全文获取类型
收费全文 | 5498篇 |
免费 | 393篇 |
国内免费 | 3篇 |
出版年
2023年 | 26篇 |
2022年 | 34篇 |
2021年 | 116篇 |
2020年 | 103篇 |
2019年 | 127篇 |
2018年 | 172篇 |
2017年 | 156篇 |
2016年 | 239篇 |
2015年 | 370篇 |
2014年 | 379篇 |
2013年 | 459篇 |
2012年 | 509篇 |
2011年 | 483篇 |
2010年 | 327篇 |
2009年 | 282篇 |
2008年 | 348篇 |
2007年 | 318篇 |
2006年 | 275篇 |
2005年 | 257篇 |
2004年 | 239篇 |
2003年 | 192篇 |
2002年 | 169篇 |
2001年 | 68篇 |
2000年 | 40篇 |
1999年 | 30篇 |
1998年 | 38篇 |
1997年 | 19篇 |
1996年 | 24篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1962年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有5894条查询结果,搜索用时 31 毫秒
991.
992.
Koh CJ Delo DM Lee JW Siddiqui MM Lanza RP Soker S Yoo JJ Atala A 《Methods (San Diego, Calif.)》2009,47(2):90-97
Embryonic stem cells are envisioned as a viable source of pluripotent cells for use in regenerative medicine applications when donor tissue is not available. However, most current harvest techniques for embryonic stem cells require the destruction of embryos, which has led to significant political and ethical limitations on their usage. Parthenogenesis, the process by which an egg can develop into an embryo in the absence of sperm, may be a potential source of embryonic stem cells that may avoid some of the political and ethical concerns surrounding embryonic stem cells. Here we provide the technical aspects of embryonic stem cell isolation and expansion from the parthenogenetic activation of oocytes. These cells were characterized for their stem-cell properties. In addition, these cells were induced to differentiate to the myogenic, osteogenic, adipogenic, and endothelial lineages, and were able to form muscle-like and bony-like tissue in vivo. Furthermore, parthenogenetic stem cells were able to integrate into injured muscle tissue. Together, these results demonstrate that parthenogenetic stem cells can be successfully isolated and utilized for various tissue engineering applications. 相似文献
993.
994.
Won Jun Choi Hyuk Woo Lee Hea Ok Kim Moshe Chinn Zhan-Guo Gao Amit Patel Kenneth A. Jacobson Hyung Ryong Moon Young Hoon Jung Lak Shin Jeong 《Bioorganic & medicinal chemistry》2009,17(23):8003-8011
On the basis of a bioisosteric rationale, 4′-thionucleoside analogues of IB-MECA (N6-(3-Iodo-benzyl)-9-(5′-methylaminocarbonyl-β-d-ribofuranosyl)adenine), which is a potent and selective A3 adenosine receptor (AR) agonist, were synthesized from d-gulonic acid γ-lactone. The 4′-thio analogue (5h) of IB-MECA showed extremely high binding affinity (Ki = 0.25 nM) at the human A3AR and was more potent than IB-MECA (Ki = 1.4 nM). Bulky substituents at the 5′-uronamide position, such as cyclohexyl and 2-methylbenzyl, in this series of 2-H nucleoside derivatives were tolerated in A3AR binding, although small alkyl analogues were more potent. 相似文献
995.
996.
The astrocyte porosome complex, the secretory machinery at the plasma membrane of astrocytes, is a 10-15 nm cup-shaped lipoprotein structure possessing a central plug. Since the porosome is a membrane-associated, multi-protein complex, it has precluded the generation of 3D crystals for X-ray diffraction studies, nor structural analysis at the atomic level using the solution NMR. These limitations were partially overcome in the current studies, furthering our understanding of the porosome structure in astrocytes. Using atomic force microscopy, electron microscopy, and electron density and 3D contour mapping, finally provides at the nanoscale, the structure and assembly of proteins within the astrocyte porosome complex. Results from this study demonstrate a set of protein units lining the porosome cup, each connected via spoke-like elements to a central plug region within the structure. In contrast to the neuronal porosome, which possess eight globular proteins at the outer rim of the complex, the porosome complex appear to possess 12 such globular structures. Nature has designed the porosome as the universal secretory machinery, but has fine-tuned its use to suite secretion from different cell types. The isolation of intact astrocyte porosomes for near-atomic resolution using cryo-electron diffraction measurements, is finally possible. 相似文献
997.
