首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7684篇
  免费   907篇
  国内免费   139篇
耳鼻咽喉   43篇
儿科学   110篇
妇产科学   62篇
基础医学   753篇
口腔科学   87篇
临床医学   930篇
内科学   813篇
皮肤病学   31篇
神经病学   1614篇
特种医学   504篇
外科学   457篇
综合类   1171篇
一般理论   2篇
预防医学   768篇
眼科学   63篇
药学   692篇
  8篇
中国医学   487篇
肿瘤学   135篇
  2024年   12篇
  2023年   116篇
  2022年   194篇
  2021年   414篇
  2020年   392篇
  2019年   358篇
  2018年   318篇
  2017年   344篇
  2016年   330篇
  2015年   358篇
  2014年   620篇
  2013年   549篇
  2012年   482篇
  2011年   511篇
  2010年   379篇
  2009年   375篇
  2008年   329篇
  2007年   328篇
  2006年   310篇
  2005年   263篇
  2004年   207篇
  2003年   202篇
  2002年   162篇
  2001年   124篇
  2000年   93篇
  1999年   96篇
  1998年   63篇
  1997年   74篇
  1996年   48篇
  1995年   56篇
  1994年   62篇
  1993年   53篇
  1992年   39篇
  1991年   47篇
  1990年   58篇
  1989年   36篇
  1988年   31篇
  1987年   28篇
  1986年   30篇
  1985年   37篇
  1984年   38篇
  1983年   15篇
  1982年   22篇
  1981年   19篇
  1980年   25篇
  1979年   15篇
  1978年   16篇
  1977年   22篇
  1975年   8篇
  1974年   7篇
排序方式: 共有8730条查询结果,搜索用时 156 毫秒
31.
The aim of the project was to survey the hospital prevalence of apallic syndrome in a federal state in Austria at an exact point in time. To achieve this, a point prevalence study was carried out on 28 November 2001 in the Vienna region. The central element was a questionnaire, which provided an exact recording of the patients' condition. An additional preliminary task was to check all the discharge diagnoses in the hospitals of the Vienna Hospital Association (Wiener Krankenanstalten Verbund) between 1996 and 2000 according to the ICD-9 diagnoses for apallic syndrome. These data should serve to cross-check the recorded results. All hospitals (n = 48) and nursing facilities (n = 44) in Vienna were included in this investigation. As the aim of the study was to record the prevalence of apallic syndrome in the population of Vienna, four patients of the group with full-stage apallic syndrome (n = 36) were excluded as they were from other federal states. In total, 32 hospital patients who met the clinical criteria for apallic syndrome (full-stage) were recorded. The point prevalence of apallic syndrome was 1.9/100,000 inhabitants. As a result of this study, the exact survey of hospital prevalence of apallic syndrome could be found. As a consequence, the Viennese government has developed a rehabilitation concept for patients with apallic syndrome in Vienna.  相似文献   
32.
The aim of this work was to examine the occurrence of stressful events in the lives of children, using the ‘Scale of Infantile Social Readjustment’ (SISR), and the ‘Inventory of Symptoms of Infantile Stress’ (ISIS) to identify the presence of stress symptoms. The results of these evaluations were then used to examine the relationship between the levels of stress and the nutritional state of the children, by correlation. Forty 7–10‐year‐old children were included in the evaluation. From the analysed sample 49 per cent of them were eutrophic (weight/height normal to age), 50 per cent were above weight and 1 per cent was undernourished. Whereas 70 per cent of the girls were eutrophic and 30 per cent were above weight, only 35 per cent of the boys were eutrophic, 60 per cent were above weight and 5 per cent were undernourished. The results obtained in this first study indicated that 45 per cent of eutrophic girls demonstrated symptoms of stress, while 20 per cent of them were asymptomatic (with no symptoms of stress). Of the overweight boys, 30 per cent of them showed symptoms of stress and 35 per cent did not. This study indicated a possible relationship between weight and the symptoms of stress. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
33.
