首页 | 官方网站   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   25751篇
  免费   1932篇
  国内免费   102篇
医药卫生   27785篇
  2023年   259篇
  2022年   453篇
  2021年   997篇
  2020年   514篇
  2019年   811篇
  2018年   928篇
  2017年   649篇
  2016年   666篇
  2015年   757篇
  2014年   1039篇
  2013年   1307篇
  2012年   2063篇
  2011年   2088篇
  2010年   1118篇
  2009年   968篇
  2008年   1609篇
  2007年   1601篇
  2006年   1462篇
  2005年   1415篇
  2004年   1343篇
  2003年   1249篇
  2002年   1226篇
  2001年   180篇
  2000年   141篇
  1999年   216篇
  1998年   250篇
  1997年   203篇
  1996年   161篇
  1995年   159篇
  1994年   161篇
  1993年   126篇
  1992年   114篇
  1991年   75篇
  1990年   96篇
  1989年   70篇
  1988年   72篇
  1987年   94篇
  1986年   77篇
  1985年   67篇
  1984年   94篇
  1983年   81篇
  1982年   90篇
  1981年   81篇
  1980年   84篇
  1979年   50篇
  1978年   56篇
  1977年   44篇
  1975年   39篇
  1974年   35篇
  1973年   37篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
OBJECTIVE: To evaluate the anti-tumor potential of beta-lapachone in multiple myeloma (MM) cell lines (U266, RPMI8226, and MM.1S); MM cell lines resistant to dexamethasone (MM.1R), melphalan (RPMI8226/LR5), doxorubicin (RPMI8226/DOX40), and mitoxantrone (RPMI8226/ MR20); and MM cells from patients (MM1-MM4). MATERIALS AND METHODS: Cytotoxicity of beta-lapachone was assessed by MTT and [3H]-thymidine uptake assays. Apoptosis was analyzed using propidium iodide staining, DNA fragmentation, TUNEL assay, caspase-9 colorimetric assay, and immunoblotting for caspase-3, poly (ADP-ribose) polymerase (PARP), and caspase-8 cleavage products. Paracrine growth of MM cells was assessed by [3H]-thymidine uptake in cultures of bone marrow stromal cells (BMSCs) and MM cells. Interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) secretion in the culture supernatants was measured by specific enzyme-linked immunosorbent assays (ELISAs). RESULTS: beta-lapachone showed significant cytotoxicity in MM cells (IC(50): 4-8 microM). In contrast, normal peripheral blood mononuclear cells (PBMCs) and BMSCs from MM patients were relatively resistant (IC(50): 8-16 microM). IL-6 did not protect against beta-lapachone-induced apoptosis in MM.1S cells, and dexamethasone showed additive cytotoxicity. beta-lapachone also decreased binding of MM.1S cells to BMSCs; abrogated IL-6 and VEGF secretion triggered by adhesion of BMSCs to MM.1S cells; reduced proliferation of MM.1S cells adherent to BMSCs; and decreased intracellular adhesion molecule-1 (ICAM-1) expression on MM.1S cells. Furthermore, beta-lapachone induced typical PARP cleavage, increased caspase-9 proteolytic activity, and activation of caspase-3, without activation of caspase-8 in U266 cells. CONCLUSION: These studies provide a framework for clinical evaluation of beta-lapachone to improve the outcome for patients with MM.  相似文献   
993.
The clinical findings of Takatsubo Cardiomyopathy and acute myocardial infarction can be very similar. While Takatsubo cardiomyopathy rarely leads to severe complications, acute myocardial infarction can be life threatening. Treatment of both these conditions is different and so it is imperative for clinicians to have a high index of suspicion for either. Several EKG differences between the two entities have been proposed. This article summarizes the EKG changes most likely seen in Takatsubo cardiomyopathy and compares them to those seen in Acute Myocardial infarction.  相似文献   
994.
Increasing evidence suggests that derangements of cytoskeletal proteins contribute to alterations in intracellular signaling, myocyte function, and the coupling of myocytes to the extracellular matrix during cardiac hypertrophy and failure. Data from animal studies have shown an increased density of beta-tubulin protein in the right or left ventricle subjected to pressure overload, and have demonstrated that interfering with excess polymerization of beta-tubulin improves contractility. We tested the hypothesis that beta-tubulin is increased in human left ventricular hypertrophy and end-stage heart