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   2445773篇
  免费   185447篇
  国内免费   7946篇
耳鼻咽喉   33462篇
儿科学   80270篇
妇产科学   68454篇
基础医学   344779篇
口腔科学   69564篇
临床医学   213392篇
内科学   492203篇
皮肤病学   56631篇
神经病学   196780篇
特种医学   96429篇
外国民族医学   618篇
外科学   376233篇
综合类   53011篇
现状与发展   3篇
一般理论   711篇
预防医学   192326篇
眼科学   54687篇
药学   178489篇
  42篇
中国医学   4682篇
肿瘤学   126400篇
  2018年   26586篇
  2016年   22784篇
  2015年   25689篇
  2014年   35217篇
  2013年   53325篇
  2012年   70427篇
  2011年   75491篇
  2010年   45378篇
  2009年   42656篇
  2008年   70522篇
  2007年   75843篇
  2006年   76801篇
  2005年   74886篇
  2004年   71356篇
  2003年   69238篇
  2002年   66801篇
  2001年   110391篇
  2000年   113981篇
  1999年   95760篇
  1998年   28169篇
  1997年   25217篇
  1996年   26039篇
  1995年   25483篇
  1994年   24014篇
  1993年   22360篇
  1992年   78235篇
  1991年   76509篇
  1990年   74470篇
  1989年   71317篇
  1988年   66454篇
  1987年   65152篇
  1986年   62012篇
  1985年   59424篇
  1984年   44983篇
  1983年   38427篇
  1982年   23670篇
  1981年   21149篇
  1980年   19843篇
  1979年   41700篇
  1978年   29821篇
  1977年   25435篇
  1976年   23700篇
  1975年   25530篇
  1974年   30056篇
  1973年   28874篇
  1972年   27043篇
  1971年   25085篇
  1970年   23133篇
  1969年   22082篇
  1968年   20745篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Objectives:To assess low dose altepase outcome and safety in comparison with a standard-dose regimen for acute ischemic stroke treatment in Egyptian patients.Materials:An observational prospective cohort non-randomized single blinded study was carried out during the period from November 2017 to December 2018. Eighty Egyptian acute ischemic stroke patients, all eligible for intravenous alteplase, were subdivided into 2 groups (40 patients in each group). Patients were thrombolysed at a dose of 0.6 mg/kg in the first group and 0.9 mg/kg in the second group. Both groups were compared in regard to safety and outcome. Safety was expressed by the rate of symptomatic intracranial hemorrhage (SICH) and 3 months mortality, while outcome was expressed by favorable outcomes at three months (modified Rankin Scale [mRS] of 0 to 2).Results:In the first group, 69.2% (n=27) achieved favorable outcomes at 90 days compared with 64.1% (n=25) in the second group (p=0.631). Ninety-day mortality was 5% (n=2) in the first group versus 2.5% (n=1) in the second group (p=0.556). Symptomatic intracranial hemorrhage was noted in 3 patients in the second group and zero patients in the first group (p=0.077).Conclusion:Low-dose alteplase could be a practical alternative for Egyptian populations with acute ischemic stroke especially in 3 to 4.5 hours window.

