全文获取类型
收费全文 | 1537篇 |
免费 | 116篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 59篇 |
妇产科学 | 15篇 |
基础医学 | 137篇 |
口腔科学 | 69篇 |
临床医学 | 128篇 |
内科学 | 434篇 |
皮肤病学 | 29篇 |
神经病学 | 33篇 |
特种医学 | 244篇 |
外国民族医学 | 1篇 |
外科学 | 116篇 |
综合类 | 86篇 |
预防医学 | 132篇 |
眼科学 | 16篇 |
药学 | 89篇 |
中国医学 | 24篇 |
肿瘤学 | 36篇 |
出版年
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 39篇 |
2017年 | 41篇 |
2016年 | 25篇 |
2015年 | 29篇 |
2014年 | 51篇 |
2013年 | 71篇 |
2012年 | 78篇 |
2011年 | 83篇 |
2010年 | 61篇 |
2009年 | 57篇 |
2008年 | 67篇 |
2007年 | 96篇 |
2006年 | 45篇 |
2005年 | 40篇 |
2004年 | 44篇 |
2003年 | 49篇 |
2002年 | 30篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 35篇 |
1998年 | 65篇 |
1997年 | 53篇 |
1996年 | 44篇 |
1995年 | 25篇 |
1994年 | 31篇 |
1993年 | 29篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 33篇 |
1988年 | 35篇 |
1987年 | 40篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1928年 | 4篇 |
排序方式: 共有1659条查询结果,搜索用时 187 毫秒
1.
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
2.
M Caruana R Jones A Lahiri G Brigden E Rodrigues C Dore E B Raftery 《Nuclear medicine communications》1986,7(10):717-728
Five studies were conducted to examine the degree of variability to be expected during the use of the non-imaging nuclear probe (BIOS Inc.) under a variety of clinical conditions. Comparison of the ejection fraction (EF) readings between the nuclear probe and a gamma camera showed good agreement, with the nuclear probe tending to underestimate lower, and overestimate higher camera EF values [mean (S.D.) difference, 0.84% (6.06)]. A comparison of two nuclear probes showed a small mean (S.D.) difference of EF readings of 0.063% (2.26). EF readings obtained in normal subjects 6 weeks apart were reproducible and differed by a mean (S.D.) of 0.23% (4.42). The administration of placebo to 10 normal subjects followed by sequential measurements for 4 h produced EF changes large enough to mimic a clinical effect, the largest hourly change observed being 5.4%, indicating the need for strict placebo control in interventional experiments. Data on four patients with heart failure showed small non-significant EF changes in the 1 h after placebo administration but a wide intra-subject range of ejection time and time to peak filling measurements. This highlights the problem of accurate, reproducible cursor placement in such patients. The nuclear probe is a portable, low cost instrument which produces accurate EF measurements when compared with the gamma camera. 相似文献
3.
Margaret MacDonald Matthew Law John Kaldor Jim Hales Gregory J. Dore 《The International journal on drug policy》2003,14(5-6):353
Objective: To examine the effectiveness of needle and syringe programmes (NSPs) in preventing HIV transmission among injecting drug users (IDUs).Methods: An ecological study design was used to determine change in HIV prevalence among injecting drug users between cities with and without NSPs. Several data sources, such as electronic journal databases, surveillance reports, websites, and index review of relevant journals, were used to identify studies of HIV seroprevalence among IDUs, and presence of NSPs. The rate of change in HIV prevalence was estimated by regression analysis.Results: There were 778 years of data from 99 cities globally included in the analysis. HIV prevalence decreased by 18.6% per annum in cities that introduce NSPs, and increased by 8.1% in cities that had never introduced NSPs (mean difference −24.7% [95% CI: −43.8, 0.5%], P=0.06). The mean difference was –33% when comparison was weighted to one over the variance of the regression estimator (29% decrease in cities with NSPs and 5% increase in cities without NSPs, P<0.001). When analysis was restricted to cities with first HIV seroprevalence less than 10%, the average annual change in seroprevalence was 18% lower in cities with NSPs (P=0.03).Conclusions: Despite the inherent limitations within an ecological study design, the study provides additional evidence that NSPs reduce transmission of HIV infection. The rapid spread of HIV among IDU populations and increasing rates of injecting in many countries calls for scaling up of NSPs as well as other harm reduction strategies. 相似文献
4.
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
5.
6.
D Dore 《Physical therapy》1987,67(6):964-966
The purpose of this study was to examine the effect of the Medicare prospective payment system on the utilization of physical therapy for patients served by Medicare. The total number of inpatient and outpatient physical therapy referrals and the percentage of physical therapy Medicare referrals from January 1981 through May 1985 for the 336 acute care beds in the county selected for this study were analyzed. The results indicated that acute care inpatient and outpatient physical therapy Medicare referrals have increased significantly since the implementation of the diagnostic related group system. The results indicate that physical therapy is being used increasingly to rehabilitate patients within the time and economic constraints established by the Medicare prospective payment system. 相似文献
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.
10.