全文获取类型
收费全文 | 260150篇 |
免费 | 18844篇 |
国内免费 | 843篇 |
专业分类
耳鼻咽喉 | 2778篇 |
儿科学 | 7570篇 |
妇产科学 | 5688篇 |
基础医学 | 33345篇 |
口腔科学 | 5020篇 |
临床医学 | 28069篇 |
内科学 | 53196篇 |
皮肤病学 | 3464篇 |
神经病学 | 25133篇 |
特种医学 | 7817篇 |
外国民族医学 | 13篇 |
外科学 | 37000篇 |
综合类 | 3950篇 |
现状与发展 | 2篇 |
一般理论 | 397篇 |
预防医学 | 26261篇 |
眼科学 | 5067篇 |
药学 | 17677篇 |
1篇 | |
中国医学 | 435篇 |
肿瘤学 | 16954篇 |
出版年
2023年 | 1009篇 |
2022年 | 1280篇 |
2021年 | 4372篇 |
2020年 | 2756篇 |
2019年 | 4359篇 |
2018年 | 5087篇 |
2017年 | 4112篇 |
2016年 | 4410篇 |
2015年 | 5214篇 |
2014年 | 7663篇 |
2013年 | 11362篇 |
2012年 | 16725篇 |
2011年 | 18202篇 |
2010年 | 10271篇 |
2009年 | 9259篇 |
2008年 | 17087篇 |
2007年 | 18161篇 |
2006年 | 17504篇 |
2005年 | 18064篇 |
2004年 | 17372篇 |
2003年 | 16229篇 |
2002年 | 15477篇 |
2001年 | 2304篇 |
2000年 | 1772篇 |
1999年 | 2479篇 |
1998年 | 3440篇 |
1997年 | 2987篇 |
1996年 | 2631篇 |
1995年 | 2397篇 |
1994年 | 2144篇 |
1993年 | 1970篇 |
1992年 | 1430篇 |
1991年 | 1335篇 |
1990年 | 1222篇 |
1989年 | 1133篇 |
1988年 | 1179篇 |
1987年 | 1172篇 |
1986年 | 1147篇 |
1985年 | 1232篇 |
1984年 | 1655篇 |
1983年 | 1612篇 |
1982年 | 2011篇 |
1981年 | 1827篇 |
1980年 | 1702篇 |
1979年 | 899篇 |
1978年 | 1061篇 |
1977年 | 981篇 |
1976年 | 886篇 |
1975年 | 727篇 |
1974年 | 732篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
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
122.
Jean-Sébastien Fallu Jürgen Rehm Emmanuel N. Kuntsche Esther Grichting Neerav Monga Edward M. Adlaf Susan J Bondy Gerhard Gmel 《Sozial- und Pr?ventivmedizin》2006,8(1):363-372
Volume and profile of alcohol consumption among students and classmates as predictors of aggression and victimization: a multilevel
analysis among Swiss adolescents
Objective:
To test the effects of the volume of alcohol consumption and drinking patterns on alcohol-related aggression and victimization, both at the individual and class levels. 相似文献123.
PURPOSE: The variable-pitch pulse oximeter is an important intraoperative patient monitor. Our ability to hear its auditory signal depends on its acoustical properties and our hearing. This study quantitatively describes the audio spectrum and sound pressure levels of the monitoring tones produced by five variable-pitch pulse oximeters. METHODS: We compared the Datex-Ohmeda Capnomac Ultima, Hewlett-Packard M1166A, Datex-Engstrom AS/3, Ohmeda Biox 3700, and Datex-Ohmeda 3800 oximeters. Three machines of each of the five models were assessed for sound pressure levels (using a precision sound level meter) and audio spectrum (using a hanning windowed fast Fourier trans-form of three beats at saturations of 99%, 90%, and 85%). RESULTS: The widest range of sound pressure levels was produced by the Hewlett-Packard M1166A (46.5 +/- 1.74 dB to 76.9 +/- 2.77 dB). The loudest model was the Datex-Engstrom AS/3 (89.2 +/- 5.36 dB). Three oximeters, when set to the lower ranges of their volume settings, were indistinguishable from background operating room noise. Each model produced sounds with different audio spectra. Although each model produced a fundamental tone with multiple harmonic overtones, the number of harmonics varied with each model; from three harmonic tones on the Hewlett-Packard M1166A, to 12 on the Ohmeda Biox 3700. There were variations between models, and individual machines of the same model with respect to the fundamental tone associated with a given saturation. CONCLUSION: There is considerable variance in the sound pressure and audio spectrum of commercially-available pulse oximeters. Further studies are warranted in order to establish standards. 相似文献
124.
