全文获取类型
收费全文 | 38114篇 |
免费 | 2463篇 |
国内免费 | 106篇 |
专业分类
耳鼻咽喉 | 295篇 |
儿科学 | 1263篇 |
妇产科学 | 1035篇 |
基础医学 | 4308篇 |
口腔科学 | 603篇 |
临床医学 | 6632篇 |
内科学 | 6712篇 |
皮肤病学 | 403篇 |
神经病学 | 3660篇 |
特种医学 | 784篇 |
外国民族医学 | 1篇 |
外科学 | 3824篇 |
综合类 | 404篇 |
现状与发展 | 1篇 |
一般理论 | 66篇 |
预防医学 | 5248篇 |
眼科学 | 495篇 |
药学 | 2282篇 |
中国医学 | 35篇 |
肿瘤学 | 2632篇 |
出版年
2023年 | 212篇 |
2022年 | 371篇 |
2021年 | 695篇 |
2020年 | 486篇 |
2019年 | 757篇 |
2018年 | 927篇 |
2017年 | 638篇 |
2016年 | 717篇 |
2015年 | 762篇 |
2014年 | 1139篇 |
2013年 | 1811篇 |
2012年 | 2552篇 |
2011年 | 2721篇 |
2010年 | 1450篇 |
2009年 | 1272篇 |
2008年 | 2473篇 |
2007年 | 2660篇 |
2006年 | 2478篇 |
2005年 | 2474篇 |
2004年 | 2300篇 |
2003年 | 2201篇 |
2002年 | 2113篇 |
2001年 | 454篇 |
2000年 | 400篇 |
1999年 | 485篇 |
1998年 | 450篇 |
1997年 | 382篇 |
1996年 | 314篇 |
1995年 | 339篇 |
1994年 | 276篇 |
1993年 | 256篇 |
1992年 | 315篇 |
1991年 | 322篇 |
1990年 | 308篇 |
1989年 | 274篇 |
1988年 | 256篇 |
1987年 | 243篇 |
1986年 | 215篇 |
1985年 | 228篇 |
1984年 | 214篇 |
1983年 | 214篇 |
1982年 | 205篇 |
1981年 | 200篇 |
1980年 | 171篇 |
1979年 | 126篇 |
1978年 | 141篇 |
1977年 | 100篇 |
1976年 | 67篇 |
1975年 | 58篇 |
1974年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Cannabis remains the most widely used illegal drug in the United States. This update examines the available literature on neuroimaging studies of the brains of cannabis users. The majority of studies examining the acute effects of delta-9-tetrahydrocannabinol (THC) administration used PET methods and concluded that administration of THC leads to increased activation in frontal and paralimbic regions and the cerebellum. These increases in activation are broadly consistent with the behavioral effects of the drug. Although there is only equivocal evidence that chronic cannabis use might result in structural brain changes, blood-oxygenation-level-dependent-fMRI studies in chronic users consistently show alterations, or neuroadaptation, in the activation of brain networks responsible for higher cognitive functions. It is not yet certain whether these changes are reversible with abstinence. Given the high prevalence of cannabis use among adolescents, studies are needed to evaluate whether cannabis use might affect the developing brain. Considerable further work, employing longitudinal designs, is also required to determine whether cannabis use causes permanent functional alterations in the brains of adults. 相似文献
33.
Cystic Fibrosis has effects on many body systems, including the skeletal system. In this case, we describe the impact of respiratory and endocrine disease on bone healing following orthopedic trauma in a 22-year-old woman. Limitations to mobility resulting from trauma complicated her respiratory condition. Disease-related effects on bone health and healing delayed her recovery from the trauma. It is important to recognize the multisystemic nature of CF, even when managing acute orthopedic injuries. 相似文献
34.
Bernhard L mmle Mauro Berrettini Hans Peter Schwarz Mary Jo Heeb John B. Griffin 《Thrombosis research》1986,41(6):747-759
The immunoblotting technique was applied to the study of Factor XII (F.XII) in plasma. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of whole plasma followed by electroblotting of the electropherograms to nitrocellulose (NC) membranes and immunologic detection by a double antibody technique was used. 125-F.XII was transferred to the NC membrane in amounts proportional to the amount applied to the gel provided that a constant amount of carrier protein was present. Based on this, a quantitative assay was developed using either normal plasma or F.XII dilutions in F.XII-deficient plasma as standards. The measurement of F.XII antigen by immunoblotting was reproducible and gave values similar to those obtained by radial immunodiffusion. Two normal plasma pools contained 26 and 29 μ/ml of F.XII according to the immunoblotting assay. Compared to other immunoassays, immunoblotting has the advantage of directly estimating the apparent molecular weight (MW) of the protein of interest. Thus, we could confirm the normal apparent MW (80,000) of a F.XII-like molecule previously isolated from a cross reacting material (CRM)-positive F.XII-deficient plasma. None of eight CRM-negative F.XII-deficient plasmas showed an 80,000 MW immunoreactive molecule. However, five of these eight plasmas had a faint autoradiographic band at 115,000 MW that was similarly seen in only three out of 43 individual normal plasmas. The nature of this 115,000 MW band remains to be defined. 相似文献
35.
David Berrigan Linda W Pickle Jennifer Dill 《International journal of health geographics》2010,9(1):20
Background
Past studies of associations between measures of the built environment, particularly street connectivity, and active transportation (AT) or leisure walking/bicycling have largely failed to account for spatial autocorrelation of connectivity variables and have seldom examined both the propensity for AT and its duration in a coherent fashion. Such efforts could improve our understanding of the spatial and behavioral aspects of AT. We analyzed spatially identified data from Los Angeles and San Diego Counties collected as part of the 2001 California Health Interview Survey. 相似文献36.
