全文获取类型
收费全文 | 920篇 |
免费 | 58篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 24篇 |
妇产科学 | 58篇 |
基础医学 | 121篇 |
口腔科学 | 36篇 |
临床医学 | 122篇 |
内科学 | 147篇 |
皮肤病学 | 17篇 |
神经病学 | 123篇 |
特种医学 | 32篇 |
外科学 | 87篇 |
综合类 | 5篇 |
一般理论 | 5篇 |
预防医学 | 55篇 |
眼科学 | 4篇 |
药学 | 57篇 |
中国医学 | 2篇 |
肿瘤学 | 77篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 43篇 |
2012年 | 52篇 |
2011年 | 58篇 |
2010年 | 34篇 |
2009年 | 32篇 |
2008年 | 61篇 |
2007年 | 76篇 |
2006年 | 65篇 |
2005年 | 66篇 |
2004年 | 53篇 |
2003年 | 52篇 |
2002年 | 50篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 11篇 |
1997年 | 15篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1949年 | 4篇 |
排序方式: 共有978条查询结果,搜索用时 15 毫秒
91.
Moritz A Koci G Steinlechner B Hölzenbein T Nasel C Grubhofer G Dworschak M 《Wiener klinische Wochenschrift》2007,119(21-22):669-673
Approximately 10-20% of patients will not tolerate cross-clamping of the common carotid artery for carotid endarterectomy procedures. The most frequent causes of neurological deficits are either embolization of particulate matter or cerebral hypoperfusion. Insufficient blood flow through primary collaterals of the circle of Willis is the main reason for hypoperfusion that requires immediate shunt placement. Although excessive preoperative imaging is not indicated in many patients undergoing disobliteration of a stenosed internal carotid artery, there are some patients with particular anatomic constellations who would benefit from a more detailed preoperative work-up. In these cases, the specific risk should be evaluated prior to surgery in order to make plans for appropriate intraoperative management regarding neurologic monitoring and shunt insertion. As regional anesthesia permits early detection of ischemic symptoms, it is advantageous in these patients. We report a case where regional anesthesia allowed early detection of rapidly progressing signs of bi-hemispheric brain ischemia in a patient with diabetes and with at that time unknown severe abnormalities of the circle of Willis. Lack of adequate collateralization was detected only after surgery, in a combined perfusion-magnetic resonance imaging study. In symptomatic diabetics with low-grade stenosis of the internal carotid artery, preoperative assessment of the function of the circle of Willis may therefore be helpful in predicting any increased risk for intraoperative cerebral ischemia. 相似文献
92.
93.
94.
Winston X. Yan Karen J. Mullinger Gerda B. Geirsdottir Richard Bowtell 《Human brain mapping》2010,31(4):604-620
The collection of electroencephalography (EEG) data during simultaneous functional magnetic resonance imaging (fMRI) is impeded by large artefacts in the EEG recordings, with the pulse artefact (PA) being particularly challenging because of its persistence even after application of artefact correction algorithms. Despite several possible causes of the PA having been hypothesized, few studies have rigorously quantified the contributions from the different putative sources. This article presents analytic expressions and simulations describing two possible sources of the PA corresponding to different movements in the strong static field of the MR scanner: cardiac‐pulse‐driven head rotation and blood‐flow‐induced Hall voltages. Models of head rotation about a left–right axis and flow in a deep artery running in the anterior–posterior direction reproduced properties of the PA including the left/right spatial variation of polarity. Of these two sources, head rotation was shown to be the most likely source of the PA with simulated magnitudes of >200 μV being generated at 3 T, similar to the in vivo PA magnitudes, for an angular velocity of just 0.5°/s. Smaller artefact voltages of less than 10 μV were calculated for flow in a model artery with physical characteristics similar to the internal carotid artery. A deeper physical understanding of the PA is a key step in working toward production of higher fidelity EEG/fMRI data: analytic expressions for the artefact voltages can guide a redesign of the wiring layout on EEG caps to minimize intrinsic artefact pickup, while simulated artefact maps could be incorporated into selective filters. Hum Brain Mapp, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
95.
96.
Karlsson D Fallarero A Brunhofer G Mayer C Prakash O Mohan CG Vuorela P Erker T 《European journal of pharmaceutical sciences》2012,47(1):190-205
The role of butyrylcholinesterase (BChE) in the progression of Alzheimer's disease (AD) has recently become more crucial. In the AD brain, selective BChE inhibitors have been demonstrated to have a beneficial effect in vivo, probably by recovering cholinergic activity and/or by restoring AChE:BChE activity ratios to the levels observed in the healthy brain. Thienothiazines are compounds sharing some structural features with phenothiazines, which are known to be potent BChE inhibitors. Thus, in this contribution 45 thienothiazines were investigated for their BChE inhibitory activity. Six of them were proven to be potent and selective inhibitors of equine BChE's hydrolase activity. Structure-activity relationships were laid out, and a tentative pharmacophore model for BChE inhibitors of the thienothiazine type was proposed. The most active compound, 3f, displayed a mixed type of inhibition and was also active against the human BChE (huBChE) with an IC(50) huBChE of 0.51 ± 0.07 μM. Computational studies suggested that 3f likely binds to the catalytic site and nearby to the peripheral site of the huBChE in an extended form. In addition, the chemical space occupied by the active thienothiazines, as opposed to phenothiazines and other representative chemical classes of BChE inhibitors, was explored with the aid of ChemGPS-NP, and the relevant chemical space regions were identified. This study shows for the first time that thienothiazines represent a new group of BChE inhibitors that can be used as molecular probes for studying the role of BChE in the brain or for developing newer drug leads for AD therapy. 相似文献
97.
