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   709篇
  免费   40篇
  国内免费   8篇
耳鼻咽喉   7篇
儿科学   43篇
妇产科学   7篇
基础医学   85篇
口腔科学   29篇
临床医学   48篇
内科学   190篇
皮肤病学   12篇
神经病学   28篇
特种医学   24篇
外科学   124篇
综合类   14篇
一般理论   2篇
预防医学   54篇
眼科学   8篇
药学   30篇
中国医学   2篇
肿瘤学   50篇
  2024年   4篇
  2023年   4篇
  2022年   16篇
  2021年   21篇
  2020年   17篇
  2019年   18篇
  2018年   26篇
  2017年   18篇
  2016年   18篇
  2015年   23篇
  2014年   20篇
  2013年   38篇
  2012年   61篇
  2011年   50篇
  2010年   36篇
  2009年   29篇
  2008年   25篇
  2007年   33篇
  2006年   31篇
  2005年   27篇
  2004年   21篇
  2003年   17篇
  2002年   19篇
  2001年   14篇
  2000年   8篇
  1999年   10篇
  1998年   7篇
  1997年   6篇
  1995年   3篇
  1992年   7篇
  1991年   5篇
  1990年   9篇
  1989年   7篇
  1988年   10篇
  1987年   12篇
  1986年   10篇
  1985年   7篇
  1984年   4篇
  1983年   6篇
  1982年   7篇
  1981年   9篇
  1980年   4篇
  1979年   8篇
  1978年   4篇
  1977年   6篇
  1974年   3篇
  1972年   5篇
  1971年   2篇
  1970年   2篇
  1967年   2篇
排序方式: 共有757条查询结果,搜索用时 15 毫秒
41.

Introduction

Posterior fossa tumors are the most common brain tumor of children. Aggressive resection correlates with long-term survival. A high incidence of posterior fossa syndrome (PFS), impairing the quality of life in many survivors, has been attributed to damage to bilateral dentate nucleus or to cerebellar output pathways. Using diffusion tensor imaging (DTI), we examined the involvement of the dentothalamic tracts, specifically the superior cerebellar peduncle (SCP), in patients with posterior fossa tumors and the association with PFS.

Methods

DTI studies were performed postoperatively in patients with midline (n?=?12), lateral cerebellar tumors (n?=?4), and controls. The location and visibility of the SCP were determined. The postoperative course was recorded, especially with regard to PFS, cranial nerve deficits, and oculomotor function.

Results

The SCP travels immediately adjacent to the lateral wall of the fourth ventricle and just medial to the middle cerebellar peduncle. Patients with midline tumors that still had observable SCP did not develop posterior fossa syndrome (N?=?7). SCPs were absent, on either preoperative (N?=?1, no postoperative study available) or postoperative studies (N?=?4), in the five patients who developed PFS. Oculomotor deficits of tracking were observed in patients independent of PFS or SCP involvement.

Conclusion

PFS can occur with bilateral injury to the outflow from dentate nuclei. In children with PFS, this may occur due to bilateral injury to the superior cerebellar peduncle. These tracts sit immediately adjacent to the wall of the ventricle and are highly vulnerable when an aggressive resection for these tumors is performed.  相似文献   
42.
We investigated whether dissimilar biochemical fractions originating in anatomically discrete sections of the pomegranate (Punica granatum) fruit might act synergistically against proliferation, metastatic potential, and phosholipase A2 (PLA2) expression of human prostate cancer cells in vitro . Proliferation of DU 145 human prostate cancer cells was measured following treatment with a range of therapeutically active doses of fermented pomegranate juice polyphenols (W) and sub-therapeutic doses of either pomegranate pericarp (peel) polyphenols (P) or pomegranate seed oil (Oil). Invasion across Matrigel by PC-3 human prostate cancer cells was measured following treatment with combinations of W, P and Oil such that the total gross weight of pomegranate extract was held constant. Expression of PLA2, associated with invasive potential, was measured in the PC-3 cells after treatment with the same dosage combinations as per invasion. Supra-additive, complementary and synergistic effects were proven in all models by the Kruskal-Wallis non-parametric H test at p < 0.001 for the proliferation tests, p < 0.01 for invasion, and p < 0.05 for PLA2 expression. Proliferation effects were additionally evaluated with CompuSyn software median effect analysis and showed a concentration index CI < 1, confirming synergy. The results suggest vertical as well as the usual horizontal strategies for discovering pharmacological actives in plants.  相似文献   
43.

Ethnopharmacological relevance

While camel urine (CU) is widely used in the Arabian Peninsula to treat various diseases, including cancer, its exact mechanism of action is still not defined. The objective of the present study is to investigate whether camel urine has anti-cancer effect on human cells in vitro.

