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   1093篇
  免费   36篇
  国内免费   15篇
耳鼻咽喉   24篇
儿科学   37篇
妇产科学   64篇
基础医学   75篇
口腔科学   23篇
临床医学   91篇
内科学   249篇
皮肤病学   10篇
神经病学   49篇
特种医学   20篇
外科学   349篇
综合类   9篇
预防医学   10篇
眼科学   36篇
药学   51篇
中国医学   3篇
肿瘤学   44篇
  2023年   7篇
  2022年   10篇
  2021年   27篇
  2020年   15篇
  2019年   19篇
  2018年   35篇
  2017年   16篇
  2016年   56篇
  2015年   32篇
  2014年   55篇
  2013年   59篇
  2012年   116篇
  2011年   96篇
  2010年   67篇
  2009年   50篇
  2008年   78篇
  2007年   97篇
  2006年   82篇
  2005年   72篇
  2004年   55篇
  2003年   49篇
  2002年   30篇
  2001年   5篇
  2000年   1篇
  1999年   1篇
  1998年   9篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1985年   1篇
排序方式: 共有1144条查询结果,搜索用时 15 毫秒
51.
Recording the motor output of the central nervous system from the cervical spinal cord was investigated as a method of generating voluntary command signals, potentially to be used in quadriplegic individuals. Corticospinal volleys evoked by motor cortex stimulation were recorded from the spinal cord surface with multicontact electrodes in anesthetized cats. The multicontact recordings were analyzed for their information-carrying capacity as a neural interface. Neural signals resulting from the stimulation of various points in the motor cortex were considered as symbols of an alphabet that were sent through a discrete information channel. The information capacity of this channel at the thermal noise level of the electrode contacts was calculated. The maximum information rate was 1.57 bits in a trial for a 4-symbol alphabet. The background noise that reduces the information rate to 50% of its maximum theoretical value was defined as the half-bitrate-noise-tolerance (HBR-NoiseTol) and used as a measure of symbol distinguishability. The HBR-NoiseTol for all trials on average was 24 +/- 12%, 18 +/- 10%, and 15 +/- 9% for interfaces with 2-, 3-, and 4-symbol alphabets (n = 11 trials). The average peak-to-peak amplitude of the neural volleys was 13.5 +/- 6.7 microV (n = 11). These results suggest that the corticospinal signals can be recorded with spatial selectivity from the spinal cord surface and thus warrant further investigation of their potential use for a spinal cord-computer interface.  相似文献   
52.
BACKGROUND: The purpose of this study was to determine the rate of spontaneous gestational sac loss during the first trimester in women achieving multiple pregnancies by ICSI. METHODS: A retrospective analysis was performed of 1448 consecutive multiple pregnancies conceived by ICSI. RESULTS: Of the cohort of 1448 pregnancies, twin gestations constituted 59.6% (864), triplets 30.2% (438) and quadruplets 10.0% (146). During the first trimester, 69 (4.7%) patients miscarried, while 179 (12.3%) continued their pregnancies and had fewer gestational sacs at the end of the first trimester than at the beginning. The overall loss rate of any gestational sac during the first trimester in these multiple pregnancies was 10.1%. There was a significant difference in the frequency of spontaneous reduction to twin or singleton pregnancies in the first trimester between women carrying triplets (11.7%) and those carrying quadruplets (3.5%) [P = 0.004; odds ratio (OR) 3.5; 95% confidence interval (CI) 1.3-9.1]. The frequency of gestational sac loss was significantly greater among women >35 years old (20.9%) than in women less than 35 years old (15.9%) (P = 0.03; OR 1.4; 95% CI 1.0-1.9). CONCLUSION: In multiple pregnancies there is a significant risk of spontaneous loss of any embryo during the first trimester. These findings should be considered prior to any decision about selective embryo reduction.  相似文献   
53.
54.
Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease with unknown etiology and pathogenesis. With high mortality risks, most of the IPF cases emerged after a damage of alveolar epithelium, where this situation stimulates the over expression of matrix components. Inflammatory process observed as a reaction to emerged damage. Prolidase as an iminodipeptidase significantly increased during the development of fibrosis. The aim of this study is to measure prolidase activity as a marker of treatment and diagnosis in an experimental lung fibrosis animal model. Thirty male Wistar rats randomly divided into three experimental groups, with ten rats in each group. Group 1, control group; group 2, bleomycin (BLM)-induced lung fibrosis group, and group 3, BLM-induced lung fibrosis treated with palosuran (urotensin-II receptor antagonist). For histopathology, the middle lobes of right lungs were embedded in paraffin, followed by fixation in 10?% buffered formalin, and evaluation of IPF was performed using the Ashcroft scoring method. Prolidase activity was determined by a photometric method based on the measurement of proline levels produced by prolidase. The fibrosis scores and the prolidase activity were significantly enhanced by BLM stimulation. The BLM + palosuran treatment decreased prolidase activity in group 3. There was a positive correlation between prolidase activity and fibrosis scores. Palosuran seems to be effective in the treatment of lung fibrosis, and prolidase activity can be used for the diagnosis and/or for management of the treatment. However, further clinical and experimental studies with animals and/or patients are needed to verify these conclusions.  相似文献   
55.
