全文获取类型
收费全文 | 8756篇 |
免费 | 784篇 |
国内免费 | 1篇 |
出版年
2024年 | 3篇 |
2023年 | 33篇 |
2022年 | 24篇 |
2021年 | 186篇 |
2020年 | 113篇 |
2019年 | 152篇 |
2018年 | 188篇 |
2017年 | 161篇 |
2016年 | 291篇 |
2015年 | 469篇 |
2014年 | 508篇 |
2013年 | 545篇 |
2012年 | 775篇 |
2011年 | 736篇 |
2010年 | 459篇 |
2009年 | 423篇 |
2008年 | 569篇 |
2007年 | 570篇 |
2006年 | 532篇 |
2005年 | 536篇 |
2004年 | 492篇 |
2003年 | 457篇 |
2002年 | 430篇 |
2001年 | 74篇 |
2000年 | 50篇 |
1999年 | 95篇 |
1998年 | 103篇 |
1997年 | 59篇 |
1996年 | 47篇 |
1995年 | 58篇 |
1994年 | 48篇 |
1993年 | 52篇 |
1992年 | 44篇 |
1991年 | 31篇 |
1990年 | 40篇 |
1989年 | 26篇 |
1988年 | 29篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 16篇 |
1984年 | 18篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有9541条查询结果,搜索用时 15 毫秒
1.
2.
Stephen J. Assinder Lisa V.J. Eynstone R. Peter Shellis George H. Dibdin 《FEMS microbiology letters》1995,134(2-3):287-292
Abstract The pac gene encoding the penicillin G acylase (PGA) of Bacillus megaterium ATCC 14945 has been cloned in Escherichia coli HB101 ( proA, leuB ) using a selective minimal medium containing phenylacetyl-L-leucine instead of L-leucine. The nucleotide sequence of this gene has been determined and contains an open reading frame of 2406 nucleotides. The deduced amino acid sequence shows significant similarity with other β-lactam acylases. Although the PGA of B. megaterium is extracellular, the enzyme produced in E. coli appears to have a cytoplasmic localization. 相似文献
3.
4.
5.
6.
7.
Karlheinz Grillitsch Pablo Tarazona Lisa Klug Tamara Wriessnegger Günther Zellnig Erich Leitner Ivo Feussner Günther Daum 《生物化学与生物物理学报:生物膜》2014
Despite similarities of cellular membranes in all eukaryotes, every compartment displays characteristic and often unique features which are important for the functions of the specific organelles. In the present study, we biochemically characterized the plasma membrane of the methylotrophic yeast Pichia pastoris with emphasis on the lipids which form the matrix of this compartment. Prerequisite for this effort was the design of a standardized and reliable isolation protocol of the plasma membrane at high purity. Analysis of isolated plasma membrane samples from P. pastoris revealed an increase of phosphatidylserine and a decrease of phosphatidylcholine compared to bulk membranes. The amount of saturated fatty acids in the plasma membrane was higher than in total cell extracts. Ergosterol, the final product of the yeast sterol biosynthetic pathway, was found to be enriched in plasma membrane fractions, although markedly lower than in Saccharomyces cerevisiae. A further characteristic feature of the plasma membrane from P. pastoris was the enrichment of inositol phosphorylceramides over neutral sphingolipids, which accumulated in internal membranes. The detailed analysis of the P. pastoris plasma membrane is discussed in the light of cell biological features of this microorganism especially as a microbial cell factory for heterologous protein production. 相似文献
8.
The endoplasmic reticulum (ER) of live metaphase II mouse eggs and prophase I-arrested oocytes was compared using the fluorescent, lipophilic dicarbocyanine dye, DiI. DiI, dissolved in soybean oil, was microinjected into oocytes and eggs; the dye diffused throughout the cytoplasm to label the ER, which was imaged by confocal microscopy. The mature egg had a fine reticular network of ER throughout the cell and numerous dense accumulations of membrane in the cortex. These ER accumulations, 1-2 μm in diameter, were generally absent deeper in the cytoplasm. A similar staining pattern was observed when the eggs were fixed within 1 min of injection, providing evidence that the cortical accumulations of membrane are part of a continuous ER membrane system, since membrane trafficking could not occur in a fixed egg. Cortical ER accumulations were localized to the same region of the egg as the cortical granules and were not observed in the cortical granule-free region adjacent to the meiotic spindle. In contrast, ER accumulations were rarely found in the cortex of the immature, prophase I-arrested oocyte, but larger and less well-defined membrane clusters were found throughout the deeper cytoplasm of the oocyte. The appearance of ER clusters in the egg cortex following oocyte maturation correlates with an increased ability of the mature egg to release calcium at fertilization. Since the ER is a calcium store, structural reorganization of the ER may be necessary to permit the large release of calcium and resulting cortical granule exocytosis at fertilization. 相似文献
9.
10.