全文获取类型
收费全文 | 2759篇 |
免费 | 182篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 36篇 |
2020年 | 17篇 |
2019年 | 28篇 |
2018年 | 33篇 |
2017年 | 28篇 |
2016年 | 56篇 |
2015年 | 113篇 |
2014年 | 119篇 |
2013年 | 153篇 |
2012年 | 215篇 |
2011年 | 209篇 |
2010年 | 111篇 |
2009年 | 123篇 |
2008年 | 171篇 |
2007年 | 176篇 |
2006年 | 160篇 |
2005年 | 149篇 |
2004年 | 176篇 |
2003年 | 131篇 |
2002年 | 123篇 |
2001年 | 32篇 |
2000年 | 29篇 |
1999年 | 36篇 |
1998年 | 38篇 |
1997年 | 43篇 |
1996年 | 25篇 |
1995年 | 20篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 41篇 |
1991年 | 24篇 |
1990年 | 18篇 |
1989年 | 29篇 |
1988年 | 27篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1969年 | 4篇 |
排序方式: 共有2943条查询结果,搜索用时 31 毫秒
81.
Fran?oise Schmitt Guillaume Podevin Jo?l Poupon Jér?me Roux Pierre Legras Jean-Marc Trocello France Woimant Olivier Laprévote Tuan Huy NGuyen Souleiman El Balkhi 《PloS one》2013,8(12)
Background
Wilson''s disease (WD) is an inherited disorder of copper metabolism leading to liver failure and/or neurological impairment. Its diagnosis often remains difficult even with genetic testing. Relative exchangeable copper (REC) has recently been described as a reliable serum diagnostic marker for WD.Methodology/Principal Findings
The aim of this study was to validate the use of REC in the Long Evans Cinnamon (LEC) rat, an animal model for WD, and to study its relevance under different conditions in comparison with conventional markers. Two groups of LEC rats and one group of Long-Evans (LE) rats were clinically and biologically monitored from 6 to 28 weeks of age. One group of LEC rats was given copper-free food. The other groups had normal food. Blood samples were collected each month and different serum markers for WD (namely ceruloplasmin oxidase activity, exchangeable copper (CuEXC), total serum copper and REC) and acute liver failure (serum transaminases and bilirubinemia) were tested. Every LEC rat under normal food developed acute liver failure (ALF), with 40% global mortality. Serum transaminases and bilirubinemia along with total serum copper and exchangeable copper levels increased with the onset of acute liver failure. A correlation was observed between CuEXC values and the severity of ALF. Cut-off values were different between young and adult rats and evolved because of age and/or liver failure. Only REC, with values >19%, was able to discriminate LEC groups from the LE control group at every time point in the study. REC sensitivity and specificity reached 100% in adults rats.Conclusions/Significance
REC appears to be independent of demographic or clinical data in LEC rats. It is a very simple and reliable blood test for the diagnosis of copper toxicosis owing to a lack of ATP7B function. CuEXC can be used as an accurate biomarker of copper overload. 相似文献82.
In prey species, vigilance is an important part of the decision making process related to predation risk effects. Therefore, understanding the mechanisms shaping vigilance behavior provides relevant insights on factors influencing individual fitness. We investigated the role of extrinsic and intrinsic factors on vigilance behavior in Mediterranean mouflon (Ovis gmelini musimon×Ovis sp.) in a study site spatially and temporally contrasted in human pressures. Both sexes were less vigilant in the wildlife reserve compared to surrounding unprotected areas, except for males during the hunting period. During this period, males tended to be less strictly restricted to the reserve than females what might lead to a pervasive effect of hunting within the protected area, resulting in an increase in male vigilance. It might also be a rutting effect that did not occur in unprotected areas because males vigilance was already maximal in response to human disturbances. In both sexes, yearlings were less vigilant than adults, probably because they traded off vigilance for learning and energy acquisition and/or because they relied on adult experience present in the group. Similarly, non-reproductive females benefited of the vigilance effort provided by reproductive females when belonging to the same group. However, in the absence of reproductive females, non-reproductive females were as vigilant as reproductive females. Increasing group size was only found to reduce vigilance in females (up to 17.5%), not in males. We also showed sex-specific responses to habitat characteristics. Females increased their vigilance when habitat visibility decreased (up to 13.8%) whereas males increased their vigilance when feeding on low quality sites, i.e., when concomitant increase in chewing time can be devoted to vigilance with limited costs. Our global approach was able to disentangle the sex-specific sources of variation in mouflon vigilance and stressed the importance of reserves in managing and conserving wild sheep populations. 相似文献
83.
Voahangy Andrianaivoarimanana Katharina Kreppel Nohal Elissa Jean-Marc Duplantier Elisabeth Carniel Minoarisoa Rajerison Ronan Jambou 《PLoS neglected tropical diseases》2013,7(11)
Plague, a zoonosis caused by Yersinia pestis, is still found in Africa, Asia, and the Americas. Madagascar reports almost one third of the cases worldwide. Y. pestis can be encountered in three very different types of foci: urban, rural, and sylvatic. Flea vector and wild rodent host population dynamics are tightly correlated with modulation of climatic conditions, an association that could be crucial for both the maintenance of foci and human plague epidemics. The black rat Rattus rattus, the main host of Y. pestis in Madagascar, is found to exhibit high resistance to plague in endemic areas, opposing the concept of high mortality rates among rats exposed to the infection. Also, endemic fleas could play an essential role in maintenance of the foci. This review discusses recent advances in the understanding of the role of these factors as well as human behavior in the persistence of plague in Madagascar. 相似文献
84.
