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   2934篇
  免费   238篇
  国内免费   311篇
  3483篇
  2024年   7篇
  2023年   57篇
  2022年   127篇
  2021年   170篇
  2020年   126篇
  2019年   131篇
  2018年   166篇
  2017年   97篇
  2016年   135篇
  2015年   194篇
  2014年   220篇
  2013年   218篇
  2012年   264篇
  2011年   251篇
  2010年   162篇
  2009年   127篇
  2008年   165篇
  2007年   156篇
  2006年   124篇
  2005年   85篇
  2004年   87篇
  2003年   50篇
  2002年   73篇
  2001年   45篇
  2000年   31篇
  1999年   41篇
  1998年   32篇
  1997年   30篇
  1996年   17篇
  1995年   15篇
  1994年   13篇
  1993年   12篇
  1992年   17篇
  1991年   5篇
  1990年   5篇
  1989年   6篇
  1988年   7篇
  1987年   4篇
  1986年   1篇
  1985年   4篇
  1984年   2篇
  1983年   3篇
  1980年   1篇
排序方式: 共有3483条查询结果,搜索用时 12 毫秒
991.

Purpose

Nucleolar spindle-associated protein (NuSAP1) is an important mitosis-related protein, and aberrant NuSAP1 expression is associated with abnormal spindles and mitosis. This study investigated the prognostic value of NuSAP1 in breast cancer.

Methods

Two sets of tissue microarrays (TMAs) that included samples from 450 breast cancer patients were constructed, of which 250 patients were training set and the other 200 patients were validation set. Immunohistochemical staining was performed to determine the NuSAP1 levels. A Kaplan-Meier analysis was used to estimate the prognostic value of NuSAP1 in breast cancer. A stepwise Cox analysis was performed to construct a risk-prediction model for triple-negative breast cancer (TNBC). All statistical analysis was performed with SPSS software.

Results

There were 108 (43.5%) and 88 (44.0%) patients expressed NuSAP1 in the training set and validation set respectively. High levels of NuSAP1 expression were related to poor disease-free survival (DFS) in both training (P = 0.028) and validation (P = 0.006) cohorts, particularly in TNBC. With combination of two cohorts, both NuSAP1 (HR = 4.136, 95% CI: 1.956–8.747, P < 0.001) and BRCA1 (HR = 0.383, 95% CI: 0.160–0.915, P = 0.031) were independent prognostic indicators of DFS in TNBC. A receiver operating characteristic (ROC) analysis revealed that the combination of NuSAP1 and BRCA1 significantly improved the prognostic power compared with the traditional model (0.778 versus 0.612, P < 0.001).

Conclusions

Our study confirms the prognostic value of NuSAP1 in breast cancer. The combination of NuSAP1 and BRCA1 could improve the DFS prediction accuracy in TNBC.  相似文献   
992.

Objective

To examine the trends in the prevalence of overweight and obesity among preschool children from 2006 to 2014.

Methods

A total of 145,078 children aged 3–6 years from 46 kindergartens finished the annual health examination in Tianjin, China. Height, weight and other information were obtained using standardized methods. Z-scores for weight, height, and BMI were calculated based on the standards for the World Health Organization (WHO) child growth standards.

Results

From 2006 to 2014, mean values of height z-scores significantly increased from 0.34 to 0.54, mean values of weight z-scores kept constant, and mean values of BMI z-scores significantly decreased from 0.40 to 0.23. Mean values of height z-scores, weight z-scores, and BMI z-scores slightly decreased among children from 3 to 4 years old, and then increased among children from 4 to 6 years old. Between 2006 and 2014, there were no significant changes in prevalence of overweight (BMI z-scores >2 SD) and obesity (BMI z-scores >3 SD) among 3–4 years children. However, prevalence of obesity (BMI z-scores >2 SD) increased from 8.8% in 2006 to 10.1% in 2010, and then kept stable until 2014 among 5–6 years children. Boys had higher prevalence of obesity than girls.

