全文获取类型
收费全文 | 6363篇 |
免费 | 445篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 43篇 |
儿科学 | 221篇 |
妇产科学 | 231篇 |
基础医学 | 930篇 |
口腔科学 | 114篇 |
临床医学 | 887篇 |
内科学 | 1192篇 |
皮肤病学 | 132篇 |
神经病学 | 531篇 |
特种医学 | 126篇 |
外科学 | 485篇 |
综合类 | 67篇 |
一般理论 | 22篇 |
预防医学 | 755篇 |
眼科学 | 146篇 |
药学 | 414篇 |
中国医学 | 5篇 |
肿瘤学 | 527篇 |
出版年
2023年 | 71篇 |
2022年 | 94篇 |
2021年 | 153篇 |
2020年 | 156篇 |
2019年 | 174篇 |
2018年 | 183篇 |
2017年 | 166篇 |
2016年 | 146篇 |
2015年 | 182篇 |
2014年 | 287篇 |
2013年 | 386篇 |
2012年 | 510篇 |
2011年 | 507篇 |
2010年 | 273篇 |
2009年 | 255篇 |
2008年 | 438篇 |
2007年 | 458篇 |
2006年 | 413篇 |
2005年 | 398篇 |
2004年 | 373篇 |
2003年 | 314篇 |
2002年 | 291篇 |
2001年 | 34篇 |
2000年 | 24篇 |
1999年 | 32篇 |
1998年 | 58篇 |
1997年 | 53篇 |
1996年 | 35篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 31篇 |
1992年 | 19篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1972年 | 8篇 |
排序方式: 共有6828条查询结果,搜索用时 15 毫秒
31.
Novel Method for Processing Respiratory Specimens for Detection of Mycobacteria by Using C18-Carboxypropylbetaine: Blinded Study 总被引:1,自引:0,他引:1 下载免费PDF全文
Charles G. Thornton Kerry M. MacLellan Thomas L. Brink Jr. Denise E. Lockwood Mark Romagnoli June Turner William G. Merz Richard S. Schwalbe Marcia Moody Yvonne Lue Selvin Passen 《Journal of clinical microbiology》1998,36(7):1996-2003
A novel method for processing respiratory specimens to improve culture and acid-fast staining of mycobacteria is introduced. This new method utilized N,N-dimethyl-N-(n-octadecyl)-N-(3-carboxypropyl)ammonium inner salt (Chemical Abstract Service no. 78195-27-4), also known as C18-carboxypropylbetaine (CB-18). In a blinded, five-center study, CB-18-based processing was compared to the standard method combining NALC and NaOH (NALC/NaOH). A total of 573 respiratory specimens were tested. Individual specimens were split approximately equally; the host institutions processed half of each specimen by the NALC/NaOH method, while the other half was processed with CB-18 at Quest Diagnostics—Baltimore. A total of 106 specimens were culture positive for acid-fast bacilli (AFB). Replacement of the primary decontamination agent with CB-18 caused changes in all diagnostic parameters. Aggregate culture sensitivity improved by approximately 43% (P < 0.01), and smear sensitivity improved by approximately 58% (P < 0.01). The sensitivity of smear relative to that of M. tuberculosis isolates exceeded 93% (P < 0.01) when specimens were processed with CB-18. The average times to a positive result were reduced by 7.3 days in liquid culture (P < 0.01) and 5.3 days on solid media (P < 0.05); however, the CB-18 method had a 20.8% contamination rate in liquid culture versus a rate of approximately 7.5% with NALC/NaOH processing. There were also unusual reductions in liquid culture sensitivity and smear specificity among CB-18-processed specimens. The characteristics of the latter parameters suggested that refinement of the CB-18 processing method should allow further improvements in culture sensitivity. This study showed that the CB-18 method has the potential to improve both smear and culture detection for these important human pathogens. 相似文献
32.
Genotyping of clinical methicillin-susceptible Staphylococcus aureus isolates in a Dutch teaching hospital 下载免费PDF全文
Van Dijk Y Wielders CL Fluit AC Paauw A Diepersloot RJ Mascini EM 《Journal of clinical microbiology》2002,40(2):663-665
Methicillin-susceptible Staphylococcus aureus isolates, recovered from 204 patients in our hospital in a 22-month period, were characterized by pulsed-field gel electrophoresis. Among the multiple S. aureus types six clonal lineages dominated, comprising isolates from 158 patients. Despite the limited genetic variation, cross-transmission was made plausible only sporadically. 相似文献
33.
