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   31903篇
  免费   3148篇
  国内免费   2150篇
耳鼻咽喉   234篇
儿科学   502篇
妇产科学   372篇
基础医学   2599篇
口腔科学   465篇
临床医学   4433篇
内科学   3740篇
皮肤病学   282篇
神经病学   1068篇
特种医学   1039篇
外国民族医学   7篇
外科学   2404篇
综合类   7406篇
现状与发展   23篇
一般理论   1篇
预防医学   2976篇
眼科学   598篇
药学   4335篇
  48篇
中国医学   2617篇
肿瘤学   2052篇
  2024年   143篇
  2023年   446篇
  2022年   1149篇
  2021年   1410篇
  2020年   1175篇
  2019年   874篇
  2018年   841篇
  2017年   1029篇
  2016年   845篇
  2015年   1435篇
  2014年   1845篇
  2013年   1950篇
  2012年   2922篇
  2011年   2900篇
  2010年   2215篇
  2009年   1881篇
  2008年   2084篇
  2007年   2135篇
  2006年   1945篇
  2005年   1688篇
  2004年   1216篇
  2003年   1193篇
  2002年   932篇
  2001年   677篇
  2000年   596篇
  1999年   412篇
  1998年   234篇
  1997年   225篇
  1996年   152篇
  1995年   150篇
  1994年   122篇
  1993年   72篇
  1992年   50篇
  1991年   41篇
  1990年   45篇
  1989年   35篇
  1988年   31篇
  1987年   27篇
  1986年   34篇
  1985年   17篇
  1984年   9篇
  1983年   5篇
  1982年   1篇
  1981年   6篇
  1980年   3篇
  1979年   3篇
  1970年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
为了研究不同心电序列转换方式及不同谱估计方法对心率变异性(HRV)信号谱分析结果的影响,本文对积分脉冲频率调制(IPFM)模型及修正积分脉冲频率调制(MIPFM)模型在输入不同振幅与频率的正弦信号时所产生的随机点过程,用两种心电序列转换方法进行转换得到仿真HRV信导;然后,采用周期图与自回归(AR)谱估计方法计算这种厉真HRV信号的功率谱。研究结果表明:①对于MIPFM模型产生的随机点过程,同一心电序列转换方法所得出的仿真HRV信号的AR谱与周期图的谱峰功率估计基本一致;而对IPFM模型则不完全一致。②MIPFM模型仿真实验表明,对实际HRV信号谱分析,使用低,高频谱峰功率比(RF)作为反映心脏自主神经张力平衡的指标时,除心电序列传换及谱估计方法可能造成的误差外,当低频谱峰靠近极低频谱峰时,根据RF值解释生理实验结果会有校大误差。③座分析实际HRV信号的工作中,不同心电序列转换方式产生的伪谐波对HRV谱分析结果的影响不大。  相似文献   
122.
Objective To investigate the association between the-258T/G polymorphism.in the pro-moter of parkin gene and the risk for sporadic parkinson's disease (SPD) in Guangxi Province, and in relationto the age of onset, of PD patients. Methods PCR-RFLP and sequence analysis were used to determine thegenotype of-258T/G polymorphism between all patients and healthy controls. Results The G allele was morecommon in patients than controls (55.20%:43.33% ,x2=6.898, P<0.05, OR=1.61, 95% CI: 1.13 ~2.30). The frequency of GG genotype was higher in patients than in controls (28.00 %: 18.33%, x2=7.159, P<0.05, OR=2.75, 95% CI : 1.31 ~ 5.77). The frequency of TG + GG genotype was higher in pa-tients than in controls (82.40%:68.33%, x2=6.551, P<0.05, OR=2.17.95%CI: 1.20 ~3.93). Afterbeing stratified by onset age, the frequencies of the G allele and GG genotype were significantly higher in pa-tients with onset age over 50 years than those in controls respectively. On the other hand, the frequency was notsignificantly different between the younger onset PD patients and the controls. Conclusion The parkin promot-er-258T/G polymorphism might be a risk factor for PD in Guangxi Province, and the G allele was increasedwith increasing age.  相似文献   
123.
