全文获取类型
收费全文 | 15748篇 |
免费 | 756篇 |
国内免费 | 93篇 |
专业分类
耳鼻咽喉 | 235篇 |
儿科学 | 308篇 |
妇产科学 | 279篇 |
基础医学 | 1915篇 |
口腔科学 | 1130篇 |
临床医学 | 1212篇 |
内科学 | 3756篇 |
皮肤病学 | 321篇 |
神经病学 | 1291篇 |
特种医学 | 329篇 |
外科学 | 2424篇 |
综合类 | 81篇 |
一般理论 | 7篇 |
预防医学 | 1159篇 |
眼科学 | 280篇 |
药学 | 928篇 |
中国医学 | 69篇 |
肿瘤学 | 873篇 |
出版年
2024年 | 14篇 |
2023年 | 152篇 |
2022年 | 305篇 |
2021年 | 576篇 |
2020年 | 355篇 |
2019年 | 469篇 |
2018年 | 557篇 |
2017年 | 384篇 |
2016年 | 410篇 |
2015年 | 479篇 |
2014年 | 692篇 |
2013年 | 826篇 |
2012年 | 1333篇 |
2011年 | 1380篇 |
2010年 | 778篇 |
2009年 | 662篇 |
2008年 | 1080篇 |
2007年 | 1036篇 |
2006年 | 912篇 |
2005年 | 891篇 |
2004年 | 756篇 |
2003年 | 616篇 |
2002年 | 586篇 |
2001年 | 115篇 |
2000年 | 123篇 |
1999年 | 127篇 |
1998年 | 117篇 |
1997年 | 78篇 |
1996年 | 68篇 |
1995年 | 61篇 |
1994年 | 54篇 |
1993年 | 50篇 |
1992年 | 45篇 |
1991年 | 40篇 |
1990年 | 36篇 |
1989年 | 30篇 |
1988年 | 22篇 |
1987年 | 35篇 |
1986年 | 41篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 25篇 |
1980年 | 21篇 |
1979年 | 19篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1974年 | 19篇 |
1972年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Surface-Associated Hsp60 Chaperonin of Legionella pneumophila Mediates Invasion in a HeLa Cell Model 总被引:6,自引:0,他引:6 下载免费PDF全文
HeLa cells have been previously used to demonstrate that virulent strains of Legionella pneumophila (but not salt-tolerant avirulent strains) efficiently invade nonphagocytic cells. Hsp60, a member of the GroEL family of chaperonins, is displayed on the surface of virulent L. pneumophila (R. A. Garduño et al., J. Bacteriol. 180:505–513, 1988). Because Hsp60 is largely involved in protein-protein interactions, we investigated its role in adherence-invasion in the HeLa cell model. Hsp60-specific antibodies inhibited the adherence and invasiveness of two virulent L. pneumophila strains in a dose-dependent manner but had no effect on the association of their salt-tolerant avirulent derivatives with HeLa cells. A monospecific anti-OmpS (major outer membrane protein) serum inhibited the association of both virulent and avirulent strains of L. pneumophila to HeLa cells, suggesting that while both Hsp60 and OmpS may mediate bacterial association to HeLa cells, only virulent strains selectively displayed Hsp60 on their surfaces. Furthermore, the surface-associated Hsp60 of virulent bacterial cells was susceptible to the action of trypsin, which rendered the bacteria noninvasive. Additionally, pretreatment of HeLa cells with purified Hsp60 or precoating of the plastic surface where HeLa cells attached with Hsp60 reduced the adherence and invasiveness of the two virulent strains. Finally, recombinant Hsp60 covalently bound to latex beads promoted the early association of beads with HeLa cells by a factor of 20 over bovine serum albumin (BSA)-coated beads and competed with virulent strains for association with HeLa cells. Hsp60-coated beads were internalized in large numbers by HeLa cells and remained in tight endosomes that did not fuse with other vesicles, whereas internalized BSA-coated beads, for which endocytic trafficking is well established, resided in more loose or elongated endosomes. Mature intracellular forms of L. pneumophila, which were up to 100-fold more efficient than agar-grown bacteria at associating with HeLa cells, were enriched for Hsp60 on the bacterial surface, as determined by immunolocalization techniques. Collectively, these results establish a role for surface-exposed Hsp60 in invasion of HeLa cells by L. pneumophila. 相似文献
63.