Cerebrovascular stroke is the second death and the seventh disability leading cause worldwide.1 Tissue-type plasminogen activator (tPA) alteplase was the first medication approved by the Food and Drug Administration (FDA) for the acute ischemic stroke (AIS) treatment on June 1996, within 3 hours of stroke onset with a recommended dose of 0.9 mg/kg (maximum 90mg).2 In 2008, the safety of using alteplase within 3 to 4.5 hours of stroke onset was approved by the Safe Implementation of Treatments in Stroke International Stroke Thrombolysis Registry (SITS -ISTR)3 and the European Cooperative Acute Stroke Study (ECASS III).4 However, thrombolytic therapy use has not been widely adopted, especially in developing countries. The restricted time window (3 to 4.5 hours), intracerebral hemorrhage (ICH) risk and the drug high cost are major obstacles preventing its broad application.5 Coagulation and fibrinolysis responses differ among different races, which increase symptomatic intracerebral hemorrhage (SICH) risk with standard-dose alteplase6 in Asian populations, many Asian neurologists considered alteplase low dose to be a better alternative for ischemic stroke treatment. Many studies had been conducted in order to prove the efficacy and safety of Alteplase low dose.7-9 One of these studies was the Japan Alteplase Clinical Trial (J-ACT) conducted by Yamaguchi et al10 According to this study, using a 0.6 mg/kg dose of intravenous recombinant tissue plasminogen activator (rtPA) in Japanese patients was safe and effective. Despite the relatively stroke high rate among Egyptian populations, 963/100,000 inhabitants, only less than 1% of stroke patients receive intravenous thrombolysis. A major reason for this is the drug cost.11,12 Low-dose regimens (0.6 mg/kg) use will lower the economic burden of thrombolytic therapy in the community and will greatly promote the implementation of this therapy in Egypt. Our study aim was to assess the outcome and safety of alteplase low dose in comparison to the standard-dose regimen in AIS treatment in Egypt.  相似文献   
23.
Background The impact of various breast-cancer treatments on patients with a BRCA2 mutation has not been studied. We sought to estimate the impact of bilateral oophorectomy and other treatments on breast cancer-specific survival among patients with a germline BRCA2 mutation.Methods We identified 664 women with stage I–III breast cancer and a BRCA2 mutation by combining five different datasets (retrospective and prospective). Subjects were followed for 7.2 years from diagnosis to death from breast cancer. Tumour characteristics and cancer treatments were patient-reported and derived from medical records. Predictors of survival were determined using Cox proportional hazard models, adjusted for other treatments and for prognostic features.Results The 10-year breast-cancer survival for ER-positive patients was 78.9% and for ER-negative patients was 82.3% (adjusted HR = 1.23 (95% CI, 0.62–2.45, p = 0.55)). The 10-year breast-cancer survival for women who had a bilateral oophorectomy was 89.1% and for women who did not have an oophorectomy was 59.0% (adjusted HR = 0.45; 95% CI, 0.28–0.72, p = 0.001). The adjusted hazard ratio for chemotherapy was 0.83 (95% CI, 0.65–1.53: p = 0.56).Conclusions For women with breast cancer and a germline BRCA2 mutation, positive ER status does not predict superior survival. Oophorectomy is associated with a reduced risk of death from breast cancer and should be considered in the treatment plan.Subject terms: Targeted therapies, Breast cancer  相似文献   
24.
25.
AimsSelf-expanding metal stents provide rapid improvement of dysphagia in oesophageal cancer but are associated with complications. The aim of the present study was to test the effectiveness of an alternative treatment of combining biodegradable stents with radiotherapy.Materials and methodsA Simon two-stage single-arm prospective phase II trial design was used to determine the efficacy of biodegradable stents plus radiotherapy in patients with dysphagia caused by oesophagus cancer who were unsuitable for radical treatment. Fourteen patients were recruited and data from 12 were included in the final analyses.ResultsFive of 12 patients met the primary end point: one stent-related patient death; four further interventions for dysphagia within 16 weeks of stenting (41.7%, 95% confidence interval 15.2–72.3%). The median time to a 10-point deterioration of quality of life was 2.7 weeks. Nine patients died within 52 weeks of registration. The median time to death from any cause was 15.0 weeks (95% confidence interval 9.6–not reached).ConclusionThe high re-intervention observed, which met the pre-defined early stopping criteria, meant that the suggested alternative treatment was not sufficiently effective to be considered for a larger scale trial design. Further work is needed to define the place of biodegradable stents in the management of malignant oesophageal strictures.  相似文献   
26.

Objective

To compare perioperative and long-term outcomes in patients undergoing hemiarch and aggressive arch replacement for acute type A aortic dissection (ATAAD).

