全文获取类型
收费全文 | 1276篇 |
免费 | 167篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 55篇 |
妇产科学 | 16篇 |
基础医学 | 181篇 |
口腔科学 | 21篇 |
临床医学 | 205篇 |
内科学 | 298篇 |
皮肤病学 | 41篇 |
神经病学 | 36篇 |
特种医学 | 146篇 |
外科学 | 252篇 |
综合类 | 23篇 |
预防医学 | 75篇 |
眼科学 | 5篇 |
药学 | 37篇 |
肿瘤学 | 52篇 |
出版年
2023年 | 13篇 |
2021年 | 18篇 |
2020年 | 10篇 |
2019年 | 20篇 |
2018年 | 27篇 |
2017年 | 22篇 |
2016年 | 35篇 |
2015年 | 30篇 |
2014年 | 43篇 |
2013年 | 49篇 |
2012年 | 37篇 |
2011年 | 48篇 |
2010年 | 59篇 |
2009年 | 63篇 |
2008年 | 44篇 |
2007年 | 31篇 |
2006年 | 46篇 |
2005年 | 36篇 |
2004年 | 38篇 |
2003年 | 33篇 |
2002年 | 23篇 |
2001年 | 16篇 |
2000年 | 31篇 |
1999年 | 38篇 |
1998年 | 41篇 |
1997年 | 45篇 |
1996年 | 44篇 |
1995年 | 42篇 |
1994年 | 33篇 |
1993年 | 35篇 |
1992年 | 23篇 |
1991年 | 22篇 |
1990年 | 18篇 |
1989年 | 33篇 |
1988年 | 31篇 |
1987年 | 39篇 |
1986年 | 29篇 |
1985年 | 21篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1973年 | 11篇 |
1969年 | 8篇 |
1965年 | 5篇 |
排序方式: 共有1452条查询结果,搜索用时 46 毫秒
1.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
2.
Shigeru Ichioka MD ; Naomi Sekiya MT ; Masahiro Shibata PhD ; Takashi Nakatsuka MD 《Wound repair and regeneration》2007,15(4):572-576
The leukocyte-endothelium interaction is known to contribute to reperfusion injury, which is considered to participate in the pathophysiology of pressure ulcers, and integrin alphaV beta3 (alphavbeta3) has been shown to mediate the processes of cellular adhesion in various types of cells. This study aims to clarify leukocyte behavior in our original microcirculatory pressure-induced reperfusion model, which can visualize the microcirculation in vivo. We also estimated the effect of alphavbeta3 integrin inhibition on the reduction of the leukocyte-endothelium interaction. Mice with dorsal skinfold chambers were divided into three groups: the baseline group (n=6), in which animals received no compression; the compression-reperfusion group (n=6), in which animals underwent 2-hour compression of the dorsal skin, followed by release, and the inhibitor-treated group (n=7), in which an alphavbeta3 inhibitor, CP4715, was administered in addition to the compression-release procedure. Staining with rhodamine 6G quantitatively visualized leukocyte behavior under the intravital fluorescent microscope. Compression-reperfusion induced a significant increase in rolling, sticking, and extravasation of the leukocytes. Treatment with the inhibitor strikingly reduced leukocyte sticking and extravasation. The present experiment has provided evidence that alphavbeta3 inhibition reduces leukocyte-endothelium interaction in our original pressure-induced reperfusion model. 相似文献
3.
Dr. S. Eggstein MD G. Manthey MT T. Hirsch PhD F. Baas MA B. U. V. Specht MD E. H. Farthmann MD 《Digestive diseases and sciences》1996,41(6):1069-1075
Epidermal growth factor receptors (EGFR) andras mutations are known to play a significant role in controlling cell growth and tumor promotion. Both of them transmit mitogenic signals to the nucleus by activation of Raf-1 kinase. In this study, the expression of EGFR and mutant Ras proteins, and, for the first time, the expression, phosphorylation and kinase activity of Raf-1 kinase have been determined in paired samples of colorectal cancer and mucosa. The tumor and mucosa samples did not differ significantly with regard to Raf-1 kinase content and activity. A major difference between tumors and mucosa was found, however, in the phosphorylation of Raf-1. Most of the mucosa samples (13/20), but only 1/20 of the cancer samples, contained hyperphosphorylated Raf-1. EGFR were significantly (p=0.0025) decreased in the tumors. The decreased phosphorylation of Raf-1 in colonic carcinomas could be the result of activation of Raf-1 phosphatases or inactivation of kinases phosphorylating Raf-1. New forms of treatment based on EGFR overexpression do not seem to be suitable for the majority of colonic cancers.This work was supported by the state of Baden-Württemberg (Verbundforschungsprojekt: Aufklärung von Mechanismen der Tumorentstehung und Tumorabwehr). 相似文献
4.
