全文获取类型
收费全文 | 2286篇 |
免费 | 225篇 |
国内免费 | 2篇 |
专业分类
2513篇 |
出版年
2024年 | 4篇 |
2023年 | 35篇 |
2022年 | 98篇 |
2021年 | 156篇 |
2020年 | 66篇 |
2019年 | 81篇 |
2018年 | 79篇 |
2017年 | 66篇 |
2016年 | 110篇 |
2015年 | 174篇 |
2014年 | 155篇 |
2013年 | 167篇 |
2012年 | 208篇 |
2011年 | 174篇 |
2010年 | 102篇 |
2009年 | 100篇 |
2008年 | 129篇 |
2007年 | 92篇 |
2006年 | 96篇 |
2005年 | 72篇 |
2004年 | 55篇 |
2003年 | 49篇 |
2002年 | 57篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1980年 | 3篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1967年 | 3篇 |
1966年 | 3篇 |
1955年 | 4篇 |
1946年 | 2篇 |
1926年 | 2篇 |
排序方式: 共有2513条查询结果,搜索用时 15 毫秒
71.
Jürgen Schymeinsky Hannah Mayer Christopher Tomsic Cornelia Tilp John D. Schuetz Yunhai Cui Lutz Wollin Florian Gantner Klaus J. Erb 《PloS one》2013,8(4)
The multidrug resistance protein 4 (Mrp4) is an ATP-binding cassette transporter that is capable of exporting the second messenger cAMP from cells, a process that might regulate cAMP-mediated anti-inflammatory processes. However, using LPS- or cigarette smoke (CS)-inflammation models, we found that neutrophil numbers in the bronchoalveolar lavage fluid (BALF) were similar in Mrp4−/− and Mrp4+/+ mice treated with LPS or CS. Similarly, neutrophil numbers were not reduced in the BALF of LPS-challenged wt mice after treatment with 10 or 30 mg/kg of the Mrp1/4 inhibitor MK571. The absence of Mrp4 also had no impact on the influx of eosinophils or IL-4 and IL-5 levels in the BALF after OVA airway challenge in mice sensitized with OVA/alum. LPS-induced cytokine release in whole blood ex vivo was also not affected by the absence of Mrp4. These data clearly suggest that Mrp4 deficiency alone is not sufficient to reduce inflammatory processes in vivo. We hypothesized that in combination with PDE4 inhibitors, used at suboptimal concentrations, the anti-inflammatory effect would be more pronounced. However, LPS-induced neutrophil recruitment into the lung was no different between Mrp4−/− and Mrp4+/+ mice treated with 3 mg/kg Roflumilast. Finally, the single and combined administration of 10 and 30 mg/kg MK571 and the specific breast cancer resistance protein (BCRP) inhibitor KO143 showed no reduction of LPS-induced TNFα release into the BALF compared to vehicle treated control animals. Similarly, LPS-induced TNFα release in murine whole blood of Mrp4+/+ or Mrp4−/− mice was not reduced by KO143 (1, 10 µM). Thus, BCRP seems not to be able to compensate for the absence or inhibition of Mrp4 in the used models. Taken together, our data suggest that Mrp4 is not essential for the recruitment of neutrophils into the lung after LPS or CS exposure or of eosinophils after allergen exposure. 相似文献
72.
Paige Wartko Mark E. Sherman Hannah P. Yang Ashley S. Felix Louise A. Brinton Britton Trabert 《Cancer epidemiology》2013,37(4):374-377
BackgroundChanges in endometrial cancer incidence rates after the precipitous decline in menopausal hormone therapy (MHT) use in 2002 have not been evaluated.MethodsUsing data from the Surveillance, Epidemiology, and End Results Program from 1992 to 2009 (SEER 13), we identified 63 428 incident endometrial cancer cases among women ages 20–74. We compared annual percent change (APC) in endometrial cancer incidence rates from 1992 to 2002 to rates from 2003 to 2009.ResultsIn contrast to the constant endometrial cancer rate pattern observed from 1992 to 2002 (APC 0.0%), rates increased after 2002 in women 50–74 years old (2.5%; PAPC comparison < 0.01). Endometrial cancer incidence increased over the entire time period among women ages 20–49 (1992–2002: 1.1%; 2003–2009: 2.1%; PAPC comparison = 0.21). Post-2002 increases in incidence among women ages 50–74 were specific to Type I endometrial tumors (1992–2002: ?0.6%; 2003–2009: 1.6%; PAPC comparison < 0.01).DiscussionThe increase in endometrial cancer incidence rates after 2002 may be related to the widespread decrease in estrogen plus progestin MHT use, which has been reported to lower endometrial cancer risk in overweight and obese women. 相似文献
73.