A previously developed eigenvector formalism is adapted to off-resonance in the transient response of quasiperiodic steady-state free precession (SSFP) sequences, including TrueFISP as a special case. The effective relaxation rates for essentially parallel and perpendicular deviations from the steady state are determined analytically in leading order perturbation theory. The latter are a known cause of oscillatory artifacts and therefore constitute the main target of a variety of preparation techniques. In addition, the former also play a dominating role in applications such as inversion recovery (IR) TrueFISP, which intentionally measure far away from the equilibrium. For both components, the approach toward equilibrium turns out to depend sensitively on field inhomogeneities, especially for smaller ratios of T2/T1. For the perpendicular deviations, the calculations show that--except very close to banding artifacts, where the steady-state signal is almost zero--field inhomogeneities additionally increase their effective relaxation rate almost as much as in the free induction decay (FID). The analytical results are tested against numerical simulation and MR measurements.  相似文献   
34.
Magnetization prepared segmented acquisition requires a view order that maximizes signal contrast during the acquisition of the central portion of k-space. Steady state free precession (SSFP) acquisition further requires a view order that minimizes changes in phase-encoding gradients from one repetition to the next in order to minimize eddy current artifacts. In this article, optimal view ordering schemes satisfying these two requirements are formulated and applied to inversion prepared 3D SSFP contrast-enhanced MR angiography (MRA). Experiments on phantoms and pigs demonstrated improved background suppression and reduced image artifacts.  相似文献   
35.
Spoiled gradient echo sequences can only reach a homogeneous steady state if sufficiently strong crusher gradients are used in combination with RF phase cycling (RF spoiling). However, the signal depends quite sensitively on the chosen phase increment ? and—lacking analytical solutions—numerical simulations must be used to study the transient and steady‐state magnetization. For the steady state an exact analytical solution is derived, which holds for arbitrary sequence and tissue parameters. Besides a considerably improved computation performance, the analytical approach enables a better understanding of the complicated dependence on ?. For short repetition times (TR) the regime of small ? turns out to be particularly interesting: It is shown that the typical ?c, where RF spoiling starts to become effective, is essentially inversely proportional to T2. This tissue dependence implies that contrasts can be considerably larger with partial spoiling (? ≈ ?c) than with conventional RF spoiling (? ? ?c). As an example, the uptake of contrast agents in tissues is investigated. For typical parameters a considerably improved contrast enhancement can be obtained, both theoretically and experimentally. Magn Reson Med, 2006. © 2005 Wiley‐Liss, Inc.  相似文献   
36.
深圳市龙岗区坪地外来工亚健康状态的研究   总被引:5,自引:0,他引:5  
目的 :探讨深圳市龙岗区坪地外来工亚健康状况及其影响因素 ,为预防亚健康提供科学依据。方法 :采用统一表格对 12 68深圳市龙岗区坪地外来工进行调查。结果 :外来工的平均年龄为 ( 2 4.96± 6.10 )a ,其亚健康状态总体发生率为 65 .3 0 %,男性亚健康状态发生率为 63 .2 1%,女性为 67.91%,男性和女性之间差异无统计学意义。亚健康状态主要影响因素为 :结婚与否、睡眠时间、工作时间、加班时间以及工作是否有压力和居住环境差等因素 ,而与吸烟、饮酒、文化程度等因素无相关。结论 :深圳龙岗区坪地外来工中普遍存在亚健康状态 ,其发生较高且与工作环境、工作时间、加班时间有密切关系 ,故应引起政府部门及社会各界高度重视 ,加强对外来工的健康保护  相似文献   
37.
