全文获取类型
收费全文 | 36784篇 |
免费 | 2771篇 |
国内免费 | 104篇 |
专业分类
耳鼻咽喉 | 395篇 |
儿科学 | 1075篇 |
妇产科学 | 1103篇 |
基础医学 | 5510篇 |
口腔科学 | 532篇 |
临床医学 | 5173篇 |
内科学 | 6476篇 |
皮肤病学 | 714篇 |
神经病学 | 4093篇 |
特种医学 | 864篇 |
外科学 | 3407篇 |
综合类 | 298篇 |
现状与发展 | 1篇 |
一般理论 | 34篇 |
预防医学 | 3876篇 |
眼科学 | 639篇 |
药学 | 2393篇 |
中国医学 | 44篇 |
肿瘤学 | 3032篇 |
出版年
2023年 | 284篇 |
2022年 | 435篇 |
2021年 | 916篇 |
2020年 | 603篇 |
2019年 | 931篇 |
2018年 | 1125篇 |
2017年 | 866篇 |
2016年 | 962篇 |
2015年 | 988篇 |
2014年 | 1402篇 |
2013年 | 1817篇 |
2012年 | 2883篇 |
2011年 | 2986篇 |
2010年 | 1605篇 |
2009年 | 1478篇 |
2008年 | 2497篇 |
2007年 | 2566篇 |
2006年 | 2327篇 |
2005年 | 2407篇 |
2004年 | 2163篇 |
2003年 | 2020篇 |
2002年 | 1899篇 |
2001年 | 303篇 |
2000年 | 197篇 |
1999年 | 339篇 |
1998年 | 425篇 |
1997年 | 372篇 |
1996年 | 299篇 |
1995年 | 280篇 |
1994年 | 220篇 |
1993年 | 201篇 |
1992年 | 178篇 |
1991年 | 151篇 |
1990年 | 125篇 |
1989年 | 132篇 |
1988年 | 103篇 |
1987年 | 110篇 |
1986年 | 94篇 |
1985年 | 83篇 |
1984年 | 109篇 |
1983年 | 73篇 |
1982年 | 71篇 |
1981年 | 85篇 |
1980年 | 81篇 |
1979年 | 57篇 |
1978年 | 47篇 |
1977年 | 61篇 |
1976年 | 41篇 |
1975年 | 33篇 |
1974年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Exercise metabolism in healthy volunteers taking celiprolol, atenolol, and placebo. 总被引:2,自引:2,他引:0 下载免费PDF全文
OBJECTIVE: Previous studies have shown that beta 1 selective agents have fewer adverse effects on exercise metabolism than nonselective beta blockers, and this has been attributed to their reduced blockade of beta 2 receptors. This study aimed at determining whether a beta blocker with partial agonist activity at beta 1 and beta 2 receptors (celiprolol) was better than a conventional beta 1 receptor-blocker (atenolol) in prolonging exercise capabilities. METHODS: After four days of treatment with celiprolol 200 mg, atenolol 50 mg, or placebo, 22 healthy volunteers exercised on a treadmill for two hours at 50% of their maximal oxygen uptake. Resting heart rate and blood pressure were recorded before and after exercise. During exercise, fat oxidation, plasma free fatty acids, glycerol, glucose, and ammonia were measured together with heart rate and perceived exertion. RESULTS: Mean exercising heart rate was significantly lower in those taking either of the beta blockers than in those taking placebo, and significantly lower for those taking atenolol rather than celiprolol. Fat oxidation was significantly lower for those taking celiprolol (38.8 (SD 12.2)%, P < 0.01) and atenolol (36.6 (15.9)%, P < 0.01) compared with placebo (45.6 (14.1)%). For the first 15 minutes of exercise, fat oxidation was significantly lower for those taking atenolol (24.6 (12.8)%, P < 0.01) than celiprolol (29.6 (14.3)%). The rise in plasma free fatty acids and glycerol during exercise was also significantly attenuated by both beta blockers in comparison with the rise in those taking placebo (P < 0.01). CONCLUSIONS: Both celiprolol and atenolol reduced fat oxidation compared with placebo. For the first 15 minutes of exercise fat oxidation was preserved by celiprolol, but not atenolol. This preservation of fat oxidation during the early part of exercise may confer some small benefit to patients who take beta blockers and intend to exercise regularly. However, we did not detect significant differences between atenolol and celiprolol in overall mean fat oxidation or perceived exertion in this study. 相似文献
62.
During a 12-month period 115 patients with abnormal mammograms had stereotaxic needle localization and biopsy of nonpalpable breast lesions. The procedure was performed on a Fischer Mammotest II machine (Fischer Imaging; Denver, CO) and the biopsies were taken with a #18 gauge Bard biopsy needle using a Bard biopty gun (distributed by Bard Urological; Covington, GA; manufactured by Radiplast; Uppsala, Sweden). Mammographic lesions were suspicious matrix densities (85), clustered microcalcifications (22), or a combination of both (8). The pathologist recommended open biopsy in 16 per cent (18/115) of the patients. Pathology on the 18 open biopsies revealed that 11 (9 matrix densities and 2 calcifications) were carcinomas and true positives, whereas the other 7 (all matrix densities) were benign mastopathies and false positives. Further analysis of the pathologic data showed that there were three possible diagnoses from the needle biopsies on the patients that later went to open biopsy: cancer (6), very suspicious lesion (9), and slightly suspicious lesion without atypical hyperplasia (3). All 6 cancers were confirmed by open biopsy; about half (5/9) of the very suspicious lesions were cancer and none (0/3) of the slightly suspicious lesions were cancer. More cases, followed by open biopsy, are needed to refine the selection procedure for open biopsy and careful follow-up of the patients who did not have open biopsy will also be needed to determine the false negative rate. Excellent patient acceptance was found and the test was easy to perform in the office without serious complications. Furthermore, the test was cost effective because it avoided open biopsy in 97 patients. 相似文献
63.
