全文获取类型
收费全文 | 35461篇 |
免费 | 2805篇 |
国内免费 | 75篇 |
专业分类
耳鼻咽喉 | 429篇 |
儿科学 | 1308篇 |
妇产科学 | 858篇 |
基础医学 | 4993篇 |
口腔科学 | 957篇 |
临床医学 | 3637篇 |
内科学 | 7007篇 |
皮肤病学 | 486篇 |
神经病学 | 3210篇 |
特种医学 | 1318篇 |
外科学 | 5124篇 |
综合类 | 661篇 |
一般理论 | 55篇 |
预防医学 | 3247篇 |
眼科学 | 656篇 |
药学 | 2259篇 |
1篇 | |
中国医学 | 25篇 |
肿瘤学 | 2110篇 |
出版年
2021年 | 492篇 |
2020年 | 321篇 |
2019年 | 533篇 |
2018年 | 579篇 |
2017年 | 459篇 |
2016年 | 459篇 |
2015年 | 580篇 |
2014年 | 832篇 |
2013年 | 1227篇 |
2012年 | 1698篇 |
2011年 | 1842篇 |
2010年 | 1035篇 |
2009年 | 867篇 |
2008年 | 1758篇 |
2007年 | 1863篇 |
2006年 | 1806篇 |
2005年 | 1812篇 |
2004年 | 1702篇 |
2003年 | 1693篇 |
2002年 | 1524篇 |
2001年 | 846篇 |
2000年 | 805篇 |
1999年 | 724篇 |
1998年 | 414篇 |
1997年 | 359篇 |
1996年 | 356篇 |
1995年 | 365篇 |
1994年 | 355篇 |
1993年 | 309篇 |
1992年 | 678篇 |
1991年 | 633篇 |
1990年 | 602篇 |
1989年 | 615篇 |
1988年 | 577篇 |
1987年 | 487篇 |
1986年 | 491篇 |
1985年 | 570篇 |
1984年 | 478篇 |
1983年 | 437篇 |
1982年 | 326篇 |
1981年 | 316篇 |
1980年 | 276篇 |
1979年 | 325篇 |
1978年 | 333篇 |
1977年 | 252篇 |
1976年 | 269篇 |
1975年 | 285篇 |
1974年 | 259篇 |
1973年 | 305篇 |
1972年 | 234篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Unusual viral infections (progressive multifocal leukoencephalopathy and cytomegalovirus disease) after high-dose chemotherapy with autologous blood stem cell rescue and peritransplantation rituximab 下载免费PDF全文
Goldberg SL Pecora AL Alter RS Kroll MS Rowley SD Waintraub SE Imrit K Preti RA 《Blood》2002,99(4):1486-1488
Efforts to reduce relapse of non-Hodgkin lymphoma after autologous transplantation have included ex vivo stem cell selection and/or peritransplantation immunotherapy. The late infectious and immunologic consequences of these maneuvers are not well understood, although an increase in early cytomegaloviral disease after CD34(+) stem cell selection and an alteration in immunoglobulin and T-cell recovery after peritransplantation rituximab has been noted. We report the first 2 cases of progressive multifocal leukoencephalopathy caused by JC papovavirus after autologous peripheral blood stem cell transplantation and a case each of cytomegalovirus retinitis and pneumonitis. All 4 patients experienced significant impairment of CD4 T-cell recovery, placing them at risk for these unusual viral infections. The clustering of cases is concerning because all occurred shortly after the introduction of peritransplantation rituximab into treatment protocols (4 of 62 immunotherapy recipients compared with 0 of 276 without; z = 3.595; P <.001), although a direct association with this CD20 B-cell-directed therapy remains speculative. 相似文献
992.
Markus Goldschmiedt MD Walter L. Peterson MD Ricardo Spielberger MD Edward L. Lee MD Stanley F. Kurtz MD PhD Mark Feldman MD 《Digestive diseases and sciences》1989,34(8):1285-1289
Summary Achalasia secondary to malignancy is rare, with most cases associated with gastric adenocarcinoma of the gastroesophageal junction. This report describes the clinicopathologic features of a 64-year-old man found to have mesothelioma as the cause of secondary achalasia. To our knowledge, this is the first case of secondary achalasia produced by a mesothelioma. We reviewed the English literature in regard to achalasia induced by tumors.This work was supported by the Veterans Administration. 相似文献
993.
