全文获取类型
收费全文 | 177429篇 |
免费 | 916篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 1166篇 |
儿科学 | 6668篇 |
妇产科学 | 3082篇 |
基础医学 | 16854篇 |
口腔科学 | 1618篇 |
临床医学 | 12489篇 |
内科学 | 31166篇 |
皮肤病学 | 696篇 |
神经病学 | 16577篇 |
特种医学 | 9007篇 |
外科学 | 29136篇 |
综合类 | 2315篇 |
预防医学 | 18133篇 |
眼科学 | 2803篇 |
药学 | 9654篇 |
中国医学 | 632篇 |
肿瘤学 | 16383篇 |
出版年
2021年 | 27篇 |
2019年 | 34篇 |
2018年 | 21941篇 |
2017年 | 17381篇 |
2016年 | 19527篇 |
2015年 | 928篇 |
2014年 | 832篇 |
2013年 | 802篇 |
2012年 | 6989篇 |
2011年 | 21040篇 |
2010年 | 18851篇 |
2009年 | 11564篇 |
2008年 | 19582篇 |
2007年 | 21802篇 |
2006年 | 633篇 |
2005年 | 2292篇 |
2004年 | 3526篇 |
2003年 | 4481篇 |
2002年 | 2612篇 |
2001年 | 299篇 |
2000年 | 446篇 |
1999年 | 202篇 |
1998年 | 237篇 |
1997年 | 222篇 |
1996年 | 107篇 |
1995年 | 131篇 |
1994年 | 132篇 |
1993年 | 97篇 |
1992年 | 60篇 |
1991年 | 110篇 |
1990年 | 141篇 |
1989年 | 97篇 |
1988年 | 75篇 |
1987年 | 63篇 |
1986年 | 36篇 |
1985年 | 42篇 |
1984年 | 39篇 |
1983年 | 43篇 |
1982年 | 48篇 |
1980年 | 70篇 |
1978年 | 26篇 |
1975年 | 31篇 |
1970年 | 27篇 |
1969年 | 26篇 |
1939年 | 26篇 |
1938年 | 64篇 |
1937年 | 27篇 |
1934年 | 33篇 |
1932年 | 60篇 |
1930年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Stolzmann P Alkadhi H Scheffel H Plass A Leschka S Falk V Kozerke S Wyss C Donati OF 《The international journal of cardiovascular imaging》2011,27(7):969-977
To investigate prospectively, in patients with suspicion of coronary artery disease (CAD), the added value of coronary calcium
scoring (CS) as adjunct to cardiac magnetic resonance (CMR) for the diagnosis of morphological coronary stenosis in comparison
to catheter angiography (CA). Sixty consecutive patients (8 women; 64 ± 10 years) referred to CA underwent CMR (1.5 T) including
perfusion and late gadolinium-enhancement imaging as well as CS with computed tomography. Diagnostic performance was evaluated
for CMR and CS separately, and for both methods combined, with CA as reference standard. Best CS threshold combined with a
specificity >90% to predict significant stenosis in patients without abnormalities on CMR was determined from receiver operator
characteristics (ROC) analysis. Abnormal CMR results were considered to indicate significant stenosis regardless of CS; CS
above threshold reclassified patients to have CAD regardless of CMR. CA identified 104/960 (11%) coronary segments with coronary
artery stenosis >50% in 36/60 (60%) patients. ROC revealed an area-under-the-curve of 0.83 (95%CI: 0.68-0.99) with the best
CS threshold of 495 Agatston score (sensitivity 50%). CMR depicted 128/960 (13%) myocardial segments with abnormalities in
31/60 (52%) patients. Sensitivity, specificity, negative (NPV) and positive predictive value (PPV) of CMR were 78, 88, 72
and 90%. When adding CS to CMR, sensitivity and NPV increased to 89 and 83%, while specificity and PPV slightly decreased
to 83 and 89%. Accuracy of the combined approach (87%) was significantly (P < 0.05) higher than that of CMR (82%) alone. Adding CS to CMR improves the accuracy for the detection of morphological CAD. 相似文献
992.
993.
Nair SU Ahlberg AW Mathur S Katten DM Polk DM Heller GV 《Journal of nuclear cardiology》2012,19(2):244-255
Background
The role of single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) in cardiac evaluation of the very elderly patients is unclear. We investigated the clinical value of SPECT MPI in very elderly patients (≥80 years) with suspected coronary artery disease (CAD) as well as in comparison to younger patients. 相似文献994.
