全文获取类型
收费全文 | 4972篇 |
免费 | 345篇 |
国内免费 | 1篇 |
专业分类
5318篇 |
出版年
2023年 | 34篇 |
2022年 | 72篇 |
2021年 | 121篇 |
2020年 | 88篇 |
2019年 | 103篇 |
2018年 | 116篇 |
2017年 | 98篇 |
2016年 | 172篇 |
2015年 | 260篇 |
2014年 | 291篇 |
2013年 | 376篇 |
2012年 | 454篇 |
2011年 | 380篇 |
2010年 | 268篇 |
2009年 | 231篇 |
2008年 | 315篇 |
2007年 | 303篇 |
2006年 | 275篇 |
2005年 | 233篇 |
2004年 | 195篇 |
2003年 | 205篇 |
2002年 | 163篇 |
2001年 | 45篇 |
2000年 | 45篇 |
1999年 | 44篇 |
1998年 | 26篇 |
1997年 | 27篇 |
1996年 | 34篇 |
1995年 | 30篇 |
1994年 | 23篇 |
1993年 | 25篇 |
1992年 | 30篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1967年 | 5篇 |
1966年 | 7篇 |
排序方式: 共有5318条查询结果,搜索用时 13 毫秒
951.
Linda Avesani Matilde Merlin Elisa Gecchele Stefano Capaldi Annalisa Brozzetti Alberto Falorni Mario Pezzotti 《Transgenic research》2014,23(2):281-291
The 65-kDa isoform of human glutamic acid decarboxylase (hGAD65) is a major diabetes autoantigen that can be used for the diagnosis and (more recently) the treatment of autoimmune diabetes. We previously reported that a catalytically-inactive version (hGAD65mut) accumulated to tenfold higher levels than its active counterpart in transgenic tobacco plants, providing a safe and less expensive source of the protein compared to mammalian production platforms. Here we show that hGAD65mut is also produced at higher levels than hGAD65 by transient expression in Nicotiana benthamiana (using either the pK7WG2 or MagnICON vectors), in insect cells using baculovirus vectors, and in bacterial cells using an inducible-expression system, although the latter system is unsuitable because hGAD65mut accumulates within inclusion bodies. The most productive of these platforms was the MagnICON system, which achieved yields of 78.8 μg/g fresh leaf weight (FLW) but this was substantially less than the best-performing elite transgenic tobacco plants, which reached 114.3 μg/g FLW after six generations of self-crossing. The transgenic system was found to be the most productive and cost-effective although the breeding process took 3 years to complete. The MagnICON system was less productive overall, but generated large amounts of protein in a few days. Both plant-based systems were therefore advantageous over the baculovirus-based production platform in our hands. 相似文献
952.
Filippo Menolascina Gianfranco Fiore Emanuele Orabona Luca De Stefano Mike Ferry Jeff Hasty Mario di Bernardo Diego di Bernardo 《PLoS computational biology》2014,10(5)
We describe an innovative experimental and computational approach to control the expression of a protein in a population of yeast cells. We designed a simple control algorithm to automatically regulate the administration of inducer molecules to the cells by comparing the actual protein expression level in the cell population with the desired expression level. We then built an automated platform based on a microfluidic device, a time-lapse microscopy apparatus, and a set of motorized syringes, all controlled by a computer. We tested the platform to force yeast cells to express a desired fixed, or time-varying, amount of a reporter protein over thousands of minutes. The computer automatically switched the type of sugar administered to the cells, its concentration and its duration, according to the control algorithm. Our approach can be used to control expression of any protein, fused to a fluorescent reporter, provided that an external molecule known to (indirectly) affect its promoter activity is available. 相似文献
953.
Stefano Luccioli Eshel Ben-Jacob Ari Barzilai Paolo Bonifazi Alessandro Torcini 《PLoS computational biology》2014,10(9)
It has recently been discovered that single neuron stimulation can impact network dynamics in immature and adult neuronal circuits. Here we report a novel mechanism which can explain in neuronal circuits, at an early stage of development, the peculiar role played by a few specific neurons in promoting/arresting the population activity. For this purpose, we consider a standard neuronal network model, with short-term synaptic plasticity, whose population activity is characterized by bursting behavior. The addition of developmentally inspired constraints and correlations in the distribution of the neuronal connectivities and excitabilities leads to the emergence of functional hub neurons, whose stimulation/deletion is critical for the network activity. Functional hubs form a clique, where a precise sequential activation of the neurons is essential to ignite collective events without any need for a specific topological architecture. Unsupervised time-lagged firings of supra-threshold cells, in connection with coordinated entrainments of near-threshold neurons, are the key ingredients to orchestrate population activity. 相似文献
954.
