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   43841篇
  免费   3101篇
  国内免费   855篇
耳鼻咽喉   237篇
儿科学   1795篇
妇产科学   1177篇
基础医学   6202篇
口腔科学   1223篇
临床医学   3131篇
内科学   9187篇
皮肤病学   692篇
神经病学   3486篇
特种医学   1974篇
外国民族医学   4篇
外科学   5917篇
综合类   2885篇
现状与发展   3篇
预防医学   2945篇
眼科学   425篇
药学   3574篇
  27篇
中国医学   841篇
肿瘤学   2072篇
  2023年   565篇
  2022年   1243篇
  2021年   1865篇
  2020年   1495篇
  2019年   2530篇
  2018年   2470篇
  2017年   1644篇
  2016年   1226篇
  2015年   1261篇
  2014年   2180篇
  2013年   2165篇
  2012年   1514篇
  2011年   1658篇
  2010年   1345篇
  2009年   1428篇
  2008年   1334篇
  2007年   1196篇
  2006年   1141篇
  2005年   926篇
  2004年   841篇
  2003年   854篇
  2002年   624篇
  2001年   592篇
  2000年   547篇
  1999年   529篇
  1998年   414篇
  1997年   367篇
  1996年   319篇
  1995年   237篇
  1994年   209篇
  1993年   153篇
  1992年   135篇
  1991年   128篇
  1990年   107篇
  1989年   107篇
  1988年   100篇
  1987年   75篇
  1985年   1009篇
  1984年   1796篇
  1983年   1100篇
  1982年   1226篇
  1981年   1191篇
  1980年   985篇
  1979年   881篇
  1978年   803篇
  1977年   684篇
  1976年   791篇
  1975年   558篇
  1974年   496篇
  1973年   552篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A large body of work relating to the occurrence of rickets in UK Asians is reviewed. Several theories of the aetiology of this condition are shown to be untenable: it is not exclusively a function of sunlight deprivation or of darker pigmentation; nor is it simply due to phytate-induced losses of calcium from the gut. Asian rickets, however, is associated with a high consumption of cereals, and experiments with rats have suggested a mechanism. In the absence of adequate vitamin D from sunlight, the low-calcium, high cereal intake of the UK Asian population may induce a state of mild secondary hyperparathyroidism which enhances the destruction of vitamin D and leads to a progressive reduction in vitamin D status and, ultimately, to the development of clinical rickets.  相似文献   
102.
Nephrocalcinosis (NC) detected by ultrasound is a recognized abnormality for some patients with X-linked hypophosphatemia (XLH) who received vitamin D2 and inorganic phosphate therapy, but is commonly observed in XLH patients treated with 1,25-dihydroxyvitamin D3 and inorganic phosphate supplementation. Nevertheless, long-term follow-up of kidney function in XLH patients with NC detected ultrasonographically has not been reported. We investigated two women with XLH, ages 31 (patient 1) and 39 (patient 2) years, each of whom had suffered at least one documented episode of vitamin D2-induced hypercalcemia and renal azotemia during childhood. Patient 2 had also been treated with inorganic phosphate. No medications for XLH had been taken during adulthood. Renal ultrasonography at our institution demonstrated marked bilateral medullary NC in both women. No other explanation was found for their NC that apparently occurred several decades earlier from medical therapy for XLH. Detailed studies (including creatinine clearance, β2-microglobulin excretion, and fasting urinary osmolality and acidification) revealed no impairment of kidney function in either patient. Our findings indicate that subradiographic medullary NC acquired during medical therapy for XLH may persist for decades, but with no adverse renal sequelae. Definitive (long-term) assessment of kidney function in the XLH population with NC, however, will be necessary to fully understand the risk of current medical treatment for this most common heritable form of rickets.  相似文献   
103.