Teri L. Bourdeau Larry L. Mullins Melissa Y. Carpentier Christina J. M. Colletti Cortney Wolfe-Christensen 《Journal of developmental and physical disabilities》2007,19(2):125-134
The present study examined the relationship of three parent-related variables, namely, perceived child vulnerability, parental
overprotection, and parenting stress to child self-care behaviors among 200 children with Type 1 diabetes, asthma, or cystic
fibrosis. A related goal of the study was to examine for illness- and age-related differences among the same variables of
interest. Results indicated that higher levels of parenting stress were associated with lower parent ratings of their child’s
self-care behaviors. Additional analyses of individual illness groups demonstrated that age was significantly related to both
child and parent ratings of self-care only for the diabetes group, with older children engaging in lower levels of self-care.
Such results support continued investigation of parent behaviors and beliefs as they relate to child self-care outcomes at
different ages in pediatric chronic illness populations. 相似文献
995.
Timothy M. Bateman 《Journal of nuclear cardiology》2012,19(1):3-11
The continued high utilization of rest-stress single-photon emission computed tomographic (SPECT) myocardial perfusion imaging (MPI) is supported by its known clinical benefits, established reimbursement, and wide availability of cameras and radiopharmaceuticals. However, traditional rest-stress SPECT protocols tend to be lengthy and inefficient, and the prevalence of equivocal studies continues to be a problem. The use of stress-only SPECT protocols in selected patients, and a new generation of ultrafast SPECT cameras have led to improved image quality, reduced dosimetry and shorter, more efficient MPI protocols. The utilization of positron emission tomographic (PET) MPI has been accelerated by the availability of radiopharmaceuticals that can be generated on-site, and by the availability of more PET cameras. Emerging evidence consistently demonstrates that PET provides improved image quality, greater interpretive certainty, higher diagnostic accuracy, lower patient dosimetry, and shorter imaging protocols as compared to SPECT. Importantly, PET imaging allows assessment of left ventricular function at peak-stress, and evaluation of microvascular function through the measurement of absolute myocardial blood flow at rest and at peak-stress. Wider utilization of PET MPI is hindered by a high cost of entry, high on-going costs, and an immature reimbursement structure. 相似文献
996.
Duvall WL Sweeny JM Croft LB Ginsberg E Guma KA Henzlova MJ 《Journal of nuclear cardiology》2012,19(1):19-27
Background
Cadmium Zinc Telluride (CZT) SPECT camera technology has the potential to reduce patient’s radiation exposure and shorten imaging time. This study evaluated the correlation of low stress tracer dose, rapid CZT SPECT myocardial perfusion imaging (MPI) to coronary angiography in a <200-lbs population to further validate its ability to achieve both goals while preserving diagnostic accuracy. 相似文献997.
Johnny L. Matson Jonathan Wilkins Melissa González 《Journal of developmental and physical disabilities》2007,19(6):565-577
Most of the scale development work in autism spectrum disorders (ASD) to date has focused on instrumentation designed for
one disorder, autism, and mainly focused on young children. Three hundred seventy-one staff were administered a newly developed
assessment scale for adults with ID. The Autism Spectrum Disorders—Diagnosis Scale for Intellectually Disabled Adults (ASD—DA)
was designed to quickly provide relevant information to establish a diagnosis for the most common ASD (autism, PDD-NOS, and
Asperger’s syndrome). Staff completed the assessment for adults with ID (n = 192) some of which had a diagnosis of either autism or PDD-NOS (n = 107) or ID alone (n = 85). Inter-rater and test-retest reliability data were obtained. Item analysis reduced the scale to 31 items that were
found to be both reliable and significantly differentiate between groups. A factor analysis with a three-factor solution was
identified. The internal consistency of factor and total scale scores were found to be excellent. 相似文献
998.
Nishikawa K Hagiwara R Nakamura K Ishizeki J Kubo K Saito S Goto F 《Journal of clinical monitoring and computing》2007,21(2):109-114
Backgrounds Patients may become sedated with␣spinal anesthesia; however, the effect of the extent of␣spinal block on the Bispectral index
(BIS), a processed electroencephalographic variable, has not been fully investigated. We evaluated the influence of the extent
of spinal block on BIS values and on regional cerebral oxygen saturation (rSO2) in elderly patients.
Methods A prospective, randomized, double-blinded study was performed in 55 ASA II patients undergoing urological surgery. The patients
were randomly allocated into one of two groups to receive 2.7 ml of 0.5% hyperbaric bupivacaine or 1.5 ml, and then divided
into two groups according to level of spinal blockade: high spinal group (Th6 and above) or low spinal group (Th12 and below).
