全文获取类型
收费全文 | 2116篇 |
免费 | 149篇 |
国内免费 | 2篇 |
出版年
2022年 | 13篇 |
2021年 | 44篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 30篇 |
2017年 | 27篇 |
2016年 | 48篇 |
2015年 | 71篇 |
2014年 | 97篇 |
2013年 | 138篇 |
2012年 | 149篇 |
2011年 | 132篇 |
2010年 | 83篇 |
2009年 | 98篇 |
2008年 | 90篇 |
2007年 | 117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 | 37篇 |
1998年 | 22篇 |
1997年 | 25篇 |
1996年 | 15篇 |
1995年 | 20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 | 13篇 |
1985年 | 22篇 |
1984年 | 14篇 |
1983年 | 13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 |
1967年 | 14篇 |
1966年 | 12篇 |
排序方式: 共有2267条查询结果,搜索用时 187 毫秒
101.
102.
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
103.
104.
105.
106.
Glyphidrilus annandalei Michaelson exhibits a pronounced breeding period extending from September to November. Breeding individuals achieve their maximum frequency in September, when 50 per cent of the whole population was with fully developed clitellum. Studies on the physical and chemical conditions of the habitat revealed that breeding in this worm depends the monsoon of the area creating optimum conditions for the life and activities of the organism. 相似文献
107.
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
108.
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
109.
Adhesion of neutrophils to substrate is initiated by receptor-ligand interactions that induce outside-in signaling. Inside-out signals and lateral interactions between surface molecules further fine tune the response. This study investigates the role of CD66 in adhesion of neutrophils to fibronectin, using domain-mapped monoclonal antibodies to CD66. Neutrophils express CD66a, CD66b, and CD66c on their surface. The neutrophil surface molecules that bind to fibronectin are the alpha(4)beta(1) and alpha(5)beta(1) integrins. Our results show that the monoclonal antibody Kat4c, which recognizes the AB domain of CD66a, b, and c and the polyclonal anti-CD66 (anti-carcinoembryonic antigen), augments neutrophil adhesion to fibronectin, while monoclonal antibodies to the individual CD66 antigens, the Fab fragment of Kat4c, and a mixture of the individual antibodies to CD66 antigens were unable to affect the adhesion. Thus heterodimerization of CD66a, b, and c is required for promoting neutrophil adhesion to fibronectin. The increased adhesion in presence of Kat4c was inhibited by antibodies to the beta(1) and beta(2) integrins. Antibody ligation of CD66 antigens causes their clustering and concomitant coclustering of the alpha(M) subunit of the beta(2) integrin, thereby activating the integrin. The sugar alpha-methyl mannoside inhibited anti-CD66-mediated clustering, indicating that a carbohydrate-lectin interaction may exist between CD66 and alpha(M) integrin. It also reduced the increased adhesion of neutrophils to fibronectin, suggesting that beta(2) integrin activation precedes beta(1) integrin activation. Further, the anti-CD66-mediated adhesion to fibronectin is accompanied by increased localization of Src family kinases (lyn and hck) to the cytoskeleton and an increase in their kinase activity. These results suggest that crosslinking of CD66a, CD66b, and CD66c promotes activation of the beta(2) integrin and in turn an alteration in the affinity of the beta(1) integrin, which enhances the adhesion of neutrophils to fibronectin. 相似文献
110.