全文获取类型
收费全文 | 4049篇 |
免费 | 380篇 |
国内免费 | 3篇 |
出版年
2023年 | 27篇 |
2022年 | 51篇 |
2021年 | 132篇 |
2020年 | 79篇 |
2019年 | 92篇 |
2018年 | 115篇 |
2017年 | 106篇 |
2016年 | 171篇 |
2015年 | 309篇 |
2014年 | 277篇 |
2013年 | 271篇 |
2012年 | 445篇 |
2011年 | 359篇 |
2010年 | 230篇 |
2009年 | 188篇 |
2008年 | 269篇 |
2007年 | 240篇 |
2006年 | 197篇 |
2005年 | 191篇 |
2004年 | 134篇 |
2003年 | 130篇 |
2002年 | 108篇 |
2001年 | 18篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 29篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1985年 | 5篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1972年 | 4篇 |
1969年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有4432条查询结果,搜索用时 15 毫秒
121.
Tomá? Venit Rastislav Dzijak Al?běta Kalendová Michal Kahle Jana Roho?ková Volker Schmidt Thomas Rülicke Birgit Rathkolb Wolfgang Hans Alexander Bohla Oliver Eickelberg Tobias Stoeger Eckhard Wolf Ali ?nder Yildirim Valérie Gailus-Durner Helmut Fuchs Martin Hrabě de Angelis Pavel Hozák 《PloS one》2013,8(4)
122.
Phuti E. Makgotlho Gabriella Marincola Daniel Sch?fer Qian Liu Taeok Bae Tobias Geiger Elizabeth Wasserman Christiane Wolz Wilma Ziebuhr Bhanu Sinha 《PloS one》2013,8(8)
The Staphylococcus aureus regulatory saePQRS system controls the expression of numerous virulence factors, including extracellular adherence protein (Eap), which amongst others facilitates invasion of host cells. The saePQRS operon codes for 4 proteins: the histidine kinase SaeS, the response regulator SaeR, the lipoprotein SaeP and the transmembrane protein SaeQ. S. aureus strain Newman has a single amino acid substitution in the transmembrane domain of SaeS (L18P) which results in constitutive kinase activity. SDS was shown to be one of the signals interfering with SaeS activity leading to inhibition of the sae target gene eap in strains with SaeSL but causing activation in strains containing SaeSP. Here, we analyzed the possible involvement of the SaeP protein and saePQ region in SDS-mediated sae/eap expression. We found that SaePQ is not needed for SDS-mediated SaeS signaling. Furthermore, we could show that SaeS activity is closely linked to the expression of Eap and the capacity to invade host cells in a number of clinical isolates. This suggests that SaeS activity might be directly modulated by structurally non-complex environmental signals, as SDS, which possibly altering its kinase/phosphatase activity. 相似文献
123.
Felix C. Ringshausen Andrés de Roux Mathias W. Pletz Nina H?m?l?inen Tobias Welte Jessica Rademacher 《PloS one》2013,8(8)
Background
Representative population-based data on the epidemiology of bronchiectasis in Europe are limited. The aim of the present study was to investigate the current burden and the trends of bronchiectasis-associated hospitalizations and associated conditions in Germany in order to inform focused patient care and to facilitate the allocation of healthcare resources.Methods
The nationwide diagnosis-related groups hospital statistics for the years 2005–2011 were used in order to identify hospitalizations with bronchiectasis as any hospital discharge diagnosis according to the International Classification of Diseases, 10th revision, code J47, (acquired) bronchiectasis. Poisson log-linear regression analysis was used to assess the significance of trends. In addition, the overall length of hospital stay (LOS) and the in-hospital mortality in comparison to the nationwide overall mortality due to bronchiectasis as the primary diagnosis was assessed.Results
Overall, 61,838 records with bronchiectasis were extracted from more than 125 million hospitalizations. The average annual age-adjusted rate for bronchiectasis as any diagnosis was 9.4 hospitalizations per 100,000 population. Hospitalization rates increased significantly during the study period, with the highest rate of 39.4 hospitalizations per 100,000 population among men aged 75–84 years and the most pronounced average annual increases among females. Besides numerous bronchiectasis-associated conditions, chronic obstructive pulmonary disease (COPD) was most frequently found in up to 39.2% of hospitalizations with bronchiectasis as the primary diagnosis. The mean LOS was comparable to that for COPD. Overall, only 40% of bronchiectasis-associated deaths occurred inside the hospital.Conclusions
The present study provides evidence of a changing epidemiology and a steadily increasing prevalence of bronchiectasis-associated hospitalizations. Moreover, it confirms the diversity of bronchiectasis-associated conditions and the possible association between bronchiectasis and COPD. As the major burden of disease may be managed out-of-hospital, prospective patient registries are needed to establish the exact prevalence of bronchiectasis according to the specific underlying condition. 相似文献124.