Anti-ischemic effects of atenolol versus nifedipine in patients with coronary artery disease and ambulatory silent ischemia 总被引:1,自引:0,他引:1
P C Deedwania E V Carbajal J R Nelson H Hait 《Journal of the American College of Cardiology》1991,17(4):963-969
The anti-ischemic effects of atenolol and nifedipine were compared in a randomized double-blind crossover manner in 24 patients with stable exertional angina and transient silent ischemia during ambulatory electrocardiographic (ECG) monitoring. Both atenolol and nifedipine were effective (p less than 0.005) in reducing the average number and duration of transient ischemic events, but therapy with atenolol was associated with a significantly greater reduction in the mean number (p less than 0.05) and duration (p less than 0.01) of silent ischemic events. Analyses of the silent ischemic activity during the morning hours revealed that only therapy with atenolol produced a significant reduction in the average duration per patient (139 +/- 54 vs. 1,609 +/- 468 s, p less than 0.01) and in the average duration of silent ischemia per event between 6 AM and 12 noon (62 +/- 21 vs. 208 +/- 24 s, p less than 0.005). There were fewer adverse experiences during therapy with atenolol. These results show that although both atenolol and nifedipine are effective in reducing silent ischemic events, treatment with atenolol is associated with significantly greater efficacy, particularly on the morning surge of silent myocardial ischemia. 相似文献
994.
995.
Targeting and crossing of the human maternofetal barrier by Listeria monocytogenes: role of internalin interaction with trophoblast E-cadherin 下载免费PDF全文
Lecuit M Nelson DM Smith SD Khun H Huerre M Vacher-Lavenu MC Gordon JI Cossart P 《Proceedings of the National Academy of Sciences of the United States of America》2004,101(16):6152-6157
Listeria monocytogenes produces severe fetoplacental infections in humans. How it targets and crosses the maternofetal barrier is unknown. We used immunohistochemistry to examine the location of L. monocytogenes in placental and amniotic tissue samples obtained from women with fetoplacental listeriosis. The results raised the possibility that L. monocytogenes crosses the maternofetal barrier through the villous syncytiotrophoblast, with secondary infection occurring via the amniotic epithelium. Because epidemiological studies indicate that the bacterial surface protein, internalin (InlA), may play a role in human fetoplacental listeriosis, we investigated the cellular patterns of expression of its host receptor, E-cadherin, at the maternofetal interface. E-cadherin was found on the basal and apical plasma membranes of syncytiotrophoblasts and in villous cytotrophoblasts. Established trophoblastic cell lines, primary trophoblast cultures, and placental villous explants were each exposed to isogenic InlA+ or InlA- strains of L. monocytogenes, and to L. innocua expressing or not InlA. Quantitative assays of cellular invasion demonstrated that bacterial entry into syncytiotrophoblasts occurs via the apical membrane in an InlA-E-cadherin dependent manner. In human placental villous explants, bacterial invasion of the syncytiotrophoblast barrier and underlying villous tissue and subsequent replication produces histopathological lesions that mimic those seen in placentas of women with listeriosis. Thus, the InlA-E-cadherin interaction that plays a key role in the crossing of the intestinal barrier in humans is also exploited by L. monocytogenes to target and cross the placental barrier. Such a ligand-receptor interaction allowing a pathogen to specifically cross the placental villous trophoblast barrier has not been reported previously. 相似文献
996.
RNA splicing permits expression of a maize gene with a defective Suppressor-mutator transposable element insertion in an exon. 总被引:12,自引:1,他引:12 下载免费PDF全文
997.
Quantitative histological study of enteropathy associated with HIV infection. 总被引:6,自引:3,他引:6 下载免费PDF全文
A quantitative histological study was performed on small intestinal biopsies from eight ambulatory patients with HIV infection (AIDS/AIDS-related complex, ARC) and compared with those from 16 normal subjects. Enteropathy was assessed by measurement of villus area, crypt length and mitotic count, as well as duodenal counts of intraepithelial lymphocytes, mucosal mast cells and goblet cells. Enteropathy in subjects with AIDS/ARC was shown by reduced mean villus area of 0.363 (SD 0.081) compared with 0.500 (SD 0.064) mm2 in control subjects (p less than 0.0001), while intestinal crypts were of similar length with 239 (SD 36) compared with 225 (SD 28 microns, but mitotic count was increased to 3.8 (SD 1.2) compared with 2.4 (SD 0.8) (p = 0.01) in the same control subjects. These results indicate villous atrophy with impaired crypt hyperplasia. Duodenal cell counts showed similar numbers of mucosal mast cells, intraepithelial lymphocytes and goblet cells in AIDS/ARC patients and fifteen control subjects. 相似文献
998.
