首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3802篇
  免费   136篇
  国内免费   27篇
耳鼻咽喉   176篇
儿科学   79篇
妇产科学   102篇
基础医学   554篇
口腔科学   28篇
临床医学   342篇
内科学   1054篇
皮肤病学   12篇
神经病学   243篇
特种医学   115篇
外科学   437篇
综合类   29篇
一般理论   3篇
预防医学   181篇
眼科学   70篇
药学   291篇
中国医学   2篇
肿瘤学   247篇
  2024年   2篇
  2023年   18篇
  2022年   152篇
  2021年   240篇
  2020年   65篇
  2019年   104篇
  2018年   134篇
  2017年   82篇
  2016年   98篇
  2015年   112篇
  2014年   163篇
  2013年   216篇
  2012年   313篇
  2011年   349篇
  2010年   166篇
  2009年   108篇
  2008年   231篇
  2007年   235篇
  2006年   264篇
  2005年   221篇
  2004年   221篇
  2003年   186篇
  2002年   134篇
  2001年   15篇
  2000年   7篇
  1999年   13篇
  1998年   14篇
  1997年   9篇
  1996年   10篇
  1995年   9篇
  1994年   5篇
  1993年   6篇
  1992年   7篇
  1991年   5篇
  1990年   11篇
  1989年   7篇
  1988年   5篇
  1987年   3篇
  1985年   2篇
  1984年   2篇
  1981年   3篇
  1980年   2篇
  1978年   3篇
  1977年   2篇
  1976年   1篇
  1975年   3篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有3965条查询结果,搜索用时 31 毫秒
91.
BACKGROUND: Cardioversion of atrial fibrillation (AF) carries the risk of thromboembolic complications and, therefore, anticoagulation therapy is routinely administered before and after this procedure. In patients with permanent AF who undergo implantation of cardioverter-defibrillator (ICD), anticoagulants are usually withdrawn during the perioperative period. However, in some patients sinus rhythm may be restored during defibrillation threshold (DFT) testing which potentially may increase the risk of thromboembolic complications. AIM: To assess the frequency of sinus rhythm restoration during ICD implantation in patients with permanent AF and the rate of both thromboembolic events and local bleeding complications which may occur due to temporary withdrawal of anticoagulation therapy and its re-initiation early after the procedure. METHODS: Permanent AF was present in 23 (12%) of 193 patients selected for ICD implantation. All patients received prolonged oral anticoagulation according to the generally accepted standards. Anticoagulation therapy was stopped few days before the procedure and replaced by low molecular weight heparin which was administered up to 24 hours before ICD implantation and re-initiated 12-24 hours afterwards. RESULTS: During DFT testing sinus rhythm was restored in 5 (21.7%) patients with AF. Clinical and DFT characteristics were similar in those who were converted to sinus rhythm and those who remained in AF. No thromboembolic events were noted in either group. Local haematoma at the site of ICD implantation occurred in two (8%) patients. CONCLUSIONS: Sinus rhythm was restored in 21.7% of patients with permanent AF who underwent ICD implantation. Temporary withdrawal of anticoagulation therapy did not increase the risk of thromboembolic complications, however, its early re-initiation after implantation resulted in an increase in local bleeding complication rate.  相似文献   
92.
93.
Two-photon microscopy allows visualization of subcellular structures in the living animal retina. In previously reported experiments it was necessary to apply a contact lens to each subject. Extending this technology to larger animals would require fitting a custom contact lens to each animal and cumbersome placement of the living animal head on microscope stage. Here we demonstrate a new device, periscope, for coupling light energy into mouse eye and capturing emitted fluorescence. Using this periscope we obtained images of the RPE and their subcellular organelles, retinosomes, with larger field of view than previously reported. This periscope provides an interface with a commercial microscope, does not require contact lens and its design could be modified to image retina in larger animals.OCIS codes: (170.0110) Imaging systems, (170.4460) Ophthalmic optics and devices, (170.5755) Retina scanning, (180.4315) Nonlinear microscopy, (330.7327) Visual optics, ophthalmic instrumentation  相似文献   
94.
[Purpose] To assess the effect of 12-weeks Nordic walking training on gait parameters and some elements of postural control. [Subjects and Methods] Sixty-seven women aged 65 to 74 years were enrolled in this study. The subjects were divided into a Nordic Walking group (12 weeks of Nordic walking training, 3 times a week for 75 minutes) and a control group. In both study groups, a set of functional tests were conducted at the beginning and at the end of the study: the Forward Reach Test (FRT) and the Upward Reach Test (URT) on a stabilometric platform, and the analysis of gait parameters on a treadmill. [Results] The NW group showed improvements in: the range of reach in the FRT test and the URT test in compared to the control group. The length of the gait cycle and gait cycle frequency also showed changes in the NW group compared to the control group. [Conclusion] A 12-week NW training program had a positive impact on selected gait parameters and may improve the postural control of women aged over 65 according to the results selected functional tests.Key words: Nordic walking, Postural control, Gait  相似文献   
95.
The fibroblast growth factor 1 (FGF1) gene is expressed primarily in the kidney and may contribute to hypertension. However, the biologic mechanisms underlying the association between FGF1 and BP regulation remain unknown. We report that the major allele of FGF1 single nucleotide polymorphism rs152524 was associated in a dose-dependent manner with systolic BP (P=9.65×10−5) and diastolic BP (P=7.61×10−3) in a meta-analysis of 14,364 individuals and with renal expression of FGF1 mRNA in 126 human kidneys (P=9.0×10−3). Next-generation RNA sequencing revealed that upregulated renal expression of FGF1 or of each of the three FGF1 mRNA isoforms individually was associated with higher BP. FGF1-stratified coexpression analysis in two separate collections of human kidneys identified 126 FGF1 partner mRNAs, of which 71 and 63 showed at least nominal association with systolic and diastolic BP, respectively. Of those mRNAs, seven mRNAs in five genes (MME, PTPRO, REN, SLC12A3, and WNK1) had strong prior annotation to BP or hypertension. MME, which encodes an enzyme that degrades circulating natriuretic peptides, showed the strongest differential coexpression with FGF1 between hypertensive and normotensive kidneys. Furthermore, higher level of renal FGF1 expression was associated with lower circulating levels of atrial and brain natriuretic peptides. These findings indicate that FGF1 expression in the kidney is at least under partial genetic control and that renal expression of several FGF1 partner genes involved in the natriuretic peptide catabolism pathway, renin-angiotensin cascade, and sodium handling network may explain the association between FGF1 and BP.  相似文献   
96.
Cytokinemia and oxidative stress are important factors responsible for an inadequate immune response in the early course of acute pancreatitis (AP). The aim of the study was to evaluate the profiles of interleukin 18 (IL-18), glutathione peroxidase (GPx), and selenium concentrations in serum with respect to AP severity and to study the relationships between these parameters and recognized prognostic indicators of AP severity. Prospective clinical analyses were performed on 61 patients with mild and severe forms of AP and for 15 healthy volunteers. In both forms of AP severity, the IL-18 concentration in the serum was significantly higher than in healthy controls. In the severe form of AP, the IL-18 concentration was the highest and exceeded significantly the values recorded on the 1st, 2nd, 3rd, 5th, and 10th days of mild AP. A significantly lower GPx concentration in the serum was recorded in severe AP compared to the mild form and in the control group. There was a significantly lower selenium concentration in the severe form of AP. Significant correlations between GPx and selenium, between IL-18 and GPx, and between IL-18 and selenium were recorded. The ROC analysis shows a high prognostic accuracy of IL-18 and GPx concentrations in the determination of AP severity. IL-18 is released early in the course of AP and may be a key immunomodulator of the inflammatory response in the severe form of this disease. Low GPx and selenium concentrations in severe AP reflect the lower antioxidative ability in this form of AP. IL-18 and GPx may represent new indicators of AP severity.  相似文献   
97.
98.
99.

