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   21077篇
  免费   1405篇
  国内免费   158篇
耳鼻咽喉   354篇
儿科学   353篇
妇产科学   409篇
基础医学   2805篇
口腔科学   510篇
临床医学   1897篇
内科学   4380篇
皮肤病学   590篇
神经病学   1350篇
特种医学   1135篇
外科学   2769篇
综合类   779篇
现状与发展   1篇
一般理论   14篇
预防医学   1082篇
眼科学   722篇
药学   1618篇
中国医学   170篇
肿瘤学   1702篇
  2023年   204篇
  2022年   433篇
  2021年   773篇
  2020年   442篇
  2019年   548篇
  2018年   705篇
  2017年   511篇
  2016年   622篇
  2015年   819篇
  2014年   1005篇
  2013年   1075篇
  2012年   1709篇
  2011年   1657篇
  2010年   929篇
  2009年   835篇
  2008年   1173篇
  2007年   1149篇
  2006年   1122篇
  2005年   1063篇
  2004年   840篇
  2003年   690篇
  2002年   566篇
  2001年   526篇
  2000年   511篇
  1999年   405篇
  1998年   132篇
  1997年   110篇
  1996年   76篇
  1995年   86篇
  1994年   82篇
  1993年   64篇
  1992年   155篇
  1991年   167篇
  1990年   137篇
  1989年   129篇
  1988年   116篇
  1987年   133篇
  1986年   106篇
  1985年   94篇
  1984年   73篇
  1983年   69篇
  1982年   36篇
  1979年   60篇
  1977年   39篇
  1975年   38篇
  1974年   39篇
  1973年   36篇
  1972年   37篇
  1970年   35篇
  1969年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Formaldehyde (FA) is an important substance that induces sick house syndrome and diseases, such as asthma and allergies. Oxidative stress is involved in the development of respiratory disease, and diverse antioxidants may protect respiratory tract cells from apoptosis. Peroxiredoxin is a pivotal endogenous antioxidant. In the present study, FA induced death in A549 cells, a lung epithelial cell line, in a dose-dependent manner. FA also increased lipid peroxide formation (LPO) in A549 cells, suggesting a role for oxidative stress. Additionally, FA decreased peroxiredoxin 2 (Prx 2) protein levels after a 24 or 48 h exposure to FA. We also examined whether the FA-induced decrease in Prx 2 was associated with apoptosis. Prx 2 overexpression protected against FA-induced cell apoptosis but not necrosis. Prx 2 overexpression blocked FA-induced increase in Bax, a pro-apoptotic molecule, and a decrease in Bcl-2, an anti-apoptotic molecule. Prx 2 overexpression also protected against FA-induced activation of some special apoptosis-associated proteins [caspase-3, caspase-9, and polypeptide poly (ADP-ribose) polymerase (PARP)]. Furthermore, we examined the signaling molecules involved in the FA-induced decrease in Prx 2 expression. The FA-induced decrease in Prx 2 and increase in cell apoptosis was restored by treatment with SB203580 [a p38 mitogen activated protein kinase (MAPK) inhibitor], but not by SP600125 [a c-jun-N-terminal kinase (JNK) inhibitor]. Also, FA-induced events were blocked by treatment with p38 siRNA, but not by scrambled siRNA. Indeed, FA increased p38 MAPK activation, suggesting a role for p38 MAPK in FA action. In conclusion, FA mediated apoptosis in lung epithelial cells by decreasing Prx 2 via p38 MAPK.  相似文献   
982.
Occupational exposure limits (OELs) are used as an important tool to protect workers from adverse chemical exposures and its detrimental effects on their health. The Ministry of Labor (MOL) can establish and publish OELs based on the Industrial Safety and Health Act in Korea. The first set of OELs was announced by the MOL in 1986. At that time, it was identical to the Threshold Limit Values of the American Conference of Governmental Industrial Hygienists. Until 2006, none the first OELs except for those of three chemicals (asbestos, benzene, and 2-bromopropane) were updated during the last twenty years. The Hazardous Agents Review Committee established under the MOL selected 126 chemicals from 698 chemicals covered by OELs using several criteria. From 2005 to 2006, the MOL provided research funds for academic institutions and toxicological laboratories to gather the evidence documenting the need to revise the outdated OELs. Finally, the MOL notified the revised OELs for 126 chemicals from 2007 to 2008. The revised OELs of 58 substances from among these chemicals were lowered to equal or less than half the value of the original OELs. This is the most substantial change in the history of OEL revisions in Korea.  相似文献   
983.
Bisphenol A (BPA) is known as an estrogen-mimic environmental hormone which has the ability to indirectly stimulate the production of allergic inflammation-related cytokines. Cudrania tricuspidata Bureau (CTB) has been used in Korean folk medicine for a long time. In order to determine the inhibitory effect of a glycoprotein (CTB glycoprotein, 75 kDa) isolated from CTB fruits on the activities of allergic inflammation-related cytokines (TNF-α and IL-6) caused by BPA, we evaluated the activities of protein kinase C (PKC), p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor (NF)-κB, and inflammation-related cytokine (TNF-α and IL-6) in the BPA-induced HMC-1 cells using immunoblot analysis and RT-PCR. The results obtained from this study revealed that CTB glycoprotein (100 μg/ml) inhibits the translocation of PKC from cytosol to the membrane, the phosphorylation of p38 MAPK, the activation of NF-κB, and the expression levels of TNF-α and IL-6. Taken together, the results in this study suggest that CTB glycoprotein inhibits the expression of allergic inflammation-related cytokines (TNF-α and IL-6) by blocking NF-κB and p38 kinase in BPA-induced HMC-1 cells.  相似文献   
984.
