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   15858篇
  免费   1348篇
  国内免费   67篇
耳鼻咽喉   207篇
儿科学   351篇
妇产科学   232篇
基础医学   2067篇
口腔科学   218篇
临床医学   1737篇
内科学   3411篇
皮肤病学   382篇
神经病学   973篇
特种医学   652篇
外科学   2623篇
综合类   115篇
现状与发展   1篇
一般理论   4篇
预防医学   1329篇
眼科学   523篇
药学   1156篇
中国医学   86篇
肿瘤学   1206篇
  2024年   16篇
  2023年   185篇
  2022年   458篇
  2021年   861篇
  2020年   458篇
  2019年   560篇
  2018年   650篇
  2017年   429篇
  2016年   511篇
  2015年   527篇
  2014年   664篇
  2013年   718篇
  2012年   1146篇
  2011年   1108篇
  2010年   661篇
  2009年   532篇
  2008年   909篇
  2007年   905篇
  2006年   767篇
  2005年   709篇
  2004年   624篇
  2003年   542篇
  2002年   501篇
  2001年   500篇
  2000年   455篇
  1999年   371篇
  1998年   121篇
  1997年   101篇
  1996年   91篇
  1995年   75篇
  1994年   70篇
  1993年   59篇
  1992年   152篇
  1991年   105篇
  1990年   120篇
  1989年   107篇
  1988年   93篇
  1987年   81篇
  1986年   67篇
  1985年   56篇
  1984年   48篇
  1983年   32篇
  1982年   19篇
  1981年   11篇
  1980年   16篇
  1979年   15篇
  1977年   10篇
  1976年   8篇
  1975年   9篇
  1974年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
We undertook this study to determine whether the use of contrast venography would adversely affect renal function in patients with renal insufficiency requiring caval interruption. We conducted a retrospective review of all inferior vena cava (IVC) filters inserted at our institution over a 2-year period (January 2002 to January 2004). The indication for caval interruption, insertion technique, type of filter used, pre- and postintervention creatinine level, and the presence of diabetes and hypertension were analyzed. A total of 282 IVC filters were inserted, with 38 of them placed in patients with renal insufficiency as defined by a serum creatinine level of > 1.5 mg/dL. Contrast venography with 15 to 30 mL of iohexol (Omnipaque 300) was used in all cases, and no special measures other than proper hydration were used for renal protection. All filters were successfully deployed. The mean±SD preintervention creatinine level was 2.38±0.79 mg/dL. The mean±SD postintervention creatinine levels at 2 and 30 days were 2.26±0.45 mg/dL and 2.12±0.94 mg/dL, respectively. No patients required hemodialysis following caval interruption, and no adverse effect on renal function was noted. Contrast venography accurately delineates venous anatomy and facilitates proper caval filter placement with no apparent adverse effect on renal function. We believe contrast venography is safe even in the presence of renal insufficiency.  相似文献   
993.
Exhaled breath condensate pH assays are not influenced by oral ammonia   总被引:3,自引:0,他引:3  
BACKGROUND: Measurement of pH in exhaled breath condensate (EBC) is robust and simple. Acidic source fluid (airway lining fluid) traps bases while volatilising acids, leading to EBC acidification in many lung diseases. Lower airway ammonia is one determinant of airway lining fluid pH, raising the concern that addition of the base ammonia by contamination from the mouth might confound EBC pH assays. METHODS: Three discrete methods were used to limit oral ammonia contamination of EBC collections: endotracheal intubation, oral rinsing, and -40 degrees C condenser temperatures. Separately, ammonia was removed from collected EBC samples by lyophilisation and resuspension. Intraweek and intraday variability of ammonia concentration was determined in 76 subjects, and ammonia and pH from a further 235 samples were graphically compared. Ammonia was assayed spectrophotometrically and pH was assessed after deaeration. RESULTS: Data from 1091 samples are presented. Ammonia was reduced in EBC by all methods. Endotracheal intubation decreased EBC ammonia from a mean (SD) of 619 (124) microM to 80 (24) microM (p<0.001, n=32). Oral rinsing before collection also led to a decline in EBC ammonia from 573 (307) microM to 224 (80) microM (p=0.016, n=7). The colder the condensation temperature used, the less ammonia was trapped in the EBC. Lyophilisation removed 99.4 (1.9)% of ammonia. Most importantly, the pH of EBC never decreased after removal of ammonia by any of these methods. Intraweek and intraday coefficients of variation for ammonia were 64 (27)% and 60 (32)%, which is substantially more variable than EBC pH assays. CONCLUSIONS: Although ammonia and pH appear to correlate in EBC, the oral ammonia concentration is not an important determinant of EBC pH. No precautions need to be taken to exclude oral ammonia when EBC pH is of interest. The low pH and low ammonia found in EBC from patients with lung diseases appear to be independent effects of volatile compounds arising from the airway.  相似文献   
994.
