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   4966篇
  免费   277篇
  国内免费   33篇
耳鼻咽喉   156篇
儿科学   75篇
妇产科学   257篇
基础医学   634篇
口腔科学   49篇
临床医学   437篇
内科学   1421篇
皮肤病学   49篇
神经病学   436篇
特种医学   90篇
外科学   619篇
综合类   31篇
一般理论   1篇
预防医学   157篇
眼科学   68篇
药学   403篇
中国医学   4篇
肿瘤学   389篇
  2023年   23篇
  2022年   18篇
  2021年   355篇
  2020年   83篇
  2019年   120篇
  2018年   147篇
  2017年   110篇
  2016年   128篇
  2015年   163篇
  2014年   209篇
  2013年   284篇
  2012年   405篇
  2011年   419篇
  2010年   205篇
  2009年   142篇
  2008年   346篇
  2007年   378篇
  2006年   328篇
  2005年   308篇
  2004年   330篇
  2003年   304篇
  2002年   217篇
  2001年   18篇
  2000年   19篇
  1999年   23篇
  1998年   25篇
  1997年   14篇
  1996年   8篇
  1995年   12篇
  1994年   13篇
  1993年   8篇
  1992年   12篇
  1991年   6篇
  1990年   9篇
  1989年   7篇
  1988年   7篇
  1987年   4篇
  1986年   16篇
  1985年   6篇
  1983年   3篇
  1982年   5篇
  1981年   8篇
  1980年   5篇
  1978年   4篇
  1977年   3篇
  1976年   3篇
  1975年   3篇
  1971年   2篇
  1968年   2篇
  1959年   1篇
排序方式: 共有5276条查询结果,搜索用时 31 毫秒
1.
Animal and human studies suggest fish oil and green tea may have protective effect on prostate cancer. Fatty acid synthase (FAS) has been hypothesized to be linked to chemoprotective effects of both compounds. This study evaluated the independent and joint effects of fish oil (FO) and green tea supplement (epigallocatechin-3-gallate, EGCG) on FAS and Ki-67 levels in prostate tissue. Through a double-blinded, randomized controlled trial with 2 × 2 factorial design, 89 men scheduled for repeat prostate biopsy following an initial negative prostate biopsy were randomized into either FO alone (1.9 g DHA + EPA/day), EGCG alone (600 mg/day), a combination of FO and EGCG, or placebo. We used linear mixed-effects models to test the differences of prostate tissue FAS and Ki-67 by immunohistochemistry between pre- and post-intervention within each group, as well as between treatment groups. Results did not show significant difference among treatment groups in pre-to-post-intervention changes of FAS (P = 0.69) or Ki-67 (P = 0.26). Comparing placebo group with any of the treatment groups, we did not find significant difference in FAS or Ki-67 changes (all P > 0.05). Results indicate FO or EGCG supplementation for a short duration may not be sufficient to produce biologically meaningful changes in FAS or Ki-67 levels in prostate tissue.  相似文献   
2.
The current literature suggests that the antibacterial effect of leukocyte- and platelet-rich plasma (L-PRP) is directly related to platelet and leukocyte concentrations. The aim of this study was twofold: first, to evaluate the antimicrobial effect of L-PRP against selected bacterial strains in vitro, and second, to correlate this effect with leukocyte and platelet content in the final concentration. Blood was collected from 20 healthy males, and L-PRP, acellular plasma (AP), and autologous thrombin were consecutively prepared. Flow cytometry analysis of the blood, L-PRP, and AP was performed. The L-PRP gel, liquid L-PRP, and thrombin samples were tested in vitro for their antibacterial properties against seven selected bacterial strains using the Kirby–Bauer disk-diffusion method. There was notable antimicrobial activity against selected bacterial strains. No statistically significant correlations between antimicrobial activities and the platelet concentration in L-PRP were observed. Statistically significant positive correlations between selected leukocyte subtypes and antimicrobial activity were noted. A negative correlation was found between elevated monocyte count and antimicrobial activity of L-PRP against one bacterial strain studied. L-PRP possesses antimicrobial activity and can be potentially useful in the fight against certain postoperative infections. The bactericidal effect of L-PRP is caused by leukocytes, and there exists a relationship among selected leukocyte subtypes and L-PRP antimicrobial activity.  相似文献   
3.
4.
5.
