全文获取类型
收费全文 | 28614篇 |
免费 | 2072篇 |
国内免费 | 90篇 |
专业分类
耳鼻咽喉 | 345篇 |
儿科学 | 727篇 |
妇产科学 | 649篇 |
基础医学 | 3786篇 |
口腔科学 | 762篇 |
临床医学 | 3248篇 |
内科学 | 6701篇 |
皮肤病学 | 317篇 |
神经病学 | 2622篇 |
特种医学 | 1054篇 |
外科学 | 3605篇 |
综合类 | 437篇 |
一般理论 | 55篇 |
预防医学 | 2331篇 |
眼科学 | 722篇 |
药学 | 1762篇 |
中国医学 | 17篇 |
肿瘤学 | 1636篇 |
出版年
2022年 | 165篇 |
2021年 | 373篇 |
2020年 | 236篇 |
2019年 | 345篇 |
2018年 | 412篇 |
2017年 | 318篇 |
2016年 | 385篇 |
2015年 | 456篇 |
2014年 | 639篇 |
2013年 | 1096篇 |
2012年 | 1407篇 |
2011年 | 1490篇 |
2010年 | 858篇 |
2009年 | 765篇 |
2008年 | 1302篇 |
2007年 | 1410篇 |
2006年 | 1444篇 |
2005年 | 1453篇 |
2004年 | 1497篇 |
2003年 | 1343篇 |
2002年 | 1395篇 |
2001年 | 545篇 |
2000年 | 463篇 |
1999年 | 513篇 |
1998年 | 347篇 |
1997年 | 313篇 |
1996年 | 323篇 |
1995年 | 294篇 |
1994年 | 257篇 |
1993年 | 269篇 |
1992年 | 477篇 |
1991年 | 435篇 |
1990年 | 389篇 |
1989年 | 411篇 |
1988年 | 315篇 |
1987年 | 343篇 |
1986年 | 316篇 |
1985年 | 322篇 |
1984年 | 315篇 |
1983年 | 283篇 |
1982年 | 299篇 |
1981年 | 262篇 |
1980年 | 274篇 |
1979年 | 256篇 |
1978年 | 227篇 |
1977年 | 193篇 |
1976年 | 193篇 |
1975年 | 205篇 |
1974年 | 206篇 |
1973年 | 167篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
74.
Kenneth J. Sher PhD Arthur I. Alterman PhD 《Alcoholism, clinical and experimental research》1988,12(2):233-238
Although Tarter et al.'s (1977) HK/MBD questionnaire has been found useful in subtyping populations of clinical alcoholics, its potential utility in nonclinical populations has yet to be determined. The current study examined the family history, personality, and substance use/abuse correlates of Tarter et al.'s HK/MBD questionnaire and factor analytically derived subscales (Alterman and McLellan, 1986) in a nonclinical sample of 580 young, adult males. In addition, a factor analysis of the HK/MBD questionnaire was undertaken to assess the extent to which the factor structure determined on a clinical alcoholic sample replicates in a nonclinical sample. Results indicated that each of the HK/MBD subscales showed relatively unique patterns of correlations with the various personality measures employed suggesting that they are measuring separate constructs. Perhaps of greatest importance, the HK/MBD items that appear to be of greatest relevance for understanding substance use/abuse are those related to antisocial behavior. Finally, the factor structure of the HK/MBD questionnaire in the nonclinical sample was found to be quite similar to the structure obtained in a clinical sample. These results demonstrate the multidimensional structure of the HK/MBD questionnaire and the utility of using the more homogeneous subscales in research with both clinical and nonclinical samples. 相似文献
75.