Materials and methods

The annexinV/PI assay was used to assess apoptosis, and immunoblotting analysis determined the effect of CU on different apoptotic and oncogenic proteins. Furthermore, flow cytometry and Elispot were utilized to investigate cytotoxicity and the effect on the cell cycle as well as the production of cytokines, respectively.

Results

Camel urine showed cytotoxicity against various, but not all, human cancer cell lines, with only marginal effect on non-tumorigenic epithelial and normal fibroblast cells epithelial and fibroblast cells. Interestingly, 216 mg/ml of lyophilized CU inhibited cell proliferation and triggered more than 80% of apoptosis in different cancer cells, including breast carcinomas and medulloblastomas. Apoptosis was induced in these cells through the intrinsic pathway via Bcl-2 decrease. Furthermore, CU down-regulated the cancer-promoting proteins survivin, β-catenin and cyclin D1 and increased the level of the cyclin-dependent kinase inhibitor p21. In addition, we have shown that CU has no cytotoxic effect against peripheral blood mononuclear cells and has strong immuno-inducer activity through inducing IFN-γ and inhibiting the Th2 cytokines IL-4, IL-6 and IL-10.

Conclusions

CU has specific and efficient anti-cancer and potent immune-modulator properties in vitro.  相似文献   
44.
OBJECTIVES: Clinicians are told to use the number needed to treat (NNT) to compare the benefits of therapeutic strategies, and researchers are asked to report results this way, generally without considering differences among the studies from which these were derived. METHODS: The crude NNT currently advocated is compared to the NNT standardized for a common outcome, follow-up time, study population and comparator. An NNT model for cardiovascular disease is described as an example that addresses differences among studies of secondary prevention of cardiovascular disease. Crude NNTs are compared to those obtained from the model. RESULTS: Follow-up in the 18 trials identified varied from 1.0 to 6.2 years; rates of cardiovascular events in the untreated subgroups ranged from 4.8% to 45.9%. The crude NNTs were more variable (9.1-163.7) than those obtained from the model (9.1-75.2). The effect of standardization was substantial in some cases, with proportional changes ranging from a 91% decrease to a 223% increase. CONCLUSION: Using an NNT model to account for differences in study design allows for more meaningful comparisons.  相似文献   
45.
Michael HN  Salib JY  Ishak MS 《Die Pharmazie》2002,57(12):859-860
Ten phenolic and flavonoid compounds including one new acylated flavonol glycoside were isolated from Psidium gauijava seeds. The structures of the new compound quercetin-3-O-beta-D-(2"-O-galloyl glucoside)-4'-O-vinylpropionate and of the known compounds were elucidated by different chemical and physical methods, 1H- and 13C NMR spectral analysis.  相似文献   
46.
This study was designed to investigate the possible participation of morphine in pulmonary oedema induced by alpha-naphthylthiourea (ANTU), which is a well-known noxious chemical agent in the lung. Injection of ANTU (15 mg/kg i.p.) produced pulmonary oedema as indicated by an increase in lung weight/body weight ratio and pleural effusion reaching a maximum within 4 h in rat. Administration of morphine prior to ANTU significantly inhibited to pulmonary oedema with a dose-dependent manner. The protective effect of morphine is prevented by peripheral opioid receptor antagonist, naloxone methiodide. ANTU-treated rats were shown positive by inducible nitric oxide synthase immunohistochemical staining. There was no staining in the control group. On the other hand, the degree of staining was markedly reduced in tissue sections by morphine. These results suggest that previous administration of subcutaneous morphine has preventive effect on ANTU-induced pulmonary inflammatory reaction and its effect mediated via peripheral opioid receptors. Application of naloxone with ANTU has no effect on the lung parameters indicating that endogenous opioids do not modulate ANTU-induced damage.  相似文献   
47.
Risk factors for primary Middle East respiratory syndrome coronavirus (MERS-CoV) illness in humans are incompletely understood. We identified all primary MERS-CoV cases reported in Saudi Arabia during March–November 2014 by excluding those with history of exposure to other cases of MERS-CoV or acute respiratory illness of unknown cause or exposure to healthcare settings within 14 days before illness onset. Using a case–control design, we assessed differences in underlying medical conditions and environmental exposures among primary case-patients and 2–4 controls matched by age, sex, and neighborhood. Using multivariable analysis, we found that direct exposure to dromedary camels during the 2 weeks before illness onset, as well as diabetes mellitus, heart disease, and smoking, were each independently associated with MERS-CoV illness. Further investigation is needed to better understand animal-to-human transmission of MERS-CoV.  相似文献   
48.
