全文获取类型
收费全文 | 4014篇 |
免费 | 341篇 |
出版年
2022年 | 39篇 |
2021年 | 76篇 |
2020年 | 65篇 |
2019年 | 70篇 |
2018年 | 95篇 |
2017年 | 86篇 |
2016年 | 126篇 |
2015年 | 174篇 |
2014年 | 205篇 |
2013年 | 271篇 |
2012年 | 291篇 |
2011年 | 232篇 |
2010年 | 172篇 |
2009年 | 119篇 |
2008年 | 188篇 |
2007年 | 198篇 |
2006年 | 145篇 |
2005年 | 140篇 |
2004年 | 113篇 |
2003年 | 116篇 |
2002年 | 121篇 |
2001年 | 77篇 |
2000年 | 76篇 |
1999年 | 68篇 |
1998年 | 46篇 |
1997年 | 23篇 |
1996年 | 29篇 |
1995年 | 38篇 |
1994年 | 25篇 |
1992年 | 46篇 |
1991年 | 59篇 |
1990年 | 63篇 |
1989年 | 60篇 |
1988年 | 45篇 |
1987年 | 29篇 |
1986年 | 32篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 28篇 |
1982年 | 33篇 |
1981年 | 29篇 |
1979年 | 32篇 |
1978年 | 32篇 |
1974年 | 22篇 |
1973年 | 23篇 |
1972年 | 23篇 |
1971年 | 22篇 |
1970年 | 26篇 |
1967年 | 21篇 |
1966年 | 19篇 |
排序方式: 共有4355条查询结果,搜索用时 78 毫秒
321.
Leandro C. de Oliveira Viviam M. da Silva Francieli Colussi Aline D. Cabral Mario de Oliveira Neto Fabio M. Squina Wanius Garcia 《PloS one》2015,10(2)
Endo-β-1, 4-mannanase from Thermotoga petrophila (TpMan) is a modular hyperthermostable enzyme involved in the degradation of mannan-containing polysaccharides. The degradation of these polysaccharides represents a key step for several industrial applications. Here, as part of a continuing investigation of TpMan, the region corresponding to the GH5 domain (TpManGH5) was characterized as a function of pH and temperature. The results indicated that the enzymatic activity of the TpManGH5 is pH-dependent, with its optimum activity occurring at pH 6. At pH 8, the studies demonstrated that TpManGH5 is a molecule with a nearly spherical tightly packed core displaying negligible flexibility in solution, and with size and shape very similar to crystal structure. However, TpManGH5 experiences an increase in radius of gyration in acidic conditions suggesting expansion of the molecule. Furthermore, at acidic pH values, TpManGH5 showed a less globular shape, probably due to a loop region slightly more expanded and flexible in solution (residues Y88 to A105). In addition, molecular dynamics simulations indicated that conformational changes caused by pH variation did not change the core of the TpManGH5, which means that only the above mentioned loop region presents high degree of fluctuations. The results also suggested that conformational changes of the loop region may facilitate polysaccharide and enzyme interaction. Finally, at pH 6 the results indicated that TpManGH5 is slightly more flexible at 65°C when compared to the same enzyme at 20°C. The biophysical characterization presented here is well correlated with the enzymatic activity and provide new insight into the structural basis for the temperature and pH-dependent activity of the TpManGH5. Also, the data suggest a loop region that provides a starting point for a rational design of biotechnological desired features. 相似文献
322.
Alexander Berndt Petra Richter Hartwig Kosmehl Marcus Franz 《Cell Adhesion & Migration》2015,9(1-2):105-111
Carcinoma invasion is a complex process regulated by genetic and epigenetic factors as well. A relevant supportive condition for cancer cell migration is the reorganization of the extracellular matrix (ECM), which is realized in an orchestrated multicellular manner including carcinoma cells and stromal fibroblasts. An important key player in the process of ECM reorganization is Tenascin-C (Tn-C). The molecule occurs as different isoforms generated by alternative splicing and de novo glycosylation. Large variants of Tn-C are abundantly re-expressed in the invasive front of many carcinoma types. A special role for initiating migration and accompanied epithelial to mesenchymal transition has been suggested. Here, we review the current knowledge concerning the tumor biological importance of Tn-C, the synthesis and alternative splicing during the invasive process in general, and give an overview on the impact of Tn-C in urothelial carcinoma of the urinary bladder (UBC) and oral squamous cell carcinoma (OSCC). 相似文献
323.
