全文获取类型
收费全文 | 159037篇 |
免费 | 10794篇 |
国内免费 | 630篇 |
专业分类
耳鼻咽喉 | 1772篇 |
儿科学 | 3910篇 |
妇产科学 | 2655篇 |
基础医学 | 20981篇 |
口腔科学 | 3395篇 |
临床医学 | 15573篇 |
内科学 | 33674篇 |
皮肤病学 | 3253篇 |
神经病学 | 14642篇 |
特种医学 | 6981篇 |
外国民族医学 | 14篇 |
外科学 | 25254篇 |
综合类 | 1957篇 |
一般理论 | 110篇 |
预防医学 | 11821篇 |
眼科学 | 3309篇 |
药学 | 10141篇 |
中国医学 | 239篇 |
肿瘤学 | 10780篇 |
出版年
2023年 | 886篇 |
2022年 | 1496篇 |
2021年 | 3385篇 |
2020年 | 2082篇 |
2019年 | 3126篇 |
2018年 | 3606篇 |
2017年 | 2807篇 |
2016年 | 3144篇 |
2015年 | 3591篇 |
2014年 | 5100篇 |
2013年 | 6871篇 |
2012年 | 10343篇 |
2011年 | 11024篇 |
2010年 | 6314篇 |
2009年 | 6024篇 |
2008年 | 9754篇 |
2007年 | 10203篇 |
2006年 | 10107篇 |
2005年 | 10161篇 |
2004年 | 9321篇 |
2003年 | 8628篇 |
2002年 | 8273篇 |
2001年 | 2155篇 |
2000年 | 1846篇 |
1999年 | 2136篇 |
1998年 | 1929篇 |
1997年 | 1551篇 |
1996年 | 1333篇 |
1995年 | 1251篇 |
1994年 | 1125篇 |
1993年 | 1019篇 |
1992年 | 1296篇 |
1991年 | 1195篇 |
1990年 | 1036篇 |
1989年 | 978篇 |
1988年 | 915篇 |
1987年 | 890篇 |
1986年 | 888篇 |
1985年 | 867篇 |
1984年 | 927篇 |
1983年 | 795篇 |
1982年 | 960篇 |
1981年 | 860篇 |
1980年 | 728篇 |
1979年 | 654篇 |
1978年 | 646篇 |
1977年 | 534篇 |
1976年 | 514篇 |
1974年 | 511篇 |
1973年 | 449篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
M M Smith J E Thompson D Thomas M Castillo D Carrier S K Mukherji D Gilliam 《AJNR. American journal of neuroradiology》1997,18(2):327
Choristomas, masses of normal tissues in aberrant locations, contain smooth muscle fibers and fibrous tissues. We describe the MR imaging features of two choristomas located in the internal auditory canals and arising from the facial and vestibulocochlear nerves. Both lesions enhanced with contrast material. In one case, enhancement was seen in the geniculate ganglion and greater superficial petrosal nerve. In the other, a medial component enhanced less than the lateral component did. 相似文献
32.
33.
Stephen R. Thomas Ronald G. Pratt Ronald W. Millard R. C. Samaratunga Yoseph Shiferaw Leland C. Clark Richard E. Hoffmann 《Journal of magnetic resonance imaging : JMRI》1994,4(4):631-635
Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local Po2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant Po2, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T. 相似文献
34.
Thomas Donohue Morton J. Kern Richard Bach Frank Aguirre Thomas Wolford 《Catheterization and cardiovascular interventions》1993,28(2):155-161
The vasomotor response of native human collateral vessels to pharmacologic or hemodynamic vasodilatory stimuli is not well known. We describe a case where retrograde collateral flow velocity was measured both at baseline and following selected hemodynamic and pharmacologic interventions. This index case represents the first in a series of potential human physiologic studies designed to address questions pertaining to control of collateral blood supply in humans. © 1993 Wiley-Liss, Inc. 相似文献
35.
36.
37.
P Thomas 《British journal of hospital medicine》1990,44(2):133-135
38.
