全文获取类型
收费全文 | 128953篇 |
免费 | 9792篇 |
国内免费 | 222篇 |
专业分类
耳鼻咽喉 | 1194篇 |
儿科学 | 3586篇 |
妇产科学 | 2728篇 |
基础医学 | 20304篇 |
口腔科学 | 3382篇 |
临床医学 | 10992篇 |
内科学 | 25981篇 |
皮肤病学 | 2244篇 |
神经病学 | 12499篇 |
特种医学 | 5304篇 |
外国民族医学 | 16篇 |
外科学 | 16117篇 |
综合类 | 539篇 |
现状与发展 | 1篇 |
一般理论 | 108篇 |
预防医学 | 14729篇 |
眼科学 | 2018篇 |
药学 | 7837篇 |
中国医学 | 238篇 |
肿瘤学 | 9150篇 |
出版年
2023年 | 516篇 |
2022年 | 425篇 |
2021年 | 1845篇 |
2020年 | 1468篇 |
2019年 | 2137篇 |
2018年 | 2682篇 |
2017年 | 2285篇 |
2016年 | 2457篇 |
2015年 | 2775篇 |
2014年 | 3772篇 |
2013年 | 4975篇 |
2012年 | 7660篇 |
2011年 | 7712篇 |
2010年 | 3978篇 |
2009年 | 4209篇 |
2008年 | 6838篇 |
2007年 | 7036篇 |
2006年 | 6807篇 |
2005年 | 6448篇 |
2004年 | 5470篇 |
2003年 | 5198篇 |
2002年 | 4723篇 |
2001年 | 4558篇 |
2000年 | 4563篇 |
1999年 | 4030篇 |
1998年 | 1526篇 |
1997年 | 1241篇 |
1996年 | 1314篇 |
1995年 | 1183篇 |
1994年 | 1095篇 |
1993年 | 995篇 |
1992年 | 2773篇 |
1991年 | 2509篇 |
1990年 | 2396篇 |
1989年 | 2226篇 |
1988年 | 2035篇 |
1987年 | 1792篇 |
1986年 | 1707篇 |
1985年 | 1633篇 |
1984年 | 1164篇 |
1983年 | 1004篇 |
1982年 | 537篇 |
1981年 | 473篇 |
1980年 | 408篇 |
1979年 | 885篇 |
1978年 | 534篇 |
1977年 | 439篇 |
1974年 | 444篇 |
1973年 | 432篇 |
1972年 | 384篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
de Haan S Harms HJ Lubberink M Allaart CP Danad I Chen WJ Diamant M van Rossum AC Iida H Lammertsma AA Knaapen P 《European journal of nuclear medicine and molecular imaging》2012,39(8):1240-1245
Purpose
The perfusable tissue index (PTI) is a marker of myocardial viability. Recent technological advances have made it possible to generate parametric PTI images from a single [15O]H2O PET/CT scan. The purpose of this study was to validate these parametric PTI images.Methods
The study population comprised 46 patients with documented or suspected coronary artery disease who were studied with [15O]H2O PET and late gadolinium-enhanced (LGE) cardiac magnetic resonance imaging (CMR).Results
Of the 736 myocardial segments included, 364 showed some degree of LGE. PTI and perfusable tissue fraction (PTF) diminished with increasing LGE. The areas under the curve of the PTI and PTF, used to predict (near) transmural LGE on CMR, were 0.86 and 0.87, respectively. Optimal sensitivity and specificity were 91?% and 73?% for PTI and 69?% and 87?% for PTF, respectively.Conclusion
PTI and PTF assessed with a single [15O]H2O scan can be utilized as markers of myocardial viability in patients with coronary artery disease. 相似文献994.
Improved anatomic visualization of a glomus caroticum tumour within the carotic bifurcation with combined 68Ga-DOTATATE PET/MRI 总被引:1,自引:0,他引:1
995.
MATTIE G.C. PIETERSE KAREL den DULK BERRY M. van GELDER ROB van MECHELEN HEIN J.J. WELLENS 《Pacing and clinical electrophysiology : PACE》1994,17(2):252-257
In patients with intermittent AV block and dual chamber pacemakers, a long paced AV interval of 200 msec or more can be selected to prolong pulse generator life (by avoiding the ventricular pace output) and to enable a more physiological and hemodynamically superior activation sequence. This case report describes the potential risks of programming a long paced AV interval in a patient with a DDDR pacemaker. T wave pacing, as described here, can occur if the conducted QRS complex is not sensed because it occurs during the ventricular blanking period (delivery of the atrial stimulus). This can be initiated by the mechanisms that induce apparent and actual P wave undersensing of the conducted QRS complex. In this case report apparent P wave undersensing and subsequent T wave pacing with ventricular capture (in a patient with intermittent AV block) occurred frequently during an exercise test done in the DDDR mode with a paced AV interval of 200 msec, according to the clinical evaluation protocol. 相似文献
996.
