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   1285篇
  免费   63篇
  国内免费   14篇
耳鼻咽喉   2篇
儿科学   13篇
妇产科学   9篇
基础医学   103篇
口腔科学   8篇
临床医学   97篇
内科学   192篇
皮肤病学   24篇
神经病学   56篇
特种医学   141篇
外科学   61篇
综合类   122篇
预防医学   260篇
眼科学   16篇
药学   178篇
  1篇
中国医学   46篇
肿瘤学   33篇
  2023年   5篇
  2022年   27篇
  2021年   33篇
  2020年   20篇
  2019年   26篇
  2018年   38篇
  2017年   25篇
  2016年   24篇
  2015年   33篇
  2014年   74篇
  2013年   70篇
  2012年   95篇
  2011年   82篇
  2010年   70篇
  2009年   48篇
  2008年   49篇
  2007年   60篇
  2006年   38篇
  2005年   67篇
  2004年   37篇
  2003年   51篇
  2002年   20篇
  2001年   33篇
  2000年   27篇
  1999年   19篇
  1998年   21篇
  1997年   27篇
  1996年   28篇
  1995年   20篇
  1994年   21篇
  1993年   20篇
  1992年   15篇
  1991年   12篇
  1990年   15篇
  1989年   23篇
  1988年   5篇
  1987年   9篇
  1986年   3篇
  1985年   8篇
  1984年   8篇
  1983年   5篇
  1982年   4篇
  1981年   9篇
  1980年   5篇
  1979年   5篇
  1978年   5篇
  1977年   4篇
  1976年   5篇
  1975年   5篇
  1971年   2篇
排序方式: 共有1362条查询结果,搜索用时 15 毫秒
71.
Background: In recent years, trace elements (TEs) have gained considerable attention in the course of treatment and diagnosis of ischemic stroke. The purpose of the conducted research was to determine the trace mineral status (Se, Cu, Zn, Cu/Zn ratio, and Cu/Se ratio) in patients with acute ischemic stroke compared to the population of healthy people in the northeastern region of Poland. Materials and methods: 141 patients with acute ischemic stroke (AIS) and 69 healthy control subjects were examined. The serum concentrations of mineral components were assessed by the atomic absorption spectrometry method. Clinical parameters were updated based on medical records. Results: The serum Se and Zn concentrations were significantly decreased (p < 0.0001; p < 0.0001) in patients with AIS compared with healthy control subjects. However, no significant differences were revealed in terms of the serum Cu concentration (p = 0.283). As expected, we found that the serum Cu/Zn and Cu/Se molar ratios were significantly higher (p = 0.001; p < 0.0001) in patients with AIS compared with healthy control subjects. Conclusions: Disturbed metal homeostasis is a significant contributor to AIS pathogenesis. Furthermore, marked disruption of the serum Cu/Zn and Cu/Se molar ratios could serve as a valuable indicator of AIS patients’ nutritional status and oxidative stress levels.  相似文献   
72.
甘净  朱玉秀  刘霞 《预防医学论坛》2014,(5):345-346,349
目的为了解双流县人工游泳池水质卫生状况,提供卫生安全的游泳池水,保证游泳人群的健康。方法按照GB/T17220-1998《公共场所卫生监测技术规范》要求,采集双流县2009~2013年人工游泳池水进行检测,并对结果进行分析。结果 2009~2013年游泳池水质总体合格率为75.76%,且呈逐年上升趋势;合格率较低的指标为尿素、游离余氯等;5年合计检测297份水样,合格225份,合格率为75.76%,2009~2013年检测合格率分别为70.00%、52.78%、79.45%、86.36%,77.78%(P〈0.05)。检测合格率对外开放的公共泳池为73.08%,酒店泳池为76.00%,住宅小区泳池为74.89%,学校泳池为78.26%(P〉0.05)。游离性余氯、尿素、pH值、浑浊度、大肠菌群、细菌总数的合格率分别为93.27%、89.23%、100.00%、100.00%、94.61%、90.91%。结论双流县游泳池水质合格率较低,应加强游泳池水质卫生管理,大力开展相关知识的宣传,提高人群自我保护意识。  相似文献   
73.
In the present study, the effects of MEHP on human hepatocellular liver carcinoma HepG2 cells were investigated. The results showed that MEHP-induced oxidative DNA damage in the treatment groups (?25.00 μM) at 24 h after treatment and in the 100.00 μM treatment group at 36 h after treatment (p < 0.05 or p < 0.01). At 36 h after treatment, MEHP at higher concentrations (?25.00 μM) resulted in a decrease in ATP level, and an increase in the protein levels of cytochrome c and Smac/DIABLO in the cytosol as well as the percentage of apoptotic cells. The activation of caspase-9 and -3 and the expression of the selected apoptosis-related proteins, p53, PUMA, NOXA, Bax and Bcl-2 were also induced. Furthermore, vitamin C, a scavenger of reactive oxygen species, attenuated MEHP-induced apoptosis. These findings indicated that MEHP induced oxidative DNA damage and apoptosis in HepG2 cells, and p53 and its downstream proteins were involved in mitochondria- and caspase-mediated apoptosis induced by MEHP.  相似文献   
