restricted developmental potentials from differentiating cultures of P19 cells, a line of EC. By selecting for differentiated cells capable of anchorage-independent growth, we isolated cell lines which differentiated in high density cultures to form at least two cell types; myocytes that resembled fetal skeletal muscle cells and loose connective tissue cells that secreted large amounts of type I collagen. These results suggest that skeletal myocytes and connective tissue share a common precursor and that stem cells with limited but multiple developmental potentials can be isolated from differentiating cultures of P19 cells. 相似文献
77.
Linkage analysis of seven kindreds with the X-linked lymphoproliferative syndrome (XLP) confirms that the XLP locus is near DXS42 and DXS37 总被引:5,自引:0,他引:5
James C. Skare Helen L. Grierson John L. Sullivan Robert L. Nussbaum David T. Purtilo Bakary S. Sylla Gilbert M. Lenon Dorothy S. Reilly Bradley N. White Aubrey Milunsky 《Human genetics》1989,82(4):354-358
Summary Analysis of seven kindreds indicates that the XLP locus exhibits 1% recombination with DXS42 (lod = 17.5) and no recombination with DXS37 (lod = 13.3). 相似文献
78.
Russell G. Snell Leslie M. Thompson Danilo A. Tagle Tracey L. Holloway Glenn Barnes Helen G. Harley Lodewijk A. Sandkuijl Marcy E. MacDonald Francis S. Collins James F. Gusella Peter S. Harper Duncan J. Shaw 《American journal of human genetics》1992,51(2):357-362
We report both a recombination event that places the Huntington disease gene proximal to the marker D4S98 and an extended linkage-disequilibrium study that uses this marker and confirms the existence of disequilibrium between it and the HD locus. We also report the cloning of other sequences in the region around D4S98, including a new polymorphic marker R10 and conserved sequences that identify a gene in the region of interest. 相似文献
79.
80.
Abstract: K252a, an inhibitor of trk phosphorylation and nerve growth factor signal transduction in PC12 cells, blocked nerve growth factor-induced responses in cultured adult rat dorsal root ganglion sensory neurones. The nerve growth factor-dependent appearance of capsaicin sensitivity and accumulation of the neuropeptide substance P were inhibited when dorsal root ganglion neurones were grown in the presence of low concentrations (100 n M ) of K252a. At higher concentrations (3 µ M ), however, K252a stimulated the development of capsaicin sensitivity and the accumulation of substance P even in the absence of nerve growth factor. By using a wide dose range, therefore, we showed that K252a could either inhibit or mimic nerve growth factor's actions on sensory neurones. These results may explain the apparent paradox in the literature that some groups show a blocking effect of K252a on nerve growth factor-dependent survival of dorsal root ganglion sensory neurones, whereas others report that K252a can substitute for nerve growth factor or other trophic factors and promote neuronal survival. 相似文献