用PCR扩增tim基因检测蓝氏贾第鞭毛虫   总被引:1,自引:1,他引:1  
采用聚合酶链反应 (PCR)对蓝氏贾第鞭毛虫 (Giardialamblia)的磷酸丙糖异构酶 (triosephosphateisomerase ,缩写为tim)基因进行特异性扩增 ,结果扩增出 1条 6 83bp的DNA片段。此方法的特异性可高达10 0 % ,而其它DNA样本 ,如日本血吸虫 (Schistosomajaponicum)、刚地弓形虫 (Toxoplasmagondii)、微小隐孢子虫 (Cryptosporidiumparvum)、溶组织内阿米巴 (Entamoebahistolytica)、旋毛虫 (Trichinellaspiralis)和阴道毛滴虫 (Trichomonasvaginalis) ,以及人体血细胞等均未出现扩增反应。本法的敏感性也很高 ,可检测到0 4pg贾第虫包囊的DNA。 13株来自不同地理位置和 或宿主的贾第虫DNA样本在PCR中均各产生 1条长为 6 83bp的目的片段。上述结果表明本实验建立的检测贾第虫的PCR方法有效  相似文献   
124.
人际交往训练降低医学生心理应激反应的实验研究   总被引:3,自引:0,他引:3  
目的 探讨人际交往训练降低医学生心理应激反应的有效模式 ,以培养交往手段 ,促进身心健康 ,提高学习效率。方法 从云南中医学院中医专业 2 0 0 0级 8个班 ,41 2名学生中随机抽取 2个班 ,共 1 0 6人为被试对象 ,结合专业学习 ,在生理学课堂教学中贯穿人际交往训练 ,训练前后分别测查 90项症状自评量表 ( SCL-90 )和防御方式问卷 ( DSQ) ,并用 Q分类法检验被试课前和课后自我评价。最后 ,对被试和其余 6个班的学生进行生理测验 ,并对测验成绩进行比较。结果 被试在交友信心、乐观豁达、口头表达、积极接纳、说服技巧方面均比训练前有显著和极显著提高 ;且考前心理应激反应明显降低 ,防御方式趋向成熟 ,测验及格率高于其余 6个班。结论 结合专业进行人际交往训练可在近期内改善医学生的心理健康水平 ,有利于提高学习效率 ,深受大学生欢迎  相似文献   
125.
The major consequence of long-term diabetes is the increased incidence of disease of the vasculature. Of the underlying mechanisms leading to disease, the accumulation of advanced glycation end products (AGEs), resulting from the associated hyperglycemia, is the most convincing. Interaction of AGEs with their receptor, RAGE, activates numerous signaling pathways leading to activation of proinflammatory and procoagulatory genes. Studies in rodent models of macro- and microvascular disease have demonstrated that blockade of RAGE can prevent development of disease. These observations highlight RAGE as a therapeutic target for treatment of diabetic vascular disease.  相似文献   
126.
To elucidate the involvement of type IV collagenases [matrix metalloproteinase (MMP)-2 and MMP-9] and their tissue inhibitors (TIMP-1 and TIMP-2) in the development of gestational trophoblastic disease (GTD), we quantified their levels in hydatidiform mole and choriocarcinoma tissues using specific enzyme-linked immunosorbent assays, and the results were compared with those from normal first trimester placenta. Levels of pro-MMP-2 were increased in hydatidiform mole, and they were further elevated in choriocarcinoma. Levels of pro-MMP-9 in choriocarcinoma and those of TIMP-1 in both hydatidiform mole and choriocarcinoma were also increased. In contrast, TIMP-2 levels were markedly decreased in both hydatidiform mole and choriocarcinoma. Similar results were obtained by the tissue culture of first trimester placenta and hydatidiform mole. Gelatin zymography indicated that the levels of both pro- and activated forms of MMP-2 and MMP-9 were higher in hydatidiform mole and choriocarcinoma. The decreased expression of TIMP-2 in hydatidiform mole and choriocarcinoma was confirmed by Western blot, Northern blot and immunohistochemistry, with the decrease being more pronounced in choriocarcinoma. Taken together, the present study shows that both TIMP-2 mRNA and protein levels are markedly decreased in GTD and the imbalance of MMP-TIMP production, shifted toward greater MMP activity, may be involved in the pathogenesis of GTD.  相似文献   
127.
