全文获取类型
收费全文 | 1298篇 |
免费 | 133篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 74篇 |
妇产科学 | 24篇 |
基础医学 | 129篇 |
口腔科学 | 27篇 |
临床医学 | 234篇 |
内科学 | 260篇 |
皮肤病学 | 47篇 |
神经病学 | 38篇 |
特种医学 | 115篇 |
外科学 | 251篇 |
综合类 | 26篇 |
预防医学 | 68篇 |
眼科学 | 10篇 |
药学 | 63篇 |
中国医学 | 1篇 |
肿瘤学 | 72篇 |
出版年
2023年 | 11篇 |
2021年 | 14篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 19篇 |
2017年 | 19篇 |
2016年 | 34篇 |
2015年 | 22篇 |
2014年 | 38篇 |
2013年 | 44篇 |
2012年 | 24篇 |
2011年 | 37篇 |
2010年 | 32篇 |
2009年 | 59篇 |
2008年 | 40篇 |
2007年 | 41篇 |
2006年 | 49篇 |
2005年 | 38篇 |
2004年 | 34篇 |
2003年 | 29篇 |
2002年 | 25篇 |
2001年 | 28篇 |
2000年 | 41篇 |
1999年 | 36篇 |
1998年 | 41篇 |
1997年 | 39篇 |
1996年 | 50篇 |
1995年 | 34篇 |
1994年 | 38篇 |
1993年 | 35篇 |
1992年 | 31篇 |
1991年 | 33篇 |
1990年 | 34篇 |
1989年 | 28篇 |
1988年 | 31篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 23篇 |
1984年 | 23篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 22篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有1440条查询结果,搜索用时 31 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.
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
5.
Heterogeneity of the genes encoding the major surface glycoprotein of Leishmania donovani. 总被引:3,自引:0,他引:3
The major surface glycoprotein of Leishmania (GP63) is present on all known species of Leishmania and likely plays an integral role during the infection of macrophages in the mammalian host. To identify regions of GP63 which may be of functional significance, the nucleotide sequence of a gene encoding GP63 of Leishmania donovani was determined and compared to the sequences reported for GP63 genes of Leishmania major and Leishmania chagasi. The GP63 nucleotide and predicted protein sequence was highly conserved among the 3 species despite their diverse geographical distribution. L. donovani GP63 is encoded by a multigene family and the gene locus contains at least 7 tandemly repeated genes and at least 3 genes which are dispersed from the tandem array. In addition, polymerase chain reaction and Southern blot analyses demonstrated that there was size heterogeneity within the pro-peptide coding regions of the multiple GP63 genes of L. donovani and that such genes were expressed concurrently in the promastigote life stage. 相似文献
6.
A P Boon M P Carey D H Adams J Buckels P McMaster 《Journal of clinical pathology》1991,44(11):909-914
Five cases of central pontine myelinolysis (CPM) were detected by neuropathological examination in a series of 50 patients coming to necropsy after liver transplantation. One patient also had extrapontine myelinolysis. In no case was the diagnosis made during life. Only two patients showed rapid rises in serum sodium concentrations. The incidence of hyponatraemia, before and after transplantation, and rapid rises in serum sodium in patients with CPM was significantly greater than in the 45 patients showing no neuropathological evidence of CPM. It is concluded that there is a high incidence of CPM after liver transplantation, that clinical diagnosis is difficult, and that there is no simple direct correlation between rapid serum sodium changes and the development of this condition. Avoidance of major electrolyte fluctuations at the time of liver transplantation is recommended but it must be emphasised that CPM may occur without any rapid rise in serum sodium concentration. 相似文献
7.
The interaction between exercise and drug response has not been studied extensively. The present study examined the relationship between both acute (15 minute) and chronic (10 week) treadmill exercise and behavioral response to the carbamates physostigmine and pyridostigmine. Rats trained on an operant task under a multi-component FR30 schedule were used to evaluate the interaction between exercise and performance following drug administration. The direct effects of both 10 weeks of exercise conditioning and a moderate exercise challenge, as well as the interaction between two were assessed. Results obtained with physostigmine show that acute exercise increased behavioral sensitivity. Chronic exercise resulted in behavioral tolerance. These results are consistent with previously reported studies of centrally acting compounds. In contrast, pyridostigmine, which has little or no central activity, produced no behavioral changes. This result was constant over exercise conditions. 相似文献
8.
9.
10.
Immunotopographic assessment of lymphoid and plasma cell malignancies in the bone marrow 总被引:4,自引:0,他引:4
Rene Kronland MD Thomas Grogan MD Catherine Spier MD Daniel Wirt HTL Catherine Rangel MT Lynne Richter MD Brian Durie MD Bernard Greenberg MD Thomas Miller MD Stephen Jones 《Human pathology》1985,16(12):1247-1254
To determine the utility of tissue section immunochemistry in the evaluation of bone marrow involved by lymphoid and plasma cell malignancies, snap-frozen, undecalcified bone marrow core and aspirate samples from 23 patients with these disorders were studied with a battery of monoclonal antibodies. With techniques that preserve architecture, difficult diagnostic cases characterized by core but not aspirate involvement, or the reverse, were resolved. By means of an extensive battery of monoclonal antibodies applied to serial sections, complex tumor cell phenotypes were established in all 23 cases. In addition to the identification of straightforward monoclonal surface immunoglobulin expression in small cleaved cell lymphomas (four cases), the battery approach added immunologic certainty in malignancies with unusual or difficult phenotypes: peripheral T-cell lymphomas with idiosyncratic antigen expression, and chronic lymphocytic leukemias and small cell lymphomas with faint surface immunoglobulin expression (four cases). For the chronic lymphocytic leukemias and the small cell lymphomas, the combined IgD+, B2+, B1+, Ia+, Leu-1+ phenotype taken as a whole had greater utility than any isolated marker. The acute lymphocytic leukemias and the myelomas studied demonstrate the wide range of B-cell antigens that must be detected to account for the variety of B-cell neoplasms encountered. Additionally, the previously undescribed phenotypic subset of CALLA+ myelomas, which is of prognostic relevance, was identified. Marrow frozen section immunotyping is a major asset in the evaluation of patients with lymphoma, leukemia, and myeloma when special care is accorded to tissue handling and to treatment of endogenous peroxidase/pseudoperoxidase and interstitial immunoglobulin. 相似文献