全文获取类型
收费全文 | 7446篇 |
免费 | 1573篇 |
国内免费 | 959篇 |
专业分类
9978篇 |
出版年
2024年 | 101篇 |
2023年 | 356篇 |
2022年 | 368篇 |
2021年 | 511篇 |
2020年 | 462篇 |
2019年 | 423篇 |
2018年 | 336篇 |
2017年 | 367篇 |
2016年 | 305篇 |
2015年 | 316篇 |
2014年 | 415篇 |
2013年 | 519篇 |
2012年 | 327篇 |
2011年 | 368篇 |
2010年 | 291篇 |
2009年 | 375篇 |
2008年 | 388篇 |
2007年 | 395篇 |
2006年 | 336篇 |
2005年 | 322篇 |
2004年 | 277篇 |
2003年 | 283篇 |
2002年 | 209篇 |
2001年 | 172篇 |
2000年 | 149篇 |
1999年 | 149篇 |
1998年 | 120篇 |
1997年 | 104篇 |
1996年 | 112篇 |
1995年 | 99篇 |
1994年 | 97篇 |
1993年 | 78篇 |
1992年 | 81篇 |
1991年 | 77篇 |
1990年 | 56篇 |
1989年 | 56篇 |
1988年 | 43篇 |
1987年 | 51篇 |
1986年 | 45篇 |
1985年 | 62篇 |
1984年 | 41篇 |
1983年 | 34篇 |
1982年 | 54篇 |
1981年 | 41篇 |
1980年 | 28篇 |
1979年 | 26篇 |
1978年 | 30篇 |
1977年 | 29篇 |
1976年 | 21篇 |
1972年 | 17篇 |
排序方式: 共有9978条查询结果,搜索用时 18 毫秒
951.
Hui Yan Hui Li James Denney Christopher Daniels Krishna Singh Balvin Chua Charles Stuart Yi Caudle Ronald Hamdy Gene LeSage Deling Yin 《Biochemistry and Biophysics Reports》2016
Sepsis is an exaggerated systemic inflammatory response to persistent bacteria infection with high morbidity and mortality rate clinically. β-arrestin 2 modulates cell survival and cell death in different systems. However, the effect of β-arrestin 2 on sepsis-induced cardiac dysfunction is not yet known. Here, we show that β-arrestin 2 overexpression significantly enhances animal survival following cecal ligation and puncture (CLP)-induced sepsis. Importantly, overexpression of β-arrestin 2 in mice prevents CLP-induced cardiac dysfunction. Also, β-arrestin 2 overexpression dramatically attenuates CLP-induced myocardial gp130 and p38 mitogen-activated protein kinase (MAPK) phosphorylation levels following CLP. Therefore, β-arrestin 2 prevents CLP-induced cardiac dysfunction through gp130 and p38. These results suggest that modulation of β-arrestin 2 might provide a novel therapeutic approach to prevent cardiac dysfunction in patients with sepsis. 相似文献
952.
Summary Hydrostatic pressure applied to one end of a horizontalChara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca2+ concentrations, osmotic pressure, neutral red, TEA Cl–, and the Ca2+ channel blockers nifedipine and LaCl3. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends. 相似文献
953.
954.
Antibacterial activity of silkworm hemolymph after hemopoietic organ being injured with radiosurgery
Abstract: To study the effect of hemopoietic organs damage on hemocyte function and antibacterial activity of hemolymph, silkworm ( Bombyx mori ) larvae were locally irradiated with carbon ion beams (12 C5+ , 100 Gy), live and death ratio of hemocytes and antibacterial activity of hemolymph were investigated. For unirradiated controls, the ratio of died hemocytes hardly changed at the fifth instar, but for locally irradiated silkworms, with growth died hemocytes and low-functional hemocytes increased clearly, and reached an extremely significant level at the later stage of the fifth instar. For irradiated individuals, the phenolxidase activities and sterilization effect of hemolymph were clearly lower than those of controls. So it is considered that after irradiating hemopoietic organs with heavy ion beams, not only the number of hemocytes decreased but the function of hemocytes also dropped, and they at last lead to a decline in immunity. 相似文献
955.
Herein, we describe a novel technique for heterotopic abdominal heart-lung transplantation (HAHLT) in rats. The configuration of the transplant graft involves anastomosis of donor inferior vena cava (IVC) to recipient IVC, and donor ascending aorta (Ao) to recipient abdominal Ao. The right upper and middle lung lobes are preserved and function as conduits for blood flow from right heart to left heart.There are several advantages to using this technique, and it lends itself to a broad range of applications. Because the graft is transplanted in a configuration that allows for dyamic volume-loading, cardiac function may be directly assessed in vivo. The use of pressure-volume conductance catheters permits characterization of load-dependent and load-independent hemodynamic parameters. The graft may be converted to a loaded configuration by applying a clamp to the recipient’s infra-hepatic IVC. We describe modified surgical techniques for both donor and recipient operations, and an ideal myocardial protection strategy. Depending on the experimental aim, this model may be adapted for use in both acute and chronic studies of graft function, immunologic status, and variable ventricular loading conditions. The conducting airways to the transplanted lung are preserved, and allow for acute lung re-ventilation. This facilitates analysis of the effects of the mixed venous and arterial blood providing coronary perfusion to the graft.A limitation of this model is its technical complexity. There is a significant learning curve for new operators, who should ideally be mentored in the technique. A surgical training background is advantageous for those wishing to apply this model. Despite its complexity, we aim to present the model in a clear and easily applicable format. Because of the physiologic similarity of this model to orthotopic transplantation, and its broad range of study applications, the effort invested in learning the technique is likely to be worthwhile. 相似文献
956.