Katherine A. Owen Andrew Price Hannah Ainsworth Bryce N. Aidukaitis Prathyusha Bachali Michelle D. Catalina James M. Dittman Timothy D. Howard Kathryn M. Kingsmore Adam C. Labonte Miranda C. Marion Robert D. Robl Kip D. Zimmerman Carl D. Langefeld Amrie C. Grammer Peter E. Lipsky 《American journal of human genetics》2020,107(5):864
74.
Berthold Hocher Hannah Haumann Jan Rahnenführer Christoph Reichetzeder Philipp Kalk Thiemo Pfab 《Epigenetics》2016,11(7):539-552
Maternal environmental factors can impact on the phenotype of the offspring via the induction of epigenetic adaptive mechanisms. The advanced fetal programming hypothesis proposes that maternal genetic variants may influence the offspring's phenotype indirectly via epigenetic modification, despite the absence of a primary genetic defect. To test this hypothesis, heterozygous female eNOS knockout mice and wild type mice were bred with male wild type mice. We then assessed the impact of maternal eNOS deficiency on the liver phenotype of wild type offspring. Birth weight of male wild type offspring born to female heterozygous eNOS knockout mice was reduced compared to offspring of wild type mice. Moreover, the offspring displayed a sex specific liver phenotype, with an increased liver weight, due to steatosis. This was accompanied by sex specific differences in expression and DNA methylation of distinct genes. Liver global DNA methylation was significantly enhanced in both male and female offspring. Also, hepatic parameters of carbohydrate metabolism were reduced in male and female offspring. In addition, male mice displayed reductions in various amino acids in the liver. Maternal genetic alterations, such as partial deletion of the eNOS gene, can affect liver metabolism of wild type offspring without transmission of the intrinsic defect. This occurs in a sex specific way, with more detrimental effects in females. This finding demonstrates that a maternal genetic defect can epigenetically alter the phenotype of the offspring, without inheritance of the defect itself. Importantly, these acquired epigenetic phenotypic changes can persist into adulthood. 相似文献
75.
76.
Mathias J. Gerl Verena Bittl Susanne Kirchner Timo Sachsenheimer Hanna L. Brunner Christian Lüchtenborg Cagakan ?zbalci Hannah Wiedemann Sabine Wegehingel Walter Nickel Per Haberkant Carsten Schultz Marcus Krüger Britta Brügger 《PloS one》2016,11(4)
Cell membranes contain hundreds to thousands of individual lipid species that are of structural importance but also specifically interact with proteins. Due to their highly controlled synthesis and role in signaling events sphingolipids are an intensely studied class of lipids. In order to investigate their metabolism and to study proteins interacting with sphingolipids, metabolic labeling based on photoactivatable sphingoid bases is the most straightforward approach. In order to monitor protein-lipid-crosslink products, sphingosine derivatives containing a reporter moiety, such as a radiolabel or a clickable group, are used. In normal cells, degradation of sphingoid bases via action of the checkpoint enzyme sphingosine-1-phosphate lyase occurs at position C2-C3 of the sphingoid base and channels the resulting hexadecenal into the glycerolipid biosynthesis pathway. In case the functionalized sphingosine looses the reporter moiety during its degradation, specificity towards sphingolipid labeling is maintained. In case degradation of a sphingosine derivative does not remove either the photoactivatable or reporter group from the resulting hexadecenal, specificity towards sphingolipid labeling can be achieved by blocking sphingosine-1-phosphate lyase activity and thus preventing sphingosine derivatives to be channeled into the sphingolipid-to-glycerolipid metabolic pathway. Here we report an approach using clustered, regularly interspaced, short palindromic repeats (CRISPR)-associated nuclease Cas9 to create a sphingosine-1-phosphate lyase (SGPL1) HeLa knockout cell line to disrupt the sphingolipid-to-glycerolipid metabolic pathway. We found that the lipid and protein compositions as well as sphingolipid metabolism of SGPL1 knock-out HeLa cells only show little adaptations, which validates these cells as model systems to study transient protein-sphingolipid interactions. 相似文献
77.