Introduction

Statin use might be associated with an increased risk of sleep disturbances including insomnia, but the evidence regarding sleep changes following statin therapy has not been conclusive. Therefore we assessed the impact of statin therapy on sleep changes through a systematic review and meta-analysis of available randomized controlled trials (RCTs).

Material and methods

We searched MEDLINE and SCOPUS up to October 1, 2014 to identify placebo-controlled RCTs investigating the effect of statin therapy on sleep changes. A meta-analysis was performed using either a fixed-effects or a random-effect model according to the I2 statistic. Effect size was expressed as weighted mean difference (WMD) and 95% confidence interval (CI).

Results

Overall, the impact of statin therapy on polysomnography (PSG) indices of sleep was reported in 5 trials comprising 9 treatment arms. Overall, statin therapy had no significant effect on total sleep duration (WMD: –7.75 min, 95% CI: –18.98, 3.48, p = 0.176), sleep efficiency (WMD: 0.09%, 95% CI: –2.27, 2.46, p = 0.940), entries to stage I (WMD: 0.36, 95% CI: –0.91, 1.63, p = 0.580), or latency to stage I (WMD: –1.92 min, 95% CI: –4.74, 0.89, p = 0.181). In contrast, statin therapy significantly reduced wake time (WMD: –4.43 min, 95% CI: –7.77, –0.88, p = 0.014) and number of awakenings (WMD: –0.40, 95% CI: –0.46, –0.33, p < 0.001). Meta-regression did not suggest any correlation between changes in wake time and awakening episodes with duration of treatment and LDL-lowering effect of statins.

Conclusions

The results indicated that statins have no significant adverse effect on sleep duration and efficiency, entry to stage I, or latency to stage I sleep, but significantly reduce wake time and number of awakenings.  相似文献   
100.
A case of atlas assimilation revealed during serial study of suboccipital region is presented. The specimen was harvested from the body of 31-year-old woman. Images of the computed tomography scans are correlated with classic dissection. Asymmetrical bony assimilation is accompanied by asymmetrical development of the suboccipital musculature. In the presented case, the atlantic segments of both vertebral arteries preserved their usual course between bony elements derived from the atlas and proatlas. Development of the soft tissues must be influenced by similar factors as development of the skeleton. Detailed radiologic studies, possibly with volumetric reconstructions, are necessary in cases of atlas assimilation before surgical interventions in the region of craniovertebral junction.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号