全文获取类型
收费全文 | 2060篇 |
免费 | 140篇 |
专业分类
2200篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 44篇 |
2021年 | 59篇 |
2020年 | 32篇 |
2019年 | 66篇 |
2018年 | 71篇 |
2017年 | 54篇 |
2016年 | 78篇 |
2015年 | 116篇 |
2014年 | 119篇 |
2013年 | 131篇 |
2012年 | 196篇 |
2011年 | 187篇 |
2010年 | 101篇 |
2009年 | 94篇 |
2008年 | 138篇 |
2007年 | 118篇 |
2006年 | 113篇 |
2005年 | 84篇 |
2004年 | 79篇 |
2003年 | 63篇 |
2002年 | 52篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 14篇 |
1997年 | 5篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有2200条查询结果,搜索用时 15 毫秒
81.
Monoclonal antibodies against pertussis toxin subunits 总被引:2,自引:0,他引:2
Massimo Bigio Roberta Rossi Daniele Nucci Maria Giuseppina Borri Guido Antoni Antonella Bartoloni Rino Rappuoli 《FEMS microbiology letters》1988,51(1):7-11
Abstract Twenty monoclonal antibodies (mAbs) reacting with cholera toxin (CT) of Vibrio cholerae strain 569B were characterized in cross-section and GM1 ganglioside inhibition assays. MAbs were characterized by reaction with CT and Escherichia coli heat-labile porcine strain (LTp ) and human strain (LTh) enterotoxins, and by GM1 ganglioside inhibition of mAb binding. Eight of 10 CT-A specific and 3 of 10 CT-B-specific mAbs cross-reacted with LTh and LTp. GM1 ganglioside inhibited reactions of the CT-B cross-reacting antibodies. Results showed that these epitodes common to the B subunit of CT and LT are located in or near the GM1 ganglioside binding region, and that the GM1 ganglioside-binding region of LT differs from that of CT. 相似文献
82.
Sandra Urbanelli Daniele Porretta Valentina Mastrantonio Romeo Bellini Giuseppe Pieraccini Riccardo Romoli Graziano Crasta Giuseppe Nascetti 《Evolution; international journal of organic evolution》2014,68(10):3030-3038
Natural selection can act against maladaptive hybridization between co‐occurring divergent populations leading to evolution of reproductive isolation among them. A critical unanswered question about this process that provides a basis for the theory of speciation by reinforcement, is whether natural selection can cause hybridization rates to evolve to zero. Here, we investigated this issue in two sibling mosquitoes species, Aedes mariae and Aedes zammitii, that show postmating reproductive isolation (F1 males sterile) and partial premating isolation (different height of mating swarms) that could be reinforced by natural selection against hybridization. In 1986, we created an artificial sympatric area between the two species and sampled about 20,000 individuals over the following 25 years. Between 1986 and 2011, the composition of mating swarms and the hybridization rate between the two species were investigated across time in the sympatric area. Our results showed that A. mariae and A. zammitii have not completed reproductive isolation since their first contact in the artificial sympatric area. We have discussed the relative role of factors such as time of contact, gene flow, strength of natural selection, and biological mechanisms causing prezygotic isolation to explain the observed results. 相似文献
83.
Giulia Borgonovo Eleonora Paulicelli Deborah Daniele Stefano Presilla Antonella Richetti Mariacarla Valli 《Reports of Practical Oncology and Radiotherapy》2022,27(4):717
BackgroundThe aim of our study is to determine whether deep inspiration breath hold (DIBH) is effective for reducing exposure of the heart, left coronary artery (LAD) and both lungs in right breast radiotherapy.Materials and methodsWe have analyzed 10 consecutive patients with right-sided breast cancer (BC), simulated during free breathing (FB) and in DIBH modality. For all patients we contoured breast PTV and organs at risk (right and left lungs, heart, LAD) on both CT scans (FB and DIBH). Finally, 5 patients were treated with IMRT and 5 with VMAT techniques.ResultsAll patients were able to end the treatments in DIBH modalities regardless of the longer treatment time in comparison to FB. The maximum and mean dose to the heart are lower in the DIBH modality. The mean values of the heart mean dose were 1.76 Gy in DIBH and 2.19 Gy in FB. The mean heart maximum dose in DIBH and FB were, respectively, 9.3 Gy and 11 Gy. Likewise, the maximum dose to the LAD is lower in DIBH; 2.57 Gy versus 3.56 Gy in FB. Noteworthy, 3 patients with hepatomegaly treated with the DIBH technique showed a higher ipsilateral lung dose than FB, but a decrease of liver dose.ConclusionWe report that the use of DIBH for right-sided BC allows the dose to the heart, LAD and to the liver to be reduced in case of hepatomegaly. This technique is well tolerated by patients, when adequately trained, and could be considered effective even in right sided BC. 相似文献
84.
