全文获取类型
收费全文 | 17195篇 |
免费 | 2187篇 |
国内免费 | 89篇 |
专业分类
耳鼻咽喉 | 116篇 |
儿科学 | 755篇 |
妇产科学 | 336篇 |
基础医学 | 2502篇 |
口腔科学 | 502篇 |
临床医学 | 1886篇 |
内科学 | 3876篇 |
皮肤病学 | 176篇 |
神经病学 | 1188篇 |
特种医学 | 871篇 |
外科学 | 2589篇 |
综合类 | 467篇 |
一般理论 | 15篇 |
预防医学 | 1697篇 |
眼科学 | 205篇 |
药学 | 1450篇 |
中国医学 | 5篇 |
肿瘤学 | 835篇 |
出版年
2021年 | 212篇 |
2020年 | 152篇 |
2019年 | 205篇 |
2018年 | 241篇 |
2017年 | 191篇 |
2016年 | 167篇 |
2015年 | 220篇 |
2014年 | 344篇 |
2013年 | 474篇 |
2012年 | 680篇 |
2011年 | 688篇 |
2010年 | 397篇 |
2009年 | 387篇 |
2008年 | 676篇 |
2007年 | 792篇 |
2006年 | 703篇 |
2005年 | 711篇 |
2004年 | 687篇 |
2003年 | 690篇 |
2002年 | 693篇 |
2001年 | 620篇 |
2000年 | 647篇 |
1999年 | 569篇 |
1998年 | 306篇 |
1997年 | 271篇 |
1996年 | 288篇 |
1995年 | 250篇 |
1994年 | 251篇 |
1993年 | 239篇 |
1992年 | 459篇 |
1991年 | 434篇 |
1990年 | 434篇 |
1989年 | 398篇 |
1988年 | 366篇 |
1987年 | 350篇 |
1986年 | 327篇 |
1985年 | 364篇 |
1984年 | 279篇 |
1983年 | 227篇 |
1982年 | 182篇 |
1981年 | 186篇 |
1980年 | 149篇 |
1979年 | 236篇 |
1978年 | 178篇 |
1977年 | 195篇 |
1976年 | 148篇 |
1975年 | 168篇 |
1974年 | 202篇 |
1973年 | 203篇 |
1972年 | 134篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
C Lee R Salim D Ofili-Yebovi J Yazbek A Davies D Jurkovic 《Ultrasound in obstetrics & gynecology》2006,28(6):837-841
OBJECTIVE: To determine the intraobserver and interobserver reproducibility of measurement of the percentage of protrusion of submucous fibroids into the uterine cavity using three-dimensional saline contrast sonohysterography (3D-SCSH). METHODS: Women diagnosed with submucous uterine fibroids on B-mode two-dimensional (2D) ultrasound scan were invited to join the study and 3D-SCSH was carried out. 3D volume datasets were stored digitally and were examined later using the technique of planar reformatted sections. The reproducibilities of the measurement of fibroid diameter and protrusion ratio into the uterine cavity (ratio of the size of the segment of the fibroid protruding into the cavity to the total diameter of the fibroid) were examined by two independent observers who were unaware of the initial 2D scan findings. Interobserver reproducibility was assessed by calculating the difference between measurements taken by the two operators (limits of agreement) and interclass correlation coefficient. Intraobserver repeatability was assessed by calculating the difference between two measurements for each variable (limits of agreement) and further expressed as an intraclass correlation coefficient. RESULTS: Thirty-three 3D ultrasound volumes were examined. There was a good agreement between the observers in classifying the fibroids as greater or less than 50% confined to the myometrium (Cohen's kappa 0.81). There was no bias in measurements for both variables either between observers or with repeated measurements by each observer. For fibroid diameter and protrusion ratio the inter- and intraclass correlation coefficients were high (0.984-0.995), with narrow limits of agreement. CONCLUSION: 3D-SCSH is a reproducible method for the quantification of the percentage of a submucous fibroid protruding into the uterine cavity. 相似文献
33.
目的:次极量运动过程中摄氧量(VO2)的降低,妨碍了对慢性心力衰竭(CH F)患者依据峰值运动VO2预测生存情况。摄氧效率斜率(OUES)是对运动的通气反应的非线性描绘,甚至在运动早期就可能反映出异常。作者评价了OUES的生理学意义及其对CH F患者预后信息的潜在价值。方法和结果:243例 相似文献
34.