Proprioception is a term covering together joint position sense, kinesthesia and integration of these stimuli in the central nervous system which is needed to keep homeosthasis of joints during motion. The aim of this study is to present authors originally created measuring device working according to the principles of Barrett, aiming at evaluation of proprioception of the knee. The construction of this device is based on the Summer chair, model UPR-01B, working in connection with Bosh goniometer DWM-40L measuring angles with a precision of 0,1 degree. The device presented in this study fulfills all criteria required for this kind of apparatus and may be an alternative to other constructs produced commercially and available on the market.  相似文献   
6.
Objective: Electroporation mediated transfer of plasmid DNA into peripheral muscle results in high transfection efficiency. The aim of this study was to investigate the effect of gene transfer of human IL-10 (hIL-10) into the tibialis anterior muscle (MTA) in combination with low dose Cyclosporine A (CsA) on acute rejection of lung allografts in the rat. Methods: Lung allotransplantation was performed from male BN donor to male Fisher F344 rats. Gene transfer was achieved by intramuscular injection into the MTA of the recipient followed by electroporation (4×20 ms impulses at 200 V/cm) 24 h prior to the transplantation. Group A (n=5) received CsA (2.5 mg/kg bw ip) for 5 days post-transplant and group B (n=5) 2.5 μg of PCIK hIL-10 (plasmid expression vector containing human CMV immediate early gene promoter and enhancer) and a low dose CsA (2.5 mg/kg bw i.p.). Graft function was assessed by blood gas at day 5 after exclusion of the native lung. Animals were sacrificed and blood was drawn to measure serum hIL-10 levels (ELISA) and tissue was sampled for histological grading of rejection. Results: Local expression of hIL-10 was confirmed at the mRNA level by in situ hybridization. All group A control animals showed severe signs of rejection. At day 5 all grafts in group B showed good gas exchange mean PaO2 233±123 mmHg, vs 44±8 mmHg in group A. Histological examination revealed moderate to severe rejection in all animals in group A (IIIB, ISHLT) in contrast to low moderate rejection in group B (II–IIIA). hIL-10 serum levels on day 5 were 14±7 pg/ml in group B vs. 0 in group A. Conclusions: Electroporation mediated hIL-10 overexpression in a peripheral muscle of the recipient in combination with low dose CsA reduces acute rejection in this model of rat lung allotransplantation.  相似文献   
7.
The objectives of this study were to determine the relationship between carotid-femoral (cfPWV) and aortic pulse wave velocity (aPWV) and to compare their modulators and association with coronary artery disease (CAD). We studied 107 consecutive patients (68 men) with a mean age of 60.49+/-8.31 years who had stable angina and had been referred for coronary angiography. cfPWV and aPWV were measured simultaneously during cardiac catheterization using the Complior device and aortic pressure waveform recordings, respectively. Based on the presence or absence of significant coronary artery stenosis (CAS) patients were subdivided into a CAS+ or CAS- group. The mean values of cfPWV and aPWV were 10.65+/-2.29 m/s and 8.78+/-2.24 m/s, respectively. They were significantly higher in the CAS+ (n=71) compared with the CAS- (n=36) group and predicted significant CAS independently of cardiovascular risk factors and mean or systolic aortic blood pressure. aPWV and cfPWV were significantly correlated (r=0.70; p<0.001) but the degree of correlation differed significantly (p<0.03) between the CAS+ (r=0.74, p<0.001) and CAS- group (r=0.46, p=0.003). Age and mean aortic blood pressure were independent predictors for aPWV as well as cfPWV. In the receiver operating characteristic (ROC) analysis, aPWV and cfPWV had similar accuracy in identification of significant CAS (AUC [area under the ROC curve]=0.76 and 0.69, respectively; p=0.13). However, neither cfPWV nor aPWV was effective at differentiating the extent of CAD. In conclusion, aPWV and cfPWV are highly correlated parameters with similar determinants and comparable accuracy in predicting significant CAS. The strength of correlation between these two indices differed significantly between subjects with and those without CAS.  相似文献   
8.
