全文获取类型
收费全文 | 7643篇 |
免费 | 694篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 86篇 |
儿科学 | 316篇 |
妇产科学 | 193篇 |
基础医学 | 863篇 |
口腔科学 | 244篇 |
临床医学 | 841篇 |
内科学 | 1483篇 |
皮肤病学 | 77篇 |
神经病学 | 703篇 |
特种医学 | 450篇 |
外科学 | 845篇 |
综合类 | 203篇 |
一般理论 | 5篇 |
预防医学 | 879篇 |
眼科学 | 68篇 |
药学 | 622篇 |
中国医学 | 4篇 |
肿瘤学 | 490篇 |
出版年
2022年 | 43篇 |
2021年 | 110篇 |
2020年 | 71篇 |
2019年 | 128篇 |
2018年 | 124篇 |
2017年 | 116篇 |
2016年 | 120篇 |
2015年 | 133篇 |
2014年 | 172篇 |
2013年 | 231篇 |
2012年 | 365篇 |
2011年 | 392篇 |
2010年 | 216篇 |
2009年 | 212篇 |
2008年 | 312篇 |
2007年 | 327篇 |
2006年 | 309篇 |
2005年 | 293篇 |
2004年 | 342篇 |
2003年 | 289篇 |
2002年 | 259篇 |
2001年 | 230篇 |
2000年 | 230篇 |
1999年 | 199篇 |
1998年 | 142篇 |
1997年 | 144篇 |
1996年 | 157篇 |
1995年 | 113篇 |
1994年 | 101篇 |
1993年 | 97篇 |
1992年 | 159篇 |
1991年 | 133篇 |
1990年 | 200篇 |
1989年 | 165篇 |
1988年 | 140篇 |
1987年 | 157篇 |
1986年 | 136篇 |
1985年 | 157篇 |
1984年 | 114篇 |
1983年 | 106篇 |
1982年 | 51篇 |
1981年 | 60篇 |
1980年 | 42篇 |
1979年 | 81篇 |
1978年 | 48篇 |
1977年 | 63篇 |
1976年 | 67篇 |
1975年 | 42篇 |
1974年 | 62篇 |
1972年 | 51篇 |
排序方式: 共有8372条查询结果,搜索用时 0 毫秒
161.
The purpose of this study was to examine the associations between smoking, physical inactivity, obesity, and asthma severity among US adults. The magnitude of these associations was very strong. For example, those who visited an emergency room in the past year were 60% more likely than those who did not to smoke; those who used an inhaler ≥15 times in the past month (versus those who did not use an inhaler) were 90% more likely to be physically inactive; and those who had asthma symptoms all the time in the past 30 days (versus those with no symptoms) were 80% more likely to be obese. 相似文献
162.
Christy M. King Graham A. Hamilton Mathew Cobb Diane Carpenter Lawrence A. Ford 《The Journal of foot and ankle surgery》2012,51(5):543-547
Obesity is an epidemic in the United States and is associated with an increased risk of musculoskeletal problems. Rotational injuries of the ankle with a Weber C fibula fracture have a greater risk of syndesmosis disruption and instability. The goal of the present study was to explore the association between obesity and ankle fractures. Using a retrospective review, the radiographs of 280 patients with an ankle fracture were reviewed and classified using the Weber classification, which was then associated with the body mass index, gender, age, diabetes, tobacco use, and osteoporosis. Patients with a body mass index of 30 kg/m2 or greater (odds ratio 1.78), men (odds ratio 1.74), and age 25 years or younger (odds ratio 3.97) had greater odds of having a Weber C ankle fracture (compared with Weber A and B) and Weber C and B (compared with Weber A). Diabetes mellitus, osteoporosis/osteopenia, and current tobacco use were not significantly associated with the severity of the ankle fracture. The results from the present study suggest that obesity presents a greater risk of sustaining a more proximal distal fibula fracture. 相似文献
163.
164.
