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   276篇
  免费   17篇
  国内免费   2篇
儿科学   8篇
妇产科学   4篇
基础医学   30篇
口腔科学   6篇
临床医学   42篇
内科学   62篇
皮肤病学   10篇
神经病学   4篇
特种医学   7篇
外科学   24篇
综合类   7篇
预防医学   37篇
眼科学   1篇
药学   28篇
肿瘤学   25篇
  2022年   2篇
  2021年   10篇
  2020年   6篇
  2019年   10篇
  2018年   17篇
  2017年   7篇
  2016年   6篇
  2015年   8篇
  2014年   13篇
  2013年   13篇
  2012年   21篇
  2011年   21篇
  2010年   17篇
  2009年   8篇
  2008年   16篇
  2007年   25篇
  2006年   14篇
  2005年   17篇
  2004年   15篇
  2003年   2篇
  2002年   9篇
  2001年   3篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1995年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   2篇
  1988年   1篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1981年   3篇
  1979年   2篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1972年   1篇
排序方式: 共有295条查询结果,搜索用时 687 毫秒
181.
The impact of indoor air pollution (IAP) from biomass fuel burning on the risk of carcinogenesis in the airways has been investigated in 187 pre-menopausal women (median age 34 years) from eastern India who cooked exclusively with biomass and 155 age-matched control women from same locality who cooked with cleaner fuel liquefied petroleum gas. Compared with control, Papanicolau-stained sputum samples showed 3-times higher prevalence of metaplasia and 7-times higher prevalence of dysplasia in airway epithelial cell (AEC) of biomass users. Immunocytochemistry showed up-regulation of phosphorylated Akt (p-Aktser473 and p-Aktthr308) proteins in AEC of biomass users, especially in metaplastic and dysplastic cells. Compared with LPG users, biomass-using women showed marked rise in reactive oxygen species (ROS) generation and depletion of antioxidant enzyme, superoxide dismutase (SOD) indicating oxidative stress. There were 2-5 times more particulate pollutants (PM10 and PM2.5), 72% more nitrogen dioxide and 4-times more particulate-laden benzo(a)pyrene, but no change in sulfur dioxide in indoor air of biomass-using households, and high performance liquid chromatography estimated 6-fold rise in the concentration of benzene metabolite trans,trans-muconic acid (t,t-MA) in urine of biomass users. Metaplasia and dysplasia, p-Akt expression and ROS generation were positively associated with PM and t,t-MA levels. It appears that cumulative exposure to biomass smoke increases the risk of lung carcinogenesis via oxidative stress-mediated activation of Akt signal transduction pathway.  相似文献   
182.
Because differentiation of mesenchymal stem cells (MSCs) is enacted through the integration of soluble signaling factors and physical cues, including substrate architecture and exogenous mechanical stimulation, it is important to understand how micropatterned biomaterials may be optimized to enhance differentiation for the formation of functional soft tissues. In this work, macroscopic strain applied to MSCs in an aligned nanofibrous microenvironment elicited cellular and nuclear deformations that varied depending on scaffold orientation. Reorientation of aligned, oriented MSCs corresponded at the microscopic scale with the affine approximation of their deformation based on macroscopic strains. Moreover, deformations at the subcellular scale corresponded with scaffold orientation, with changes in nuclear shape depending on the direction of substrate alignment. Notably, these deformations induced changes in gene expression that were also dependent on scaffold and cell orientations. These findings demonstrate that directional biases in substrate microstructure convey direction-dependent mechanosensitivity to MSCs and provide an experimental framework in which to explore the mechanistic underpinnings of this response.  相似文献   
183.
Understanding the interplay of composition, organization and mechanical function in load-bearing tissues is a prerequisite in the successful engineering of tissues to replace diseased ones. Mesenchymal stem cells (MSCs) seeded on electrospun scaffolds have been successfully used to generate organized tissues that mimic fibrocartilages such as the knee meniscus and the annulus fibrosus of the intervertebral disc. While matrix deposition has been observed in parallel with improved mechanical properties, how composition, organization, and mechanical function are related is not known. Moreover, how this relationship compares to that of native fibrocartilage is unclear. Therefore, in the present work, functional fibrocartilage constructs were formed from MSC-seeded nanofibrous scaffolds, and the roles of collagen and glycosaminoglycan (GAG) in compressive and tensile properties were determined. MSCs deposited abundant collagen and GAG over 120 days of culture, and these extracellular molecules were organized in such a way that they performed similar mechanical functions to their native roles: collagen dominated the tensile response while GAG was important for compressive properties. GAG removal resulted in significant stiffening in tension. A similar stiffening response was observed when GAG was removed from native inner annulus fibrosus, suggesting an interaction between collagen fibers and their surrounding extrafibrillar matrix that is shared by both engineered and native fibrocartilages. These findings strongly support the use of electrospun scaffolds and MSCs for fibrocartilage tissue engineering, and provide insight on the structure-function relations of both engineered and native biomaterials.  相似文献   
184.
Though the incidence of hypertension has increased considerably in recent years, the pathophysiologic mechanism that causes progression from stage of prehypertension to hypertension has not been fully elucidated. Therefore, the present study was conducted to assess the sympathovagal imbalance in prehypertensives and hypertensives by spectral analysis of heart rate variability (HRV) to understand the nature of change in autonomic balance in this common dysfunction of mankind. Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), and spectral indices of HRV such as total power (TP), normalized low frequency power (LFnu), normalized high frequency power (HFnu), ratio of low frequency power to high frequency power (LF-HF ratio), mean heart rate (mean RR), square root of the mean squared differences of successive normal to normal intervals (RMSSD), the number of interval differences of successive NN intervals greater than 50 ms (NN50), and the proportion derived by dividing NN50 by the total number of NN intervals (pNN50) were assessed in three groups of subjects: normotensives (n = 32), prehypertensives (n = 28), and hypertensives (n = 31). Sympathovagal balance was analyzed and correlated with BMI, BHR, and BP in all the groups. It was observed that autonomic imbalance in prehypertensives was due to proportionate increased sympathetic activity and vagal inhibition, whereas in hypertensives, vagal withdrawal was more prominent than sympathetic overactivity. The LF-HF ratio, the sensitive indicator of sympathovagal balance, was significantly correlated with BMI, BHR, and BP. It was concluded that vagal inhibition plays an important role in the critical alteration of sympathovagal balance in the development of clinical hypertension in prehypertensive subjects.  相似文献   
185.

