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   1924篇
  免费   109篇
  国内免费   7篇
耳鼻咽喉   33篇
儿科学   88篇
妇产科学   33篇
基础医学   185篇
口腔科学   52篇
临床医学   166篇
内科学   452篇
皮肤病学   50篇
神经病学   93篇
特种医学   59篇
外科学   273篇
综合类   73篇
预防医学   91篇
眼科学   66篇
药学   166篇
中国医学   15篇
肿瘤学   145篇
  2023年   20篇
  2022年   46篇
  2021年   103篇
  2020年   46篇
  2019年   59篇
  2018年   73篇
  2017年   34篇
  2016年   72篇
  2015年   55篇
  2014年   100篇
  2013年   91篇
  2012年   122篇
  2011年   142篇
  2010年   89篇
  2009年   67篇
  2008年   101篇
  2007年   104篇
  2006年   93篇
  2005年   66篇
  2004年   69篇
  2003年   60篇
  2002年   48篇
  2001年   43篇
  2000年   30篇
  1999年   34篇
  1998年   14篇
  1997年   13篇
  1996年   10篇
  1995年   11篇
  1994年   8篇
  1993年   5篇
  1992年   19篇
  1991年   17篇
  1990年   18篇
  1989年   19篇
  1988年   21篇
  1987年   17篇
  1986年   18篇
  1985年   13篇
  1984年   10篇
  1983年   12篇
  1982年   2篇
  1981年   2篇
  1979年   12篇
  1978年   9篇
  1977年   7篇
  1976年   3篇
  1973年   5篇
  1970年   2篇
  1959年   1篇
排序方式: 共有2040条查询结果,搜索用时 31 毫秒
991.
International Journal of Paediatric Dentistry 2012; 22: 197–202 Objective. It is a well‐established fact that colonization of S. mutans occurs early in life. The purpose of this study is to determine the correlation between mode of delivery and other associating factors with colonization of oral S. mutans in the infants. Methods. The newborns were divided into two groups according to the mode of delivery: Infants who were delivered by either caesarean section (Group‐C) or vaginally (Group‐V). A total number of 60 mother–infant pairs were included and followed for 1 year. The swab samples were collected for the detection of S. mutans. Results. Analysis of data demonstrated the possible influence of prolonged bottle feeding (P = 0.007), socioeconomic status (P = 0.00030) and tasting of food by the mothers (P = 0.0065) on the initial acquisition of S. mutans in the oral cavity of infants. Conclusion. The causes for initial acquisition of oral S. mutans in infants were postnatal factors like feeding and oral hygiene practices.  相似文献   
992.
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences - Ephedra gerardiana Wall. (Ephedraceae) is an evergreen xerophytic shrub and is used in Indian and Chinese...  相似文献   
993.
Fibrillary glomerulopathy (FG) can occur either alone or co-existing with other proteinuric glomerular disorders. FG has been associated with poor renal outcomes leading to End Stage Renal Disease (ESRD). Since FG is a relatively rare disorder, limited information is available concerning treatment protocols. We present two patients with FG who were treated with rituximab after they had already progressed to stage 3 chronic kidney disease (CKD) with worsening proteinuria. Rituximab therapy resulted in long-term stabilization of renal function.  相似文献   
994.

Introduction

Hypercoagulability due to high coagulation factor levels resulting from host inflammatory response to cancer contributes to an increased risk of venous thromboembolism (VTE) in cancer patients. Central venous catheters (CVCs) further heighten this risk. Activated partial thromboplastin time (aPTT) can be used to broadly screen for elevated levels of relevant coagulation factors. Our objective was to determine if a shortened aPTT ratio (coagulation time of test- to- reference plasma) was a predictor of CVC-associated VTE in cancer patients.

Materials and Methods

We performed a retrospective case–control study on cancer patients undergoing tunneled CVC insertion at our center from 1999 to 2006 and identified 40 patients who had CVC-associated VTE. VTE was confirmed with color duplex ultrasonography or computed tomography scan. For each case, we obtained 5 controls that had the same cancer diagnosis and were matched on the following factors: age, chemotherapy, hormone therapy (if applicable), tobacco use, TNM staging and year of diagnosis. All patients had aPTT testing within 30 days prior to surgery. We compared aPTT and aPTT ratio between cases and controls using Wilcoxon two sample test.

Results

aPTT ratio was significantly shorter in patients with CVC-related VTE as compared to controls [0.86 (95% confidence interval (CI) 0.78, 0.94) vs. 0.98 (0.94, 1.01), p = 0.0003]. Mean aPTT was also significantly shorter. [25.6 seconds (95% CI 23.2, 27.9) vs. 28.1 (26.9, 29.3), p = 0.001] aPTT ratios of the controls tended to spread across larger aPTT ratio values whereas those of cases tended to clustered around the mean.

