全文获取类型
收费全文 | 6193篇 |
免费 | 683篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 85篇 |
儿科学 | 259篇 |
妇产科学 | 117篇 |
基础医学 | 961篇 |
口腔科学 | 164篇 |
临床医学 | 837篇 |
内科学 | 1264篇 |
皮肤病学 | 80篇 |
神经病学 | 462篇 |
特种医学 | 234篇 |
外科学 | 663篇 |
综合类 | 160篇 |
一般理论 | 9篇 |
预防医学 | 728篇 |
眼科学 | 95篇 |
药学 | 365篇 |
中国医学 | 2篇 |
肿瘤学 | 411篇 |
出版年
2021年 | 77篇 |
2019年 | 72篇 |
2018年 | 99篇 |
2017年 | 72篇 |
2016年 | 72篇 |
2015年 | 78篇 |
2014年 | 106篇 |
2013年 | 150篇 |
2012年 | 202篇 |
2011年 | 233篇 |
2010年 | 113篇 |
2009年 | 138篇 |
2008年 | 179篇 |
2007年 | 244篇 |
2006年 | 241篇 |
2005年 | 205篇 |
2004年 | 206篇 |
2003年 | 225篇 |
2002年 | 223篇 |
2001年 | 240篇 |
2000年 | 192篇 |
1999年 | 181篇 |
1998年 | 91篇 |
1997年 | 83篇 |
1996年 | 73篇 |
1995年 | 77篇 |
1994年 | 81篇 |
1993年 | 78篇 |
1992年 | 162篇 |
1991年 | 186篇 |
1990年 | 153篇 |
1989年 | 165篇 |
1988年 | 168篇 |
1987年 | 155篇 |
1986年 | 146篇 |
1985年 | 134篇 |
1984年 | 101篇 |
1983年 | 91篇 |
1982年 | 76篇 |
1981年 | 77篇 |
1980年 | 72篇 |
1979年 | 86篇 |
1978年 | 79篇 |
1977年 | 83篇 |
1976年 | 81篇 |
1975年 | 70篇 |
1974年 | 76篇 |
1973年 | 74篇 |
1972年 | 73篇 |
1969年 | 67篇 |
排序方式: 共有6896条查询结果,搜索用时 0 毫秒
1.
Spleen sizing by ultrasound in polycythaemia and thrombocythaemia: comparison with SPECT 总被引:3,自引:1,他引:2
M. Messinezy L. M. MacDonald T. O. Nunan N. B. Westwood S. Chinn & T. C. Pearson 《British journal of haematology》1997,98(1):103-107
Detection of non-palpable early splenic enlargement may aid diagnosis of primary polycythaemia (PP) and primary thrombocythaemia (PT). In this study linear spleen sizing by ultrasound has been compared with spleen volume estimation by single photon emission computerized tomography (SPECT) in 26 patients. Spleen length by ultrasound correlated well with SPECT volume estimation.
Ultrasound spleen length was also measured in 60 normal control subjects where the upper limit of the 95% reference range was 11.6 cm. Changes in spleen length with both age and body weight were substantial and overshadowed the imperfect reproducibility of this method. Therefore, interpretation of an individual's measured spleen length should be in relation to that predicted for adults of the same age and weight, particularly at the extremes of the younger, heavier patients and also the older, lighter patients.
Ultrasound spleen lengths of different patient groups (21 PP, 26 PT, 17 idiopathic erythrocytosis, 12 secondary polycythaemia, nine apparent polycythaemia) were compared both using the measured overall reference range and the differences from the values predicted for their age and weight. The comparison showed that almost all patients with PP whose spleens were not palpable had spleen lengths greater than the upper limit for the normal control group, but separation from the other patient groups was incomplete.
Detection of non-palpable splenomegaly by ultrasound length should remain a 'minor' criterion amongst the 'proposed modified diagnostic criteria' of PP. 相似文献
Ultrasound spleen length was also measured in 60 normal control subjects where the upper limit of the 95% reference range was 11.6 cm. Changes in spleen length with both age and body weight were substantial and overshadowed the imperfect reproducibility of this method. Therefore, interpretation of an individual's measured spleen length should be in relation to that predicted for adults of the same age and weight, particularly at the extremes of the younger, heavier patients and also the older, lighter patients.
Ultrasound spleen lengths of different patient groups (21 PP, 26 PT, 17 idiopathic erythrocytosis, 12 secondary polycythaemia, nine apparent polycythaemia) were compared both using the measured overall reference range and the differences from the values predicted for their age and weight. The comparison showed that almost all patients with PP whose spleens were not palpable had spleen lengths greater than the upper limit for the normal control group, but separation from the other patient groups was incomplete.
Detection of non-palpable splenomegaly by ultrasound length should remain a 'minor' criterion amongst the 'proposed modified diagnostic criteria' of PP. 相似文献
2.
Lithium is a widely prescribed drug used for the treatment of bipolar affective illness. Previous reports on its effects on sperm motility and male fertility are conflicting. The effect of lithium on human sperm motility was examined in vitro using the modified transmembrane migration method. This technique takes account of the dilution of lithium that occurs during the incubation. Lithium inhibits human sperm motility in vitro in concentrations comparable with those reported to be achieved in semen after oral administration. 相似文献
3.
