全文获取类型
收费全文 | 5486篇 |
免费 | 325篇 |
国内免费 | 1篇 |
出版年
2023年 | 28篇 |
2022年 | 44篇 |
2021年 | 128篇 |
2020年 | 82篇 |
2019年 | 114篇 |
2018年 | 163篇 |
2017年 | 156篇 |
2016年 | 199篇 |
2015年 | 281篇 |
2014年 | 283篇 |
2013年 | 357篇 |
2012年 | 457篇 |
2011年 | 376篇 |
2010年 | 267篇 |
2009年 | 202篇 |
2008年 | 282篇 |
2007年 | 235篇 |
2006年 | 211篇 |
2005年 | 354篇 |
2004年 | 298篇 |
2003年 | 271篇 |
2002年 | 133篇 |
2001年 | 102篇 |
2000年 | 107篇 |
1999年 | 72篇 |
1998年 | 44篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 20篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 29篇 |
1991年 | 38篇 |
1990年 | 35篇 |
1989年 | 25篇 |
1988年 | 28篇 |
1987年 | 30篇 |
1986年 | 14篇 |
1985年 | 30篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1979年 | 16篇 |
1978年 | 22篇 |
1977年 | 17篇 |
1976年 | 13篇 |
1975年 | 14篇 |
1974年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有5812条查询结果,搜索用时 15 毫秒
991.
Silva LD Rocha AM Rocha GA de Moura SB Rocha MM Dani R de Melo FF Guerra JB de Castro LP Mendes GS Ferrari TC Lima AS Queiroz DM 《Memórias do Instituto Oswaldo Cruz》2011,106(6):748-754
The hypothesis that Helicobactermight be a risk factor for human liver diseases has arisen after the detection of Helicobacter DNA in hepatic tissue of patients with hepatobiliary diseases. Nevertheless, no explanation that justifies the presence of the bacterium in the human liver has been proposed. We evaluated the presence of Helicobacterin the liver of patients with hepatic diseases of different aetiologies. We prospectively evaluated 147 patients (106 with primary hepatic diseases and 41 with hepatic metastatic tumours) and 20 liver donors as controls. Helicobacter species were investigated in the liver by culture and specific 16S rDNA nested-polymerase chain reaction followed by sequencing. Serum and hepatic levels of representative cytokines of T regulatory cell, T helper (Th)1 and Th17 cell lineages were determined using enzyme linked immunosorbent assay. The data were evaluated using logistic models. Detection of Helicobacter pylori DNA in the liver was independently associated with hepatitis B virus/hepatitis C virus, pancreatic carcinoma and a cytokine pattern characterised by high interleukin (IL)-10, low/absent interferon-γ and decreased IL-17A concentrations (p < 10(-3)). The bacterial DNA was never detected in the liver of patients with alcoholic cirrhosis and autoimmune hepatitis that are associated with Th1/Th17 polarisation. H. pylori may be observed in the liver of patients with certain hepatic and pancreatic diseases, but this might depend on the patient cytokine profile. 相似文献
992.
Silva MR Guimarães MD Oliveira VM Moreira Ados S Costa RR Abi-Zaid KC Rocha Ada S Suffys PN 《Memórias do Instituto Oswaldo Cruz》2011,106(1):9-15
A cross-sectional analysis of stored Ziehl-Neelsen (ZN)-stained sputum smear slides (SSS) obtained from two public tuberculosis referral laboratories located in Juiz de Fora, Minas Gerais, was carried out to distinguish Mycobacterium bovis from other members of the Mycobacterium tuberculosis complex (MTC). A two-step approach was used to distinguish M. bovis from other members of MTC: (i) oxyR pseudogene amplification to detect MTC and, subsequently, (ii) allele-specific sequencing based on the polymorphism at position 285 of this gene. The oxyR pseudogene was successfully amplified in 100 of 177 (56.5%) SSS available from 99 individuals. No molecular profile of M. bovis was found. Multivariate analysis indicated that acid-fast bacilli (AFB) results and the source laboratory were associated (p < 0.05) with oxyR pseudogene amplification. SSS that were AFB++ SSS showed more oxyR pseudogene amplification than those with AFB0, possibly due to the amount of DNA. One of the two source laboratories presented a greater chance of oxyR pseudogene amplification, suggesting that differences in sputum conservation between laboratories could have influenced the preservation of DNA. This study provides evidence that stored ZN-SSS can be used for the molecular detection of MTC. 相似文献
993.
