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   182241篇
  免费   13274篇
  国内免费   4294篇
耳鼻咽喉   1363篇
儿科学   2528篇
妇产科学   3075篇
基础医学   23767篇
口腔科学   3458篇
临床医学   12218篇
内科学   23415篇
皮肤病学   2276篇
神经病学   12016篇
特种医学   6445篇
外国民族医学   1篇
外科学   14634篇
综合类   24164篇
现状与发展   22篇
一般理论   8篇
预防医学   15568篇
眼科学   2307篇
药学   25831篇
  53篇
中国医学   12969篇
肿瘤学   13691篇
  2024年   354篇
  2023年   2230篇
  2022年   5368篇
  2021年   7614篇
  2020年   6103篇
  2019年   6110篇
  2018年   6145篇
  2017年   6828篇
  2016年   6861篇
  2015年   6420篇
  2014年   7185篇
  2013年   11206篇
  2012年   8983篇
  2011年   10907篇
  2010年   6824篇
  2009年   6926篇
  2008年   8450篇
  2007年   9440篇
  2006年   8944篇
  2005年   8281篇
  2004年   7123篇
  2003年   6381篇
  2002年   5050篇
  2001年   4536篇
  2000年   3811篇
  1999年   3219篇
  1998年   2532篇
  1997年   2643篇
  1996年   2401篇
  1995年   2085篇
  1994年   2016篇
  1993年   1699篇
  1992年   1562篇
  1991年   1463篇
  1990年   1265篇
  1989年   1031篇
  1988年   991篇
  1987年   900篇
  1986年   830篇
  1985年   1211篇
  1984年   971篇
  1983年   733篇
  1982年   756篇
  1981年   620篇
  1980年   604篇
  1979年   478篇
  1978年   298篇
  1977年   259篇
  1976年   243篇
  1975年   187篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Infusion of 1 μg of carbachol, a potent cholinergic agonist, into the lateral septum of the urethane-anaesthetized rat systematically caused the induction of clear-cut hippocampal theta (θ). However, infusion of an equivalent amount of the drug into the hippocampus, close to the recording electrode, failed to induce θ in 50% of the animals and produced a mixture of θ waves and desynchronized activity, resulting in atypical EEG patterns, in the remaining subjects. Both carbachol EEG effects were blocked by intraseptal infusion of the antimuscarinic agent, atropine. Our data demontrate that muscarinic receptors in the septum are predominent sites for cholinergic agonist-antagonist action capable of generating or suppressing hippocampal θ in the rat. They also indicate that intraseptal cholinergic mechanisms play an important role in the initiation and generation of this rhythm.  相似文献   
992.
Summary In order to study the immune function of patients on maintenance hemodialysis (MHD), we assayed NK cell cytotoxicity against K562 targets in 40 patients on MHD, and the production of IL-2 and IFN in peripheral blood mononuclear cells (PBMC) after PHA stimulation, in contrast to those in normal controls. The results showed that NK cell activity and IL-2 and IFN levels were markedly lower in the patients than in the controls. Afeter a single dialysis, NK cell activity as well as IL-2 and IFN levels were elevated to different extent. But there was no significant change in patients after long-term dialysis. There was a positive correlation between the NK cell activity and IL-2 and IFN activity in the controls, but no such correlation was found in the patients on MHD. There was a positive correlation between the NK cell activity and IL-2 activity in patients after dialysis, suggesting that immune function were impaired in the patients on MHD, with a decline in the activity of NK cell and IL-2 and IFN, and a disorder of immune regulation cycle. These abnormal immune impairments in the patients could be partly corrected by hemodialysis. However, long-term hemodialysis is not much helpful in the improvement of patient’s immune function.  相似文献   
993.
The healing effect of human epidermal growth factor (hEGF) on open wounds was studied in rats. No improvement in wound healing was found by topical application of EGF alone to open wound sites. We found an ointment containing EGF and a protease inhibitor, nafamostat mesilate or gabexate mesilate, or gelatin accelerated the healing rate of open wounds. Significant increases in the dry weight of the wound site granulation tissue, uronic acid (as an index of acid mucopolysaccharide) and hydroxyproline (as an index of collagen) were observed by treatment with EGF ointment containing nafamostat compared with the controls. The effects of the protease inhibitor on wound healing were dose dependent. Nafamostat was more efficient than gabexate or gelatin on wound healing. The degradation of 125I-EGF in wound tissue homogenate was significantly decreased in the presence of a protease inhibitor, such as nafamostat or gabexate, or gelatin. These findings indicate that the stabilization of EGF at the wound site is an important factor in permitting the expression of its healing effects and suggest that the ointment containing EGF and a stabilizing agent would be a suitable dosage form for acceleration of wound repair.  相似文献   
994.
