全文获取类型
收费全文 | 47832篇 |
免费 | 4389篇 |
国内免费 | 80篇 |
专业分类
耳鼻咽喉 | 613篇 |
儿科学 | 1281篇 |
妇产科学 | 1323篇 |
基础医学 | 6862篇 |
口腔科学 | 1260篇 |
临床医学 | 5834篇 |
内科学 | 8315篇 |
皮肤病学 | 623篇 |
神经病学 | 3783篇 |
特种医学 | 2144篇 |
外国民族医学 | 1篇 |
外科学 | 6249篇 |
综合类 | 1116篇 |
一般理论 | 23篇 |
预防医学 | 5269篇 |
眼科学 | 1090篇 |
药学 | 3560篇 |
2篇 | |
中国医学 | 56篇 |
肿瘤学 | 2897篇 |
出版年
2021年 | 656篇 |
2019年 | 643篇 |
2018年 | 750篇 |
2017年 | 629篇 |
2016年 | 610篇 |
2015年 | 727篇 |
2014年 | 947篇 |
2013年 | 1475篇 |
2012年 | 2150篇 |
2011年 | 2224篇 |
2010年 | 1231篇 |
2009年 | 1022篇 |
2008年 | 1890篇 |
2007年 | 2050篇 |
2006年 | 2060篇 |
2005年 | 2038篇 |
2004年 | 1870篇 |
2003年 | 1689篇 |
2002年 | 1722篇 |
2001年 | 1614篇 |
2000年 | 1723篇 |
1999年 | 1464篇 |
1998年 | 657篇 |
1997年 | 537篇 |
1996年 | 549篇 |
1995年 | 540篇 |
1994年 | 455篇 |
1993年 | 442篇 |
1992年 | 1260篇 |
1991年 | 1165篇 |
1990年 | 1151篇 |
1989年 | 1072篇 |
1988年 | 996篇 |
1987年 | 996篇 |
1986年 | 918篇 |
1985年 | 912篇 |
1984年 | 719篇 |
1983年 | 626篇 |
1982年 | 445篇 |
1981年 | 391篇 |
1980年 | 401篇 |
1979年 | 655篇 |
1978年 | 522篇 |
1977年 | 412篇 |
1976年 | 401篇 |
1975年 | 374篇 |
1974年 | 451篇 |
1973年 | 438篇 |
1972年 | 450篇 |
1971年 | 423篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
E.M. Smith Ph.D. S.R. Johnson M.D. E.J. Figuerres M.S. M. Mendoza M.S. D. Fedderson B.S. T.H. Haugen M.D. L.P. Turek M.D. 《Gynecologic oncology》1997,65(3):441-446
Postmenopausal women enrolled in the Iowa portion of the postmenopausal estrogen/progestin interventions randomized clinical trial (n= 105) during 1989–1991 were studied for (i) the prevalence of human papillomavirus (HPV) in this older age population (ages 45–64), and (ii) the association between hormone replacement therapies (HRTs) and changes in detection of HPV over a 2-year time period. HPV is causative in most cervical and some other genital cancers and in the presence of steroid hormones has been shown to increase neoplastic transformation by HPVin vitro.Using PCR to detect HPV DNA, the overall frequency of the virus regardless of time period was 50.3% (n= 53) with a baseline (BL) frequency of 38.1% and the second year follow-up (FU) of 22.9%. The oncogenic types HPV-16 (75.5%) and HPV-31 (20.8%) were the most commonly reported. All those with persistently detected infection (10.5%), defined as HPV+ at both BL and FU, were identified with HPV-16 or -18. Between these two time periods there were no significant differences in HPV frequency between the placebo and combined HRT groups (BL−/FU+, 21% vs 18%; BL+/FU−, 71% vs 80%). While the study is based on a small sample, the findings suggest that short-term use of HRTs is not associated with an increased risk of HPV detection, but assessment of effects from long-term use is needed. The data also indicate that the frequency of HPV found in older women is higher than previously suspected but that short-term changes in HPV detected in this age group are unrelated to the development of precancerous cervical lesions. 相似文献
103.
104.
J. Keith Smith M.D. Ph.D. Gordon C. Carson III M.D. Jay D. Johnson B.S. John H. Harris Jr. M.D. D.Sc. F.A.C.R. 《Emergency radiology》1994,1(2):78-80
Purpose: To describe an educational computer aided instruction program dealing with diagnosis and classification of facial
fractures.
Methods: A program was created for use on Macintosh computers using a graphic presentation package. This program allows for
the display of high resolution digitized radiographic images and illustrations, along with integrated voice and text information.
Users can interact with the program to review complex concepts or study additional cases. Case material was obtained from
selected high quality plain radiographs and computed tomography (CT) scans obtained in the trauma center of one institution,
and was scanned on a high resolution digital scanner with image parameters optimized for viewing on the Macintosh high resolution
color monitor.
Results: The program has been installed in the computer aided instructional laboratories or trauma centers at The University
of Texas Health Science Center, Houston; The University of Alabama, Birmingham; Emory University School of Medicine, Atlanta,
Georgia; and The University of North Carolina, Chapel Hill. The program is available to radiology residents and medical students
rotating on the trauma radiology services at these institutions. Completion of the program requires 30–45 minutes.