The contribution of transforming growth factor-beta and epidermal growth factor signalling to airway remodelling in chronic asthma. 总被引:6,自引:0,他引:6
Asthma is increasing in prevalence in the developing world, affecting approximately 10% of the world's population. It is characterised by chronic lung inflammation and airway remodelling associated with wheezing, shortness of breath, acute bronchial hyperresponsiveness to a variety of innocuous stimuli and a more rapid decline in lung function over time. Airway remodelling, involving proliferation and differentiation of mesenchymal cells, particularly myofibroblasts and smooth muscle cells, is generally refractory to corticosteroids and makes a major contribution to disease chronicity. Transforming growth factor-beta is a potent profibrogenic factor whose expression is increased in the asthmatic airways and is a prime candidate for the initiation and persistence of airway remodelling in asthma. This review highlights the role of transforming growth factor-beta in the asthmatic lung, incorporating biosynthesis, signalling pathways and functional outcome. In vivo, however, it is the balance between transforming growth factor-beta and other growth factors, such as epidermal growth factor, which will determine the extent of fibrosis in the airways. A fuller comprehension of the actions of transforming growth factor-beta, and its interaction with other signalling pathways, such as the epidermal growth factor receptor signalling cascade, may enable development of therapies that control airway remodelling where there is an unmet clinical need. 相似文献
35.
S J Virk F X Qiang N H Anfilogoff R G Murray W A Littler M K Davies 《The American journal of cardiology》1991,67(12):48C-52C; discussion 52C-54C
Xamoterol, a new beta 1 partial agonist, has the potential to modulate cardiac response to variations in sympathetic tone in patients with heart failure. Its properties should result in beta-receptor stimulatory effects at low levels of sympathetic tone and beta-receptor protective effects at higher levels of sympathetic tone. The acute effects of intravenous (i.v.) xamoterol on hemodynamics at rest and during exercise were studied in 30 patients with mild to moderate heart failure (13 patients in New York Heart Association class II; 17 in class III) due to ischemic (n = 24) or cardiomyopathic (n = 6) heart disease. Cardiac index, stroke volume and stroke work index at rest were significantly improved after i.v. administration of xamoterol and consistent with net agonist effects. During exercise, heart rate and double product were significantly reduced (net antagonist effects), but with preservation of the expected increases in cardiac index and systolic blood pressure. These hemodynamic findings confirm the ability of xamoterol to modulate cardiac response to variations in sympathetic tone. Tachyphylaxis and arrhythmogenicity limit the chronic use of drugs with full beta-agonist properties as positive inotropes in heart failure. The patients were therefore entered into a 6-month double-blind, placebo-controlled, crossover study of chronic oral xamoterol therapy, 200 mg twice daily, and the hemodynamic responses to i.v. xamoterol were repeated at the end of the trial. No impairment in either resting or exercise effects was observed, indicative of a maintained response and absence of tachyphylaxis after chronic therapy. Furthermore, 24-hour ambulatory electrocardiographic monitoring showed no change in ventricular arrhythmias during oral treatment.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
36.
37.
38.
L M Davies 《Health services management research》1988,1(3):145-155
There has been much debate in recent years about the implementation of community care policies for people with learning difficulties. The debate has centred on the following points: what the real costs and benefits of community care are, and to whom; what a community care service should look like; who should provide the service and how should it best be funded. This paper presents the results of a study comparing the costs and outcomes to clients of a variety of residential services for people with learning difficulties. The services evaluated range from traditional hospital services to small community based homes, run on 'ordinary life' principles. The purpose of the study was to collect information to aid policy makers and service providers in deciding how best to implement the community care initiative. 相似文献
39.
40.
A. Dornhorst M. Davies V. Anyaoku S. M. Hampton R. S. Elkeles R. W. Beard D. G. Johnston 《Clinical endocrinology》1991,34(3):211-213
Fasting plasma proinsulin, insulin and glucose concentrations were measured in ten women with mild gestational diabetes and ten controls matched for race, age (32 +/- 6 vs 31 +/- 6 years), body mass index (28 +/- 8 vs 27 +/- 6) and gestational week (24 +/- 4 vs 25 +/- 4 weeks). There was no significant difference in fasting plasma glucose between these gestational diabetics and their controls (median 4.7, range 3.7-6.0 mmol/l vs 4.5, range 3.4-5.3 mmol/l). The fasting proinsulin levels were significantly higher in the gestational diabetics compared with the controls (median 12.2, range less than 4-14.8 pmol/l vs 5.8, range less than 4-12.8 pmol/l, P less than or equal to 0.02, Wilcoxon Summed Rank Test), while the calculated intact insulin levels (immunoreactive insulin minus proinsulin) were significantly lower (median 14.5, range 6.3-81.8 pmol/l vs 51.6, range 11.7-312 pmol/l, P less than or equal to 0.01). The ratio of proinsulin to calculated intact insulin was significantly higher in the gestational diabetics than the controls (median 0.66, range 0.16-2.04 vs 0.12, range 0.03-0.62), P less than or equal to 0.01). These results demonstrate that gestational diabetics, with normal fasting plasma glucose values, have abnormalities in pancreatic beta-cell secretion, which are likely to be important both in the aetiology of gestational diabetes and non-insulin dependent diabetes. 相似文献