Robyn M. Sutherland Stephen Brassell Qiang Liu Yvonne Paterson 《European journal of immunology》1995,25(7):1810-1814
Heme is a non-protein autoantigen which is ubiquitous in vivo, primarily complexed in various hemoproteins or bound to specialized carrier molecules. Nevertheless, heme is able to stimulate a high frequency of CD4+, class II-restricted T cells, freshly explanted from unprimed mice, to proliferate in vitro. In this study, we show that heme incorporated into various species of mammalian cytochrome c (cyt c), including murine cyt c, represents a facultative cryptic determinant, able to be recalled only at high doses of native cyt c. By contrast, avian cyt c is of comparable antigenicity to free heme. Artificially denatured carboxymethylated (CM) mammalian cyt c exhibited greatly increased antigenicity, comparable to that of heme and avian cyt c, indicating that the crypticity of heme in native mammalian cyt c is due to the resistance of the native conformation of this molecule to antigen processing within murine antigen-presenting cells. Thus, tolerance to the heme group of at least some hemoproteins, may be maintained by the crypticity of the heme, rather than by deletion of hemereactive T cells. Given the high frequency of heme-reactive T cells in unprimed mice, these findings suggest that heme may become an important modulator during an inflammatory response. 相似文献
34.
Lugli A Forster Y Haas P Nocito A Bucher C Bissig H Mirlacher M Storz M Mihatsch MJ Sauter G 《Human pathology》2003,34(10):994-1000
Calretinin is a calcium-binding protein expressed in different normal and neoplastic tissues. Early studies suggested that calretinin is a useful marker to differentiate adenocarcinomas from malignant mesotheliomas of the lung, but subsequent work has shown that calretinin can be expressed in several other tumor types. To systematically investigate the epidemiology of calretinin expression in normal and neoplastic tissues, we used tissue microarrays (TMAs) to analyze the immunohistochemically detectable expression of calretinin in 5233 tissue samples from 128 different tumor categories and 76 different normal tissue types. At least 1 case with weak expression could be found in 74 of 128 (58%) different tumor types and 46 entities (36%) had at least 1 tumor with strong positivity. In normal tissues, a particularly strong expression was found in Leydig cells of the testis, neurons of the brain, theca-lutein and theca interna cells of the ovary, and mesothelium. In tumors, strong calretinin expression was most frequently found in malignant mesotheliomas (6 of 7), Leydig cell tumors of the testis (5 of 5), adenomas of adrenal gland (5 of 9), and adenomatoid tumors (4 of 9). In summary, calretinin is frequently expressed in many different tumor types. Metastases of various different origins must be included in the differential diagnosis of calretinin-positive pleura tumors. 相似文献
35.
Widdowson MA Rockx B Schepp R van der Poel WH Vinje J van Duynhoven YT Koopmans MP 《Journal of medical virology》2005,76(1):119-128
The close genetic relationship of human and animal strains of norovirus has raised the possibility of transmission of noroviruses from animals to humans and may explain the emergence of certain norovirus strains. To assess if exposure to bovine noroviruses (NoV) might result in infection in humans, an enzyme immunoassay (EIA) was designed and validated in order to detect antibodies against bovine norovirus. This and two other EIAs were used to test sera from 210 veterinarians and 630 matched population controls for IgG and IgA antibodies to recombinant capsid protein of bovine NoV (rBoV), Norwalk virus (rNV), and Lordsdale virus (rLDV). Of 840 participants, IgG reactivity to rBoV was found in 185 (22%), to rNV in 638 (76%) and to rLDV in 760 (90%). IgG reactivity to rBoV was more common in veterinarians (58/210: 28%) than in controls (127/630: 20% [P = 0.03]). IgA reactivity to rBoV was similar in both veterinarians and controls. Cross-reactivity of IgA and IgG antibodies to rBoV and rNV was seen, but 26% of all specimens positive rBoV antibodies showed high IgG reactivity to rBoV but low reactivity to rNV, suggesting a specific response to bovine antigen. No evidence of overall cross-reactivity of antibodies to rBoV and rLDV was seen. Among veterinarians, youth spent on farm (Odds Ratio [OR] = 1.8) and membership of the bovine practitioners' society (OR = 2.7) were significantly associated with IgG seroreactivity to rBoV. These data indicate that bovine strains of NoV may infect humans though less frequently than human strains. 相似文献
36.
