全文获取类型
收费全文 | 723536篇 |
免费 | 49797篇 |
国内免费 | 1359篇 |
专业分类
耳鼻咽喉 | 9453篇 |
儿科学 | 24215篇 |
妇产科学 | 18031篇 |
基础医学 | 111844篇 |
口腔科学 | 20251篇 |
临床医学 | 65128篇 |
内科学 | 138607篇 |
皮肤病学 | 16410篇 |
神经病学 | 50262篇 |
特种医学 | 26326篇 |
外国民族医学 | 76篇 |
外科学 | 107718篇 |
综合类 | 15199篇 |
现状与发展 | 2篇 |
一般理论 | 163篇 |
预防医学 | 52338篇 |
眼科学 | 17131篇 |
药学 | 55303篇 |
4篇 | |
中国医学 | 2423篇 |
肿瘤学 | 43808篇 |
出版年
2021年 | 6115篇 |
2019年 | 5945篇 |
2018年 | 8504篇 |
2017年 | 6536篇 |
2016年 | 7256篇 |
2015年 | 8005篇 |
2014年 | 10958篇 |
2013年 | 16248篇 |
2012年 | 21801篇 |
2011年 | 22663篇 |
2010年 | 13473篇 |
2009年 | 12505篇 |
2008年 | 20879篇 |
2007年 | 22391篇 |
2006年 | 22720篇 |
2005年 | 21216篇 |
2004年 | 20666篇 |
2003年 | 19535篇 |
2002年 | 18988篇 |
2001年 | 36683篇 |
2000年 | 37293篇 |
1999年 | 30706篇 |
1998年 | 8013篇 |
1997年 | 6782篇 |
1996年 | 7074篇 |
1995年 | 6723篇 |
1994年 | 6178篇 |
1992年 | 23177篇 |
1991年 | 23128篇 |
1990年 | 22492篇 |
1989年 | 22252篇 |
1988年 | 20180篇 |
1987年 | 19553篇 |
1986年 | 18592篇 |
1985年 | 17436篇 |
1984年 | 12820篇 |
1983年 | 10861篇 |
1982年 | 5975篇 |
1979年 | 11610篇 |
1978年 | 8197篇 |
1977年 | 6882篇 |
1976年 | 6632篇 |
1975年 | 7309篇 |
1974年 | 8553篇 |
1973年 | 8214篇 |
1972年 | 7735篇 |
1971年 | 7179篇 |
1970年 | 6918篇 |
1969年 | 6339篇 |
1968年 | 5811篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
R H Green C E Brightling S McKenna B Hargadon N Neale D Parker C Ruse I P Hall I D Pavord 《The European respiratory journal》2006,27(6):1144-1151
There is increasing evidence that the assessment of eosinophilic airway inflammation using induced sputum and measurement of airway hyperresponsiveness provides additional, clinically important information concerning asthma control. The aim of this study was to directly compare the effects of different treatments on these markers in patients with asthma and persistent symptoms, despite the use of low-dose inhaled corticosteroids. A double-blind four-way crossover study was performed, which compared a 1-month treatment with budesonide 400 mug b.i.d., additional formoterol, additional montelukast and placebo in 49 patients with uncontrolled asthma despite budesonide 100 mug b.i.d., with each treatment separated by a 4-week washout period. The change in sputum eosinophil count with formoterol (2.4 to 3.8% change, 0.6-fold reduction, 95% confidence interval (CI) 0.5-0.9) differed significantly from placebo (2.8 to 2.5% change, 1.1-fold reduction, 95% CI 0.7-1.6) and high-dose budesonide (2.7 to 1.6% change, 1.6-fold reduction, 95% CI 1.2-2.2). The effects of montelukast did not differ from placebo. The changes in methacholine airway responsiveness were small and did not differ between treatments. High-dose budesonide had the broadest range of beneficial effects on other outcomes, including symptom scores, morning peak expiratory flow and forced expiratory volume in one second. In conclusion, treatment given in addition to low-dose inhaled corticosteroids results in modest benefits. Formoterol and high-dose budesonide have contrasting effects on eosinophilic airway inflammation. 相似文献
92.
N B Pride 《The European respiratory journal》2006,27(1):240-1; author reply 241-2
93.
94.
95.
96.