Ferreira JL Borborema SE Brígido LF Oliveira MI Paiva TM Santos CL 《Memórias do Instituto Oswaldo Cruz》2011,106(5):613-616
In this paper, we analysed the haemagglutinin (HA) gene identified by polymerase chain reaction from 90 influenza A H1N1 virus strains that circulated in Brazil from April 2009-June 2010. A World Health Organization sequencing protocol allowed us to identify amino acid mutations in the HA protein at positions S220T (71%), D239G/N/S (20%), Y247H (4.5%), E252K (3.3%), M274V (2.2%), Q310H (26.7%) and E391K (12%). A fatal outcome was associated with the D239G mutation (p < 0.0001). Brazilian HA genetic diversity, in comparison to a reference strain from California, highlights the role of influenza virus surveillance for study of viral evolution, in addition to monitoring the spread of the virus worldwide. 相似文献
994.
de Melo ME Cabral AB Maciel MA da Silveira VM de Souza Lopes AC 《Current microbiology》2011,62(5):1596-1601
The objectives of this study were to determine the distribution of phylogenetic groups among Klebsiella pneumoniae isolates from Recife, Brazil and to assess the relationship between the groups and the isolation sites and resistance profile.
Ninety four isolates of K. pneumoniae from hospital or community infections and from normal microbiota were analyzed by gyrA PCR–RFLP, antibiotic susceptibility, and adonitol fermentation. The results revealed the distinction of three phylogenetic
groups, as it has also been reported in Europe, showing that these clusters are highly conserved within K. pneumoniae. Group KpI was dominantly represented by hospital and community isolates while groups KpII and KpIII displayed mainly normal
microbiota isolates. The resistance to third generation cephalosporins, aztreonam, imipenem, amoxicillin/clavulanic acid,
and streptomycin was only observed in KpI. The percentage of resistance was higher in KpI, followed by KpII and KpIII. The
differences in the distribution of K. pneumoniae phylogenetic groups observed in this study suggest distinctive clinical and epidemiological characteristics among the three
groups, which is important to understand the epidemiology of infections caused by this organism. This is the first study in
Brazil on K. pneumoniae isolates from normal microbiota and community infections regarding the distribution of phylogenetic groups based on the gyrA gene. 相似文献
995.
Tissue-nonspecific alkaline phosphatase (TNAP) is associated to the plasma membrane via a GPI-anchor and plays a key role in the biomineralization process. In plasma membranes, most GPI-anchored proteins are associated with "lipid rafts", ordered microdomains enriched in sphingolipids, glycosphingolipids and cholesterol. In order to better understand the role of lipids present in rafts and their interactions with GPI-anchored proteins, the insertion of TNAP into different lipid raft models was studied using dipalmitoylphosphatidylcholine (DPPC), cholesterol (Chol), sphingomyelin (SM) and ganglioside (GM1). Thus, the membrane models studied were binary systems (9:1 molar ratio) containing DPPC:Chol, DPPC:SM and DPPC:GM1, ternary systems (8:1:1 molar ratio) containing DPPC:Chol:SM, DPPC:Chol:GM1 and DPPC:SM:GM1 and finally, a quaternary system (7:1:1:1 molar ratio) containing DPPC:Chol:SM:GM1. Calorimetry analysis of the liposomes and proteoliposomes indicate that lateral phase segregation could be noted only in the presence of cholesterol, with the formation of cholesterol-rich microdomains centered above Tc=41.5°C. The presence of GM1 and SM into DPPC-liposomes influenced mainly ΔH and Δt(1/2) values. The gradual increase in the complexity of the systems decreased the activity of the enzyme incorporated. The presence of the enzyme also fluidifies the systems, as seen by the intense reduction in ?H values, but do not alter Tc values significantly. Therefore, the study of different microdomains and its biophysical characterization may contribute to the knowledge of the interactions between the lipids present in MVs and its interactions with TNAP. 相似文献
996.
Lopes-Ferreira M Magalhães GS Fernandez JH Junqueira-de-Azevedo Ide L Le Ho P Lima C Valente RH Moura-da-Silva AM 《Biochimie》2011,93(6):971-980
Lectins are glycan-binding receptors that recognize glycan epitopes on foreign pathogens and in the host systems. They can be involved in functions that include innate immunity, development, immune regulation and homeostasis. Several lectins have been purified and characterized from fish species. In this work, using cation-exchange chromatography, a galactose-specific lectin belonging to the family of C-type lectins was isolated from the venom of the Brazilian venomous fish Thalassophryne nattereri. Nattectin is a basic, non-glycosilated, 15 kDa monomeric protein. It exhibits hemagglutination activity that is independent of Ca2+. We also demonstrated a lectin activity for Nattectin in the innate immune system, especially in neutrophil mobilization in mice, indicating that marine organisms are source of immunomodulator agents. 相似文献
997.
da Silva GN Evangelista AF Magalhães DA Macedo C Búfalo MC Sakamoto-Hojo ET Passos GA Salvadori DM 《Molecular biology reports》2011,38(6):4159-4170
Urinary bladder cancer is the fourth most common malignancy in the Western world. Transitional cell carcinoma (TCC) is the
most common subtype, accounting for about 90% of all bladder cancers. The TP53 gene plays an essential role in the regulation of the cell cycle and apoptosis and therefore contributes to cellular transformation
and malignancy; however, little is known about the differential gene expression patterns in human tumors that present with
the wild-type or mutated TP53 gene. Therefore, because gene profiling can provide new insights into the molecular biology of bladder cancer, the present
study aimed to compare the molecular profiles of bladder cancer cell lines with different TP53 alleles, including the wild type (RT4) and two mutants (5637, with mutations in codons 280 and 72; and T24, a TP53 allele encoding an in-frame deletion of tyrosine 126). Unsupervised hierarchical clustering and gene networks were constructed
based on data generated by cDNA microarrays using mRNA from the three cell lines. Differentially expressed genes related to
the cell cycle, cell division, cell death, and cell proliferation were observed in the three cell lines. However, the cDNA
microarray data did not cluster cell lines based on their TP53 allele. The gene profiles of the RT4 cells were more similar to those of T24 than to those of the 5637 cells. While the deregulation
of both the cell cycle and the apoptotic pathways was particularly related to TCC, these alterations were not associated with
the TP53 status. 相似文献
998.
