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   29104篇
  免费   1684篇
  国内免费   140篇
耳鼻咽喉   278篇
儿科学   715篇
妇产科学   474篇
基础医学   3606篇
口腔科学   699篇
临床医学   2572篇
内科学   7190篇
皮肤病学   526篇
神经病学   2647篇
特种医学   779篇
外国民族医学   1篇
外科学   4260篇
综合类   239篇
一般理论   19篇
预防医学   2312篇
眼科学   566篇
药学   1675篇
中国医学   49篇
肿瘤学   2321篇
  2023年   152篇
  2022年   244篇
  2021年   581篇
  2020年   351篇
  2019年   564篇
  2018年   658篇
  2017年   499篇
  2016年   532篇
  2015年   627篇
  2014年   942篇
  2013年   1227篇
  2012年   2029篇
  2011年   2097篇
  2010年   1143篇
  2009年   1112篇
  2008年   1871篇
  2007年   2097篇
  2006年   1969篇
  2005年   1992篇
  2004年   1904篇
  2003年   1648篇
  2002年   1640篇
  2001年   340篇
  2000年   309篇
  1999年   306篇
  1998年   326篇
  1997年   242篇
  1996年   218篇
  1995年   223篇
  1994年   197篇
  1993年   189篇
  1992年   200篇
  1991年   178篇
  1990年   156篇
  1989年   149篇
  1988年   133篇
  1987年   130篇
  1986年   156篇
  1985年   160篇
  1984年   162篇
  1983年   129篇
  1982年   143篇
  1981年   139篇
  1980年   127篇
  1979年   75篇
  1978年   85篇
  1977年   60篇
  1976年   67篇
  1975年   69篇
  1974年   53篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Almost 90% of primary acute pericarditis are idiopathic. Between specifics forms, a very low percentage of cases are due to chronic rheumatic diseases. A case of adult Still's disease (juvenile chronic rheumatoid arthritis) with acute pericarditis being the first clinical manifestation (besides fever and general syndrome) is presented. Therapy with oral prednisone was rapidly effective, and pericardial effusion resolved after 3 weeks of treatment, as echocardiography showed.  相似文献   
42.
Age and gender interactions on verbal memory performance.   总被引:1,自引:0,他引:1  
Age and gender effects on verbal episodic memory are well established. However, the possibility of interactions between age and gender has been raised by studies linking estrogen and verbal memory performance, and by research suggesting gender differences in age-related cortical atrophy. We evaluated whether age by gender interactions in verbal memory were present. Subjects within three years of the median age of menopause were excluded from a large cohort of normal subjects, resulting in a younger sample (16-47 years) of 288 men and 285 women, and an older sample (55-89 years) of 201 men and 245 women. All subjects were administered the CVLT-2, a multiple-trial list-learning task. Verbal memory was negatively correlated with age for younger men, older men, and older women, but not for younger women. Multivariate analyses indicated age by gender interactions on memory for the younger group but not the older group. Results indicate that verbal memory declines with age for younger men but not younger women, whereas both older men and older women show age-related declines. These findings are consistent with hypotheses linking estrogen and verbal memory performance, and with imaging data suggesting that age-related hippocampal atrophy is found in younger men but not younger women. The role of estrogen on cognition in normal aging warrants further study.  相似文献   
43.
Introduction: Opioid-induced rigidity often makes bag-mask ventilation difficult or impossible during induction of anesthesia. Difficult ventilation may result from chest wall rigidity, upper airway closure, or both. This study further defines the contribution of vocal cord closure to this phenomenon.

Methods: With institutional review board approval, 30 patients undergoing elective cardiac surgery participated in the study. Morphine (0.1 mg/kg) and scopolamine (6 micro gram/kg) given intramuscularly provided sedation along with intravenous midazolam as needed. Lidocaine 10% spray provided topical anesthesia of the oropharynx. A fiberoptic bronchoscope positioned in the airway photographed the glottis before induction of anesthesia. A second photograph was obtained after induction with 3 micro gram/kg sufentanil administered during a period of 2 min. A mechanical ventilator provided 10 ml/kg breaths at 10/min via mask and oral airway with jaw thrust. A side-stream spirometer captured objective pulmonary compliance data. Subjective airway compliance was scored. Pancuronium (0.1 mg/kg) provided muscle relaxation. One minute after the muscle relaxant was given, a third photograph was taken and compliance measurements and scores were repeated. Photographs were scored in a random, blinded manner by one investigator. Wilcoxon signed rank tests compared groups, with Bonferroni correction. Differences were considered significant at P <0.05.