BACKGROUND: Patients who survive gunshot wounds often have retained missiles. Unlike intra-articular retained missiles, extra-articular retained missiles (EARMs) are not routinely removed. Cases of lead toxicity from EARMs have been described. This study seeks to determine whether blood lead levels are elevated in emergency department patients with EARMs compared with matched controls, whether clinical symptoms of lead toxicity are more prevalent in patients with EARMs than in controls, and whether longer missile retention times or recent hypermetabolic conditions are associated with higher blood lead levels. METHODS: One hundred twenty adults with EARMs and 120 age- and gender-matched controls with no history of gunshot wound were prospectively enrolled on presentation to a large urban emergency department. Whole blood lead (WBL), zinc protoporphyrin, and hemoglobin levels were obtained. Patients completed a questionnaire regarding time since gunshot injury; symptoms of lead toxicity; and occurrence within 30 days of any surgery, alcohol abuse, illicit drug abuse, diabetic ketoacidosis, hyperthyroidism, infection, fracture, pregnancy, or lactation. RESULTS: Five EARM patients (4%) and no control patients (0%) had WBL greater than our threshold for medical follow-up (20 microg/dL). Mean WBL was 6.71 microg/dL (95% confidence interval [CI], 5.68-7.74 microg/dL) in EARM patients and 3.16 mug/dL (95% CI, 2.79-3.53 microg/dL) in controls. This difference was statistically significant when analyzed by matched pairs t test (p = 0.0001). There was no difference in the number of symptoms associated with lead toxicity that were noted by EARM patients versus controls (p = 0.377). Longer duration of missile retention was not associated with higher blood lead levels (r = 0.125, p = 0.172). Of the five hypermetabolic conditions analyzed, only fractures were associated with elevated blood lead levels (9.95 microg/dL [95% CI, 5.77-14.13 microg/dL] in EARM patients with fractures vs. 6.23 microg/dL [95% CI, 5.23-7.23 microg/dL] in EARM patients without fractures). CONCLUSION: Patients with EARMs have significantly elevated blood lead levels compared with matched controls. The occurrence of a bony fracture within the past 30 days is associated with a higher lead level. In 96% of patients with EARMs, elevated lead levels were not clinically significant and did not change patient management.  相似文献   
995.
996.
We report a case of shoulder arthritis due to Haemophilus aphrophilus. The patient, a 56 year-old woman, was immunocompetent. She presented with a septic arthritis of the left shoulder without portal of entry. A synovial fluid sample was cultured and positive for a gram-negative bacillus after 8 days. It was identified as Haemophilus aphrophilus, in the HACCEK group, by PCR ARN 16S. We did not find any associated endocarditis. The patient recovered. As far as we know, this is only the 5th reported case of arthritis due to this microorganism.  相似文献   
997.
OBJECTIVE: To determine the impact of anthropometric characteristics and dietary patterns on Type 2 diabetes mellitus in Vietnam. METHODS: Data from 144 subjects (9m/39f newly diagnosed diabetics; 18m/78f control subjects) were analyzed in this case-control study. Height, weight, waist and hip circumferences and percent body fat were measured. Dietary intakes were assessed by 24-hour recall on three non-consecutive weekdays. Fasting blood samples were collected for the analysis of plasma glucose, fructosamine, protein and lipid concentrations. RESULTS: Although the body mass index (BMI, kg/m(2)) was similar between diabetic and control subjects, diabetic subjects had significantly greater percent body fat (31.1 +/- 5.8% vs. 27.7 +/- 6.2%) and waist-hip ratios (WHR, 0.91 +/- 0.07 vs. 0.86 +/- 0.08). Diabetic subjects had higher intakes of protein (p < 0.01), especially animal protein (p < 0.001), and consumed more meat (p < 0.01) than control subjects. Percent body fat and WHR were positively associated with diabetes (odds ratios [OR] 1.53 [95%CI 1.29-1.79] and 1.09 [95% CI 0.89-1.58], respectively) as were protein intake (OR 1.21 [95% CI 1.12-1.31]) and animal protein intake (OR 1.18 [95% CI 1.10-1.26]). CONCLUSIONS: This study indicates that percent body fat and WHR are risk factors associated with diabetes even when the BMI is normal. Evolving dietary patterns with increasingly more protein and meat consumption may also contribute to the deterioration of glucose metabolism among Vietnamese people.  相似文献   
998.