98.
Feichtinger M Eder H Holl A Körner E Zmugg G Aigner R Fazekas F Ott E 《Epilepsia》2007,48(7):1409-1413
PURPOSE: In the presurgical evaluation of patients with partial epilepsy, the ictal single photon emission computed tomography (SPECT) is a useful noninvasive diagnostic tool for seizure focus localization. To achieve optimal SPECT scan quality, ictal tracer injection should be carried out as quickly as possible after the seizure onset and under highest safety conditions possible. Compared to the commonly used manual injection, an automatic administration of the radioactive tracer may provide higher quality standards for this procedure. In this study, therefore, we retrospectively analyzed efficiency and safety of an automatic injection system for ictal SPECT tracer application. METHODS: Over a 31-month period, 26 patients underwent ictal SPECT by use of an automatic remote-controlled injection pump originally designed for CT-contrast agent application. Various factors were reviewed, including latency of ictal injection, radiation safety parameters, and ictal seizure onset localizing value. RESULTS: Times between seizure onset and tracer injection ranged between 3 and 48 s. In 21 of 26 patients ictal SPECT supported the localization of the epileptogenic focus in the course of the presurgical evaluation. In all cases ictal SPECT tracer injection was performed with a high degree of safety to patients and staff. CONCLUSIONS: Ictal SPECT by use of a remote-controlled CT-contrast agent injection system provides a high scan quality and is a safe and confirmatory presurgical evaluation technique in the epilepsy-monitoring unit. 相似文献
99.
Storkholm JH Zhao J Villadsen GE Hager H Jensen SL Gregersen H 《Digestive diseases and sciences》2007,52(2):336-346
Small intestinal obstruction is a frequently encountered clinical problem. To understand the mechanisms behind obstruction
and the clinical consequences, data are needed on the relation between the morphologic and biomechanical remodeling that takes
place in the intestinal wall during chronic obstruction. We sought to determine the effect of partial obstruction on mechanical
and morphologic properties of the guinea pig small intestine. Partial obstruction was created surgically in 2 groups of animals
living for 2 and 4 weeks. Controls were sham operated and lived for 4 weeks. A combined impedance planimetry–high-frequency
ultrasound system was designed to measure the luminal cross-sectional area and wall thickness. These measures were used to
compute the circumferential stress and strain of the excised intestinal segments. The incremental elastic modulus was obtained
by using nonlinear fitting of the stress–strain curve. Histologic analysis and the measurements of total wall collagen were
also performed. The luminal cross-sectional area, wall thickness, and elastic modulus in circumferential direction increased
in a time-dependent manner proximal to the obstruction site (P < 0.01), whereas no differences in these parameters were found distal to the obstruction site (P > 0.25). The circumferential stress–strain curves of the proximal segments in 2- and 4-week groups shifted to the left, indicating
the intestinal wall became stiffer. Histologic examination revealed a massive increase in the thickness of the muscle layer
especially the circular smooth muscle layer (P < 0.05). The collagen content proximal to the obstruction site was significantly larger in the partially obstructed animals
compared to controls (P < 0.05). No difference was found distal to the obstruction site. Strong correlation was found between the collagen content
and the elastic modulus at stress levels of 70 kPa stress (P < 0.01) and 10 kPa (P < 0.05) proximal to the obstruction site suggesting that the alteration of collagen has great impact on the mechanical remodeling.
The morphologic and biomechanical remodeling likely influence the function of the intestine affected by partial obstructed
intestine. 相似文献
100.
The extracellular calcium-sensing receptor (CaR) senses small fluctuations of the extracellular calcium (Ca(2+)(e)) concentration and translates them into potent changes in parathyroid hormone secretion. Dissecting the regulatory mechanisms of CaR-mediated signal transduction may provide insights into the physiology of the receptor and identify new molecules as potential drug targets for the treatment of osteoporosis and/or hyperparathyroidism. CaR can be phosphorylated by protein kinase C (PKC) and G protein-coupled receptor kinases (GRKs), and has been shown to bind to beta-arrestins, potentially contributing to desensitization of CaR, although the mechanisms by which CaR-mediated signal transduction is terminated are not known. We used a PKC phosphorylation site-deficient CaR, GRK and beta-arrestin overexpression or down-regulation to delineate CaR-mediated desensitization. Fluorescence-activated cell sorting was used to determine whether receptor internalization contributed to desensitization. Overexpression of GRK 2 or 3 reduced Ca(2+)(e)-dependent inositol phosphate accumulation by more than 70%, whereas a GRK 2 mutant deficient in G alpha(q) binding (D110A) was without major effect. Overexpression of GRK 4-6 did not reduce Ca(2+)(e)-dependent inositol phosphate accumulation. Overexpression of beta-arrestin 1 or 2 revealed a modest inhibitory effect on Ca(2+)(e)-dependent inositol phosphate production (20-30%), which was not observed for the PKC phosphorylation site-deficient CaR. Agonist-dependent receptor internalization (10-15%) did not account for the described effects. Thus, we conclude that PKC phosphorylation of CaR contributes to beta-arrestin-dependent desensitization of CaR coupling to G proteins. In contrast, GRK 2 predominantly interferes with G protein-mediated inositol-1,4,5-trisphosphate formation by binding to G alpha(q). 相似文献