全文获取类型
收费全文 | 726篇 |
免费 | 41篇 |
国内免费 | 21篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 28篇 |
妇产科学 | 16篇 |
基础医学 | 78篇 |
口腔科学 | 12篇 |
临床医学 | 76篇 |
内科学 | 178篇 |
皮肤病学 | 3篇 |
神经病学 | 96篇 |
特种医学 | 158篇 |
外科学 | 37篇 |
综合类 | 11篇 |
预防医学 | 26篇 |
眼科学 | 6篇 |
药学 | 31篇 |
肿瘤学 | 30篇 |
出版年
2022年 | 4篇 |
2021年 | 11篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 22篇 |
2011年 | 28篇 |
2010年 | 19篇 |
2009年 | 28篇 |
2008年 | 23篇 |
2007年 | 27篇 |
2006年 | 31篇 |
2005年 | 21篇 |
2004年 | 21篇 |
2003年 | 13篇 |
2002年 | 20篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 42篇 |
1997年 | 23篇 |
1996年 | 27篇 |
1995年 | 18篇 |
1994年 | 24篇 |
1993年 | 15篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 14篇 |
1989年 | 31篇 |
1988年 | 35篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有788条查询结果,搜索用时 31 毫秒
61.
62.
Matthew D. Johnson Svjetlana Miocinovic Cameron C. McIntyre Jerrold L. Vitek 《Neurotherapeutics》2008,5(2):294-308
Chronic electrical stimulation of the brain, known as deep brain stimulation (DBS), has become a preferred surgical treatment
for medication-refractory movement disorders. Despite its remarkable clinical success, the therapeutic mechanisms of DBS are
still not completely understood, limiting opportunities to improve treatment efficacy and simplify selection of stimulation
parameters. This review addresses three questions essential to understanding the mechanisms of DBS. 1) How does DBS affect
neuronal tissue in the vicinity of the active electrode or electrodes? 2) How do these changes translate into therapeutic
benefit on motor symptoms? 3) How do these effects depend on the particular site of stimulation? Early hypotheses proposed
that stimulation inhibited neuronal activity at the site of stimulation, mimicking the outcome of ablative surgeries. Recent
studies have challenged that view, suggesting that although somatic activity near the DBS electrode may exhibit substantial
inhibition or complex modulation patterns, the output from the stimulated nucleus follows the DBS pulse train by direct axonal
excitation. The intrinsic activity is thus replaced by high-frequency activity that is time-locked to the stimulus and more
regular in pattern. These changes in firing pattern are thought to prevent transmission of pathologic bursting and oscillatory
activity, resulting in the reduction of disease symptoms through compensatory processing of sensorimotor information. Although
promising, this theory does not entirely explain why DBS improves motor symptoms at different latencies. Understanding these
processes on a physiological level will be critically important if we are to reach the full potential of this powerful tool. 相似文献
63.
M P Vitek 《Neurobiology of aging》1989,10(5):471-3; discussion 477-8
64.
The NADPH-dependent reduction of chromium (VI), a known carcinogen, by
hepatic microsomes was very similar for all five humans examined, with an
apparent Km for chromate of 1.04-1.68 microM, and a Vmax of 10.4- 10.7
nmol/min/mg protein. Inhibitor studies indicate no role for cytochrome
P450s, but a prominent role for flavoproteins, which could include P450
reductase, flavin-containing mono-oxygenase and cytochrome b5. Relative to
anaerobic conditions, Cr(VI) reduction was inhibited only 26-37% by room
air, which indicates that human microsomal Cr(VI) reduction could still
proceed at significant rates, even in tissues with high O2 tensions.
Studies with lung microsomes from one human exhibited Vmax and Km values
that were two-thirds lower and 2.8-fold greater, respectively, than those
of hepatic microsomes from the same individual; other Cr(VI)-reducing
parameters were similar for lung and liver. Various forms of exogenous
iron, when present at 0.76-6.3 microM, markedly enhanced both liver and
lung microsomal rates and Vmax of Cr(VI) reduction, but did not
significantly alter the other Cr(VI)- reducing parameters (Km, effects of
O2 and inhibitors). These iron levels were 3.1- to 26-fold lower than the
initial Cr(VI) concentration, which suggests that iron is serving a
catalytic role. The ratio of human microsomal Cr(VI) reduction rates under
aerobic versus anaerobic conditions remained fairly constant, regardless of
iron concentration. Small increases in intracellular iron could therefore
lead to large increases in the rate and extent of microsomal Cr(VI)
reduction. Individuals that are simultaneously exposed to Cr(VI) and to
agents that increase intracellular iron could therefore be at potentially
greater risk for Cr(VI) toxicity and carcinogenicity.
