全文获取类型
收费全文 | 107332篇 |
免费 | 6766篇 |
国内免费 | 472篇 |
专业分类
耳鼻咽喉 | 1191篇 |
儿科学 | 2718篇 |
妇产科学 | 1932篇 |
基础医学 | 13329篇 |
口腔科学 | 1886篇 |
临床医学 | 11159篇 |
内科学 | 22062篇 |
皮肤病学 | 1486篇 |
神经病学 | 10837篇 |
特种医学 | 4061篇 |
外国民族医学 | 3篇 |
外科学 | 17361篇 |
综合类 | 1103篇 |
一般理论 | 131篇 |
预防医学 | 8542篇 |
眼科学 | 2163篇 |
药学 | 6864篇 |
中国医学 | 114篇 |
肿瘤学 | 7628篇 |
出版年
2023年 | 625篇 |
2022年 | 1026篇 |
2021年 | 2293篇 |
2020年 | 1427篇 |
2019年 | 2250篇 |
2018年 | 2715篇 |
2017年 | 1956篇 |
2016年 | 2159篇 |
2015年 | 2435篇 |
2014年 | 3649篇 |
2013年 | 4999篇 |
2012年 | 7950篇 |
2011年 | 8336篇 |
2010年 | 4812篇 |
2009年 | 4322篇 |
2008年 | 7472篇 |
2007年 | 7822篇 |
2006年 | 7542篇 |
2005年 | 7241篇 |
2004年 | 7038篇 |
2003年 | 6317篇 |
2002年 | 5955篇 |
2001年 | 1074篇 |
2000年 | 811篇 |
1999年 | 1077篇 |
1998年 | 1286篇 |
1997年 | 991篇 |
1996年 | 822篇 |
1995年 | 736篇 |
1994年 | 636篇 |
1993年 | 613篇 |
1992年 | 568篇 |
1991年 | 515篇 |
1990年 | 423篇 |
1989年 | 383篇 |
1988年 | 359篇 |
1987年 | 358篇 |
1986年 | 309篇 |
1985年 | 342篇 |
1984年 | 383篇 |
1983年 | 298篇 |
1982年 | 365篇 |
1981年 | 309篇 |
1980年 | 245篇 |
1979年 | 134篇 |
1978年 | 155篇 |
1977年 | 120篇 |
1976年 | 107篇 |
1975年 | 80篇 |
1973年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
In cystic fibrosis (CF), perturbations of total daily energy expenditure (TDEE) may be a major determinant of altered nutrition and growth. Measurement of TDEE is problematic, though the flex-heart rate method (FHRM) provides a close estimation of TDEE, as compared to the cost-prohibitive, gold standard, the double-labeled water method, and permits estimates of the energy cost of daily activities (ECA) above resting energy expenditure (REE). We hypothesize that alterations in ECA affects TDEE in CF. PURPOSE: To measure components of TDEE in adolescents with CF and normal lung function compared with controls, and to determine whether ECA can be improved by diet and exercise. METHODS: Clinically stable CF subjects (aged 9-13, n=12) and age- and gender-matched controls (n=13) had repeated measurements of TDEE by FHRM, REE, and maximal cardiopulmonary exercise testing (CPET) during a 6-week exercise and diet program. RESULTS: While the mean REE was similar in both groups, ECA was significantly lower in CF adolescents as compared to controls (p=0.02). During CPET, maximal exercise in CF was characterized by hyperventilation, which was unrelated to ventilation-perfusion mismatching. There were no changes in REE after dietary intervention. CONCLUSION: ECA in CF adolescents with normal lung function is lower when compared to healthy controls. These findings support the hypothesis that clinically stable patients with CF have inefficient energy metabolism or alternatively conserve energy during activities of daily living. 相似文献
54.
Mark W Woolrich Peter Chiarelli Daniel Gallichan Joanna Perthen Thomas T Liu 《Magnetic resonance in medicine》2006,56(4):891-906
The study of brain function using MRI relies on acquisition techniques that are sensitive to different aspects of the hemodynamic response contiguous to areas of neuronal activity. For this purpose different contrasts such as arterial spin labeling (ASL) and blood oxygenation level dependent (BOLD) functional MRI techniques have been developed to investigate cerebral blood flow (CBF) and blood oxygenation, respectively. Analysis of such data typically proceeds by separate, linear modeling of the appropriate CBF or BOLD time courses. In this work an approach is developed that provides simultaneous inference on hemodynamic changes via a nonlinear physiological model of ASL data acquired at multiple echo times. Importantly, this includes a significant contribution by changes in the static magnetization, M, to the ASL signal. Inference is carried out in a Bayesian framework. This is able to extract, from dual-echo ASL data, probabilistic estimates of percentage changes of CBF, R(2) (*), and the static magnetization, M. This approach provides increased sensitivity in inferring CBF changes and reduced contamination in inferring BOLD changes when compared with general linear model approaches on single-echo ASL data. We also consider how the static magnetization, M, might be related to changes in CBV by assuming the same mechanism for water exchange as in vascular space occupancy. 相似文献
55.
56.
