全文获取类型
收费全文 | 1980篇 |
免费 | 123篇 |
国内免费 | 6篇 |
学科分类
医药卫生 | 2109篇 |
出版年
2022年 | 13篇 |
2021年 | 14篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 38篇 |
2017年 | 35篇 |
2016年 | 24篇 |
2015年 | 35篇 |
2014年 | 58篇 |
2013年 | 92篇 |
2012年 | 90篇 |
2011年 | 97篇 |
2010年 | 73篇 |
2009年 | 72篇 |
2008年 | 86篇 |
2007年 | 105篇 |
2006年 | 64篇 |
2005年 | 65篇 |
2004年 | 45篇 |
2003年 | 55篇 |
2002年 | 42篇 |
2001年 | 48篇 |
2000年 | 38篇 |
1999年 | 44篇 |
1998年 | 64篇 |
1997年 | 63篇 |
1996年 | 46篇 |
1995年 | 31篇 |
1994年 | 35篇 |
1993年 | 37篇 |
1992年 | 33篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 50篇 |
1988年 | 49篇 |
1987年 | 59篇 |
1986年 | 45篇 |
1985年 | 48篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 18篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 12篇 |
排序方式: 共有2109条查询结果,搜索用时 15 毫秒
1.
2.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
3.
Maxillary sinusitis in adults: an evaluation of placebo-controlled double-blind trials 总被引:1,自引:0,他引:1
BACKGROUND: In general practice, acute sinusitis is frequently diagnosed
and treated with antibiotics. OBJECTIVE: This study aimed to determine the
evidence for the effectiveness of antibiotic treatment in acute maxillary
sinusitis in adults by assessing the methodological quality of
placebo-controlled double-blind randomized trials. METHOD: An evaluation by
four raters through a 35-item scoring-scale for internal and external
validity of all placebo-controlled double-blind randomized trials on acute
sinusitis found between January 1966 and July 1996. RESULTS: Eighty-five
trials were excluded because they were not placebo-controlled,
double-blind, randomized, or were carried out in patients with chronic
sinusitis or in children. The three remaining trials were performed in
different populations (one in general practice) between 1973 and 1978. Only
one study claimed superiority of antibiotic treatment. Different inclusion
criteria and major outcome measures were used by the authors. The
reliability of major outcome events was reported poorly or not at all and
in two studies outcome measures were clinically inappropriate. The studies
scored 30-62% of the maximum attainable score for internal validity and
10-20% for external validity. CONCLUSION: The effectiveness of antibiotic
treatment in acute maxillary sinusitis in a general practice population is
not based sufficiently on evidence.
相似文献
4.
B Ulfhake K Carlsson K Mossberg U Arvidsson P J Helm 《Journal of neuroscience methods》1991,40(1):39-48
This paper describes the implementation of an ultraviolet (UV) laser (Spectra Physics 171-18 with 3 lines: 334, 351 and 364 nm in UV) as light source for fluorescence confocal scanning microscopy. With this instrument it is possible to use fluorophores not previously available for confocal laser microscopical imaging of fluorophores such as fluoro-gold and AMCA. In the study we show confocal laser microscopical imaging of fluorescent motoneurons labelled by retrograde transport of fluoro-gold and AMCA-fluorescent axon terminals labelled with antisera against immunogenes as thyrotropin-releasing hormone (TRH) and calcitonin gene-related peptide (CGRP). These two fluorophores may be recorded simultaneously or separately by using a filter that suppresses the emission of one of the fluorophores. The described instrument should also be useful in applications involving detection of monoamines by the Falck-Hillarp technique, as well as measurements of cytosolic free calcium by indicators such as Fura-2 and Indo-1. Measurements performed in reflected and fluorescence light indicated that the resolution along the optical axis improved by about 25% when UV (351 nm) is used instead of visible light (514 nm). This figure is close to that expected on theoretical basis. There are, however, also serious problems related to the use of UV excitation. Firstly, objectives must be selected based on their UV transmission properties. Secondly, chromatic aberration may cause a substantial focal shift between illuminating and emitted light, calling for a flexible instrumental design in order to allow for compensation. As shown here, this problem can be circumvented by using reflecting objectives but at a price of lower resolution compared with high-aperture refracting objectives. 相似文献
5.
A synchronous occurrence of large bowel adenocarcinoma and extragenital malignant mixed mesodermal tumour (MMMT) is reported. This case represents the sixth extragenital MMMT reported in the literature. 相似文献
6.
7.