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
324.
325.
G Correia de Faria Santarém R de Cleva Marco Aurélio Santo Aline Biaseto Bernhard Alexandre Vieira Gadducci Julia Maria D’Andrea Greve Paulo Roberto Santos Silva 《PloS one》2015,10(6)
Background
Obesity is associated with mobility reduction due to mechanical factors and excessive body fat. The six-minute walk test (6MWT) has been used to assess functional capacity in severe obesity.Objective
To determine the association of BMI, total and segmental body composition with distance walked (6MWD) during the six-minute walk test (6MWT) according to gender and obesity grade.Setting
University of São Paulo Medical School, Brazil; Public Practice.Methods
Functional capacity was assessed by 6MWD and body composition (%) by bioelectrical impedance analysis in 90 patients.Results
The mean 6MWD was 514.9 ± 50.3 m for both genders. The male group (M: 545.2 ± 46.9 m) showed a 6MWD higher (p = 0.002) than the female group (F: 505.6 ± 47.9 m). The morbid obese group (MO: 524.7 ± 44.0 m) also showed a 6MWD higher (p = 0.014) than the super obese group (SO: 494.2 ± 57.0 m). There was a positive relationship between 6MWD and fat free mass (FFM), FFM of upper limps (FFM_UL), trunk (FFM_TR) and lower limbs (FFM_LL). Female group presented a positive relationship between 6MWD and FFM, FFM_UL and FFM_LL and male group presented a positive relationship between 6MWD and FFM_TR. In morbid obese group there was a positive relationship between 6MWD with FFM, FFM_UL, FFM_TR and FFM_LL. The super obese group presented a positive relationship between 6MWD with FFM, FFM_TR and FFM_LL.Conclusions
Total and segmental FFM is associated with a better walking capacity than BMI. 相似文献326.
327.
328.
Background
Body image distortion is highly prevalent among overweight individuals. Whilst there is evidence that body-dissatisfied women and those suffering from disordered eating show a negative attentional bias towards their own unattractive body parts and others’ attractive body parts, little is known about visual attention patterns in the area of obesity and with respect to males. Since eating disorders and obesity share common features in terms of distorted body image and body dissatisfaction, the aim of this study was to examine whether overweight men and women show a similar attentional bias.Methods/Design
We analyzed eye movements in 30 overweight individuals (18 females) and 28 normal-weight individuals (16 females) with respect to the participants’ own pictures as well as gender- and BMI-matched control pictures (front and back view). Additionally, we assessed body image and disordered eating using validated questionnaires.Discussion
The overweight sample rated their own body as less attractive and showed a more disturbed body image. Contrary to our assumptions, they focused significantly longer on attractive compared to unattractive regions of both their own and the control body. For one’s own body, this was more pronounced for women. A higher weight status and more frequent body checking predicted attentional bias towards attractive body parts. We found that overweight adults exhibit an unexpected and stable pattern of selective attention, with a distinctive focus on their own attractive body regions despite higher levels of body dissatisfaction. This positive attentional bias may either be an indicator of a more pronounced pattern of attentional avoidance or a self-enhancing strategy. Further research is warranted to clarify these results. 相似文献329.
Melanie Brügger Thomas Dmoulins G. Tuba Barut Beatrice Zumkehr Blandina I. Oliveira Esteves Kemal Mehinagic Quentin Haas Aline Schgler Marie-Anne Rameix-Welti Jean-Franois Elouët Ueli Moehrlen Thomas M. Marti Ralph A. Schmid Artur Summerfield Horst Posthaus Nicolas Ruggli Sean R. R. Hall Marco P. Alves 《PLoS pathogens》2021,17(7)
330.
Said El?Shamieh Marion Neuillé Angélique Terray Elise Orhan Christel Condroyer Vanessa Démontant Christelle Michiels Aline Antonio Fiona Boyard Marie-Elise Lancelot Mélanie Letexier Jean-Paul Saraiva Thierry Léveillard Saddek Mohand-Sa?d Olivier Goureau José-Alain Sahel Christina Zeitz Isabelle Audo 《American journal of human genetics》2014,94(4):625-633