Outbreak of carbapenem-resistant Acinetobacter baumannii producing the OXA-23 enzyme in Curitiba,Brazil 总被引:19,自引:0,他引:19
Dalla-Costa LM Coelho JM Souza HA Castro ME Stier CJ Bragagnolo KL Rea-Neto A Penteado-Filho SR Livermore DM Woodford N 《Journal of clinical microbiology》2003,41(7):3403-3406
Carbapenem-resistant Acinetobacter baumannii isolates were obtained from eight patients in two hospitals in Curitiba, Brazil. The isolates were multiresistant, belonged to a single strain, and produced the OXA-23 carbapenemase. Treatment options were limited, although the isolates were susceptible to polymyxin B in vitro. The strain contributed to the deaths of five patients. 相似文献
64.
Allele-Specific PCR Method Based on pncA and oxyR Sequences for Distinguishing Mycobacterium bovis from Mycobacterium tuberculosis: Intraspecific M. bovis pncA Sequence Polymorphism 总被引:1,自引:0,他引:1 下载免费PDF全文
Luz Elena Espinosa de los Monteros Juan Carlos Galn Montserrat Gutirrez Sofía Samper Juan F. García Marín Carlos Martín Lucas Domínguez Luis de Rafael Fernando Baquero Enrique Gmez-Mampaso Jesús Blzquez 《Journal of clinical microbiology》1998,36(1):239-242
An allele-specific amplification method based on two genetic polymorphisms to differentiate Mycobacterium tuberculosis from Mycobacterium bovis was tested. Based on the differences found at position 169 in the pncA genes from M. tuberculosis and M. bovis, a PCR system which was able to differentiate most of the 237 M. tuberculosis complex isolates tested in one of the two species was developed. All 121 M. tuberculosis strains showed the expected base (cytosine) at position 169. Most of the M. bovis isolates had a guanine at the cited position. Nevertheless, 18 of the 116 M. bovis isolates, all of them goat isolates, showed the pncA polymorphism specific to M. tuberculosis. These results suggest that goat M. bovis may be the nicotinamidase-missing link at the origin of the M. tuberculosis species. Based on the polymorphism found at position 285 in the oxyR gene, the same system was used to differentiate M. tuberculosis from M. bovis. In this case, DNAs from all 121 M. tuberculosis isolates had the expected base (guanine) at this position. In addition, all 116 M. bovis isolates, including those from goats, showed the identical polymorphism (adenine). The oxyR allele-specific amplification method can differentiate M. bovis from M. tuberculosis, is rapid (results can be obtained in less than 3 h), and is easy to perform. 相似文献
65.
Antonio López-Beltrán Alfonso S. Calañas Pilar Jimena Alberto L. Escudero Telma R. Campello Manuel Muñoz-Torres Fernando Escobar-Jiménez Rafael E. Carvia F. F. Nogales 《Virchows Archiv : an international journal of pathology》1997,431(2):149-151
Three further cases of mature benign cystic teratomas of the ovary associated with virilization are added to the three previously
reported in the literature. They were found in postmenopausal, obese, diabetic women aged 52, 61, and 67 years. The patients
presented with hirsutism and voice changes and clitoromegaly was present in one. Testosterone and androstenedione levels were
elevated but promptly regressed after removal of the tumours. Histologically, sheets of stromal luteinized cells were found
peripherally at the interface between the neoplasm and ovarian tissue. Luteinization of ovarian stroma induced by an unknown
factor related to diabetes mellitus is the origin of the virilization.
Received: 8 January 1997 / Accepted: 28 February 1997 相似文献
66.
Isabel M. Coelho Maria Teresa Pereira G. Virella R. A. Thompson 《Clinical and experimental immunology》1974,17(4):685-689
The saliva of an individual with selective IgA deficiency was found to contain IgG and IgM, with some of the IgM linked to secretory component. Some specimens showed evidence of low molecular weight immunoglobulin fragments, presumed to be the result of proteolysis. 相似文献
67.