74.
Excess production of H2O2 has been implicated in oncogenesis. The object of the present study was twofold: first, to determine the influence of chronic estradiol (E2) on the activities of selected hepatic antioxidant enzymes in female ACI rats, a strain that is highly sensitive to the induction of estrogen dependent mammary tumors; secondly, to evaluate the actions of dietary clofibrate, a peroxisome proliferator, on activities of these enzymes in control and E2-treated ACI rats. Enzymes selected for study were: NAD(P)H quinone oxidoreductase (NQO1), glutathione S-transferase (GST) and glutathione peroxidase (GPx). Cytosolic catalase (CAT) was also measured as an index of peroxisome proferation in control and E2- treated animals. E2 was administered chronically over 6 and 12 week periods from cholesterol pellet implants containing either 1 or 3 mg E2. Animals were fed AIN-76A diets with or without 0.4% clofibrate over the experimental period. NQO1 and GST but not GPx were induced to varying degrees (NQO1 about 300%, and GST about 45–97%) by chronic E2-treatment. E2-induced increases in these activities were completely prevented in rats exposed to dietary clofibrate. Dietary clofibrate also caused slight but significant reductions in baseline activities of NQO1, GST and GPx in control animals. Serum E2 levels, increased approximately 540% in a dose-dependent manner, and were not altered by dietary clofibrate. It is concluded that chronic E2 treatment markedly induces several important hepatic antioxidant enzymes in female ACI rats, and induction of these activities by E2 is inhibited completely by dietary clofibrate. Both of these actions have the potential to markedly influence the profile of E2 metabolites exported from the liver to E2 sensitive extrahepatic tissues and influence the initiation and progression of hormone-dependent tumors.  相似文献   
75.
The use of antioxidants during chemotherapy has been shown to reduce or prevent the undesirable effects experienced by healthy cells. Micronutrient selenium is well known for its antioxidant properties; however, selenium exhibits a bimodal nature in that both its beneficial and toxic properties lie within a limited and narrow dose range. The present study investigated the possible protective effects of selenomethionine (SM) on the cytotoxicity, genotoxicity and clastogenicity of the chemotherapic doxorubicin (DXR), a key chemotherapic used in cancer treatment. Human peripheral lymphocytes were treated in vitro with varying concentrations of SM (0.25 microM, 0.5 microM, 1.0 microM and 2.0 microM), tested in combination with DXR (0.15 microg/mL). SM alone was not cytotoxic and when combined with DXR treatment, reduced the DNA damage index significantly, the frequency of chromosomal aberrations, the number of aberrant metaphases and the frequency of apoptotic cells. The mechanism of chemoprotection of SM may be related to its antioxidant properties as well as its ability to interfere with DNA repair pathways. Therefore this study showed that SM is effective in reducing the genetic damage induced by the antitumoral agent DXR.  相似文献   
76.