Conclusions

Mean values of BMI z-scores decreased from 2006 to 2014 among Chinese children aged 3–6 years old due to the significant increase of height z-scores. Prevalence of obesity increased from 2006 to 2010, and then kept stable until 2014 among children aged 5–6 years. The prevalence of obesity was higher in boys than in girls.  相似文献   
993.
The formation and development of maize kernel is a complex dynamic physiological and biochemical process that involves the temporal and spatial expression of many proteins and the regulation of metabolic pathways. In this study, the protein profiles of the endosperm and pericarp at three important developmental stages were analyzed by isobaric tags for relative and absolute quantification (iTRAQ) labeling coupled with LC-MS/MS in popcorn inbred N04. Comparative quantitative proteomic analyses among developmental stages and between tissues were performed, and the protein networks were integrated. A total of 6,876 proteins were identified, of which 1,396 were nonredundant. Specific proteins and different expression patterns were observed across developmental stages and tissues. The functional annotation of the identified proteins revealed the importance of metabolic and cellular processes, and binding and catalytic activities for the development of the tissues. The whole, endosperm-specific and pericarp-specific protein networks integrated 125, 9 and 77 proteins, respectively, which were involved in 54 KEGG pathways and reflected their complex metabolic interactions. Confirmation for the iTRAQ endosperm proteins by two-dimensional gel electrophoresis showed that 44.44% proteins were commonly found. However, the concordance between mRNA level and the protein abundance varied across different proteins, stages, tissues and inbred lines, according to the gene cloning and expression analyses of four relevant proteins with important functions and different expression levels. But the result by western blot showed their same expression tendency for the four proteins as by iTRAQ. These results could provide new insights into the developmental mechanisms of endosperm and pericarp, and grain formation in maize.  相似文献   
994.

Purpose

Evaluation of peripheral retinal vascular changes in anterior uveitis using ultra-wide-field fluorescein angiography.

Design

A prospective, observational study of a case series of patients diagnosed with anterior uveitis.

Methods

Setting: Clinical observation at an academic medical center. Patient or Study Population: A total of 65 eyes of 33 patients corresponded with the research criteria of anterior uveitis in the opinion of specialists of Peking University First Hospital. Observation Procedures: Patients were diagnosed primarily through clinical examinations and conventional fluorescein angiography. Subsequently, ultra-wide-field fluorescein angiograms were obtained for each patient. Main Outcome Measures: The main outcome was the detection of peripheral retinal changes by ultra-wide-field fluorescein angiography, and how these changes influenced the evaluation and management of the disease.

Results

Peripheral vessel leakage was detected in 27 eyes (42%) with anterior uveitis, of which 15 eyes displayed active inflammation and 12 eyes displayed inactive inflammation. Peripheral vessel leakage was found in seven of eight eyes with cystoid macular edema. Cystoid macular edema was detected in 7 of 27 eyes (26%) with peripheral vessel leakage, whereas 1 of 38 eyes (3%) did not display peripheral vessel leakage (p<0.01). 44.4% of the patients with peripheral vessel leakage had a specific etiology. The relevant treatment strategies were modified based on the results of the ultra-wide-field fluorescein angiography. 12 patients with peripheral vessel leakage and a quiescent anterior segment were added to those receiving topical glucocorticoids, while 3 patients with serious peripheral vessel leakage and an active anterior segment received a sub-Tenon injection of triamcinolone acetonide.

Conclusions

Ultra-wide-field fluorescein angiography was very effective in detecting peripheral retinal vascular pathology in anterior uveitis. The changes found in the periphery were important in the evaluation and management of anterior uveitis.  相似文献   
995.

Background

Restenosis after percutaneous coronary intervention (PCI) is a remained clinical problem which limits long-term success of PCI. Although there was recognition that probucol in treating restenosis after percutaneous transluminal coronary angioplasty, the efficacy of probucol on restenosis after stent-implantation is controversial. So this meta-analysis was conducted to investigate the association between probucol and late restenosis.

