全文获取类型
收费全文 | 270592篇 |
免费 | 15666篇 |
国内免费 | 7618篇 |
专业分类
耳鼻咽喉 | 3483篇 |
儿科学 | 8674篇 |
妇产科学 | 3135篇 |
基础医学 | 18736篇 |
口腔科学 | 6592篇 |
临床医学 | 32300篇 |
内科学 | 45281篇 |
皮肤病学 | 3248篇 |
神经病学 | 13505篇 |
特种医学 | 27198篇 |
外国民族医学 | 43篇 |
外科学 | 37377篇 |
综合类 | 26274篇 |
现状与发展 | 29篇 |
预防医学 | 16215篇 |
眼科学 | 7405篇 |
药学 | 25625篇 |
91篇 | |
中国医学 | 4788篇 |
肿瘤学 | 13877篇 |
出版年
2023年 | 2750篇 |
2022年 | 4911篇 |
2021年 | 12187篇 |
2020年 | 6922篇 |
2019年 | 12633篇 |
2018年 | 7350篇 |
2017年 | 6469篇 |
2016年 | 8377篇 |
2015年 | 11361篇 |
2014年 | 20764篇 |
2013年 | 17877篇 |
2012年 | 21433篇 |
2011年 | 18815篇 |
2010年 | 17013篇 |
2009年 | 16593篇 |
2008年 | 15402篇 |
2007年 | 15411篇 |
2006年 | 13296篇 |
2005年 | 9324篇 |
2004年 | 5555篇 |
2003年 | 4729篇 |
2002年 | 3830篇 |
2001年 | 3192篇 |
2000年 | 2757篇 |
1999年 | 1927篇 |
1998年 | 2233篇 |
1997年 | 2100篇 |
1996年 | 1686篇 |
1995年 | 1720篇 |
1994年 | 1637篇 |
1993年 | 1256篇 |
1992年 | 1382篇 |
1991年 | 1228篇 |
1990年 | 1235篇 |
1989年 | 1201篇 |
1988年 | 1118篇 |
1987年 | 999篇 |
1986年 | 794篇 |
1985年 | 1733篇 |
1984年 | 1904篇 |
1983年 | 1351篇 |
1982年 | 1477篇 |
1981年 | 1429篇 |
1980年 | 1227篇 |
1979年 | 1045篇 |
1978年 | 795篇 |
1977年 | 801篇 |
1976年 | 682篇 |
1974年 | 458篇 |
1973年 | 433篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Comparison of computer-assisted learning with tutorial teaching in a group of first-year dental students 总被引:1,自引:0,他引:1
Two identical groups of first-year dental students were instructed in the pathology of dental caries and periodontitis using computer-assisted learning (CAL) or tutorial teaching (TT). A cross-over arrangement, in which the first group was taught about dental caries by CAL and periodontitis by TT and the second group in the reverse order, allowed comparison of the two methods. The comparison included a knowledge test and completion of a questionnaire. CAL and TT were equally effective as far as acquisition of knowledge was concerned. Students felt pressurized with CAL and had problems with note-taking. They liked a teacher to be present. Nevertheless, CAL was an acceptable method of instruction and was more economical, in terms of staff involvement, than TT. 相似文献
992.
David Karasick M.D. Eric A. Huettl M.D. Jerome M. Cotler M.D. 《Skeletal radiology》1992,21(6):359-363
With the growing number of orthopedic reconstructive spinal procedures, the use of bone grafting has steadily increased in the past decade. An understanding of the biology of bone grafting is essential for both the clinician and radiologist. Despite the advent of computed tomography and magnetic resonance imaging, conventional polydirectional tomography remains an important tool in the evaluation of vertebral body autografts. Trispiral or hypocycloidal tomography plays a valuable role in the assessment of bone graft fusion and possible complications, especially in the presence of metallic fixation devices. We present our imaging experience derived from 375 patients with cervical, thoracic, or lumbar anterior spinal fusion. True graft complications occurred in 27 patients (7%) and consisted of fracture (4%), malpositioning (3%), and infection (<1%). 相似文献
993.
Stuart J. McLachlan John C. Francisco Joseph R. Pernicone Anton N. Hasso 《Journal of magnetic resonance imaging : JMRI》1994,4(3):405-411
A phase III multicenter study was conducted in 89 patients with known intracranial vascular lesions to evaluate an extracellular gadolinium contrast agent, gadoteridol, for intracranial magnetic resonance (MR) angiography. The pre- and postcontrast MR angiograms of 82 patients were evaluated by the unblinded investigators and by two blinded readers (A and B) for visualization of lesions; arterial and venous anatomy; extent, size, and number of lesions; and disease classification. The unblinded readers indicated that lesions were visualized better on postcontrast images in the following categories: venous anatomy, 87 (81%) of 107 lesions; arterial anatomy, 43 lesions (40%); and extent or size of lesions, 38 lesions (36%). In 29 (35%) of 82 patients, the unblinded readers determined that enhanced MR angiography provided more diagnostic information than unenhanced MR angiography. The blinded readers determined that enhanced MR angiography provided more information for visualization of vascular anatomy in more than 60% of cases. The additional information provided with gadoteridol would have changed the diagnosis in nine (8%) of 107 lesions seen by the unblinded readers, 11 (12%) of 90 lesions seen by reader A, and three (3%) of 93 lesions seen by reader B. The results confirm that the use of gadoteridol improves the visualization of intracranial vascular lesions with MR angiography. The authors conclude that development of new postprocessing algorithms will improve the utility of contrast-enhanced MR angiography. 相似文献
994.