The trypanosome responsible for the majority of cases of human trypanosomiasis in Africa is Group 1 Trypanosoma brucei gambiense. Currently the most reliable test for the parasite is based on a single gene, which encodes a 47 kDa receptor-like T. b. gambiense-specific glycoprotein, TgsGP, expressed in the flagellar pocket of bloodstream forms. Although TgsGP has been demonstrated in T. b. gambiense throughout its geographic range, similar genes have been demonstrated in other T. brucei sspp. isolates, and there are no data on the extent of sequence variation in TgsGP. Here we have carried out a comparison of TgsGP sequences in a range of Group 1 T. b. gambiense isolates and compared the gene to homologues in other T. brucei sspp. in order to provide information to support the use of this gene as the key identification target for Group 1 T. b. gambiense. We demonstrate that the sequence of TgsGP is well conserved in Group 1 T. b. gambiense across the endemic range of gambian human trypanosomiasis and confirm that this gene is a suitable target for specific detection of this parasite. The TgsGp-like genes in some isolates of T. b. brucei, T. b. rhodesiense and Group 2 T. b. gambiense are closely similar to VSG Tb10.v4.0178, which may be the ancestral gene from which TgsGP was derived. 相似文献
37.
Mark A. Trimble Salvador Borges-Neto Stuart Smallhelser Ji Chen Emily F. Honeycutt Linda K. Shaw Jaekyeong Heo Robert A. Pagnanelli E. Lindsey Tauxe Ernest V. Garcia Fabio Esteves Frank Seghatol-Eslami G. Neal Kay Ami E. Iskandrian 《Journal of nuclear cardiology》2007,14(3):298-307
Background Cardiac resynchronization therapy (CRT) is approved for the treatment of patients with advanced systolic heart failure and
evidence of dyssynchrony on electrocardiograms. However, a significant percentage of patients do not demonstrate improvement
with CRT. Echocardiographic techniques have been used for more accurate determination of dyssynchrony. Single photon emission
computed tomography (SPECT) myocardial perfusion imaging has not previously been used to evaluate cardiac dyssynchrony. The
objective of this study is to evaluate mechanical dyssynchrony as described by phase analysis of gated SPECT images in patients
with left ventricular dysfunction, conduction delays, and ventricular paced rhythms.
Methods and Results A novel count-based method is used to extract regional systolic wall thickening amplitude and phase from gated SPECT images.
Five indices describing the phase dispersion of the onset of mechanical contraction are determined: peak phase, phase SD,
bandwidth, skewness, and kurtosis. These indices were determined in consecutive patients with left ventricular dysfunction
(n=120), left bundle branch block (n=33), right bundle branch block (n=19), and ventricular paced rhythms (n=23) and were
compared with normal control subjects (n=157). Phase SD, bandwidth, skewness, and kurtosis were significantly different between
patients with left ventricular dysfunction, left bundle branch block, right bundle branch block, and ventricular paced rhythms
and normal control subjects (all P<.001) Peak phase was significantly different between patients with right ventricular paced rhythms and normal control subjects
(P=.001).
Conclusions A novel SPECT technique for describing left ventricular mechanical dyssyn-chrony has been developed and may prove useful in
the evaluation of patients for CRT.
This study was funded in part by a research grant from the Medtronic-Duke Strategic Alliance, of which Dr Borges-Neto is the
primary investigator. 相似文献
38.
Linda V Walsh 《Journal of transcultural nursing》2006,17(2):148-154
Childbearing women and infants in developing countries continue to experience unacceptably high rates of mortality and morbidity in spite of targeted initiatives to address the problem. The aim of this study was to identify the beliefs and rituals of traditional birth attendants (TBAs) in one indigenous Guatemalan community to better understand the cultural influences on perinatal care practices. Ethnographic methods were used to increase understanding of the practice of 10 Mayan TBAs. Three themes were constructed: sacred calling, sacred knowledge and sacred ritual. 相似文献
39.
Jack D Griffin 《Practical procedures & aesthetic dentistry》2008,20(1):39-45; quiz 47
Visualization and pre-operative plan are critical to efficient and thorough case preparation. Congenitally missing teeth, coupled with improper tooth positioning, can compromise the aesthetic rehabilitation outcome. Utilizing pre-treatment digital photography as an outline for tooth reduction and laser tissue re-contouring may help to create a symmetric and pleasing smile, even under less ideal conditions. 相似文献
40.
Barbara Bruemmer Author Vitae Jeffrey HarrisAuthor Vitae Phil GleasonAuthor Vitae Carol J. BousheyAuthor Vitae Patricia M. SheeanAuthor Vitae Sujata ArcherAuthor Vitae Linda Van HornAuthor Vitae 《Journal of the American Dietetic Association》2009,109(10):1728-1737
The use of epidemiologic research designs and analytical methods is common in dietetics research. Food and nutrition professionals who seek to perform evidence-based practice or participate in research design, analysis, and communication need skills in the essentials of epidemiology. This is one of a series of monographs on research methodology that addresses these needs and supports the goals of the Board of Editors of the Journal of the American Dietetic Association to further enhance competency and skills. This monograph focuses on statistical approaches for univariate analyses used with the primary observational study designs associated with epidemiology. Tables illustrating the presentation and interpretation of these results are included. 相似文献