Conclusions

Cancer patients undergoing catheter placement who develop CVC-associated VTE have a shorter aPTT and aPTT ratio than those who do not develop VTE. aPTT, a simple and inexpensive test might be useful as a predictor of CVC-associated VTE risk in cancer patients.  相似文献   
995.
Clinical Rheumatology - Systemic autoinflammatory diseases (SAIDs) may not always present with typical clinical findings of a monogenic disease. We aimed to genetically screen and diagnose these...  相似文献   
996.
Naturally occurring lycopene has been reported for its chemopreventive and chemotherapeutic efficiency in various cancers, but its exceptional lipophilicity, poor aqueous solubility, instability, and consequently poor bioavailability limit its usage as a chemopreventive and chemotherapeutic agent. The present study aimed to synthesize co-polymeric nanoparticle-encapsulated formulations of commercial lycopene (NLY) and extracted lycopene (NLX) and evaluate their in vitro anticancer activity and inhibitory effect on 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin inflammation and tumorigenesis in Swiss albino mice. To prepare the nanoparticle-encapsulated formulations of lycopene, thermosensitive PNIPAAM–PEG-based co-polymeric nanoparticles were synthesized and characterized by FTIR spectroscopy, NMR spectroscopy, DLS, and TEM. Nanolycopene, unlike free lycopene, could be readily dispersed in aqueous media. Nanolycopene demonstrated stronger antioxidant activity and comparable in vitro anticancer efficacy to free lycopene against the melanoma cell line B16. Furthermore, nanolycopene showed comparable reduction of TPA-induced skin edema, expression of COX-2, and oxidative stress response. Additionally, it showed significant inhibition of tumor promotion. It also altered Bax and Bcl2 expressions, which led to the induction of apoptosis. The results also supported that the extracted lycopene-encapsulated nanoparticles may be a good alternative to the expensive commercial lycopene for cancer treatment.

Nanolycopene demonstrated strong antioxidant activity and enhanced chemopreventive effect on skin tumorigenesis in mouse.  相似文献   
997.
In this work, γ-ray irradiation effects on pentacene thin films are investigated in terms of the change in the crystallinity, and electronic structure as well as chemical states of the film. The pentacene films are γ-irradiated up to 3 kGy and then characterized using synchrotron X-ray diffraction, near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy. We found that γ-ray irradiation creates defects, resulting in a decrease of X-ray diffraction intensity both in the plane normal and in-plane directions. From angle dependent NEXAFS; the transition of C 1s to π* orbital for irradiated samples increases; suggesting that the unoccupied π* states enhance due to defects or radical formation in pentacene thin films. Additionally, the in-plane resistivity shows a decreasing trend of resistance after irradiation. This trend of increase in conductivity is also consistent with C 1s to π transition, which manifests the increase in carrier concentration. Hall effect measurements further confirmed the increase in carrier concentration as a function of dose; however, the mobility of the sample decreases as the dose rate increases due to the defects created. By post-irradiation annealing, the thin film phase diffraction intensity can be recovered. Altogether, the anisotropic studies on pentacene films disclosed that the irradiation leads to defect formation along in-plane and plane normal directions. Overall, these results suggest that pentacene is one of the robust organic electronic materials; whose structure remains mostly intact even after irradiation up to a dose of 3 kGy.

In this work, γ-ray irradiation effects on pentacene thin films are investigated in terms of the change in the crystallinity, and electronic structure as well as chemical states of the film.  相似文献   
998.
Paraben is a phenolic derivative of benzoic acid extensively used as preservatives in food, pharmaceutical, and cosmetic industries due to its antimicrobial characteristics. The objective of this study was to evaluate the in vitro genotoxic effects of paraben in human lymphocyte cultures. Cells were analyzed by cytokinesis-block micronucleus (CBMN), chromosome aberration (CA), sister chromatid exchange (SCE), and comet tests. For CBMN, CA, and SCE assays, the human lymphocytes were isolated from healthy donors and incubated with 500, 250, 100, and 50?µg/mL of paraben for 24 and 48?h, and for comet assay, cells were exposed to 1000, 750, 500, and 250?µg/mL of paraben for an hour. Results showed that numbers of MN and SCEs were not significant in the cells exposed to paraben when compared to the solvent control. However, 500 and 250?µg/mL of paraben induced the CA after 24?h. Also, we observed a significant decrease in the cytokinesis-block proliferation index in cells exposed 250–500?µg/mL paraben for 24?h, and 100, 250, and 500?µg/mL for 48?h. The mitotic index was also decreased at all concentrations and periods. However, the proliferation index was statistically decreased at all concentrations after 48?h treatments. Only the highest concentration of paraben caused DNA migration (mean tail length) in human lymphocytes analyzed by Comet assay. Taken together, results indicated that paraben had cytotoxic effects and caused genotoxicity by affecting directly chromosomes and DNA in human lymphocyte cells in vitro, and may have genotoxic potential for human.  相似文献   
999.

Background  

Although subarachnoid hemorrhage (SAH) serves as a good model to study heart–brain interactions, neither the changes on the single ventricular action potential (SVAP) and contraction nor the effects of possible cardioprotective agents have been investigated.  相似文献   
1000.
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