Oscar J. Hines MD Anton J. Bilchik MD PhD David W. Mcfadden MD Paula J. Rodgers MD Norman Bautista MD Michael J. Zinner MD Dr. Stanley W. Ashley MD 《Digestive diseases and sciences》1995,40(4):774-780
Feeding stimulates fluid and electrolyte absorption in the small intestine. Previous studies have suggested that Na+/glucose cotransport is important in initiating this response in the jejunum. The purpose of this study was to determine whether Na+/H+ exchange plays a role in meal-induced absorption. Exteriorized, neurovascularly intact jejunal and ileal loops (25 cm) were constructed in dogs. Following a two-week period of postoperative recovery, the loops of awake dogs were perfused with standard buffer alone or with increasing concentrations of amiloride, a Na+/H+ exchange inhibitor. Water, sodium, and chloride fluxes were calculated following a meal using [14C]PEG as a volume marker. The meal significantly increased absorption in both the jejunum (P<0.001) and ileum (P<0.01) in those animals perfused with buffer alone. More significantly, amiloride suppressed the increased absorption seen following a meal in the ileum (P<0.001) but not the jejunum. The response in the ileum was dose dependent. These findings suggest that a major mediator of postprandial sodium and water absorption in the ileum is the Na+/H+ exchanger.Supported by NIH R29-DK-47326 (S.W.A.), R01-DK-39879 (M.J.Z.), and a VA Merit Review (D.W.M.).Portions of this work were presented at the Annual Meeting of the American Gastroenterological Association, May 1993, Boston, Massachusetts. 相似文献
999.
Clinical Characteristics and Outpatient Mental Health Service Use of Transition-Age Youth in the USA
Kathleen J. Pottick PhD Lynn A. Warner PhD Ann Vander Stoep PhD Nelson M. Knight BA 《The journal of behavioral health services & research》2014,41(2):230-243
This study examines diagnostic and service utilization patterns of transition-age youth in outpatient care derived from the 2007 nationally representative Client/Patient Sample Survey. Comparisons between 16–17, 18–21, and 22–25 year olds are highlighted. Among transition-age outpatients, the oldest youth had the highest rates of depression and bipolar disorder and co-occurring medical and substance use problems. Controlling for sociodemographic and clinical characteristics, 18–21 year olds were less likely to receive individual therapy than 16–17 year olds, but there were no age group differences in receipt of specialized therapy or psychotropic medication. Female gender and Hispanic ethnicity were positively associated with the number of services received and specialized service use, respectively; youth with private insurance were more likely than those with public insurance to receive psychotropic medication. Implications are discussed regarding access to and adequacy of services provided for young people in the critical transition to adulthood, especially with the implementation of the 2010 Affordable Care Act. 相似文献
1000.
Wendy R. Galpern Christopher S. Coffey Alberto Albanese Ken Cheung Cynthia L. Comella Dixie J. Ecklund Stanley Fahn Joseph Jankovic Karl Kieburtz Anthony E. Lang Michael P. McDermott Jeremy M. Shefner Jan K. Teller John L. P. Thompson Sharon D. Yeatts H. A. Jinnah 《Neurotherapeutics》2014,11(1):117-127
With advances in the understanding of the pathophysiology of dystonia, novel therapeutics are being developed. Such therapies will require clinical investigation ranging from exploratory studies to examine safety, tolerability, dosage selection, and preliminary efficacy to confirmatory studies to evaluate efficacy definitively. As dystonia is a rare and complex disorder with clinical and etiological heterogeneity, clinical trials will require careful consideration of the trial design, including enrollment criteria, concomitant medication use, and outcome measures. Given the complexities of designing and implementing efficient clinical trials, it is important for clinicians and statisticians to collaborate closely throughout the clinical development process and that each has a basic understanding of both the clinical and statistical issues that must be addressed. To facilitate designing appropriate clinical trials in this field, we review important general clinical trial and regulatory principles, and discuss the critical components of trials with an emphasis on considerations specific to dystonia. Additionally, we discuss designs used in early exploratory, late exploratory, and confirmatory phases, including adaptive designs. 相似文献