failure. Confocal microscopy of fluorescently labeled beta-tubulin protein revealed an increased density of the beta-tubulin network in cardiomyocytes from both hypertrophied and failing human hearts as compared to cells from nonfailing hearts. Western blot analysis on total heart homogenate showed no change in beta-tubulin when data were normalized to either actin or calsequestrin, although there was a significant increase in failing human hearts when data were normalized only for a constant amount of protein per heart. The mRNA for beta-tubulin was not changed in hypertrophied hearts, but was significantly decreased in failing human hearts. Thus, similar to animal models, we have shown that the density of the microtubular network within the cardiomyocyte is increased in end-stage failing human hearts. We have also shown for the first time that beta-tubulin density is increased in cells from hypertrophied human hearts. Although the functional implications of this finding in the human heart remain to be explored, data from animal studies suggest that increased beta-tubulin protein contributes to cardiac dysfunction.  相似文献   
995.
Hepatocellular carcinoma (HCC) has a poor prognosis with limited therapeutic options. We propose that local immune responses in patients with HCC are held in check by tumor-infiltrating CD4(+)CD25(+) T-regulatory lymphocytes (T(reg) cells), which suppress the activity and proliferation of effector CD4(+) and CD8(+) T cells. The phenotype and cell cycle status of tumor-infiltrating lymphocytes (TILs) in HCC were analyzed via immunohistochemistry of sections from patients undergoing surgery for HCC and via flow cytometry of peripheral blood mononuclear cells and TILs isolated from patients with HCC. Circulating and tumor-infiltrating T-cell function and activation status were assessed via proliferation and flow cytometry. More than 96% of TILs were quiescent as measured via Mcm-2 or Ki-67 expression, while less than 10% of CD8(+) T cells expressed perforin or granzyme B. CD4(+)CD25(+) T(reg) cells comprised 8.7% (1.4-13.8) of TILs and always exceeded the proportion in distant nontumor tissue (2.4% [1.5-5.6]; P = .014). T(reg) cells isolated from HCC suppressed proliferation of autologous circulating CD4(+)CD25(-) cells and perforin expression and proliferation of autologous CD8(+) T cells. The proportion of circulating T(reg) cells in patients with HCC was similar in healthy controls (7.2% [1.2-23.3] and 9.2% [1.6-30.2], respectively), but the proportion of circulating T(reg) cells that were also transforming growth factor beta1(+) was elevated in HCC compared with controls (55.5% [8.2-73.9] and 2.0% [0-4.9], respectively; P = .003). In conclusion, TILs are compromised and contain a subpopulation of suppressive CD4(+)CD25(+)Foxp3(+) T(reg) cells. Functional deletion of tumor-infiltrating T(reg) cells could enhance tumor-specific immunotherapy.  相似文献   
996.
In a population-based study of 207 subjects with irritable bowel syndrome (IBS) or functional dyspepsia (FD) and controls (n = 100), we aimed to determine whether dimensions of abnormal illness behavior from the Abnormal Illness Behaviour Questionnaire and aspects of social learning of illness behavior from the Social Learning of Illness Behaviour scale were independent predictors of health care seeking for IBS and FD. Results showed that dimensions of abnormal illness behavior and aspects of social learning of illness behavior (encouragement, reinforcement, and modeling) did not significantly differentiate between consulters and nonconsulters with IBS and/or FD. The Disease Conviction scale (OR = 1.55; 95% CI, 1.15–2.09) of the Abnormal Illness Behaviour Questionnaire was an independent predictor of having a diagnosis of IBS and/or FD, independent of age and gender, psychiatric diagnoses, and symptom severity. We conclude that a belief in the presence of serious pathology characterizes community subjects with IBS and FD, but not health care seeking.  相似文献   
997.

