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   6627篇
  免费   313篇
  国内免费   115篇
耳鼻咽喉   72篇
儿科学   95篇
妇产科学   137篇
基础医学   864篇
口腔科学   112篇
临床医学   576篇
内科学   1486篇
皮肤病学   107篇
神经病学   457篇
特种医学   529篇
外科学   879篇
综合类   33篇
预防医学   199篇
眼科学   64篇
药学   715篇
中国医学   92篇
肿瘤学   638篇
  2023年   44篇
  2022年   141篇
  2021年   217篇
  2020年   103篇
  2019年   148篇
  2018年   164篇
  2017年   141篇
  2016年   198篇
  2015年   260篇
  2014年   306篇
  2013年   362篇
  2012年   534篇
  2011年   521篇
  2010年   371篇
  2009年   262篇
  2008年   401篇
  2007年   386篇
  2006年   319篇
  2005年   296篇
  2004年   254篇
  2003年   210篇
  2002年   166篇
  2001年   142篇
  2000年   151篇
  1999年   125篇
  1998年   83篇
  1997年   69篇
  1996年   66篇
  1995年   49篇
  1994年   48篇
  1993年   32篇
  1992年   36篇
  1991年   38篇
  1990年   35篇
  1989年   47篇
  1988年   46篇
  1987年   36篇
  1986年   29篇
  1985年   30篇
  1984年   20篇
  1983年   18篇
  1982年   17篇
  1981年   19篇
  1980年   18篇
  1979年   10篇
  1978年   9篇
  1976年   12篇
  1975年   9篇
  1971年   7篇
  1969年   8篇
排序方式: 共有7055条查询结果,搜索用时 31 毫秒
991.
We previously reported that oroxylin A, a γ-aminobutyric acid A (GABAA) receptor antagonist, ameliorates drugs-induced memory impairments. We synthesized several oroxylin A derivatives in efforts to find a substance that has pro-cognitive effects as well as improves sensorimotor gating. The aim of the present study is to investigate the effect of a novel oroxylin A derivative, 5,7-dihydroxy-6-methoxy-2(4-phenoxyphenyl)-4H-chromene-4-one (DMPC), on pharmacological models of schizophrenia, which exhibit memory impairment and sensorimotor gating deficit. Memory impairment was induced by scopolamine, a muscarinic receptor antagonist, or MK-801, an N-methyl-d-aspartate receptor antagonist. Sensorimotor gating deficits were induced by MK-801 and measured by prepulse inhibition (PPI) of the acoustic startle response task. DMPC treatment (20 mg/kg) significantly attenuated scopolamine- or MK-801-induced memory impairment and it even enhanced cognitive performance of normal animals. Furthermore, DMPC significantly ameliorated MK-801-induced PPI deficits in the acoustic startle response task. In an in vitro study, DMPC (20 μM) inhibited intracellular Cl? influx induced by muscimol, a selective GABAA receptor agonist. These results suggest that DMPC would be a potential candidate for alleviating cognitive dysfunction and sensorimotor gating deficits in schizophrenia, and that its effects may be mediated, in part, via blockade of the GABAergic neurotransmitter system.  相似文献   
992.
993.
We have recently demonstrated that some anti-diabetic drugs such as biguanide and thizolidinediones administered centrally modulate the blood glucose level, suggesting that orally administered anti-diabetic drugs may modulate the blood glucose level by acting on central nervous system. The present study was designed to explore the possible action of another class of anti-diabetic drugs, glinidies, administered centrally on the blood glucose level in ICR mice. Mice were administered intracerebroventricularly (i.c.v.) or intrathecally (i.t.) with 5 to 30 µg of repaglinide or nateglinide in D-glucose-fed and streptozotocin (STZ)-treated models. We found that i.c.v. or i.t. injection with repaglinide dose-dependently attenuated the blood glucose level in D-glucose-fed model, whereas i.c.v. or i.t. injection with nateglinide showed no modulatory action on the blood glucose level in D-glucose-fed model. Furthermore, the effect of repaglinide administered i.c.v. or i.t. on the blood glucose level in STZ-treated model was studied. We found that repaglinide administered i.c.v. slightly enhanced the blood glucose level in STZ-treated model. On the other hand, i.t. injection with repaglinide attenuated the blood glucose level in STZ-treated model. The plasma insulin level was enhanced by repaglinide in D-glucose-fed model, but repaglinide did not affect the plasma insulin level in STZ-treated model. In addition, nateglinide did not alter the plasma insulin level in both D-glucose-fed and STZ-treated models. These results suggest that the anti-diabetic action of repaglinide appears to be, at least, mediated via the brain and the spinal cord as revealed in both D-glucose fed and STZ-treated models.  相似文献   
994.
This study examined the mechanism of action of a local anesthetic, lidocaine·HCl. Energy transfer between the surface fluorescent probe, 1-anilinonaphthalene-8-sulfonic acid, and the hydrophobic fluorescent probe, 1,3-di(1-pyrenyl) propane, was used to determine the effect of lidocaine·HCl on the thickness (D) of the synaptosomal plasma membrane vesicles (SPMV) isolated from the bovine cerebral cortex, and liposomes of the total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from the SPMV. The thickness (D) of the intact SPMV, SPMVTL and SPMVPL were 1.044±0.008, 0.914±0.005 and 0.890±0.003 (arbitrary units, n=5) at 37℃ (pH 7.4), respectively. Lidocaine·HCl decreased the thickness of the neuronal and model membrane lipid bilayers in a dose-dependent manner with a significant decrease in the thickness, even at 0.1 mM. The decreasing effect of lidocaine·HCl on the membrane thickness might be responsible for some, but not all of its anesthetic action.  相似文献   
995.

