全文获取类型
收费全文 | 4559篇 |
免费 | 274篇 |
出版年
2023年 | 22篇 |
2022年 | 55篇 |
2021年 | 100篇 |
2020年 | 60篇 |
2019年 | 79篇 |
2018年 | 115篇 |
2017年 | 73篇 |
2016年 | 142篇 |
2015年 | 221篇 |
2014年 | 245篇 |
2013年 | 355篇 |
2012年 | 398篇 |
2011年 | 340篇 |
2010年 | 220篇 |
2009年 | 198篇 |
2008年 | 303篇 |
2007年 | 285篇 |
2006年 | 277篇 |
2005年 | 257篇 |
2004年 | 209篇 |
2003年 | 224篇 |
2002年 | 171篇 |
2001年 | 49篇 |
2000年 | 34篇 |
1999年 | 36篇 |
1998年 | 37篇 |
1997年 | 33篇 |
1996年 | 29篇 |
1995年 | 28篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 26篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 11篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1964年 | 5篇 |
排序方式: 共有4833条查询结果,搜索用时 15 毫秒
991.
992.
MariaLisa Garavaglia Silvia Dopinto Markus Ritter Johannes Fürst Stefano Saino Fabiana Guizzardi Martin Jakab Claudia Bazzini Valeria Vezzoli Silvia Dossena Simona Rodighiero Chiara Sironi Guido Bottà Giuliano Meyer Robert M Henderson Markus Paulmichl 《Cellular physiology and biochemistry》2004,14(4-6):231-240
The plasma membrane is a highly dynamic cell-barrier if the nature and distribution of its constituents are considered. Ion channels are embedded in these double lipid bilayers, which modulate their 3D-structures. The structure modulations by the lipid bilayer can assume such a degree that channel activation depends on them, as was shown for the KcsA potassium channel. Here we show that the cation-over-anion selectivity of reconstituted ICln channels can be varied by the thickness of a bilayer build of phosphatidylcholines. The shorter the acyl-chains and therefore the thinner the bilayers of the membrane are, the more potassium selective the channels are. In contrast, the longer the acyl-chains and therefore the thicker the membranes are, the more chloride selective the channels become. 相似文献
993.
Giuliano Bonanomi Salvatore A. Gaglione Vincenzo Antignani Gaspare Cesarano 《Plant and Soil》2016,403(1-2):37-51
Background and Aims
Soil water repellency (SWR, i.e. the reduced affinity for water due to the presence of hydrophobic coatings on soil particles) has relevant hydrological implications on the rate of water infiltration, surface runoff, and overland flow. Here, we test how SWR varies along a 2490 m altitudinal gradient encompassing six ecosystems including Mediterranean, Temperate, and Alpine vegetation types.Methods
Water repellency, measured by the Molarity of an Ethanol Droplet (MED) test, was quantified in 80 soil samples collected for 16 different elevations. Soil quality was assessed by measuring soil texture, pH, organic carbon, salinity, and nutrient availability.Results
SWR showed a unimodal pattern along the 2490 m transect, peaking at intermediate elevations. Unexpectedly, SWR was the highest under broad-leaf deciduous forests, and the lowest under evergreen, sclerophyllous Mediterranean vegetation types. The soil organic carbon content, and the pH were the main determinants of water repellency, showing respectively a positive, and a negative correlation with the SWR. In contrast, soil texture and salinity resulted unrelated to the SWR.Conclusions
With this study we demonstrated a linkage between SWR, vegetation type and soil pH and organic carbon content along the elevation gradient. Further studies are needed to explicitly evaluate the impact SRW on erosion risk at catchment scale in the context of climatic change.994.
995.
996.
997.
998.
