全文获取类型
收费全文 | 6585篇 |
免费 | 565篇 |
国内免费 | 2篇 |
出版年
2022年 | 46篇 |
2021年 | 105篇 |
2020年 | 56篇 |
2019年 | 92篇 |
2018年 | 117篇 |
2017年 | 100篇 |
2016年 | 173篇 |
2015年 | 267篇 |
2014年 | 250篇 |
2013年 | 393篇 |
2012年 | 461篇 |
2011年 | 386篇 |
2010年 | 272篇 |
2009年 | 245篇 |
2008年 | 324篇 |
2007年 | 350篇 |
2006年 | 349篇 |
2005年 | 307篇 |
2004年 | 268篇 |
2003年 | 268篇 |
2002年 | 258篇 |
2001年 | 127篇 |
2000年 | 117篇 |
1999年 | 100篇 |
1998年 | 74篇 |
1997年 | 56篇 |
1996年 | 58篇 |
1995年 | 41篇 |
1994年 | 63篇 |
1993年 | 70篇 |
1992年 | 68篇 |
1991年 | 71篇 |
1990年 | 65篇 |
1989年 | 49篇 |
1988年 | 60篇 |
1987年 | 67篇 |
1986年 | 32篇 |
1985年 | 58篇 |
1984年 | 60篇 |
1983年 | 48篇 |
1982年 | 53篇 |
1981年 | 53篇 |
1980年 | 41篇 |
1979年 | 33篇 |
1978年 | 48篇 |
1977年 | 49篇 |
1976年 | 29篇 |
1975年 | 32篇 |
1974年 | 27篇 |
1972年 | 32篇 |
排序方式: 共有7152条查询结果,搜索用时 796 毫秒
961.
The mitochondrial elongation factor EF-Tu (tufM) in rice (Oryza sativa L.) was isolated and characterized. The rice tufM cDNA clone contained 1,726 nucleotides and coded for a 453 amino acid protein including a putative mitochondrial transit peptide of 64 amino acid residues. This coding region was composed of 12 exons and 11 introns. The deduced amino acid sequence showed 62% and 88% identities with rice chloroplast EF-Tu (tufA) and Arabidopsis mitochondrial EF-Tu, respectively. As previously observed for the rice tufA gene, the tufM gene is likely present as one copy in rice. The mitochondrial EF-Tu gene was differentially expressed during flower development, and the other translational EF-Tu genes (chloroplast EF-Tu and cytosolic EF-1 alpha) were also distinctly expressed in a temporal manner. Phylogenetic analysis of the rice tufM gene showed that the mitochondrial tufA homologue of Reclinomonas was more closely related to the mitochondrial tufM genes of flowering plants than fungal and other mitochondrial tuf genes. In addition, the tufM encoded an N-terminal extension showing significant similarity to that of rps14 (or sdhB), which is also a nuclear-encoded rice mitochondrial gene. 相似文献
962.
Allan R Brasier 《BioTechniques》2002,32(1):100-2, 104, 106, 108-9
High-density oligonucleotide arrays are widely employed for detecting global changes in gene expression profiles of cells or tissues exposed to specific stimuli. Presented with large amounts of data, investigators can spend significant amounts of time analyzing and interpreting this array data. In our application of GeneChip arrays to analyze changes in gene expression in viral-infected epithelium, we have needed to develop additional computational tools that may be of utility to other investigators using this methodology. Here, I describe two executable programs to facilitate data extraction and multiple data point analysis. These programs run in a virtual DOS environment on Microsoft Windows 95/98/2K operating systems on a desktop PC. Both programs can be freely downloaded from the BioTechniques Software Library (www.BioTechniques.com). The first program, Retriever, extracts primary data from an array experiment contained in an Affymetrix textfile using user-inputted individual identification strings (e.g., the probe set identification numbers). With specific data retrieved for individual genes, hybridization profiles can be examined and data normalized. The second program, CompareTable, is used to facilitate comparison analysis of two experimental replicates. CompareTable compares two lists of genes, identifies common entries, extracts their data, and writes an output text file containing only those genes present in both of the experiments. The output files generated by these two programs can be opened and manipulated by any software application recognizing tab-delimited text files (e.g., Microsoft NotePad or Excel). 相似文献
963.