The patient with an implantable cardioverter defibrillator 总被引:1,自引:0,他引:1
Electrophysiologic technology developed over the past 20 years has improved the life expectancy of patients who have survived sudden cardiac death events. Use of an implantable cardioverter defibrillator (ICD) continues to increase as more indications for the device are researched. Patients with ICDs will be cared for in the postanesthesia care unit following cardiac and noncardiac surgery and require PACU nurses to be knowledgeable about this advanced and changing technology as well as provide for emotional and psychological needs. 相似文献
125.
OBJECTIVE: This study employed EEG source localisation procedures to study the contribution of motor preparatory and attentional processing to foreperiod activity in an S1-S2 motor priming task. METHODS: Behavioural and high-density event-related potential (ERP) data were recorded in an S1-S2 priming task where participants responded to S2 with a left or right-hand button press. S1 either provided information about response hand (informative) or ambiguous information (uninformative). RESULTS: Responses were significantly faster in informative trials compared with uninformative trials. Dipole source analysis of foreperiod lateralized ERPs revealed sources of motor preparatory activity in the dorsolateral premotor cortex (PMd) in line with previous work. In addition, two spatial attention components (ADAN, LDAP) were identified with generators in the PMd and occipitotemporal visual areas in the middle temporal (MT) region, respectively. Separation of motor-related and attentional PMd source locations was reliable along the rostral-caudal axis. CONCLUSIONS: The presence of attentional components in a motor priming paradigm supports the premotor theory of attention which suggests a close link between attention and motor preparatory processes. Separation of components in the premotor cortex is in accord with a functional division of PMd into rostral (higher-order processing) and caudal (motor-related processing) areas as suggested by imaging work. SIGNIFICANCE: A prime for response preparation is a trigger for separate, but closely linked, attention-related activity in premotor areas. 相似文献
126.
127.
128.
129.
130.
Dr. Menon Raj Gopal M.Ch. AlDelamie Taha FRCS Valliathu John FRCS Zacharias Sunny FRCS Lawati Al Adil FRCS Venkatraman M.Ch. 《Indian Journal of Thoracic and Cardiovascular Surgery》2006,22(3):173-177
Background Despite improving surgical techniques, treatment of heart valve disease in children remains controversial. Somatic growth
and adequate anticoagulation are of concern when children undergo valve replacement. We conducted this study to evaluate the
performance of valves in this age group.
Methods 42 children under the age of 13 years who underwent valve replacement were included in this study. Totally, 50 valves were
implanted in 42 patients: 48 were mechanical prostheses, two were bioprosthetic both in pulmonary position. 37 (74%) valves
were implanted in mitral position, 10 (20%) in aortic position, 1 (2%) in tricuspid position and 2 (4%) in pulmonary position.
Preoperatively, 14 (33,3%) patients were in New York Heart Association (NYHA) class IV, while 27 (64.2%) were in NYHA class
III.
Results There were 2 (4.7%) hospital deaths and 2 (4.7%) late deaths while 2 (4.7%) patients were lost to follow up. The mean follow
up period was 9.4 yrs. 35 (83.3%) patients are in NYHA Class I and free of all medications except warfarin. 3 (7.1%) patients
have undergone 5 successful pregnancies. The median INR was 2.23. Major thrombo-embolic episode occurred in 1 (2.3%) patient.
Conclusions In view of the problems of sizing, anticoagulation and need for re-operation at an early age, there is a reluctance to replace
valves in children. This study shows that despite these problems, valve replacement can be undertaken safely and successfully
in children, when repair has failed or not technically feasible. 相似文献