Samanta Cristina das Chagas Xavier André Luiz Rodrigues Roque Daniele Bilac Vitor Ant?nio Louzada de Araújo Sócrates Fraga da Costa Neto Elias Seixas Lorosa Luiz Felipe Coutinho Ferreira da Silva Ana Maria Jansen 《PLoS neglected tropical diseases》2014,8(5)
Background
The new epidemiological scenario of orally transmitted Chagas disease that has emerged in Brazil, and mainly in the Amazon region, needs to be addressed with a new and systematic focus. Belém, the capital of Pará state, reports the highest number of acute Chagas disease (ACD) cases associated with the consumption of açaí juice.Methodology/Principal Findings
The wild and domestic enzootic transmission cycles of Trypanosoma cruzi were evaluated in the two locations (Jurunas and Val-de Cães) that report the majority of the autochthonous cases of ACD in Belém city. Moreover, we evaluated the enzootic cycle on the three islands that provide most of the açaí fruit that is consumed in these localities. We employed parasitological and serological tests throughout to evaluate infectivity competence and exposure to T. cruzi. In Val-de-Cães, no wild mammal presented positive parasitological tests, and 56% seroprevalence was observed, with low serological titers. Three of 14 triatomines were found to be infected (TcI). This unexpected epidemiological picture does not explain the high number of autochthonous ACD cases. In Jurunas, the cases of ACD could not be autochthonous because of the absence of any enzootic cycle of T. cruzi. In contrast, in the 3 island areas from which the açaí fruit originates, 66.7% of wild mammals and two dogs displayed positive hemocultures, and 15.6% of triatomines were found to be infected by T. cruzi. Genotyping by mini-exon gene and PCR-RFLP (1f8/Akw21I) targeting revealed that the mammals and triatomines from the islands harbored TcI and Trypanosoma rangeli in single and mixed infections.Conclusion/Significance
These findings show that cases of Chagas disease in the urban area of Belém may be derived from infected triatomines coming together with the açaí fruits from distant islands. We term this new epidemiological feature of Chagas disease as “Distantiae transmission”. 相似文献85.
Elena Flaugnacco Luisa Lopez Chiara Terribili Marcella Montico Stefania Zoia Daniele Sch?n 《PloS one》2015,10(9)
There is some evidence for a role of music training in boosting phonological awareness, word segmentation, working memory, as well as reading abilities in children with typical development. Poor performance in tasks requiring temporal processing, rhythm perception and sensorimotor synchronization seems to be a crucial factor underlying dyslexia in children. Interestingly, children with dyslexia show deficits in temporal processing, both in language and in music. Within this framework, we test the hypothesis that music training, by improving temporal processing and rhythm abilities, improves phonological awareness and reading skills in children with dyslexia. The study is a prospective, multicenter, open randomized controlled trial, consisting of test, rehabilitation and re-test (ID NCT02316873). After rehabilitation, the music group (N = 24) performed better than the control group (N = 22) in tasks assessing rhythmic abilities, phonological awareness and reading skills. This is the first randomized control trial testing the effect of music training in enhancing phonological and reading abilities in children with dyslexia. The findings show that music training can modify reading and phonological abilities even when these skills are severely impaired. Through the enhancement of temporal processing and rhythmic skills, music might become an important tool in both remediation and early intervention programs.
Trial Registration
ClinicalTrials.gov NCT02316873 相似文献86.
The influence of the leaflets' curvature on the flow field in two bileaflet prosthetic heart valves 总被引:4,自引:0,他引:4
A successful mechanical prosthetic heart valve design is the bileaflet valve, which has been implanted for the first time more than 20 years ago. A key feature of bileaflet valves is the geometry of the two leaflets, which can be very important in determining the flow field. Laser Doppler anemometry (LDA) was used to perform an accurate study of the velocity and turbulence shear stress peak values (TSS(max)) fields at four distances from the valve plane. TSS(max) is a relevant parameter to assess the risk of hemolysis and platelet activation associated to the implantation of a prosthetic device, continuously interacting with blood. Two bileaflet valves were tested: the St. Jude HP and the Sorin Bicarbon, of the same nominal size (19mm). The former has flat leaflets, whereas the latter's leaflets have a cylindrical surface. A high regime (CO: 6l/min) was imposed, in order to test the two valves at maximum Reynolds number and consequent turbulence generation. The flat-leaflet design of the St. Jude generates a TSS field constant with distance; on the contrary, the Bicarbon's shear stress field undergoes an evident development, with an unexpected central peak at a distance comparable to the valve's dimensions (21mm). The two bileaflet valves tested, although very similar in design, behave very differently as for their turbulence properties. In particular, the concept of curved wake leads to conclude that the curvature of the leaflets' surface must be identified as an important parameter, which deserves careful attention in PHV design and development. 相似文献
87.