Purpose

Metabolic tumour volume (MTV) and total lesion glycolysis (TLG) from 18F-FDG PET/CT are emerging prognostic biomarkers in human solid cancers; yet few studies have investigated their clinical and prognostic significance in oral cavity squamous cell carcinoma (OSCC). The present retrospective study evaluated the utility of pretreatment MTV and TLG measured by 18F-FDG PET/CT to predict survival and occult metastasis (OM) in OSCC.

Methods

Of 162 patients with OSCC evaluated preoperatively by 18F-FDG PET/CT, 105 who underwent definitive surgery with or without adjuvant therapy were eligible. Maximum standardized uptake value (SUVmax), MTV and TLG were measured. For calculation of MTV, 3-D regions of interest were drawn and a SUV threshold of 2.5 was used for defining regions. Univariate and multivariate analyses identified clinicopathological and imaging variables associated with OM, disease-free survival (DFS) and overall survival (OS).

Results

The median (range) SUVmax, MTV and TLG were 7.3 (0.7–41.9), 4.5 ml (0.7–115.1 ml) and 18.3 g (2.4–224.1 g), respectively. Of 53 patients with clinically negative lymph nodes, OM was detected in 19 (36 %). By univariate and multivariate analyses, MTV (P?=?0.018) and TLG (P?=?0.011) were both independent predictive factors for OM, although they were not independent of each other. The 4-year DFS and OS rates were 53.0 % and 62.0 %, respectively. Univariate and multivariate analyses revealed that MTV (P?=?0.001) and TLG (P?=?0.006), with different cut-off levels, were both independent predictive factors for DFS, although they were not independent of each other, and MTV (P?=?0.001), TLG (P?=?0.002) and the involved resection margin (P?=?0.007) were independent predictive factors for OS.

Conclusion

Pretreatment MTV and TLG may be useful in stratifying the likelihood of survival and predicting OM in OSCC.  相似文献   
996.

Purpose

Breast cancer displays varying molecular and clinical features. The ability to form breast tumors has been shown by several studies with aldehyde dehydrogenase 1 (ALDH1) positive cells. The aim of this study is to investigate the association between ALDH1 expression and clinicopathologic characteristics of invasive ductal carcinoma.

Methods

We investigated breast cancer tissues for the prevalence of ALDH1+ tumor cells and their prognostic value. The present study included paraffin-embedded tissues of 70 patients with or without recurrences. We applied immunohistochemical staining for the detection of ALDH1+ cells. Analysis of the association of clinical outcomes and molecular subtype with marker status was conducted.

Results

ALDH1+ and ALDH1- tumors were more frequent in triple-negative breast cancers and in luminal A breast cancers, respectively (p<0.01). ALDH1 expression was found to exert significant impact on disease free survival (DFS) (ALDH1+ vs. ALDH1-, 53.1±6.7 months vs. 79.2±4.7 months; p=0.03) and overall survival (OS) (ALDH1+ vs. ALDH1-, 68.5±4.7 months vs. 95.3±1.1 months; p<0.01). In triple-negative breast cancer (TNBC) patients, DFS and OS showed no statistical differences according to ALDH1 expression (ALDH1+ vs. ALDH1-, 45.3±9.4 months vs. 81.3±7.4 months, p=0.52; 69.0±7.5 months vs. 91.3±6.3 months, p=0.67). However, non-TNBC patients showed significant OS difference between ALDH1+ and ALDH1- tumors (ALDH1+ vs. ALDH1-, 77.6±3.6 months vs. 98.0±1.0 months; p=0.04) with no statistical difference of DFS (ALDH1+ vs. ALDH1-, 60.5±8.0 months vs. 81.8±4.6 months; p=0.27).