Results: Twenty-eight of 30 patients exhibited decreased pulmonary compliance and closed vocal cords after opioid induction. Two patients with neither objective nor subjective changes in pulmonary compliance had open vocal cords after opioid administration. Both subjective and objective compliances increased from severely compromised values after narcotic-induced anesthesia to normal values (P = 0.000002) after patients received a relaxant. Photo scores document open cords before induction, progressing to closed cords after the opioid (P = 0.00002), and opening again after a relaxant was administered (P = 0.00005).  相似文献   

44.
OBJECTIVES: The aim of this study was to examine the construct validity of the 7-point Likert scale of muscle soreness, assessing its relationship with Visual Analogue Scale (VAS). An additional aim was to examine its sensitivity as measure of symptom of eccentric-contraction muscle damage. DESIGN: Correlational study. SETTING: Self-administered questionnaires collected in field setting. PARTICIPANTS: Twenty-six soccer players. INTERVENTIONS: 4-week preseason training camp, which included high-intensity plyometric training sessions. MAIN OUTCOME MEASUREMENTS: Players self-reported the perceived muscle soreness of the lower limbs using the VAS (criterion measure) and the 7-point Likert scale of muscle soreness. RESULTS: Significant individual correlations were found between the 2 muscle soreness scales (mean r=0.80+/-0.07; range, 0.65 to 0.94). The correlation using the pooled data was 0.81. No significant muscle soreness scale x time interaction was found for standardized measures of muscle soreness (P=0.98). The main factor for time (24, 48, 72, and 96 hours after the first plyometric training session) was significant (P=0.0001). Effect sizes for the changes in the Likert and VAS absolute scores during the first 96 hours were similar (partial eta=0.13). CONCLUSIONS: The results of this study provide further convergent evidence for the construct validity of the 7-point Likert scale of muscle soreness. The 2 scales showed similar sensitivity to muscle soreness caused by eccentric contractions during the first 96 hours after plyometric exercises.  相似文献   
45.
S100A1 is a calcium-binding protein, which has been recently found in renal cell neoplasms. We evaluated the diagnostic utility of immunohistochemical detection of S100A1 in 164 renal cell neoplasms. Forty-one clear cell, 32 papillary, and 51 chromophobe renal cell carcinomas, and 40 oncocytomas, 164 samples of normal renal parenchyma adjacent to the tumors and 13 fetal kidneys were analyzed. The levels of S100A1 mRNA detected by quantitative RT-PCR analysis of frozen tissues from seven clear cell, five papillary, and six chromophobe renal cell carcinomas, four oncocytomas, and nine samples of normal renal tissues adjacent to neoplasms were compared with the immunohistochemical detection of protein expression. Clear cell and papillary renal cell carcinomas showed positive reactions for S100A1 in 30 out of 41 tumors (73%) and in 30 out of 32 (94%) tumors, respectively. Thirty-seven renal oncocytomas out of 40 (93%) were positive for S100A1, whereas 48 of 51 (94%) chromophobe renal cell carcinomas were negative. S100A1 protein was detected in all samples of unaffected and fetal kidneys. S100A1 mRNA was detected by RT-PCR in all normal kidneys and renal cell neoplasms, although at very different levels. Statistical analyses comparing the different expression of S100A1 in clear cell and chromophobe renal cell carcinomas observed by immunohistochemical and RT-PCR methods showed significant values (P<0.001), such as when comparing by both techniques the different levels of S100A1 expression in chromophobe renal cell carcinomas and oncocytomas (P<0.001). Our study shows that S100A1 protein is expressed in oncocytomas, clear cell and papillary renal cell carcinomas but not in chromophobe renal cell carcinomas. Its immunodetection is potentially useful for the differential diagnosis between chromophobe renal cell carcinoma and oncocytoma. Further, S100A1 protein expression is constantly detected in the normal parenchyma of the adult and fetal kidney.  相似文献   
46.
BACKGROUND AND OBJECTIVE: In recent years, new classes of medication, such as the serotonin-noradrenaline reuptake inhibitors (SNRIs), have been developed for use in the treatment of major depressive disorder (MDD). For many years, treatment options were largely limited to the use of monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs). However, there have been published reports of orthostatic hypotension, arrhythmias and corrected QT (QTc) interval changes in patients treated with TCAs. As new medications become available, it is important to understand how their cardiovascular safety profile compares with that of more established agents to aid clinicians and patients in choosing the best treatment options. This study was designed to evaluate the cardiovascular safety profile of the SNRI duloxetine through evaluation of cardiovascular-related parameters and adverse events (AEs). METHODS: The cardiovascular safety of duloxetine was assessed using all placebo-controlled duloxetine clinical trial data as of December 2005. This consisted of data from 42 placebo-controlled clinical trials of 8504 patients who were treated with duloxetine. Additional information from a high-dose clinical pharmacology study and postmarketing safety surveillance are also presented. Of the placebo-controlled trials included in this analysis, clinical indications under investigation included MDD (15 studies), diabetic peripheral neuropathic pain (3 studies), fibromyalgia (2 studies), generalised anxiety disorder (3 studies) and lower urinary tract disorders (19 studies, all related to incontinence). Cardiovascular safety was evaluated based on vital signs, ECGs and the incidence of treatment-emergent AEs potentially related to cardiovascular safety. These safety parameters were analysed across all indications. To identify both serious and non-serious cardiovascular-related AEs, as well as AEs reported as the reason for discontinuation, a comprehensive list of terms derived from the Medical Dictionary for Regulatory Activities (version 8.0) was generated and used to search the duloxetine databases for cardiovascular-related events. RESULTS: Calculation of change from baseline to maximum in ECG parameters showed significant differences between treatment groups for all parameters, with decreases from baseline in RR, QRS and QT intervals for patients receiving duloxetine and increases from baseline for patients treated with placebo. These shifts were related to small heart rate changes, but the mean differences were not considered clinically relevant. Categorical analyses of shifts from normal to abnormal (or abnormal to normal) for heart rate and QT corrected for heart rate using Fridericia's formula (QTcF) values showed that most patients did not shift from their baseline category. Patients with MDD who were treated for up to 1 year with duloxetine had blood pressure changes early in treatment that then stabilised. Even in patients with elevated blood pressure at baseline in these clinical trials, no increased risk of sustained blood pressure elevation with duloxetine treatment was found. CONCLUSION: Overall, the findings presented here support our conclusions that use of duloxetine does not appear to be associated with significant cardiovascular risks in patients with conditions for which the drug has been approved or studied.  相似文献   
47.
Background: Erythrocytes are transfused to improve oxygen delivery and prevent or treat inadequate oxygenation of tissues. Acute isovolemic anemia subtly slows human data processing and degrades memory, increases heart rate, and decreases self-assessed energy level. Erythrocyte transfusion is efficacious in reversing these effects of acute anemia. We tested the hypothesis that increasing arterial oxygen pressure (Pao2) to 350 mmHg or greater would supply sufficient oxygen to be equivalent to augmenting hemoglobin concentration by 2-3 g/dl and thus reverse the effects of acute anemia.

