全文获取类型
收费全文 | 4783篇 |
免费 | 322篇 |
国内免费 | 246篇 |
出版年
2024年 | 27篇 |
2023年 | 68篇 |
2022年 | 72篇 |
2021年 | 65篇 |
2020年 | 96篇 |
2019年 | 127篇 |
2018年 | 187篇 |
2017年 | 104篇 |
2016年 | 115篇 |
2015年 | 109篇 |
2014年 | 294篇 |
2013年 | 329篇 |
2012年 | 202篇 |
2011年 | 338篇 |
2010年 | 293篇 |
2009年 | 353篇 |
2008年 | 388篇 |
2007年 | 397篇 |
2006年 | 301篇 |
2005年 | 233篇 |
2004年 | 190篇 |
2003年 | 185篇 |
2002年 | 152篇 |
2001年 | 110篇 |
2000年 | 87篇 |
1999年 | 84篇 |
1998年 | 61篇 |
1997年 | 37篇 |
1996年 | 29篇 |
1995年 | 36篇 |
1994年 | 27篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 22篇 |
1990年 | 15篇 |
1989年 | 21篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 6篇 |
1973年 | 3篇 |
1972年 | 5篇 |
排序方式: 共有5351条查询结果,搜索用时 31 毫秒
101.
102.
【背景】乳链菌肽主要是由乳酸乳球菌生产的一类多肽,对革兰氏阳性菌有抑菌作用,是目前联合国粮食及农业组织/世界卫生组织唯一批准使用的天然食品防腐剂。但是其产量低、缺乏简便高效的检测方法,限制了其研究和应用。【目的】构建一种可输出肉眼可见红色荧光的细胞分子传感器,以期能简单方便地检测样品中的乳链菌肽,同时应用该传感器筛选乳链菌肽生产菌株。【方法】用Golden-Gate克隆方法构建含乳链菌肽诱导启动子和下游红色荧光蛋白基因(两种)的载体,转入Lactococcus lactis中。用细胞传感器筛选可能的乳链菌肽生产菌株。【结果】构建的两种乳链菌肽细胞分子传感器都能对2?200 ng/mL乳链菌肽有灵敏的响应,可用于定量测定。两种传感器的最大荧光强度和表型也有所不同。利用细胞传感器确定了Lactococcus lactis ATCC 11454乳链菌肽的产生,同时排除了一个能产其他抗菌化合物的菌株。【结论】构建的细胞分子传感器能特异性地响应乳链菌肽,并能简单快速地筛选乳链菌肽菌株。 相似文献
103.
Srabani Bhaumik Jean Boyer Chaitali Banerjee Samantha Clark Noemi Sebastiao Elizabeth Vela Penny Towne 《Journal of cellular biochemistry》2020,121(12):4974-4990
In preclinical cancer studies, three-dimensional (3D) cell spheroids and aggregates are preferred over monolayer cell cultures due to their architectural and functional similarity to solid tumors. We performed a proof-of-concept study to generate physiologically relevant and predictive preclinical models using non–small cell lung adenocarcinoma, and colon and colorectal adenocarcinoma cell line-derived 3D spheroids and aggregates. Distinct panels were designed to determine the expression profiles of frequently studied biomarkers of the two cancer subtypes. The lung adenocarcinoma panel included ALK, EGFR, TTF-1, and CK7 biomarkers, and the colon and colorectal adenocarcinoma panel included BRAF V600E, MSH2, MSH6, and CK20. Recent advances in immunofluorescence (IF) multiplexing and imaging technology enable simultaneous detection and quantification of multiple biomarkers on a single slide. In this study, we performed IF staining of multiple biomarkers per section on formalin-fixed paraffin-embedded 3D spheroids and aggregates. We optimized protocol parameters for automated IF and demonstrated staining concordance with automated chromogenic immunohistochemistry performed with validated protocols. Next, post-acquisition spectral unmixing of the captured fluorescent signals were utilized to delineate four differently stained biomarkers within a single multiplex IF image, followed by automated quantification of the expressed markers. This workflow has the potential to be adapted to preclinical high-throughput screening and drug efficacy studies utilizing 3D spheroids from cancer cell lines and patient-derived organoids. The process allows for cost, time, and resource savings through concurrent staining of several biomarkers on a single slide, the ability to study the interactions of multiple expressed proteins within a single region of interest, and enable quantitative assessment of biomarkers in cancer cells. 相似文献
104.
