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   2244篇
  免费   137篇
  国内免费   10篇
耳鼻咽喉   23篇
儿科学   69篇
妇产科学   32篇
基础医学   248篇
口腔科学   31篇
临床医学   162篇
内科学   504篇
皮肤病学   29篇
神经病学   116篇
特种医学   45篇
外科学   453篇
综合类   54篇
预防医学   153篇
眼科学   58篇
药学   265篇
中国医学   23篇
肿瘤学   126篇
  2023年   18篇
  2022年   17篇
  2021年   97篇
  2020年   57篇
  2019年   74篇
  2018年   76篇
  2017年   40篇
  2016年   55篇
  2015年   59篇
  2014年   100篇
  2013年   118篇
  2012年   153篇
  2011年   156篇
  2010年   82篇
  2009年   72篇
  2008年   114篇
  2007年   124篇
  2006年   108篇
  2005年   115篇
  2004年   92篇
  2003年   79篇
  2002年   60篇
  2001年   38篇
  2000年   47篇
  1999年   46篇
  1998年   9篇
  1997年   13篇
  1995年   8篇
  1994年   11篇
  1993年   9篇
  1992年   28篇
  1991年   31篇
  1990年   24篇
  1989年   26篇
  1988年   29篇
  1987年   13篇
  1986年   17篇
  1985年   19篇
  1984年   20篇
  1983年   17篇
  1981年   11篇
  1980年   5篇
  1979年   18篇
  1978年   10篇
  1977年   9篇
  1976年   9篇
  1975年   9篇
  1974年   11篇
  1973年   9篇
  1972年   6篇
排序方式: 共有2391条查询结果,搜索用时 15 毫秒
1.
2.
Well‐known causes of zinc deficiency, also referred to as acrodermatitis enteropathica (AE), include defects in intestinal zinc transporters and inadequate intake, but a rare cause of acquired zinc deficiency discussed here is an iatrogenic nutritional deficiency caused by parenteral nutrition administered without trace elements. While zinc‐depleted parenteral nutrition causing dermatosis of acquired zinc deficiency was first reported in the 1990s, it is now again relevant due to a national vitamin and trace element shortage. A high index of suspicion may be necessary to diagnose zinc deficiency, particularly because early clinical findings are nonspecific. We present this case of acquired zinc deficiency in a patient admitted to a pediatric intensive care unit for respiratory distress and atypical pneumonia, who subsequently developed a severe bullous eruption due to iatrogenic zinc deficiency but was treated effectively with enteral and parenteral zinc supplementation, allowing for rapid re‐epithelialization of previously denuded skin.  相似文献   
3.
4.
5.

Arbuscular mycorrhizal (AM) fungi are well known root symbionts in heavy metal polluted soils. To assess AM fungal association and their contribution to the host plants naturally growing on a highly chromium (Cr) contaminated soil, the present study has been undertaken. The soil of the study site was contaminated with 32,562 ppm Cr coming from tannery industry. The study site was dominated by Cynodon dactylon (L.) Pers., Parthenium hysterophorus L., Croton bonplandianum Baill and Prosopis juliflora (Sw.) DC. High mycorrhizal colonization (31–83%) and low spore population (5–11 spores/g) was recorded. The diversity of AM fungi was very low because of stress caused by Cr. Only seven AM fungal isolates have been recovered. Funneliformis mosseae, Rhizophagus intraradices, Funneliformis geosporus and Glomus sinuosum have been recovered from two hosts, while, Rhizophagus fasciculatus, Glomus aggregatum and Acaulospora scrobiculata from single host only. Cr accumulation in the roots were analyzed through AAS and correlated with various mycorrhization parameters. The results of correlation through PCA showed that, various mycorrhization parameters were under strong influence of Cr accumulation in the roots. Furthermore, all the AM fungi showed certain adaptive features like compact sporocarp, thick spore wall, sloughing outermost wall layer and formation of water stable aggregates. Low species diversity, high mycorrhizal colonization, presence of adaptive features and strong correlation of mycorrhizal parameters with the Cr accumulation in the roots clearly indicated that, these AM fungi have contributed to the Cr accumulation and tolerance to the host plants in Cr sludge deposit.

  相似文献   
6.
Gastric cancer (GC) is the third leading cause of cancer mortality worldwide, with an overall 5-y survival rate of 25%. The majority of GCs are caused by infectious agents, including the bacterium Helicobacter pylori (H. pylori) and Epstein–Barr virus (EBV). Furthermore, inappropriate repair of DNA damage can also result in genomic instability, which has shown to be a key factor in carcinogenesis of different regions including gastric region. Present study was designed to explore the association between base excision repair pathway genes, PARP1 and APEX1 and gastric pathology and H. pylori infection. Two hundred gastric cancer tissue samples (114 H. pylori positive and 86 H. pylori negative) and adjacent uninvolved area taken as controls was used for expression analysis of BER pathway genes at mRNA level and protein levels using quantitative PCR (qPCR) and immunohistochemistry (IHC) respectively. Oxidative stress and DNA damage was also determined by measuring the level of antioxidant enzymes and comet assay respectively. Significant upregulation in PARP1 (p < 0.001) and APEX1 (p < 0.02) was observed in GC tissue samples compared to controls and this upregulation was more pronounced in H. pylori positive cases (HPGC) (PARP1, p < 0.02: APEX1, p < 0.04) than H. pylori negative cases (HNGC). Upregulation of BER pathway genes in HPGC was found correlated with smoking status (p < 0.0001), T stage (p < 0.01) and lymph node metastasis (p < 0.03). Moreover, immunohistochemical staining of BER pathway genes was found correlated with a number of clinicopathological characteristics such as tumor type (p < 0.03), tumor size (p < 0.01) and lymph node metastasis (p < 0.01). Expression levels of APEX1 and PARP1 gene also correlated with increased oxidative burden (p < 0.0001) and DNA damage (p < 0.001) in GC patients. Survival analysis showed that upregulation of PARP1 gene was associated with poor overall survival outcome of gastric cancer patients (HR = 2.04 (95% CI = 1.10–3.76; p < 0.02). Univariate and multivariate cox regression analysis showed the upregulated PARP1 gene (HR = 5.03; 95%CI (2.22–11.35); p = 0.0001), positive smoking status (HR = 3.58; 95%CI (1.67–7.65); p = 0.001), positive status for H pylori infection (HR = 4.38; 95%CI (1.82–10.56); p = 0.001) and advance N-stage (HR = 5.29; 95%CI (2.28–12.24); p = 0.0001) were independent prognostic factors for gastric cancer and may serve as a valuable biomarker for the diagnosis and progression of GC and can be helpful in developing individualized treatment strategies for treating GC.  相似文献   
7.