Objectives: Genetic variants in Toll-like receptors (TLRs) are considered a potential indicator for host susceptibility to and outcome of several infectious diseases including tuberculosis. The aim of this study was to determine whether −129 C/G and Met1Val polymorphisms of TLR8 were associated with pediatric pulmonary tuberculosis in Turkish population. Methods: The −129 C/G and Met1Val polymorphisms were studied in 124 children with pulmonary tuberculosis compared to 150 age-matched healthy control subjects. Results: We did not identify any statistically significant differences between the patients with TB and control groups with regard to the frequency of genotypes GG or G/(−), CG, and CC or C/(−); and alleles G and C at rs3764879 (p > 0.05). We found a strong association with genotype A/(−) at rs3764880 with susceptibility to pulmonary TB in males (OR 2.87, 95%CI 1.38–5.98, p = 0.007). Conclusions: Our results provide evidence, for the first time, of a role for the TLR8 gene in susceptibility to pulmonary TB in male children. Additional research to verify our results are necessary. Tuberculosis in children presents particularly difficult challenges, but research priorities and advances in pediatric tuberculosis could provide wider insights and opportunities for tuberculosis control.  相似文献   
56.
Research questionAngiotensin-converting enzyme inhibition results in a significant reduction in plasma concentrations of plasminogen activator inhibitor-1 (PAI-1). What are the effects of lisinopril treatment on PAI-1 concentrations and the morphology and function of the ovaries in the letrozole-induced polycystic ovary syndrome (PCOS) rat model?DesignThis prospective randomized controlled animal study involved female Wistar albino rats. Twelve rats were assigned as controls (group I). In the study group (n = 48), letrozole (an aromatase inhibitor) was administered for PCOS modelling for 9 weeks. After confirming disrupted oestrous cycles, the study group was randomized into two groups: group II (n = 24; letrozole only) and group III (n = 24; letrozole + lisinopril 15 mg/kg per day). After 12 weeks, each group was divided randomly into two. Biochemical, histopathological and immunohistochemical analyses was performed in subgroups designated A, and fertilization rates were studied in subgroups designated B.ResultsLisinopril treatment reduced the weight and area of the ovaries, the number and wall thickness of cystic follicles, and serum concentrations of LH and testosterone, relative to group II (P < 0.001). Circulating PAI-1 concentrations were significantly different among three groups (7.7 ± 0.9 ng/ml, 9.8 ± 0.7 ng/ml and 8.6 ± 0.7 ng/ml for groups IA, IIA and IIIA; P < 0.001). Pregnancy rates were 100%, 0% and 16.7% in groups IB, IIB and IIIB.ConclusionsIn the letrozole-induced rodent PCOS model, lisinopril modifies the action of letrozole, possibly by inhibition of systemic and ovarian production of PAI-1. The use of PAI-1 inhibitors deserves further investigation in understanding the pathogenesis of PCOS.  相似文献   
57.
Introduction. Gastric cancer is the second cause of cancer-related deaths worldwide. Delayed diagnosis leads to high mortality rates. Eotaxin-1 was originally discovered as an eosinophil-selective chemoattractant and may play a role in a number of chronic inflammatory diseases, cancer, and other gastrointestinal disorders. The aim of this study was to analyse diagnostic and prognostic significance of serum eotaxin-1 (s-eotaxin-1) levels in gastric cancer. Methods. Sixty gastric cancer patients and 69 healthy subjects were included into the study. S-eotaxin-1 levels were compared with clinicopathological features and outcomes in gastric cancer. Results. Serum levels of eotaxin-1 in gastric cancer patients were significantly higher than controls (74.51 ± 16.65 pg/mL versus 16.79 ± 5.52 pg/mL, respectively (P < 0.001)). The s-eotaxin-1 levels did not differ significantly with histopathological grade, tumor-node-metastasis (TNM) stage, tumor localization, lymph node metastases, positive lymph node ratio, size, perineural and perivascular invasion. So there is no relationship found between s-eotaxin-1 level and prognosis. Conclusion. S-eotaxin-1 levels may be used as an easily available biomarker for gastric cancer risk and may alert physicians for early diagnosis. Due to the limited number of patients included in this study, larger cohort studies are warranted to validate the diagnostic value of s-eotaxin-1 level in gastric cancer.  相似文献   
58.