Differential interleukin 1 elaboration by unfractionated and density fractionated human alveolar macrophages and blood monocytes: relationship to cell maturity 总被引:10,自引:0,他引:10
J A Elias A D Schreiber K Gustilo P Chien M D Rossman P J Lammie R P Daniele 《Journal of immunology (Baltimore, Md. : 1950)》1985,135(5):3198-3204
The elaboration of interleukin 1 (IL 1) by mononuclear phagocytes is important in the regulation of human inflammatory and fibrotic reactions. Mononuclear phagocytes are morphologically and functionally heterogeneous cells. To further understand the processes controlling inflammation and fibrosis, in particular that in the human lung, we studied the elaboration of IL 1 by unfractionated and density-fractionated human alveolar macrophages and blood monocytes. Stimulated blood monocytes elaborated more IL 1 than stimulated alveolar macrophages. In addition, denser alveolar macrophages and blood monocytes elaborated more IL 1 than less dense alveolar macrophages and monocytes. Lastly, as monocytes matured in vitro, they lost their ability to elaborate IL 1 and became less dense. Thus, there is variability between and within mononuclear phagocyte cell populations in their ability to elaborate IL 1. These differences may result in part from differences in cell maturation. 相似文献
88.
Thermal specialization across large geographical scales predicts the resilience of mangrove crab populations to global warming 下载免费PDF全文
Marco Fusi Folco Giomi Simone Babbini Daniele Daffonchio Christopher D. McQuaid Francesca Porri Stefano Cannicci 《Oikos》2015,124(6):784-795
The broad prediction that ectotherms will be more vulnerable to climate change in the tropics than in temperate regions includes assumptions about centre/edge population effects that can only be tested by within‐species comparisons across wide latitudinal gradients. Here, we investigated the thermal vulnerability of two mangrove crab species, comparing populations at the centre (Kenya) and edge (South Africa) of their distributions. At the same time, we investigated the role of respiratory mode (water‐ versus air‐breathing) in determining the thermal tolerance in amphibious organisms. To do this, we compared the vulnerability to acute temperature fluctuations of two sympatric species with two different lifestyle adaptations: the free living Perisesarma guttatum and the burrowing Uca urvillei, both pivotal to the ecosystem functioning of mangroves. The results revealed the air‐breathing U. urvillei to be a thermal generalist with much higher thermal tolerances than P. guttatum. Importantly, however, we found that, while U. urvillei showed little difference between edge and centre populations, P. guttatum showed adaptation to local conditions. Equatorial populations had elevated tolerances to acute heat stress and mechanisms of partial thermoregulation, which make them less vulnerable to global warming than temperate conspecifics. The results reveal both the importance of respiratory mode to thermal tolerance and the unexpected potential for low latitude populations/species to endure a warming climate. The results also contribute to a conceptual model on the latitudinal thermal tolerance of these key species. This highlights the need for an integrated population‐level approach to predict the consequences of climate change. 相似文献
89.
The measurement of the Reynolds stress tensor, or at least of some of its components, is a necessary step to assess if the turbulence associated with the flow near prosthetic devices can damage blood constituents. Because of the intrinsic three dimensionality of turbulence, in general, a three-component anemometer should be used to measure directly the components of the Reynolds stress tensor. However, this can be practically unfeasible, especially in vivo; therefore, it is interesting to investigate the possibility of characterizing the turbulent flows that may occur in the circulatory system with the monodimensional data that a less complete equipment (e.g., a pulsed ultrasound Doppler) can yield. From the general expression of the Reynolds stress tensor, the highest shear stress can be deduced, as well as the Reynolds normal stress in the main flow direction. The relation between these two quantities, which is an issue already addressed in previous works, can thus be rigorously formulated in terms of some characteristic parameters of the Reynolds stress tensor, the principal normal stresses and the angles that the directions that define them form with the main flow direction. An experimental verification of the ratio of the two above-mentioned quantitites for the flow across bileaflet valves, investigated by means of two-dimensional laser Doppler anemometry, will illustrate the limitations of the monodimensional approach estimating the maximum load on blood constituents. 相似文献
90.
Francesco Pantano Matteo Santoni Giuseppe Procopio Mimma Rizzo Roberto Iacovelli Camillo Porta Alessandro Conti Antonio Lugini Michele Milella Luca Galli Cinzia Ortega Francesco Maria Guida Marianna Silletta Giovanni Schinzari Elena Verzoni Daniela Modica Pierfilippo Crucitti Annamaria Rauco Alessandra Felici Valentina Ballatore Stefano Cascinu Giuseppe Tonini Giacomo Carteni Antonio Russo Daniele Santini 《PloS one》2015,10(4)