Yoshihiro Kawano Christopher Higgins Yasuhito Yamamoto Julie Nyhus Amy Bernard Hong-Wei Dong Harvey J. Karten Tobias Schilling 《PloS one》2013,8(3)
We present a new method for whole slide darkfield imaging. Whole Slide Imaging (WSI), also sometimes called virtual slide or virtual microscopy technology, produces images that simultaneously provide high resolution and a wide field of observation that can encompass the entire section, extending far beyond any single field of view. For example, a brain slice can be imaged so that both overall morphology and individual neuronal detail can be seen. We extended the capabilities of traditional whole slide systems and developed a prototype system for darkfield internal reflection illumination (DIRI). Our darkfield system uses an ultra-thin light-emitting diode (LED) light source to illuminate slide specimens from the edge of the slide. We used a new type of side illumination, a variation on the internal reflection method, to illuminate the specimen and create a darkfield image. This system has four main advantages over traditional darkfield: (1) no oil condenser is required for high resolution imaging (2) there is less scatter from dust and dirt on the slide specimen (3) there is less halo, providing a more natural darkfield contrast image, and (4) the motorized system produces darkfield, brightfield and fluorescence images. The WSI method sometimes allows us to image using fewer stains. For instance, diaminobenzidine (DAB) and fluorescent staining are helpful tools for observing protein localization and volume in tissues. However, these methods usually require counter-staining in order to visualize tissue structure, limiting the accuracy of localization of labeled cells within the complex multiple regions of typical neurohistological preparations. Darkfield imaging works on the basis of light scattering from refractive index mismatches in the sample. It is a label-free method of producing contrast in a sample. We propose that adapting darkfield imaging to WSI is very useful, particularly when researchers require additional structural information without the use of further staining. 相似文献
125.
The proportion in which carbon and growth-limiting nutrients are exported from the oceans’ productive surface layer to the deep sea is a crucial parameter in models of the biological carbon pump. Based on >400 vertical flux observations of particulate organic carbon (POC) and nitrogen (PON) from the European Arctic Ocean we show the common assumption of constant C:N stoichiometry not to be met. Exported POC:PON ratios exceeded the classical Redfield atomic ratio of 6.625 in the entire region, with the largest deviation in the deep Central Arctic Ocean. In this part the mean exported POC:PON ratio of 9.7 (a:a) implies c. 40% higher carbon export compared to Redfield-based estimates. When spatially integrated, the potential POC export in the European Arctic was 10–30% higher than suggested by calculations based on constant POC:PON ratios. We further demonstrate that the exported POC:PON ratio varies regionally in relation to nitrate-based new production over geographical scales that range from the Arctic to the subtropics, being highest in the least productive oligotrophic Central Arctic Ocean and subtropical gyres. Accounting for variations in export stoichiometry among systems of different productivity will improve the ability of models to resolve regional patterns in carbon export and, hence, the oceans’ contribution to the global carbon cycle will be predicted more accurately. 相似文献
126.
127.
Monica Rolando Serena Sanulli Christophe Rusniok Laura Gomez-Valero Clement Bertholet Tobias Sahr Raphael Margueron Carmen Buchrieser 《Cell host & microbe》2013,13(4):395-405
- Download : Download high-res image (266KB)
- Download : Download full-size image
128.
John T. Heiker Matthias Kern Joanna Kosacka Gesine Flehmig Michael Stumvoll Edward Shang Tobias Lohmann Miriam Dreßler Peter Kovacs Matthias Blüher Nora Klöting 《Obesity (Silver Spring, Md.)》2013,21(3):529-534
Objective:
A spontaneous deletion in the nicotinamide nucleotide transhydrogenase (Nnt) gene eliminating exons 7‐11 in C57BL/6J (B6J) mice is associated with reduced glucose‐stimulated insulin secretion in vitro, impaired glucose tolerance, higher epigonadal fat mass, and altered susceptibility to diet induced obesity of male B6J mice was proposed. A potential implication for NNT in human adipose tissue distribution has not been investigated so far.Design and Methods:
Therefore, NNT mRNA expression in paired human samples of visceral (vis) and subcutaneous (sc) adipose tissue from 221 subjects with a wide range of body mass index (BMI), insulin sensitivity, and glucose tolerance was analyzed.Results:
NNT mRNA expression is significantly higher in visceral fat of obese patients and correlates with body weight, BMI, % body fat, visceral and sc fat area, waist and hip circumference, and fasting plasma insulin (FPI). Multivariate linear regression analysis revealed visceral NNT expression as age and gender independent predictor of BMI, waist circumference, visceral fat area, and % body fat, but not FPI and 2 h OGTT glucose.Conclusion:
In conclusion, a functional relevance of NNT in the development of human obesity and visceral fat distribution was suggested here. 相似文献129.
Epigenetic dysregulation in the developing Down syndrome cortex 总被引:1,自引:0,他引:1
Nady El Hajj Marcus Dittrich Julia Böck Theo F. J. Kraus Indrajit Nanda Tobias Müller 《Epigenetics》2016,11(8):563-578
130.
Real‐Time Investigation of Intercalation and Structure Evolution in Printed Polymer:Fullerene Bulk Heterojunction Thin Films
下载免费PDF全文
![点击此处可从《Liver Transplantation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Thaer Kassar Nusret S. Güldal Marvin Berlinghof Tayebeh Ameri Andreas Kratzer Bob C. Schroeder Giovanni Li Destri Andreas Hirsch Martin Heeney Iain McCulloch Christoph J. Brabec Tobias Unruh 《Liver Transplantation》2016,6(5)
The complex intermixing morphology is critical for the performance of the nanostructured polymer:fullerene bulk heterojunction (BHJ) solar cells. Here, time resolved in situ grazing incidence X‐ray diffraction and grazing incidence small angle X‐ray scattering are used to track the structure formation of BHJ thin films formed from the donor polymer poly(2,5‐bis(3‐hexadecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) with different fullerene derivative acceptors. The formation of stable bimolecular crystals through the intercalation of fullerene molecules between the side chains of polymer crystallites is investigated. Such systems exhibit more efficient exciton dissociation but lower photo‐conductance and faster decay of charges. On the basis of the experimental observations, intercalation obviously takes place before or with the formation of the crystalline polymer domains. It results in more stable structures whose volume remains constant upon further drying. Three distinct periods of drying are observed and the formation of unidimensional fullerene channels along the π‐stacking direction of polymer crystallites is confirmed. 相似文献