全文获取类型
收费全文 | 422篇 |
免费 | 51篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 18篇 |
妇产科学 | 1篇 |
基础医学 | 49篇 |
口腔科学 | 13篇 |
临床医学 | 71篇 |
内科学 | 99篇 |
皮肤病学 | 15篇 |
神经病学 | 7篇 |
特种医学 | 148篇 |
外科学 | 10篇 |
综合类 | 12篇 |
预防医学 | 14篇 |
眼科学 | 8篇 |
药学 | 41篇 |
肿瘤学 | 13篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 37篇 |
2006年 | 4篇 |
2005年 | 8篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 18篇 |
1998年 | 31篇 |
1997年 | 34篇 |
1996年 | 29篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 23篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 15篇 |
1985年 | 19篇 |
1984年 | 5篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1975年 | 5篇 |
排序方式: 共有520条查询结果,搜索用时 15 毫秒
31.
32.
Helen M. Hallgren Duaine R. Jackola James J. O''Leary 《Mechanisms of ageing and development》1985,30(3):239-250
In a previous report, we described an unusual pattern of T cell associated surface marker expression in unfractionated mononuclear cells from aged donors; an excess of T4 and T8 positive cells relative to T3 positive cells. This study further characterizes these cells on the basis of density, adherence to nylon wool and quantitative expression of cell surface markers. We find that the population of lymphocytes responsible for the unusual surface marker expression is of low density, adheres to nylon wool, and is present in small numbers in young donors. The adherent cells have a reduced quantitative expression of the T3 antigen, no change in the antigen density of T4 and T8, and have increased expression of the T10 antigen. These cells do not have the characteristics of large granular lymphocytes, monocytes, B cells with unusual marker expression, or thymocytes poised for export to peripheral blood. We suggest that these cells, found in increased numbers in aged humans, may represent an expansion of a population of T lymphocytes with absent or reduced T3 antigen expression found normally in smaller numbers in young adults. T lymphocyte antigen receptor density has been quantitatively linked to expression of the T3 antigen. Thus, our results imply that aging may lead to decreased T cell surface antigen density, which may account in part for decline in T cell function with age. 相似文献
33.
Gazitt Y; Reading CC; Hoffman R; Wickrema A; Vesole DH; Jagannath S; Condino J; Lee B; Barlogie B; Tricot G 《Blood》1995,86(1):381-389
High-dose therapy with autologous marrow or peripheral blood stem cell (PBSC) rescue has been extensively applied in the treatment of multiple myeloma (MM) patients during the past 10 years resulting in improved event-free and overall survival when compared with standard chemotherapy. However, relapses are common and cure is unlikely in the majority of patients. Because both bone marrow and PBSCs are contaminated with myeloma cells it is conceivable that relapse after autotransplantation originates at least in part from autografted tumor cells. In this study, mobilized PBSCs were examined for the presence of myeloma cells based on immunophenotyping and sensitive polymerase chain reaction (PCR)-based techniques. In addition, CD34+ Lin- Thy+ stem cells were purified from mobilized PBSC harvests of 10 MM patients by sequentially using counterflow elutriation centrifugation, treatment with phenylalanine methylester, and flow sorting, using 5-parameter gating (propidium iodide, forward scatter, side scatter, CD34+ v Lin- and CD34+ v Thy+). Virtually all mobilized unsorted PBSC preparations contained myeloma cells in sufficient quantities (range, < 0.01 to > 10%) potentially causing a disease relapse. Stem cell purification led to an overall enrichment by about 50-fold in all 10 patients; approximately 90% of the final cell population expressed CD34+ Lin- Thy+ with no evidence of myeloma cell contamination based on flow cytometric analysis of CD38bright cells (< 0.1%). Quantitative PCR amplification of patient-specific complementarity determining region III (CDRIII) DNA sequences showed depletion of clonal B cells by 2.7 to 7.3 logs, with the highest log reduction noted in the samples initially containing the most tumor cells. Our results show that purification of CD34+ Lin- Thy+ cells depletes myeloma cells to undetectable levels from up to 10% present in unsorted PBSCs, thus offering a tool to investigate whether MM relapse after autotransplantation can be reduced markedly. 相似文献
34.
35.
Femke?DH?Koedijk Birgit?HB?van BenthemEmail author Eliane?MDC?Vrolings Wim?Zuilhof Marianne?AB?van der Sande 《Emerging themes in epidemiology》2014,11(1):12
Background
Men having sex with men (MSM) remain the largest high-risk group involved in on-going transmission of sexually transmitted infections (STI), including HIV, in the Netherlands. As risk behaviour may change with age, it is important to explore potential heterogeneity in risks by age. To improve our understanding of this epidemic, we analysed the prevalence of and risk factors for selected STI in MSM attending STI clinics in the Netherlands by age group.Methods
Analysis of data from the national STI surveillance system for the period 2006–2012. Selected STI were chlamydia, gonorrhoea, infectious syphilis and/or a new HIV infection. Logistic regression was used to identify factors associated with these selected STI and with overall STI positivity. Analyses were done separately for MSM aged younger than 25 years and MSM aged 25 years and older.Results
In young MSM a significant increase in positivity rate was seen over time (p?<?0.01), mainly driven by increasing gonorrhoea diagnoses, while in MSM aged 25 and older a significant decrease was observed (p?<?0.01). In multivariate analyses for young MSM, those who were involved in commercial sex were at higher risk (OR: 1.5, 95% CI: 1.2-1.9). For MSM aged 25 years and older this was not the case. Having a previous negative HIV test was protective among older MSM compared to those not tested for HIV before (OR: 0.8, 95% CI: 0.8-0.8), but not among younger MSM.Conclusions
MSM visiting STI clinics remain a high-risk group for STI infections and transmission, but are not a homogenous group. While in MSM aged older than 25 years, STI positivity rate is decreasing, positivity rate in young MSM increased over time. Therefore specific attention needs to be paid towards targeted counselling and reaching particular MSM sub-groups, taken into account different behavioural profiles.36.
37.
Acute bronchial obstruction by mucous plugs may be manifested clinically by dyspnea, hypoxemia, and respiratory alkalosis mimicking pulmonary thromboembolism. In eight cases with complete interruption of ventilation to an entire lung, chest radiography failed to reveal the extent of the obstruction. Perfusion was substantially less affected than ventilation. Routine ventilation-perfusion scintigraphy with technetium-99m DTPA aerosol aids in the diagnosis of acute major bronchial obstruction in patients with suspected pulmonary thromboembolism. 相似文献
38.
A prospective evaluation of color flow mapping and real-time ultrasound was performed to determine if pseudoaneurysms could be distinguished from other causes of masses surrounding vascular grafts of the lower extremities. Twelve palpable pulsatile masses were imaged. Diagnoses were confirmed at angiography (n = 11), computed tomography (n = 7), aspiration biopsy (n = 5), and operative intervention (n = 6). A swirling pattern of blood flow was seen in six of seven cases of pseudoaneurysm. Lack of flow signals was noted in four of the five collections representing hematoma (n = 2) or infection (n = 2). The seventh case was later shown to be an infected, thrombosed pseudoaneurysm. The single false-positive diagnosis was made early in the series when the flow signals detected were due to transmitted arterial pulsations. The authors conclude that color Doppler flow imaging is useful in the differential diagnosis of pulsatile masses associated with prosthetic grafts. Prosthetic graft pseudoaneurysms have a specific appearance of swirling blood flow arising from a wide neck and are distinguishable from traumatic or iatrogenic pseudoaneurysms of the native vascular tree. 相似文献
39.
40.