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   4136篇
  免费   247篇
  国内免费   8篇
耳鼻咽喉   25篇
儿科学   97篇
妇产科学   96篇
基础医学   827篇
口腔科学   159篇
临床医学   360篇
内科学   601篇
皮肤病学   120篇
神经病学   472篇
特种医学   151篇
外科学   723篇
综合类   24篇
一般理论   1篇
预防医学   171篇
眼科学   96篇
药学   211篇
中国医学   7篇
肿瘤学   250篇
  2021年   66篇
  2020年   51篇
  2019年   47篇
  2018年   85篇
  2017年   62篇
  2016年   81篇
  2015年   105篇
  2014年   129篇
  2013年   149篇
  2012年   244篇
  2011年   239篇
  2010年   159篇
  2009年   167篇
  2008年   225篇
  2007年   211篇
  2006年   215篇
  2005年   169篇
  2004年   202篇
  2003年   163篇
  2002年   161篇
  2001年   95篇
  2000年   116篇
  1999年   109篇
  1998年   25篇
  1997年   28篇
  1996年   27篇
  1995年   28篇
  1994年   18篇
  1993年   21篇
  1992年   56篇
  1991年   40篇
  1990年   59篇
  1989年   53篇
  1988年   42篇
  1987年   28篇
  1986年   22篇
  1985年   44篇
  1984年   26篇
  1979年   25篇
  1978年   22篇
  1977年   21篇
  1974年   26篇
  1971年   26篇
  1970年   20篇
  1885年   18篇
  1880年   32篇
  1879年   21篇
  1877年   21篇
  1876年   21篇
  1875年   18篇
排序方式: 共有4391条查询结果,搜索用时 343 毫秒
1.

Objective

Arch obstruction after the Norwood procedure is common and contributes to mortality. We determined the prevalence, associated factors, and practice variability of arch reintervention and assessed whether arch reintervention is associated with mortality.

Methods

From 2005 to 2017, 593 neonates in the Congenital Heart Surgeons' Society Critical Left Heart Obstruction cohort underwent a Norwood procedure. Median follow-up was 3.7 years. Multivariable parametric models, including a modulated renewal analysis, were performed.

Results

Of the 593 neonates, 146 (25%) underwent 218 reinterventions for arch obstruction after the Norwood procedure: catheter-based (n = 168) or surgical (n = 50) at a median age of 4.3 months (quartile 1-quartile 3, 2.6-5.7). Interdigitation of the distal aortic anastomosis was protective against arch reintervention. Development of ≥ moderate tricuspid valve regurgitation and right ventricular dysfunction at any point was associated with arch reintervention. Nonsignificant variables for arch reintervention included shunt type and preoperative aortic measurements. Surgical arch reintervention was protective against arch reintervention, but transcatheter reintervention was associated with increased reintervention. Arch reintervention was not associated with increased mortality. There was wide institutional variation in incidence of arch reintervention (range, 0-40 reinterventions per 100 years patient follow-up) and in preintervention gradient (range, 0-64 mm Hg).

