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   3245篇
  免费   139篇
  国内免费   9篇
耳鼻咽喉   37篇
儿科学   44篇
妇产科学   69篇
基础医学   429篇
口腔科学   23篇
临床医学   286篇
内科学   1024篇
皮肤病学   65篇
神经病学   254篇
特种医学   62篇
外科学   245篇
综合类   8篇
一般理论   1篇
预防医学   289篇
眼科学   38篇
药学   165篇
中国医学   3篇
肿瘤学   351篇
  2024年   16篇
  2023年   15篇
  2022年   56篇
  2021年   110篇
  2020年   62篇
  2019年   111篇
  2018年   87篇
  2017年   75篇
  2016年   61篇
  2015年   68篇
  2014年   112篇
  2013年   144篇
  2012年   243篇
  2011年   259篇
  2010年   149篇
  2009年   139篇
  2008年   212篇
  2007年   207篇
  2006年   205篇
  2005年   174篇
  2004年   178篇
  2003年   141篇
  2002年   168篇
  2001年   43篇
  2000年   27篇
  1999年   45篇
  1998年   33篇
  1997年   28篇
  1996年   35篇
  1995年   28篇
  1994年   10篇
  1993年   9篇
  1992年   30篇
  1991年   19篇
  1990年   16篇
  1989年   16篇
  1988年   15篇
  1987年   9篇
  1986年   7篇
  1985年   5篇
  1984年   5篇
  1983年   4篇
  1982年   6篇
  1981年   5篇
  1980年   2篇
  1979年   1篇
  1977年   1篇
  1975年   2篇
排序方式: 共有3393条查询结果,搜索用时 28 毫秒
41.
42.
The aim of this trial was to evaluate the effectiveness of continuous positive airway pressure (CPAP) in patients with mild sleep apnea- hypopnea syndrome (SAHS). One hundred forty-two consecutive patients with mild SAHS (apnea-hypopnea index 10-30, without severe sleepiness) were randomly assigned to receive conservative treatment (CT)-sleep hygiene and weight loss-(65 patients) or CT plus CPAP (77 patients), and 125 patients (86% males, age: 54 +/- 9 yr, BMI: 29 +/- 4 kg/m(2), AHI: 20 +/- 6, ESS: 12 +/- 4) completed the follow-up. The following outcomes were assessed at inclusion and after 3 and 6 mo of treatment: sleepiness (Epworth scale, multiple sleep latency test [MSLT]), other symptoms related to SAHS, cognitive function, and perceived health status (Functional Outcomes of Sleep Questionnaire [FOSQ], Nottingham Health profile). The relief of SAHS-related clinical symptoms was significantly greater in the CPAP group than in the CT group; the Epworth scale and FOSQ also showed more improvement in the CPAP group but did not reach significance. There were no significant differences in the other tests performed probably because the baseline values were normal. CPAP compliance was 4.8 +/- 2.2 h and treatment continuation was accepted by 62% of the patients at the end of the study. These results suggest that CPAP can be considered in treating patients with mild SAHS on the basis of an improvement in symptoms.  相似文献   
43.
The aim of this study was to examine the possible relationship between the plasma levels of leptin and tumor necrosis factor (TNF)- and the stage of hepatic fibrosis in a cohort of patients with chronic hepatitis C. Leptin and TNF levels were measured by RIA in 135 patients and in 75 age- and sex-matched controls. Liver disease was evaluated by the stage of fibrosis and the extent of inflammatory infiltrate in the liver biopsy. Leptin levels correlated with BMI values in healthy controls and in patients with chronic hepatitis C (men, r = 0.61, P = 0.0001; women, r = 0.68, P = 0.003). Leptin levels increased as hepatic fibrosis stage progressed both in male and in female patients (P < 0.001); also, TNF levels were higher in patients with an advanced stage of fibrosis (P = 0.006). In these patients, levels of leptin increased according to the progression of the stage of fibrosis; these data suggest that leptin may play a role in the regulation of hepatic fibrosis.  相似文献   
44.