The Target of Rapamycin Signaling Pathway Regulates mRNA Turnover in the Yeast Saccharomyces cerevisiae
下载免费PDF全文
![点击此处可从《Molecular biology of the cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The target of rapamycin (TOR) signaling pathway is an important mechanism by which cell growth is regulated by nutrient availability in eukaryotes. We provide evidence that the TOR signaling pathway controls mRNA turnover in Saccharomyces cerevisiae. During nutrient limitation (diauxic shift) or after treatment with rapamycin (a specific inhibitor of TOR), multiple mRNAs were destabilized, whereas the decay of other mRNAs was unaffected. Our findings suggest that the regulation of mRNA decay by the TOR pathway may play a significant role in controlling gene expression in response to nutrient depletion. The inhibition of the TOR pathway accelerated the major mRNA decay mechanism in yeast, the deadenylation-dependent decapping pathway. Of the destabilized mRNAs, two different responses to rapamycin were observed. Some mRNAs were destabilized rapidly, while others were affected only after prolonged exposure. Our data suggest that the mRNAs that respond rapidly are destabilized because they have short poly(A) tails prematurely either as a result of rapid deadenylation or reduced polyadenylation. In contrast, the mRNAs that respond slowly are destabilized by rapid decapping. In summary, the control of mRNA turnover by the TOR pathway is complex in that it specifically regulates the decay of some mRNAs and not others and that it appears to control decay by multiple mechanisms. 相似文献
964.
Allan S. Hoffman Patrick S. Stayton Oliver Press Niren Murthy Chantal A. Lackey Charles Cheung Fiona Black Jean Campbell Nelson Fausto Themis R. Kyriakides Paul Bornstein 《Biotechnology and Bioprocess Engineering》2001,6(4):205-212
One of the important characteristics of biological systems is their ability to change important properties in response to
small environmental signals. The molecular mechanisms that biological molecules utilize to sense and respond provide interesting
models for the development of “smart” polymeric biomaterials with biomimetic properties. An important example of this is the
protein coat of viruses, which contains peptide units that facilitate the trafficking of the virus into the cell via endocytosis,
then out of the endosome into the cytoplasm, and from there into the nucleus. We have designed a family of synthetic polymers
whose compositions have been designed to mimic specific peptides on viral coats that facilitate endosomal escape. Our biomimetic
polymers are responsive to the lowered pH within endosomes, leading to disruption of the endosomal membrane and release of
important biomolecular drugs such as DNA, RNA, peptides and proteins to the cytoplasm before they are trafficked to lysosomes
and degraded by lysosomal enzymes. In this article, we review our work on the design, synthesis and action of such smart,
pH-sensitive polymers. 相似文献
965.
966.
When a habitat becomes fragmented and surrounded by another habitat this generally causes an increase in predation pressure at habitat transitions, often referred to as an edge effect. Edge effect in the form of enhanced nest predation intensities is one of the most cited explanations for bird population declines in fragmented landscapes. Here, we report results from a nest predation experiment conducted in a tropical montane forest landscape in the Uzungwa Mts., Tanzania. Using artificial nests with chicken eggs, we determined predation rates across a fragmentation gradient. The proportion of indigenous forest in four landscapes used in the study were 0.29, 0.58, 0.75 to 1.0. Nest predation intensities on artificial nests were about 19% higher inside intact forest than at edges in fragmented forest landscapes. Furthermore, predation intensities were relatively constant across a forest fragmentation gradient. Our results thus challenge the applicability and generality of the edge effect, derived from studies almost exclusively conducted in temperate regions rather than tropical forest ecosystems. Nest predation levels differences between tropical montane forest and that reported in other forest ecosystems are discussed. 相似文献
967.
968.
969.
970.
D. Allan Drummond 《Current biology : CB》2009,19(17):R740-R742