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   158767篇
  免费   10801篇
  国内免费   625篇
耳鼻咽喉   1769篇
儿科学   3905篇
妇产科学   2616篇
基础医学   20938篇
口腔科学   3389篇
临床医学   15557篇
内科学   33620篇
皮肤病学   3241篇
神经病学   14606篇
特种医学   6967篇
外国民族医学   14篇
外科学   25264篇
综合类   1958篇
一般理论   109篇
预防医学   11806篇
眼科学   3306篇
药学   10132篇
中国医学   238篇
肿瘤学   10758篇
  2023年   885篇
  2022年   1485篇
  2021年   3374篇
  2020年   2079篇
  2019年   3118篇
  2018年   3591篇
  2017年   2798篇
  2016年   3136篇
  2015年   3585篇
  2014年   5090篇
  2013年   6847篇
  2012年   10335篇
  2011年   11003篇
  2010年   6308篇
  2009年   6014篇
  2008年   9745篇
  2007年   10191篇
  2006年   10099篇
  2005年   10146篇
  2004年   9313篇
  2003年   8621篇
  2002年   8271篇
  2001年   2149篇
  2000年   1846篇
  1999年   2129篇
  1998年   1925篇
  1997年   1555篇
  1996年   1333篇
  1995年   1251篇
  1994年   1127篇
  1993年   1015篇
  1992年   1292篇
  1991年   1190篇
  1990年   1031篇
  1989年   973篇
  1988年   911篇
  1987年   884篇
  1986年   883篇
  1985年   865篇
  1984年   925篇
  1983年   796篇
  1982年   960篇
  1981年   860篇
  1980年   729篇
  1979年   657篇
  1978年   646篇
  1977年   533篇
  1976年   514篇
  1974年   511篇
  1973年   449篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Sickle cell disease (SCD), an inherited group of blood disorders, is a major public health problem worldwide. Patients experience severe anemia, increased risk of life-threatening infections, painful crisis, and chronic organ damage. Access to comprehensive care for SCD is known to improve outcomes; however, it is only reported from large urban centers serving one metropolitan area. Alabama, US, is a largely rural state with a significant number of children born each year with SCD. Prior to the development of our regional clinic network, the Children and Youth Sickle Network (CYSNSM), 50% of patients identified by newborn screening were not enrolled in comprehensive sickle cell care. The majority of non-enrolled patients lived in southern Alabama. Rural areas in this region are particularly plagued by poverty and poor access to healthcare. Life expectancy is equivalent to residents of Sri Lanka. This area has 15.7 doctors/10 000 residents compared with the statewide ratio of 41.9 doctors/10 000 residents.To improve access to care, a regional clinic network, the CYSNSM, was established in 1995. This paper reviews the impact of the CYSNSM on pediatrie SCD in Alabama over the first 5 years of implementation.Since its inception in 1995, the CYSNSM has provided care for 923 patients compared with 450 prior to the development of the clinic network. Currently, 90% of all cases identified by newborn screening are enrolled compared with 50% pre-CYSNSM. Prior to the network, the average age of patients at their first clinic visit was 21 months. In the post-CYSNSM period, the average age at first clinic visit decreased substantially to 5.3 months. Prior to the CYSNSM, patients traveled on average 90 miles to a comprehensive clinic. Post-CYSNSM, this distance has been cut in half to an average of 45 miles. A total of 70% of patients now live within 30 miles of a clinic. Most importantly, the infection death rate has decreased from 5.71 deaths/100 patient years to 1.94 deaths/100 patient years.The development, implementation, and evaluation of the CYSNSM show that comprehensive care delivery in a rural setting is feasible and improves outcomes in pediatric SCD.  相似文献   
992.