Changes in oscillatory brain dynamics can be studied by means of induced band power (IBP) analyses, which quantify event-related changes in amplitude of frequency-specific EEG rhythms. Such analyses capture EEG phenomena that are not part of traditional event-related potential measures. The present study investigated whether IBP changes in the delta, theta, and alpha frequency ranges are sensitive to syntactic violations in sentences. Subjects read sentences that either were correct or contained a syntactic violation. The violations were either grammatical gender agreement violations, where a prenominal adjective was not appropriately inflected for the head noun's gender, or number agreement violations, in which a plural quantifier was combined with a singular head noun. IBP changes of the concurrently measured EEG were computed in five frequency bands of 2-Hz width, individually adjusted on the basis of subjects' alpha peak, ranging approximately from 2 to 12 Hz. Words constituting a syntactic violation elicited larger increases in theta power than the same words in a correct sentence context, in an interval of 300-500 ms after word onset. Of all the frequency bands studied, this was true for the theta frequency band only. The scalp topography of this effect was different for different violations: following number violations a left-hemispheric dominance was found, whereas gender violations elicited a right-hemisphere dominance of the theta power increase. Possible interpretations of this effect are considered in closing. 相似文献
997.
Acute psychological stress can trigger normal and abnormal motivated behaviors such as reward seeking, habitual behavior, and drug craving. Animal research suggests that such effects may result from actions of catecholamines and glucocorticoids that converge in brain regions that regulate motivated behaviors and incentive processing. At present, however, little is known about the acute effects of stress on these circuits in humans. During functional magnetic resonance imaging (fMRI), twenty-seven healthy young women performed a modified version of the monetary incentive delay (MID) task, which is known to robustly engage ventral striatal and medial prefrontal regions. To induce psychological stress, strongly aversive movie clips (versus neutral movie clips) were shown with the instruction to imagine being an eyewitness. Physiological (cortisol levels, heart rate frequency, and heart rate variability) and subjective measurements confirmed successful induction of moderate levels of acute psychological stress. Brain imaging data revealed that stress induction resulted in a significant decrease in reward-related responses in the medial prefrontal cortex (PFC) without affecting ventral striatal responses. Our results thus show that acute psychological stress induces regionally specific changes in functioning of incentive processing circuits. This regional specificity is in line with animal data showing inverted U-shaped relations between levels of stress-related neuromodulators and functioning of the PFC, a structure that is believed to be critical for coordinating behavior in accordance with higher order internal goals. Our findings thus suggest that stress-related increases in habitual and reward-seeking behaviors may be triggered primarily by an impairment of such PFC-dependent cognitive control mechanisms. 相似文献
998.
999.
Kam BL Teunissen JJ Krenning EP de Herder WW Khan S van Vliet EI Kwekkeboom DJ 《European journal of nuclear medicine and molecular imaging》2012,39(Z1):S103-S112
Treatment with radiolabelled somatostatin analogues is a promising new tool in the management of patients with inoperable or metastasized neuroendocrine tumours. Symptomatic improvement may occur with (177)Lu-labelled somatostatin analogues that have been used for peptide receptor radionuclide therapy (PRRT). The results obtained with (177)Lu-[DOTA(0),Tyr(3)]octreotate (DOTATATE) are very encouraging in terms of tumour regression. Dosimetry studies with (177)Lu-DOTATATE as well as the limited side effects with additional cycles of (177)Lu-DOTATATE suggest that more cycles of (177)Lu-DOTATATE can be safely given. Also, if kidney-protective agents are used, the side effects of this therapy are few and mild and less than those from the use of (90)Y-[DOTA(0),Tyr(3)]octreotide (DOTATOC). Besides objective tumour responses, the median progression-free survival is more than 40 months. The patients' self-assessed quality of life increases significantly after treatment with (177)Lu-DOTATATE. Lastly, compared to historical controls, there is a benefit in overall survival of several years from the time of diagnosis in patients treated with (177)Lu-DOTATATE. These findings compare favourably with the limited number of alternative therapeutic approaches. If more widespread use of PRRT can be guaranteed, such therapy may well become the therapy of first choice in patients with metastasized or inoperable neuroendocrine tumours. 相似文献
1000.