Y E Hsia J Yuen J A Hunt P Rattamanasay J Hall N Takaesu E A Titus J Fujita C A Ford 《Hemoglobin》1988,12(5-6):465-484
From May 1985 to October 1987, 1,564 Southeast Asians living in Hawaii were screened for hereditary anemias. Microcytosis was determined by electronic red cell indices and morphology; iron deficiency was ruled out by normal red cell distribution width and normal protoporphyrin levels; Hb E was determined by electrophoresis; beta-thalassemia (thal) heterozygotes were identified by raised Hb A2 on column chromatography. alpha-Thalassemia heterozygotes were diagnosed by exclusion. Family studies helped identify or confirm diagnoses, especially for the alpha-thal-2 heterozygotes (-alpha/alpha alpha) and homozygotes (-alpha/-alpha). Provisional diagnoses are being checked by DNA analyses. Iron deficiency prevented detection of possibly coexisting alpha-thalassemias in 97 individuals. Technical problems included the obscuring of standard criteria for recognizing the alpha-thal variants by the presence of Hb E or beta-thal. In such cases, alpha-thal could only be detected by family studies or DNA analyses. Problems with hemoglobin (Hb) electrophoresis included Hb H migrating beyond the edge of the strip if incubation was not closely monitored, and difficulty in detecting the small amounts of unstable Hb Constant Spring. DNA analyses also had limitations, since the nondeletion alpha-thalassemias would not be detected by routine Southern blotting. DNA analyses suggested that about 50% of presumed alpha-thalassemias were alpha-thal-2 (-alpha/alpha alpha) variants, and a corresponding number of alpha-thal-2 variants were among the apparent normals. Gene frequencies in the unselected Lao subjects were approximately 0.2 for Hb E, at least 0.1 for (-alpha), usually a rightward (alpha -3.7) type, 0.04 for (-), and 0.01 for a beta-thal. Multistep screening for the alpha- and beta-thalassemias was an effective and efficient strategy. 相似文献
165.
166.
BACKGROUND: Few national estimates of the prevalence of coronary heart disease in the United States are available. METHODS: By using data from the Third National Health and Nutrition Examination Survey (1988 to 1994), we estimated prevalence of angina pectoris by questionnaire, self-reported myocardial infarction, and electrocardiographically (ECG)-defined myocardial infarction. RESULTS: Among participants aged >/=40 years who attended the medical examination, the age-adjusted prevalence of angina pectoris, self-reported myocardial infarction, and ECG-defined myocardial infarction were 5.8% of 9255, 6.7% of 9250, and 3.0% of 8206 participants, respectively. Among participants aged >/=65 years compared with those aged 40 to 64 years, the prevalence of a self-reported myocardial infarction was more than 3 times higher and that of ECG-defined myocardial infarction more than 4 times higher. The prevalences of self-reported myocardial infarction and ECG-defined myocardial infarction, but not angina pectoris, were higher among men than women. Among women, prevalence of angina pectoris and self-reported myocardial infarction were highest among blacks; among men, these coronary heart diseases were somewhat higher among whites. Prevalence of ECG-defined myocardial infarction were similar for all 3 race or ethnicity groups in either sex. The age-adjusted prevalence of coronary heart disease defined by the presence of any of these conditions was 13.9% among men and 10.1% among women. CONCLUSIONS: Although the management of coronary heart disease has improved during the past 2 decades, it remains an important prevalent disease burden among adults. 相似文献
167.
Thombs BD Fuss S Hudson M Schieir O Taillefer SS Fogel J Ford DE Baron M;Canadian Scleroderma Research Group 《Arthritis and rheumatism》2008,59(3):431-437
OBJECTIVE: Between 36% and 65% of patients with systemic sclerosis (SSc) report symptoms of depression above cutoff thresholds on self-report questionnaires. The objective of this study was to assess whether these high rates result from differential reporting of somatic symptoms related to the high physical burden of SSc. METHODS: Symptom profiles reported on the Center for Epidemiologic Studies Depression Scale (CES-D) were compared between a multicenter sample of 403 patients with SSc and a sample of respondents to an Internet depression survey, matched on total CES-D score, age, race/ethnicity, and sex. An exact nonparametric generalized Mantel-Haenszel procedure was used to identify differential item functioning between groups. RESULTS: Patients with SSc reported significantly higher frequencies (moderate to large effect size; P < 0.01) on 4 CES-D somatic symptom items: bothered, appetite, effort, and sleep. Internet respondents had higher item scores on 2 items that assessed interpersonal difficulties (unfriendly, large effect size; P < 0.01; disliked, large effect size; P < 0.01) and on 2 items that assessed lack of positive effect (happy, moderate effect size; P = 0.01; enjoy, large effect size; P < 0.01). Adjustment of standard CES-D cutoff criteria for potential bias due to somatic symptom reporting resulted in a reduction of only 3.6% in the number of SSc patients with significant symptoms of depression. CONCLUSION: High rates of depressive symptoms in SSc are not due to bias related to the report of somatic symptoms. The pattern of differential item functioning between the SSc and Internet groups, however, suggests some qualitative differences in depressive symptom presentation. 相似文献
168.