Data from the household portion of the 1977-78 USDA Nationwide Food Consumption Survey were used to determine expenditures for convenience and nonconvenience foods and nutrients from those foods. Households with male food preparers accounted for approximately 15% of the survey population, frequently included only one person, and had a larger proportion of young and elderly heads of household than households with a female food preparer. As a group, the foods most frequently reported in households with male food preparers were quite similar to those used by households with female food preparers. Male food preparers spent less of the food dollar on nonconvenience items than did other food preparers, and conversely they spent more on complex and manufactured convenience foods. Total food energy and nutrient levels per nutrition unit of the foods used by households with male food preparers were significantly higher than those in households with female food preparers for all nutrients except thiamin and riboflavin. However, the values were more than 100% of the Recommended Dietary Allowance values except for vitamin B-6 for both sample groups. 相似文献
4.
5.
Paul C. Ivancic Manohar M. Panjabi Yasuhiro Tominaga Adam M. Pearson S. Elena Gimenez Travis G. Maak 《European spine journal》2006,15(6):891-901
Between 23 and 70% of occupants involved in frontal impacts sustain cervical spine injuries, many with neurological involvement. It has been hypothesized that cervical spinal cord compression and injury may explain the variable neurological profile described by frontal impact victims. The goals of the present study, using a biofidelic whole cervical spine model with muscle force replication, were to quantify canal pinch diameter (CPD) narrowing during frontal impact and to evaluate the potential for cord compression. The biofidelic model and a sled apparatus were used to simulate frontal impacts at 4, 6, 8, and 10 g horizontal accelerations of the T1 vertebra. The CPD was measured in the intact specimen in the neutral posture (neutral posture CPD), under static sagittal pure moments of 1.5 Nm (pre-impact CPD), during dynamic frontal impact (dynamic impact CPD), and again under static pure moments following each impact (post-impact CPD). Frontal impact caused significant (P<0.05) dynamic CPD narrowing at C0-dens, C2-C3, and C6-C7. The narrowest dynamic CPD was observed at C0-dens during the 10 g impact and was 25.9% narrower than the corresponding neutral posture CPD. Interpretation of the present results indicate that the neurological symptomatology reported by frontal impact victims is most likely not due to cervical spinal cord compression. Cord compression due to residual spinal instability is also not likely. 相似文献
6.
Australian nursing has undergone rapid academization in the past 10 years and this radical change has tended to meld the somewhat different academic traditions of North America and Britain. The introduction of doctoral education in nursing in 1987 has led to a massive increase in scholarly activity and to the preparation of talented leaders. We concur with the view expressed by Henry (1997), "I am convinced that the problems we face in the nursing services would be much more creatively solved if the majority of our doctoral programs prepared young, energetic nurses, early in their career, for clinical practice, not for research and teaching" (p. 162). 相似文献
7.
D J Pearson J P Day V J Suarez-Mendez P F Miller S Owen A Woodcock 《European journal of clinical nutrition》1990,44(4):277-283
Nutritional selenium deficiency disease, due to low soil selenium content, is well recognized in British livestock. The adequacy of the selenium status of 25 healthy human volunteers, 50 blood donors, 94 general medical patients and 106 allergy clinic patients was investigated in 1987/8 by measuring serum selenium concentration and platelet glutathione peroxidase activity. Mean serum selenium concentration for the entire study population was 92 micrograms/l. Significant linear correlations between serum selenium concentration and peroxidase activity indicate that a substantial proportion of both healthy volunteers and medical patients are of low selenium nutritional status. Twenty-five per cent of healthy volunteers and 50 per cent of medical patients had serum selenium values below those required for full expression of selenium-dependent enzyme activity. Deficiency of the antioxidant activities of selenium and selenium-dependent enzymes may be relevant to geographical differences in morbidity from a wide range of human disease states. 相似文献
8.
9.
Action of calcitonin gene-related peptide upon bovine vascular endothelial and smooth muscle cells grown in isolation and co-culture. 总被引:3,自引:2,他引:1 下载免费PDF全文
D. C. Crossman M. R. Dashwood S. D. Brain J. McEwan J. D. Pearson 《British journal of pharmacology》1990,99(1):71-76
1. Bovine aortic endothelial cells (BAE) and smooth muscle cells (BASM) were grown separately and in co-culture. 2. Calcitonin gene-related peptide (CGRP) caused dose-dependent activation of adenylate cyclase in each cell type when grown in isolation. The concentration of CGRP causing half-maximal activation in BAE and BASM was 200 nM and 310 nM, respectively. 3. In cells grown in co-culture exposure to bradykinin produced dose-dependent elevations in cyclic GMP content which were maximal 1 min after application of the agonist. 4. CGRP (1 nM-1 microM) did not stimulate a rise in cyclic GMP in co-cultures. 5. Displaceable CGRP binding was identified throughout the wall of the bovine aorta. 6. We conclude that CGRP receptors coupled to adenylate cyclase are present on BAE and BASM, but there is no coupling of these receptors to the release of any agent (such as endothelium-derived relaxing factor) that activates guanylate cyclase. 相似文献
10.
F G Pearson 《The Journal of thoracic and cardiovascular surgery》1990,100(5):639-651