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   40448篇
  免费   2512篇
  国内免费   266篇
耳鼻咽喉   476篇
儿科学   1199篇
妇产科学   1205篇
基础医学   4292篇
口腔科学   1150篇
临床医学   3339篇
内科学   8482篇
皮肤病学   845篇
神经病学   1922篇
特种医学   1402篇
外国民族医学   18篇
外科学   7109篇
综合类   1002篇
现状与发展   2篇
一般理论   31篇
预防医学   3128篇
眼科学   1187篇
药学   3650篇
中国医学   281篇
肿瘤学   2506篇
  2023年   520篇
  2022年   1541篇
  2021年   2275篇
  2020年   1203篇
  2019年   1542篇
  2018年   2042篇
  2017年   1258篇
  2016年   1275篇
  2015年   1403篇
  2014年   1835篇
  2013年   2211篇
  2012年   3163篇
  2011年   3310篇
  2010年   1794篇
  2009年   1395篇
  2008年   2009篇
  2007年   2115篇
  2006年   1896篇
  2005年   1724篇
  2004年   1553篇
  2003年   1379篇
  2002年   1264篇
  2001年   461篇
  2000年   424篇
  1999年   381篇
  1998年   227篇
  1997年   186篇
  1996年   169篇
  1995年   164篇
  1994年   126篇
  1993年   103篇
  1992年   177篇
  1991年   174篇
  1990年   168篇
  1989年   146篇
  1988年   142篇
  1987年   136篇
  1986年   135篇
  1985年   121篇
  1984年   107篇
  1983年   119篇
  1982年   68篇
  1981年   67篇
  1980年   51篇
  1979年   87篇
  1978年   59篇
  1977年   64篇
  1976年   58篇
  1975年   52篇
  1974年   50篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
961.
AIM: To determine the prevalence of bipolar disorder (BD) and sub-threshold symptoms in children with attention deficit hyperactivity disorder (ADHD) through 14 years’ follow-up, when participants were between 21-24 years old.METHODS: First, we examined rates of BD type I and II diagnoses in youth participating in the NIMH-funded Multimodal Treatment Study of ADHD (MTA). We used the diagnostic interview schedule for children (DISC), administered to both parents (DISC-P) and youth (DISCY). We compared the MTA study subjects with ADHD (n = 579) to a local normative comparison group (LNCG, n = 289) at 4 different assessment points: 6, 8, 12, and 14 years of follow-ups. To evaluate the bipolar variants, we compared total symptom counts (TSC) of DSM manic and hypomanic symptoms that were generated by DISC in ADHD and LNCG subjects. Then we sub-divided the TSC into pathognomonic manic (PM) and non-specific manic (NSM) symptoms. We compared the PM and NSM in ADHD and LNCG at each assessment point and over time. We also evaluated the irritability as category A2 manic symptom in both groups and over time. Finally, we studied the irritability symptom in correlation with PM and NSM in ADHD and LNCG subjects.RESULTS: DISC-generated BD diagnosis did not differ significantly in rates between ADHD (1.89%) and LNCG 1.38%). Interestingly, no participant met BD diagnosis more than once in the 4 assessment points in 14 years. However, on the symptom level, ADHD subjects reported significantly higher mean TSC scores: ADHD 3.0; LNCG 1.7; P < 0.001. ADHD status was associated with higher mean NSM: ADHD 2.0 vs LNCG 1.1; P < 0.0001. Also, ADHD subjects had higher PM symptoms than LNCG, with PM means over all time points of 1.3 ADHD; 0.9 LNCG; P = 0.0001. Examining both NSM and PM, ADHD status associated with greater NSM than PM. However, Over 14 years, the NSM symptoms declined and changed to PM over time (df 3, 2523; F = 20.1; P < 0.0001). Finally, Irritability (BD DSM criterion-A2) rates were significantly higher in ADHD than LNCG (χ2 = 122.2, P < 0.0001), but irritability was associated more strongly with NSM than PM (df 3, 2538; F = 43.2; P < 0.0001).CONCLUSION: Individuals with ADHD do not appear to be at significantly greater risk for developing BD, but do show higher rates of BD symptoms, especially NSM. The greater linkage of irritability to NSM than to PM suggests caution when making BD diagnoses based on irritability alone as one of 2 (A-level) symptoms for BD diagnosis, particularly in view of its frequent presentation with other psychopathologies.  相似文献   
962.
963.
964.
