首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2108篇
  免费   174篇
  国内免费   5篇
耳鼻咽喉   10篇
儿科学   39篇
妇产科学   71篇
基础医学   490篇
口腔科学   117篇
临床医学   110篇
内科学   493篇
皮肤病学   78篇
神经病学   172篇
特种医学   75篇
外科学   129篇
综合类   20篇
预防医学   326篇
眼科学   19篇
药学   88篇
  1篇
中国医学   8篇
肿瘤学   41篇
  2023年   12篇
  2022年   26篇
  2021年   35篇
  2020年   25篇
  2019年   35篇
  2018年   37篇
  2017年   38篇
  2016年   39篇
  2015年   50篇
  2014年   60篇
  2013年   88篇
  2012年   115篇
  2011年   113篇
  2010年   79篇
  2009年   69篇
  2008年   89篇
  2007年   109篇
  2006年   76篇
  2005年   82篇
  2004年   68篇
  2003年   51篇
  2002年   65篇
  2001年   64篇
  2000年   43篇
  1999年   51篇
  1998年   35篇
  1997年   36篇
  1996年   50篇
  1995年   30篇
  1994年   44篇
  1993年   32篇
  1992年   42篇
  1991年   41篇
  1990年   42篇
  1989年   40篇
  1988年   42篇
  1987年   26篇
  1986年   29篇
  1985年   26篇
  1984年   29篇
  1983年   24篇
  1982年   19篇
  1981年   15篇
  1980年   14篇
  1979年   16篇
  1978年   19篇
  1977年   15篇
  1974年   15篇
  1973年   11篇
  1971年   12篇
排序方式: 共有2287条查询结果,搜索用时 15 毫秒
51.
52.
In patients with Mansoni schistosomiasis, it is fundamental to evaluate the disease morbidity, which is reflected by the severity of periportal fibrosis (PPF) and parameters of portal hypertension, as analyzed by ultrasonography (US). This study aimed to evaluate the morbidity of schistosomiasis by hepatic and splenic point shear-wave elastography (pSWE) and relate this to US parameters. The PPF pattern, the diameter of the portal and splenic veins and the size of the spleen were evaluated by US. Then, liver and spleen pSWEs were assessed in 74 patients using the same equipment. As the PPF pattern progressed, the splenic pSWE values significantly increased. Significant correlations between splenic pSWE, the longitudinal and transverse lengths of the spleen and the diameters of the portal and splenic veins were observed. These findings, however, were not observed through hepatic pSWE. In conclusion, the splenic pSWE has the potential for assessing morbidity in schistosomiasis mansoni.  相似文献   
53.
In a cross-sectional study of 641 Schistosoma japonicum-infected individuals in Leyte, Philippines, who were 7-30 years old, we determined the grade of hepatic fibrosis (HF) by ultrasound and used anthropometric measurements and hemoglobin levels to assess nutritional status. Serum levels of interleukin (IL)-1, IL-6, and IL-10; tumor-necrosis factor (TNF)-alpha; soluble TNF- alpha receptor I; and C-reactive protein (CRP) were measured to examine the association between these markers of inflammation and HF grade. HF was present in 8.9% of the cohort; the majority of cases were mild (grade I), and severe (grade II or grade III) cases occurred only in male individuals. Compared with individuals without HF, those with severe HF--and, to a lesser degree, those with mild HF--had a significantly lower body-mass index (BMI) and BMI z-score, a higher prevalence of anemia, and a higher level of CRP and were more likely to produce IL-6; furthermore, those with severe HF had a significantly higher level of IL-1, compared with those either without HF or with mild HF. These findings suggest that even mild HF is associated with nutritional morbidity and underscore the importance of early recognition and treatment. In addition, our data are consistent with the hypothesis that, by systemically increasing the levels of the proinflammatory cytokines IL-1 and IL-6, HF causes undernutrition and anemia.  相似文献   
54.
A factor that augmented the phagocytosis of IgG-coated ox red blood cells by the human monocyte/macrophage line U937 was identified in cell culture supernatants from two of two patients with angiocentric peripheral T cell lymphomas, three of three patients with angiocentric immunoproliferative lesions that were not frankly malignant, and one of two patients with T lymphoblastic malignancies. The factor was not present in supernatants derived from 14 nonangiocentric peripheral T cell lymphomas of other histologic types nor in ten cases of B cell lymphoma and two cases of Hodgkin's disease. A similar factor was present in the supernatants of concanavalin A (Con A)-stimulated normal peripheral blood mononuclear cells and in the supernatants of IL-2- dependent T cell lines derived from normal peripheral blood. The factor had an apparent mol wt of greater than 50,000 daltons, was heat labile (100 degrees C for two minutes), and stable at pH 2.0. Its stimulation of phagocytosis was independent of any increase in number of Fc receptors. Thus, this factor is probably not gamma-interferon. This factor may play a pathogenetic role in the hemophagocytic syndromes associated with certain T cell malignancies and immunodeficient states.  相似文献   
55.
OBJECTIVE: To examine temporal variation in the effects of CCR5-Delta32 and CCR2-64I chemokine receptor gene polymorphisms on HIV-1 disease progression. DESIGN: Pooled analysis of individual patient data from 10 cohorts of HIV-1 seroconverters from the United States, Europe, and Australia. METHODS: We studied HIV-1 seroconverters of European (n = 1635) or African (n = 215) ancestry who had been genotyped for CCR5-Delta32 and CCR2-64I. We used Cox proportional hazards models with time-varying coefficients to determine whether the genetic protection against AIDS (1987 case definition) and death varied with time since seroconversion. RESULTS: Protection against AIDS conferred by CCR5-Delta32 held constant at a 31% (RH 0.69, 95% CI 0.54, 0.88) reduction in risk over the course of HIV-1 infection, whereas protection against death held constant at a 39% reduction in risk (RH 0.61, 95% CI 0.45, 0.88). When the period from AIDS to death was isolated, the survival benefit of CCR5-Delta32 diminished 2 years after AIDS. Protection against AIDS conferred by CCR2-64I was greatest early in the disease course. Compared with individuals without CCR5-Delta32 or CCR2-64I, individuals with one or two copies of CCR2-64I had a 58% lower risk of AIDS during the first 4 years after seroconversion (RH 0.42, 95% CI 0.23, 0.76), a 19% lower risk during the subsequent 4 years (RH 0.81, 95% CI 0.59, 1.12), and no significant protection thereafter. CONCLUSION: The protection against AIDS provided by CCR5-Delta32 is continuous during the course of infection. In contrast, the protection provided by CCR2-64I is greatest early in the course of infection.  相似文献   
56.

