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   1607篇
  免费   75篇
  国内免费   15篇
耳鼻咽喉   26篇
儿科学   44篇
妇产科学   44篇
基础医学   155篇
口腔科学   29篇
临床医学   159篇
内科学   335篇
皮肤病学   18篇
神经病学   133篇
特种医学   101篇
外科学   316篇
综合类   16篇
预防医学   66篇
眼科学   53篇
药学   148篇
中国医学   6篇
肿瘤学   48篇
  2024年   4篇
  2023年   22篇
  2022年   71篇
  2021年   106篇
  2020年   39篇
  2019年   45篇
  2018年   67篇
  2017年   50篇
  2016年   42篇
  2015年   47篇
  2014年   72篇
  2013年   99篇
  2012年   101篇
  2011年   101篇
  2010年   64篇
  2009年   59篇
  2008年   75篇
  2007年   103篇
  2006年   121篇
  2005年   79篇
  2004年   78篇
  2003年   61篇
  2002年   76篇
  2001年   11篇
  2000年   26篇
  1999年   14篇
  1998年   12篇
  1997年   2篇
  1996年   3篇
  1995年   4篇
  1994年   3篇
  1993年   1篇
  1992年   4篇
  1991年   10篇
  1990年   4篇
  1989年   2篇
  1987年   4篇
  1986年   1篇
  1985年   2篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1977年   1篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
  1965年   1篇
  1960年   1篇
排序方式: 共有1697条查询结果,搜索用时 0 毫秒
71.
Our objective was to describe MR imaging findings of liver lesions in human fascioliasis. The MR imaging of the liver was performed in 29 patients with fascioliasis. Seventeen patients were women and 12 were men, with a mean age of 47.5 years (age range 17–75 years). Hepatic lesions were grouped into five types based on their signal characteristics. Three patients had normal imaging findings. One or more lesions were observed in the other 26 patients. The lesion types and the frequency of appearances were as follows: hyperintensity of the liver capsule on T2-weighted images (n=16, 55.2%); ill-defined slightly hyperintense areas on T2-weighted images (n=18, 62.1%); lesions which were hypointense on T1-weighted and hyperintense on T2-weighted images (n=10, 34.5%); hypointense on T1-weighted images and centrally hypo- or hyperintense, surrounded by peripherally less hyperintense area on T2-weighted images (n=4, 13.8%); and hypointense foci or ill-defined hypointense areas on T1- and T2-weighted images (n=10, 34.5%). We describe the MR imaging features of the disease. Our findings may help the differential diagnosis in which fascioliasis should be added to the list. Electronic Publication  相似文献   
72.
We investigated role of reactive oxygen species (ROS) and apoptosis in the pathogenesis of infertility in experimental model of varicocele. The protective effect of vitamin E was also examined. Three groups of rats were constructed as the first group had sham operation, experimental varicoceles were established by partial ligation of the left renal vein in later two groups. Third group had received vitamin E. Production of ROS was determined by chemiluminescence assay (CL). The in situ end labelling technique was utilized to investigate apoptosis. Tissue vitamin E levels were measured by high performance liquid chromatography. The differences between luminol enhanced CL levels of groups were not statistically significant. However, the difference between CL levels of lucigenin probe in left testicles of sham and varicocele groups were statistically significant ( p = 0.0007). Similarly, the results of the third group receiving vitamin E significantly differed from the varicocele group ( p = 0.0025). The difference of apoptotic index was also statistically significant between sham and varicocele groups ( p = 0.0038). Although the values of apoptotic index detected in the vitamin E group were lower compared with the varicocele group, the difference was not significant. This study proposes that ROS production and apoptosis in the testicles were induced with experimental varicocele. Vitamin E had a protective role. An increased rate of apoptosis with experimental varicocele suggests a molecular alteration, which may involve ROS overproduction as the triggering mechanism. Consequently, this study indicates an association between varicocele and infertility at molecular level through stimulation of ROS and apoptosis.  相似文献   
73.
Proton-observed carbon-edited (POCE) NMR spectroscopy is commonly used to measure 13C labeling with higher sensitivity compared to direct 13C NMR spectroscopy, at the expense of spectral resolution. For weakly coupled first-order spin systems, the multiplet signal at a specific proton chemical shift in POCE spectra directly reflects 13C enrichment of the carbon attached to this proton. The present study demonstrates that this is not necessarily the case for strongly coupled second-order spin systems. In such cases NMR signals can be detected in the POCE spectra even at chemical shifts corresponding to protons bound to 12C. This effect is demonstrated theoretically with density matrix calculations and simulations, and experimentally with measured POCE spectra of [3-13C]glutamate.  相似文献   
74.
