全文获取类型
收费全文 | 1908篇 |
免费 | 133篇 |
专业分类
2041篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 47篇 |
2021年 | 99篇 |
2020年 | 49篇 |
2019年 | 65篇 |
2018年 | 74篇 |
2017年 | 55篇 |
2016年 | 81篇 |
2015年 | 133篇 |
2014年 | 142篇 |
2013年 | 165篇 |
2012年 | 197篇 |
2011年 | 170篇 |
2010年 | 101篇 |
2009年 | 85篇 |
2008年 | 108篇 |
2007年 | 85篇 |
2006年 | 72篇 |
2005年 | 60篇 |
2004年 | 60篇 |
2003年 | 44篇 |
2002年 | 29篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4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2041条查询结果,搜索用时 15 毫秒
91.
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
92.
93.
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
94.
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
95.
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
96.
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
97.
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
98.
Francesca Resentini Cristina Ruberti Matteo Grenzi Maria Cristina Bonza Alex Costa 《Plant physiology》2021,187(4):1985
Recent insights about the transport mechanisms involved in the in and out of calcium ions in plant organelles, and their role in the regulation of cytosolic calcium homeostasis in different signaling pathways.The transport of Ca2+ across the membranes of subcellular compartments contributes to cytosolic Ca2+ homeostasis as well as environmental and developmental responses. 相似文献
99.
Romagnoli S Fogolari F Catalano M Zetta L Schaller G Urech K Giannattasio M Ragona L Molinari H 《Biochemistry》2003,42(43):12503-12510
The high resolution three-dimensional structure of the newly discovered plant viscotoxin C1, from the Asiatic Viscum album ssp. Coloratum ohwi, has been determined in solution by (1)H NMR spectroscopy at pH 3.6 and 285 K. The viscotoxin C1-fold, consisting of a helix-turn-helix motif and a short stretch of an antiparralel beta-sheet is very similar to that found for the highly similar viscotoxins A2 and A3 and for other related thionins. Different functional properties of members of the thionin family are discussed here in light of the structural and electrostatic properties. Among the very homologous family of alpha- and beta-thionins, known for their antimicrobial activity, the viscotoxin subfamily differs from the other members because of its high toxicity against tumoral cells. Key residues for the modulation of viscotoxin cytotoxicity have been identified on the basis of sequence and structural alignment. 相似文献
100.
Paolo Baldi Pieter Jacobus Wolters Matteo Komjanc Roberto Viola Riccardo Velasco Silvio Salvi 《Molecular breeding : new strategies in plant improvement》2013,31(2):429-440
A better understanding of the genetic control of tree architecture would potentially allow improved tailoring of newly bred apple cultivars in terms of field management aspects, such as planting density, pruning, pest control and disease protection. It would also have an indirect impact on yield and fruit quality. The Columnar (Co) locus strongly suppresses lateral branch elongation and is the most important genetic locus influencing tree architecture in apple. Co has previously been mapped on apple linkage group (LG) 10. In order to obtain fine mapping of Co, both genetically and physically, we have phenotypically analysed and screened three adult segregating experimental populations, with a total of 301 F1 plants, and one substantial 3-year old population of 1,250 F1 plants with newly developed simple sequence repeat (SSR) markers, based on the ‘Golden delicious’ apple genome sequence now available. Co was found to co-segregate with SSR marker Co04R12 and was confined in a region of 0.56 cM between SSR markers Co04R11 and Co04R13, corresponding to 393 kb on the ‘Golden delicious’ genome sequence. In this region, 36 genes were predicted, including at least seven sequences potentially belonging to genes that could be considered candidates for involvement in control of shoot development. Our results provide highly reliable, virtually co-segregating markers that will facilitate apple breeding aimed at modifications of the tree habit and lay the foundations for the cloning of Co. 相似文献