Objective:

to validate an instrument to measure self-confidence of nursing care in urinary retention.

Methods:

methodological research study, carried out after ethical approval. A Likert-like scale of 32 items related to nursing care in urinary retention was applied to students of the graduate nursing course. For instrument validation, analysis of the sample adequacy and main components, Varimax orthogonal rotation and internal consistency analyses were developed.

Results:

in a sample of 305 students, there was high correlation of all items with the total scale and Cronbach''s alpha of 0.949. The scale items were divided into five factors with internal consistency: Factor 1 (0.890), Factor 2 (0.874), Factor 3 (0.868), Factor 4 (0.814) and Factor 5 (0.773), respectively.

Conclusion:

the scale meets the validity requirements, demonstrating potential for use in evaluation and research.  相似文献   
57.
Population-wide variation in genomic RNA of human immunodeficiency virus type 1 (HIV-1) encompassing the V3 loop of the envelope protein was studied in serum samples of 74 newly infected individuals from three Dutch cohorts: 30 homosexual men, 32 drug users, and 12 hemophiliacs. During acute infection, HIV-1 RNA sequences present in serum are relatively homogeneous, which makes direct sequencing feasible. This offered an opportunity to study the infecting virus variants before mutations had accumulated in the new host. The sampling dates ranged from 1980 to 1991, thus spanning the entire AIDS epidemic in The Netherlands. The diversity in the sequenced region increased over time in both the homosexual and the drug-user risk groups. Furthermore, this increase was associated with an increase in antigenic variation, as witnessed by serum reactivity to a V3 peptide panel. Despite this diversification, some 1990 sequences still closely resembled the earliest 1980 sequence, making ancestral inferences problematic. No evidence was found of a change in the master sequence of the virus quasi-species over time. At the amino acid level, no risk-group-associated variation was found, but at the nucleotide level, the drug-user and homosexual/hemophiliac sequences could be distinguished on the basis of a single silent nucleotide change in the sequence encoding the tip of the V3 loop. Hemophiliac sequences could not be distinguished from those of homosexuals. In spite of the large and increasing genetic variability, all sequences were more similar to the European/American HIV consensus sequence than to that of non-Western strains.  相似文献   
58.
Do gender differences in CD4 cell counts matter?   总被引:4,自引:0,他引:4  
OBJECTIVE: To examine the effect of gender on disease progression and whether gender differences in CD4 lymphocyte counts persisted for the entire course from HIV seroconversion until (death from) AIDS. METHODS: CD4 lymphocyte counts were modelled in 221 female and 443 male seroconverters following seroconversion, backwards from AIDS and backwards from death using regression analysis for repeated measurements. RESULTS: In the period before use of highly active antiretroviral therapy (HAART), progression to AIDS and to death were marginally slower in women than in men as assessed by proportional hazards analysis. Women seroconverted for HIV, developed AIDS and died at higher CD4 cell counts than men (women: 815, 146 and 44 x 10(6) cells/l, respectively; men: 727, 49 and 22 x 10(6) cells/l, respectively), although differences were only statistically significant at AIDS onset. Declines in CD4 lymphocyte counts were not significantly affected by gender and absolute differences between men and women were stable, with exception for the trajectory close to AIDS when the decline became steeper for men than women. CONCLUSION: These gender differences in CD4 lymphocyte counts suggest a delay of initiation of therapy in women compared with men (our model predicted that women reach the threshold of starting HAART at about 12 months later than men). If this delay unfavourably influences progression, treatment guidelines should be revised so that women can benefit equally from HAART.  相似文献   