Summary The efficiency of cold storage red blood cells (CSRBC) or whole blood at −80 °C used in 27 Rh(D) negative patients during surgical operation was reported. The Rh(D) negative patients received the transfusion of CSRBC or whole blood stored at −80 °C for 180 to 360 days. The changes in the indexes, such as blood TB, DB, K+, Na+, BUN, Cr, urine protein (URPO), UOB, Hb, HCT, serum total protein, relative to hemolytic reaction and blood volume before and after transfusion were observed. The results showed that after transfusion of CSRBC or whole blood 27 cases were negative for urine protein and UOB, and the levels of BUN and Cr were normal (P>0.05). Blood TB, DB, Hb, and HCT were increased, while pH, blood K+ and blood Na+ was normal with the difference being not significant before and after operation (P>0.05). Plasma protein was decreased, but there was no significant difference before and after operation (P>0.05). It was suggested that CSRBC or whole blood at −80 °C could be safely infused to the Rh(D) negative patients without side effects during the surgical operation. YU Zhongqing, male, born in 1957, Technician in Charge  相似文献   
104.
Cyclin D1在胶质瘤细胞系中表达分布模式的初步研究   总被引:2,自引:1,他引:1  
黄安炀  章翔  曹云新  李霞  刘新平 《医学争鸣》2003,24(22):2024-2026
目的:探讨cyclin D1在胶质瘤细胞系中的细胞周期表达模式,将为从生物学功能上阐明cyclin D1在胶质瘤细胞周期演进中的作用.方法:利用流式细胞仪双参数法和细胞同步化,确定cyclin D1在胶质瘤细胞系SHG-44和BT-325中的细胞周期表达分布模式.结果:在胶质瘤细胞系SHG-44和BT-325中,Cyclin Dl的表达呈细胞周期依赖性:在SHG-44中,cyclin D1在G1期表达最高,4h左右达到峰值,S期及G2/M期下降,但仍可检测到;在BT-325中,cyclin D1在G1期表达最高,6h左右达到峰值,S期及G2/M期下降,但仍可检测到.结论:cyclin D1蛋白质的表达呈细胞周期依赖性,且与细胞周期行进有关;cyclin D1在SHG-44和BT-325胶质瘤细胞进入G1期的早期发挥着重要的生物学作用。  相似文献   
105.
目的:探讨人脑胶质瘤中βcatenin的表达及与细胞增殖的相关性。方法:用免疫组化法观察了47例胶质瘤标本βcatenin、cyclinD1、增殖细胞核抗原(PCNA)的表达,并分析其相关性。结果:在胶质瘤中βcatenin、cyclinD1、PCNA均随肿瘤恶性程度增高而增高(P分别为0.017、0.017、0.027),相关分析发现βcatenin、cyclinD1、PCNA的表达两两相关(P<0.001,P<0.001和P=0.005)。结论:βcatenin表达水平的异常与胶质瘤细胞周期调节紊乱、增殖指数上升有关,因此可能是控制肿瘤细胞增殖活性的候选基因之一。  相似文献   
106.
The serum apolipoprotein A- I (apo A-I) Concentrations in 39 patients with posthepatitis cirrhosis were reported to be 0.87±0.27 g/L lower than that of controls 1.15±0.14 g/L P<0.01. The, decrease of apo. A-I was correlated with the severityof impaired liver function. Apo A- I concentrations in serum correlated positively with decrease of serum albumin (r=0.503 P< 0.01) and negatively with serum bilirubin increase (r=- 0.508 P <0.01) . The data indicate that decreasing of apo A- I concentration may be regarded as one of the reliable indices reflecting the degree of liver function impairment.  相似文献   
107.