Pulmonary arterial hypertension (PAH) is a progressive and a life-threatening disease with its high morbidity and mortality ratios. On searching for new shining targets in pathogenesis, we noticed, in our previous studies, urotensin-II (UII) in systemic sclerosis with potent angiogenic and pro-fibrotic features. Owing to the mimicking properties of UII with endothelin-1 (ET1), we attempted to investigate the effect of palosuran in a PAH rat model. Thirty rats were randomly divided into three groups, with each group comprising 10 rats: group 1 (control group) received the vehicle subcutaneously, instead of monocrotaline (MCT) and vehicle; group 2 (MCT group) received subcutaneous MCT and vehicle; and group 3 (MCT + palosuran group) received subcutaneous MCT and palosuran. Serum UII, ET1, transforming growth factor-β1 (TGF-β1) levels, pulmonary arteriolar pathology of different diameter vessels, and cardiac indices were evaluated. The ET1, TGF-β1, and UII levels were significantly diminished in the treatment group, similar to the controls (p?<?0.001). Right ventricular hypertrophy index and mean pulmonary arterial pressure scores were also significantly reduced in the treatment group (p?=?0.001). Finally, in the 50–125-μm diameter arterioles, in contrast to Groups 3 and 1, there was a statistically significant thickness (p?<?0.01) in the arteriolar walls of rats in Group 2. The treatment effect on arteries of more than 125-μm diameters was found to be valuable but not significant. Owing to its healing effect on hemodynamic, histological, and biochemical parameters of MCT-induced PAH, palosuran as an antagonist of UII might be an optional treatment alternative for PAH.  相似文献   
59.
Systemic sclerosis (SSc) is a disease characterized by skin and internal organ involvement. There is progressive accumulation of extracellular matrix components in the skin and involved organs. Tissue fibrosis is the prominent reason for mortality, and still, there is no satisfactory treatment. The aim of this study was to evaluate the effects of urotensin-II (U-II) antagonist palosuran in an animal model of scleroderma. We also planned to measure U-II, endothelin-1 (ET-1), and transforming growth factor-β1 (TGF-β1) levels, as well as the association of these levels with dermal thickness. Twenty-four male mice were included in this study and they were divided into three groups—group 1: control group, group 2: fibrosis group, and group 3: fibrosis + palosuran treatment group. Fibrosis + palosuran treatment in group 3 reduced ET-1, U-II, and TGF-β1 levels. In total, the diminished values were statistically significant in the ET-1 and TGF-β1 levels (p?<?0.05). Dermal thickness was higher in the fibrosis group, when compared with the other groups. There was no significant relationship between dermal thickness and ET-1, U-II, or TGF-β1 levels (p?>?0.05). It is believed that U-II is an important mediator in SSc, and its antagonism with palosuran could be a new treatment choice in SSc.  相似文献   
60.
BackgroundIt is extremely difficult to treat spine disorders with stabilization in patients with rheumatoid arthritis. Because revision rates are significantly higher in rigid stabilization. To date, there is no data about patients with rheumatoid arthritis treated with dynamic stabilization. Our aim was to compare the radiological and clinical results of patients with rheumatoid arthritis who underwent lumbar rigid stabilization or dynamic stabilization with Polyetheretherketone rod (PEEK).MethodsPatients with degenerative lumbar spine disease with rheumatoid arthritis who underwent dynamic stabilization between 2013 and 2015 and rigid stabilization between 2010 and 2012 were evaluated radiologically for adjacent segment disease, proximal junctional kyphosis, system problem (nonunion, screw loosening, instrumentation failure, pull out). It was also compared according to both the revision rates and the Visual Analog Scale and Oswestry Disability Index scores at the 12th month and 24th month.ResultsThe difference of decrease in Visual Analog Scale and Oswestry Disability Index scores from preoperative to 12th month between patients who underwent dynamic stabilization and rigid stabilization was statistically insignificant. However, there was a significant difference of increase in Visual Analog Scale and Oswestry Disability Index scores between the 12th month and 24th month of patients who underwent rigid stabilization, compared with patients with dynamic stabilization. In patients with dynamic stabilization, the problems of instrumentation were seen less frequently. Revision rates were high in patients with rigid stabilization when compared the patients with dynamic stabilization.ConclusionRadiological and clinical outcomes in patients with rheumatoid arthritis operated with dynamic stabilization are more significant when compared to rigid stabilization. These patients have lower pain and disability scores in their follow up periods. Revision rates are lower in patients with dynamic stabilization.  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