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   64678篇
  免费   5095篇
  国内免费   2613篇
耳鼻咽喉   861篇
儿科学   897篇
妇产科学   1035篇
基础医学   8602篇
口腔科学   1410篇
临床医学   6993篇
内科学   11164篇
皮肤病学   1130篇
神经病学   4094篇
特种医学   3239篇
外国民族医学   18篇
外科学   8156篇
综合类   5452篇
现状与发展   7篇
一般理论   16篇
预防医学   3845篇
眼科学   1746篇
药学   6251篇
  21篇
中国医学   2179篇
肿瘤学   5270篇
  2024年   118篇
  2023年   694篇
  2022年   1836篇
  2021年   2590篇
  2020年   1748篇
  2019年   1933篇
  2018年   2046篇
  2017年   1847篇
  2016年   1962篇
  2015年   2729篇
  2014年   3447篇
  2013年   3531篇
  2012年   5247篇
  2011年   5241篇
  2010年   3177篇
  2009年   2709篇
  2008年   3715篇
  2007年   3509篇
  2006年   3292篇
  2005年   3136篇
  2004年   2561篇
  2003年   2339篇
  2002年   2009篇
  2001年   1605篇
  2000年   1501篇
  1999年   1338篇
  1998年   682篇
  1997年   609篇
  1996年   487篇
  1995年   467篇
  1994年   393篇
  1993年   304篇
  1992年   474篇
  1991年   408篇
  1990年   335篇
  1989年   331篇
  1988年   304篇
  1987年   229篇
  1986年   201篇
  1985年   156篇
  1984年   123篇
  1983年   112篇
  1982年   73篇
  1981年   73篇
  1980年   68篇
  1979年   88篇
  1978年   62篇
  1977年   58篇
  1972年   54篇
  1971年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
目的 :观察天然碱性脂 (Stearylamine,SA)脂质体介导绿色荧光蛋白 /碱性成纤维细胞生长因子(GFP/bFGF)基因于不同时间段豚鼠耳蜗中的表达 ,为进一步研究耳聋的基因治疗提供实验基础。方法 :取豚鼠 1 6只 ,分成 4组 ,每组 4只。其中 3只右耳圆窗内注入SA -GFP/bFGF复合物 ,1只同法注入生理盐水作为对照。分别于术后第 2、7、1 4、2 1天取材。在荧光显微镜下观察GFP的表达 ,用免疫组化法检测bFGF的转导情况。结果 :荧光显微镜下见双侧耳蜗于术后第 2天开始部分细胞发出绿色荧光 ,第 7天达到高峰 ,支持细胞及内外毛细胞均显荧光 ,细胞轮廓清晰 ;第 1 4天开始减弱 ,第 2 1天消失。免疫组化染色显示 ,除血管纹外 ,耳蜗各回Corti器、螺旋韧带、螺旋缘及螺旋神经节细胞均有高浓度的表达产物 ,对照动物呈阴性表达。结论 :SA脂质体介导的GFP/bFGF基因单耳给药双侧耳蜗均有高效表达 ,为进一步研究基因治疗耳聋提供了可能。  相似文献   
32.
OBJECTIVES: The aim was to assess the natural course of oral lichen lesions (OLL) among unselected, non-consulting individuals. SUBJECTS AND METHODS: A cohort of 327 subjects with OLL, confirmed in 1973-1974 during a population-based survey in two Swedish municipalities, was followed through January 2002 via record linkages with nationwide and essentially complete registers. A sample of 80 drawn from the 194 surviving subjects who still resided in the area in 1993-1995 was invited for interview and oral re-examination. RESULTS: At the end of follow-up, one case of oral cancer was detected, while 0.4 were expected. The overall mortality among subjects with OLL was not significantly different from that in the 15,817 OLL-free subjects who participated in the initial population based survey in 1973-1974. The lesion had disappeared in 14 (39%) of 36 re-examined subjects with white OLLs in 1973-1974, and four (11%) had transformed into red types. In the corresponding group of 19 with red forms initially, five (26%) had become lesion free and four (21%) had switched to white types. Although the cohort size does not permit firm conclusions regarding oral cancer risk, the natural course over up to 30 years appears to be benign in the great majority.  相似文献   
33.
