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   3770篇
  免费   242篇
  国内免费   14篇
耳鼻咽喉   40篇
儿科学   211篇
妇产科学   111篇
基础医学   531篇
口腔科学   135篇
临床医学   317篇
内科学   739篇
皮肤病学   83篇
神经病学   496篇
特种医学   61篇
外科学   363篇
综合类   40篇
预防医学   219篇
眼科学   102篇
药学   255篇
中国医学   17篇
肿瘤学   306篇
  2024年   5篇
  2023年   50篇
  2022年   108篇
  2021年   225篇
  2020年   116篇
  2019年   138篇
  2018年   147篇
  2017年   104篇
  2016年   118篇
  2015年   131篇
  2014年   188篇
  2013年   225篇
  2012年   306篇
  2011年   297篇
  2010年   169篇
  2009年   114篇
  2008年   231篇
  2007年   213篇
  2006年   211篇
  2005年   187篇
  2004年   179篇
  2003年   152篇
  2002年   150篇
  2001年   22篇
  2000年   13篇
  1999年   26篇
  1998年   27篇
  1997年   19篇
  1996年   19篇
  1995年   18篇
  1994年   11篇
  1993年   14篇
  1992年   8篇
  1991年   7篇
  1990年   7篇
  1989年   5篇
  1988年   7篇
  1987年   6篇
  1986年   7篇
  1985年   4篇
  1984年   3篇
  1983年   6篇
  1982年   5篇
  1980年   5篇
  1979年   4篇
  1977年   3篇
  1975年   2篇
  1974年   3篇
  1966年   3篇
  1936年   2篇
排序方式: 共有4026条查询结果,搜索用时 46 毫秒
1.
2.

Background

Bone mineral density (BMD) has been found to improve after parathyroidectomy (PTX) in patients with primary hyperparathyroidism. There are few data on the effect of PTX on BMD in normocalcemic and normohormonal primary hyperparathyroidism.

Methods

A retrospective analysis of 92 primary hyperparathyroidism patients who underwent PTX between 2004 and 2012 with pre- and post-PTX dual-energy x-ray absorptiometry was performed. Within-person changes in BMD pre- and post-PTX were analyzed using log linear mixed models, stratified by biochemical status.

Results

Bone mineral density increased post-PTX in the whole cohort at the lumbar spine (+2.5%), femoral neck (+2.1%), and total hip (+1.9%) and decreased at the one-third radius (–0.9%). On comparison of BMD changes by profile, BMD increased in those with the typical profile at the lumbar spine (3.2%), femoral neck (2.9%), and total hip (2.9%) but declined at the one-third radius (–1.5%). In contrast, BMD improved only at the femoral neck (4.3%) in the normohormonal group and did not change at any site in the normocalcemic group. The typical group had a greater increase in BMD over time at the femoral neck and total hip compared with normocalcemic patients.

