全文获取类型
收费全文 | 1942篇 |
免费 | 136篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 42篇 |
2021年 | 100篇 |
2020年 | 49篇 |
2019年 | 65篇 |
2018年 | 77篇 |
2017年 | 55篇 |
2016年 | 85篇 |
2015年 | 134篇 |
2014年 | 144篇 |
2013年 | 167篇 |
2012年 | 202篇 |
2011年 | 174篇 |
2010年 | 104篇 |
2009年 | 87篇 |
2008年 | 108篇 |
2007年 | 87篇 |
2006年 | 76篇 |
2005年 | 61篇 |
2004年 | 63篇 |
2003年 | 45篇 |
2002年 | 29篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1985年 | 11篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有2078条查询结果,搜索用时 810 毫秒
121.
F. Marcello Iaia Matteo Fiorenza Enrico Perri Giampietro Alberti Grégoire P. Millet Jens Bangsbo 《PloS one》2015,10(9)
In order to better understand the specificity of training adaptations, we compared the effects of two different anaerobic training regimes on various types of soccer-related exercise performances. During the last 3 weeks of the competitive season, thirteen young male professional soccer players (age 18.5±1 yr, height 179.5±6.5 cm, body mass 74.3±6.5 kg) reduced the training volume by ~20% and replaced their habitual fitness conditioning work with either speed endurance production (SEP; n = 6) or speed endurance maintenance (SEM; n = 7) training, three times per wk. SEP training consisted of 6–8 reps of 20-s all-out running bouts followed by 2 min of passive recovery, whereas SEM training was characterized by 6–8 x 20-s all-out efforts interspersed with 40 s of passive recovery. SEP training reduced (p<0.01) the total time in a repeated sprint ability test (RSAt) by 2.5%. SEM training improved the 200-m sprint performance (from 26.59±0.70 to 26.02±0.62 s, p<0.01) and had a likely beneficial impact on the percentage decrement score of the RSA test (from 4.07±1.28 to 3.55±1.01%) but induced a very likely impairment in RSAt (from 83.81±2.37 to 84.65±2.27 s). The distance covered in the Yo-Yo Intermittent Recovery test level 2 was 10.1% (p<0.001) and 3.8% (p<0.05) higher after SEP and SEM training, respectively, with possibly greater improvements following SEP compared to SEM. No differences were observed in the 20- and 40-m sprint performances. In conclusion, these two training strategies target different determinants of soccer-related physical performance. SEP improved repeated sprint and high-intensity intermittent exercise performance, whereas SEM increased muscles’ ability to maximize fatigue tolerance and maintain speed development during both repeated all-out and continuous short-duration maximal exercises. These results provide new insight into the precise nature of a stimulus necessary to improve specific types of athletic performance in trained young soccer players. 相似文献
122.
123.
Understanding mechanosensitivity (i.e., how cells sense the stiffness of their environment) is very important, yet there is a fundamental difficulty in understanding its mechanism: to measure an elastic modulus one requires two points of application of force—a measuring and a reference point. The cell in contact with substrate has only one (adhesion) point to work with, and thus a new method of measurement needs to be invented. The aim of this theoretical work is to develop a self-consistent physical model for mechanosensitivity, a process by which a cell detects the mechanical stiffness of its environment (e.g., a substrate it is attached to via adhesion points) and generates an appropriate chemical signaling to remodel itself in response to this environment. The model uses the molecular mechanosensing complex of latent TGF-β attached to the adhesion point as the biomarker. We show that the underlying Brownian motion in the substrate is the reference element in the measuring process. The model produces a closed expression for the rate of release of active TGF-β, which depends on the substrate stiffness and the pulling force coming from the cell in a subtle and nontrivial way. It is consistent with basic experimental data showing an increase in signal for stiffer substrates and higher pulling forces. In addition, we find that for each cell there is a range of stiffness where a homeostatic configuration of the cell can be achieved, outside of which the cell either relaxes its cytoskeletal forces and detaches from the very weak substrate, or generates an increasingly strong pulling force through stress fibers with a positive feedback loop on very stiff substrates. In this way, the theory offers the underlying mechanism for the myofibroblast conversion in wound healing and smooth muscle cell dysfunction in cardiac disease. 相似文献
124.
125.
126.
M. Giovanna Parisi Matteo Cammarata Gigliola Benenati Giuseppina Salerno Valentina Mangano Aiti Vizzini Nicolò Parrinello 《Cell and tissue research》2010,341(2):279-288
The purification, cloning, sequencing, molecular properties and expression of a fucose-binding lectin from the serum of Dicentrarchus labrax (DlFBL) have been previously reported. We now describe the distribution and expression of DlFBL during fish ontogeny. Immunohistochemistry
and in situ hybridization assays were carried out at various developmental stages (from 10 days post-hatching larvae to juveniles).
Another fucose-binding lectin, similar to DlFBL in biochemical, immunochemical and agglutinating properties, was extracted
and purified from eggs and appeared to be localized in the embryo yolk sack residual. DlFBL was found in columnar and goblet
cells of the intestinal epithelium of larvae (from 20 days post-hatching) and juveniles and in parenchymal tissue of juveniles.