Kevin L. Greason M.D. Jose A. Acosta M.D. Thomas J. Magrino M.D. Moogil Choe M.D. 《Diseases of the colon and rectum》1996,39(6):702-704
PURPOSE: This study was undertaken to clarify the importance of bleeding vascular ectasia of the colon as the etiology of massive lower gastrointestinal hemorrhage in patients 40 years of age or younger. METHODS: An otherwise healthy 21-year-old male was admitted to a tertiary medical center with massive lower gastrointestinal hemorrhage. Technetium-labeled red blood cell scan, selective visceral angiography, and colonoscopy identified the source of bleeding as vascular abnormality of the descending colon. Segmental colonic resection was performed. RESULTS: Histologic review of the specimen demonstrated a vascular ectasia. The patient recovered uneventfully and has had no further stigmata of hemorrhage. A review of the literature was undertaken to make clear the significance of vascular ectasia as the source for massive colonic hemorrhage in the young adult. CONCLUSION: This is the first report that documents histologically a vascular ectasia as the source of massive lower gastrointestinal hemorrhage in an otherwise healthy patient less than 40 years of age. Vascular ectasia is an uncommon cause of lower gastrointestinal hemorrhage in the young adult.The Chief, Bureau of Medicine and Surgery, Navy Department, Washington, DC, Clinical Investigation Program sponsored this report #84-16-1968-532, as required by HSETCINST 6000.41A. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government. 相似文献
39.
Peter E Murray Thomas W Smyth Imad About Remeille Remusat Jean-Claude Franquin Anthony J Smith 《Journal of dentistry》2002,30(1):29-36
OBJECTIVES: The incidence of bacterial microleakage, pulp inflammation and necrosis associated with dentine etching treatments prior to restoration are not known. Consequently, to resolve some of the controversy surrounding the effects and importance of vital dentine etching, the authors investigated these factors. METHODS: 110 standardised class V cavities were cut into buccal dentine, without exposing the pulp of teeth scheduled for extraction for orthodontic reasons. Cavities were either left unetched, or etched with the non-equivalent treatments of phosphoric acid gel for 60s or Ethylenediaminetetraacetic acid (EDTA) for 30s, prior to placement of composite resin. Teeth were collected and pulp responses were evaluated according to ISO guidelines, using pathohistomorphometric analysis and ANOVA statistics. RESULTS: Etching was found to be correlated to bacterial microleakage (p=0.0001) and tertiary dentine formation (p=0.0023). Bacterial microleakage was correlated to inflammatory activity (p=0.0001). The frequency of bacterial microleakage was: no etching (65%), EDTA (51%) and phosphoric acid (PA) (20%). SIGNIFICANCE: Vital dentine etching treatment is of extreme importance for the placement of RC to minimise bacterial microleakage. PA etching proved to be more effective at preventing bacterial microleakage than non-etching, and etching with EDTA. 相似文献
40.
BACKGROUND: The responses of mice to the mite allergen Der p 1 have been used to study the mechanisms of allergic sensitization and the development of new types of immunotherapy. Many of the studies require a knowledge of the T cell epitopes, and because Der p 1 is polymorphic, the effect of natural amino acid substitution in the allergen. The intranasal administration of peptides containing T cell epitopes can induce a mucosal tolerance but it is not known if the major activity is limited to stimulatory peptides and if, as found for autoimmunity, some epitopes are not inhibitory. OBJECTIVE: To determine and compare the sequences of Der p 1 which contain stimulatory epitopes for the high responding H-2(b) and H-2(q) mice and the sequences which induce tolerance by intranasal administration of peptides. METHODS: T cell responses of mice immunized with Der p 1 were measured by in vitro T cell stimulation assays so an extensive study of epitope recognition and intranasal tolerance could be made. Synthetic peptides were used to examine the stimulatory and inhibitory ability of all Der p 1 sequences and to map the major H-2(b) epitope in detail. This included the effect of the common polymorphic amino acid 124 substitution found within this epitope. RESULTS: Three and two regions, respectively, were found to contain stimulatory T cell epitopes for H-2(b) and H-2(q) mice. The peptides in these regions were also the most active at inducing intranasal tolerance for the responding haplotype. The correspondence between inhibitory and stimulatory peptides was maintained for the fine mapping of the major H-2(b) epitope. This was found about a core region of 118-126 which was overlapping but separate to a consensus sequence for the binding of endogeneous peptides. Peptides with alanine at the naturally polymorphic residue 124 stimulated and inhibited responses to Der p 1 more effectively, while peptides with the valine 124 variant were immunogenic but poorly cross-reactive. CONCLUSIONS: The intranasal administration of peptides representing each of five epitopes recognized by two strains of mice were able to induce mucosal tolerance and the major tolerizing activity was limited to these epitopes. The position of the core major epitope for C57 mice, which differs from a previously predicted epitope, and its specificity for the natural alanine 124 variant is described. 相似文献