全文获取类型
收费全文 | 653篇 |
免费 | 36篇 |
专业分类
689篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 14篇 |
2021年 | 29篇 |
2020年 | 12篇 |
2019年 | 18篇 |
2018年 | 23篇 |
2017年 | 17篇 |
2016年 | 31篇 |
2015年 | 40篇 |
2014年 | 37篇 |
2013年 | 43篇 |
2012年 | 60篇 |
2011年 | 41篇 |
2010年 | 33篇 |
2009年 | 23篇 |
2008年 | 37篇 |
2007年 | 35篇 |
2006年 | 20篇 |
2005年 | 27篇 |
2004年 | 17篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 17篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
排序方式: 共有689条查询结果,搜索用时 0 毫秒
21.
22.
Soares JB Pimentel-Nunes P Afonso L Rolanda C Lopes P Roncon-Albuquerque R Gonçalves N Boal-Carvalho I Pardal F Lopes S Macedo G Lara-Santos L Henrique R Moreira-Dias L Gonçalves R Dinis-Ribeiro M Leite-Moreira AF 《Innate immunity》2012,18(5):700-708
We evaluated expression of TLR2, TLR4 and proinflammatory genes [NF-κB, TNF-α, cyclooxygenase-2 (COX-2)] in liver samples of patients in different stages of liver disease. Fifteen patients with unexplained transaminases elevation (reference group), 22 with viral chronic hepatitis (hepatitis group), 14 with virus-induced severe fibrosis/cirrhosis (cirrhosis group) and 10 with hepatocarcinoma (hepatocarcinoma group) were consecutively included in the study. Quantification of TLR2, TLR4, NF-κB, TNF-α and COX-2 mRNA was done by real-time RT-PCR and TLR2 and TLR4 protein expression was evaluated by immunohistochemistry. Compared with reference, TLR2 and TLR4 mRNA was increased in hepatitis (TLR2: 2.66?±?0.69; TLR4: 3.11?±?0.79; P?0.05) and cirrhosis (TLR2: 2.14?±?0.5; TLR4: 1.74?±?0.27; P?0.05) and decreased in hepatocarcinoma (TLR2: 0.48?±?0.15; TLR4: 0.54?±?0.10; P?0.05). This associated with increased TNF-α and COX-2 mRNA in hepatitis (TNF-α: 3.24?±?0.79; COX-2: 2.47?±?0.36; P?0.05) and cirrhosis (TNF-α: 1.73?±?0.28; COX-2: 1.8?±?0.35, P?0.05), whereas NF-κB mRNA was increased in hepatitis (2.42?±?0.31; P?0.05) and unchanged in cirrhosis (1.34?±?0.17; P?=?0.3). Hepatocarcinoma presented increased COX-2 mRNA (1.63?±?0.15; P?0.05) and maintained (at decreased levels) mRNA of NF-κB (0.52?±?0.12) and TNF-α (0.52?±?0.12; P?0.05, all genes). Immunohistochemistry confirmed increased expression of TLR2 and TLR4 in hepatitis and cirrhosis and maintained expression in hepatocarcinoma. Upregulation of TLR2, TLR4 and their proinflammatory mediators is associated with virus-induced hepatic IFC sequence. 相似文献
23.
Marcelo Bighetti Toniollo Ligia Jaqueline Pereira Vieira Mikaelly dos Santos Sá Ana Paula Macedo Jair Pereira de Melo Jr Andrea Sayuri Silveira Dias Terada 《Computer methods in biomechanics and biomedical engineering》2019,22(7):706-712
In implantology, when financial or biological feasibility limitations appear, it is necessary to use prostheses with geometries that deviate from the conventional, with a pontic in the absence of an intermediate implant. The aim of this study was analyze and understand the general differences in the stresses generated in implants, components and infrastructures according to the configuration of the prosthesis over three or two implants. Thus, this paper analyzes the von Mises equivalent stresses (VMES) of ductile materials on their external surfaces. The experimental groups: Regular Splinted Conventional Group (RCG), which had conventional infrastructures on 3 regular-length Morse taper implants (4x11?mm); Regular Splinted Pontic Group (RPG), which had infrastructures with intermediate pontics on 2 regular-length Morse taper implants (4x11?mm). The simulations of the groups were created with Ansys Workbench 10.0 software. The results revealed that the RPG presented greater areas of possible fragility due to higher stress concentrations, for example, in the cervical area of the union between the implant and component the top platform of the abutment, as well as greater coverage of the stress by the cervical implant threads. The RPG infrastructure was also more affected by stresses in the connection areas between the prostheses and on the occlusal surface. There is an advantage to using prostheses supported by a greater number of implants (RCG) because this decreases the stress in the analyzed structures and consequently improves stress dissipation to the supporting bone, which would preserve the system. 相似文献
24.
