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   1468篇
  免费   84篇
  国内免费   14篇
耳鼻咽喉   6篇
儿科学   24篇
妇产科学   9篇
基础医学   194篇
口腔科学   151篇
临床医学   133篇
内科学   413篇
皮肤病学   26篇
神经病学   48篇
特种医学   91篇
外科学   158篇
综合类   21篇
预防医学   121篇
眼科学   11篇
药学   101篇
中国医学   2篇
肿瘤学   57篇
  2023年   9篇
  2022年   25篇
  2021年   59篇
  2020年   22篇
  2019年   61篇
  2018年   44篇
  2017年   36篇
  2016年   43篇
  2015年   42篇
  2014年   78篇
  2013年   80篇
  2012年   126篇
  2011年   117篇
  2010年   73篇
  2009年   64篇
  2008年   84篇
  2007年   104篇
  2006年   97篇
  2005年   68篇
  2004年   44篇
  2003年   32篇
  2002年   26篇
  2001年   13篇
  2000年   9篇
  1999年   20篇
  1998年   17篇
  1997年   13篇
  1996年   10篇
  1995年   11篇
  1994年   4篇
  1993年   11篇
  1992年   9篇
  1990年   5篇
  1989年   9篇
  1988年   7篇
  1987年   4篇
  1986年   5篇
  1985年   7篇
  1983年   5篇
  1980年   4篇
  1979年   5篇
  1978年   4篇
  1975年   4篇
  1972年   5篇
  1969年   3篇
  1968年   4篇
  1967年   3篇
  1966年   3篇
  1964年   4篇
  1961年   4篇
排序方式: 共有1566条查询结果,搜索用时 15 毫秒
51.
52.
Trichomonas vaginalis causes trichomoniasis in humans, a sexually transmitted disease commonly treated with metronidazole (MTZ). MTZ is known to cause undesirable side effects, and MTZ-resistant parasites have been reported. Thus, the development of an alternative treatment is desirable. Miltefosine (MLT) is an alkylphosphocholine synthetic lipid analogue that displays antiparasitic activity against Leishmania, Trypanosoma cruzi, Entamoeba histolytica, Acanthamoeba spp., Giardia lamblia, T. vaginalis and some fungi. Moreover, it has been used for oral treatment of visceral leishmaniosis in several countries. Here, we analysed the MLT-induced antiproliferative effect on T. vaginalis as well its effect on the fine structure and viability of the parasite. We observed a dose-dependent effect with an IC50 of 14.5 and 20 μM after 24 and 48 h, respectively. Furthermore, reversibility assays demonstrated that new incubations were necessary in order to maintain the antiproliferative effect. Ultrastructural analyses demonstrated that MLT induced several alterations, including the appearance of wrinkled and rounded cells, membrane blebbing, intense vacuolization and nuclear condensation, all indicative of cell death by apoptosis. In addition, the quantitative analyses of the viability assays using combined markers of live and dead cells demonstrated that treatment with the IC50 concentration of MLT significantly reduced the number of viable parasites compared with untreated cells. Taken together, these observations suggest that MLT is a promising compound for the treatment of trichomoniasis.  相似文献   
53.

The aquaculture growth can be followed by the occurrence of more and new pathogenic agents, since the production leads to higher fish densities in confined areas more appropriate to the appearance and propagation of pathologies. Copper sulfate has been widely used in preventing and controlling fish parasites. The objective of this study is to investigate the effects of copper treatments in the fish tissues (bioaccumulation and histological changes in different organs), mortality and evaluate what happens during the recovery period. White sea bream (Diplodus sargus) were exposed to copper sulfate (0.25 and 0.5 mg L−1) during 60 days followed with a 75-day recovery period. The results showed that the concentration of copper in fish liver was significantly higher in the 0.5 mg L−1 treatment than in the 0.25 mg L−1 treatment. Conversely, copper load in the muscle did not differ significantly between treatments and control. Copper levels in muscle, and especially in liver, increased during copper exposure (up to 60 days). In summary, at higher concentrations copper sulfate treatment (0.5 mg L−1) might be toxic to fish, which showed histological alterations and copper accumulation in their tissues, mainly in the liver. Nevertheless, individuals returned to their original state after a 75-day recovery period and the tested copper concentrations does not represents risk for food safety.