Stefano Guariniello Giovanni Colonna Raffaele Raucci Maria Costantini Gianni Di Bernardo Francesca Bergantino Giuseppe Castello Susan Costantini 《Biochimica et Biophysica Acta - Proteins and Proteomics》2014,1844(2):447-456
In humans we know 25 selenoproteins that play important roles in redox regulation, detoxification, immune-system protection and viral suppression. In particular, selenoprotein M (SelM) may function as thiol disulfide oxidoreductase that participates in the formation of disulfide bonds, and can be implicated in calcium responses. However, it presents a redox motif (CXXU), where U is a selenocysteine, and may also function as redox regulator because its decreased or increased expression regulated by dietary selenium alters redox homeostasis. No data are reported in literature about its involvement in cancer but only in neurodegenerative diseases. In this paper we evaluated the SelM expression in two hepatoma cell lines, HepG2 and Huh7, compared to normal hepatocytes. The results suggested its involvement in hepatocellular carcinoma (HCC) as well as its possible use to follow the progression of this cancer as putative marker. The aim of this study has been to analyze the structure–function relationships of SelM. Hence, firstly we studied the evolutionary history of this protein by phylogenetic analysis and GC content of genes from various species. So, we modeled the three-dimensional structure of the human SelM evaluating its energetic stability by molecular dynamics simulations. Moreover, we modeled some of its mutants to obtain structural information helpful for structure-based drug design. 相似文献
955.
Matteo Brunelli Serena Beccari Romano Colombari Stefano Gobbo Luca Giobelli Andrea Pellegrini Marco Chilosi Maria Lunardi Guido Martignoni Aldo Scarpa Albino Eccher 《Diagnostic pathology》2014,9(Z1):S12
Background
Validation of digital whole slide images is crucial to ensure that diagnostic performance is at least equivalent to that of glass slides and light microscopy. The College of American Pathologists Pathology and Laboratory Quality Center recently developed recommendations for internal digital pathology system validation. Following these guidelines we sought to validate the performance of a digital approach for routine diagnosis by using an iPad and digital control widescreen-assisted workstation through a pilot study.Methods
From January 2014, 61 histopathological slides were scanned by ScanScope Digital Slides Scanner (Aperio, Vista, CA). Two independent pathologists performed diagnosis on virtual slides in front of a widescreen by using two computer devices (ImageScope viewing software) located to different Health Institutions (AOUI Verona) connected by local network and a remote image server using an iPad tablet (Aperio, Vista, CA), after uploading the Citrix receiver for iPad. Quality indicators related to image characters and work-flow of the e-health cockpit enterprise system were scored based on subjective (high vs poor) perception. The images were re-evaluated two weeks apart.Results
The whole glass slides encountered 10 liver: hepatocarcinoma, 10 renal carcinoma, 10 gastric carcinoma and 10 prostate biopsies: adenocarcinoma, 5 excisional skin biopsies: melanoma, 5 lymph-nodes: lymphoma. 6 immuno- and 5 special stains were available for intra- and internet remote viewing. Scan times averaged two minutes and 54 seconds per slide (standard deviation 2 minutes 34 seconds). Megabytes ranged from 256 to 680 (mean 390) per slide storage. Reliance on glass slide, image quality (resolution and color fidelity), slide navigation time, simultaneous viewers in geographically remote locations were considered of high performance score. Side by side comparisons between diagnosis performed on tissue glass slides versus widescreen were excellent showing an almost perfect concordance (0.81, kappa index).Conclusions
We validated our institutional digital pathology system for routine diagnostic facing with whole slide images in a cockpit enterprise digital system or iPad tablet. Computer widescreens are better for diagnosing scanned glass slide that iPad. For urgent requests, iPad may be used. Legal aspects have to be soon faced with to permit the clinical use of this technology in a manner that does not compromise patient care.956.
Hymenopteran parasitoids can utilize substrate-borne semiochemicals released by conspecifics or by their hosts, increasing the likelihood of successful mating and host location. According to the literature, two substrate-borne chemo-orientation patterns can occur: (1) biased random searching, a non-directional reaction toward the chemicals (kinesis), and (2) trail-following searching, a directional response toward the source emitting the chemical compounds (taxis). These two different strategies can be adopted by parasitoids to locate hosts and mates. In host location, random searching is induced by allelochemicals indirectly associated with the host, whereas trail-following behavior is induced by allelochemicals directly emitted by the target organism. In mate finding, sex pheromones emitted by conspecifics can induce either the random searching or the trail-following behavior, although the spatial distribution of virgin conspecifics could be an important factor driving the evolution of substrate-borne chemo-orientation patterns. The chemical nature of substrate-borne semiochemicals has not yet been fully elucidated. Most studies have shown that crude extracts are biologically active for eliciting parasitoid arrestment response, but few studies have clearly characterized their chemical nature. However, experimental evidence indicates that cuticular lipids located in the external layer of insects’ bodies play a role in parasitoid–parasitoid and host–parasitoid communication. The ecological role of parasitoid chemo-orientation in host and mate location is discussed from a biological control perspective. 相似文献
957.