64.
Morphometric studies conducted on the blood vessels of the spontaneously hypertensive rat have provided evidence that medial hypertrophy is a key characteristic of the vascular change which occurs in hypertension. In the present study, we determined whether 3-methylhistidine (3MH), a post-translationally modified amino acid which is found uniquely in the actin and myosin of muscle, could provide a biochemical marker of such change. Our results indicated that the concentrations of 3MH were selectively elevated in the blood vessels from the spontaneously hypertensive rat, when compared with concentrations in vascular tissues from the Wistar-Kyoto rat. The concentrations of 3MH in non-vascular tissues were similar in the two strains. Chronic captopril treatment prevented the development of hypertension in the spontaneously hypertensive rat and was associated with a reduction of the vascular concentrations of 3MH. We therefore conclude that blood vessel concentrations of 3MH are a useful biochemical index of the changes in vascular smooth muscle contractile protein which occur during the development of hypertension in the spontaneously hypertensive rat. 相似文献
65.
R J Head 《Blood vessels》1991,28(1-3):173-178
Two distinguishing features of the vasculature of the spontaneously hypertensive rat (SHR) are an increased sympathetic innervation and vascular smooth muscle hyperplasia. Evidence supporting the existence of hypernoradrenergic innervation and vascular smooth muscle cell hyperplasia is presented with emphasis upon the possible interrelationships between the two events. The results of experiments designed to explore this relationship are presented and include the determination of the role of endogenous nerve growth factor (NGF) and the influence of exogenous NGF on the development of sympathetic innervation of blood vessels and blood pressure change. Attention is focused upon elevated levels of 3-methylhistidine (a biochemical marker for contractile proteins) in the mesenteric vasculature of the SHR. The potential relationships between hypernoradrenergic innervation and increased concentrations of 3-methylhistidine are explored. 相似文献
66.
Why should depression screening be conducted in chronically ill populations? Depression is a disabling illness and is very common among patients who have chronic illnesses. Despite its high prevalence in this patient population, depression often goes unrecognized. Having a plan for a population-based screening program for depression can not only identify patients who are at risk of depression, but can also help to foster early treatment and enhanced care for these patients. This article provides an overview of commonly-used depression screening tools and presents an example of how this might be carried out in a healthcare organization. 相似文献
67.
Explanations of cancer need to take into account developmental changes in children's cognitive and emotional abilities to understand illness. Children below 5 years of age are usually informed by parents, and older children by medical staff. Information tends to focus on details of treatments and procedures, and less on the seriousness of the disease and length of time involved. There are indications that early and honest information is associated with better behaviour and adjustment in the child, communication within the family and compliance with treatment, although methodological inadequacies in assessment of adjustment and knowledge of cancer limit the ability to generalize these findings. Communication with children should take into account developmental changes in children's ability to understand illness information. Communicators should also provide emotional support to deal with the threatening nature of this information. 相似文献
68.
Lynn Ware M.D. Dr. David Muram M.D. Christine L. Gale M.D. 《Sexuality and disability》1992,10(3):189-192
In some patients with mental retardation, a Q-tip pap smear obtained blindly from the upper vagina may be the only cytologic smear obtainable without subjecting the patient to heavy sedation or to examination under anesthesia. The efficacy of blind Q-tip smears has not been previously determined. Of 31 Q-tip smears obtained from patients with CIN, the Q-tip smear identified the abnormality in 10 (32%) patients. For those patients who will not submit to examination without anesthesia or sedation, routine screening with multiple smears, obtained on an annual basis has the potential to identify many cases of CIN which otherwise would not be identified at all, and in certain patients, this method outweighs the risks of heavy sedation or general anesthesia. Because of the greatly reduced sensitivity of the Q-tip pap, every effort should be made to help the patient and/or her family or guardian to understand the implications and risks of this method. However, if an examination under anesthesia is performed for other indications, a complete gynecologic examination and a direct smear should be obtained at that time. 相似文献
69.
An important methodological issue in depressionanalog research is whether individuals who scoreextremely low on self-report measures like the BeckDepression Inventory (BDI) should be included innondepressed control groups. Joiner, Schmidt, and Metalsky(1994) found that college students with BDI scores of 0or 1 evidenced a fake-good test taking style as measuredby the MMPI validity scales. The present study investigated whether very low BDI scores (BDI= 0 or 1; n = 21) might be associated with an elevatedpositive mood state, extreme optimism, positiveattributional style or social desirability. Resultsindicated that the very low scoring BDI subjects scoredhigher on social desirability than the low scoring group(BDI = 2 9, n = 63). Significant differences on mood,symptom and cognitive measures disappeared when social desirability was entered as a covariate.Findings support Kendall, Hollon, Beck, Hammen, andIngram's (1987) recommendation that subjects who score0 or 1 on the BDI should be excluded from a nondepressed control group. 相似文献
70.