A key feature of Parkinson's disease is the dopaminergic neuronal cell loss in the substantia nigra pars compacta. Many triggering pathways have been incriminated in the pathogenesis of this disease including inflammation, oxidative stress, excitotoxicity and apoptosis. Thyroid hormone is an essential agent for the growth and maturation of neurons; moreover, it has variable mechanisms for neuroprotection. So, we tested the efficacy of l-thyroxin as a neuroprotectant in rotenone model of Parkinson's disease in rats. Thirty Sprague Dawley rats aged 3 months were divided into 3 equal groups. The first received daily intraperitoneal injections of 0.5% carboxymethyl cellulose (CMC) 3 mL/Kg. The second group received rotenone suspended in 0.5% CMC intraperitoneally at a dose of 3 mg/kg, daily. The third group received the same rotenone regimen subcutaneous l-thyroxine at a dose of 7.5 μg daily. All animals were evaluated regarding locomotor disturbance through blinded investigator who monitored akinesia, catalepsy, tremors and performance in open field test. After 35 days the animals were sacrificed and their brains were immunostained against anti-tyrosine hydroxylase and iba-1. Photomicrographs for coronal sections of the substantia nigra and striatum were taken and analyzed using image J software to evaluate cell count in SNpc and striatal fibers density and number of microglia in the nigrostriatal system. The results were then analyzed statistically. Results showed selective protective effects of thyroxin against rotenone induced neurotoxicity in striatum, however, failed to exert similar protection on SN. Moreover, microglial elevated number in nigrostriatal system that was induced by rotenone injections was diminished selectively in striatum only in the l-thyroxin treated group. One of the possible mechanisms deduced from this work was the selective regulation of microglia in striatal tissues. Thus, this study provides an insight into thyroxin neuroprotection warranting further investigation as therapeutic option for Parkinson's disease patients.  相似文献   
49.
Purpose: To estimate health utility values, explore predictors of utility values, and estimate the quality-adjusted life years (Q.A.L.Y.s) gained by treatment in multicentric Castleman’s disease (M.C.D.). Methods: The SF-36 was administered to 79 patients enrolled in a randomized, double-blind, placebo-controlled, multi-national study to determine the safety and efficacy of siltuximab plus best supportive care (B.S.C.) compared with B.S.C., in subjects with symptomatic M.C.D. Utility (SF-6D) scores were derived from the SF-36. Sensitivity analyses using utilities obtained by mapping the SF-36 to the EQ-5D were also conducted. Repeated measures, mixed effects models were conducted to estimate effects of treatment, responder status and?≥?Grade 3 adverse events (A.E.s) on changes in utility values over time, controlling for baseline utility value. Additionally, differential Q.A.L.Y. gain was assessed in the trial using multiple regression. Results: Patients on siltuximab and those who experienced a complete or partial response had higher mean utility values over time than those on placebo or those with stable disease. After an initial response to treatment, the mean utility remained relatively stable for patients on siltuximab and those who experienced a complete or partial response during the period when most patients were on study. A significantly different Q.A.L.Y. gain was found for patients on siltuximab (versus placebo) as calculated by SF-6D (0.070 Q.A.L.Y.s, p?<?.05) scores at 6 months (EQ-5D 0.096 Q.A.L.Y.s, p?<?0.05). Conclusions: Siltuximab demonstrated improved, durable health utility gains in this rare disease over B.S.C. The main SF-6D results were supported by EQ-5D sensitivity analysis. These findings are limited by the small study sample size and substantial missing data caused predominantly by crossover. A longitudinal, multisite international observational study capturing clinical, safety and health-related quality of life (H.R.Q.L.) endpoints are needed to confirm these findings.  相似文献   
50.
This study investigated the dose-dependent and time-course effects of intramuscular (i.m.) and intraperitoneal (i.p.) injection of benzo[a]pyrene (BaP) on the biomarkers EROD activity, GST activity, concentrations of BaP metabolites in bile, and visceral fat deposits (Lipid Somatic Index, LSI) in African catfish (Clarias gariepinus). Intraperitoneal injection resulted in 4.5 times higher accumulation of total selected biliary FACs than i.m. injection. Hepatic GST activities were inhibited by BaP via both injection methods. Dose-response relationships between BaP injection and both biliary FAC concentrations and hepatic GST activities were linear in the i.p. injected group but nonlinear in the i.m. injected fish. Hepatic EROD activity and LSI were not significantly affected by BaP exposure by either injection route. We conclude that i.p. is a more effective route of exposure than i.m. for future ecotoxicological studies of PAH exposure in C. gariepinus.  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