Conclusion

Our results indicate that the skeletal benefit of PTX was attenuated in normocalcemic and normohormonal patients, suggesting that skeletal changes after PTX may depend on biochemical profile.  相似文献   
3.
4.
OBJECTIVE: We sought to measure the incidence of pressure ulcer development at a university health center in Turkey, and to determine whether the Waterlow Pressure Sore Risk (PSR) Scale score predicted pressure ulcer development, stage, or number of ulcers. DESIGN: We prospectively evaluated patients who were hospitalized at our university-based medical center. SETTING AND SUBJECTS: We analyzed data from 22,834 patients hospitalized at the Baskent University Adana Teaching and Medical Research Center in Ankara, Turkey from January 1, 2004 to December 31, 2004, including 360 patients who developed pressure ulcers. INSTRUMENTS: The Waterlow PSR Scale was used to assess pressure ulcer risk. In addition, age, sex, the ward or unit in which the patient was hospitalized, reason for hospitalization, and location and stage of ulcers were collected on a data form designed specifically for this study. METHODS: A single nurse physiotherapist assessed all patients daily during their hospitalization. When a pressure ulcer was diagnosed by the nurse physiotherapist, a physician staged the pressure ulcers based on the US National Pressure Ulcer Advisory Panel (NPUAP) staging system. RESULTS: Three hundred sixty out of 22,834 patients developed 1 or more pressure ulcers, resulting in an incidence rate of 1.6%. Most ulcers (59.2%) occurred in patients hospitalized in the intensive care unit (n = 213). A positive correlation between the Waterlow PSR Scale score and number of ulcers per patient (r: 0.178, P < .01) was identified. No significant correlation was found linking Waterlow PSR Scale score and ulcer stage or the development of a single ulcer. CONCLUSION: We found significantly lower pressure ulcer incidence rates than those commonly reported in the literature, which we believe is principally attributable to short hospital stays and a strong emphasis on preventive nursing care. While high Waterlow PSR scale Scores correlated positively with development of multiple ulcers, this did not predict ulcer stage or the presence of a single pressure ulcer.  相似文献   
5.
6.
BACKGROUND: Quality of life has increased in popularity as an outcome measure in health research. However, the measurement of quality of life has been questioned on methodologic grounds, as it often shows little association with objective measures of disease status. OBJECTIVE: For this report we studied the determinants of pediatric asthma caregiver report of quality of life and its relationship to disease burden. METHOD: Ninety-eight children who were admitted to a Pediatric Day Program for an asthma evaluation were enrolled in an outcome study. A complete set of medical records for the 2-year period before and after the admission was collected and systematically coded for health care utilization. Using the Pediatric Asthma Caregiver's Quality of Life Questionnaire, data were collected at baseline, discharge, and year after the admission. Caregiver negative affect (anxiety and depression), measured with the Brief Symptom Inventory, was also collected at baseline and discharge. RESULTS: Caregiver report of quality of life was unrelated to health care utilization at baseline but instead was significantly related to baseline caregiver negative affect. A significant relationship between health care utilization and quality of life was present at followup. The Emotional Function scale from the quality of life measure can account for most of the relationship between quality of life and negative affect. CONCLUSIONS: Caregiver affect may have a considerable influence on report of quality of life. Understanding the individual characteristics of the respondent is important when using a quality of life instrument as an outcome measure.  相似文献   
7.
8.
A total of five Wolf-Hirschhorn syndrome (WHS) patient with a 4p16.3 de novo microdeletion was referred because of genotype-phenotype inconsistencies, first explained as phenotypic variability of the WHS. The actual deletion size was found to be about 12 Mb in three patients, 5 Mb in another one and 20 Mb in the last one, leading us to hypothesize the presence of an extrachromosome segment on the deleted 4p. A der(4)(4qter --> p16.1::8p23 --> pter) chromosome, resulting from an unbalanced de novo translocation was, in fact, detected in four patients and a der(4)(4qter --> q32::4p15.3 --> qter) in the last. Unbalanced t(4;8) translocations were maternal in origin, the rec(4p;4q) was paternal. With the purpose of verifying frequency and specificity of this phenomenon, we investigated yet another group of 20 WHS patients with de novo large deletions (n = 13) or microdeletions (n = 7) and with apparently straightforward genotype-phenotype correlations. The rearrangement was paternal in origin, and occurred as a single anomaly in 19 out of 20 patients. In the remaining patient, the deleted chromosome 4 was maternally derived and consisted of a der(4)(4qter --> 4p16.3::8p23 --> 8pter). In conclusions, we observed that 20% (5/25) of de novo WHS-associated rearrangements were maternal in origin and 80% (20/25) were paternal. All the maternally derived rearrangements were de novo unbalanced t(4;8) translocations and showed specific clinical phenotypes. Paternally derived rearrangements were usually isolated deletions. It can be inferred that a double, cryptic chromosome imbalance is an important factor for phenotypic variability in WHS. It acts either by masking the actual deletion size or by doubling a quantitative change of the genome.  相似文献   
9.
The co-segregation in one pedigree of bipolar affective disorder with Darier's disease whose gene is on chromosome 12q23-q24.1, and findings from linkage and association studies with the neighbouring gene of phospholipase A2 (PLA2) indicate that PLA2 may be considered as a candidate gene for affective disorders. All relevant genetic association studies, however, were conducted on bipolar patients. In the present study, the possible association between the PLA2 gene and unipolar affective disorder was examined on 321 unipolar patients and 604 controls (all personally interviewed), recruited from six countries (Belgium, Bulgaria, Croatia, Germany, Greece, and Italy) participating in the European Collaborative Project on Affective Disorders. After controlling for population group and gender, one of the eight alleles of the investigated marker (allele 7) was found to be more frequent among unipolar patients with more than three major depressive episodes than among controls (P<0.01); genotypic association was also observed, under the dominant model of genetic transmission (P<0.02). In addition, presence of allele 7 was correlated with a higher frequency of depressive episodes (P<0.02). These findings suggest that structural variations at the PLA2 gene or the chromosomal region around it may confer susceptibility for unipolar affective disorder.  相似文献   
10.
Investigations were carried out to study the production of factors associated with the innate immune response in the systemic and mucosal compartments in adults and children infected with Vibrio cholerae O1 and V. cholerae O139. The levels of nonspecific mediators of the innate defense system, i.e., prostaglandin E(2) (PGE(2)), leukotriene B(4) (LTB(4)), and lactoferrin (Lf), as well as myeloperoxidase (MPO), were elevated at the acute stage of the disease in stools obtained from both O1- and O139-infected adults and children. In the systemic compartment, the levels of Lf were increased after onset of disease, which in children remained elevated up to convalescence compared to the healthy controls. Increased concentrations of C-reactive protein were seen in the sera of adult cholera patients at the acute stage of infection. Elevated levels of the nitric oxide (NO*) metabolites (nitrite and nitrate [NO(2)(-) and NO(3)(-)]) were detected in plasma but not in urine. The activity of the scavenger of reactive oxygen species, superoxide dismutase, was higher in the plasma of adults immediately after the onset of disease, suggesting that an active scavenging of reactive oxygen species was taking place. The concentration of 8-iso-prostaglandin F(2 alpha) remained unchanged in the systemic and mucosal compartments in the study subjects. After the recovery of patients from cholera, the concentration of the majority of the metabolites decreased to baseline levels by day 30 after the onset of infection. Immunohistochemical staining showed increased tissue expression of MPO, Lf, and inducible nitric oxide synthase at the acute stage in the duodenal biopsies of adults and rectal biopsies obtained from children with cholera. Very little difference was seen in the levels of the different inflammatory mediators in patients infected with V. cholerae O1 or the encapsulated V. cholerae O139. In summary, these results suggest that elevated concentrations of Lf, MPO, PGE(2), LTB(4), and NO*, as well as other metabolites, during the acute stage of the disease indicate that the innate defense system, as well as the inflammatory process, is activated in both adults and pediatric patients infected with V. cholerae O1 and O139.  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