PURPOSE: To investigate the effects of high dielectric material padding on RF field distribution in the human head at 7.0 T, and demonstrate the feasibility and effectiveness of RF passive shimming and focusing with such an approach. MATERIALS AND METHODS: The intensity distribution changes of gradient-recalled-echo (GRE) and spin-echo (SE) images of a human head acquired with water pads (dielectric constant = 78) placed in specified configurations around the head at 7.0 T were evaluated and compared with computer simulation results using the finite difference time domain (FDTD) method. The contributions to the B(1) field distribution change from the displacement current and conductive current of a given configuration of dielectric padding were determined with computer simulations. RESULTS: MR image intensity distribution in the human head with an RF coil at 7.0 T can be changed drastically by placing water pads around the head. Computer simulations reveal that the high permittivity of water pads results in a strong displacement current that enhances image intensity in the nearby region and alters the intensity distribution of the entire brain. CONCLUSION: The image intensity distribution in the human head at ultra-high field strengths can be effectively manipulated with high permittivity padding. Utilizing this effect, the B(1) field inside the human head of a given RF coil can be adjusted to reduce the B(1) field inhomogeneity artifact associated with the wave behavior (RF passive shimming) or to locally enhance the signal-to-noise ratio (SNR) in targeted regions of interest (ROIs; RF field focusing).  相似文献   
75.
Kamil W, Al Habashneh R, Khader Y, Al Bayati L, Taani D. Effects of nonsurgical periodontal therapy on C‐reactive protein and serum lipids in Jordanian adults with advanced periodontitis. J Periodont Res 2011; 46: 616–621. © 2011 John Wiley & Sons A/S Background and Objective: Data on whether periodontal therapy affects serum CRP levels are inconclusive. The aim of this study was to determine if nonsurgical periodontal therapy has any effect on CRP and serum lipid levels in patients with advanced periodontitis. Material and Methods: Thirty‐six systemically healthy patients, ≥ 40 years of age and with advanced periodontitis, were recruited for the study. Patients were randomized consecutively to one of two groups: the treatment group (n = 18) or the control group (n = 18). Treated subjects received nonsurgical periodontal therapy, which included oral hygiene instructions and subgingival scaling and root planing. Systemic levels of inflammatory markers [C‐reactive protein (CRP) and the lipid profile] were measured at baseline and 3 mo after periodontal therapy. Results: Nonsurgical periodontal therapy in the treatment group resulted in a significant reduction in the serum CRP level. The average CRP level decreased from 2.3 mg/dL at baseline to 1.8 mg/dL (p < 0.005) after 3 mo of periodontal therapy. The average reduction (95% confidence interval) in CRP was 0.498 (95% confidence interval = 0.265–0.731). In the treatment group, the reduction in CRP was significantly, linearly and directly correlated with the reduction in the plaque index, the gingival index and the percentage of sites with pocket depth ≥ 7 mm (Pearson correlation coefficient = 0.746, 0.425 and 0.621, respectively). Nonsurgical periodontal therapy had no effect on the lipid parameters. Conclusion: This study demonstrated that nonsurgical periodontal therapy results in a significant reduction in the serum CRP level. The effect of this outcome on systemic disease is still unknown.  相似文献   
76.
A phantom design method suitable for high-field MRI based on the RF field wave characteristics of sample and experimental validations at 7.0 T and 3.0 T are presented. The RF field distribution in a phantom with a given RF coil system is primarily determined by the sample size relative to the wavelength inside the sample, and the ratio between the displacement and conduction currents. Experimental results demonstrate that the MR image intensity patterns associated with wave behavior in human samples at a given field strength can be reproduced with a phantom at the same or different field strengths once the dimension and penetration constant are scaled by the corresponding wavelength in the sample medium.  相似文献   
77.
Hepatic artery aneurysms are responsible for 12% to 20% of all visceral arterial aneurysms. Because most patients are asymptomatic, this disease is generally diagnosed incidentally during radiologic examination. Aneurysm rupture develops in 14% to 80% of cases, depending on the aneurysmatic segment''s diameter and location, as well as other etiologic factors. Mortality rates associated with rupture range between 20% and 70%. Thus, early diagnosis and timely initiation of medical interventions are critical to improve survival rates. Here, we present a male patient, age 69 years, with a hepatic artery aneurysm that was detected incidentally. The 3-cm aneurysm was detected on contrast-enhanced computed tomography and extended from the common hepatic artery to the hepatic trifurcation. A laparotomy was performed using a right subcostal incision. After dissection of the hepatoduodenal ligament, the common, right, and left hepatic arteries, as well as the gastroduodenal artery, were suspended separately. Then, the aneurysmatic hepatic artery segment was resected, and the gastroduodenal artery stump was ligated. An end-to-end anastomosis was formed between the left and common hepatic arteries, followed by an end-to-end anastomosis formed between the right hepatic artery and splenic artery using a splenic artery transposition graft. Postoperative follow-up examinations showed that both hepatic arterial circulations were good, and no splenic infraction had developed.  相似文献   
78.
79.