Background/aims: The objective and quantitative assessment of the skin is important in medical and cosmeceutical research. Assessment of color is an important element for analyzing the surface of the skin, which is usually determined subjectively by a doctor or using color analysis devices. These devices, however, cannot provide correct color information because color is construed from the mean value of the observation region, and analysis of color distribution is impossible. The purpose of this paper is to develop an objective analysis method to permit skin color measurement of each pixel unit of an image and analyze the distribution of skin surface color. Methods: The Skin Color Distribution Analyzer (SCDA) is an analysis method newly developed at the Research Institute for Skin Image at Korea University. The SCDA system presented in this paper performed a novel form of quantitative and objective analysis of skin color distribution using each pixel color model parameter found in image wavelength information. In this paper, distribution analysis was conducted on normal skin and skin lesions and skin affected by artificially induced irritant contact dermatitis and pigmented nevous. The method selected a grade using a color model parameter. Twenty healthy Korean males participated in this study. A comparative study of the eight anatomical areas was performed, including the exposure and non‐exposure parts and the medial aspect and the lateral aspect of the forearm. A reliability test for the SCDA system was also conducted with a spectrometer (SPEC) using the color analysis method. Results: Each skin lesion was precisely segmented by grade and each parameter hada different statistical significance for results of analysis of distribution in pigmented nevous and the artificially induced irritant contact dermatitis. Parameters L*, b*, a*, and EI showed salient traits. Showed resemble measured result in the SCDA system and the SPEC of normal skin. The exposed site, in comparison with the non‐exposed site, showed a notable difference in the L* parameter and a significant statistical difference in the x and z parameters, except b*. The comparison of the medial and lateral aspects of the forearm showed a notable difference in the L* parameter and a significant statistical difference in the parameters except y and b*. In the reliability test result using the SCDA system and the SPEC, the SCDA system was highly reliabile in terms of the CV value in all color model parameters. Conclusions: The color distribution analysis method using the SCDA system has revealed an aspect that the existent method of medical research has not shown, and is considered to be more reliable than other methods. This method can provide better study findings because it can be applied to other fields in addition to the medical science field and the ripple effect is thought to be bigger in other science field too.  相似文献   
34.
以曼氏血吸虫的虫卵和成虫免疫家兔后所产生的特异性抗体,可用以日本血吸虫虫卵、尾蚴和成虫为抗原分别进行的COP,CHR和ELACIEP测出,表明两种人体血吸虫存有显著的交叉抗原成分。应用此种血清交叉反应性,以检测抗异种人体血吸虫的抗体,似有效而可取的,可用以辅助诊断援外回国人员是否感染国外人体血吸虫病。  相似文献   
35.
36.
目的研究高原地区,脱髓鞘疾病与中老年人疾病等因素的关系。方法对我院所有接受过磁共振头部扫描的病人进行评估,确诊出40位脱髓鞘疾病患者,并对大脑7个部位的脱髓鞘疾病按严重性分4级打分,统计临床数据,最后运用统计学方法分析其相关性。结果在40例患者中,出现在大脑半球、放射冠、半卵圆中心和脑室前后角的脑白质损伤频率最多,分别占总量的50%、67.5%、77.5%和87.5%。脑白质损伤患者的平均年龄为47.1岁,这比世界其他地区都有明显的提前。男性患者将近是女性患者的3倍(29∶11)。年龄、慢性高原红细胞增多症、收缩压、脑梗塞与脑白质损伤正相关(P<0.05)。结论对于高海拔地区,有效控制高原心血管疾病的发生对于减少颅脑脱髓鞘疾病的发生具有重要意义。  相似文献   
37.
38.