Background/Aim:

Current guidelines recommend screening cirrhotic patients with an endoscopy to detect esophageal varices and to institute prophylactic measures in patients with large esophageal varices. In this study, we aimed at identifying non-endoscopic parameters that could predict the presence and grades of esophageal varices.

Patients and Methods:

In a prospective study, 229 newly diagnosed patients with liver cirrhosis, without a history of variceal bleeding, were included. Demographic, clinical, biochemical and ultrasonographic parameters were recorded. Esophageal varices were classified as small and large, at endoscopy. Univariate analysis and multivariate logistic regression analysis were done to identify independent predictors for the presence and grades of varices.

Results:

Of the 229 patients (141 males; median age 42 years; range 17-73 years) with liver cirrhosis, 97 (42.3%) had small and 81 (35.4%) had large varices. On multivariate analysis, low platelet count (Odd’s Ratio [OR], 4.3; 95% confidence interval [CI], 1.2-14.9), Child Pugh class B/C (OR, 3.3; 95% CI, 1.8-6.3), spleen diameter (OR, 4.3; 95% CI, 1.6-11.9) and portal vein diameter (OR, 2.4; 95% CI, 1.1-5.3) were independent predictors for the presence of varices. Likewise, for the presence of large esophageal varices, low platelet count (OR, 2.7; 95% CI, 1.4-5.2), Child Pugh class B/C (OR, 3.8; 95% CI, 2.3-6.5) and spleen diameter (OR, 3.1; 95% CI, 1.6-6.0) were the independent risk factors.

Conclusion:

The presence and higher grades of varices can be predicted by a low platelet count, Child-Pugh class B/C and spleen diameter. These may be considered as non-endoscopic predictors for the diagnosis and management of large grade varices.  相似文献   
186.
Over 70 years have passed since dermatologists John H. Stokes and Donald M. Pillsbury first proposed a gastrointestinal mechanism for the overlap between depression, anxiety and skin conditions such as acne. Stokes and Pillsbury hypothesized that emotional states might alter the normal intestinal microflora, increase intestinal permeability and contribute to systemic inflammation. Among the remedies advocated by Stokes and Pillsbury were Lactobacillus acidophilus cultures. Many aspects of this gut-brain-skin unifying theory have recently been validated. The ability of the gut microbiota and oral probiotics to influence systemic inflammation, oxidative stress, glycemic control, tissue lipid content and even mood itself, may have important implications in acne. The intestinal microflora may also provide a twist to the developing diet and acne research. Here we provide a historical perspective to the contemporary investigations and clinical implications of the gut-brain-skin connection in acne.  相似文献   
187.