Systolic blood pressure (SBP), heart rate (HR), cardiac output (CO), stroke volume (SV), BIS values, and rSO2 were measured for 30 min. CO and SV were evaluated using impedance cardiograph methods.
Results The level of spinal blockade was Th4.7 ± 1.0 in high spinal group (n = 20) and L2.5 ± 2.2 in low spinal group (n = 20). High spinal anesthesia produced a significant decrease in SBP (p < 0.01) and SV (p < 0.01), but had no effect on CO. High spinal anesthesia significantly decreased BIS values (p < 0.01) without affecting rSO2. There was relationship between level of spinal blockade and BIS values (r = 0.566). In contrast, no changes in above parameters were found in low spinal group.
Conclusions This study provides evidence that the extent of spinal block may have significant influence on BIS values without affecting
rSO2 in elderly patients.
A part of the present study was presented at the Annual Meeting of the Japan Society of Anesthesiologists, June 02–04, 2005
at Kobe, Japan.
Nishikawa K,Hagiwara R, Nakamura K, Ishizeki J, Kubo K, Saito S, Goto F. The effects of the extent of spinal block on the
BIS score and regional cerebral oxygen saturation in elderly patients: A prospective, randomized, and double-blinded study. 相似文献
999.
Noninvasive positive ventilation has undergone a remarkable evolution over the past decades and is assuming an important role in the management of both acute and chronic respiratory failure. Long-term ventilatory support should be considered a standard of care to treat selected patients following an intensive care unit (ICU) stay. In this setting, appropriate use of noninvasive ventilation can be expected to improve patient outcomes, reduce ICU admission, enhance patient comfort, and increase the efficiency of health care resource utilization. Current literature indicates that noninvasive ventilation improves and stabilizes the clinical course of many patients with chronic ventilatory failure. Noninvasive ventilation also permits long-term mechanical ventilation to be an acceptable option for patients who otherwise would not have been treated if tracheostomy were the only alternative. Nevertheless, these results appear to be better in patients with neuromuscular/-parietal disorders than in chronic obstructive pulmonary disease. This clinical review will address the use of noninvasive ventilation (not including continuous positive airway pressure) mainly in diseases responsible for chronic hypoventilation (that is, restrictive disorders, including neuromuscular disease and lung disease) and incidentally in others such as obstructive sleep apnea or problems of central drive. 相似文献
1000.
Assessment of the extension and the inflammatory activity in Crohn’s disease: comparison of ultrasound and MRI 总被引:2,自引:0,他引:2
Objective The purpose of this prospective study was twofold: to examine the efficacy of MRI and sonography in the assessment of Crohn’s
disease (CD) activity in comparison with clinical scoring and biologic tests and to compare both techniques in the evaluation
of extension and transmural complications.
Material and methods Thirty patients with histologically proven Crohn’s disease were prospectively examined the same day first with sonography
and after MRI. Sonographic exam included evaluation of bowel wall thickness, vascularity pattern, and perienteric changes.
Thirty minutes prior to MRI imaging, patients were given 250 mL of dilute sodium phosphate solution and additional 750 mL
of water orally. MRI images evaluation included bowel wall thickening, bowel wall enhancement, and perienteric changes. The
gastrointestinal tract was divided into five segments. Findings and extension of the both techniques were verified by means
of barium studies, surgery, or/and colonoscopy. The sonographic and MR findings were compared with clinical and laboratory
data.
Results About 53 of 119 (45%) bowel segments showed pathological changes in gold standard tests. Sonography was superior to MRI in
the localization of affected bowel segments (sensitivity: US 91%; MRI 83%; intertechniques agreement, kappa: 0.905) and in recognizing transmural complications (sensitivity: US 80%; MRI 72%), although significant differences were
not found (p > 0.05). A statistically significant correlation between color Doppler flow and MR bowel wall enhancement (segment-by-segment
analysis and per patient analysis; p > 0.5), and between perienteric changes in both techniques (p > 0.5) were found. Wall thickness measured on sonography was significantly greater in the group of patients with clinical
activity (p = 0.023) or with clinical-biologic activity (p = 0.024). Grades of hyperemia and MR contrast enhancement of patients with clinical–biologic activity was higher than in
patients without clinical–biologic activity (p = 0.019; p = 0.023).
Conclusion In summary, both ultrasound and MRI are sensitive to localize the affected bowel segments and to detect transmural complications
in patients with Crohn’s disease. A significant correlation between color Doppler flow and bowel wall enhancement on MRI was
found. Sonographic wall thickness, color Doppler flow, and bowel wall enhancement on MRI are related with clinical or biologic
activity. 相似文献