H. Seyer J. Honegger W. Schott M. Küchle W. J. Huk R. Fahlbusch H. Frisch 《Acta neurochirurgica》1994,131(1-2):157-159
Summary Inferior petrosal sinus sampling (IPSS) is used to evaluate the pituitary-dependency of Cushing's disease, and to predict the laterality of a microadenoma prior to transsphenoidal operation. A serious complication occured in a 14-year-old boy: he suffered brain stem ischaemia with abducens nerve palsy and hemiparesis (Raymond's syndrome). The case prompted us to reconsider the indication for this investigation. 相似文献
995.
996.
997.
Plasma volume estimation using indocyanine green with biexponential regression analysis of the decay curves 总被引:2,自引:0,他引:2
We studied seven analytical methods of estimating the plasma volume from the decay curves of indocyanine green. Fifteen volunteers received 1.0 mgkg−1 of the dye by intravenous injection and the plasma concentration was measured continuously using spectrophotometry. Plasma volumes were calculated using three single-regression methods (1-a, 1-b, 1-c) and four biexponential regression methods (2-a, 2-b, 2-c, 2-d). The means (SD) of 1-a, 1-b and 1-c were 39 (5.0), 44 (5.7) and 54 (11.5) mlkg−1 , respectively, and these were significantly different from each other (p < 0.05). The values for methods 2-b, 2-c and 2-d were similar to each other: 39 (4.6), 40 (4.1) and 40 (4.0) mlkg−1 , respectively. These required more than 3 min circulation or mixing time. When the time allowed for mixing was less than 3 min (method 2-a) the plasma volume was underestimated. We conclude that plasma volume estimation using indocyanine green and spectrophotometry is most accurate when the mixing time is adequate (3–5 min) and the decay curves are analysed using biexponential regression. 相似文献
998.
999.
Gianmauro Sacchetti Eugenio Inglese Angelo S Bongo Franco Aina Marco Brambilla Alberto Baroli Carmelo Cernigliaro Pierfranco Dellavesa Edgardo Pittaluga Marco Rudoni 《European journal of nuclear medicine and molecular imaging》1997,24(10):1230-1236
The aim of this study was to determine the diagnostic accuracy of technetium-99m tetrofosmin myocardial imaging for the localization
of coronary artery stenoses of different degrees of severity. Stress-rest single-photon emission tomography (SPET) was performed
on separate days in 80 patients (64 males, 16 females; mean age 61 years; 43 patients with previous myocardial infarction;
18 patients with pharmacological stress), within 6 months of coronary angiography. Scintigraphic images were blindly and independently
evaluated by three observers. Coronary stenosis was defined as a >50% narrowing in luminal diameter; severe stenosis was defined
as a proximal stenosis of >75% or a peripheral stenosis of >90%. Coronary angiography revealed normal coronary arteries or
insignificant coronary stenosis in 13 patients and significant coronary stenoses in 67 patients. The sensitivity and specificity
of 99mTc-tetrofosmin SPET in respect of severely stenosed vessels were, respectively, 80% and 65% for the left anterior descending
artery (LAD), 100% and 46% for the right coronary artery (RCA) and 58 and 78% for the left circumflex artery (LCx) territories.
Considering all the significantly stenosed vessels, a significant decrease in sensitivity was observed for LAD territories
(to 59%, P=0.05), and a nonsignificant decrease for RCA (88%) and LCx (47%) territories while specificity values remained essentially
unchanged. No significant changes in sensitivity or specificity were observed when regions with previous myocardial infarction
were excluded. In conclusion, the sensitivity of 99mTc-tetrofosmin SPET for the localization of individual stenosed vessels is only moderate when all significant stenoses are
considered, but the ability of this technique to predict the location of severe coronary artery stenoses seems satisfactory,
with the exception of the low specificity in respect of RCA territories.
Received 26 April and in revised form 7 June 1997 相似文献
1000.
Kengo Yoshimitsu Hiroshi Honda Kuniyuki Kaneko Toshiro Kuroiwa Hiroyuki Irie Takashi Ueki Kazuo Chijiiwa Kenji Takenaka Kouji Masuda 《Journal of magnetic resonance imaging : JMRI》1997,7(4):696-701
Forty-nine pathologically proven gallbladder lesions were evaluated in 45 patients using dynamic MRI with a spoiled gradient pulse sequence (SPGR), to access the ability of this technique to differentiate benign from malignant gallbladder lesions. The studies were reviewed retrospectively. Signal intensity of the lesions were measured. Twenty-one malignant and 28 benign lesions were classified into three categories: polypoid, diffuse wall thickening, and exophytic. Early and delayed enhancement patterns were evaluated. For the polypoid masses, malignant lesions (n = 9) demonstrated early and prolonged enhancements, whereas benign lesions (n = 14) had early enhancement with subsequent washout (P < .05). For diffuse gallbladder wall thickening, malignant lesions (n = 6) demonstrated early and prolonged enhancement and benign lesions (n = 14) showed relatively slow, prolonged enhancement (P < .05). The exophytic masses (n = 6) all were malignant and demonstrated early and prolonged enhancement. Dynamic MRI can help differentiate benign from malignant gallbladder lesions. 相似文献