全文获取类型
收费全文 | 4727篇 |
免费 | 346篇 |
出版年
2023年 | 35篇 |
2022年 | 56篇 |
2021年 | 163篇 |
2020年 | 135篇 |
2019年 | 143篇 |
2018年 | 176篇 |
2017年 | 164篇 |
2016年 | 235篇 |
2015年 | 272篇 |
2014年 | 324篇 |
2013年 | 356篇 |
2012年 | 375篇 |
2011年 | 301篇 |
2010年 | 201篇 |
2009年 | 199篇 |
2008年 | 252篇 |
2007年 | 213篇 |
2006年 | 190篇 |
2005年 | 165篇 |
2004年 | 163篇 |
2003年 | 109篇 |
2002年 | 121篇 |
2001年 | 87篇 |
2000年 | 87篇 |
1999年 | 67篇 |
1998年 | 41篇 |
1997年 | 26篇 |
1996年 | 21篇 |
1995年 | 36篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 31篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 31篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1971年 | 9篇 |
1969年 | 6篇 |
1968年 | 7篇 |
排序方式: 共有5073条查询结果,搜索用时 15 毫秒
991.
Mariana Volpe Arnoni Claudete Rodrigues Paula Marcos Ereno Auler Cirilo Cesar Naozuka Simões Shirley Nakano Maria Walderez Szeszs Márcia de Souza Carvalho Melhem Virgínia Bodelão Richini Pereira Hans Garcia Garces Eduardo Bagagli Eriques Gonçalves Silva Melissa Ferreira de Macêdo Luciana da Silva Ruiz 《Mycopathologia》2018,183(6):941-949
Fusarium species have emerged as responsible for a broad spectrum of infections, including superficial, locally invasive and disseminated ones, especially in the hospital environment. Since there are few reports of invasive and disseminated fusariosis in children, the aim of this study was to report four cases of nosocomial infection caused by this microorganism in children with cancer hospitalized in a public children’s hospital located in Brazil. Two of these patients were female and two were male. All patients presented febrile neutropenia, while three patients had acute lymphocytic leukemia and one patient had Wilms’ tumor as underlying disease. In two cases, fungi were isolated from blood and identified as Fusarium oxysporum species complex after phenotypic and genotypic studies, while in two other cases fungi were isolated from skin biopsies and identified as Fusarium solani species complex. One patient died 12 days after the onset of cutaneous lesions. All isolates, after susceptibility testing, presented high levels of minimum inhibitory concentration for itraconazole, voriconazole and amphotericin B. Considering the emergence of filamentous fungi as etiologic agents of nosocomial infections, health professionals should be aware of the problems these infections, especially fungal ones, may cause to debilitated patients. 相似文献
992.
993.
Fatal primary diffuse large B‐cell lymphoma of the maxillary sinus initially treated as an infectious disease in an elderly patient: A clinicopathologic report
下载免费PDF全文
![点击此处可从《Gerodontology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mayara Santos de Castro Cínthia Magalhães Ribeiro Marina Lara de Carli Alessandro Antônio Costa Pereira Felipe Fornias Sperandio Oslei Paes de Almeida João Adolfo Costa Hanemann 《Gerodontology》2018,35(1):59-62
Objective
To report a case of primary diffuse large B‐cell lymphoma (DLBCL) of the maxillary sinus in an 82‐year‐old Caucasian woman.Background
Diffuse large B‐cell lymphoma of the maxillary sinus has non‐specific signs and symptoms that may be confused with benign inflammatory conditions and upper respiratory infections.Methods
An incisional biopsy was performed. CD20+/CD3–/Ki‐67: 95% cells were observed.Conclusion
A good medical history, clinical and imaging evaluations and immunohistochemical reactions are crucial to establish a correct and early diagnosis of DLBCL. 相似文献994.
Geraldo Jose Ferrari Junior Christopher L Drake Diego Grasel Barbosa Diego Augusto Santos Silva Gomes Felden Érico Pereira 《Chronobiology international》2018,35(8):1088-1094
The present study aimed to analyze the construct validity of the Pediatric Daytime Sleepiness Scale (PDSS) for the evaluation of the daytime sleepiness construct in adolescents through confirmatory factorial analysis. The cross-sectional study was carried out with a sample of 773 adolescents aged 14 to 19 years, enrolled in the state schools of Paranaguá, Paraná, Brazil. We investigated the sex, age, school year, study shift, occupational status, socioeconomic level and daytime sleepiness. The PDSS questions were not normal (p <0.001) and the mean total score was 14.87 (5.62). With Schwarz’s BIC adjustment indicators = 142,389 and Akaike’s AIC = 105,389, the model reached the criteria of the global adjustment indicators of the model in the confirmatory analysis, in which RMSEA = 0.020; CFI = 0.986; TLI = 0.977; SRMR = 0.021, with 17 degrees of freedom, KMO = 0.8504 and Cronbach’s Alpha = 0.737, with three correlations. We conclude that the construct validity of the PDSS remains valid and confirms its factor structure with only one factor. Thereby, it was verified that the operationalization of the construct sleepiness of adolescents through this scale is adequately conceptualized to the behavior of the age group. 相似文献
995.
Joost Willebrords Michaël Maes Isabel Veloso Alves Pereira Tereza Cristina da Silva Veronica Mollica Govoni Valéria Veras Lopes Sara Crespo Yanguas Valery I. Shestopalov Marina Sayuri Nogueira Inar Alves de Castro Anwar Farhood Inge Mannaerts Leo van Grunsven Jephte Akakpo Margitta Lebofsky Hartmut Jaeschke Bruno Cogliati Mathieu Vinken 《生物化学与生物物理学报:疾病的分子基础》2018,1864(3):819-830
996.
997.