Methods

From 1996 to 2017, we compared outcomes of hemiarch (n = 322) versus aggressive arch replacements (zones 2 and 3 arch replacement with implantation of 2-4 arch branches, n = 150) in ATAAD. Indications for aggressive arch were arch aneurysm >4 cm or intimal tear in the aortic arch that was not resectable by hemiarch replacement, or dissection of arch branches with malperfusion.

Results

Patients in the aggressive arch group were significantly younger (mean age: 57 vs 61 years old) and had significantly longer hypothermic circulatory arrest, cardiopulmonary bypass, and aortic crossclamp times. There were no significant differences in perioperative outcomes between hemiarch and aggressive arch groups, including 30-day mortality (5.3% vs 7.3%, P = .38) and postoperative stroke rate (7% vs 7%, P = .96). Over 15 years, Kaplan–Meier survival was similar between hemiarch and aggressive arch groups (log-rank P = .55, 10-year survival 70% vs 72%). Given death as a competing factor, incidence rates of reoperation over 15 years (2.1% vs 2.0% per year, P = 1) and 10-year cumulative incidence of reoperation (14% vs 12%, P = .89) for arch and distal aorta pathology were similar between the 2 groups.

Conclusions

Both hemiarch and aggressive arch replacement are appropriate approaches for select patients with ATAAD. Aggressive arch replacement should be considered for an arch aneurysm >4 cm or an intimal tear at the arch unable to be resected by hemiarch replacement, or dissection of the arch branches with malperfusion.  相似文献   
27.

Context

Demoralization is a state of existential distress in patients with advanced illness, typically with coping difficulties, feelings of loss of sense, and purpose in life and despair, among other things. The New Demoralization Scale (DS-II) is an evaluation tool for this syndrome, which has recently been reformulated on a shorter scale.

Objectives

The objective of this study was to obtain a Spanish version of the DS-II and to assess its psychometric properties in advanced cancer patients in Spain and a number of Latin American countries.

Methods

Following a translation–back translation process, a validation study and a confirmatory analysis using structural equation models with their corresponding latent constructs were undertaken. Patients completed the DS-II in Spanish (DS-II (es)), the Hospital Anxiety and Depression Scale, and the Edmonton Symptom Assessment System–revised. Reliability was studied according to internal consistency; construct validity and concurrent validity with the Hospital Anxiety and Depression Scale and the Edmonton Symptom Assessment System–revised; discriminant validity using the Karnofsky Performance Status scale; and feasibility, with response ratio and required time. Cutoff points were established, and sensitivity and specificity were studied.

Results

The DS-II (es) was obtained. One hundred fifty patients completed the validation study. The confirmatory analysis showed coherence, and all items correlated positively with their subscales and with the overall scale. Cronbach's alpha for the DS-II (es) was 0.88, for the sense and purpose subscale 0.83, and for the coping ability 0.79. Demoralization correlated significantly with emotional distress (rho = 0.73, P < 0.001). The tool distinguished between patients with diverse functional levels (rho = ?0.319, P = 0.001). Cutoff points at 10 and 20 out of 32 were established. The scale showed high sensitivity (81.97%) and specificity (80.90%). The prevalence of demoralization was 33% in our sample.

Conclusion

The Spanish version of the new Kissane DS-II demoralization scale has shown to be valid, reliable, and feasible with adequate psychometric properties.  相似文献   
28.

Context

Quality of life (QoL) is increasingly recognized as an important outcome of cancer treatment. Previous studies have examined clinical predictors of QoL, but with the increasing prevalence of wearable sensors that monitor sleep and activity patterns, further investigation into whether these behaviors are predictive of post-treatment QoL is now feasible. Among patients receiving aggressive cancer treatment such as hematopoietic cell transplantation (HCT), analysis of circadian rhythms (24-hour patterns of sleep and activity) via wearable sensors is limited.

Objective

To evaluate the relationship between overall QoL and circadian rhythms in patients receiving allogeneic HCT.