GOALS: This study characterizes cardiovascular autonomic function in women with irritable bowel syndrome (IBS), using standardized techniques. BACKGROUND: Autonomic dysfunction is believed to contribute to abnormal gastrointestinal motility and visceral hypersensitivity in IBS. There is mounting evidence of generalized impairment of autonomic activity in patients with IBS. STUDY: Thirty women aged 39 years (95% C.I. 25-53 years) diagnosed with IBS, and 30 age-matched healthy women were studied. The ratio of low frequency to high frequency heart rate variability domains (LF:HF ratio) was used to represent cardiac sympathovagal activity, and orthostatic testing and sustained isometric handgrip exercise were used as sympathetic stimuli. Parasympathetic activity was represented by the expiratory to inspiratory R-R interval (E:I) ratio during deep breathing at 6 minutes. RESULTS: LF:HF responses to handgrip exercise (316%, C.I. 134% to 498% vs. 107%, C.I. 15% to 153%; P < 0.05) and orthostatic testing (648%, C.I. 520% to 904% vs. 330%, C.I. 140% to 520%; P < 0.05) were higher in IBS patients than controls, and the E:I ratio was significantly lower (1.47, C.I. 1.33-1.61 vs. 1.20, C.I. 1.14-1.26; P < 0.01). CONCLUSIONS: Autonomic cardiovascular function is impaired in IBS, manifest as attenuated cardio-vagal tone, and relative sympathetic excess during stimulated conditions. 相似文献
169.
170.
Sugar-sweetened soft drinks, diet soft drinks, and serum uric acid level: the Third National Health and Nutrition Examination Survey 总被引:1,自引:0,他引:1
OBJECTIVE: Sugar-sweetened soft drinks contain large amounts of fructose, which may significantly increase serum uric acid levels and the risk of gout. Our objective was to evaluate the relationship between sugar-sweetened soft drink intake, diet soft drink intake, and serum uric acid levels in a nationally representative sample of men and women. METHODS: Using data from 14,761 participants age>or=20 years from the Third National Health and Nutrition Examination Survey (1988-1994), we examined the relationship between soft drink consumption and serum uric acid levels using linear regression. Additionally, we examined the relationship between soft drink consumption and hyperuricemia (serum uric acid level>7.0 mg/dl for men and >5.7 mg/dl for women) using logistic regression. Intake was assessed by a food-frequency questionnaire. RESULTS: Serum uric acid levels increased with increasing sugar-sweetened soft drink intake. After adjusting for covariates, serum uric acid levels associated with sugar-sweetened soft drink consumption categories (<0.5, 0.5-0.9, 1-3.9, and >or=4 servings/day) were greater than those associated with no intake by 0.08, 0.15, 0.33, and 0.42 mg/dl, respectively (95% confidence interval 0.11, 0.73; P<0.001 for trend). The multivariate odds ratios for hyperuricemia according to the corresponding sweetened soft drink consumption levels were 1.01, 1.34, 1.51, and 1.82, respectively (P=0.003 for trend). Diet soft drink consumption was not associated with serum uric acid levels or hyperuricemia (multivariate P>0.13 for trend). CONCLUSION: These findings from a nationally representative sample of US adults suggest that sugar-sweetened soft drink consumption is associated with serum uric acid levels and frequency of hyperuricemia, but diet soft drink consumption is not. 相似文献