Background

One proposed strategy to increase the success of irrigation and debridement with implant retention for the treatment of acute periprosthetic joint infection (PJI) is the use of dissolvable antibiotic-impregnated calcium sulfate beads to provide a local depot of antibiotics. The purpose of this study was to evaluate the outcome of such an approach.

Methods

Thirty-two patients with acute hematogenous (18 patients; 1 bilateral) or acute postoperative (14 patients) PJIs who underwent irrigation and debridement with implant retention and addition of antibiotic-impregnated calcium sulfate beads were retrospectively reviewed. PJI followed 27 total knee arthroplasties and 6 total hip arthroplasties. The most common infecting organisms were methicillin-sensitive Staphylococcus aureus (13 of 33) and Streptococcus (9 of 33). The primary outcome parameter was recurrence of infection according to the Musculoskeletal Infection Society criteria. Patients were followed up for a minimum of 3 months or until failure.

Results

At a mean of 12.7 months (range, 3-30 months), 16 of the 33 patients failed (48%). Acute hematogenous and acute postoperative PJI had similar failure rates at 47% and 50%, respectively (P = .88). Seven failures required a 2-stage exchange, while 8 patients were treated with chronic antibiotic suppression, being unwilling or unable to undergo further surgical intervention.

Conclusion

The addition of antibiotic-impregnated calcium sulfate beads does not appear to improve outcomes of irrigation and debridement with implant retention in the setting of acute hematogenous or acute postoperative PJI. Given the short follow-up in this report, this represents a best-case scenario and the overall failure rate may be higher with further follow-up.  相似文献   
80.
Hip fractures are the most devastating consequence of osteoporosis and impact 1 in 6 white women leading to a two‐ to threefold increased mortality risk in the first year. Despite evidence of inflammatory markers in the pathogenesis of osteoporosis, few studies have examined their effect on hip fracture. To determine if high levels of inflammation increase hip fracture risk and to explore mediation pathways, a case‐cohort design nested in a cohort of 4709 white women from the Study of Osteoporotic Fractures was used. A random sample of 1171 women was selected as the subcohort (mean age 80.1 ± 4.2 years) plus the first 300 women with incident hip fracture. Inflammatory markers interleukin‐6 (IL‐6) and soluble receptors (SR) for IL‐6 (IL‐6 SR) and tumor necrosis factor (TNF SR1 and TNF SR2) were measured, and participants were followed for a median (interquartile range) of 6.3 (3.7, 6.9) years. In multivariable models, the hazard ratio (HR) of hip fracture for women in the highest inflammatory marker level (quartile 4) was 1.64 (95% confidence interval [CI], 1.09–2.48, p trend = 0.03) for IL‐6 and 2.05 (95% CI, 1.35–3.12, p trend <0.01) for TNF SR1 when compared with women in the lowest level (quartile 1). Among women with 2 and 3–4 inflammatory markers in the highest quartile, the HR of hip fracture was 1.51 (95% CI, 1.07–2.14) and 1.42 (95% CI, 0.87–2.31) compared with women with zero to one marker(s) in the highest quartile (p trend = 0.03). After individually adjusting for seven potential mediators, cystatin‐C (a biomarker of renal function) and bone mineral density (BMD) attenuated HRs among women with the highest inflammatory burden by 64% and 50%, respectively, suggesting a potential mediating role. Older white women with high inflammatory burden are at increased risk of hip fracture in part due to poor renal function and low BMD. © 2014 American Society for Bone and Mineral Research.  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