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   27820篇
  免费   2648篇
  国内免费   498篇
耳鼻咽喉   339篇
儿科学   815篇
妇产科学   529篇
基础医学   2084篇
口腔科学   722篇
临床医学   2849篇
内科学   2807篇
皮肤病学   394篇
神经病学   1581篇
特种医学   716篇
外国民族医学   15篇
外科学   3840篇
综合类   3086篇
现状与发展   3篇
预防医学   5028篇
眼科学   123篇
药学   1214篇
  36篇
中国医学   431篇
肿瘤学   4354篇
  2024年   64篇
  2023年   542篇
  2022年   867篇
  2021年   1397篇
  2020年   1286篇
  2019年   1196篇
  2018年   1118篇
  2017年   1112篇
  2016年   1093篇
  2015年   1063篇
  2014年   1824篇
  2013年   1968篇
  2012年   1606篇
  2011年   1824篇
  2010年   1387篇
  2009年   1483篇
  2008年   1526篇
  2007年   1489篇
  2006年   1179篇
  2005年   980篇
  2004年   859篇
  2003年   747篇
  2002年   610篇
  2001年   488篇
  2000年   422篇
  1999年   347篇
  1998年   328篇
  1997年   243篇
  1996年   197篇
  1995年   199篇
  1994年   172篇
  1993年   150篇
  1992年   138篇
  1991年   150篇
  1990年   99篇
  1989年   98篇
  1988年   91篇
  1987年   82篇
  1986年   68篇
  1985年   92篇
  1984年   69篇
  1983年   50篇
  1982年   59篇
  1981年   43篇
  1980年   33篇
  1979年   33篇
  1978年   27篇
  1977年   25篇
  1976年   18篇
  1972年   10篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
A comparison of 121 mature-age and 270 normal-age entrants who graduated from the University of Queensland Medical School between 1972 and 1987 shows that mature-age entrants are some 7 years older, are more likely to come from public (state) schools and less likely to have parents in professional/technical occupations. Otherwise, the two groups were similar in terms of gender, marital status, number of children, ethnic background and current practice location. The educational background of mature-age entrants prior to admission includes 44.6% with degrees in health-science areas and 31.4% with degrees in non-health areas. Reasons for delayed entry of mature-age entrants include late consideration of medicine as a career (34.7%), financial problems (31.4%), dissatisfaction with previous career (30.6%), poor academic results (19.8%), or a combination of the above factors. Motivations to study medicine include family influences (more so in normal-age entrants), altruistic reasons (more so in mature-age entrants) and a variety of personal/social factors such as intellectual satisfaction, prestige and financial security (similar for both groups) and parental expectations (more so in normal-age entrants). Mature-age entrants experienced greater stress throughout the medical course, especially with regard to financial difficulties, loneliness/isolation from the students and family problems (a greater proportion were married with children). While whole-course grades were similar in both groups, normal-age entrants tended to win more undergraduate honours/prizes and postgraduate diplomas/degrees, including specialist qualifications. Practice settings were similar in terms of group private practice, hospital/clinic practice or medical administration, but there was a greater proportion of mature-age entrants in solo private practice, and a smaller proportion in teaching/research. If given the time over, some two-thirds of both groups would choose medicine as a career. Reasons for job satisfaction include helping patients, intellectual stimulation and financial rewards. Reasons for dissatisfaction include pressure of work, red-tape/paperwork, 'doctor-bashing', long working hours, emotional strain, financial pressure, unfulfilled career expectations and irritation with trivial medical complaints.  相似文献   
62.
Concentrations of the vitamins B1, B2, B6, B12, C, folic acid,A, E and ß-carotene were determined in blood and 24-hdialysate in 44 CAPD patients. Twenty-five of these patientswere studied during chronic treatment (mean 313 days, range60–1034 days). Nineteen patients were studied during training.In a longitudinal study, 11 patients were analysed again after77–507 (mean 238) days. In both patient groups a considerable portion of patients (11%–64%)had blood concentrations indicative of a deficiency of the vitaminsB1, B6, C and folic acid. The average concentrations of thesevitamins were normal in both groups. The only abnormal findingwas the mean EGOT activity being deficient in patients on chronictreatment. Mean concentrations of vitamin A were above normalin both groups. In the longitudinal study a significant increaseof vitamin B2 and a decrease of vitamin B6 in blood was found. When compared to 24-h excretion in normal urine, loss with 24-hdialysate was low for vitamin B1, normal to relatively highfor vitamin B2 and B6, but extremely high for vitamin C andfolic acid. The vitamins B12, A, E and carotenoids were hardlydetectable in the dialysate. In ten other patients the effect of daily supplementation with2 mg vitamin B6, 100mg vitamin C and 400 µg folic acidwas analysed during a 16-week period. In all patients a significantincrease in blood concentrations was obtained. It is concludedthat these dosages were sufficient to maintain a normal statusof these vitamins in CAPD patients.  相似文献   
63.
There is little agreement about the methodology of clinical trials of antipsychotic drugs in patients with negative symptoms. A literature review revealed wide variation in experimental design, rating scales and study duration. This reflects differing views as to the definition and response to treatment of negative symptoms. Some degree of standardization would improve comparability of studies and aid the development of new compounds. Patients included in such studies should have displayed negative symptoms for at least 6 months. Depressive symptoms, positive schizophrenic symptoms and extrapyramidal signs may all influence or be confused with negative symptoms and may respond to treatment; they should be at a low level at baseline and should be measured during the study period. Studies should last at least 8 weeks. Several scales are available for measuring negative symptoms and are reviewed; a global impression score should be used additionally.  相似文献   
64.