Methods

Articles were assessed by four trained investigators, with divergences resolved by consensus. PubMed, EMBASE, ScienceDirect and the Cochrane Central Register of clinical trials were searched for pertinent studies. Inclusion criteria were random allocated to treatment and a comparison of probucol-treated patients and control patients (not treated with lipid-lowering drug) undergoing PCI.

Results

Fifteen studies with 859 subjects were analyzed. Major outcome, binary angiographic restenosis defined as >50% stenosis upon follow-up angiography, was significantly decreased with probucol treatment (RR = 0.59 [0.43, 0.80] among vessels, P = 0.0007; and RR = 0.52 [0.40, 0.68] among patients, P<0.00001). Probucol also increased the minimal luminal diameter (SMD = 0.45 [0.30, 0.61], P<0.00001) and decreased late loss upon follow-up after 6 months (SMD = -0.41 [-0.60, -0.22], P<0.0001). Moreover, there was a significantly lower incidence of major adverse cardiac events (MACE) in the probucol group than control group (RR = 0.69 [0.51, 0.93], P = 0.01).

Conclusion

Probucol is more than a lipid-lowering drug. It is also effective in reducing the risk of restenosis and incidence of MACE after PCI.  相似文献   
996.

Research Background

Currently, multiple myeloma is the second most common hematological malignancy in the U.S., constituting 1% of all cancers. With conventional treatment, the median survival time is typically 3–4 years, although it can be extended to 5–7 years or longer with advanced treatments. Recent research indicated that an increase in osteoclast (OC) activity is often associated withmultiple myeloma (MM) and that a decrease inosteoblast (OB) activity contributesto the osteolytic lesions in MM. Normally, the populations of OCs and OBs are inequilibrium, and an imbalance in this statecontributes to the development of lesions.

Research procedures

A multi-scale agent-based multiple myeloma model was developed to simulate the proliferation, migration and death of OBs and OCs. Subsequently, this model was employed to investigate the efficacy of thethree most commonly used drugs for MM treatment under the following two premises: the reduction in the progression of MM and the re-establishment of the equilibrium between OCs and OBs.

Research purposes

The simulated results not only demonstrated the capacity of the model to choose optimal combinations of the drugs but also showed that the optimal use of the three drugs can restore the balance between OCs and OBs as well as kill MMs. Furthermore, the drug synergism analysis function of the model revealed that restoring the balance between OBs and OCs can significantly increase the efficacy of drugs against tumor cells.  相似文献   
997.

Purpose

The purpose of this study is to identify risk factors of physical violence in Chinese township hospitals.

Methods

A cross-sectional survey was used in a sample of 442 general practitioners and 398 general nurses from 90 township hospitals located in Heilongjiang province, China (response rate = 84.8%).

Results

A total of 106 of the 840 (12.6%) respondents reported being physically attacked in their workplace in the previous 12 months. Most perpetrators were the patients’ relatives (62.3%), followed by the patient (22.6%); 73.6% of perpetrators were aged between 20 and 40 years. Of the physical violence incidents, about 56.6% (n = 60) resulted in a physical injury, and 45.4% of respondents took two or three days of sick leave. Reporting workplace violence in hospitals to superiors or authorities was low (9.4%). Most respondents (62.8%) did not receive training on how to avoid workplace violence. Logistic regression analyses indicated that general nurses, aged 35 years or younger, and with a higher-level professional title were more likely to experience physical violence. Healthcare workers with direct physical contact (washing, turning, lifting) with patients had a higher risk of physical violence compared to other health care workers. Procedures for reporting workplace violence were a protective factor for physical violence; when in place, reporting after psychological violence (verbal abuse, bullying/mobbing, harassment, and threats) was more protective than waiting until an instance of physical violence (beating, kicking, slapping, stabbing, etc.).