The study is based on the observation that data from the existing literature is underutilised during the project development stage. The objective is to carry out a study to track the current status quo on how the knowledge from the literature is used and incorporated. Semi-structured interviews of professionals working in nutritional education of youth were conducted to assess this aspect in the French-speaking community in Belgium. The study permitted the identification of which types of data are being used by the respondents, as well as which elements can have a positive or negative impact their incorporation. Moreover, it was observed that most of the field workers who participated in the study would prefer to have access to more data relevant to their local context than data on a specific topic. The study highlighted the need for more training to be provided to the nutritional educators working in the field, in particular in the areas of information needs and their interpretation of these needs in light of the data available.  相似文献   
999.
BACKGROUND: Occupational studies of fertility often rely on men's report of time to pregnancy (TTP). We assessed accuracy of men's report of TTP compared with TTP derived from data from their female partners. METHODS: Men from the Dieckmann diethylstilbestrol cohort were interviewed to assess fertility. Men were asked TTP for their most recent pregnancies. Their female partner was subsequently interviewed separately; TTP derived from her data was used as the gold standard. Our analysis was based on 202 couples. RESULTS: Men's report was identical to the women's-derived TTP in 32% of couples; 74% differed by no more than 2 cycles. Men tended to underestimate TTP (mean difference = -1.2 cycles). Weighted kappa was 0.5 overall and varied by the man's education, the number of pregnancies he had fathered, his stated confidence in reporting, his exposure to diethylstilbestrol, pregnancy planning, and whether he was still married to the index partner. CONCLUSIONS: Overall accuracy of men's report of TTP was reasonably good, particularly for men who had fathered only one pregnancy.  相似文献   
1000.
OBJECTIVE: To develop and validate sex-specific equations for predicting percentage body fat (%BF) in rural Thai population, based on BMI and anthropometric measurements. RESEARCH METHODS AND PROCEDURES: %BF (DXA; GE Lunar Corp., Madison, WI) was measured in 181 men and 255 women who were healthy and between 20 and 84 years old. Anthropometric measures such as weight (kilograms), height (centimeters), BMI (kilograms per meter squared), waist circumference (centimeters), hip circumference (centimeters), thickness at triceps skinfold (millimeters), biceps skinfold (millimeters), subscapular skinfold (millimeters), and suprailiac skinfold (millimeters) were also measured. The sample was randomly divided into a development group (98 men and 125 women) and a validation group (83 men and 130 women). Regression equations of %BF derived from the development group were then evaluated for accuracy in the validation group. RESULTS: The equation for estimating %BF in men was: %BF(men) = 0.42 x subscapular skinfold + 0.62 x BMI - 0.28 x biceps skinfold + 0.17 x waist circumference - 18.47, and in women: %BF(women) = 0.42 x hip circumference + 0.17 x suprailiac skinfold + 0.46 x BMI - 23.75. The coefficient of determination (R2) for both equations was 0.68. Without anthropometric variables, the predictive equation using BMI, age, and sex was: %BF = 1.65 x BMI + 0.06 x age - 15.3 x sex - 10.67 (where sex = 1 for men and sex = 0 for women), with R2 = 0.83. When these equations were applied to the validation sample, the difference between measured and predicted %BF ranged between +/-9%, and the positive predictive values were above 0.9. DISCUSSION: These results suggest that simple, noninvasive, and inexpensive anthropometric variables may provide an accurate estimate of %BF and could potentially aid the diagnosis of obesity in rural Thais.  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