AIM: To determine the long-term prevalence of Helicobacter pylori (H pylori) gastritis in patients after partial gastric resection due to peptic ulcer, and to compare the severity of H pylori-positive gastritis in the corpus mucosa between partial gastrectomy patients and matched controls. METHODS: Endoscopic biopsies were obtained from 57 patients after partial gastric resection for histological examination using hematoxylin/eosin and Warthin-Starry staining. Gastritis was graded according to the updated Sydney system. Severity of corpus gastritis was compared between H pylori-positive partial gastrectomy patients and H pylori-positive duodenal ulcer patients matched for age and gender. RESULTS: In partial gastrectomy patients, surgery was performed 20 years (median) prior to evaluation. In 25 patients (43.8%) H pylori was detected histologically in the gastric remnant. Gastric atrophy was more common in H pylori-positive compared to H pylori-negative partial gastrectomy patients (P<0.05). The severity of corpus gastritis was significantly lower in H pylori-positive partial gastrectomy patients compared to duodenal ulcer patients (P<0.01). There were no significant differences in the activity of gastritis, atrophy and intestinal metaplasia between the two groups. CONCLUSION: The long-term prevalence of H pylori gastritis in the gastric corpus of patients who underwent partial gastric resection due to peptic ulcer disease is comparable to the general population. The expression of H pylori gastritis in the gastric remnant does not resemble the gastric cancer phenotype.  相似文献   
965.
BACKGROUND: Antibiotics can potentiate warfarin anticoagulation. While preemptive warfarin dose reduction (DR) upon initiation of antibiotics has been advocated by experts, there are no published data regarding the efficacy of this strategy vs. the conventional strategy of not changing warfarin dose and carefully following international normalized ratio (INR) results. METHODS AND RESULTS: We compared the efficacy of preemptive 10-20% DR vs. no change in warfarin dosing in 40 chronically anticoagulated patients initiating trimethoprim-sulfamethoxazole (TMP-SMX) or levofloxacin. Eighteen patients received preemptive warfarin DR and 22 control patients underwent no change in warfarin dosing. There was no difference between the DR and control groups in the mean INR before beginning antibiotic therapy (2.53 +/- 0.12 vs. 2.52 +/- 0.11; P > 0.9). Mean interval between initiation of antibiotic and next INR was 5.1 +/- 0.4 vs. 4.7 +/- 0.5 days for DR vs. control patients, respectively (P > 0.5). For both TMP-SMX and levofloxacin, patients managed with a preemptive warfarin DR strategy did not exhibit a statistically significant change in the INR after initiating antibiotic therapy. In contrast, for each antibiotic, control group patients exhibited a significant increase in mean post-antibiotic INR compared to mean pre-antibiotic INR, though the effect was more pronounced in patients treated with TMP-SMX than with levofloxacin. Of DR group patients who were treated with TMP-SMX, none (0/8) developed a subtherapeutic INR, while 40% (4/10) of levofloxacin-treated patients developed a sub-therapeutic INR. Supra-therapeutic INR results led to transient interruption of warfarin dosing in 2 patients (11%) in the DR group vs. 12 patients (55%) in the control group (P = 0.007). CONCLUSIONS: Prophylactic warfarin DR of 10-20% is effective in maintaining therapeutic anticoagulation in patients initiating TMP-SMX. An expectant strategy consisting of no change in warfarin dosing with short-term INR follow-up appears reasonable in patients treated with levofloxacin.  相似文献   
966.
Hematologic adverse events, including anemia, neutropenia, and thrombocytopenia, occur frequently during the course of antiviral therapy with pegylated interferon and ribavirin in patients with chronic hepatitis C. Dose reduction of antiviral therapy to manage these adverse events may result in decreased rates of sustained virologic response. Other management options include the use of growth factors and the development of new therapies with less hematologic toxicity.  相似文献   
967.