Introduction

Septic shock is a major cause of morbidity and mortality throughout the world. Unfortunately, the optimal fluid management of septic shock is unknown and currently is empirical.

Methods

A retrospective analysis was performed at Barnes-Jewish Hospital (St. Louis, Missouri). Consecutive patients (n = 325) hospitalized with septic shock who had echocardiographic examinations performed within 24 hours of shock onset were enrolled.

Results

A total of 163 (50.2%) patients with septic shock died during hospitalization. Non-survivors had a significantly larger positive net fluid balance within the 24 hour window of septic shock onset (median (IQR): 4,374 ml (1,637 ml, 7,260 ml) vs. 2,959 ml (1,639.5 ml, 4,769.5 ml), P = 0.004). The greatest quartile of positive net fluid balance at 24 hours and eight days post-shock onset respectively were found to predict hospital mortality, and the greatest quartile of positive net fluid balance at eight days post-shock onset was an independent predictor of hospital mortality (adjusted odds ratio (AOR), 1.66; 95% CI, 1.39 to 1.98; P = 0.004). Survivors were significantly more likely to have mild left ventricular dysfunction as evaluated by bedside echocardiography and non-survivors had slightly elevated left ventricular ejection fraction, which was also found to be an independent predictor of outcome.

Conclusions

Our data confirms the importance of fluid balance and cardiac function as outcome predictors in patients with septic shock. A clinical trial to determine the optimal administration of intravenous fluids to patients with septic shock is needed.  相似文献   
998.

Background

Arterial carbon dioxide tension (PaCO2) affects neuronal function and cerebral blood flow. However, its association with outcome in patients admitted to intensive care unit (ICU) after cardiac arrest (CA) has not been evaluated.

Methods and results

Observational cohort study using data from the Australian New Zealand (ANZ) Intensive Care Society Adult-Patient-Database (ANZICS-APD). Outcomes analyses were adjusted for illness severity, co-morbidities, hypothermia, treatment limitations, age, year of admission, glucose, source of admission, PaO2 and propensity score.We studied 16,542 consecutive patients admitted to 125 ANZ ICUs after CA between 2000 and 2011. Using the APD-PaCO2 (obtained within 24 h of ICU admission), 3010 (18.2%) were classified into the hypo- (PaCO2 < 35 mmHg), 6705 (40.5%) into the normo- (35–45 mmHg) and 6827 (41.3%) into the hypercapnia (>45 mmHg) group. The hypocapnia group, compared with the normocapnia group, had a trend toward higher in-hospital mortality (OR 1.12 [95% CI 1.00–1.24, p = 0.04]), lower rate of discharge home (OR 0.81 [0.70–0.94, p < 0.01]) and higher likelihood of fulfilling composite adverse outcome of death and no discharge home (OR 1.23 [1.10–1.37, p < 0.001]). In contrast, the hypercapnia group had similar in-hospital mortality (OR 1.06 [0.97–1.15, p = 0.19]) but higher rate of discharge home among survivors (OR 1.16 [1.03–1.32, p = 0.01]) and similar likelihood of fulfilling the composite outcome (OR 0.97 [0.89–1.06, p = 0.52]). Cox-proportional hazards modelling supported these findings.

Conclusions

Hypo- and hypercapnia are common after ICU admission post-CA. Compared with normocapnia, hypocapnia was independently associated with worse clinical outcomes and hypercapnia a greater likelihood of discharge home among survivors.  相似文献   
999.
BACKGROUND: Recently, there have been concerns about the tolerability of long-acting (2)-agonists, including possible adverse cardiovascular effects-a particular concern in patients with chronic obstructive pulmonary disease (COPD), who are at elevated risk for cardiovascular disease. OBJECTIVE: The aim of this study was to assess the cardiac safety profile of nebulized formoterol fumarate inhalation solution. METHODS: Cardiac safety was assessed as part of a 12-week, randomized, double-blind, double-dummy, placebo- and active-controlled trial that was conducted at 38 centers across the United States. Male and female patients aged >/=40 years with COPD and without other significant disease were enrolled. After a 4- to 14-day, single-blind placebo run-in period, patients with COPD were randomly assigned to receive formoterol fumarate inhalation solution 20 microg BID via nebulizer (FFIS group), formoterol fumarate 12 microg BID via dry powder inhaler (FA group), or placebo. Cardiac effects-measured by changes in heart rate (HR) and ventricular premature beats; incidence of proarrhythmic events; change in corrected QT (QTc) interval; and incidence of maximum mean change in QTc >/=60 ms-were assessed using 24-hour Holter monitoring at baseline and 12 weeks; 12-lead electrocardiography at screening and weeks 4, 8, and 12; and patient diary cards. RESULTS: A total of 351 patients with COPD were randomized (mean age, 62.8 years; 56.1% male; mean postbronchodilator forced expiratory volume in 1 second, 1.5 L). Holter monitoring found no clinically meaningful effects of FFIS or FA treatment on mean or maximum HR, ventricular premature beats, or inci dence of arrhythmic events compared with placebo. At week 12, mean (SD) changes from baseline in mean HR were -0.6 (10.9), +0.1 (11.6), and -1.4 (9.4) bpm in the FFIS, FA, and placebo groups, respectively. The incidence of mean maximum changes in QTc >/=60 ms at any time during the 12-week treatment period were 1.6%, 1.8%, and 1.8% with FFIS, FA, and placebo, respectively. Treatment-emergent cardiac adverse events (AEs) occurred in 4.1%, 3.5%, and 4.4% of patients in the FFIS, FA, and placebo groups; withdrawals due to possible cardiac AEs occurred in 1 patient per treatment group. No deaths or serious cardiac AEs occurred during the treatment period. CONCLUSION: In this COPD population, no clinically significant cardiac effects were found with twicedaily treatment with nebulized formoterol fumarate inhalation solution.  相似文献   
1000.
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-23

京公网安备 11010802026262号