全文获取类型
收费全文 | 1454篇 |
免费 | 78篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 7篇 |
儿科学 | 109篇 |
妇产科学 | 33篇 |
基础医学 | 89篇 |
口腔科学 | 13篇 |
临床医学 | 168篇 |
内科学 | 338篇 |
皮肤病学 | 10篇 |
神经病学 | 122篇 |
特种医学 | 58篇 |
外科学 | 172篇 |
综合类 | 73篇 |
预防医学 | 135篇 |
眼科学 | 15篇 |
药学 | 102篇 |
中国医学 | 39篇 |
肿瘤学 | 61篇 |
出版年
2023年 | 9篇 |
2021年 | 10篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 12篇 |
2017年 | 15篇 |
2016年 | 18篇 |
2015年 | 27篇 |
2014年 | 28篇 |
2013年 | 36篇 |
2012年 | 52篇 |
2011年 | 131篇 |
2010年 | 54篇 |
2009年 | 47篇 |
2008年 | 73篇 |
2007年 | 66篇 |
2006年 | 74篇 |
2005年 | 65篇 |
2004年 | 109篇 |
2003年 | 94篇 |
2002年 | 67篇 |
2001年 | 60篇 |
2000年 | 57篇 |
1999年 | 37篇 |
1998年 | 21篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1994年 | 12篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1976年 | 15篇 |
1975年 | 10篇 |
1974年 | 11篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1969年 | 7篇 |
1967年 | 8篇 |
1966年 | 7篇 |
排序方式: 共有1544条查询结果,搜索用时 15 毫秒
71.
“True agonadism”: A misnomer? 总被引:1,自引:0,他引:1
G A Parks K W Dumars G A Limbeck W L Quinlivan M I New 《The Journal of pediatrics》1974,84(3):375-380
72.
Mark Garton James Martin Susan New Sue Lee Nigel Loveridge John Milne David Reid Ivan Reid Simon Robins 《Clinical endocrinology》1996,44(5):563-570
OBJECTIVE Changes in calcium homeostasis and bone mass around the climacteric are poorly understood. We examined relations between endocrine factors and indices of bone mass and metabolism in healthy women approaching the menopause. DESIGN Cross-section study. PATIENTS Sixty-eight spontaneously menstruating women aged 45–55. MEASUREMENTS Bone density measured at lumbar spine (LS) and femoral neck (FN) using dual energy X-ray absorptiometry and distal non-dominant forearm using peripheral quantitative computed tomography. We recorded menstrual history, physical activity and dietary calcium, and measured serum calcium, phosphate, alkaline phosphatase, osteocalcin, vitamin D, fT3, T4, TSH, PTH, FSH and oestradiol (E2), and urinary pyridinoline (PYD) and deoxypyridinoline (DPD) excretion. RESULTS Using serum FSH level as a marker of ovarian function, 63 subjects could be classified into one of three groups: group A (serum FSH <10 U/l, n = 29), group B (10–35 U/l, n = 27) and group C (>35 U/l, n = 7). Bone density fell with declining ovarian function at the LS, FN and forearm trabecular (but not cortical) sites. Serum PTH was lower in group A vs B (mean (SD) 2.68 (0.97) vs 3.52 (1.17) pmol/l, P < 0.05), but similar to group C (2.90 (1.09) pmol/l, P = NS). Serum phosphate was elevated in group C compared to groups A and B (1.17 (0.15) vs 1.04 (0.11) and 1.05 (0.13) mmol/l, P < 0.05), and urinary PYD (61.1 (8.0) vs 50.4 (11.6) and 43.9 (8.1) μmol/mol creatinine) and DPD (15.9 (3.9) vs 12.0 (3.6) and 11.4 (3.6) μmol/mol creatinine) excretion were also increased. There were no significant differences in vitamin D metabolites or osteocalcin. Multivariate analysis suggested serum osteocalcin was positively related to physical activity and serum 1,25-dihydroxycholecalciferol levels. Serum free T3 was positively correlated with urinary DPD excretion, and inversely related to serum PTH. In all subjects, serum PTH was related to body weight (r = 0.38, P = 0.002). CONCLUSIONS Declining ovarian function before menopause is accompanied by reductions in bone mass and altered calcium metabolism. Free T3 may regulate bone resorption and indirectly modulate PTH release. 相似文献
73.
74.
75.
Visualization of orbital soft tissue structures by computed tomography in direct coronal and axial studies is extremely useful in diagnosis. Direct enlargement viewing of scans has disclosed minute anatomical details. This study reviews some of our experiences in the investigation of a variety of lesions within the orbit and attempts, in particular, to illustrate the value of direct coronal studies. 相似文献
76.
77.