Conclusion: Based on our initial experience, the program has been used by residents in the training programs of all institutions
with favorable results. 相似文献
105.
R. Ehrlich R. J. Wenning G. W. Johnson S. H. Su D. J. Paustenbach 《Archives of environmental contamination and toxicology》1994,27(4):486-500
The identity and relative contributions of various sources of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) to recently deposited sediments collected in Newark Bay and its major tributaries were determined using polytopic vector analysis (PVA), a multivariate statistical technique relatively new in the chemometric literature. The concentrations of 2,3,7,8-substituted PCDD/Fs were assayed in eighty-one surface and near-surface sediment samples collected from the Passaic River, Hackensack River, Arthur Kill, Elizabeth River, Kill Van Kull, Port Elizabeth, and Port Newark navigation channels and Robins Reef, which is located in New York Harbor. PVA modeling revealed five predominant 2,3,7,8-substituted PCDD/F fingerprint patterns in geographically plausible distributions throughout the estuary. This was consistent with the current understanding of hydrodynamic and sedimentation conditions reported in the literature for Newark Bay. Three patterns contained 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), which is alleged to originate from a single industrial source on the lower Passaic River. One of the fingerprints containing 2,3,7,8-TCDD was present in moderate proportions (10–20%) in surface sediments near the site, but was generally observed in low abundance (<5%) elsewhere in the estuary. A fingerprint pattern characteristic of PCDD/F profiles in effluents from municipal sewage and waste water treatment plants was widely distributed in the estuary, but reached its highest relative proportions in the Elizabeth River. A third fingerprint pattern was highest in the Arthur Kill and lower Passaic River and closely matched the residue patterns found in several types of combustion sources. A fourth finger-print pattern in Hackensack River and lower Passaic River sediment matched the PCDD/F profile reported in PCB Aroclor® formulations. A fifth fingerprint pattern matched the profile in recycled pulp and paper mill effluents and was highest in Kill van Kull and upper Passaic River sediment. The majority of PCDD/Fs in sediment from Reaches B, C, and D of Port Newark and Port Elizabeth were attributable to sediments transported via the Arthur Kill and the Kill Van Kull. These results are consistent with those previously reported using principal components analysis, which indicated that 2,3,7,8-substituted PCDD/F patterns in the sediments of Newark Bay are consistent with discharges from multiple sources. 相似文献
106.
107.
R J Landreneau S R Hazelrigg P F Ferson J A Johnson W Nawarawong T M Boley J J Curtis C M Bowers D B Herlan R D Dowling 《The Annals of thoracic surgery》1992,54(3):415-9; discussion 419-20
Advances in endoscopic surgical equipment and laser technology have expanded the role of thoracoscopy to include thoracoscopic pulmonary resection. Eighty-five thoracoscopic pulmonary resections were performed on 61 consecutive patients with small lesions (less than 3 cm) in the outer third of the lung. Patients with preoperative histologic evidence of bronchogenic carcinoma were excluded unless there was impairment of cardiopulmonary function, advanced age, or concomitant extrathoracic malignancy. These thoracoscopic pulmonary resections were accomplished with the neodymium:yttrium-aluminum garnet laser (31), endoscopic stapler (29), or both (25). The mean diameter of the lesions was 1.3 cm (range, 0.4 to 2.7 cm). There has been one late death (38th postoperative day) unrelated to the operation. Morbidity consisted of postoperative atelectasis (2), pneumonia (2), bleeding requiring transfusion (1), and bronchopleural fistula of greater than 7 days duration (3). There were no wound problems. The mean period of chest tube drainage was 3.3 +/- 3.0 days. Mean postoperative stay was 5.7 +/- 4.9 days. The pathologic diagnosis was benign disease in 28 patients (interstitial fibrosis/pneumonitis, 15; radiation fibrosis, 1; sclerosing hemangioma, 1; rheumatoid nodules, 1; granuloma, 2; nocardia, 1; infarct, 1; hamartoma, 4; scar, 1; cytomegalovirus pneumonia, 1), metastatic malignancy in 20 patients, and bronchogenic carcinoma in 13 patients. Five patients found at thoracoscopic pulmonary resection to have bronchogenic cancer had adequate pulmonary function and therefore underwent formal segmentectomy (3) or lobectomy (2). Thoracoscopic pulmonary resection was the only operation performed on patients with benign disease, patients with metastatic lesions, and selected patients with limited stage bronchogenic carcinoma at increased risk for thoracotomy.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
108.
109.
Janice C Probst Sarah B Laditka Jong-Yi Wang Andrew O Johnson 《BMC health services research》2007,7(1):40
Background
Travel burden is a key element in conceptualizing geographic access to health care. Prior research has shown that both rural and minority populations bear disproportionate travel burdens. However, many studies are limited to specific types of patient or specific locales. The purpose of our study was to quantify geographic and race-based differences in distance traveled and time spent in travel for medical/dental care using representative national data. 相似文献110.
We examined the correlates of self-reported lifetime use of alcohol, marijuana, amphetamines, and cocaine within a sample of almost 7,000 high school sophomores in Arizona and Utah. Correlates of drug use (including parental attachment, religious attachment, educational attachment, conventional values, and drug-using friends) showed very similar patterns by gender, with some interesting differences by location. Drug-using friends are by far the best predictor of drug use for both males and females in Arizona and Utah. 相似文献