全文获取类型
收费全文 | 1143篇 |
免费 | 141篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 32篇 |
2020年 | 8篇 |
2019年 | 24篇 |
2018年 | 23篇 |
2017年 | 30篇 |
2016年 | 26篇 |
2015年 | 54篇 |
2014年 | 55篇 |
2013年 | 68篇 |
2012年 | 78篇 |
2011年 | 66篇 |
2010年 | 73篇 |
2009年 | 34篇 |
2008年 | 68篇 |
2007年 | 55篇 |
2006年 | 59篇 |
2005年 | 51篇 |
2004年 | 50篇 |
2003年 | 43篇 |
2002年 | 39篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 28篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1972年 | 8篇 |
1971年 | 8篇 |
排序方式: 共有1284条查询结果,搜索用时 15 毫秒
101.
Anderson CL Iyer SS Ziegler TR Jones DP 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,293(3):R1069-R1075
Human cell lines regulate the redox state (E(h)) of the cysteine/cystine (Cys/CySS) couple in culture medium to approximately -80 mV, a value similar to the average E(h) for Cys/CySS in human plasma. The mechanisms involved in regulation of extracellular E(h) of Cys/CySS are not known, but GSH is released from tissues at rates proportional to tissue GSH concentration, and this released GSH could react with CySS to contribute to maintenance of this balance. The present study was undertaken to determine whether depletion of cellular GSH alters regulation of extracellular Cys/CySS E(h). Decrease of GSH in HT-29 cells by inhibiting synthesis with l-buthionine-[S,R]-sulfoximine showed no effect on the rate of reduction of extracellular CySS to achieve a stable E(h) for Cys/CySS in the culture medium. Limiting Cys and CySS in the culture medium also substantially decreased cellular GSH but resulted in no significant effect on extracellular Cys/CySS E(h). Addition of CySS to these cells showed that extracellular Cys/CySS E(h) approached -80 mV at 4 h while cellular GSH and extracellular GSH/GSSG E(h) recovered more slowly. Together, these results show that HT-29 cells have the capacity to regulate the extracellular Cys/CySS E(h) by mechanisms that are independent of cellular GSH. The results suggest that transport systems for Cys and CySS and/or membranal oxidoreductases could be more important than cellular GSH in regulation of extracellular Cys/CySS E(h). 相似文献
102.
Saswati Nayak Radha Prasanna Boddupalli M. Prasanna Dina B. Sahoo 《World journal of microbiology & biotechnology》2007,23(11):1575-1584
A set of 24 strains belonging to the genus Anabaena (Phylum Cyanobacteria), isolated from diverse geographic locations in India, were evaluated along with three International
type strains of Anabaena (ATCC 29414, ATCC 29208 and ATCC 27899) for their morphological, physiological and biochemical diversity. The morphological
dataset, consisting of 58 variants for 15 characters, and SDS-PAGE protein profiles comprising 17 polymorphic bands were utilized
to differentiate the selected Anabaena strains and explore the patterns of diversity through cluster analysis. Physiological and biochemical characterization with
respect to nitrogen fixation and accumulation of chlorophyll and phycobiliproteins led to the identification of some highly
promising Anabaena strains for use as biofertilizers and source of pigments. The study highlighted the tremendous inter and intraspecific diversity
within the Anabaena isolates and indicated the potential as well as constraints of the morphological and protein profiling datasets for unambiguous
differentiation and analyses of diversity among the Anabaena strains. 相似文献
103.
Xu J Woods CR Mora AL Joodi R Brigham KL Iyer S Rojas M 《American journal of physiology. Lung cellular and molecular physiology》2007,293(1):L131-L141
Bone marrow-derived mesenchymal stem cells (BMDMSCs) appear to be important in repair of the chronic lung injury caused by bleomycin in mice. To determine effects of these BMDMSCs on an acute inflammatory response, we injected C57BL/6 mice intraperitoneally with 1 mg/kg endotoxin followed either by intravenous infusion of 5 x 10(5) BMDMSCs, the same number of lung fibroblasts, or an equal volume of normal saline solution. Lungs harvested 6, 24, and 48 h and 14 days after endotoxin showed that BMDMSC administration prevented endotoxin-induced lung inflammation, injury, and edema. Although we were able to detect donor cells in the lungs at 1 day after endotoxin, by 14 days no donor cells were detected. BMDMSC administration suppressed the endotoxin-induced increase in circulating proinflammatory cytokines without decreasing circulating levels of anti-inflammatory mediators. Ex vivo cocultures of BMDMSC and lung cells from endotoxemic animals demonstrated a bilateral conversation in which lung cells stimulated proliferation and migration of stem cells and suppressed proinflammatory cytokine production by lung cells. We conclude that BMDMSCs decrease both the systemic and local inflammatory responses induced by endotoxin. These effects do not require either lung engraftment or differentiation of the stem cells and are due at least in part to the production of stem cell chemoattractants by the lungs and to humoral and physical interactions between stem cells and lung cells. We speculate that mobilization of this population of BMDMSCs may be a general mechanism for modulating an acute inflammatory response. 相似文献
104.
105.