P F New T B Bachow G L Wismer B R Rosen T J Brady 《AJR. American journal of roentgenology》1985,144(5):1021-1026
To evaluate the capability of magnetic resonance (MR) in imaging normal acoustic nerves, 12 volunteers without signs or symptoms of intracranial disease were examined using a 0.6 T superconductive system. Several spin-echo (SE) pulse sequences were tested to identify the optimal sequence for demonstration of the acoustic nerve bundle. Repetition times (TRs) varied from 300 to 2000 msec and echo times (TEs) from 30 to 120 msec. A single-slice technique was used with 5 and 8 mm sections, one or two data acquisitions per projection, and axial and coronal imaging. The normal acoustic nerves were demonstrated readily by MR in axial and/or coronal sections. The distal parts of the nerves and tumors were imaged best with SE 1500/60. The medial extremities of the seventh and eighth nerves tended to be obscured in this sequence by brightening the cerebrospinal fluid signal adjacent to the brainstem, but they were demonstrated clearly with 500 or 800 msec TR and 30 msec TE. Five patients were studied who had hearing loss and evidence of retrocochlear disease. In four patients, MR imaging demonstrated five acoustic nerve tumors ranging in size from purely intracanalicular to a 12 mm cisternal component. In the fifth case, no tumor was identified by MR imaging or gas computed tomographic (CT) cisternography. Contrast-enhanced CT using a Siemens Somatom DR 3 or GE CT/T 8800 scanner failed to provide convincing evidence of tumor in any case, while gas CT cisternography was positive in all five tumors. All five acoustic neuromas were identified readily using the SE sequences that proved optimal for demonstration of normal nerves. This experience revealed that MR imaging can demonstrate the eighth nerve complex well and reliably. Single-slice (5 or 8 mm) technique is adequate, but multislice without tissue gaps (used recently) is more efficient. Small, even intracanalicular, acoustic neuromas are imaged effectively, indicating that the method is capable of superseding contrast CT cisternography, particularly with improving technology. 相似文献
78.
Kellie SJ Chaku J Lockwood LR O'Regan P Waters KD Wong CK;Australian New Zealand Children's Haematology Oncology Group 《European journal of cancer (Oxford, England : 1990)》2005,41(11):1588-1596
High-dose methotrexate (HDMTX) is used increasingly to treat children with central nervous system (CNS) tumours. Although the neuro-imaging features of leukoencephalopathy associated with systemic or intrathecal methotrexate administered after cranial radiation have been well described, the extent to which the sequencing of HDMTX prior to cranial radiation in infants and children predisposes to late neuroradiological features of leukoencephalopathy is unknown. This report describes the National Cancer Institute (NCI) toxicity grade of leukoencephalopathy based on magnetic resonance imaging (MRI) findings in all patients who survived 4 or more years after treatment on an earlier phase II study. These patients, with newly diagnosed CNS embryonal tumours, were in the age range 3.5-14.2 years (median 6.9 years) at diagnosis, and received four courses of pre-irradiation combination chemotherapy, including HDMTX 8 g/m(2). Following completion of the 'up-front' phase II study, all patients received conventionally fractionated whole brain doses of 36-50.4 Gy. The radiation dose and treatment volumes were determined individually according to the primary tumour location and results of extent of disease evaluations. The most recent MRI brain scans, obtained 4.0-10.5 years (median 6.5 years) after radiation therapy and comprising a minimum of T1, T1 following gadolinium and T2 sequences, were reviewed centrally to assess the neuroradiological grade of leukoencephalopathy, based on the NCI Common Terminology Criteria for Adverse Events, v3.0. Grade I changes (mild increase in subarachnoid space, and/or mild ventriculomegaly, and/or small/focal T2 hyperintensities) were evident in 8 of the 12 patients and grade II changes (moderate increase in subarachnoid space and/or moderate ventriculomegaly, and/or focal T2 hyperintensities extending to the centrum ovale) were found in the remaining 4. In conclusion, treatment with multiple courses of HDMTX prior to 36-50.4 Gy cranial radiation did not result in moderate to severe MRI features of leukoencephalopathy. Future studies in paediatric neuro-oncology patients, involving HDMTX combined with prospective neuropsychological evaluations appear justified. 相似文献
79.
Helen M. Macdonald Susan A. New Marion K. Campbell David M. Reid 《Osteoporosis international》2005,16(2):163-171
Weight is recognized as an important factor in determining an individuals risk of osteoporosis. However, little is known about whether weight or weight change influences bone loss around the time of the menopause, and the relationship with energy intake and physical activity level remains largely undefined. Healthy premenopausal women (1,064 selected from a random population of 5,119 women aged 45–54 years at baseline) each had bone mineral density (BMD), weight and height measurements, and completed a food frequency and physical activity questionnaire. Of the original participants, 907 women (85.2%) returned 6.3 ± 0.6 years later for repeat BMD measurements, and 896 women completed the questionnaires. Bone loss at the hip (FN) and spine (LS) occurred before the menopause. Weight change rather than weight was associated with FN BMD loss (r=0.102, p=0.002), but weight at follow-up was associated with LS BMD change (r=0.105, p=0.002). Although an increase in physical activity level (PAL) appeared to be beneficial for FN BMD in women who were heavy weight gainers, PAL was associated with increased LS BMD loss in women who lost weight. For current HRT users, neither weight nor weight change was associated with change in BMD. Postmenopausal women not taking HRT should be made aware that low body weight or losing weight during this particularly vulnerable period may worsen bone loss. 相似文献
80.