体外测定青蒿琥酯钠(SA)对大鼠红细胞膜Na~( )-K~( )-交换ATP酶活性的影响.方法:在反应系统中分别加入不同浓度的SA(0,0.5,1,5和10 μmol·L~(-1)),通过测定反应系统中释放的无机磷含量,计算酶活性.结果:随着SA浓度(O,0.5,1,5和10 μmol·L~(-1))的增高,对Na~( )-K~( )-交换ATP酶活性的抑制作用也随之增强,抑制率分别为15%,29%,46%和75%.将底物ATP浓度增加为125,250,375和500 μmol·L~(-1),进行了酶的动力学测定.用直线回归分析作Eadie-Hofstee动力学曲线,结果表明,SA对该酶的抑制作用为竞争性抑制.结论:提示SA可影响宿主红细胞膜的离子转运及膜的功能.  相似文献   
995.
A patient with neutropenia and life-threatening infections secondary to T-γ lymphoproliferative disease, who did not respond to treatment with recombinant human G-CSF (filgrastim), was treated with filgrastim plus cyclosporine A (CyA). The patient achieved a good response in the absolute neutrophil count and subsequently required a dose reduction in the filgrastim. The patient was eventually discontinued from the CyA but continues on filgrastim alone. While on therapy, the large granular lymphocytes disappeared from the circulation and the beta-TCR rearrangement, which was present prior to beginning therapy, became undetectable. The patient had no significant toxicity to the CyA or the filgrastim and he has not experienced any serious infections or required hospitalization. Filgrastim has proven to be relatively nontoxic and of some benefit to patients with this disease and should probably be utilized first when treatment is necessary. However, if improvement is not observed, these findings suggest that a trial of the combination of CyA plus filgrastim may be beneficial.  相似文献   
996.
33例肝占位性病变MRI误诊的分析   总被引:1,自引:0,他引:1  
我院1988年以来4000余例腹部MRI中,发现肝占位性病变误诊33例。所用机型为美国Disonics公司0.5T超导MRI,自旋回波序列(SE序列)、常规T1加权(T1WI)、质子加权(PDWI)、T2加权(T2WI),覆盖全肝。其中,PHC误诊为MHC5例、MHC误诊为PHC6例、PHC误为HHE5例、MHC误诊为HHE2例、HHE误诊为PHC6例、肝硬化结节误诊为PHC2例、炎性假瘤误诊为PHC3例、肝结核误诊为PHC1例、HCY误诊为HHE3例。本文从病变的影像学特征和扫描技术方面详细探讨了误诊的原因和鉴别诊断要点。  相似文献   
997.
利用于氨三乙酸存在下,锰(Ⅱ)对高碘酸钾氧化二甲苯蓝FF的催化效应,建立了一个新的测定微量锰的动力学分光光度法。该法检出限为6×10 ̄(-2)ng·ml ̄(-1),线性范围为0.2~8.0ng·2.5ml ̄(-1),常见离子基本不干扰测定。用于直接测定健齿茶和茉莉花茶中的锰含量,结果发现,锰含量分别为2214μg·g ̄(-1)及648μg·g ̄(-1)。此法简便易行,灵敏度高。  相似文献   
998.
999.
Purpose. To assess the accuracy of different MR sequences for the detection of articular cartilage abnormalities in rheumatoid arthritis. Design and patients. Ten metacarpophalangeal joints and 10 metatarsophalangeal joints (specimens from arthritis patients undergoing ablative joint surgery) were examined with a fat-suppressed (FS) 3D FLASH, a FS 3D FISP, a FS 2D fast spin-echo T2-weighted, and a 2D FS spin-echo T1-weighted sequence. Each cartilage lesion and each cortical lesion was graded from 0 to 4 (modified Outerbridge staging system). Subsequently, the results of each sequence were compared with the macroscopic findings and statistically tested against each other. Results. The study shows that 3D gradient-echo sequences with fat suppression were best for imaging and grading of cartilage lesions in arthritis of the small joints of the hands and feet. Using 3D techniques, all grade 2, grade 3, and grade 4 lesions of cartilage or cortical bone were detected. Conclusion. FS 3D gradient-echo techniques were best for the detection and grading of hyaline cartilage and subchondral bone lesions in rheumatoid arthritis. MRI has a great potential as an objective method of evaluating cartilage damage and bone erosions in rheumatoid arthritis.  相似文献   
1000.
Mechanical waves in magnetic resonance imaging, which have been suggested for possible clinical applications, were analyzed with regard to imaging of the viscoelastic properties of large objects. The method is based on the Larmor frequency modulation caused by the application of mechanical waves. Possible clinical applications include all diseases that result in a change in the mechanical properties of biologic tissues (eg, atherosclerosis).  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