Methods: Thirty-one healthy volunteers, aged 28 +/- 4 yr (mean +/- SD), were tested with verbal memory and standard, computerized neuropsychologic tests before and twice after acute isovolemic reduction of their hemoglobin concentration to 5.7 +/- 0.3 g/dl. Two sets of tests were performed in randomized order at the lower hemoglobin concentration: with the volunteer breathing room air or oxygen. The subject and those administering the tests and recording the results were unaware which gas was administered. As an additional control for duration of the experiment, 10 of these volunteers also completed the same tests on a separate day, without alteration of hemoglobin concentration, at times of the day similar to those on the experimental day. Heart rate, mean arterial blood pressure, and self-assessed sense of energy were recorded at the time of each test.

Results: Reaction time for digit-symbol substitution test increased, delayed memory was degraded, mean arterial pressure and energy level decreased, and heart rate increased at a hemoglobin concentration of 5.7 g/dl (all P < 0.05). Increasing Pao2 to 406 +/- 47 mmHg reversed the digit-symbol substitution test result and the delayed memory changes to values not different from those at the baseline hemoglobin concentration of 12.7 +/- 1.0 g/dl, and decreased heart rate (P < 0.05). However, mean arterial pressure and energy level changes were not altered with increased Pao2 during acute anemia.  相似文献   

48.
49.
50.
The aim of this study was to determine the diagnostic accuracy of technetium-99m tetrofosmin myocardial imaging for the localization of coronary artery stenoses of different degrees of severity. Stress-rest single-photon emission tomography (SPET) was performed on separate days in 80 patients (64 males, 16 females; mean age 61 years; 43 patients with previous myocardial infarction; 18 patients with pharmacological stress), within 6 months of coronary angiography. Scintigraphic images were blindly and independently evaluated by three observers. Coronary stenosis was defined as a >50% narrowing in luminal diameter; severe stenosis was defined as a proximal stenosis of >75% or a peripheral stenosis of >90%. Coronary angiography revealed normal coronary arteries or insignificant coronary stenosis in 13 patients and significant coronary stenoses in 67 patients. The sensitivity and specificity of 99mTc-tetrofosmin SPET in respect of severely stenosed vessels were, respectively, 80% and 65% for the left anterior descending artery (LAD), 100% and 46% for the right coronary artery (RCA) and 58 and 78% for the left circumflex artery (LCx) territories. Considering all the significantly stenosed vessels, a significant decrease in sensitivity was observed for LAD territories (to 59%, P=0.05), and a nonsignificant decrease for RCA (88%) and LCx (47%) territories while specificity values remained essentially unchanged. No significant changes in sensitivity or specificity were observed when regions with previous myocardial infarction were excluded. In conclusion, the sensitivity of 99mTc-tetrofosmin SPET for the localization of individual stenosed vessels is only moderate when all significant stenoses are considered, but the ability of this technique to predict the location of severe coronary artery stenoses seems satisfactory, with the exception of the low specificity in respect of RCA territories. Received 26 April and in revised form 7 June 1997  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