Rita Flix Soares Ana Rita Garcia Ana Raquel Monteiro Filipa Macedo Tatiana Cunha Pereira Joana Cunha Carvalho Antnio Pêgo Mnica Mariano Pedro Madeira Sara Pvoa Sofia Broco Teresa Carvalho Isabel Pazos Gabriela Sousa 《Reports of Practical Oncology and Radiotherapy》2021,26(4):563
BackgroundTriple negative breast cancer (TNBC) has the worst prognosis amongst all subtypes. Studies have shown that the achievement of pathologic complete response in the breast and axilla correlates with improved survival. The aim of this study was to identify clinical or pathological features of real-life TNBC patients with a higher risk of early relapse.Materials and methodsSingle-centre retrospective analysis of 127 women with TNBC, stage II–III, submitted to neoadjuvant treatment and surgery between January 2016 and 2020. Multivariate Cox regression analysis for disease free survival (DFS) at 2 years was performed and statistically significant variables were computed into a prognostic model for early relapse.ResultsAfter 29 months of median follow-up, 105 patients (82.7%) were alive and, in total, 38 patients (29.9%) experienced recurrence. The 2-year DFS was 73% (95% CI: 21.3–22.7). In multivariate analysis, being submitted to neoadjuvant radiotherapy [HR 2.8 (95% CI: 1.2–6.4), p = 0.017] and not achieving pathologic complete response [HR 0.3 (95% CI: 0.1–1.7), p = 0.011] were associated with higher risk of recurrence. In our prognostic model, the presence of at least one of these variables defined a subgroup of patients with a worse 2-year DFS than those without these features (59% vs. 90%, p < 0.001, respectively).ConclusionsIn this real-life non-metastatic TNBC cohort, neoadjuvant radiotherapy (performed due to insufficient clinical response to neoadjuvant chemotherapy or significant toxicity) impacted as an independent prognostic factor for relapse along with the absence of pathologic complete response identifying a subgroup of higher risk patients for early relapse that might merit a closer follow-up. 相似文献
25.
Mammalian prion proteins (PrPs) that cause transmissible spongiform encephalopathies are misfolded conformations of the host cellular PrP. The misfolded form, the scrapie PrP (PrPSc), can aggregate into amyloid fibrils that progressively accumulate in the brain, evolving to a pathological phenotype. A particular characteristic of PrPSc is to be found as different strains, related to the diversity of conformational states it can adopt. Prion strains are responsible for the multiple phenotypes observed in prion diseases, presenting different incubation times and diverse deposition profiles in the brain. PrP biochemical properties are also strain-dependent, such as different digestion pattern after proteolysis and different stability. Although they have long been studied, strain formation is still a major unsolved issue in prion biology. The recreation of strain-specific conformational features is of fundamental importance to study this unique pathogenic phenomenon. In our recent paper, we described that murine PrP, when expressed in bacteria, forms amyloid inclusion bodies that possess different strain-like characteristics, depending on the PrP construct. Here, we present an extra-view of these data and propose that bacteria might become a successful model to generate preparative amounts of prion strain-specific assemblies for high-resolution structural analysis as well as for addressing the determinants of infectivity and transmissibility. 相似文献
26.