Transmissible spongiform encephalopathies (TSE) are attributed to the conversion of the cellular prion protein (PrP(c)) into an abnormal isoform (PrP(sc)). This can be caused by the invasion of living organisms by infectious particles, or be inherited due to mutations on the PrP(c) gene. One of the most intriguing problems of prion biology is the inability to generate the infectious agent in vitro. This argues strongly that other cellular proteins besides those added in test tubes or found in cellular preparations are necessary for infection. Despite recent progress in the understanding of prion pathology, the subcellular compartments in which the interaction and conversion of PrP(c) into PrP(sc) take place are still controversial. PrP(c) interacts with various macromolecules at the cell membrane, in endocytic compartments and in the secretory pathway, all of which may play specific roles in the internalisation of PrP(sc) and conversion of PrP(c). A specific interacting protein required for the propagation of prions was originally proposed as a prion receptor, and later referred to as a ligand, a cofactor, protein X, or a partner. However, current studies indicate that PrP(c) associates with multi-molecular complexes, which mediate a variety of functions in distinct cellular compartments. It is proposed that a deeper understanding of the mechanics of such interactions, coupled to a better knowledge of the corresponding signalling pathways and ensuing cellular responses, will have a major impact on the prevention and treatment of TSE. 相似文献
68.
Well-characterised human osteoblastic bone marrow cell cultures are a useful in vitro tool to analyse bone tissue/biomaterials interactions. In this work, human bone marrow was cultured in experimental conditions described to favour osteoblastic differentiation and, serially passaged cells were cultured in two widely used culture media, minimum essential medium Eagle, alpha modification (alpha-MEM) and Dulbecco's modified Eagle's medium (DMEM). Cultures were grown for 35 d and compared concerning morphologic appearance on scanning electron microscopy (SEM), cell viability/proliferation, total protein content, activity of alkaline phosphatase (ALP) and ability to form calcium phosphate deposits. Results showed that cell proliferation was similar in cultures grown in the two media but ALP activity and ability to form mineralised deposits were lower in DMEM cultures. In both experimental situations, osteoblastic parameters were strongly reduced on cell passage, particularly from the first to the second subculture. In the experimental conditions used (presence of ascorbic acid, sodium beta-glycerophosphate and dexamethasone in the primary and secondary cultures), osteoblastic differentiation was observed in the first and second subcultures grown in alpha-MEM and in the first subculture grown in DMEM. These results underline the importance of the definition of the experimental conditions in studies involving bone cell cultures. 相似文献
69.
B. W. Jervis M. Coelho G. W. Morgan 《Medical & biological engineering & computing》1989,27(5):484-490
Work undertaken to investigate the effect on EEG responses of ocular artefact removal by proportional electro-oculogram subtraction
using the least-squares method is reported. The ocular artefact model and the least-squares approach to estimation of the
model parameters and hence of the EEG waveform, including the response, are described. Results are presented to show that
the response shapes become modified if ocular artefact removal is implemented recursively. This happens because the response
is incorrectly treated as part of the random background EEG. The solution is to incorporate a model of the response within
the ocular artefact removal algorithm. The results of tests on simulated data confirm these conclusions. The results of the
incorporation of response models in removing ocular artefacts from CNV recordings are presented. Even with modelling recursive
ocular artefact removal is found to modify the shape of the CNV, and so reliable results can only be obtained if the removal
is implemented nonrecursively. Evidence is given that it is advisable to remove DC levels from the recorded data. 相似文献
70.
Javier Domínguez María del Mar Lorenzo Rafael Blasco 《Journal of immunological methods》1998,220(1-2):115-121
We have tested Green Fluorescent Protein (GFP) expressed by a vaccinia virus recombinant as a marker for viral infection. Virus recombinants expressing either wild-type GFP, or a Ser65 to Thr mutated version (GFP-S65T) were used to infect cultured cells, and the appearance of fluorescence was followed during infection by flow cytometry. Although both versions were detectable in infected cells, GFP-S65T gave up to 26-fold brighter fluorescence than wild-type GFP when excited by an argon laser beam (488 nm). In addition, GFP-S65T fluorescence appeared earlier, and infected cells could be detected above background as soon as 1 h after infection. We have used this construct to infect porcine peripheral blood lymphocytes, and show its usefulness to study virus tropism when used in combination with cell-type specific markers. Thus, GFP provides a direct, fast and convenient way to monitor infection by flow cytometry. 相似文献