Zahra Khoshbin Mohammad Izadyar Mohammad Reza Bozorgmehr Asma Verdian 《Journal of biomolecular structure & dynamics》2020,38(12):3659-3675
AbstractThe aptamers with the ability to form a G-quadruplex structure can be stable in the presence of some ions. Hence, study of the interactions between such aptamers and ions can be beneficial to determine the highest selective aptamer toward an ion. In this article, molecular dynamics (MD) simulations and quantum mechanics (QM) calculations have been applied to investigate the selectivity of the T30695 aptamer toward Pb2+ in comparison with some ions. The Free Energy Landscape (FEL) analysis indicates that Pb2+ has remained inside the aptamer during the MD simulation, while the other ions have left it. The Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) binding energies prove that the conformational stability of the aptamer is the highest in the presence of Pb2+. According to the compaction parameters, the greatest compressed ion-aptamer complex, and hence, the highest ion-aptamer interaction have been induced in the presence of Pb2+. The contact maps clarify the closer contacts between the nucleotides of the aptamer in the presence of Pb2+. The density functional theory (DFT) results show that Pb2+ forms the most stable complex with the aptamer, which is consistent with the MD results. The QM calculations reveal that the N-H bonds and the O…H distances are the longest and the shortest, respectively, in the presence of Pb2+. The obtained results verify that the strongest hydrogen bonds (HBs), and hence, the most compressed aptamer structure are induced by Pb2+. Besides, atoms in molecules (AIM) and natural bond orbital (NBO) analyses confirm the results.Communicated by Ramaswamy H. Sarma 相似文献
105.
Shubham Srivastava Pakhuri Mehta Omprakash Sharma Manish Sharma 《Journal of biomolecular structure & dynamics》2020,38(14):4179-4188
Abstract Chemical entities targeting kinase signalling pathways serve as a potential strategy to combat malignancies. Protein Kinase B or Akt is a validated target for various malignancies and Akt3 remains the least explored isoform among all its isoforms. Initially, homology modelling technique was used for generating protein structure and further validation was performed using molecular dynamics simulation and Ramachandran plot. The validated protein structure was then subjected for active site analysis which led to identification of active site residues based on metrics provided by site score. The important residues in binding site were identified as Thr81, Asp271 and Asp289 for binding energetics and inhibition. Subsequently, virtual screening methodologies were used for identification of novel hits for inhibition of Protein Kinase B or Akt3. This led to the identification of two hits, i.e. thiophene derivative and thieno-pyridine derivative which were selected on the basis of their binding affinity and drug likeliness. These identified hits were subjected for molecular dynamics simulations, quantum mechanical and synthetic accessibility studies. The role of crucial residues in binding site stood validated as suggested by molecular dynamics simulations studies. Communicated by Ramaswamy H. Sarma 相似文献
106.
Ol’ha O. Brovarets’ 《Journal of biomolecular structure & dynamics》2020,38(10):2817-2836
AbstractThis paper focuses on the comprehensive conformational analysis of the quercetin molecule with a broad range of the therapeutic and biological actions. All possible conformers of these molecule, corresponding to the local minima on the potential energy hypersurface, have been obtained by the sequential rotation of its five hydroxyl groups and also by the rotation of its (A?+?C) and B rings relatively each other. Altogether, it was established 48 stable conformers, among which 24 conformers possess planar structure and 24 conformers – nonplanar structure. Their structural, symmetrical, energetical and polar characteristics have been investigated in details. Quantum-mechanical calculations indicate that conformers of the quercetin molecule are polar structures with a dipole moment, which varies within the range from 0.35 to 9.87 Debay for different conformers. Relative Gibbs free energies of these conformers are located within the range from 0.0 to 25.3?kcal·mol?1 in vacuum under normal conditions. Impact of the continuum with ε?=?4 leads to the decreasing of the Gibbs free energies (–0.19–18.15?kcal·mol?1) and increasing of the dipole moment (0.57–12.48?D). It was shown that conformers of the quercetin molecule differ from each other by the intramolecular specific contacts (two or three), stabilizing all possible conformers of the molecule – H-bonds (both classical ОН…О and so-called unusual С′Н…О and ОН…С′) and attractive van-der-Waals contacts О…О. Obtained conformational analysis for the quercetin molecule enables to provide deeper understanding of the ‘structure-function’ relationship and also to suggest its mechanisms of the therapeutic and biological actions.Communicated by Ramaswamy H. Sarma 相似文献
107.