Laura McGillis Nimish Mittal Daniel Santa Mina Joyce So Medha Soowamber Aliza Weinrib Leslie Soever Dmitry Rozenberg Louis Liu Yvonne Tse Joel Katz George S Charames Kieran Murphy Peter Vadas Maxwell P Slepian Scott Walsh Lindsay Wilson Arnon Adler Alyssa Franzese Laura Hussey Dayna‐Lynn Nevay Juan Guzman Hance Clarke 《American journal of medical genetics. Part A》2020,182(3):484-492
The new 2017 diagnostic criteria for hypermobile Ehlers–Danlos Syndrome (hEDS) provide a framework for diagnosing hEDS but are more stringent than the previous Villefranche criteria. Our clinical experience at the GoodHope EDS clinic was that the 2017 criteria left many highly symptomatic patients without a diagnosis of hEDS. We conducted a retrospective cohort study to confirm our clinic experience and assess the accuracy of the 2017 diagnostic criteria for hEDS in patients who had a previous hEDS diagnosis based on the Villefranche criteria. Our study found that 15% (n = 20 of 131) of patients with a prior diagnosis of hEDS met the 2017 diagnostic criteria, and many of the traits used to distinguish hEDS were not significantly more frequent in patients who met 2017 criteria versus those who did not. In both groups objective systemic manifestations were found less frequently than subjective systemic manifestations. Beighton score (BS) as assessed by primary care practitioner was found to be higher than assessment by EDS practitioner in 81% (n = 74 of 91) of cases. Generalized joint hypermobility was confirmed in only 46% (n = 51 of 111) of patients who had a previous diagnosis of hEDS. Higher BS did not correlate with increased number of systemic manifestations in our cohort. Common comorbidities of hEDS were found with similar frequency in those who met 2017 criteria and those who did not. Based on our cohort, the 2017 hEDS diagnostic criteria require refinement to improve its diagnostic accuracy. 相似文献
37.
Gene amplifications have been observed in many different tumor cells, and many of these changes are related to tumor pathogenesis. Comparative genomic hybridization (CGH) using metaphase chromosomes can detect changes in chromosome copy number with a resolution of 10-20 Mb. Current advances in CGH analysis in a microarray format allow us to refine such changes down to the gene level. We applied microarray technology to detect novel gene amplification in a malignant mixed tumor of salivary gland. Besides detecting previously known gene amplifications (MDM2 and MYC), we identified four other highly amplified genes located at 8q11.2 approximately q13: MGC2177, PLAG1, PSMC6P, and LYN. The amplification was further validated with real-time quantitative polymerase chain reaction. 相似文献
38.
The dielectrophoretic collection spectra of antibiotic-sensitive and antibiotic-resistant strains of Staphylococcus epidermidis have been determined. These indicate that in the absence of antibiotic treatment there is a strong similarity between the dielectric properties of sensitive and resistant strains, and that there is a significant difference between the sensitive strains before and after treatment with the antibiotic streptomycin after 24 h exposure. This method offers possibilities for the assessment of bacterial resistance to antibiotics. 相似文献
39.
Liposome-mediated gene transfer and expression via the skin 总被引:2,自引:1,他引:2
A ß-galactosidase gene expression construct was usedto investigate the effectiveness of gene delivery and expressionwhen DNA/liposome complexes were topically applied to mouseskin in vivo. DNA was complexed with a commercial preparationof N-[1-(2,3-dioleoyloxy) propyl]-N, N, N-trimethyl-ammonium-methyl-sulphate(DOTAP) in a ratio of 1:1.6 (w/w). The DNA rapidly penetratedthe skin and was expressed in the epidermis, dermis and hairfollicles. A DNA concentration of 267 µg/ml DNA was foundto be optimal for efficient transfection. Expression was seenas early as 6 h post-application, persisted at high levels 24and 48 h post-treatment, but was markedly reduced by 7 daysafter application. In conclusion, utilising a commercially availableliposome preparation, topically-applied DNA/liposome complexescan be efficiently delivered and expressed in several cell typeswithin the skin. This simple, non-invasive technique may haveimplications for a number of gene therapy applications. 相似文献
40.
Although the effect of IL-15 has been described on murine cells in vitro and in vivo, its effect on human memory CD8(+) T cells is not well characterized. We show here that IL-15 preferentially enhances the activation and effector function of human effector-memory CD45RA(-)CD62L(-) and CD45RA(+)CD62L(-) CD4(+) and CD8(+) T cells in both healthy and HIV-infected individuals. We find that IL-15 increases 2- to 5-fold both the activation and secretion of the effector cytokines IFN-gamma and tumor necrosis factor (TNF)-alpha by anti-CD3-stimulated purified CD4(+) and CD8(+) T cells and peripheral blood mononuclear cells from healthy and HIV-infected individuals. Furthermore, IL-15 potently inhibits CD95/Fas-induced apoptosis of the effector-memory CD4(+) and CD8(+) T cells from HIV-infected individuals. These findings suggest that in addition to being a growth and survival factor for memory CD8(+) T cells, IL-15 is also a potent activator of human effector-memory CD8(+) T cells both in healthy and in HIV-infected individuals. 相似文献