Bulk hydrogen stable isotope composition of seaweeds: Clear separation between Ulvophyceae and other classes 下载免费PDF全文
Matheus C. Carvalho Pedro Bastos de Macedo Carneiro Fernando Gaspar Dellatorre Pablo Ezequiel Gibilisco Julian Sachs Bradley D. Eyre 《Journal of phycology》2017,53(5):961-969
Little is known about the bulk hydrogen stable isotope composition (δ2H) of seaweeds. This study investigated the bulk δ2H in several different seaweed species collected from three different beaches in Brazil, Australia, and Argentina. Here, we show that Ulvophyceae (a group of green algae) had lower δ2H values (between ?94‰ and ?130‰) than red algae (Florideophyceae), brown algae (Phaeophyceae), and species from the class Bryopsidophyceae (another group of green algae). Overall the latter three groups of seaweeds had δ2H values between ?50‰ and ?90‰. These findings were similar at the three different geographic locations. Observed differences in δ2H values were probably related to differences in hydrogen (H) metabolism among algal groups, also observed in the δ2H values of their lipids. The marked difference between the δ2H values of Ulvophyecae and those of the other groups could be useful to trace the food source of food webs in coastal rocky shores, to assess the impacts of green tides on coastal ecosystems, and to help clarify aspects of their phylogeny. However, reference materials for seaweed δ2H are required before the full potential of using the δ2H of seaweeds for ecological studies can be exploited. 相似文献
27.
Phylogeography of the dry vegetation endemic species Nephila sexpunctata (Araneae: Araneidae) suggests recent expansion of the Neotropical Dry Diagonal 下载免费PDF全文
28.
Comparison of chlorophyll and carotenoid concentrations among Russian wheat aphid (Homoptera: Aphididae)-infested wheat isolines 总被引:1,自引:0,他引:1
Heng-Moss TM Ni X Macedo T Markwell JP Baxendale FP Quisenberry SS Tolmay V 《Journal of economic entomology》2003,96(2):475-481
Russian wheat aphid, Diuraphis noxia (Mordvilko), feeding injury on 'Betta' wheat isolines with the Dn1 and Dn2 genes was compared by assessing chlorophyll and carotenoid concentrations, and aphid fecundity. The resistant Betta isolines (i.e., Betta-Dn1 and Betta-Dn2) supported similar numbers of aphids, but had significantly fewer than the susceptible Betta wheat, indicating these lines are resistant to aphid feeding. Diuraphis noxia feeding resulted in different responses in total chlorophyll and carotenoid concentrations among the Betta wheat isolines. The infested Betta-Dn2 plants had higher levels of chlorophylls and carotenoids in comparison with uninfested plants. In contrast, infested Betta-Dn1 plants had the same level of chlorophyll and carotenoid in comparison with uninfested plants. Our data provide essential information on the effect of D. noxia feeding on chlorophyll and carotenoid concentrations for Betta wheat and its isolines with D. noxia-resistant Dn1 and Dn2 genes. 相似文献
29.
The relationship between dental morphology, sex, body length and age of small cetaceans can be used to determine ontogeny, sexual dimorphism and geographical variation. The objective of this study was to determine the relationship between dental morphology, sex, body size and age. A total of 91 specimens of P. blainvillei and 80 specimens of S. fluviatilis accidentally captured in fisheries or stranded in northern Rio de Janeiro (21 masculine37'-22 masculine25'S), from September 1988 to November 1996 were analysed. The teeth root diameter in P. blainvillei was significantly different between the sex; the values for females were larger than males. In neither species aid we observed significant in variations dimension and number of teeth, thickness of dentine and cemental layers and in the maximum width of cement as a function of body size. Age was related to increases in tooth length, root and cingulum diameters, and maximum width of cement in individuals of P. blainvillei, and tooth and crown lengths and maximum width of cement in individuals of S. fluviatilis. The observation of a linear growth between maximum width of cement and age in both species indicates that the equations obtained can be used to estimate relative age in P. blainvillei and S. fluviatilis in northern of Rio de Janeiro. 相似文献
30.
Nakahira M Macedo JN Seraphim TV Cavalcante N Souza TA Damalio JC Reyes LF Assmann EM Alborghetti MR Garratt RC Araujo AP Zanchin NI Barbosa JA Kobarg J 《PloS one》2010,5(11):e13799