Manuel María González-Duarte Cesar Megina Stefano Piraino 《Helgoland Marine Research》2014,68(4):511-521
In the last 20–30 years, the temperature of the Mediterranean Sea has increased and global warming is allowing the establishment of tropical-affinity species into more temperate zones. Sessile communities are particularly useful as a baseline for ecological monitoring; however, a lack of historical data series exists for sessile marine organisms without commercial interest. Hydroids are ubiquitous components of the benthic sessile fauna on rocky shores and have been used as bio-indicators of environmental conditions. In this study on the benthic hydroid assemblages of the Chafarinas Islands (Alboran Sea, South-Western Mediterranean), we characterized the hydroid assemblages, identified the bathymetric gradients, and compared them with a previous study carried out in 1991. Hydroid assemblages showed a significant difference both between year and among depths. Furthermore, eight species not present in 1991 were found, including two possible new species and the tropical and subtropical species Sertularia marginata. Due to its strategic position at the entrance of the Mediterranean and the existence of previous data on hydroid assemblages, the Chafarinas Islands are proposed as a possible monitoring point for entrance of Atlantic tropical species into the Mediterranean Sea. 相似文献
958.
Food webs have markedly non‐random network structure. Ecologists maintain that this non‐random structure is key for stability, since large random ecological networks would invariably be unstable and thus should not be observed empirically. Here we show that a simple yet overlooked feature of natural food webs, the correlation between the effects of consumers on resources and those of resources on consumers, substantially accounts for their stability. Remarkably, random food webs built by preserving just the distribution and correlation of interaction strengths have stability properties similar to those of the corresponding empirical systems. Surprisingly, we find that the effect of topological network structure on stability, which has been the focus of countless studies, is small compared to that of correlation. Hence, any study of the effects of network structure on stability must first take into account the distribution and correlation of interaction strengths. 相似文献
959.
Paolo Fraticelli Barbara Gabrielli Giovanni Pomponio Gabriele Valentini Silvia Bosello Piersandro Riboldi Maria Gerosa Paola Faggioli Roberto Giacomelli Nicoletta Del Papa Roberto Gerli Claudio Lunardi Stefano Bombardieri Walter Malorni Angelo Corvetta Gianluca Moroncini Armando Gabrielli 《Arthritis research & therapy》2014,16(4):R144
Introduction
Pulmonary involvement represents a major cause of death of systemic sclerosis (SSc) patients. Recent data suggest that tyrosine kinase inhibitors, such as imatinib, may be a therapeutic option for SSc patients. However, preliminary published clinical trials were inconclusive about imatinib efficacy and showed side effects. The purpose of this study was to verify efficacy and tolerability of low-dose imatinib on interstitial lung disease in a cohort of SSc patients unresponsive to cyclophosphamide therapy.Methods
Thirty consecutive SSc patients with active pulmonary involvement, unresponsive to cyclophosphamide, were treated with imatinib 200 mg/day for 6 months followed by a 6-month follow-up. A “good response” was defined as an increase of forced vital capacity (FVC) by more of 15% and/or increase of diffusing capacity of carbon monoxide (DLCO) >15% and PaO2 > 90% of initial value and high-resolution computed tomography (HRCT)-scan pattern unchanged or improved.Results
Twenty-six patients completed the study. Three patients died and one patient was lost to follow-up. Four patients (15.32%) had a good response, 7 worsened and 15 had a stabilized lung disease. Overall, 19 (73.07%) patients had an improved or stabilized lung disease. After a 6-month follow-up, 12 (54.5%) of the 22 patients showed an improved or stabilized lung disease.Conclusions
Lung function was stabilized in a large proportion of patients unresponsive to cyclophosphamide therapy and a beneficial outcome emerged from the analysis of HRCT lung scans. There was no significant improvement of skin involvement, and the low dose was well tolerated. These data provide useful suggestions to design future randomized clinical trials for SSc therapeutics.Trial registration
ClinicalTrials.gov . Registered 13 December 2007. NCT00573326相似文献960.
Ercole Mazzeo Laura Rubino Michela Buglione Paolo Antognoni Stefano Maria Magrini Francesco Bertoni Manuela Parmiggiani Paola Barbieri Filippo Bertoni 《Reports of Practical Oncology and Radiotherapy》2014,19(2):77-91