Chikara Otsubo Sivakama Bharathi Radha Uppala Olga R. Ilkayeva Dongning Wang Kevin McHugh Ye Zou Jieru Wang John F. Alcorn Yi Y. Zuo Matthew D. Hirschey Eric S. Goetzman 《The Journal of biological chemistry》2015,290(39):23897-23904
The role of mitochondrial energy metabolism in maintaining lung function is not understood. We previously observed reduced lung function in mice lacking the fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase (LCAD). Here, we demonstrate that long-chain acylcarnitines, a class of lipids secreted by mitochondria when metabolism is inhibited, accumulate at the air-fluid interface in LCAD−/− lungs. Acylcarnitine accumulation is exacerbated by stress such as influenza infection or by dietary supplementation with l-carnitine. Long-chain acylcarnitines co-localize with pulmonary surfactant, a unique film of phospholipids and proteins that reduces surface tension and prevents alveolar collapse during breathing. In vitro, the long-chain species palmitoylcarnitine directly inhibits the surface adsorption of pulmonary surfactant as well as its ability to reduce surface tension. Treatment of LCAD−/− mice with mildronate, a drug that inhibits carnitine synthesis, eliminates acylcarnitines and improves lung function. Finally, acylcarnitines are detectable in normal human lavage fluid. Thus, long-chain acylcarnitines may represent a risk factor for lung injury in humans with dysfunctional fatty acid oxidation. 相似文献
106.
107.
Background
The pathways regulating the transition of mammalian cells from quiescence to proliferation are mediated by multiple miRNAs. Despite significant improvements in our understanding of miRNA targeting, the majority of miRNA regulatory networks are still largely unknown and require experimental validation.Results
Here we identified miR-503, miR-103, and miR-494 as negative regulators of proliferation in primary human cells. We experimentally determined their genome wide target profiles using RNA-induced silencing complex (RISC) immunoprecipitations and gene expression profiling. Analysis of the genome wide target profiles revealed evidence of extensive regulation of gene expression through non-canonical target pairing by miR-503. We identified the proto-oncogene DDHD2 as a target of miR-503 that requires pairing outside of the canonical 5′ seed region of miR-503, representing a novel mode of miRNA-target pairing. Further bioinformatics analysis implicated miR-503 and DDHD2 in breast cancer tumorigenesis.Conclusions
Our results provide an extensive genome wide set of targets for miR-503, miR-103, and miR-494, and suggest that miR-503 may act as a tumor suppressor in breast cancer by its direct non-canonical targeting of DDHD2.Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1279-9) contains supplementary material, which is available to authorized users. 相似文献108.
S. Agarwal, R. Gupta, V. K. Iyer, S. R. Mathur and R. Ray Cytopathological diagnosis of alveolar soft part sarcoma, a rare soft tissue neoplasm Objective: Alveolar soft part sarcoma (ASPS) is a rare soft tissue neoplasm, having various morphological mimics, especially on fine needle aspiration cytology (FNAC). Because no definite immunohistochemical markers are available to aid a correct diagnosis, knowledge of the cytomorphological features is essential for correct patient management. Cytological features of five cases of ASPS are discussed, along with the ultrastructural findings available in one of them. Methods: Cytology records from 1997 to 2009 were reviewed for cases with a diagnosis of ASPS on cytology. The histology slides of the cases were also assessed for confirmation of the diagnosis. All the slides were reviewed by three pathologists. Results: There were five cases of ASPS diagnosed on FNAC. Their cytological features were noted in detail. The diagnoses in all the cases were confirmed on histology, and ultrastructural findings available in one of them were also assessed. Conclusions: The knowledge of cytological features may aid in diagnosing this rare tumour correctly on FNA smears, thus enabling correct patient management. 相似文献
109.
Vishal Gupta Chitra Natarajan Kanika Kumar Radha Prasanna 《Journal of applied phycology》2011,23(1):73-81
A cyanobacterial strain (Anabaena laxa RPAN8) exhibiting fungicidal activity and β-1,3 and 1,4 endoglucanase activities was selected for identifying the gene(s)
involved. Functional analyses of the genomic library revealed that four clones (8, 64, 116, and 248) of RPAN8 exhibited fungicidal
activity and induced structural deformities in the cell wall of the growing mycelia of Pythium aphanidermatum. Higher expression of fungicidal and β-1,4 endoglucanase activities, along with low expression of β-1,3 endoglucanase activity,
was recorded in two E. coli clones (8 and 64). Clones 8 and 64 exhibited identical sequences while clones 116 and 248 were also similar. Bioinformatic
analyses were undertaken only for the two non-identical clones 8 and 116 which showed open reading frames (ORFs) of 348 (end 1) and 656 amino acid residues (end 2), respectively. The amino acid sequence analyses revealed that the end 1 encoding endoglucanases belonged to peptidase M20 family while end 2 showed significant similarities with several known genes. The putative promoters and ribosomal binding sites were identified
and amino acid exchanges were observed in both end 1 and 2. The presence of signal peptides of 24 and 20 amino acid residues respectively revealed the secretory nature of these
proteins. 相似文献
110.
Unperturbed mitosis is a prerequisite for the generation of two genetically identical daughter cells. Nucleolar-spindle associated protein (NuSAP) is an important mitotic regulator. The activity of NuSAP is essential for a variety of cellular events that occur during mitosis starting from spindle assembly to cytokinesis. In addition to playing crucial roles during mitosis, NuSAP has been in the spotlight recently due to different studies exhibiting its importance in embryogenesis and cancer. In this review, we have extensively mined the current literature and made connections between different studies involving NuSAP. Importantly, we have assembled data pertaining to NuSAP from several proteomic studies and analyzed it thoroughly. Our review focuses on the role of NuSAP in mitosis and cancer, and brings to light several unanswered questions regarding the regulation of NuSAP in mitosis and its role in carcinogenesis. 相似文献