DlFBL mRNA and protein were detected in the intestinal epithelium and in hepatocytes. An amplification product from degenerate
primers indicates that lectin isotypes with DlFBL epitopes are expressed in eggs and embryos. Whether the lectin fraction
isolated from eggs and embryos includes DlFBL of maternal origin remains unclear. 相似文献
127.
Marco Girardello Matteo Griggio Mark J. Whittingham Stephen P. Rushton 《Ecological Research》2010,25(1):103-111
Analyzing the relationships between the distribution of animal species and climatic variables is not only important for understanding
which factors govern species distribution but also for improving our ability to predict future ecological responses to climate
change. In the context of global climate change, amphibians are of particular interest because of their extreme sensitivity
to the variation of temperature and precipitation regimes. We analyzed species–climate relationships for 17 amphibian species
occurring in Italy using species distribution data at the 10 × 10 km resolution. A machine learning method, Random Forests,
was used to model the distribution of amphibians in relation to a set of 18 climatic variables. The results showed that the
variables which had the highest importance were those related to precipitation, indicating that precipitation is an important
factor in determining amphibian distribution. Future projections showed a complex response of species distributions, emphasizing
the potential severity of climate change on the distributions of amphibians in Italy. The species that will decrease the most
are those occurring in mountainous and Mediterranean areas. Our results provide some preliminary information that could be
useful for amphibian conservation, indicating if future conservation priorities for some species should be enhanced. 相似文献
128.
Rachele Beghin Emanuele Lingua Matteo Garbarino Michele Lonati Giovanni Bovio Renzo Motta Raffaella Marzano 《Ecological Engineering》2010,36(10):1365-1372
It is frequently believed that a post-fire environment requires immediate actions in order to be restored. Salvage logging followed by plantation is a common post-fire restoration practice in many forests of the northwestern Italian Alps.The objectives of this study were to assess the impact of active and passive management techniques on the restoration of a burned area of the Aosta Valley and to determine which approach is the most suitable for enhancing Pinus sylvestris regeneration after stand replacing wildfires.The influence of five management options (no intervention; salvage logging; broadleaves plantation; Larix decidua plantation; P. sylvestris or Pseudotsuga menziesii plantation) and environmental variables on natural regeneration structure and composition was evaluated through direct gradient analysis.Pinus sylvestris and Populus tremula were the dominant tree species (40 and 29%, respectively) in the regeneration layer. Density, size, and structural diversity of natural regeneration were higher in the no intervention area. The proximity to forest edge was found to be the most important environmental variable.This study provided evidence that taking advantage of natural restoration processes may be a suitable alternative strategy to the active restoration practices adopted according to the Aosta Valley policy of post-fire management. 相似文献
129.
The identification of a series of novel, soluble non-peptidic neuropeptide Y Y2 receptor antagonists
Lunniss GE Barnes AA Barton N Biagetti M Bianchi F Blowers SM Caberlotto LL Emmons A Holmes IP Montanari D Norris R Puckey GV Walters DJ Watson SP Willis J 《Bioorganic & medicinal chemistry letters》2010,20(24):7341-7344
The identification and subsequent optimisation of a selective non-peptidic NPY Y2 antagonist series is described. This led to the development of amine 2, a selective, soluble NPY Y2 receptor antagonist with enhanced CNS exposure. 相似文献
130.
Debora Paris Dominique Melck Matteo Stocchero Oceania D’Apolito Rosa Calemma Giuseppe Castello Francesco Izzo Giuseppe Palmieri Gaetano Corso Andrea Motta 《Metabolomics : Official journal of the Metabolomic Society》2010,6(3):405-416
Human hepatocellular carcinoma (HCC) is the most recurrent malignancy of the liver and represents one of the main causes of
cancer death worldwide. Furthermore, the liver is the most frequent site of metastatic colonization, and hepatic metastases
are far more common than primary cancers in Western countries. A possible way of investigating liver diseases is to study
the tissue metabolic profiles. High-resolution nuclear magnetic resonance (NMR) spectroscopy of hepatic tissue extracts was
combined with pattern-recognition and visualization techniques to uncover metabolic differences among analyzed tissue types.
Extracts were from primary HCC, chronic hepatitis-C-virus related cirrhotic tissues, hepatic metastases from colorectal carcinomas,
and non-cirrhotic normal liver tissues adjacent to metastases as controls. We identified all metabolites present in the NMR
spectra, and after statistical evaluation of all spectral classes, we were able to define the metabolic changes underlying
the different liver conditions and diseases. In particular, the lactate and the glucose tissue signals were found to primarily
discriminate the different histological samples. We followed the biochemical changes of human hepatic lesions through primary
(HCC) and secondary (metastases from colorectal carcinoma) liver tumors, cirrhotic tissues, and non-cirrhotic histologically-confirmed
normal liver tissues adjacent to metastases, achieving a metabolic differentiation of the various pathological states based
upon the variation of the intracellular lactate/glucose ratio. It is suggested that such a signal pattern may act as a potential
marker for assessing pathological hepatic lesions. 相似文献