Scott L. Nyberg Arthur J. Matas Walter K. Kremers Jeffrey D. Thostenson Timothy S. Larson Mikel Prieto Michael B. Ishitani Sylvester Sterioff Mark D. Stegall 《American journal of transplantation》2003,3(6):715-721
We previously proposed a quantitative approach to assess donor organs for cadaver renal transplantation. To improve on our original scoring system, we studied 34 324 patients who received cadaver renal transplants from adult donors between 1994 and 1999 and were reported to the UNOS Scientific Renal Transplant Registry. A scoring system was developed from five donor variables (age, 0-25 points; history of hypertension, 0-4; creatinine clearance before procurement, 0-4; cause of death, 0-3; HLA mismatch, 0-3) that showed a significant correlation with renal function and long-term graft survival. Cadaver kidneys were stratified by cumulative donor score: grade A, 0-9 points; grade B, 10-19; grade C, 20-29; and grade D, 30-39. The influence of donor score on renal function and graft survival was most severe above 20 points, designated 'marginal' kidneys. In summary, a donor scoring system developed from a large population database was useful in predicting outcome after cadaver renal transplantation. The improved system provides a quantitative approach to evaluation of marginal kidneys and may improve allocation of these organs in cadaver renal transplantation. 相似文献
76.
OBJECTIVE: The aim of the present study was to examine the nature of previously reported deficits in sustained attention and response inhibition in adults with the developmental disorder, phenylketonuria (PKU). METHODS: This study used event-related potentials (ERPs) to examine the performance of PKU adults (n=9) and a matched control group (n=9) on a visual Go-Nogo task. RESULTS: Comparison of behavioural measures between the PKU and control groups failed to reach statistical significance, yet analysis of the ERPs showed statistically significant amplitude reductions in the P1 and N1 components elicited following presentation of stimuli, and a reduction in the amplitude of the N2 component elicited following presentation of Nogo stimuli. CONCLUSIONS: These results suggest that adults with PKU, despite being continuously treated from birth, manifest subtle impairments in distinct aspects of information processing including early sensory processing of visually presented information, as well as impairments in inhibitory functions. SIGNIFICANCE: The results contribute to an understanding of the neurophysiological mechanisms that are implicated in PKU and highlight the sensitivity of ERP techniques for the identification of the loci of information processing deficits in clinical groups. 相似文献
77.
Comparison of Asymmetry in Cerebral Blood Flow Between Brain Hemispheres Using Digital Subtraction Angiography 总被引:2,自引:0,他引:2
Afshin A. Divani PhD Adnan I. Qureshi MD Kenneth R. Hoffman PhD M. Fareed K. Suri MD Jawad F. Kirmani MD 《Journal of neuroimaging》2006,16(2):139-145
BACKGROUND AND PURPOSE: Recently, endovascular techniques have gained significant therapeutic potential for both treatment and prevention of stroke. Cerebral angiography, which is an essential component of these procedures, has been used to provide morphological information regarding condition of blood vessels. In this study, we propose to determine the possibility of acquiring information regarding cerebral blood flow (CBF) in addition to morphologic information from data routinely available during angiography. METHODS: Digital subtraction angiography sequences were obtained for eight patients having occlusive disease in internal carotid artery (ICA) territories. Two regions-of-interest (ROIs) corresponding to the two brain hemispheres on AP view were delineated. For each image, the average pixel value within each ROI was calculated and used to generate time-density curves. Indices obtained from each curve were compared with each other and with the results obtained from the single photon emission computed tomography (SPECT) studies performed a pre- or postangiography procedure. RESULTS: Comparison between ICA stenosis and cerebral perfusion measurements revealed that cerebral perfusion deficit can be independent of arterial occlusive disease. The indices obtained from the time-density curves exhibit a correlating trend with the results from SPECT studies. However, lack of sufficient sample data prevented any meaningful statistical analysis to be conducted. CONCLUSIONS: We have developed a technique for utilizing the angiographic data for the important task of routinely and easily measuring CBF. Availability of CBF measurements during cerebral angiography may favorably impact upon the appropriate use of endovascular procedures and potentially contribute to the reduction of morbidity and mortality associated with stroke. 相似文献
78.