Nathachit Limjunyawong Jonathan Fallica Amritha Ramakrishnan Kausik Datta Matthew Gabrielson Maureen Horton Wayne Mitzner 《Journal of visualized experiments : JoVE》2015,(95)
The mouse is now the primary animal used to model a variety of lung diseases. To study the mechanisms that underlie such pathologies, phenotypic methods are needed that can quantify the pathologic changes. Furthermore, to provide translational relevance to the mouse models, such measurements should be tests that can easily be done in both humans and mice. Unfortunately, in the present literature few phenotypic measurements of lung function have direct application to humans. One exception is the diffusing capacity for carbon monoxide, which is a measurement that is routinely done in humans. In the present report, we describe a means to quickly and simply measure this diffusing capacity in mice. The procedure involves brief lung inflation with tracer gases in an anesthetized mouse, followed by a 1 min gas analysis time. We have tested the ability of this method to detect several lung pathologies, including emphysema, fibrosis, acute lung injury, and influenza and fungal lung infections, as well as monitoring lung maturation in young pups. Results show significant decreases in all the lung pathologies, as well as an increase in the diffusing capacity with lung maturation. This measurement of lung diffusing capacity thus provides a pulmonary function test that has broad application with its ability to detect phenotypic structural changes with most of the existing pathologic lung models. 相似文献
957.
J. Rother C. Richter L. Turco F. Knoch I. Mey S. Luther A. Janshoff E. Bodenschatz M. Tarantola 《Open biology》2015,5(6)
Electromechanical function of cardiac muscle depends critically on the crosstalk of myocytes with non-myocytes. Upon cardiac fibrosis, fibroblasts translocate into infarcted necrotic tissue and alter their communication capabilities. In the present in vitro study, we determined a multiple parameter space relevant for fibrotic cardiac tissue development comprising the following essential processes: (i) adhesion to substrates with varying elasticity, (ii) dynamics of contractile function, and (iii) electromechanical connectivity. By combining electric cell-substrate impedance sensing (ECIS) with conventional optical microscopy, we could measure the impact of fibroblast–cardiomyocyte ratio on the aforementioned parameters in a non-invasive fashion. Adhesion to electrodes was quantified via spreading rates derived from impedance changes, period analysis allowed us to measure contraction dynamics and modulations of the barrier resistance served as a measure of connectivity. In summary, we claim that: (i) a preferred window for substrate elasticity around 7 kPa for low fibroblast content exists, which is shifted to stiffer substrates with increasing fibroblast fractions. (ii) Beat frequency decreases nonlinearly with increasing fraction of fibroblasts, while (iii) the intercellular resistance increases with a maximal functional connectivity at 75% fibroblasts. For the first time, cardiac cell–cell junction density-dependent connectivity in co-cultures of cardiomyocytes and fibroblasts was quantified using ECIS. 相似文献
958.
959.
Esther C. Maier Ankur Saxena Berta Alsina Marianne E. Bronner Tanya T. Whitfield 《Developmental biology》2014
For both the intricate morphogenetic layout of the sensory cells in the ear and the elegantly radial arrangement of the sensory neurons in the nose, numerous signaling molecules and genetic determinants are required in concert to generate these specialized neuronal populations that help connect us to our environment. In this review, we outline many of the proteins and pathways that play essential roles in the differentiation of otic and olfactory neurons and their integration into their non-neuronal support structures. In both cases, well-known signaling pathways together with region-specific factors transform thickened ectodermal placodes into complex sense organs containing numerous, diverse neuronal subtypes. Olfactory and otic placodes, in combination with migratory neural crest stem cells, generate highly specialized subtypes of neuronal cells that sense sound, position and movement in space, odors and pheromones throughout our lives. 相似文献
960.
Catherine Michaux Jenny Pouyez Aurélie Mayard Pierre Vandurm Isabelle Housen Johan Wouters 《Biochimie》2010
In this study, the crystal structure of a novel endo-1,4-β-xylanase from Scytalidium acidophilum, XYL1, was solved at 1.9 Å resolution. This is one of the few solved crystal structures of acidophilic proteins. The enzyme has the overall fold typical to family 11 xylanases. Comparison of this structure with other homologous acidophilic, neutrophilic and alkalophilic xylanases provides additional insights into the general features involved in low pH adaptation (stability and activity). Several sequence and structure modifications appeared to be responsible for the acidophilic characteristic: (a) the presence of an aspartic acid H bonded to the acid/base catalyst (b) the nature of specifically conserved residues in the active site (c) the negative potential at the surface (d) the decreased number of salt bridges and H bonds in comparison with highly alkaline enzymes. 相似文献