A S Lamont M S Roberts D G Holdsworth A Atherton J J Shepherd 《Anaesthesia and intensive care》1986,14(4):360-364
Recently, a family tree with a predisposition for the gene of multiple endocrine neoplasia Type 1 has been identified in Tasmania. As the surgical identification and localisation of parathyroid adenomas is facilitated by the administration of methylene blue, an opportunity has presented to measure the plasma concentration of methylene blue and methaemoglobin production. The study was undertaken to establish whether significant methaemoglobin concentrations were generated during the infusion and whether these concentrations could be related to the corresponding methylene blue concentrations. Mean peak methylene blue concentrations of 3.72 micrograms l-1, mean percentage methaemoglobin of 10.0 and a PaO2 within acceptable clinical ranges were found. No apparent relationship between methylene blue concentration and methaemoglobin production was found. 相似文献
5.
Analysis of ischemia-reperfusion injury in a microcirculatory model of pressure ulcers 总被引:2,自引:0,他引:2
Shinsaku Tsuji MD ; Shigeru Ichioka MD ; Naomi Sekiya MT ; Takashi Nakatsuka MD 《Wound repair and regeneration》2005,13(2):209-215
The aim of this study was to establish a pressure ulcer model that visualizes the microcirculation, and to examine the participation of ischemia-reperfusion injury in the pathophysiology of pressure ulcers. An original system composed of a new skin fold chamber and compression device allowed loading quantitative vertical stress to the skin. An intravital microscopic technique enabled direct visualization of the microcirculation in the physiological condition and in response to pressure application. To estimate the effect of ischemia-reperfusion injury, animals were divided into two groups: the compression-release group (n = 8), in which the animals received four cycles of compression-release which consisted of 2 hours of compression followed by 1 hour of pressure release; and the compression alone group (n = 8) in which the animals underwent continuous compression for 8 hours. Functional capillary density was quantified before the compression procedure and on day 1 (35 hours) after the first evaluation. The cyclic compression-release procedure significantly decreased functional capillary density as compared to continuous compression, indicating that in our experimental setting repetition of ischemia-reperfusion cycle more severely damaged the microcirculation than single prolonged ischemic insult. This finding supports the significant contribution of ischemia-reperfusion injury to the pathophysiology of pressure ulcers at the level of dynamic in vivo microcirculation. 相似文献
6.
J. Holdsworth 《Annals of the Royal College of Surgeons of England》1997,79(2):96-101
An audit of 10 years of arterial surgery was undertaken to compare the first 5 years with the second 5 years. The aim was to see if the surgery during the second 5 years was being undertaken to an acceptable standard, and if there had been improvements in haemorrhagic complications and outcome for femoro-crural bypass grafts, which had previously been identified as problem areas during the first 5 years. Between the two 5-year periods, combined general surgical and arterial admissions and operations reduced by 21.8% and 26.2%, respectively, owing to marked reductions in gastrointestinal and biliary patients. At the same time, arterial admissions and operations increased by 55.7% and 46.6%, respectively. Improvements were found in outcome for aortic and iliac aneurysms and lower limb bypasses, in particular crural grafts. Aorto-iliac and aortofemoral bypasses were undertaken less frequently with a higher mortality and more complications, but in the second 5 years these patients were more urgent and more likely to have a threatened limb. There was a reduction in re-operation for postoperative bleeding in the second 5 years (4.6% vs 2.2%). It was concluded that the surgery was being undertaken to an acceptable standard, but that the quantity of vascular surgery during the second 5 years was such that continued single-surgeon practice in the present setting was unacceptable. 相似文献
7.
8.
C Aranyi W J O'Shea C A Halder C E Holdsworth B Y Cockrell 《Toxicology and industrial health》1986,2(1):85-98
Ninety-day inhalation studies were conducted on 50:50 weight percent (wt %) mixtures of n-butane:n-pentane and isobutane:isopentane, respectively, and on a distillation cut boiling below 145 degrees F of a reference unleaded gasoline blend to assess the nephrotoxicity of these volatile mixtures. The mixtures of butanes and pentanes were selected because these four hydrocarbons are the most prevalent components of gasoline vapors encountered under typical occupational exposures. The 0-145 degrees F gasoline distillation fraction was tested because it reasonably approximates the composition of gasoline vapors measured under occupational settings. Male and female F-344 rats were exposed to 2 levels of each mixture, 6 hours per day, 5 days per week, for 13 weeks. The target concentrations for the butane:pentane mixtures were 4500 and 1000 parts per million (ppm), while 5200 and 1200 ppm were set for the gasoline distillation fraction. An interim sacrifice was conducted after 28 days. The rats were not significantly affected by the exposures, and there was no evidence of hydrocarbon-induced nephropathy in either sex at the termination of each study. However, at the 28-day interim sacrifice period for both butane:pentane mixtures, mild, transient treatment-related but not exposure-related kidney effects were observed in the male rats. These perturbations were absent at the interim sacrifice period for the gasoline distillation fraction. 相似文献
9.
10.
Management of a patient with a congenital anomaly of the midgut can be difficult for a surgeon since these abnormalities are extremely rare particularly in adults. However a thorough knowledge of embryology and anatomy will allow the complexity of a rotational anomaly to be resolved. A case of reversed rotation of the midgut is presented and the literature on this subject reviewed. 相似文献