A lot of anti-diabetic agents using natural plants have been extensively studied. Ginsenosides are known to be used as a remedy for diabetes in Asian countries and American Societies. Diabetic nephropathy is a major complication of diabetes mellitus. Extracellular matrix in mesangial cells is mainly composed of fibronectin and the increase of fibronectin is a hallmark of diabetic nephropathy. Protopenaxadiol (PPD) is a major component of total ginseng. Thus, we examined the regulatory mechanism of PPD derivatives-induced preventive effect of fibronectin expression in mesangial cells cultivated under diabetic condition. In present study, ginsenoside Rb1 prevented the high glucose-induced increase of fibronectin expression in mesangial cells. Ginsenoside Rb2 and Rg3 also mildly inhibited it. However, ginsenoside Rc and Rd did not prevent the high glucose-induced increase of fibronectin expression in mesangial cells. In addition, ginsenoside Rb1 prevented high glucose-induced phosphorylation of p44/42 mitogen activated protein kinase (MAPK), p38 MAPK, JNK/SAPK, and Akt. These results suggest that ginsenoside Rb1 is the most powerful component of PPD derivatives. In conclusion, ginsenoside Rb1 prevented high glucose-induced increase of fibronectin expression via the inhibition of MAPK-Akt signaling cascade.  相似文献   
985.
The present work aimed to assess novel pharmacological properties of ethyl vanillin (EVA) which is used as a flavoring agent for cakes, dessert, confectionary, etc. EVA exhibited an inhibitory activity in the chorioallantoic membrane angiogenesis. Anti-inflammatory activity of EVA was convinced using the two in vivo models, such as vascular permeability and air pouch models in mice. Antinociceptive activity of EVA was assessed using acetic acid-induced writhing model in mice. EVA suppressed production of nitric oxide and induction of inducible nitric oxide synthase in the lipopolysaccharide (LPS)-activated RAW264.7 macrophage cells. However, EVA could not suppress induction of cyclooxygenase-2 in the LPS-activated macrophages. EVA diminished reactive oxygen species level in the LPS-activated macrophages. EVA also suppressed enhanced matrix metalloproteinase-9 gelatinolytic activity in the LPSactivated RAW264.7 macrophage cells. EVA at the used concentrations couldn’t diminish viability of the macrophage cells. Taken together, the anti-angiogenic, anti-inflammatory and anti-nociceptive properties of EVA are based on its suppressive effect on the production of nitric oxide possibly via decreasing the reactive oxygen species level.  相似文献   
986.
987.
The clinical manifestation of most diseases of the central nervous system results from neuronal dysfunction or loss. Diseases such as stroke, epilepsy and neurodegeneration (e.g. Alzheimer's disease and Parkinson's disease) share common cellular and molecular mechanisms (e.g. oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction) that contribute to the loss of neuronal function. Neurotrophic factors (NTFs) are secreted proteins that regulate multiple aspects of neuronal development including neuronal maintenance, survival, axonal growth and synaptic plasticity. These properties of NTFs make them likely candidates for preventing neurodegeneration and promoting neuroregeneration. One approach to delivering NTFs to diseased cells is through viral vector-mediated gene delivery. Viral vectors are now routinely used as tools for studying gene function as well as developing gene-based therapies for a variety of diseases. Currently, many clinical trials using viral vectors in the nervous system are underway or completed, and seven of these trials involve NTFs for neurodegeneration. In this review, we discuss viral vector-mediated gene transfer of NTFs to treat neurodegenerative diseases of the central nervous system.  相似文献   
988.
In the present study, the antinociceptive profiles of Campanula punctata extract were examined in ICR mice. The Campanula punctata contain a large dose of saponin. Campanula punctata extract administered orally (200 mg/kg) showed an antinociceptive effect as measured by the tail-flick and hot-plate tests. In addition, Campanula punctata extract attenuated the writhing numbers in the acetic acid-induced writhing test. Furthermore, the cumulative nociceptive response time for intrathecal (i.t.) injection of substance P (0.7 µg) was diminished by Campanula punctata extract. Intraperitoneal (i.p.) pretreatment with yohimbine (α2-adrenergic receptor antagonist) attenuated antinociceptive effect induced by Campanula punctata extract in the writhing test. However, naloxone (opioid receptor antagonist) or methysergide (5-HT serotonergic receptor antagonist) did not affect antinociception induced by Campanula punctata extract in the writhing test. Our results suggest that Campanula punctata extract shows an antinociceptive property in various pain models. Furthermore, this antinociceptive effect of Campanula punctata extract may be mediated by α2-adrenergic receptor, but not opioidergic and serotonergic receptors.  相似文献   
989.
Spastic paraplegia is a neurodegenerative disorder characterized by progressive leg weakness and spasticity due to degeneration of corticospinal axons. SPG7 encodes paraplegin, and pathogenic variants in the gene cause hereditary spastic paraplegia as an autosomal recessive trait. Various ophthalmological findings including optic atrophy, ophthalmoplegia, or nystagmus have been reported in patients with spastic paraplegia type 7. We report a 15-year-old male patient with a novel heterozygous variant, c.1224T>G:p.(Asp408Glu) in SPG7 (NM_003119.3) causing early onset isolated optic atrophy and infantile nystagmus prior to the onset of neurological symptoms. Therefore, SPG7 should be considered a cause of infantile nystagmus with optic atrophy.  相似文献   
990.

Objective  

To study the nutritional status of nursing home residents in a multi-racial Asian society and its role in predicting short-term mortality independent of functional status and comorbidities.  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