Conclusion

Our findings suggest that the expression of ALDH1 in breast cancer may be associated with TNBC and poor clinical outcomes. On the basis of our findings, we propose that ALDH1 expression in breast cancer could be correlated with poor prognosis, and may contribute to a more aggressive cancer phenotype.  相似文献   
997.
PURPOSE: To estimate the incidence of occult metastases to the brain and skeleton in patients suspected of having non-small cell lung cancer (NSCLC) (stage higher than T1Nomo) with surgically resectable disease, to assess the accuracy of screening magnetic resonance (MR) imaging and radionuclide bone scanning for help in identifying occult metastases, and to determine the effectiveness of a high dose of MR contrast material. MATERIALS AND METHODS: Twenty-nine patients suspected of having NSCLC localized to the lung or to the lung and regional nodes underwent preoperative MR imaging with contrast material enhancement and radionuclide bone scanning for detection of brain or skeletal metastases. Patients were followed up for 12 months to determine the incidence of clinical metastatic disease. RESULTS: Eight (28%) patients had occult metastatic disease to the brain or skeleton. Brain metastases were identified on MR images in five of six patients. Bone metastases were identified on MR images in four of five patients and on bone scans in three of five patients. MR imaging was no more accurate than bone scanning for skeletal evaluation. A high dose of MR contrast material allowed detection of more metastases and of small lesions. CONCLUSION: Contrast-enhanced MR imaging of the brain is indicated for the exclusion of brain metastases in patients with clinically operable known or possible NSCLC and a large (> 3-cm) lung mass. Skeletal imaging may be indicated if an isolated brain metastasis is detected.  相似文献   
998.
999.

Objectives

This study was designed to assess changes in cardiopulmonary resuscitation (CPR) quality and rescuer fatigue when rescuers are provided with a break during continuous chest compression CPR (CCC-CPR).

Methods

The present prospective, randomized crossover study involved 63 emergency medical technician trainees. The subjects performed three different CCC-CPR methods on a manikin model. The first method was general CCC-CPR without a break (CCC), the second included a 10-s break after 200 chest compressions (10/200), and the third included a 10-s break after 100 chest compressions (10/100). All methods were performed for 10 min. We counted the total number of compressions and those with appropriate depth every 1 min during the 10 min and measured mean compression depth from the start of chest compressions to 10 min.

Results

The 10/100 method showed the deepest compression depth, followed by the 10/200 and CCC methods. The mean compression depth showed a significant difference after 5 min had elapsed. The percentage of adequate compressions per min was calculated as the proportion of compressions with appropriate depth among total chest compressions. The percentage of adequate compressions declined over time for all methods. The 10/100 method showed the highest percentage of adequate compressions, followed by the 10/200 and CCC methods.

Conclusion

When rescuers were provided a rest at a particular time during CCC-CPR, chest compression quality increased compared with CCC without rest. Therefore, we propose that a rescuer should be provided a rest during CCC-CPR, and specifically, we recommend a 10-s rest after 100 chest compressions.  相似文献   
1000.
ObjectiveTo evaluate the participants in the Mayo Clinic Biobank for their representativeness to the entire Employee and Community Health program (ECH) primary care population with regard to hospital utilization.Patients and MethodsParticipants enrolled in the Mayo Clinic Biobank from April 1, 2009, to December 31, 2010, were linked to the ECH population. These individuals were categorized into risk tiers (0-4) on the basis of the number of health conditions present as of December 31, 2010. Outcomes were ascertained through December 31, 2011. Hazard ratios (HRs) and 95% CIs for risk of hospitalization, emergency department (ED) visits, and for risk of hospitalization and emergency department (ED) visits were estimated.ResultsThe 8927 Biobank participants were part of ECH (N=84,872). Compared with the entire ECH population, the Biobank-ECH participants were more likely to be female (64.3% vs 54.6%), older (median age, 58 years vs 47 years), and categorized to tier 0 (6.4% vs 24.0%). There were strong positive associations between tier (tier 4 vs combined tiers 0 and 1) and risk of hospitalization (HR, 5.8; 95% CI, 4.6-7.5) and ED visits (HR, 5.4; 95% CI, 4.2-6.8) among Biobank-ECH participants. Similar associations for risk of hospitalization (HR, 8.5; 95% CI, 7.8-9.3) and ED visits (HR, 6.9; 95% CI, 6.4-7.5) were observed for the entire ECH population.ConclusionAlthough the Biobank-ECH participants were older and had more chronic conditions compared with the overall ECH population, the associations of risk tier with utilization outcomes were similar, supporting the use of the Biobank participants to assess biomarkers for health care outcomes in the primary care setting.  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