Marlene L Hauck Susan M LaRue William P Petros Jean M Poulson Daohai Yu Ivan Spasojevic Amy F Pruitt Allison Klein Beth Case Donald E Thrall David Needham Mark W Dewhirst 《Clinical cancer research》2006,12(13):4004-4010
PURPOSE: To determine the maximum tolerated dose, dose-limiting toxicities, and pharmacokinetic characteristics of doxorubicin encapsulated in a low temperature sensitive liposome (LTSL) when given concurrently with local hyperthermia to canine solid tumors. EXPERIMENTAL DESIGN: Privately owned dogs with solid tumors (carcinomas or sarcomas) were treated. The tumors did not involve bone and were located at sites amenable to local hyperthermia. LTSL-doxorubicin was given (0.7-1.0 mg/kg i.v.) over 30 minutes during local tumor hyperthermia in a standard phase I dose escalation study. Three treatments, given 3 weeks apart, were scheduled. Toxicity was monitored for an additional month. Pharmacokinetics were evaluated during the first treatment cycle. RESULTS: Twenty-one patients were enrolled: 18 with sarcomas and 3 with carcinomas. Grade 4 neutropenia and acute death secondary to liver failure, possibly drug related, were the dose-limiting toxicities. The maximum tolerated dose was 0.93 mg/kg. Other toxicities, with the possible exception of renal damage, were consistent with those observed following free doxorubicin administration. Of the 20 dogs that received > or = 2 doses of LTSL-doxorubicin, 12 had stable disease, and 6 had a partial response to treatment. Pharmacokinetic variables were more similar to those of free doxorubicin than the marketed liposomal product. Tumor drug concentrations at a dose of 1.0 mg/kg averaged 9.12 +/- 6.17 ng/mg tissue. CONCLUSION: LTSL-doxorubicin offers a novel approach to improving drug delivery to solid tumors. It was well tolerated and resulted in favorable response profiles in these patients. Additional evaluation in human patients is warranted. 相似文献
57.
58.
Christine E. Marx William T. Trost Lawrence J. Shampine Robert D. Stevens Christine M. Hulette David C. Steffens John F. Ervin Marian I. Butterfield Daniel G. Blazer Mark W. Massing Jeffrey A. Lieberman 《Neuropsychopharmacology》2006,60(12):1287-1294
BACKGROUND: Few data are currently available investigating neurosteroids (NS) in Alzheimer's disease (AD). The NS allopregnanolone may be decreased in serum and plasma in patients with AD, but it is unclear if allopregnanolone is also reduced in brain. Because a number of NS exhibit neuroprotective effects and impact cognitive performance in rodent models, these molecules may be relevant to the pathophysiology of neurodegenerative disorders. We therefore investigated prefrontal cortex (PFC) NS levels in AD. METHODS: Neurosteroid levels (allopregnanolone, pregnenolone, dehydroepiandrosterone [DHEA]) were determined in postmortem PFC in 14 male subjects with AD and 15 cognitively intact male control subjects by gas chromatography/mass spectrometry preceded by high-performance liquid chromatography purification. RESULTS: Subjects with AD exhibit significant reductions in allopregnanolone compared with cognitively intact control subjects (median levels = 2.50 ng/g vs. 5.59 ng/g, respectively; p = .02). Allopregnanolone levels are inversely correlated with neuropathological disease stage (Braak), r = -.49, p = .007. Median DHEA levels are elevated in subjects with AD (p = .01). CONCLUSIONS: Subjects with AD demonstrate significant reductions in PFC allopregnanolone levels, a finding that may be relevant to neuropathological disease stage severity. Neurosteroids may have utility as candidate biomarkers in AD. 相似文献
59.
Michele D. Mignogna Stefano Fedele Lucio Lo Russo Lorenzo Lo Muzio 《Journal of oral pathology & medicine》2003,32(4):200-205
BACKGROUND: The recurrent chronic orofacial swelling caused by orofacial granulomatosis (OFG) can cause significant cosmetic and functional problems but can be prevented if the disease is diagnosed early and promptly treated. Although the enlargement of the lips is described to be the most common presenting complaint, the clinical onset of OFG may be characterized by minor associated mucosal and neurological manifestations, making early diagnosis very difficult or, sometimes, merely presumable. PATIENTS AND METHODS: We retrospectively analyzed the clinical manifestations of 19 patients with OFG, who were examined at our institution between 1998 and 2002, in order to determine their initial manifestations and presenting symptoms. RESULTS: A total of 10 patients showed classical recurrent enlargement of the lips (six lower; four upper) as presenting symptom. In the other nine patients, OFG onset was characterized by transient unilateral facial nerve palsy (two cases), intraoral manifestations (two cases), recurrent swelling of the periorbital area (two cases), of the chin (one case), of the zygomatic area (one case), and of the cheeks (one case). CONCLUSION: Our data underlined that OFG onset could be frequently characterized by widely variable, multiform, and temporary clinical findings. Involvement of atypical sites of the orofacial region and presence of single minor manifestations may occur as presenting symptoms, often preceding the development of traditional clinical findings. 相似文献
60.
Mark Kantor PhD 《Journal of nutrition education and behavior》2006,38(1):349-69