BACKGROUND AND OBJECTIVES: A new test for screening the procoagulant capacity of plasma is described and evaluated. This test is based on the coagulation of plasma initiated by thromboplastin (Tp) in the presence of thrombomodulin (TM). In a previous paper we reported that this test had a significant phenotypic and genetic correlation with thrombosis susceptibility. The present report describes the characteristics of the test and its sensitivity to the concentration of some hemostasis factors. DESIGN AND METHODS: Plasma from normal subjects, from individuals with various disorders of hemostasis and plasma with different concentrations of factors II, V, VII, VIII, X, fibrinogen, protein C and protein S were studied. The thromboplastin-thrombomodulin-mediated time (Tp-TMT) is measured after mixing 100 mL of plasma diluted 1/10 at 37 C with 100 mL of a solution composed of 2 parts of thromboplastin, 1 part of thrombomodulin at 30 U/mL and 1 part of Owren's buffer. The results are expressed as the ratio of the patient's clotting time to that of the control. Values were compared with Student's t test and the Mann-Whitney test. Differences were considered statistically significant when p<0.05. RESULTS: In the control group women showed significantly lower values than men. Raised levels of factors II, V, VII and X reduced the coagulation time obtained with Tp-TM. Elevated concentrations of fibrinogen and factor VIII did not influence the test. The Tp-TMT was sensitive to protein S deficiencies, but not to protein C deficiencies. INTERPRETATION AND CONCLUSIONS: These results indicate that the effect of protein S on the test is through its anti-prothrombinase activity. In conclusion: Tp-TMT, which is correlated with thrombosis susceptibility, is sensitive to raised levels of factors II, V, VII and X, as well as to low levels of protein S, and may be an indicator of thrombosis risk.  相似文献   
45.
OBJECTIVE: The main objective of this work was to decrease the incidence of relapse after autologous stem cell transplantation with a "double purging" procedure. METHODS: We used a "positive" (CD34) and "negative" (CD19) double selection method to improve the efficacy of "single purging" of hematopoietic harvests in poor-prognosis lymphoproliferative disorders. All patients included in the study had a positive molecular marker of their disease. Minimal residual disease (MRD) was studied by flow cytometry and PCR techniques during the purging procedure and after transplantation. RESULTS: Twenty-six patients fulfilled entry criteria. Median age of patients was 50 years (range: 33-66); 17 were male and 9 female. Thirteen (50%) of the patients mobilized an adequate number of CD34+ cells (>or=3 x 10(6)/kg) to proceed with the double-selection protocol. Twelve of the 13 harvests became PCR negative after purging. Ten patients were grafted with the selected products and all but one engrafted without delay. After a median follow-up of 30 months, 2 of 10 patients suffered a molecular relapse at 7 and 19 months respectively. The earlier relapse was observed in the patient who received a MRD+ product. Only one patient experienced a clinical relapse. Three patients died due to obliterans bronchiolitis, pneumococcal sepsis, and septic shock of unknown origin, respectively, and three others presented life-threatening infections. CONCLUSION: Therefore, CD34+/CD19+ positive/negative selection is an effective purging approach in patients with chronic lymphoproliferative disorders. This favorable effect is, however, counterbalanced by the high frequency of life-threatening infections.  相似文献   
46.
The main structures involved in the circadian system in mammals are the suprachiasmatic nuclei (SCN) of the hypothalamus. The SCN contain multiple autonomous single-cell circadian oscillators that are coupled among themselves, generating a single rhythm. However, under determined circumstances, the oscillators may uncouple and generate several rhythmic patterns. Rats exposed to an artificially established 22-h light-dark cycle (T22) express two stable circadian rhythms in their motor activity that reflect the separate activities of two groups of oscillators in the morphologically well-defined ventrolateral and dorsomedial SCN subdivisions. In the experiments described in this paper, we studied the effect of melatonin and diazepam (DZP) administration in drinking water on the dissociated components of rat motor activity exposed to T22, to deduce the possible mechanism of these drugs on the circadian system. In order to suppress the endogenous circadian rhythm of melatonin, in some of the rats the pineal gland or the superior cervical ganglia were removed. The results show that melatonin or DZP treatment increased the manifestation of the light-dependent component to the detriment of the manifestation of the non-light-dependent component and that melatonin, but not DZP, shortens the period of the non-light-dependent component. These findings suggest that both DZP and melatonin favor entrainment to external light, and that melatonin could also act on the SCN, producing changes in the period of the circadian cycle.  相似文献   
47.