BackgroundExcessive consumption of ethanol is known to activate the mTORC1 pathway and to enhance the Collapsin Response Mediator Protein-2 (CRMP-2) levels in the limbic region of brain. The latter helps in forming microtubule assembly that is linked to drug taking or addiction-like behavior in rodents. Therefore, in this study, we investigated the effect of lacosamide, an antiepileptic drug and a known CRMP-2 inhibitor, which binds to CRMP-2 and inhibits the formation of microtubule assembly, on ethanol-induced conditioned place preference (CPP) in mice.MethodsThe behavior of mice following ethanol addiction and withdrawal was assessed by performing different behavioral paradigms. Mice underwent ethanol-induced CPP training with alternate dose of ethanol (2 g/kg, po) and saline (10 ml/kg, po). The effect of lacosamide on the expression of ethanol-induced CPP and on ethanol withdrawal associated anxiety and depression-like behavior was evaluated. The effect of drug on locomotor activity was also assessed and hippocampal CRMP-2 levels were measured.ResultsEthanol-induced CPP was associated with enhanced CRMP-2 levels in the hippocampus. Lacosamide significantly reduced the expression of ethanol-induced CPP and alleviated the levels of hippocampal CRMP-2 but aggravated withdrawal-associated anxiety and depression in mice.ConclusionThe present study demonstrated the beneficial effect of lacosamide in attenuation of expression of ethanol induced conditioned place preference via reduction of hippocampal CRMP-2 level. These findings suggest that lacosamide may be investigated further for ethanol addiction but not for managing withdrawal.  相似文献   
8.
The present investigation was aimed at studying the possible role of curcumin against N-nitrosodiethylamine (NDEA)-induced toxicity in albino rats. Administration of NDEA to rats at a concentration of 0.1 mg/ml in drinking water ad libitum for 21 days produced toxicity in them, which was evident from histopathological changes in the rat livers, and increased levels of blood serum enzyme markers, i.e. aspartate transaminase, alanine transaminase, alkaline phosphatase, and lactate dehydrogenase. In addition, the levels of oxidative stress markers like lipid peroxidation (LPO), protein carbonyl (PCC), and glutathione-S-transferase (GST) activity were elevated and the total glutathione (GSH) content was reduced in the livers. The administration of curcumin to rats at concentrations of 10, 20, and 40 mg/ml in drinking water along with 0.1 mg/ml of NDEA for 21 days effectively suppressed NDEA-induced toxicity and also resulted in a dose-dependent reduction in the levels of blood serum enzyme markers (AST, ALT, ALP, and LDH). Moreover, LPO, PCC, and GST activity were reduced and the GSH level was increased upon the administration of curcumin along with NDEA. The results obtained for the comet assay in rat hepatocytes and blood lymphocytes showed a significant dose-dependent decrease in the mean tail length. The micronucleus assay performed on rat hepatocytes also showed a dose-dependent reduction in the frequency of micronucleated cells along with curcumin administration. These results suggest that curcumin has a protective role against NDEA-induced toxicity in albino rats.  相似文献   
9.
Purpose: To describe how central venous access devices (CVADs) are utilized for ambulatory oncology patients and to evaluate the rate of complications. Method: Single institution retrospective study of oncology patients with CVADs who received systemic treatment at the Walker Family Cancer Centre (WFCC) between 1 January and 31 December 2018. Results: A total of 480 CVADS were placed in 305 patients, of which 408 (85%) were peripherally inserted central catheters (PICCs) and 72 (15%) were implanted vascular access devices (PORTs). The incidence of early and late complications was 9% and 24%, respectively. For the entire cohort, the rate of venous thromboembolism (VTE) was 16%, of which 9% were CVAD-related thrombosis (CRTs) and 7% were distant VTE. The CRT rates were similar for PICCs and PORTs (9% vs. 7%). A total of 6% of CVADs were complicated by infection (i.e., localized infections and bacteremia), with a total infection rate of 0.43 and 0.26 per 1000 indwelling days for PICCs and PORTs, respectively. The incidence of central line associated bloodstream infections (CLABSI) was greater for PICCs than PORTs, at a rate of 0.22 compared with 0.08 per 1000 indwelling days, respectively. The premature catheter removal rate was 26% for PICCs and 18% for PORTs. PORTs required more additional hospital visits. Conclusions: PICCs were utilized more frequently than PORTs and had a higher rate of premature removal. The rates of VTE and CRT were similar for both CVAD types. PORTs had a lower rate of infection per 1000 indwelling days. However, the management of PORT related complications required more visits to the hospital and oncology clinic.  相似文献   
10.
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