Background

The study was conducted to test the potential of using dienogest (DNG) plus testosterone undecanoate (TU) in rats for development of a once-a-month injectable male hormonal contraceptive.

Study Design

Dose selection studies were initiated with administration of DNG in three different doses of 20, 30 and 40 mg/kg body weight (bw) per week plus TU 25 mg/kg bw once in every 6 weeks. Status of spermatogenesis and sperm count in epididymis was evaluated. The frequency of DNG intervention was later extended to every 2- and 4-week intervals. Mating studies, toxicity and reversibility of spermatogenesis following stoppage of treatment were carried out with DNG 40 mg/kg bw at 4-week intervals.

Results

Complete arrest of spermatogenesis was observed after 60 days of treatment at all doses of DNG (20, 30 and 40 mg/kg bw per week)+TU. However, weights of testis and accessory sex organs (epididymis, prostate and seminal vesicle) declined significantly 60 days post treatment compared to vehicle-treated controls. Epididymis in the treated animals was completely devoid of sperm. When the frequency of DNG injection (20 mg/kg bw) was extended to once every 15 days, a few immotile and decapitated sperm were observed in the epididymis. With TU treatment unchanged, animals receiving DNG (40 mg/kg bw) once either every 2- or 4-week intervals demonstrated good and uniform arrest of spermatogenesis. DNG 40 mg/kg per 4 weeks+TU also demonstrated a significant rise in germ cell apoptosis in the seminiferous epithelium. There was no significant increase in the serum high-density lipoprotein and low-density lipoprotein levels at the end of 120 days of treatment. Following withdrawal of treatment after 60 or 120 days, qualitative restoration of spermatogenesis was rapid in the former compared to the latter.

Conclusion

Dienogest plus TU has the potential for development as a monthly injectable showing reversible hormonal male contraception with good efficacy.  相似文献   
188.
The occurrence of seizures in the sleep state is observed in nearly one third of patients. This is caused by an intimate relationship between the physiological state of sleep and the pathological process underlying epileptic seizures. Both sleep and sleep deprivation influence the frequency of epileptiform discharges on electroencephalograms as well as the occurrence of clinical seizures, typically during nonrapid eye movement sleep. The relationship of epileptiform activity to nonrapid eye movement sleep is vividly shown in the syndrome of continuous spikes in slow-wave sleep and the Landau-Kleffner syndrome. Seizure semiology can also be influenced by sleep and sleep deprivation. Sleep disorders may influence seizure control, and effective treatment of sleep disorders can improve seizure control. Seizures, antiepileptic drugs, ketogenic diet, and vagus nerve stimulation all influence sleep quality, daytime alertness, and neurocognitive function.  相似文献   
189.
190.
Because of high specificity and easy detection in the tissues, serum, plasma, urine and saliva, interest in exploring the potential of long non‐coding RNAs (lncRNAs) in cancer patients continues to increase. LncRNAs have shown potential as a biomarker in the diagnosis and prognosis of bladder cancer, prostate cancer, gastric cancer, pancreatic cancer, breast cancer and many other cancer types. Some lncRNAs have also been used as adjunct to improve the specificity and sensitivity of existing biomarkers. The molecular tools such as RNA‐seq, RNA‐FISH, ic‐SHAPE and quantitative real‐time PCR have been used for examining the lncRNAs' potential. Some lncRNAs such as PCA3 is now routinely used in the clinic for the diagnosis of prostate cancer. Single nucleotide polymorphisms (SNPs) in lncRNAs can also be used as a predictor of cancer risk. Although ongoing studies continue to unravel the underlying mechanism, some lncRNAs have been used as therapeutic targets for the selective killing of cancer cells in patients. Thus lncRNAs are emerging as convenient and minimally invasive diagnostic/prognostic markers, and also as therapeutic target. Companies such as the Curna Inc., MiNA Therapeutics Ltd. and RaNA Therapeutics Inc. have been taking steps to develop lncRNA based strategies against cancer. In this review, we discuss the potential of lncRNAs as biomarkers and therapeutic targets in cancer patients.  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