S Aquilina† M Dalmas‡ N Calleja§ P Gatt† L Scerri† 《Journal of the European Academy of Dermatology and Venereology》2006,20(8):958-963
BACKGROUND: The incidence of malignant melanoma of the skin has risen in every part of the world where reliable cancer registration data are found. OBJECTIVE: Our study aims to describe the changing incidence of and survival from invasive cutaneous malignant melanoma in Malta, by analysing the data from the 211 cases that were registered at the Malta National Cancer Registry between 1993 and 2002. RESULTS: The age standardized incidence rates for invasive cutaneous malignant melanoma rose from 3.7 per 100,000 population per year for males and 5.1 for females in the first 5-year period, to 8.0 per 100,000 population per year for males and 5.9 for females in the second 5-year period. In both sexes, numbers of thin (< or = 1.0 mm) invasive melanomas increased significantly between 1993 and 2002; males also registered a significant increase in intermediate-thickness (1.01-4.0 mm) melanomas. The increase in numbers of thin and intermediate-thickness melanomas between the two 5-year periods was greatest in patients aged 60 years and over. The overall absolute 5-year survival rate for the first period was 74% and for the second period 92%. CONCLUSION: Numbers of reported cases of invasive cutaneous malignant melanoma in Malta have more than doubled during the 10-year study period. This is mostly due to a marked rise in the diagnosis of thin melanomas in both sexes, occurring mainly in patients aged 60 years and over. As thin melanomas are of low metastasizing potential, this has resulted in an increase in survival between the two 5-year study periods. 相似文献
97.
98.
99.
INTRODUCTION: The optimal hyperbaric oxygen (HBO2) treatment protocol for acute carbon monoxide (CO) poisoning is unknown. This is indicated by one study that found 18 different protocols to treat CO poisoning by North American multiplace hyperbaric facilities. A pilot study was conducted to evaluate the feasibility of randomizing patients to different protocols and to determine whether any large differences in clinical outcome were present between the two most common protocols. METHODS: Adult patients with accidental CO poisoning resulting in transient loss of consciousness, presentation to the emergency department within 12 hours, primary language English, high school education, and residence within 100 miles of the hyperbaric facility were recruited. Enrolled patients were randomized to one HBO2 treatment at 2.4 atmospheres absolute (atm abs) pressure with 90 minutes of 100% oxygen breathing vs. treatment by the US Air Force CO protocol (3.0 atm abs maximum pressure). A neurocognitive screening test was performed immediately after hyperbaric treatment and repeated 14-21 days later. RESULTS: From 1995 to 2002, 30 patients age 21 to 88 years were randomized, 18 to treatment at 2.4 atm abs and 12 to 3.0 atm abs. Average carboxyhemoglobin level for the population was 24.8 +/- 8.8% (mean +/- SD). Delay to hyperbaric treatment averaged 313 +/- 129 minutes. Neither variable was different between treatment groups. Six patients had abnormal neurocognitive testing immediately following hyperbaric treatment, 4 in the 2.4 atm abs group (22%) and 2 in the 3.0 atm abs group (17%) (P=0.71). One patient in each group demonstrated abnormality on delayed testing (p=0.75). One in each group did not return for follow-up. CONCLUSIONS: It is feasible to randomize CO-poisoned patients to different hyperbaric treatment protocols. Determination of differences in efficacy between treatment protocols will require a large multicenter trial with the use of detailed neurocognitive testing. 相似文献
100.
Sami S Zoghbi H Umesha Shetty Masanori Ichise Masahiro Fujita Masao Imaizumi Jeih-San Liow Jay Shah John L Musachio Victor W Pike Robert B Innis 《Journal of nuclear medicine》2006,47(3):520-527
18F-2beta-Carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nortropane (18F-FECNT), a PET radioligand for the dopamine transporter (DAT), generates a radiometabolite that enters the rat brain. The aims of this study were to characterize this radiometabolite and to determine whether a similar phenomenon occurs in human and nonhuman primate brains by examining the stability of the apparent distribution volume in DAT-rich (striatum) and DAT-poor (cerebellum) regions of the brain. METHODS: Two rats were infused with 18F-FECNT and sacrificed at 60 min. Extracts of brain and plasma were analyzed by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometric (LC-MS) techniques. Two human participants and 3 rhesus monkeys were injected with 18F-FECNT and scanned kinetically, with serial arterial blood analysis. RESULTS: At 60 min after the injection of rats, 18F-FECNT accumulated to levels about 7 times higher in the striatum than in the cortex and cerebellum. The radiometabolite was distributed at equal concentrations in all brain regions. The LC-MS techniques identified N-dealkylated FECNT as a major metabolite in the rat brain, and reverse-phase HPLC detected an equivalent amount of radiometabolite eluting with the void volume. The radiometabolite likely was 18F-fluoroacetaldehyde, the product expected from the N-dealkylation of 18F-FECNT, or its oxidation product, 18F-fluoroacetic acid. The distribution volume in the cerebellum increased up to 1.7-fold in humans between 60 and 300 min after injection and 2.0 +/- 0.1-fold (mean +/- SD; n = 3) in nonhuman primates between 60 and 240 min after injection. CONCLUSION: An 18F-fluoroalkyl metabolite of 18F-FECNT originating in the periphery confounded the measurements of DAT in the rat brain with a reference tissue model. Its uniform distribution across brain regions suggests that it has negligible affinity for DAT (i.e., it is an inactive radiometabolite). Consistent with the rodent data, the apparent distribution volume in the cerebellum of both humans and nonhuman primates showed a continual increase at late times after injection, a result that may be attributed to entry of the radiometabolite into the brain. Thus, reference tissue modeling of 18F-FECNT will be prone to more errors than analysis with a measured arterial input function. 相似文献