Jean-Jacques Godon Laure Arcemisbéhère Renaud Escudié Jérôme Harmand Edouard Miambi Jean-Philippe Steyer 《Bioenergy Research》2013,6(3):1063-1081
Over millions of years, living organisms have explored and optimized the digestion of a wide variety of substrates. Engineers who develop anaerobic digestion processes for waste treatment and energy production can learn much from this accumulated ‘experience’. The aim of this work is a survey based on the comparison of 190 digestive tracts (vertebrate and insect) considered as ‘reactors’ and their anaerobic processes. Within a digestive tract, each organ is modeled as a type of reactor (continuous stirred-tank, such reactors in series, plug-flow or batch) associated with chemical aspects such as pH or enzymes. Based on this analysis, each complete digestion process has been rebuilt and classified in accordance with basic structures which take into account the relative size of the different reactors. The results show that all animal digestive structures can be grouped within four basic types. Size and/or position in the structure of the different reactors (pre/post treatment and anaerobic microbial digestion) are closely correlated to the degradability of the feed (substrate). Major common features are: (i) grinding, (ii) an extreme pH compartment, and (iii) correlation between the size of the microbial compartment and the degradability of the feed. Thus, shared answers found by animals during their evolution can be a source of inspiration for engineers in designing optimal anaerobic processes. 相似文献
85.
Alexander Benedikt Leichtle Uta Ceglarek Peter Weinert Christos T. Nakas Jean-Marc Nuoffer Julia Kase Tim Conrad Helmut Witzigmann Joachim Thiery Georg Martin Fiedler 《Metabolomics : Official journal of the Metabolomic Society》2013,9(3):677-687
Metabolomics as one of the most rapidly growing technologies in the “-omics” field denotes the comprehensive analysis of low molecular-weight compounds and their pathways. Cancer-specific alterations of the metabolome can be detected by high-throughput mass-spectrometric metabolite profiling and serve as a considerable source of new markers for the early differentiation of malignant diseases as well as their distinction from benign states. However, a comprehensive framework for the statistical evaluation of marker panels in a multi-class setting has not yet been established. We collected serum samples of 40 pancreatic carcinoma patients, 40 controls, and 23 pancreatitis patients according to standard protocols and generated amino acid profiles by routine mass-spectrometry. In an intrinsic three-class bioinformatic approach we compared these profiles, evaluated their selectivity and computed multi-marker panels combined with the conventional tumor marker CA 19-9. Additionally, we tested for non-inferiority and superiority to determine the diagnostic surplus value of our multi-metabolite marker panels. Compared to CA 19-9 alone, the combined amino acid-based metabolite panel had a superior selectivity for the discrimination of healthy controls, pancreatitis, and pancreatic carcinoma patients $ [ {\text{volume under ROC surface}}\;\left( {\text{VUS}} \right) = 0. 8 9 1 { }\left( { 9 5\,\% {\text{ CI }}0. 7 9 4- 0. 9 6 8} \right)]. $ We combined highly standardized samples, a three-class study design, a high-throughput mass-spectrometric technique, and a comprehensive bioinformatic framework to identify metabolite panels selective for all three groups in a single approach. Our results suggest that metabolomic profiling necessitates appropriate evaluation strategies and—despite all its current limitations—can deliver marker panels with high selectivity even in multi-class settings. 相似文献
86.
87.
Marjan Boerma Junru Wang Vijayalakshmi Sridharan Jean-Marc Herbert Martin Hauer-Jensen 《PloS one》2013,8(7)
Radiation therapy in the treatment of cancer is dose limited by radiation injury in normal tissues such as the intestine and the heart. To identify the mechanistic involvement of transforming growth factor-beta 1 (TGF-β1) in intestinal and cardiac radiation injury, we studied the influence of pharmacological induction of TGF-β1 with xaliproden (SR 57746A) in rat models of radiation enteropathy and radiation-induced heart disease (RIHD). Because it was uncertain to what extent TGF-β induction may enhance radiation injury in heart and intestine, animals were exposed to irradiation schedules that cause mild to moderate (acute) radiation injury. In the radiation enteropathy model, male Sprague-Dawley rats received local irradiation of a 4-cm loop of rat ileum with 7 once-daily fractions of 5.6 Gy, and intestinal injury was assessed at 2 weeks and 12 weeks after irradiation. In the RIHD model, male Sprague-Dawley rats received local heart irradiation with a single dose of 18 Gy and were followed for 6 months after irradiation. Rats were treated orally with xaliproden starting 3 days before irradiation until the end of the experiments. Treatment with xaliproden increased circulating TGF-β1 levels by 300% and significantly induced expression of TGF-β1 and TGF-β1 target genes in the irradiated intestine and heart. Various radiation-induced structural changes in the intestine at 2 and 12 weeks were significantly enhanced with TGF-β1 induction. Similarly, in the RIHD model induction of TGF-β1 augmented radiation-induced changes in cardiac function and myocardial fibrosis. These results lend further support for the direct involvement of TGF-β1 in biological mechanisms of radiation-induced adverse remodeling in the intestine and the heart. 相似文献
88.
Photosynthesis Research - Light response curves (LRCs) describe how the rate of photosynthesis varies as a function of light. They provide information on the maximum photosynthetic capacity,... 相似文献
89.
90.
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