  相似文献   
54.
ObjectivesUltra-high-speed (UHS) videography was used to visualize the fracture phenomena at the resin–dentin interface during micro-tensile bond strength (μTBS) test. We also investigated whether UHS videography is applicable for failure-mode analysis.MethodsTen human mid-coronal dentin surfaces were bonded using Clearfil SE Bond either in self-etching (SE) or etch-and-rinse (ER) mode. After 24-h water storage, the samples were cut into beams for μTBS test and tested at a cross-head speed of 1 mm/min. The fracture phenomena at the bonded interface were captured using a complementary metal–oxide–semiconductor digital UHS camera at 299,166 frames per second. The failure modes were classified using UHS videography, followed by scanning electron microscopy (SEM) analysis. The failure-mode distributions determined by UHS videography and SEM analysis were statistically analyzed using Fisher’s exact test with Bonferroni correction.ResultsThe crack-propagation speed exceeded 1,500 km/h. No significant difference was found between the SEM and UHS videography failure-mode distributions in the SE mode. A significant difference appeared between them in the ER mode. Significant differences in the incidence of cohesive failures within the adhesive and at the adhesive–composite interface between the SE and ER modes were identified by both SEM and UHS videography.SignificanceUHS videography enabled visualization of the fracture dynamics at the resin– dentin interfaces under tensile load. However, the resolution at such high frame rate was insufficient to classify the failure mode as precisely as that of SEM. Nevertheless, UHS videography can provide more detailed information about the fracture origin and propagation.  相似文献   
55.
56.
Using the Gomco circumcision clamp and sealing the wound with tissue adhesive results in a minimally invasive circumcision suitable for all age groups beyond the neonatal period. It is easy to perform and can be performed by generalists with local anaesthetic and standard instruments.  相似文献   
57.
58.
Limited information is available about gender and ethnic differences in red cell distribution width (RCDW) with regard to its relation to mortality in a population free of cardiovascular (CV) disease and diabetes. To assess gender and ethnic differences in RCDW and their effect on the association between RCDW and mortality, the Third National Health and Nutritional Examination Survey (n = 15,460, 1988 to 1994) data were examined. Multivariate adjusted Cox proportional hazard analysis was performed to assess effect of gender and ethnicity on the association between RCDW and mortality (total, CV disease, and coronary heart disease [CHD]). RCDW (mean ± SE) was greater in black women (13.1 ± 0.03) and men (13.4 ± 0.02) compared to women of white (12.9 ± 0.02) and other (13.0 ± 0.07) ethnicities and men of white (13.3 ± 0.02) and other (13.3 ± 0.07) ethnicities, respectively (p <0.001). The interaction between RCDW and gender was statistically significant for all study outcomes (p <0.001) but nonsignificant for RCDW and ethnicity. After adjusting for key variables, RCDW in women was associated with adjusted hazard ratios of 1.22 (95% confidence interval [CI] 1.14 to 1.31) for all-cause mortality, 1.17 (95% CI 1.07 to 1.28) for CV deaths, and 1.18 (95% CI 1.03 to 1.35) for CHD deaths; in men, adjusted hazard ratios were 1.29 (95% CI 1.20 to 1.38) for all-cause mortality, 1.27 (95% CI 1.17 to 1.37) for CV deaths, and 1.25 (95% CI 1.13 to 1.39) for CHD deaths (p <0.05 for all). In conclusion, blacks and men have significantly greater RCDWs compared to whites and women. Greater RCDW is associated with a greater risk of mortality in men compared to women, whereas no effect modification is observed by ethnicity.  相似文献   
59.

Objective

This randomized double-blind clinical trial compared the performance of posterior composite restorations with or without bevel, after 1-year follow-up.

Material and Methods

Thirteen volunteers requiring at least two posterior composite restorations were selected. Twenty-nine cavities were performed, comprising 14 without bevel (butt joint) and 15 with bevel preparation of the enamel cavosurface angle. All cavities were restored with simplified adhesive system (Adper Single Bond) and composite resin (Filtek P60). A halogen light curing unit was used through the study. Restorations were polished immediately. Analysis was carried out at baseline, after 6 months and after 1 year by a calibrated evaluator (Kappa), according to the FDI criteria. Data were statistically analyzed by Mann-Whitney test (p<0.05).

Results

Beveled and non-beveled cavities performed similarly after 1 year follow-up, regarding to fractures and retention, marginal adaptation, postoperative hypersensitivity, recurrence of caries, surface luster and anatomic form. However, for surface and marginal staining, beveled cavities showed significantly better performance (p<0.05) than butt joint restorations.

Conclusions

It was concluded that the restorations were acceptable after 1 year, but restorations placed in cavities with marginal beveling showed less marginal staining than those placed in non-beveled cavities.  相似文献   
60.
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