Noemí?Yubero ángeles?Jiménez-Marín Concepción?Lucena Manuel?Barbancho Juan?J.?GarridoEmail author 《Molecular biology reports》2011,38(2):1021-1028
The tetra-membrane-spanning protein, CD9 is a 24–27 kDa cell surface glycoprotein expressed in a wide variety of human cells
being involved in a variety of cell processes, including signaling, adhesion, motility, fertilization and tumor cells metastasis.
By means of a polyclonal antibody (N1) raised against recombinant swine CD9 protein, we studied the immunohistochemical expression
of CD9 on different normal swine tissues. Immunochemistry shows that swine CD9 was distribute in a similar form than in human
tissues, being present on epithelial cells of lung, liver, kidney, skin, tonsil, testis (epididymo), gut mucosa, uterus and
mama. Furthermore, polyclonal antibody against swine CD9 reacts with white matter from cerebrum and cerebellum, peripheral
nerves fibers and Hassal corpuscle from thymus and ovum. Platelets react strongly with our antibody, but monocytes and neutrophils
react lightly. These results suggest that CD9 antigen should play a similar functional role in swine and human and therefore
studies on CD9 on swine as an animal model would allow new knowledge about its role in adhesion, fertilization and tumor metastasis
among other important biomedical processes. 相似文献
999.
Domínguez-Machín ME Hernández-Vergara MP Jiménez-García I Simá-Alvarez R Rodríguez-Canul R 《Diseases of aquatic organisms》2011,96(2):97-103
We surveyed protozoan and metazoan parasites as well as white spot syndrome virus (WSSV) and infectious hypodermal hematopoietic necrosis virus (IHHNV) in white shrimp Litopenaeus setiferus and the palaemonid prawn Macrobrachium acanthurus native to the lower Jamapa River region of Veracruz, Mexico. The presence of parasites and the infection parameters were evaluated in 113 palaemonid prawns collected during the northwind (n = 45), rainy (n = 38) and dry seasons (n = 30) between October 2007 and July 2008, and in 91 shrimp collected in the rainy season between May and June 2008. In L. setiferus, ciliates of the subclass Apostomatia (Ascophrys sp.) were evident in gills, and third-stage larvae of the nematode Physocephalus sexalatus were evident in the stomach. Cestodes of the genus Prochristianella were evident in the hepatopancreas, while some gregarines of the genus Nematopsis, as well as unidentified larval cestodes, were observed in the intestine. Histology identified Ascophrys sp. in association with gill necrosis and tissue melanization. Slight inflammation was observed in intestinal epithelium near cestode larvae. In M. acanthurus, epibionts of the protozoans Epistylis sp., Acineta sp. and Lagenophrys sp. were observed under uropods, periopods and pleopods. An unidentified ciliate of the Apostomatia was also found in the gills, and Nematopsis was identified in the intestine. No histopathology was observed in association with these parasites. Moreover, neither WSSV nor IHHNV were detected by the polymerase chain reaction (PCR) in any of the L. setiferus or M. acanthurus analysed. 相似文献
1000.
Simões PS Perosa SR Arganãraz GA Yacubian EM Carrete H Centeno RS Varella PP Santiago JF Canzian M Silva JA Mortara RA Amado D Cavalheiro EA Mazzacoratti Mda G 《Neurochemistry international》2011,58(4):477-482
Kallikrein 1 (hK1) is a tissue enzyme responsible for kinin release in inflammatory cascade. This study was delineated to study the distribution and the co-localization of hK1 and kinin B1 and B2 receptors with glial and/or neuronal proteins markers, in the hippocampus of patients with refractory temporal lobe epilepsy, associated with hippocampal sclerosis (TLE-HS), comparing with control tissues. Hippocampal levels of KLK1 mRNA were also measured. hK1, kinin B1 and B2 receptors, NeuN and GFAP were analyzed using immunohistochemistry and confocal microscopy and KLK1 mRNA was quantified with real time PCR. Increased expression of hK1 by astrocytes co-localized with GFAP was found, contrasting with kinin B1 and B2 receptors, which were co-localized with NeuN in the sclerotic hippocampus. In addition, KLK1 mRNA was also up-regulated in same tissues. These data suggest an overexpression of kallikrein-kinin system and a neuron-glia interaction in the inflammatory process present in refractory TLE-HS. 相似文献