全文获取类型
收费全文 | 2096篇 |
免费 | 147篇 |
国内免费 | 2篇 |
出版年
2021年 | 48篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 30篇 |
2017年 | 28篇 |
2016年 | 48篇 |
2015年 | 72篇 |
2014年 | 96篇 |
2013年 | 138篇 |
2012年 | 148篇 |
2011年 | 131篇 |
2010年 | 83篇 |
2009年 | 98篇 |
2008年 | 90篇 |
2007年 | 116篇 |
2006年 | 96篇 |
2005年 | 80篇 |
2004年 | 84篇 |
2003年 | 74篇 |
2002年 | 53篇 |
2001年 | 48篇 |
2000年 | 57篇 |
1999年 | 32篇 |
1998年 | 19篇 |
1997年 | 24篇 |
1996年 | 13篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 25篇 |
1992年 | 26篇 |
1991年 | 40篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 23篇 |
1986年 | 12篇 |
1985年 | 22篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1979年 | 17篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1974年 | 11篇 |
1973年 | 24篇 |
1972年 | 13篇 |
1971年 | 16篇 |
1969年 | 10篇 |
1967年 | 13篇 |
1966年 | 12篇 |
排序方式: 共有2245条查询结果,搜索用时 15 毫秒
101.
102.
103.
Jabbarzadeh E Jiang T Deng M Nair LS Khan YM Laurencin CT 《Biotechnology and bioengineering》2007,98(5):1094-1102
Bone tissue engineering offers promising alternatives to repair and restore tissues. Our laboratory has employed poly(lactide-co-glycolide) PLAGA microspheres to develop a three dimensional (3-D) porous bioresorbable scaffold with a biomimetic pore structure. Osseous healing and integration with the surrounding tissue depends in part on new blood vessel formation within the porous structure. Since endothelial cells play a key role in angiogenesis (formation of new blood vessels from pre-existing vasculature), the purpose of this study was to better understand human endothelial cell attachment, viability, growth, and phenotypic expression on sintered PLAGA microsphere scaffold. Scanning electron microscopy (SEM) examination showed cells attaching to the surface of microspheres and bridging the pores between the microspheres. Cell proliferation studies indicated that cell number increased during early stages and reached a plateau between days 10 and 14. Immunofluorescent staining for actin showed that cells were proliferating three dimensionally through the scaffolds while staining for PECAM-1 (platelet endothelial cell adhesion molecule) displayed typical localization at cell-cell contacts. Gene expression analysis showed that endothelial cells grown on PLAGA scaffolds maintained their normal characteristic phenotype. The cell proliferation and phenotypic expression were independent of scaffold pore architecture. These results demonstrate that PLAGA sintered microsphere scaffolds can support the growth and biological functions of human endothelial cells. The insights from this study should aid future studies aimed at enhancing angiogenesis in three dimensional tissue engineered scaffolds. 相似文献
104.
Melanocyte–keratinocyte interaction induces calcium signalling and melanin transfer to keratinocytes
Preeti G. Joshi Nirmala Nair Gulnaz Begum Nanda B. Joshi Vilas P. Sinkar Shilpa Vora 《Pigment cell & melanoma research》2007,20(5):380-384
Physical contact between melanocytes and keratinocytes is a prerequisite for melanosome transfer to occur, but cellular signals induced during or after contact are not fully understood. Herein, it is shown that interactions between melanocyte and keratinocyte plasma membranes induced a transient intracellular calcium signal in keratinocytes that was required for pigment transfer. This intracellular calcium signal occurred due to release of calcium from intracellular stores. Pigment transfer observed in melanocyte–keratinocyte co‐cultures was inhibited when intracellular calcium in keratinocytes was chelated. We propose that a ‘ligand‐receptor’ type interaction exists between melanocytes and keratinocytes that triggers intracellular calcium signalling in keratinocytes and mediates melanin transfer. 相似文献
105.
106.
Pereira LA Báo SN Barbosa MS da Silva JL Felipe MS de Santana JM Mendes-Giannini MJ de Almeida Soares CM 《FEMS yeast research》2007,7(8):1381-1388
Paracoccidioides brasiliensis is an important fungal pathogen. The disease it causes, paracoccidioidomycosis (PCM), ranges from localized pulmonary infection to systemic processes that endanger the life of the patient. Paracoccidioides brasiliensis adhesion to host tissues contributes to its virulence, but we know relatively little about molecules and the molecular mechanisms governing fungal adhesion to mammalian cells. Triosephosphate isomerase (TPI: EC 5.3.1.1) of P. brasiliensis (PbTPI) is a fungal antigen characterized by microsequencing of peptides. The protein, which is predominantly expressed in the yeast parasitic phase, localizes at the cell wall and in the cytoplasmic compartment. TPI and the respective polyclonal antibody produced against this protein inhibited the interaction of P. brasiliensis to in vitro cultured epithelial cells. TPI binds preferentially to laminin, as determined by peptide inhibition assays. Collectively, these results suggest that TPI is required for interactions between P. brasiliensis and extracellular matrix molecules such as laminin and that this interaction may play an important role in the fungal adherence and invasion of host cells. 相似文献
107.
108.
109.
Rhizobia are used exclusively in agricultural systems for enhancing the ability of legumes to fix atmospheric nitrogen. Knowledge about the indigenous population is necessary for the selection and application of inoculant strains. In this study, we have assessed the genetic diversity of Bradyrhizobium strains isolated from the host plant, Arachis hypogaea along the coastline of Tamil Nadu. Different populations collected from varying environmental conditions were analysed for salt and pH tolerance. Genetic diversity among the strains was studied using RAPD markers and PCR-RFLP of 16S rDNA and nifD genes. The approaches used in this study yielded consistent results, which revealed a high degree of heterogeneity among strains and detection of two distinct genetic groups. 相似文献
110.
Jain D Nair DT Swaminathan GJ Abraham EG Nagaraju J Salunke DM 《The Journal of biological chemistry》2001,276(44):41377-41382
The crystal structure of an antibacterial protein of immune origin (TSWAB), purified from tasar silkworm (Antheraea mylitta) larvae after induction by Escherichia coli infection, has been determined. This is the first insect lysozyme structure and represents induced lysozymes of innate immunity. The core structure of TSWAB is similar to c-type lysozymes and alpha-lactalbumins. However, TSWAB shows significant differences with respect to the other two proteins in the exposed loop regions. The catalytic residues in TSWAB are conserved with respect to the chicken lysozyme, indicating a common mechanism of action. However, differences in the noncatalytic residues in the substrate binding groove imply subtle differences in the specificity and the level of activity. Thus, conformational differences between TSWAB and chicken lysozyme exist, whereas functional mechanisms appear to be similar. On the other hand, alpha-lactalbumins and c-type lysozymes exhibit drastically different functions with conserved molecular conformation. It is evident that a common molecular scaffold is exploited in the three enzymes for apparently different physiological roles. It can be inferred on the basis of the structure-function comparison of these three proteins having common phylogenetic origin that the conformational changes in a protein are minimal during rapid evolution as compared with those in the normal course of evolution. 相似文献