Calorie restriction is important in managing patients with maturity onset diabetes mellitus (NIDDM). The effect of such restriction on calcium metabolism is not known. The objective of this study was to determine whether patients on calorie restricted diets would show any modification of parathyroid hormone (PTH) and calcitonin (CTN). The serum levels of PTH and CTN were measured by radioimmunoassays in 269 patients with NIDDM. The patients were divided into two groups depending on the intake of calorie, and PTH and CTN were monitored for 2 years. Plasma levels of vitamin D were measured by competitive protein binding assays before and after each program. The level of PTH (520.8±266.0 pg/ml) (mean±S.D.) was significantly (P<0.01) higher in 109 diabetic patients whose calorie intake was restricted for 2 years (diet (D) group) as compared with that (256.6±103.8 pg/ml) of 160 diabetic patients whose calorie intake was not restricted (non-diet (ND) group). The daily oral calcium intake of the two groups did not differ significantly. We found no significant difference in the serum PTH level in the ND groupVS. normal control subjects (248.8±98.4, N=78). The serum calcium concentration and the amount of calcium excreted in urine were slightly but significantly (P<0.01) lower in the D than in the ND group. The rate of tubular reabsorption of phosphate (% TRP) was significantly lower in the D group than that in the ND group (P<0.01). The serum CTN level was significantly (P<0.01) lower in the D group (33.9±11.3 pg/ml) than in the ND group (64.9±21.2 pg/ml) 2 years after each treatment. The plasma 1,25-(OH)2-vitamin D level was significantly (P<0.01) lower in the D group (22.2±6.6 pg/ml) than in the ND group (50.6±4.2 pg/ml). When the restriction of calorie intake in the D group was canceled, their PTH levels decreased, which was accompanied by increase in the 1,25-(OH)2-vitamin D levels, whereas their CTN levels were unchanged. These observations suggested that a restricted calorie intake is a risk factor for secondary hyperparathyroidism as well as for a low serum level of CTN in patients with NIDDM.  相似文献   
108.
给出了用“混合型”雅可比级数的泰勒平均逼近黎普希兹函数类的点态估计。  相似文献   
109.
陈勇  金权膺 《江苏医药》1992,18(4):179-181
我们对64例糖尿病患者和20名正常人的糖代谢、脂代谢、血小板和血管内皮细胞前列腺素代谢的水平进行了临床观察。发现糖尿病患者载脂蛋白B、低密度脂蛋白胆固醇、总脂固醇、甘油三酯和血栓素B_2的浓度均有不同程度的升高,而载脂蛋白A_1、高密度脂蛋白胆固醇和6-酮前列腺素F_(1α)的浓度则下降。同时糖代谢异常与脂代谢紊乱、糖代谢异常与前列腺素代谢物水平、以及脂代谢紊乱与前列腺素代谢物水平之间均无明显关系。推想糖尿病中促动脉粥样硬化的各种高危因素可能从不同的角度作用于血管壁,促进动脉粥样硬化的发生和发展。  相似文献   
110.
The technique of quantitative autoradiography was used to examine the effects of Huntington's disease (HD) and schizophrenia on the organization of striatal dopamine (DA) D1 and D2 receptors. Whereas the striatum of HD cases showed a reduction in the density of D1 ([3H]SCH 23390) and D2 ([3H]spiroperidol) receptors, the patterning of D2 receptor loss did not match that of the D1 receptor loss. The HD loss of D1 D1 receptors (65%) is far greater than the loss of D2 receptors (28%). Whereas there was a dorsal-ventral gradient of effect on both receptor subtypes, the effects of HD on D2 receptors in the ventral putamen (PUT) and nucleus accumben septi (NAS) were minimal. Similarly, muscarinic M1 and M2 receptors demonstrate different patterns of alteration in HD. The M2 subtype, labeled with [3H]N-methylscopolamine (in the presence of excess pirenzepine to occlude M1 sites), was depleted far more than the M1 receptor subtype, labeled with [3H]pirenzepine. Although the effects of HD on [3H]mazindol labeling of DA terminals were more heterogeneous, there appeared to be a relative preservation of this afferent input to the striatum of the HD cases. In the schizophrenic cases, our autoradiographic studies confirm previous reports of an elevation of D2 receptor density in the striata of many schizophrenics. This increase was evident even though two of the three cases were known to have not been treated with neuroleptics, and the third case may also have been drug naive. However, the increase was far greater in the NAS (164%) and ventral PUT (173%) than more dorsally in the striatum (68%). The density of D1 receptors and DA terminals labeled with [3H]mazindol in the striatum of schizophrenics was not significantly different from that of control cases. Thus in both HD and schizophrenia, the ratio of D2/D1 receptors is altered in favor of the D2 population, particularly in the NAS.  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