This study evaluated the safety and efficacy of batroxobin in treating hyperfibrinogenemia for secondary stroke prevention. Patients with ischemic stroke or transient ischemic attack (TIA) were measured for plasma fibrinogen levels. Selected participants had concomitant hyperfibrinogenemia (plasma fibrinogen > or = 3.0 g/l). Patients enrolled between 1 July 2003 and 31 December 2004 were treated with batroxobin; patients enrolled between 1 January 2002 and 30 June 2003 were treated without batroxobin. Batroxobin was administered intermittently via intravenous injection at 3-monthly intervals. Patients in both groups were followed for 1 year. Any cerebrovascular events and suspected adverse events were recorded. In total, 112 ischemic stroke/TIA patients with concomitant hyperfibrinogenemia were enrolled, 52 being treated with batroxobin and 60 without batroxobin. Six patients (11.5%) with batroxobin and 16 patients (26.7%) without batroxobin had recurrent cerebral ischemic events during follow-up. Stroke/TIA recurrence in patients without batroxobin was higher than that in patients with batroxobin (P < 0.05). Two patients with batroxobin and two patients without batroxobin developed hemorrhagic stroke during follow-up. There were five deaths (9.6%) in the batroxobin group, and seven deaths (11.7%) in the nonbatroxobin group during follow-up (P > 0.05). Intermittent intravenous injection of batroxobin can efficiently reduce the risk for stroke/TIA recurrence in patients with concomitant hyperfibrinogenemia.  相似文献   
39.
BACKGROUND: Dialysis patient mortality remains high, and this high mortality may be due to many factors. In peritoneal dialysis (PD) patients, old age, co-morbid diseases, malnutrition, low residual renal function (RRF) and a high peritoneal transport rate have been shown to influence survival, but the relative importance of these factors may differ between different patient populations. Besides, centre practice patterns may differ between centres and may influence patient survival. In addition, the literature suggests that dialysis patient survival may be better in Asian than in Caucasian patients. METHODS: The influence of centre and patient characteristics on patient survival was investigated in 132 Korean and 106 Swedish incident PD patients, who underwent initial biochemical measurements and assessment of adequacy of dialysis, nutritional status, RRF and peritoneal transport characteristics. RESULTS: At the start of PD, Korean patients had a higher prevalence of diabetes, peritoneal Kt/V(urea), peritoneal creatinine clearance and peritoneal fluid removal, and lower body mass index, RRF and dialysate to plasma creatinine concentration ratio (D/P Cr) compared with Swedish patients. Significantly more patients from Korea were placed on temporary haemodialysis before PD (100 out of 132) when compared with Swedish patients (21 out of 106). During the follow-up, there was a significantly higher rate of transfer to other units in Korea and a significantly higher rate of kidney transplantation in Sweden. On Kaplan-Meier analysis, overall patient survival did not differ and relative risk for death was also not different between the two centres even after adjustment for age, diabetes, cardiovascular disease, RRF and D/P Cr. On Cox proportional hazards multivariate analysis, age, diabetes, RRF and D/P Cr were found to be independent predictors of mortality in the combined cohort of patients. While age, diabetes and D/P Cr were independent predictors of mortality in Korean patients, age and RRF independently predicted mortality in Swedish patients. CONCLUSION: Although there were significant differences in centre and patient characteristics, we were unable to confirm a survival advantage for Korean over Swedish PD patients. The results of this study suggest that the reported difference in survival between Asian and Caucasian dialysis patients may have been due, in part, to differences in centre and patient characteristics rather than to race as such. The genetic influence on patient characteristics remains, however, to be elucidated.  相似文献   
40.
In this work the feasibility of separating fat and water signals using the balanced steady-state free precession (SSFP) technique is demonstrated. The technique is based on the observation (Scheffler and Hennig, Magnetic Resonance in Medicine 2003;49:395-397) that at the nominal values of TE = TR/2 in SSFP imaging, phase coherence can be achieved at essentially only two orientations (0 degrees and 180 degrees ) relative to the RF pulses in the rotating frame, under the assumption of TR < T2, and independently of the SSFP angle. This property allows in-phase and out-of-phase SSFP images to be obtained by proper choices of the center frequency offset, and thus allows the Dixon subtraction method to be utilized for effective fat-water separation. The TR and frequency offset for optimal fat-water separation are derived from theories. Experimental results from healthy subjects, using a 3.0 Tesla system, show that nearly complete fat suppression can be accomplished.  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