Lisa I. Iezzoni (editor) Hardback, 508 pp, August 2003, ISBN 1-56793-207-X, $76.50, AcademyHealth/HAP(http://www.ache.org/hap.cfm) Lisa Iezzoni and colleagues produced the first edition of RiskAdjustment for Measuring Health Care Outcomes nearly 10 yearsago. At that time, payers and researchers were concerned withrisk adjustment primarily as a tool for hospital payment andfor assessing hospital performance. Although the Health CareFinancing Administration had ceased issuing Medicare risk-adjustedmortality rate reports, several other hospital performance reportingprojects were then underway, such as New York State’scoronary artery bypass grafting (CABG) surgery mortality project,Pennsylvania’s hospital outcomes reporting project, andthe Cleveland Health Quality  相似文献   
993.
OBJECTIVE: To report an influenza B infection with associated myocarditis and severe skeletal myositis. DESIGN: Case report. SETTING: Cardiac intensive care unit in a university-affiliated children's hospital. PATIENT: A 4-yr-old girl. RESULTS: The patient was successfully supported with extracorporeal membrane oxygenation for profound myocardial dysfunction and a combination of plasmapheresis and continuous venovenous hemodialysis for rhabdomyolysis and acute renal failure. CONCLUSIONS: This case provides a reminder that patients presenting with viral illness or myoglobinuria accompanied by renal failure, with or without associated myocarditis, may be demonstrating symptoms of influenza B.  相似文献   
994.

Background  

Environmental exposure to lead remains a significant health problem for children. The costs of lead exposure in children are estimated to be considerably more than other childhood diseases of environmental origin. While long-term trends in blood lead levels (BLLs) among children are declining, seasonal variation persists. Cross-sectional studies have found a peak in summer months. Part of this variation may be due to increased exposure to lead paint on window sills and through increased contact with soils containing lead during the summer. The current study represents the largest published population-based study on seasonality and trends in the BLLs of children to date. In addition, the results offer a comparison of recent data on seasonality of BLLs in New York State children, to studies conducted over the past three decades.  相似文献   
995.
996.
Endometrial carcinomas are classified by their morphology into two major subtypes. Endometrioid carcinomas (type I) are generally estrogen dependent, well-differentiated, superficially invasive, and have a good outcome. Serous carcinomas (type II) are hormone independent, frequently deeply invasive and widely metastatic, and have a poor prognosis. Microarray technology and analysis allows us to determine if the global gene expression profiles of these two subtypes correlate with their morphologic phenotype. Fresh tissue from 18 endometrial carcinomas was studied: 7 well-, 2 moderately, and one poorly differentiated endometrioid, 4 serous carcinomas, and 4 high-grade mixed endometrioid-serous carcinomas. Labeled cDNA probes were synthesized (Cy5 for tumor, Cy3 for reference) and applied to microarrays containing 18,098 cDNA clones or ESTs. A pool of equal amounts of total RNA from each tumor served as the reference RNA. By unsupervised cluster analysis, the endometrioid carcinomas clustered together and were separate from the serous carcinomas. The high-grade mixed carcinomas clustered with the serous carcinomas. Using a statistical algorithm based on gene expression pattern and conducting a supervised analysis of the two defined groups, we have identified 315 genes that statistically differentiate type I from type II endometrial carcinomas. In addition to corroborating the predicted overexpression of known markers (e.g., ras and catenin in endometrioid carcinomas), the cDNA microarray technique has revealed novel alterations in gene expression relevant to cell cycle, cell adhesion, signal transduction, apoptosis, and tumor progression not previously implicated in endometrial carcinomas. For serous carcinomas, these include aldolase, desmoplakin, integrin-linked kinase, PKC, and metallopeptidase. In conclusion, the gene expression profiles of type I and type II endometrial carcinomas are different. Refinement of these profiles will permit more accurate diagnostic tumor classification and the development of prognosis assays.  相似文献   
997.
998.
The simulation of biologically realistic neural networks requires the numerical solution of very large systems of differential equations. Variables within the system can be changing at rates that vary by orders of magnitude, not only at different times of the solution, but at the same time in different parts of the network. Therefore, an efficient implementation must be able to vary the solution step size, and do so independently in different subsystems. A single processor algorithm is presented in which each neuron can be solved with its own step size by using a priority queue to integrate them in the correct order. But this leaves the problem of how communication and synchronisation between neurons should be managed when executing in parallel. The proposed solution uses an algorithm based on waveform relaxation, which allows groups of neurons on different processors to be solved independently and hence in parallel, for substantial parts of the computation. Realistic test problems were run on a distributed memory parallel computer and results show that speedups of 10 using 16 processors are achievable, and indicate that further speedups may be possible.  相似文献   
999.
