全文获取类型
收费全文 | 7523篇 |
免费 | 412篇 |
国内免费 | 312篇 |
出版年
2023年 | 87篇 |
2022年 | 139篇 |
2021年 | 178篇 |
2020年 | 149篇 |
2019年 | 280篇 |
2018年 | 289篇 |
2017年 | 128篇 |
2016年 | 159篇 |
2015年 | 246篇 |
2014年 | 397篇 |
2013年 | 485篇 |
2012年 | 301篇 |
2011年 | 480篇 |
2010年 | 381篇 |
2009年 | 411篇 |
2008年 | 449篇 |
2007年 | 458篇 |
2006年 | 390篇 |
2005年 | 382篇 |
2004年 | 237篇 |
2003年 | 238篇 |
2002年 | 257篇 |
2001年 | 174篇 |
2000年 | 148篇 |
1999年 | 144篇 |
1998年 | 129篇 |
1997年 | 109篇 |
1996年 | 112篇 |
1995年 | 60篇 |
1994年 | 74篇 |
1993年 | 60篇 |
1992年 | 69篇 |
1991年 | 49篇 |
1990年 | 43篇 |
1989年 | 39篇 |
1988年 | 43篇 |
1987年 | 39篇 |
1986年 | 32篇 |
1985年 | 50篇 |
1984年 | 52篇 |
1983年 | 31篇 |
1982年 | 62篇 |
1981年 | 40篇 |
1980年 | 33篇 |
1979年 | 33篇 |
1978年 | 30篇 |
1977年 | 16篇 |
1975年 | 13篇 |
1974年 | 19篇 |
1973年 | 9篇 |
排序方式: 共有8247条查询结果,搜索用时 31 毫秒
81.
Inactivation of bleomycin by an N-acetyltransferase in the bleomycin-producing strain Streptomyces verticillus 总被引:1,自引:0,他引:1
Masanori Sugiyama Takanori Kumagai Mitsuhiko Shionoya Eiichi Kimura Julian E. Davies 《FEMS microbiology letters》1994,121(1):81-85
Abstract Bleomycin-producing Streptomyces verticillus ATCC15003 possesses a bleomycin acetyltransferase which inactivates the drug in the presence of acetyl coenzyme A. The site of acylation in enzymically prepared acetylbleomycin A2 was determined by nuclear magnetic resonance analysis; the primary amino group of the β-aminoalanine moiety of bleomycin was acetylated. Acetylbleomycin A2 had no detectable antibacterial activity and did not induce in vitro DNA degradation. 相似文献
82.
Spyros D. Georgatos 《Journal of cellular biochemistry》1994,55(1):69-76
In the age of “virtual reality,” the imperfect microscopic silhouettes of cells and organelles are gradually being replaced by calligraphic computer drawings. In this context, textbooks and introductory slides often depict the cell nucleus as a smooth-shaped, featureless object. However, in reality, the nuclei of different cells possess distinct sizes and morphological features which develop in a programmed fashion as each cell differentiates. To dissect this complex morphogenetic process, we need to identify the basic elements that determine nuclear architecture and the regulatory factors involved. Recently, clues about the identity of these components have been obtained both by systematic analysis and by serendipity. This review summarizes a few recent findings and ideas that may serve as a first forum for future discussions and, I hope, for further work on this topic. © 1994 Wiley-Liss, Inc. 相似文献
83.
84.
Osmium tetroxide (OsO4) reacts with the thymine residues of double-stranded DNA, but thymines that are unpaired or under torsional stress are hyperreactive. Although OsO4 hyperreactivity has been primarily utilized to identify Z-DNA structures in supercoiled plasmids, OsO4 will also identify other torsional perturbations of DNA. In this study, OsO4 was used to footprint an AT-rich region (between –780 and –500) of the maizeAdh1 promoter. Hyperreactive sites were identified bothin vitro andin vivo in an area that coincides with AT motifs similar to those found in scaffold attachment regions. Further, the region of OsO4 hyperreactivity lies within a fragment of DNA that is associated with the nuclear scaffold in histone-depleted nuclei. 相似文献
85.
86.
87.
本实验用免疫印迹法纯化的抗EBNA亚型抗体,结合显微荧光分光光度检测技术,检测在不同感染状态下,三种亚型EBNA抗原在细胞中的表达程度。结果表明,处于潜伏感染状态下的Raji细胞EBNA-1表达量较大,经巴豆油和正丁酸诱导进入钝挫感染状态后EBNA-1表达减少,而EBNA-2的表达增强。B_(95-8)细胞也有相似的趋势。表明EB病毒的激活可能与不同EBNA亚型表达量的改变有关。 相似文献
88.
Andrea Casasco Marco Casasco Antonia Lcaro Cornaglia Marco Danova Monica Giordano Alberto Calligaro 《Biotechnic & histochemistry》1994,69(2):112-117
PC10 is a monoclonal antibody to proliferating cell nuclear antigen, a nuclear protein associated with the cell cycle. We have evaluated the effects of tissue fixation on PC10 immunoreactivity in sections of paraffin embedded rat tissues. Immunoreactivity was well preserved in tissues after fixation with alcohol-based solutions for 3-24 hr. Fewer PC10-positive cells were detectable in samples fixed with formaldehydecontaining solutions compared with samples fixed with alcohol for the same time. Loss of PC10 immunoreactivity in formaldehyde fixed tissues was progressive, and quantifiable as early as after 3 hr fixation. Consequently, alcohol-based fixatives are strongly recommended for any immunocytochemical prospective study using PC10 antibody. In contrast, loss of PC10-immunoreactivity is always predictable, but difficult to quantitate, using formaldehyde fixed specimens. This aspect should be considered when using PC10 antibody in retrospective studies with routinely-processed archival material. 相似文献
89.
90.