128.
In our previous study we demonstrated that acupuncture at Shenmen (HT7) points suppressed a decrease of accumbal dopamine (DA) release in ethanol-withdrawn rats. Furthermore, here we found that it inhibited behavioral withdrawal signs of ethanol. In an effort to better understand the mechanisms underlying this inhibition, the potential role of GABA receptor system in acupuncture was investigated. Male Sprague–Dawley rats were treated with 3 g/kg/day of ethanol (20%, w/v) or saline by intraperitoneal injection for 21 days. Following 48 or 72 h of ethanol withdrawal, acupuncture was applied at bilateral HT7 for 1 min. The selective GABAA antagonist bicuculline and the selective GABAB antagonist SCH 50911 were injected intraperitoneally 20 min before acupuncture, respectively. Importantly, suppressive effects of acupuncture on DA deficiency were completely abolished by SCH 50911, but not by bicuculline, whereas ameliorating effects of acupuncture on ethanol withdrawal syndrome were completely blocked either by SCH 50911 or bicuculline. These results suggest that acupuncture at specific acupoint HT7 may normalize the DA release in the mesolimbic system and attenuate withdrawal syndrome through the GABAB receptor system in ethanol-withdrawn rats.  相似文献   
129.
MaxiK channel partners: physiological impact   总被引:7,自引:2,他引:7  
The basic functional unit of the large-conductance, voltage- and Ca2+-activated K+ (MaxiK, BK, BKCa) channel is a tetramer of the pore-forming α-subunit (MaxiKα) encoded by a single gene, Slo , holding multiple alternative exons. Depending on the tissue, MaxiKα can associate with modulatory β-subunits (β1–β4) increasing its functional diversity. As MaxiK senses and regulates membrane voltage and intracellular Ca2+, it links cell excitability with cell signalling and metabolism. Thus, MaxiK is a key regulator of vital body functions, like blood flow, uresis, immunity and neurotransmission. Epilepsy with paroxysmal dyskinesia syndrome has been recognized as a MaxiKα-related disorder caused by a gain-of-function C-terminus mutation. This channel region is also emerging as a key recognition module containing sequences for MaxiKα interaction with its surrounding signalling partners, and its targeting to cell-specific microdomains. The growing list of interacting proteins highlights the possibility that associations with the C-terminus of MaxiKα are dynamic and depending on each cellular environment. We speculate that the molecular multiplicity of the C-terminus (and intracellular loops) dictated by alternative exons may modulate or create additional interacting sites in a tissue-specific manner. A challenge is the dissection of MaxiK macromolecular signalling complexes in different tissues and their temporal association/dissociation according to the stimulus.  相似文献   
130.
Novel X-linked mental retardation syndrome with short stature maps to Xq24   总被引:1,自引:0,他引:1  
Microdeletions in the 22q11 region are associated with a wide range of overlapping phenotypes. The main manifestations of the syndrome include palatal anomalies such as cleft palate or velopharyngeal insufficiency, conotruncal heart defects, hypocalcemia, immune disorders, and minor facial anomalies. Because of the wide variability, facial changes appear to be the most constant manifestation of the syndrome and characteristic for informed physicians. The purpose of this study is to report the preliminary results of a detailed analysis of anthropometric data (35 measurements) in 15 patients (7 females and 8 males between 5 and 38 years of age, all white Europeans) with a 22q11 microdeletion. Objective anthropometric study showed that 19 measurements and 7 indexes were significantly different between 22q11 patients and normative database. The typical face showed a short forehead with an anterior vertical excess. Downslanting eyes and large binocular width were the most common anomalies in the orbital area. The nose showed anomalies with a large root, a short tip, and a narrow alar base. There was a narrowing of the mouth and thin lips. Ears were small and slightly disharmonic for the children. Statistical comparison between children (10 cases) and adults (5 cases) showed that craniofacial assessment was more demonstrative in children than in adults.  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