Leonardo Kerber Marcos César Bissaro Júnior Francisco R. Negri Jonas Pereira de Souza-Filho Edson Guilherme Annie Schmaltz Hsiou 《Historical Biology》2018,30(7):985-993
Recently, the fossil record of rodents from southwestern Brazilian Amazonia has been reviewed with regards to its diversity as well as its ecological relationships. In the reviews, the necessity to report new specimens collected with stratigraphic control was stated. Here, a new dinomyid specimen collected during a 2015 expedition to the Niterói locality, Acre River, is reported. The material is a fragment of skull with the right P4–M1 and the left P4–M2 preserved. The cheek teeth are protohypsodont, a characteristic employed to differentiate Potamarchinae dinomyids from the euhypsodont dinomyids Eumegamyinae and Tetrastylinae. The occlusal surface of the cheek teeth is composed of lophs with interruptions, showing little wear, which suggests that the specimen is not fully ontogenetically developed. The specimen has a unique combination of characters (protohypsodont and pentalophodont cheek teeth, with the leading edges of similar thickness to the trailing edges, and presence of a groove on the bottom of the infraorbital foramen) not present in other known dinomyids, which led us to erect a new taxon. The abundant and diverse fossil record of protohypsodont dinomyids suggests that an important radiative event may have occurred during the middle–late Miocene of northern South America.
http://zoobank.org/urn:lsid:zoobank.org:pub:E082C3C6-47B6-4D83-9009-A64879AAFC7A
http://www.zoobank.org/NomenclaturalActs/16235A7B-A261-445E-8DD4-940AB21DCB06 相似文献
998.
The Spatial Distribution of Alkaloids in Psychotria prunifolia (Kunth) Steyerm and Palicourea coriacea (Cham.) K. Schum Leaves Analysed by Desorption Electrospray Ionisation Mass Spectrometry Imaging
下载免费PDF全文
![点击此处可从《Phytochemical analysis : PCA》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lucilia Kato Aline Pereira Moraes Cecília Maria Alves de Oliveira Boniek Gontijo Vaz Letícia de Almeida Gonçalves Elienai Cândida e Silva Christian Janfelt 《Phytochemical analysis : PCA》2018,29(1):69-76
Introduction
Species of the genera Psychotria and Palicourea are sources of indole alkaloids, however, the distribution of alkaloids within the plants is not known. Analysing the spatial distribution using desorption electrospray ionisation mass spectrometry imaging (DESI‐MSI) has become attractive due to its simplicity and high selectivity compared to traditional histochemical techniques.Objectives
To apply DESI‐MSI to visualise the alkaloid distribution on the leaf surface of Psychotria prunifolia and Palicourea coriacea and to compare the distributions with HPLC–MS and histochemical analyses.Methodology
Based upon previous structure elucidation studies, four alkaloids targeted in this study were identified using high resolution mass spectrometry by direct infusion of plant extracts, and their distributions were imaged by DESI‐MSI via tissue imprints on a porous Teflon surface. Relative quantitation of the four alkaloids was obtained by HPLC–MS/MS analysis performed using multiple‐reaction monitoring (MRM) mode on a triple quadrupole mass spectrometer.Results
Alkaloids showed distinct distributions on the leaf surfaces. Prunifoleine was mainly present in the midrib, while 10‐hydroxyisodeppeaninol was concentrated close to the petiole; a uniform distribution of 10‐hydroxyantirhine was observed in the whole leaf of Psychotria prunifolia. The imprinted image from the Palicourea coriacea leaf also showed a homogeneous distribution of calycanthine throughout the leaf surface.Conclusion
Different distributions were found for three alkaloids in Psychotria prunifolia, and the distributions found by MSI were in complete accordance with HPLC–MS analysis and histochemical results. The DESI‐MSI technique was therefore demonstrated to provide reliable information about the spatial distribution of metabolites in plants. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献999.
1000.
Tiago Fidemann Gabriela Aparecida de Araujo Pereira Tárik Reis Heluy Rodrigo Boccoli Gallego Mônica Rosa Bertão Regildo Márcio Gonçalves da Silva Eutimio Gustavo Fernández Núñez 《Plant Cell, Tissue and Organ Culture》2018,132(1):137-155
Douglas-fir is a conifer species of major economic importance worldwide, including Western Europe and New Zealand. Herein we describe some characterization and significant refinement of somatic embryogenesis in Douglas-fir, with focus on maturation. The most typical structures observed in the embryonal masses were large polyembryogenic centres (up to 800–1500 µm) with a broad meristem, creating a compact cell “package” with suspensor cells. Singulated somatic embryos composed of both a embryonal head (300–400 µm) and long, tightly arranged suspensor were also frequent. Embryo development was enhanced following embryonal mass dispersion on filter paper discs at low density (50–100 mg fresh mass). Moreover, increasing gellan gum concentration in maturation medium (up to 10 g L?1) improved both the quantity and quality of cotyledonary somatic embryos (SEs), which were subsequently able to germinate and develop into plantlets at high frequency. Embryogenic yield was highly variable among the seven embryogenic lines tested (27–1544 SE g?1 fresh mass). Interestingly secondary somatic embryogenesis could be induced from cotyledonary SEs of both low- and highly-productive lines with some useful practical outcomes: secondary lines from low-performance lines (30–478 SE g?1 fresh mass) displayed significantly higher embryogenic yield (148–1343 SE g?1 fresh mass). In our best conditions, the total protein content in cotyledonary SEs increased significantly with maturation duration (up to 150 µg mg?1 fresh mass after 7 weeks) but remained below that of mature zygotic embryos (300 µg mg?1). The protein pattern was similar in both somatic and zygotic embryos, with major storage proteins identified as 7S-vicilin- and legumin-like proteins. 相似文献