H Angus-Leppan GA Lambert J Michalicek 《Cephalalgia : an international journal of headache》1997,17(6):625-630
Co-existence of facial and occipital pain may occur in occipital neuralgia, migraine and cluster headache; suggesting convergence of trigeminal and cervical afferents. Such convergence has been shown in humans and other animals, but the site and extent of this are uncertain. In anaesthetized adult cats, the superior sagittal sinus and occipital nerve were stimulated electrically, and extracellular recordings made in the dorsolateral area of the upper cervical cord using glass-coated tungsten electrodes. Of 49 units in 10 cats, 33 (67%) had input from the superior sagittal sinus and the occipital nerve. Thirteen (27%) had superior sagittal sinus input and 3 (6%) had occipital nerve input. Convergent receptive fields were identified mechanically in 7 units. These experiments in cats show convergent input from occipital nerve and superior sagittal sinus on dorsolateral area units in two-thirds of cases studied. This experimental site of trigeminocervical convergence may relate to referral of pain in occipital neuralgia and other headaches. 相似文献
8.
In patients with PG-dependent renal function, NSAID administration
constantly reduces GFR and RBF in a dose-dependent fashion. In this
situation, the risk of overt acute renal failure is high and should be
taken into proper account. In contrast, the incidence of NSAID-related
renal structural alterations appears to be very low, yet the absolute
number of patients may be significant considering the wide use of such
drugs. Concerning the antiproteinuric effect of NSAIDs, the unfavourable
ratio risk/benefit does not seem to support their indication in proteinuric
nephropathies. The development of PGHS-2 selective inhibitors is promising,
and may open new therapeutical strategies in the treatment of the
progression of renal disease.
相似文献
9.
Oberstabsarzt B. Hossfeld M. Helm G. Hölldobler L. Lampl 《Notfall & Rettungsmedizin》2005,8(3):201-206
Zusammenfassung Die Teilnahme der Bundeswehr an internationalen Missionen erfordert ein an die Bedingungen militärischer Einsätze angepasstes Konzept zur intensivmedizinischen Repatriierung. Die umfassende Transportkapazität des auf den Airbus A-310 gestützten Systems von bis zu 44 liegenden Patienten bedingte bereits mehrfach den Einsatz im Rahmen ziviler Großschadensereignisse. Der Transport der häufig vital gefährdeten Patienten erfordert sowohl eine dem Inlandsstandard anzupassende medizintechnische Ausstattung der Luftfahrzeuge als auch entsprechend qualifiziertes medizinisches Begleitpersonal, das aufgrund der Sitzplätze zahlenmäßig begrenzt ist. Dieser Umstand verlangt vom Personal Umsicht bei der Betreuung von zeitgleich mehreren Patienten sowie Befähigung zum eigenständigen Arbeiten. Die Patienten-Transport-Einheiten (PTE) entsprechen in der technischen Ausstattung dem Intensivbehandlungsplatz einer modernen Klinik und gewährleisten auch über eine längere Transportzeit eine Intensivtherapie auf höchstem Niveau. Die Arbeit mit dieser Ausrüstung, die Besonderheiten des Langstreckenlufttransportes und die spezielle Situation des militärischen Einsatzes stellen zusätzliche Anforderungen an das Personal. Um dem gerecht zu werden, erfolgt, ergänzend zur täglichen Arbeit im Rettungsdienst, in den Notaufnahmen und auf den Intensivstationen der Bundeswehrkrankenhäuser eine spezielle Schulung von Rettungsassistenten und Ärzten am Flugmedizinischen Institut der Luftwaffe. 相似文献
10.
B. S. Kamps H. -R. Brodt S. Staszewski L. Bergmann E. B. Helm 《Journal of molecular medicine (Berlin, Germany)》1994,72(4):283-287
The clinical history of 1538 HIV positive patients was analyzed on the basis of the new CDC classification system of HIV disease and AIDS. This classification system combines three CD4 cell categories (1, 2, and 3) with three clinical categories (A, B, and C) into nine subgroups AI–C3. We examined the overall survival for all subgroups and the AIDS-free survival for subgroups Al–B3. AIDS-free survival for patients in subgroups Al, A2, and B1 was considerably longer than survival in patients from subgroups A3, B2, and B3 (P < 0.0001). According to these findings, the new CDC classification system could be simplified into three stages, stage I and II comprising the above mentioned six subgroups, and stage III comprising clinical AIDS defining categories C1, C2, and C3. These three stages correspond to different periods in the management of HIV positive patients, i.e., period of observation, period of prophylaxis, and period of treatment.Abbreviations AIDS
acquired immunodeficiency syndrome
- CDC
Centers for Disease Control
- HIV
Human immunodeficiency virus
Correspondence to: E.B. Helm 相似文献