There is no universally accepted method to determine effective therapy for central sleep apnea (CSA). Continuous positive airway pressure (CPAP) applied acutely most often does not eliminate apneas and hypopneas. We hypothesized that the application of two or more therapeutic modalities after the diagnostic phase of polysomnography, a multi-modality titration study (MMTS), would identify a successful CSA treatment more often than a standard split-night study (SNS) and obviate the need for additional polysomnograms to determine a successful therapy. We retrospectively analyzed polysomnograms of patients diagnosed with CSA at our Sleep Disorders Center. We defined a therapy trial that resulted in an apnea–hypopnea index < 10 with at least one treatment modality as a therapeutic success. One hundred fifteen patients with CSA were studied. Sixty-six patients (57.4%) underwent a SNS, and 49 patients (42.6%) underwent a MMTS. SNS yielded only 8/66 (12.1%) successes on the first night, whereas a MMTS yielded 19/49 (38.8%) successes (p = 0.001, two-tailed Fishers exact). Patients who underwent a SNS eventually had similar rate of success as patients studied with MMTS (60.6 vs 63.3%, NS), but required more testing. Adaptive servo-ventilation was the most successful modality tested, yielding 36/46 (78.3%) successes. Trials of additional modalities following a failed trial of CPAP often produce a successful option that may guide therapy in patients with CSA. This approach may lead to establishing the diagnosis and treatment plans faster, while reducing unnecessary testing.  相似文献   
9.
OBJECTIVE: The aim of this study was to assess changes in early and late haemodynamic status after the Norwood procedure (NP), caused by the implementation of right ventricle-to-pulmonary artery shunt (RV-PA). METHODS: A consecutive series of 68 children with hypoplastic left heart syndrome underwent NP: Group 1 (n=31) with the application of a modified Blalock-Taussig shunt and Group 2 (n=37) with RV-PA. Haemodynamic data from the early postoperative period (72 h after the operation) and cardiac catheterisation data, as well as blood tests before the hemi-Fontan procedure (HF) were analysed. Univariate (chi(2) test, Mann-Whitney's and Student's t-tests) and multiple regression analysis were carried out. RESULTS: In Group 1, circulatory collapse requiring resuscitation occurred in 15 (48.4%) children, within 72 h after the procedure. The resuscitation was unsuccessful in nine (29%) cases. The operative mortality (30 days) was 35%. In Group 2, two (5%) children died within the early and two (5%) within the late postoperative period. The postoperative course in the remaining children from Group 2 was uneventful. In Group 2 there was a significantly higher mean diastolic pressure after NP (P<0.05). The arterial pulse pressure after NP was significantly lower in Group 2 (P<0.05). Before HF, the application of RV-PA was associated with a lower Qp:Qs ratio (P=0.020), lower aortic pulse pressure (P=0.004) and lower aortic oxygen saturation (P=0.039). CONCLUSIONS: A stable haemodynamic status due to independent coronary perfusion, higher diastolic and lower pulse pressure is the most advantageous effect of RV-PA, resulting in a lower mortality and morbidity after NP. A lower Qp:Qs ratio eliminates the danger of the ventricular volume overload and ensures good conditions for the development of the pulmonary circulation before HF.  相似文献   
10.
Experimental and clinical tests proved that cultured, autologous chondrocytes retain their properties and have ability to reconstruct hyaline-like cartilage, which represents chemical composition and biomechanical characteristics similar to normal hyaline cartilage. The aim of this part of the study was microscopic evaluation of repair tissue structural integrity and surface regularity after autologous chondrocyte transplantation. MATERIAL AND METHODS: Repair of partial thickness cartilage defect (ICRS III(o) grade) on distal femur joint surface was evaluated (25 adolescent rabbits). Procedures were performed in two groups: I--autologous chondrocyte transplantation under periosteal flap, II--periosteal graft. Chondrocytes were isolated from the cartilage specimens by enzymatic digestion and cultured in vitro. The follow-up periods were established at 4, 8, 12 weeks. Repair tissue was evaluated microscopically according to modified O'Driscoll scale. RESULTS: In group I, 4 weeks after the procedure surface of the reconstructed tissue was irregular. 8- and 12-week observation found the surface regular and plain, and repair tissue exhibited complete structural integrity. In group II, in all follow-up periods regenerate surface was irregular, there was many fissures and cracks in graft tissue, and in several cases--regenerate disintegration. CONCLUSION: Obtained results indicate, that hyaline-like cartilage reconstructed after autologous chondrocyte transplantation was characterized by regular, plain surface and complete structural integrity.  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