The main goal of this study was to assess the role of mycophenolate mofetil (MMF) during interruption of highly active antiretroviral therapy (HAART). Seventeen patients with early-stage chronic HIV type 1 infection were treated with HAART for 12 months. They were then randomized (day 0) to receive MMF (HAART-MMF group, n = 9) or to continue the regimen (HAART group, n = 6) for 120 additional days. At day 120 in the HAART-MMF group, HAART was discontinued, and MMF administration was continued. The primary end point of the study was the number of individuals maintaining a plasma viral load (VL) set point of <200 copies/mL after at least 6 months off HAART. At day 120, all patients in both groups had undetectable plasma VLs. After 6 months off HAART, 5 of 9 patients in the HAART-MMF group versus 1 of 6 patients in the HAART group maintained a plasma VL of <200 copies/mL (P = 0.28). According to the ability of their plasma to inhibit cellular proliferation, patients were reclassified and divided into an inhibition group (n = 6) and a no inhibition group (n = 9). The doubling time of VL rebound was significantly higher in the inhibition group (mean +/- SE, 10.22 +/- 1.3) than in the no inhibition group (mean +/- SE, 4.6 +/- 1.6; P = 0.03). Moreover, 5 of 6 patients in the inhibition group maintained a plasma VL of <200 copies/mL versus 1 of 9 patients in the no inhibition group (P = 0.005) after 6 months off HAART. We found that combining MMF and HAART delayed VL rebound and improved control of viral replication without HAART but only when inhibition of lymphocyte proliferation was achieved.  相似文献   
48.
OBJECTIVES: To analyze the dynamics of both HIV-1-specific CD4 and CD8 T-cell responses during structured treatment interruptions (STIs) in chronically HIV-1-infected (CHI) patients and to correlate them with the viral set point achieved. METHODS: Forty-five early-stage CHI patients who were on highly active antiretroviral therapy (HAART) for at least 1 year and underwent STI were included. Plasma viral load (VL), peripheral blood mononuclear cell (PBMC) lymphoproliferative (LPR) response to HIV p24 protein, and HIV-1 epitope-specific interferon-gammarelease from CD8 T cells were measured over a minimum study period of 2 years. RESULTS: VL set point during final STI was both significantly lower than, and positively correlated to, baseline VL (P < 0.0001: mean VL reduction 0.77 log10, and r = 0.42, P = 0.004, respectively). CD4 LPRs to p24 increased significantly (P = 0.001) between day 0 of the first STI cycle and 4th STI but decreased thereafter. VL set point during final STI was significantly and negatively correlated with LPRs to p24 at both 2nd STI and 4th STI. Nevertheless, at week 52, 12 weeks after the end of the last STI, LPRs were weak and transient in all patients and were not correlated with VL set point. Moreover, the magnitude and breadth of HIV-1-specific CD8 T-cell responses increased significantly (P < 0.0001) between day 0 and week 52. The largest increases occurred during the final STI. Even though VL reached set point by week 12 of the final STI, HIV-1-specific CD8 T-cell responses did not stabilize but rather increased until the end of the follow-up and did not correlate with plasma VL (r = 0.01, P = 0.88). CONCLUSIONS: STIs do not lead to control of viral replication in CHI patients, probably due to the fact that boosted CTL responses lack strong and durable helper T-cell responses. To reset the VL set point, new approaches that effectively augment and preserve helper T-cell responses should be investigated.  相似文献   
49.
Background: Patients with impaired left ventricular function have a high risk of developing ventricular arrhythmias and sudden death. Among different markers of risk, the prolongation and regional heterogeneity of repolarization are of increasing interest. However, there are limited data regarding feasibility of analyzing repolarization parameters and their dynamics in 24‐hour Holter ECG recordings. Methods: Dynamic behavior of repolarization parameters was studied with a new automatic algorithm in digital 24‐hour Holter recordings of 60 healthy subjects and 55 patients with idiopathic dilated cardiomyopathy (IDC). Repolarization parameters included the mean value of QT and QTc durations, QT dispersion, and peaks of QT duration and QT dispersion above prespecified thresholds. Results: In comparison to healthy subjects, patients with IDC had lower heart rate variability, longer mean QT and QTc durations, higher content of QTc peaks >500 ms, longer QT dispersion and its standard deviation, and a higher content of peaks >100 ms of QT dispersion (P < 0.01 for all comparisons). These repolarization parameters were significantly higher in IDC patients after adjustment for age, sex, and heart rate variability. The parameters of repolarization dynamics correlated with SDNN in healthy subjects but not in dilated cardiomyopathy patients. Conclusions: The automatic assessment of repolarization parameters in 24‐hour digital ECG recordings is feasible and differentiates dilated cardiomyopathy patients from healthy subjects. Patients with dilated cardiomyopathy have increased QT duration, QT dispersion, and increased variability of QT dispersion reflecting variations in T‐wave morphology, the factors which might predispose them to the development of arrhythmic events.  相似文献   
50.
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