Background:

Non-surgical reduction remains the first line treatment of choice for intussusception. The major complication of air enema reduction is bowel perforation. The authors developed a custom made pressure release valve to be added to portable insufflation devices, delivering air at pressures accepted as safe for effective reduction of intussusception in children under fluoroscopic guidance. The aim of this study was to develop a custom made pressure release valve that is suitable for the insufflation devices used for air enema reduction of intussusception and to put this valve into regular clinical practice.

Materials and Methods:

An adjustable, custom made pressure release valve was assembled by the authors using readily available components. The valve was coupled to a simple air enema insufflation device. The device was used for the trial of reduction of intussusception in a prospective study that included 132 patients.

Results:

The success rate for air enema reduction with the new device was 88.2%. The mean pressure required to achieve complete reduction was 100 mmHg. The insufflation pressure never exceeded the preset value (120 mmHg). Of the successful cases, 58.3% were reduced from the first attempt while 36.1% required a second insufflation. Only 5.55% required a third insufflation to complete the reduction. In cases with unsuccessful pneumatic reduction attempt (18.1%), surgical treatment was required. Surgery ranged from simple reduction to resection with a primary end to end anastomosis. No complications from air enema were recorded.

Conclusions:

The authors recommend adding pressure release valves to ensure safety by avoiding pressure overshoot during the procedure.Key words: Air enema, intussusception, pneumatic, pressure release, reduction, safety, valve  相似文献   
968.

Background and study aims

Central nervous system (CNS) involvement in hepatitis C virus (HCV) infection has different facets such as anxiety, depression, cognitive impairment and vasculitis. We were interested in detecting subclinical CNS involvement in chronic HCV infected subjects with and without systemic vasculitis.

Patients and methods

Nineteen patients (15 females and 4 males) with chronic HCV infection (mean age 46.5?±?7 and mean duration since diagnosis of HCV infection 4.7?±?4?years, including 6 (32%) Child-Pugh class A cirrhotic patients) and 30 age, sex and education matched healthy control subjects were studied. Thirteen patients had associated vasculitis. Patients and control subjects were assessed using the block design and comprehension subtests of Wechsler Bellevue Adult Intelligence Scale, Wechsler Memory scale (WMS), Beck Anxiety Inventory (BAI) and Beck Depression Inventory (BDI). Brain HMPAO Single Photon Emission Computed Tomography (SPECT) was performed for HCV patients.

Results

Patients with HCV had lower scores on the block design test compared to control subjects (8.37?±?1.89 versus 10.37?±?1.47, p?<?0.001), lower total WMS scores (43.15?±?10.49 versus 60.27?±?8.08, p?<?0.001) and higher anxiety and depression scores (16.94?±?10.46 and 37.17?±?10.38 versus 10.3?±?4.67 and 28.9?±?5.99, p?=?0.004 and 0.001, respectively). Total WMS were lower in HCV patients with vasculitis compared to those without vasculitis (39.14?±?9.3 versus 51.17?±?8.3, p?=?0.019) while the block design and comprehension tests, BAI and BDI were not significantly different between both groups. The block design and comprehension tests, WMS, BAI and BDI were not significantly different between cirrhotic and non-cirrhotic patients. Seven patients had different patterns of cerebral hypoperfusion on SPECT, and all of them had associated vasculitis. Abnormal SPECT was associated with lower total WMS scores (35.87?±?10.8 versus 46.79?±?8.6 in those with normal SPECT, p?=?0.049).

Conclusions

Vasculitis may contribute to the development of neuropsychiatric involvement in HCV patients.  相似文献   
969.

OBJECTIVES:

To estimate the prevalence of urinary tract infection in infants and children with bronchiolitis.

METHODS:

A retrospective cross-sectional study involving patients zero to 24 months of age who were hospitalized with acute bronchiolitis was conducted.

RESULTS:

A total of 835 paediatric patients with acute bronchiolitis were admitted to the paediatric ward between January 2010 and December 2012. The mean (± SD) age at diagnosis was 3.47±2.99 months. There were 325 (39%) girls and 510 (61%) boys. For the purpose of data analysis, the patient population was divided into three groups: group 1 included children hospitalized with respiratory syncytial virus (RSV) bronchiolitis; group 2 included children hospitalized with clinical bronchiolitis with no virus detected; and group 3 included children hospitalized with clinical bronchiolitis due to a respiratory virus other than RSV. Results revealed that urinary tract infection was present in 10% of patients, and was most common in group 3 (13.4%) followed by group 2 (9.7%), and was least common in group 1 (6%) (P=0.030).

CONCLUSIONS:

The possibility of a urinary tract infection should be considered in a febrile child with a diagnosis of bronchiolitis, particularly if the trigger is a respiratory virus other than RSV.  相似文献   
970.
A human 70-kDa heat shock protein (hsp70) gene segment has been isolated. The segment contains 3.15 kilobase pairs (kbp) of 5' nontranscribed sequence, an RNA leader of 119 bp, and a protein-coding region of 741 bp. The human protein sequence shows a high degree of homology to hsp70 sequences from other species. Expression experiments in Xenopus oocytes and mammalian cells indicate that a region that includes only 105 bp of 5' nontranscribed sequence contains all elements required for the efficient heat-controlled expression of the human gene. Two adjacent identical sequence elements, which are partly homologous to the Drosophila "heat shock consensus" sequence, are located 57 to 76 bp upstream from the capping site. Interestingly, the capping site itself is flanked by inverted repeat sequences.  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