Heparin/heparan sulfate (HS) plays a key role in cellular adhesion. In this study, we utilized a 12‐mer random Escherichia coli cell surface display library to identify the sequence, which binds to heparin. Isolated insert analysis revealed a novel heparin‐binding peptide sequence, VRRSKHGARKDR, designated as HBP12. Our analysis of the sequence alignment of heparin‐binding motifs known as the Cardin–Weintraub consensus (BBXB, where B is a basic residue) indicates that the HBP12 peptide sequence contains two consecutive heparin‐binding motifs (i.e. RRSK and RKDR). SPR‐based BIAcore technology demonstrated that the HBP12 peptide binds to heparin with high affinity (KD = 191 nM ). The HBP12 peptide is found to bind the cell surface HS expressed by osteoblastic MC3T3 cells and promote HS‐dependent cell adhesion. Moreover, the surface‐immobilized HBP12 peptide on titanium substrates shows significant increases in the osteoblastic MC3T3‐E1 cell adhesion and proliferation. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
998.
Chester Bittencourt Sacramento Vanessa Dionisio Cantagalli Mariana Grings Leonardo Pinto Carvalho José Carlos Costa Baptista‐Silva Abram Beutel Cassia Toledo Bergamaschi Ruy Ribeiro de Campos Junior Jane Zveiter de Moraes Christina Maeda Takiya Vívian Yochiko Samoto Radovan Borojevic Flavia Helena da Silva Nance Beyer Nardi Hans Fernando Dohmann Hamilton Silva Junior Valderez Bastos Valero Sang Won Han 《The journal of gene medicine》2009,11(4):345-353
999.
Ming Shun Li Jong Yul Roh Xueying Tao Zi Niu Yu Zi Duo Liu Qin Liu Hong Guang Xu Hee Jin Shim Yang-Su Kim Yong Wang Jae Young Choi Yeon Ho Je 《Journal of microbiology (Seoul, Korea)》2009,47(4):466-472
Bacillus thuringiensis, an entomopathogenic bacterium belonging to the B. cereus group, harbors numerous extra-chromosomal DNA molecules whose sizes range from 2 to 250 kb. In this study, we used a plasmid capture system (PCS) to clone three small plasmids from B. thuringiensis subsp. kurstaki Kl which were not found in B. thuringiensis subsp. kurstaki HD-1, and determined the complete nucleotide sequence of plasmid pKlS-1 (5.5 kb). Of the six putative open reading frames (ORF2-ORF7) in pKlS-1, ORF2 (MobKl) showed approximately 90% aa identity with the Mob-proteins of pGI2 and pTX14-2, which are rolling circle replicating group VII (RCR group VII) plasmids from B. thuringiensis. In addition, a putative origin of transfer (oriT) showed 95.8% identity with those of pGI2 and pTX14-2. ORF3 (RepK1) showed relatively low aa identity (17.8~25.2%) with the Rep protein coded by RCR plasmids, however. The putative double-strand origin of replication (dso) and single-strand origin of replication (sso) of pKlS-1 exhibited approximately 70% and 64% identities with those of pGI2 and pTX14-2. ORF6 and 7 showed greater than 50% similarities with alkaline serine protease, which belongs to the subtilase family. The other 2 ORFs were identified as hypothetical proteins. To determine the replicon of pKlS-1, seven subclones were contructed in the B. thuringiensis ori-negative pHTIK vector and were electroporated into a plasmid cured B. thuringiensis strain. The 1.6 kb region that included the putative ORF3 (ReplK), dso and ORF4, exhibited replication ability. These findings identified pKlS-1 as a new RCR group VII plasmid, and determined its replication region. 相似文献
1000.
Jiwon Ahn Chung-Hae Choi Chang-Mo Kang Chun-Ho Kim Hee-Moon Park Kyung-Bin Song Kwang-Lae Hoe Misun Won Kyung-Sook Chung 《Journal of microbiology (Seoul, Korea)》2009,47(6):789-795
An immediate challenge in the post-genomic era is to assign a biological functions to proteins unraveled by genome analysis.
This report is based on studies conducted using Schizosaccharomyces pombe, a simple model organism, and presents various vector systems as tools for high-throughput functional analysis of human genes.
We constructed S. pombe expression vectors for efficient cloning of genes via the Gateway system. We modified the pREP and pSLF series vectors, which
are widely used for gene expression in S. pombe. The vectors constructed have a uniform backbone of S. pombe autonomously replicating sequence (ARS) elements with different selective markers, namely, urw4
+ and Saccharomyces cerevisiae LEU2 complementing leul. These vectors contain 3 different strengths of the inducible promoter nmtl, which affect the expression levels of the cloned open reading frames (ORFs). Further, target proteins can be fused with
an N-terminal or C-terminal tag such as triple hemagglutinin (3× HA), enhanced green fluorescent protein (EGFP), or Discosoma red fluorescent protein (DsRed). We tested the feasibility of the constructed vectors by using 3 human genes, namely, RAB18, SCC-112, and PTEN. Proper expression of tagged RAB18 was confirmed by western blot analysis. Further, localization of RAB18, SCC112, and PTEN was demonstrated. The constructed
vectors can be utilized for high-throughput functional analysis of heterologous genes. 相似文献