The purpose of this study was to examine the effect of exacerbations on mild to moderate asthmatic patients' preference-based, health-related, quality of life scores and also to describe the effect of these exacerbations on daily life. In a survey, 100 mild to moderate asthmatic patients in the United Kingdom were asked to rate three different health marker states on a scale between 0 (death) and 100 (perfect health), defined as: your asthma of today, a mild exacerbation, and a severe exacerbation of asthma. They were also asked to describe their symptoms and what they did when experiencing an exacerbation. During exacerbations the vast majority of asthmatic patients have significant symptoms and consume a considerable amount of health care resources, which often overlap. The health marker state “your asthma of today” was given a mean score of 81.0, a mild exacerbation a score of 62.1, and a severe exacerbation a score of 25.6, indicating a large impact on patients' daily life and their health-related quality of life. In conclusion, asthmatic patients are severely affected in their health and daily living by mild and severe exacerbations. Considerable effort should be made to reduce the number and severity of exacerbations.  相似文献   
38.
EVOKED POTENTIALS OF OBSESSIVE-COMPULSIVE DISORDER: STATE OR TRAIT MARKER   总被引:1,自引:0,他引:1  
Objective To investigate the status of evoked potentials in obsessive-compulsive disorder(OCD). Methods Evoked potentials P300, auditory brainstem response (ABR) and visual evoked potential ( VEP) were recorded from 35 OCD patients and 28 normal controls (NC) with a Nicolet Spirit Instrument. 23 of the OCD patients were followed up after 5 months with the same markers. Results Compared with NC, OCD patients showed decreased P3 of P300 amplitude (OCD group 3. 5 ±1. 6μv vs. NC group 5.9 ±2. 1μv, P <0. 01), delayed V latency (6.4±0. 4ms vs. 5. 5 ±0. 3ms, P <0. 01) and increased V amplitude(0. 35±0. 1μv vs. 0. 16 ±0.09μv, P <0. 05) of ABR and delayed P2 of VEP latency (199±39ms vs. 183±28ms, P <0. 05). The follow-up measures of evoked potentials suggested that decreased P3 of P300 amplitude and delayed P2 of VEP latency might be state markers of OCD, while decreased V amplitude and delayed V of ABR latency might be trait markers of OCD. Conclusion The changes of P300 and VEP are related to clini  相似文献   
39.
This work describes a new approach to multipoint Dixon fat-water separation that is amenable to pulse sequences that require short echo time (TE) increments, such as steady-state free precession (SSFP) and fast spin-echo (FSE) imaging. Using an iterative linear least-squares method that decomposes water and fat images from source images acquired at short TE increments, images with a high signal-to-noise ratio (SNR) and uniform separation of water and fat are obtained. This algorithm extends to multicoil reconstruction with minimal additional complexity. Examples of single- and multicoil fat-water decompositions are shown from source images acquired at both 1.5T and 3.0T. Examples in the knee, ankle, pelvis, abdomen, and heart are shown, using FSE, SSFP, and spoiled gradient-echo (SPGR) pulse sequences. The algorithm was applied to systems with multiple chemical species, and an example of water-fat-silicone separation is shown. An analysis of the noise performance of this method is described, and methods to improve noise performance through multicoil acquisition and field map smoothing are discussed.  相似文献   
40.
抗凝治疗肺心病血栓前状态的临床研究   总被引:6,自引:2,他引:4  
目的探讨肺心病患者的血栓前状态,观察并分析低分子肝素抗凝干预的疗效。方法将54倒肺心病患者分为低分子肝素治疗组和常规治疗组各27例。分别检测治疗前后血浆血管性假血友病因子(VWF)、血浆凝血酶片段1 2(F1 2)、纤堆蛋白原(Fg)、血小板颗粒膜蛋白(GMP-140)和D-二聚体(DD)。结果肺心病患者VWF、F1 2、Fg、GMP-140、DD血浆浓度显著高于对照组;肺心病治疗组经LMWH治疗后上述各凝血分子标记物及PaCO2明显降低。而PaO2显著增高。常规组虽血气指标略有改善。但凝血分子标记物未见改善。结论尽早检测肺心病血栓前状态,及时给予低分子肝素抗凝干预,有望从根本上改善肺心病惠性加重期患者的不良预后。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号