Julia S. Markl Werner E. G. Müller Dayane Sereno Tarek A. Elkhooly Maria Kokkinopoulou Johan Gardères Frank Depoix Matthias Wiens 《Biotechnology and bioengineering》2020,117(6):1789-1804
During evolution, sponges (Porifera) have honed the genetic toolbox and biosynthetic mechanisms for the fabrication of siliceous skeletal components (spicules). Spicules carry a protein scaffold embedded within biogenic silica (biosilica) and feature an amazing range of optical, structural, and mechanical properties. Thus, it is tempting to explore the low-energy synthetic pathways of spiculogenesis for the fabrication of innovative hybrid materials. In this synthetic biology approach, the uptake of multifunctional nonbiogenic nanoparticles (fluorescent, superparamagnetic) by spicule-forming cells of bioreactor-cultivated sponge primmorphs provides access to spiculogenesis. The ingested nanoparticles were detected within intracellular vesicles resembling silicasomes (silica-rich cellular compartments) and as cytosolic clusters where they lent primmorphs fluorescent/magnetic properties. During spiculogenesis, the nanoparticles initially formed an incomplete layer around juvenile, intracellular spicules. In the mature, extracellular spicules the nanoparticles were densely arranged as a surface layer that rendered the resulting composite fluorescent and magnetic. By branching off the conventional route of solid-state materials synthesis under harsh conditions, a new pathway has been opened to a versatile platform that allows adding functionalities to growing spicules as templates in living cells, using nonbiogenic nanoscale building blocks with multiple functionalities. The magnet-assisted alignment renders this composite with its fluorescent/magnetic properties potentially suitable for application in biooptoelectronics and microelectronics (e.g., microscale on-chip waveguides for applications of optical detection and sensing). 相似文献
108.
Quantum biology is emerging as a new field at the intersection between fundamental physics and biology, promising novel insights into the nature and origin of biological order. We discuss several elements of QBCL (quantum biology at cellular level) – a research program designed to extend the reach of quantum concepts to higher than molecular levels of biological organization. We propose a new general way to address the issue of environmentally induced decoherence and macroscopic superpositions in biological systems, emphasizing the ‘basis-dependent’ nature of these concepts. We introduce the notion of ‘formal superposition’ and distinguish it from that of Schroedinger's cat (i.e., a superposition of macroscopically distinct states). Whereas the latter notion presents a genuine foundational problem, the former one contradicts neither common sense nor observation, and may be used to describe cellular ‘decision-making’ and adaptation. We stress that the interpretation of the notion of ‘formal superposition’ should involve non-classical correlations between molecular events in a cell. Further, we describe how better understanding of the physics of Life can shed new light on the mechanism driving evolutionary adaptation (viz., ‘Basis-Dependent Selection’, BDS). Experimental tests of BDS and the potential role of synthetic biology in closing the ‘evolvability mechanism’ loophole are also discussed. 相似文献
109.
Atanas G. Atanasov Jian N. Wang Shi P. Gu Jing Bu Matthias P. Kramer Lisa Baumgartner Nanang Fakhrudin Angela Ladurner Clemens Malainer Anna Vuorinen Stefan M. Noha Stefan Schwaiger Judith M. Rollinger Daniela Schuster Hermann Stuppner Verena M. Dirsch Elke H. Heiss 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Peroxisome proliferator-activated receptor gamma (PPARγ) agonists are clinically used to counteract hyperglycemia. However, so far experienced unwanted side effects, such as weight gain, promote the search for new PPARγ activators.Methods
We used a combination of in silico, in vitro, cell-based and in vivo models to identify and validate natural products as promising leads for partial novel PPARγ agonists.Results
The natural product honokiol from the traditional Chinese herbal drug Magnolia bark was in silico predicted to bind into the PPARγ ligand binding pocket as dimer. Honokiol indeed directly bound to purified PPARγ ligand-binding domain (LBD) and acted as partial agonist in a PPARγ-mediated luciferase reporter assay. Honokiol was then directly compared to the clinically used full agonist pioglitazone with regard to stimulation of glucose uptake in adipocytes as well as adipogenic differentiation in 3T3-L1 pre-adipocytes and mouse embryonic fibroblasts. While honokiol stimulated basal glucose uptake to a similar extent as pioglitazone, it did not induce adipogenesis in contrast to pioglitazone. In diabetic KKAy mice oral application of honokiol prevented hyperglycemia and suppressed weight gain.Conclusion
We identified honokiol as a partial non-adipogenic PPARγ agonist in vitro which prevented hyperglycemia and weight gain in vivo.General significance
This observed activity profile suggests honokiol as promising new pharmaceutical lead or dietary supplement to combat metabolic disease, and provides a molecular explanation for the use of Magnolia in traditional medicine. 相似文献110.
Sylvain Hanein Mathilde Garcia Lucas Fares-Taie Valérie Serre Yves De Keyzer Thierry Delaveau Isabelle Perrault Nathalie Delphin Sylvie Gerber Alain Schmitt Jean-Marc Masse Arnold Munnich Josseline Kaplan Frédéric Devaux Jean-Michel Rozet 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013