Christina Ahlstrom Herman W. Barkema Karen Stevenson Ruth N. Zadoks Roman Biek Rowland Kao Hannah Trewby Deb Haupstein David F. Kelton Gilles Fecteau Olivia Labrecque Greg P. Keefe Shawn L. B. McKenna Kapil Tahlan Jeroen De Buck 《PloS one》2016,11(2)
Mycobacterium avium subsp. paratuberculosis (MAP) is the causative bacterium of Johne’s disease (JD) in ruminants. The control of JD in the dairy industry is challenging, but can be improved with a better understanding of the diversity and distribution of MAP subtypes. Previously established molecular typing techniques used to differentiate MAP have not been sufficiently discriminatory and/or reliable to accurately assess the population structure. In this study, the genetic diversity of 182 MAP isolates representing all Canadian provinces was compared to the known global diversity, using single nucleotide polymorphisms identified through whole genome sequencing. MAP isolates from Canada represented a subset of the known global diversity, as there were global isolates intermingled with Canadian isolates, as well as multiple global subtypes that were not found in Canada. One Type III and six “Bison type” isolates were found in Canada as well as one Type II subtype that represented 86% of all Canadian isolates. Rarefaction estimated larger subtype richness in Québec than in other Canadian provinces using a strict definition of MAP subtypes and lower subtype richness in the Atlantic region using a relaxed definition. Significant phylogeographic clustering was observed at the inter-provincial but not at the intra-provincial level, although most major clades were found in all provinces. The large number of shared subtypes among provinces suggests that cattle movement is a major driver of MAP transmission at the herd level, which is further supported by the lack of spatial clustering on an intra-provincial scale. 相似文献
78.
Cyril F. M. Marsaux Carlos Celis-Morales Jettie Hoonhout Arjan Claassen Annelies Goris Hannah Forster Rosalind Fallaize Anna L. Macready Santiago Navas-Carretero Silvia Kolossa Marianne C. Walsh Christina-Paulina Lambrinou Yannis Manios Magdalena Godlewska Iwona Traczyk Julie A. Lovegrove J. Alfredo Martinez Hannelore Daniel Mike Gibney John C. Mathers Wim H. M. Saris 《PloS one》2016,11(3)
Background
Comparisons of objectively measured physical activity (PA) between residents of European countries measured concurrently with the same protocol are lacking. We aimed to compare PA between the seven European countries involved in the Food4Me Study, using accelerometer data collected remotely via the Internet.Methods
Of the 1607 participants recruited, 1287 (539 men and 748 women) provided at least 3 weekdays and 2 weekend days of valid accelerometer data (TracmorD) at baseline and were included in the present analyses.Results
Men were significantly more active than women (physical activity level = 1.74 vs. 1.70, p < 0.001). Time spent in light PA and moderate PA differed significantly between countries but only for women. Adherence to the World Health Organization recommendation to accumulate at least 150 min of moderate-equivalent PA weekly was similar between countries for men (range: 54–65%) but differed significantly between countries for women (range: 26–49%). Prevalence estimates decreased substantially for men and women in all seven countries when PA guidelines were defined as achieving 30 min of moderate and vigorous PA per day.Conclusions
We were able to obtain valid accelerometer data in real time via the Internet from 80% of participants. Although our estimates are higher compared with data from Sweden, Norway, Portugal and the US, there is room for improvement in PA for all countries involved in the Food4Me Study. 相似文献79.
80.
Muthu Manikandan Vijayaraghavan Kannan Ordetta Hannah Mendoza Mahalingam Kanimozhi Lejla Pašić 《International journal of phytoremediation》2016,18(1):77-86
Toxicity of chromium often impairs the remediation capacity of plants used in phytoremediation of polluted soils. In this study, we have identified Albizia lebbeck as a prospective chromium hyperaccumulator and examined cultivable diversity of endophytes present in chromium-treated and control saplings. High numbers (22–100%) of endophytic bacteria, isolated from root, stem, and leaf tissues, could tolerate elevated (1–3 mM) concentrations of K2CrO7. 16S rRNA gene sequence-based phylogenetic analysis showed that the 118 isolates obtained comprised of 17 operational taxonomic units affiliated with the proteobacterial genera Rhizobium (18%), Marinomonas (1%), Pseudomonas (16%), and Xanthomonas (7%) but also with members of Firmicutes genera, such as Bacillus (35%) and Salinococcus (3%). The novel isolates belonging to Salinococcus and Bacillus could tolerate high K2CrO7 concentrations (3 mM) and also showed elevated activity of chromate reductase. In addition, majority (%) of the endophytic isolates also showed production of indole-3-acetic acid. Taken together, our results indicate that the innate endophytic bacterial community assists plants in reducing heavy metal toxicity. 相似文献