Conclusions

Physical violence in Chinese township hospitals is an occupational hazard of rural public health concern. Policies, procedures, and intervention strategies should be undertaken to manage this issue.  相似文献   
998.
The cytotoxicity effects of E. adenophorum on cell cycle and apoptosis of renal cells in Saanen goat was evaluated by TUNEL, DAPI, AO/EB staining, DNA fragmentation assay, Caspase activity, Western-blot, qRT-PCR and flow cytometry analysis. 16 saanen goats randomly divided into four groups were fed on 0%, 40%, 60% and 80% E. adenophorum diets. The Results showed that E. adenophorum induced typical apoptotic features of renal cells. E. adenophorum significantly suppressed renal cells viability, caused cell cycle activity arrest and induced typical apoptotic features in a dose-dependent manner. However, the protein levels of Fas/FasL, Bid and caspase-8 did not appear significant changes in the process of E. adenophorum-induced apoptosis. Moreover, E. adenophorum administration slightly decreased Bcl-2 expression, promoted Bax translocation to mitochondria, triggered the release of Cyt c from mitochondria into cytosol and activated caspase-9, -3, and cleaved PARP. The mitochondrial p53 translocation was significantly activated, accompanied by a significant increase in the loss of ΔΨm, Cyt c release and caspase-9 activation. Above all, these data suggest that E. adenophorum induces renal cells apoptosis via the activation of mitochondria-mediated apoptosis pathway in renal cells. These findings may provide new insights to understand the mechanisms involved in E. adenophorum-caused cytotoxicity of renal cells.  相似文献   
999.
The present study focused on the action mechanism of S. pneumoniae (Sp) in inducing autophagy in human alveolar epithelial cells. Sp, a gram-positive extracellular bacterium, activates autophagy with considerably increased microtuble-associated protein light chain 3 (LC3) punctation in A549 cells. The accumulation of typical autophagosomes and conjugation of LC3 to phosphatidylethanolamine were observed in Sp-infected cells as an indication of autophagy. Using the pneumolysin (PLY) mutant, we successfully demonstrated that PLY is involved in initiating autophagy without affecting the expression levels of PI3K-III and Beclin1. PLY-mediated autophagy depends on the inhibition of the phosphoinositide 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway. Furthermore, Sp could also lead to the reactive oxygen species (ROS) hypergeneration in A549 cells. Taken together, Sp infection-induced autophagy is PLY-mediated through ROS hypergeneration and mTOR inhibition. PI3K-I and rapamycin (autophagy inducers) enhanced bacterial clearance, whereas wortmannin (autophagy inhibitor) and acetylcysteine (ROS inhibitor) reduced intracellular bacteria clearance. Thus, Sp-induced autophagy represents a host-protective mechanism, providing new insight into the pathogenesis of respiratory tract Sp infection.  相似文献   
1000.
The 15-kDa selenoprotein (Sep15) is a selenoprotein residing in the lumen of the endoplasmic reticulum (ER) and implicated in quality control of protein folding. Herein, we established an inducible RNAi cell line that targets Sep15 mRNA in Chang liver cells. RNAi-induced Sep15 deficiency led to inhibition of cell proliferation, whereas cell growth was resumed after removal of the knockdown inducer. Sep15-deficient cells were arrested at the G1 phase by upregulating p21 and p27, and these cells were also characterized by ER stress. In addition, Sep15 deficiency led to the relocation of focal adhesions to the periphery of the cell basement and to the decrease of the migratory and invasive ability. All these changes were reversible depending on Sep15 status. Rescuing the knockdown state by expressing a silent mutant Sep15 mRNA that is resistant to siRNA also reversed the phenotypic changes. Our results suggest that SEP15 plays important roles in the regulation of the G1 phase during the cell cycle as well as in cell motility in Chang liver cells, and that this selenoprotein offers a novel functional link between the cell cycle and cell motility.  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