Methods

Patients wore an ActiGraph GT3X (Pensacola, FL) activity monitor for at least 72 hours before the initiation of conditioning chemotherapy and transplantation and completed a QoL (Functional Assessment of Cancer Therapy-General [FACT-G]) assessment. QoL assessments were also completed 1, 3, and 6 months after HCT.

Results

Patients (n = 45, M age = 55) were mostly male (66%) with a total FACT-G score of 80.96 (SD = 16.05) before HCT. Mixed models revealed robust cross-sectional associations between overall QoL and multiple circadian rhythmicity parameters, including durations of high physical activity, overall circadian rhythmicity, and earlier starts of daily activity (P's < .01). Recovery of QoL after transplant was predicted by longer pre-transplant durations of high physical activity (P = .04) and earlier evening retirement (P = .04).

Conclusion

Our findings suggest that wearable sensor information is a promising method of predicting recovery of QoL after HCT. Additional studies are needed to confirm these findings in a larger sample.  相似文献   
29.

Background

Pulmonary hypertension (PH) is a comorbidity associated with interstitial lung disease (ILD). The purpose of this study was to evaluate the influence of PH on intrahospital mortality in lung transplantation (LT) for ILD.

Methods

We conducted a retrospective cohort study of 66 patients who underwent LT for ILD at the 12 de Octubre University Hospital (Madrid, Spain) from October 2008 to June 2014. PH was defined as mean pulmonary arterial pressure (mPAP) ≥25 mmHg on right-sided heart catheterization and intrahospital mortality as any death taken place after the transplantation of patients not being discharged.

Results

We retrospectively analyzed data of 66 patients; they were stratified by the presence or absence of PH before LT. Twenty-seven patients (41%) had PH. The PH group had a lower diffusing capacity of carbon monoxide (DLCO), carbon monoxide transfer coefficient (KCO), and 6-minute walk distance test (6MWT) and a higher total lung capacity (TLC), modified medical research council dyspnea scale (mMRC), and lung allocation score (LAS) than the non-PH group. Patients with PH more often underwent double lung transplantation (DLT; 59%) than single lung transplantation (SLT).Intrahospital mortality was 13% (9/66). No significant differences were observed in Kaplan-Meier survival curves for the PH and non-PH groups with a median survival time of 46 days versus 33 days (IQR 26–74; log-rank P = .056); however, the postoperative length of stay in the hospital was greater in the PH group.

Conclusions

In our cohort, pulmonary hypertension was not related to early mortality in lung transplantation recipients for interstitial lung diseases.  相似文献   
30.

Background and purpose

The vein of Galen aneurysmal malformation (VGAM) is a rare congenital vascular malformation with a higher morbidity and mortality, especially in neonates. Ultrasound, CT and MR are usually used in diagnosis and treatment monitoring of these disorders. In this current study, we aim to examine utility of SWI in evaluation of treatment response in infants with VGAM.

Materials and methods

We performed a retrospective chart analysis of children with VGAM in our institution between January 2008 and December 2016. Inclusion criteria included; confirmed VGAM on DSA; available SWI sequence at baseline and at follow up after at least a single embolization session; age at initial MR of 18?years or younger. Signal intensity and Angioarchitecture of VGAM and cerebral veins on SWI, as well as hydrocephalus and clinical outcome were evaluated.

Results

Of 11 patients identified with VGAM in our institution, 5 children (3 males and 2 females) satisfied the inclusion criteria. The average age at initial MR was 29?days (range 1–120). Fourteen MRI were available for review. All children had VGAM of mural type. Intramedullary veins were dilated and SWI-hypointense in all children, while subependymal and sulcal veins were dilated and SWI-hypointense in 4 patients on initial MRI. On the first available follow up MRI, cerebral veins have mostly normalized in 4 children and remained mostly dilated and SWI-hypointense in 1 child; even after complete treatment of the VGAM.

Conclusion

Our preliminary findings show that SWI seems to offer a beneficial non-invasive tool in evaluating passive venous congestion patterns in pediatric patients with VGAM. It remains to be determined in larger studies, the clinical significance of these SWI changes.  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