Ethnopharmacological relevance

The leaves of Toddalia asiatica (L.) Lam. have been utilized traditionally for the cure of diabetes.

Aim of the study

The present study was aimed to assess the antidiabetic and antioxidant effects of T. asiatica leaves in Streptozotocin (STZ) induced diabetic rats.

Materials and methods

The phytochemical screening, total phenolic content, HPLC analysis, acute toxicity study and oral glucose tolerance test were carried out. Glucose lowering effect of the hexane, ethyl acetate and methanol extracts of T. asiatica leaves was studied in STZ-induced diabetic rats. The antidiabetic and antioxidant activities were studied for the ethyl acetate extract. The effects of extracts on blood glucose, body weight, plasma insulin, total protein, liver glycogen, plasma enzymes (SGOT, SGPT and ALP) and activities of SOD, CAT and GPx were analyzed.

Results

T. asiatica leaves ethyl acetate extract (TALEe) showed highly significant blood glucose lowering effect. Phytochemical evaluation of TALEe showed the presence of alkaloids, terpenoids, cumarins, flavonoids and phenolic compounds. The total phenolic content of TALEe was 126 mg of gallic acid equivalents/g extract. HPLC analysis revealed the presence of flindersine and ulopterol. Acute toxicity study of TALEe revealed no death or toxicity. The oral glucose tolerance test showed lowered area under curve (AUCglucose) values in TALEe treated rats. After treatment with TALEe (250 and 500 mg/kg) for 28 days there was a significant decrease in blood glucose, plasma enzymes (SGOT, SGPT and ALP) and significant increase in body weight, total protein, serum insulin and liver glycogen levels in treated diabetic rats. The activities of antioxidant enzymes SOD, CAT and GPx were reversed to near normal in treated diabetic rats. Histopathology of pancreas in TALEe treated groups showed regeneration of β-cells.

Conclusion

The results of the experiments showed that TALEe exerted significant antidiabetic and antioxidant effects in STZ-induced diabetic rats justifying its traditional use.  相似文献   
77.
用稳定性同位素锌(~(68)Zn和~(70)Zn)对2例志愿者进行了历时15周不同锌营养水平的代谢实验。结果表明,锌代谢池能正确地反映人体的锌营养状况。空腹和餐后血浆锌浓度的差别比单独测定空腹血浆锌浓度更为可靠。每日尿锌和粪锌的排泄量则有一定的局限性。粪便中内源性锌排泄量的测定对确定人体每日锌的供给量标准,具有一定的参考价值。  相似文献   
78.
硒的化学形式对人血中含硒组分的影响   总被引:7,自引:0,他引:7  
夏弈明  赵新娥 《营养学报》1993,15(2):157-162
在低膳食硒地区的农村,对健康男性受试者进行了为期一年的补硒干预试验。所有受试者每天服硒200μg,以硒酸钠或硒蛋氨酸形式供给。血样分析结果表明,这两种形式的硒均能有效地提高低硒人体的谷胱甘肽过氧化物酶(GPx)活力,因而在预防克山病工作中可采用较为经济的硒酸钠;但补硒蛋氨酸后可见“富裕”硒进入了红细胞的Hb和血浆的白蛋白中,而补硒酸钠后未见“富裕”硒,因而为提高人体硒营养水平,以补充硒蛋氨酸形式的硒为宜。  相似文献   
79.
80.
目的调查南京铁路游泳馆卫生状况,探讨游泳馆卫生管理措施。方法游泳馆2010-2012年卫生监测资料:游泳馆水质及微小气候。采用统一调查表进行调查游泳者自觉症状、游泳馆卫生管理情况调查。结果 (1)游泳馆微小气候达标率较高,基本符合国家卫生标准;(2)尿素严重超标,给游泳者健康造成潜在的危害;(3)游离性余氯合格率偏低,游泳者随着游泳时间的延长自感异常症状者普遍增多(x2=101.81,p<0.01);(4)管理力度不够,消毒质量把关不严,无专业消毒剂配置设施及专业保健人员等。结论加强领导,健全组织,全方位监控游泳馆水质,为游泳者提供舒适、卫生的游泳环境。  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