Mitchell S. Cappell M.D. Ph.D. Arthur J. Geller M.D. 《The American journal of gastroenterology》1992,87(7):815-824
The patterns of which human immunodeficiency virus (HIV)-seropositive patients underwent endoscopy for gastrointestinal bleeding at a university hospital were analyzed in 50 consecutive patients admitted from July 1984 through December 1989, and criteria were developed as to which patients are most likely to benefit from endoscopy. Analyzed patient data included the medical records, follow-up until July 1990 obtained by telephone questionnaire in 46 patients, and autopsy findings in the 11 patients undergoing autopsy. Thirty-seven percent of the patients did not undergo endoscopic or radiographic examinations indicated to determine the cause of bleeding. The adequacy of the evaluation was not related to race, intravenous drug abuse, homosexuality, hemophilia, the diagnosis of known AIDS, or being a public patient. In 21 of the 28 cases in which the cause of bleeding was determined, the diagnosed lesions had a specific, effective therapy. The mortality from gastrointestinal bleeding was 39.0%, compared with 8.3% in 48 controls without known HIV infection (p less than 0.001 by Fisher's exact test, odds ratio = 7.0, odds ratio confidence interval = 5.0-9.7). Statistically significant independent predictors of mortality included leukocytosis, concurrent major diseases, intravenous drug abuse, transfusion of 5 or more units of packed erythrocytes, and the presence of a bloody nasogastric aspirate or hematemesis (Wilk's lambda statistic = 0.369, p less than 0.0001). In particular, 10 of 11 patients (89%) with two or more concurrent major diseases died, whereas only three of 24 patients (13%) with no concurrent diseases died during the hospitalization. We conclude a large percentage of HIV-seropositive patients did not undergo a diagnostic evaluation for gastrointestinal bleeding at a university hospital, and there was no discernible rational pattern as to which patients underwent endoscopy. Endoscopy is an important and indicated procedure in HIV-seropositive patients with no or one concomitant major illness. HIV-seropositive patients with gastrointestinal bleeding and two or more concomitant major illnesses have an exceedingly poor prognosis, and are less likely to benefit from invasive diagnostic tests and aggressive therapy. 相似文献
79.
Effect of ethanol on cyclic AMP levels in intact PC12 cells 总被引:4,自引:0,他引:4
Two subclones of the rat pheochromocytoma cell line, PC12, were used to compare the effects of ethanol on adenylate cyclase activity in isolated membranes with its effects on cyclic AMP accumulation in intact cells. Consistent with previous reports, ethanol increased basal and 2-chloroadenosine-stimulated adenylate cyclase activity in isolated membrane preparations from both subclones. However, ethanol had opposite effects on agonist-stimulated cyclic AMP accumulation in intact cells of the two subclones, enhancing accumulation in one subclone, and inhibiting it in the other. The inhibition of cyclic AMP accumulation did not result from stimulation of phosphodiesterase activity, activation of the inhibitory guanyl nucleotide regulatory protein, Gi, or stimulation of protein kinase C. The results indicate that extrapolation of the effects of ethanol from one cell type to another, or from in vitro to in vivo systems, may be complicated by the interaction of ethanol with regulatory processes that influence second messenger systems, and can differ in various types of intact cells. 相似文献
80.
A Franco C Gonzalez O S Levine R Lagos R H Hall S L Hoffman M A Moechtar E Gotuzzo M M Levine D M Hone et al. 《Journal of clinical microbiology》1992,30(8):2187-2190
We examined envelope protein profiles, chromosomal restriction endonuclease digest patterns, and immune responses to envelope proteins for collections of Salmonella typhi strains isolated in Peru and Indonesia. Only minor differences in envelope protein patterns were apparent among strains. Strains from 7 of 20 Indonesian patients had a distinct chromosomal digest pattern compared with patterns of Peruvian and other Indonesian strains. Strains with this pattern carried the gene for the j flagellar antigen (H1-j); differences in response to envelope proteins of j and d strains were noted on immunoblot analysis. Our data suggest that there are genotypic and phenotypic differences among S. typhi strains. The clinical importance of these differences remains to be fully evaluated; however, in this study it was not possible to show a clear correlation between strain characteristics and disease severity. 相似文献