相似文献
65.
Carotid artery stenting: Rationale, indications, and results 总被引:4,自引:0,他引:4
Gishel New MD Gary S. Roubin MD PHD Sriram S. Iyer MD Jiri J. Vitek MD PhD 《Comprehensive therapy》1999,25(8-10):438-445
Carotid stenting is a percutaneous, minimally invasive treatment for carotid stenosis. It does not carry the surgical risks of carotid endarterectomy and therefore can be applied to the elderly and to patients with comorbidities. Complications and late events appear low. 相似文献
66.
67.
1) By the action of thiouracil the follicular cell is not brought into the state of physiological inactivity and it shows signs of apparent secretion which differ however in details remarkably from the effective secretion stage. 2.) The quantity of follicular cells in mitosis is temporarily increased to the multiple. This disturbance is the result of the inhibition of caryokinesis in the stage of metaphase. 3) The absolute quantities of ribonucleic and of desoxyribonu-cleic acid are considerably reduced. 4) The ratio KNA/DNA shows a decrease to a fractional part of the normal value, according to the increase of the cell mass. 相似文献
68.
Moore AD; Godwin JD; Muller NL; Naidich DP; Hammar SP; Buschman DL; Takasugi JE; de Carvalho CR 《Radiology》1989,172(1):249-254
The authors retrospectively evaluated radiographs, computed tomographic (CT) scans, and results of pulmonary function tests (when available) for 17 patients with biopsy-proved pulmonary histiocytosis X. In 11 patients, high-resolution CT was used. In 12 patients, CT demonstrated cystic air spaces, usually less than 10 mm in diameter. In three of these 12, cysts were the only abnormality, but in six others, nodules (usually less than 5 mm in diameter) were also present. Two patients had only nodules and one, only emphysema. CT showed that many lesions that appeared reticular on plain radiographs were actually cysts. CT showed no central or peripheral concentration of lesions, but it did reveal that many small nodules were distributed in the centers of secondary lobules around small airways. CT findings correlated better with the diffusing capacity (rho = -0.71) than did the plain radiographic findings (rho = -0.57). Thus, CT was better than radiography at showing the morphology and distribution of lung abnormalities. 相似文献
69.
Digital imaging of the chest 总被引:4,自引:0,他引:4
Fraser RG; Sanders C; Barnes GT; MacMahon H; Giger ML; Doi K; Templeton AW; Cox GG; Dwyer SJ d; Merritt CR 《Radiology》1989,171(2):297-307
During the past several years, image acquisition in nuclear medicine, computed tomography, ultrasonography, subtraction angiography, and magnetic resonance has been by digitization. Despite these advances, research in the development of digital imaging in conventional radiography has lagged behind. Although studies with a variety of digital techniques have been carried out on several fronts, we still do not possess a method that has captured the imagination of the majority of radiologists and other physicians to a point where it could replace conventional screen-film imaging. This article reviews the current status and general principles of the technology, focusing on the four digital radiographic techniques that have shown the greatest promise - film digitization, an image intensifier - based system, photostimulable phosphor plates, and a scanned projection system. The physical aspects of each of the four systems and the clinical results that have been reported to date, as well as the advantages and disadvantages of each system, are presented. 相似文献
70.
TEELUCKSINGH S; STEER CR; THOMPSON CJ; SECKL JR; DOUGLAS NJ; EDWARDS CRW 《QJM : monthly journal of the Association of Physicians》1991,78(2):185-190
We describe a young man who developed extensive hypothalamicdysfunction including diabetes insipidus, adipsia, hyperprolactinaemia,and poikiliothermia together with central sleep apnoea followingexposure to toluene. 相似文献