Conclusions

Interdigitation of the distal aortic anastomosis during the Norwood procedure decreased the risk of arch reintervention. Surgical arch reintervention is more definitive than transcatheter. Arch reintervention after the Norwood procedure is not associated with increased mortality. Serial surveillance for arch obstruction, integrated with changes in right ventricular function and tricuspid valve regurgitation, is recommended after the Norwood procedure to improve outcomes.  相似文献   
2.
Mycophenolate mofetil (MMF) is increasingly used to prevent acute and chronic rejection following kidney transplantation and in autoimmune diseases. Here, we report on a patient after kidney transplantation, who developed an acute inflammatory syndrome characterized by fever and oligoarthritis within 1 week after increasing the MMF dosage. MMF was discontinued resulting in a complete resolution of the syndrome within 48 h. We demonstrated in vitro that the patient's phorbol myristate acetate (PMA-) and formyl Met-Leu-Phe (fMLP-) stimulated polymorphonuclear neutrophils (PMNs) developed increased oxidative burst when incubated with MMF. This report demonstrates that MMF can also induce acute inflammatory syndrome in patients following kidney transplantation and that this syndrome might be due to a paradox, pro-inflammatory reaction of PMNs.  相似文献   
3.
5-Amino-4-imidazolecarboxamide (AICA) riboside, the nucleoside corresponding to AICA ribotide (AICAR or ZMP), an intermediate of the de novo pathway of purine biosynthesis, was found to exert a dose-dependent inhibition on gluconeogenesis in isolated rat hepatocytes. Production of glucose from lactate-pyruvate mixtures was half-maximally inhibited by approximately 100 microM and completely suppressed by 500 microM AICA riboside. AICA riboside also inhibited the production of glucose from all other gluconeogenic precursors investigated, i.e., fructose, dihydroxyacetone, and L-proline. Measurements of intermediates of the glycolytic-gluconeogenic pathway showed that AICA riboside provoked elevations of triose phosphates and fructose-1,6-bisphosphate and decreases in fructose-6-phosphate and glucose-6-phosphate. The effects of AICA riboside persisted when the cells were washed 10 min after its addition but were suppressed by 5-iodotubercidin, an inhibitor of adenosine kinase. AICA riboside provoked a dose-dependent buildup of normally undetectable Z nucleotides. After 20 min of incubation with 500 microM AICA riboside, ZMP, ZTP, and ZDP reached 3, 0.3, and 0.1 mumol/g cells, respectively. Concentrations of ATP were not significantly modified by addition of up to 500 microM AICA riboside when the cells were incubated with lactate-pyruvate but decreased with fructose or dihydroxyacetone. The activity of rat liver fructose-1,6-bisphosphatase was inhibited by ZMP with an apparent Ki of 370 microM. It is concluded that AICA riboside exerts a suppressive effect on gluconeogenesis because it provokes an accumulation of ZMP, which inhibits fructose-1,6-bisphosphatase.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
4.
5.
Thymuses of rats that had been: a) gamma-irradiated [500 cGy whole-body radiation (R)], or b) thermally injured [20% BSA dorsal, scald burn (TI)], or c) combined injured [irradiation followed by burn (CI)] were studied for involution and recovery processes after sublethal treatments. The expression of surface antigens on thymic cells before and after injuries was evaluated using the monoclonal antibodies (mcAB) MRC OX4, MRC OX7, MRC OX8, W3/13 HLK, and W3/25 and flow cytometric analysis. Thymic cellularity decreased to less than 1% of normal (N), age-matched rats by 4 days after R or CI. Recovery reached 60% to 70% of N by 28 days post treatments. TI caused a biphasic thymic recovery pattern with nadirs of 40% of N on days 7 and 21. Recovery at day 28 was similar to that after R and CI. Expression of OX7, OX8, W3/13, and W3/25 antigens all reached nadirs of 40% of N by day 4 after R and CI. Recovery of antigen expression, except for W3/25, was near completion by day 7 after R and CI. Changes in antigen expression after TI were less pronounced for all mcAB tested. Decreases in labeling of thymocytes with the helper T-cell marker, W3/25, observed after TI, could not be correlated with elevated expressions of the suppressor/cytotoxic T-lymphocyte antigen, OX8. Variations in relative labeling of nonlymphoid thymic cells with OX4 (Ia-antigen) reflected the disappearance and recovery of radiosensitive lymphoid thymocytes. The similarity of results after R and CI demonstrate that the model of CI is 'radiation-dominated.' The addition of burn injury to radiation trauma had no synergistically damaging effect on the parameters studied.  相似文献   
6.
7.
There is considerable evidence that lipoprotein(a) (Lp(a)) is a strong independent risk factor for coronary heart disease. Based on their risk factor profile, Mexican Americans have an increased risk of coronary heart disease, yet Mexican Americans have coronary heart disease mortality similar to or lower than that of non-Hispanic whites. The authors therefore attempted to determine whether Mexican Americans had decreased Lp(a) concentrations relative to non-Hispanic whites in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Lp(a) concentrations (mg/dl) were significantly lower in Mexican Americans (n = 316) than in non-Hispanic whites (n = 242) (men: 10.4 vs. 16.3; women: 11.5 vs. 16.4). In addition, the proportion of persons with Lp(a) concentrations of > or = 30 mg/dl (the threshold at which increased risk of coronary heart disease is believed to occur) was significantly higher in non-Hispanic whites than in Mexican Americans (18.6% vs. 7.6%; Mantel-Haenszel odds ratio (adjusted for sex) = 2.79). Age, obesity, body fat distribution, cigarette smoking, alcohol consumption, and glucose and insulin concentrations were not significantly related to Lp(a) levels. Decreased Lp(a) concentrations may account in part for Mexican Americans' relative protection from coronary heart disease mortality.  相似文献   
8.
Long lasting occupational exposure to asbestos dust may cause skin corns, benign pleural effusion, hyaline plaques of the parietal pleura, diffuse thickening of the pulmonary pleura, and asbestosis, i.e. diffuse interstitial pulmonary fibrosis. Malignant disorders include lung cancer and mesothelioma of the pleura, peritoneum and pericardium. In general, many years elapse from first exposure to the appearance of symptoms. Almost all these diseases are the result of dusty working conditions more than 20 years ago. In spite of the fact that the general public is invariably exposed to small amounts of the material, asbestos is not a public health problem. Even living in a building containing sprayed asbestos is calculated to produce a lifetime risk of death which is negligible. There is no evidence to indicate that ingested asbestos fibres represent a major health problem.  相似文献   
9.
Our purpose was to explain the reasons for sex differentials in the awareness, treatment, and control of hypertension by identifying major social and behavioral predictors of these three sequential stages of high blood pressure control. We analyzed data on all 1,433 hypertensive subjects from the First Connecticut Blood Pressure Survey. Hypertensive women were more likely than hypertensive men to be aware of their high blood pressure (odds ratio = 1.40; confidence interval = 1.10-1.79) and to have controlled levels of blood pressure (odds ratio = 1.62; confidence interval = 1.08-2.44). Men and women who were aware of their hypertension were equally likely to be treated. Sex still explained differences in awareness and control of hypertension after adjusting for other significant variables. We conclude that sex is an important predictive covariate for adjustment in explaining differences in awareness and control of high blood pressure. Health care professionals should be aware of the differential role of sex when informing and treating hypertensive patients.  相似文献   
10.
Individual skull model fabrication was introduced into preoperative diagnostics in maxillofacial surgery in the mid-1980s. The aim of the present study was to collect information on the reproducibility of a skull model milled from hardened polyurethane foam. This model was based on the CT data of a real skull. Twenty comparative studies were carried out on both the model and the original skull, the model showing an average inaccuracy of 1.6 mm. The deviations ranged between 0.0 and 3.6 mm; the general trend favouring enlargements. The total deviation of the model as compared to the original skull was 1.8%. A convincing aspect of the model, which cannot be obtained by any other method, is its plasticity and the possibility of 3 D orientation on a lifesize model. This new method is already used in preoperative planning of corrections of post-traumatic defects and craniofacial deformities as well as in tumour surgery. Correspondence to: P. Solar  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