59.
OBJECTIVE: We determined pneumonia, endocarditis, hospitalizations and death rates in a group of HIV-infected and non-infected IVDU recruited at low-threshold methadone programmes in Amsterdam, The Netherlands to examine the influence of HIV infection on morbidity and non-AIDS mortality in intravenous drug users (IVDU) without AIDS. DESIGN: A prospective epidemiologic study among HIV-infected and non-infected IVDU in Amsterdam. SETTING: We analysed patients attending the Municipal Health Service of Amsterdam. PATIENTS: The patient group consisted of 197 HIV-seropositive IVDU and 193 HIV-seronegative IVDU as controls. MAIN OUTCOME MEASURES: We analysed incidence rates per person-year of bacterial pneumonia; hospitalizations and non-AIDS mortality; and relative risks for HIV-infected IVDU compared to non-infected IVDU. RESULTS: The incidence of bacterial pneumonia rose from 0.1 in 1986 to 0.29 in 1989 in HIV-infected IVDU. The overall relative risk for this group was 4.0 (95% confidence interval, 1.7-9.7) compared with non-infected controls. HIV-infected IVDU were more frequently hospitalized for bacterial pneumonia than non-infected IVDU (50 versus 13%). In contrast, non-AIDS mortality rates remained stable for both HIV-infected and non-infected IVDU. HIV seropositivity was not found to be an independent risk factor for non-AIDS mortality. CONCLUSION: We found a high and rising incidence of bacterial pneumonia among HIV-infected IVDU in Amsterdam without any consequential rise in non-AIDS mortality. This contrasts with reports from studies conducted in New York City, New York, USA, where bacterial pneumonia-related mortality has been found to increase markedly, coincident with the AIDS epidemic. Early detection of bacterial pneumonia and easy access to both inpatient and outpatient medical care may be important factors in preventing early death due to common bacterial pathogens in IVDU without AIDS.  相似文献   
60.
Human immunodeficiency virus (HIV) antigen (HIV-Ag) in polyethylene glycol (PEG) precipitates and supernatants and HIV antibodies (HIV-Ab) to core and envelope antigens were studied in serial serum samples of three HIV-Ab seroconverters and 11 HIV-Ab seropositive men with a mean follow-up time of 16.1 months. In five men not progressing beyond persistent generalized lymphadenopathy (PGL) and two progressing to AIDS, HIV-Ag was detected once in 'free' configuration before HIV-Ab seroconversion and persistently or intermittently 'complexed' thereafter; in six of these men HIV core antibodies were continuously present with a declining level in one. In two men not progressing beyond PGL and five progressing to AIDS HIV-Ag was detected 'complexed' before HIV-Ab seroconversion once and persisted predominantly in 'free' configuration thereafter, while no HIV core antibody was detected in six of these men and a declining level in one. HIV-Ag was detected in 37% (14 out of 38) of HIV core antibody seropositive samples, mostly in 'complexed' form, while HIV-Ag was detected in 86% (43 out of 50) of HIV core antibody seronegative samples, mostly in both 'complexed' and 'free' configuration. Antibodies to HIV envelope antigen were detected in all HIV-Ab seropositive samples. These results indicate that the level of HIV-Ag expression is the primary determinant of detectability of HIV core antigens as well as antibodies. Enhancement of HIV-Ag expression, in a significant number of cases associated with clinical deterioration, appears to lead to clearance of HIV core antibodies in immune complexes, while HIV envelope antibody levels remain relatively unaffected.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号