The present study examined if drug suppression of active sleep (AS) in the neonate affected the development and expression of respiratory behavior. Secondly, we assessed brain neurochemistry and receptor density in specific supra-medullary brain regions to identify coincident biochemical alterations. Sprague-Dawley newborn rat pups were randomized and divided among six rat mothers (n=10/mother/group), each mother housed separately. Two untreated control (UC) groups received either no interventions or were fed milk vehicle twice daily and were handled similarly to the drug intervention animals. Pharmacological disruption of sleep was achieved by administration (2 groups of each) of either clonidine (CLO) 100 microm/kg, or scopolamine (SCO) 800 microm/kg, given orally twice daily for the first 7 days of life. On postnatal (P) days P10 and P19 of life, pups were assessed for metabolism, minute ventilation (VE), tidal volume (Vt) and frequency (f). On P21 (14 days after the end of drug exposure), pups from each condition were sacrificed and punch biopsies of the frontal cortex, hypothalamus, and hippocampus were examined for hydroxytryptophan (5-HT), and norepinepherine (NE) by HPLC. An equal number of pups were sacrificed and brains examined for muscarinic acetylcholine (mAch), alpha2-adrenergic and I1-imidazoline receptor density. RESULTS: Both CLO and SCO exposed animals had a lower V(t) and respiratory quotient than UC animals (p<0.01). CLO animals exhibited a higher f (p<0.01) and both CLO and SCO exhibited a lower V(t) (p<0.05) than the UC groups; VE was reduced in the SCO groups, compared with CLO and UC groups (p<0.01). Pattern of breathing in response to brief hypoxia exposure was altered for CLO and SCO. The normal decline in VE during sleep was not observed in CLO rats. Both drug exposures resulted in a comparable reduction in hypothalamic NE and 5-HT levels (p<0.05), while in the frontal cortex, and the hippocampus variable changes in NE and 5-HT, occurred. In CLO and SCO rats mAch receptors were increased in cortex, and reduced in hypothalamus; I1-imidazoline receptors were increased in hypothalamus and decreased in hippocampus (p<0.05 for each). In contrast, alpha2-adrenergic receptors were increased in cortex for both CLO and SCO, decreased in hypothalamus for CLO, and decreased in hippocampus for SCO (p<0.05 for each). CONCLUSIONS: these data show that drug-induced neonatal sleep suppression will alter ventilatory pattern, metabolism, and site-specific concentrations of adrenergic neurotransmitters and in receptor density, perhaps as a result of suppression of neonatal AS.  相似文献   
1000.
BACKGROUND: Children with severe neurological impairment may have significant oral motor dysfunction and are at increased risk of nutritional deficiencies, poor growth, and aspiration pneumonia. Gastrostomy tube feeding is increasingly being used for nutritional support in these children. AIM: To examine the occurrence of respiratory morbidity before and after gastrostomy feeding tube insertion in children with severe neurological disabilities. METHODS: This study was nested in a longitudinal, prospective, uncontrolled, multicentre cohort study designed to investigate the outcomes of gastrostomy tube feeding in 57 children with severe neurological disabilities. Parents completed a questionnaire prior to (visit 1) and 6 and 12 months (visits 2 and 3) following the gastrostomy, detailing number of chest infections requiring antibiotics and/or hospital admission. RESULTS: Mean number of chest infections requiring antibiotics was 1.8 on visit 1 and 0.9 on visit 3. Hospital admissions for chest infections fell significantly from 0.5 to 0.09. CONCLUSION: This study provides no evidence for an increase in respiratory morbidity following insertion of a feeding gastrostomy in children with cerebral palsy.  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