Molecularly imprinted polymers coupled to matrix assisted laser desorption ionization mass spectrometry for femtomoles detection of cardiac troponin I peptides
下载免费PDF全文
![点击此处可从《Journal of molecular recognition : JMR》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mirko Busato Graziano Guella Alessandra Maria Bossi 《Journal of molecular recognition : JMR》2016,29(1):41-50
Molecularly imprinted polymers (MIPs) were combined to MALDI‐TOF‐MS to evaluate a selective enrichment (SE) method for the determination of clinically relevant biomarkers from complex biological samples. The concept was proven with the myocardial injury marker Troponin I (cTnI). In a first part, MIP materials entailed for the recognition of cTnI epitopes (three peptides selected) were prepared and characterized in dimensions (0.7–2μm), dissociation constants (58–817 nM), kinetics of binding (5–60 min), binding capacity (ca. 1.5 µg/mg polymer), imprinting factors (3 > IF > 5) and selectivity for the peptide epitope. Then, the MIPs, incubated with cTnI peptides and spotted on the target with the DHB matrix, were assayed for the desorption of the peptides in MALDI‐TOF‐MS. The measured detection limit was ca. 300 femtomols. Finally, the MIP‐SE MALDI‐TOF‐MS was tested for its ability to enrich in the cTnI peptides from a complex sample, mimic of serum (i.e. 81 peptides of digested albumin). The MIP‐SE MALDI‐TOF‐MS successfully enriched in cTnI peptides from the complex sample proving the technique could offer a flexible platform to prepare entailed materials suitable for diagnostic purposes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
999.
ASPM and CITK regulate spindle orientation by affecting the dynamics of astral microtubules
下载免费PDF全文
![点击此处可从《EMBO reports》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marta Gai Federico T Bianchi Cristiana Vagnoni Fiammetta Vernì Silvia Bonaccorsi Selina Pasquero Gaia E Berto Francesco Sgrò Alessandra MA Chiotto Laura Annaratone Anna Sapino Anna Bergo Nicoletta Landsberger Jacqueline Bond Wieland B Huttner Ferdinando Di Cunto 《EMBO reports》2016,17(10):1396-1409
Correct orientation of cell division is considered an important factor for the achievement of normal brain size, as mutations in genes that affect this process are among the leading causes of microcephaly. Abnormal spindle orientation is associated with reduction of the neuronal progenitor symmetric divisions, premature cell cycle exit, and reduced neurogenesis. This mechanism has been involved in microcephaly resulting from mutation of ASPM, the most frequently affected gene in autosomal recessive human primary microcephaly (MCPH), but it is presently unknown how ASPM regulates spindle orientation. In this report, we show that ASPM may control spindle positioning by interacting with citron kinase (CITK), a protein whose loss is also responsible for severe microcephaly in mammals. We show that the absence of CITK leads to abnormal spindle orientation in mammals and insects. In mouse cortical development, this phenotype correlates with increased production of basal progenitors. ASPM is required to recruit CITK at the spindle, and CITK overexpression rescues ASPM phenotype. ASPM and CITK affect the organization of astral microtubules (MT), and low doses of MT‐stabilizing drug revert the spindle orientation phenotype produced by their knockdown. Finally, CITK regulates both astral‐MT nucleation and stability. Our results provide a functional link between two established microcephaly proteins. 相似文献
1000.
Ultrastructure of the liver microcirculation influences hepatic and systemic insulin activity and provides a mechanism for age‐related insulin resistance
下载免费PDF全文
![点击此处可从《Aging cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mashani Mohamad Sarah Jayne Mitchell Lindsay Edward Wu Melanie Yvonne White Stuart James Cordwell John Mach Samantha Marie Solon‐Biet Dawn Boyer Dawn Nines Abhirup Das Shi‐Yun Catherine Li Alessandra Warren Sarah Nicole Hilmer Robin Fraser David Andrew Sinclair Stephen James Simpson Rafael de Cabo David George Le Couteur Victoria Carroll Cogger 《Aging cell》2016,15(4):706-715
While age‐related insulin resistance and hyperinsulinemia are usually considered to be secondary to changes in muscle, the liver also plays a key role in whole‐body insulin handling and its role in age‐related changes in insulin homeostasis is largely unknown. Here, we show that patent pores called ‘fenestrations’ are essential for insulin transfer across the liver sinusoidal endothelium and that age‐related loss of fenestrations causes an impaired insulin clearance and hyperinsulinemia, induces hepatic insulin resistance, impairs hepatic insulin signaling, and deranges glucose homeostasis. To further define the role of fenestrations in hepatic insulin signaling without any of the long‐term adaptive responses that occur with aging, we induced acute defenestration using poloxamer 407 (P407), and this replicated many of the age‐related changes in hepatic glucose and insulin handling. Loss of fenestrations in the liver sinusoidal endothelium is a hallmark of aging that has previously been shown to cause deficits in hepatic drug and lipoprotein metabolism and now insulin. Liver defenestration thus provides a new mechanism that potentially contributes to age‐related insulin resistance. 相似文献