陈坤  邹艳  王建跃  张立军 《营养学报》2003,25(3):239-244
目的 : 海岛学生饮食结构中含有碘丰富的海产品。本研究旨在了解海岛学生的碘营养状况 ,评价食盐补碘的利弊。方法 : 对定海农村 (食用碘盐 )和岱山农村 (不食用碘盐 )的学校中随机抽取的 1 2个班级 ,对碘盐组和非碘盐组的饮食碘摄入和尿碘水平等变量进行描述 ,并分别以尿碘和甲状腺肿率为应变量进行单因素和多因素回归分析。结果 : 碘盐组除碘盐外每日碘摄入量中位数为 1 84μg,而不食用加碘盐的组为 1 0 5 μg,两组饮食碘摄入有显著性差异 (u=4.71 0 ,P=0 .0 0 0 ) ,而尿碘水平在食用碘盐组和不食用碘盐组分别为 1 6 9μg/L和 1 2 9μg/L,两组间有显著性差异 (u=6 .3 0 2 ,P=0 .0 0 0 )。多因素分析中性别和是否食用碘盐对尿碘水平有显著性意义 (P<0 .0 5 ,OR值分别为 0 .76 5 ,1 .93 3 )。甲状腺肿学生和正常学生的饮食碘和尿碘无统计学差异 (P>0 .0 5 )。Poisson回归分析中性别和是否食用碘盐对甲状腺肿率有影响 (P<0 .0 5 ,OR值分别为2 .2 5 ,3 .5 2 )。结论 : 舟山海岛学生要注意补碘过程中可能出现的碘过量问题。  相似文献   
65.
The dietary history method was used to determine the total energy and macronutrient intake, the distribution of daily energy from the different meals and the energy contribution of various food groups, in a population of 299 boys, aged between 10 and 15 years. The effects of age, the social status of the father (SPS), the ponderal index, the importance of breakfast or lunch, and the level of energy intake on dietary indicators, were studied. In our population, energy intake increased with increasing age but the energy contribution of macronutrients did not vary. The diet of boys whose fathers were in the upper SPS classes differed from the diet of those boys whose fathers were manual workers: for example they consumed less energy and pastries, but more animal protein (in percentage of energy intake), more dairy products, and more fruit. The ponderal index was negatively related to energy intake but positively related to protein intake, especially from meat and meat products. The energy intake from protein, animal protein and the energy contribution of dairy products, meat and meat products, fish and vegetables was lower among large eaters than among small eaters. The energy contribution of pastries, sugar and sweets was higher among large eaters.
Similarily, the energy intake from morning and evening snacks was also higher among large eaters. It should be noted that boys who had a substantial breakfast took in less energy from all other meals (including snacks and main meals). Such informaton is necessary in order to develop an effective health programme.  相似文献   
66.
67.
BACKGROUND: In maintenance haemodialysis patients, daily food intake is changeable; however, its relationship with nutritional status is unexplored. This study aimed to evaluate the isolated, long-term effect of daily nutrient intake on nutritional status in haemodialysis patients. METHODS: We performed a prospective 1-year controlled study in 27 chronic haemodialysis patients, without recognized risk factors for malnutrition. Each day for 1 week, four times in the year, we measured protein nitrogen appearance, and assessed dietary protein (DPI) and energy (DEI) intake from dietary diaries. We compared the nutritional outcome of patients spontaneously reducing nutrient intake below the threshold of 0.8 g/kg body weight/day for DPI and 25 kcal/kg body weight/day for DEI during the week (LOW, n = 8), with controls at adequate nutrient intake (CON, n = 19). An interventional 6-month study was then carried out in LOW to verify the cause-effect relationship. RESULTS: All patients showed a day-by-day reduction of whole nutrient intake during interdialytic period, which was mostly relevant in the third interdialytic day (L3). During the 1-year study, even in the presence of adequate dialysis dose and normal inflammatory indexes, body weight (68.0 +/- 5.5 to 65.8 +/- 5.9 kg), serum albumin (3.96 +/- 0.07 to 3.66 +/- 0.06 g/dl) and creatinine (9.2 +/- 1.1 to 8.1 +/- 0.7 mg/dl) significantly decreased in LOW but not in CON. Diaries evidenced in LOW a reduced number of meals at L3 that was explained by the fear of excessive interdialytic weight gain. During the interventional study, daily DPI and DEI increased at L3; this was associated with a significant increment of body weight, and serum albumin and creatinine levels. CONCLUSIONS: In maintenance haemodialysis patients the persistent, marked reduction of daily nutrient intake, even if limited to a single day of the week, is an independent determinant of reversible impairment of nutritional status.  相似文献   
68.
目的 探讨对小儿难治性惊厥持续状态的有效治疗方法。方法 对14例小儿难治性惊厥持续状态采用硫喷妥钠治疗并观察疗效。结果 硫喷妥钠治疗有效率为100%,1例出现呼吸抑制,3例于停药后复发。结论 硫喷妥钠对小儿难治性惊厥持续状态有明显疗效,但易发生呼吸抑制。惊止后应维持一段时间,以免复发。  相似文献   
69.
目的探讨18^F-FDG PET/CT在检测非小细胞肺癌(NSCLC)区域淋巴结中出现假阴性和假阳性的因素。方法随机选择手术治疗的NSCLC患者48例,术前1周内行18^F—FDG PET/CT检查,同期行CT增强扫描,术后根据病理检查结果分析PET/CT诊断NSCLC区域淋巴结转移的假阴性与假阳性因素。结果48例患者共切除区域淋巴结313枚,转移淋巴结51枚,PET/CT结果7枚假阴性。8枚假阳性,阳性预测值和阴性预测值分别为85%,97%,高于CT(57%,94%;P=0.002,0.045)。3枚假阴性淋巴结内的癌灶较小;2枚淋巴结短径约为0.4mm,小于PET/CT的空间分辨率;2枚紧邻原发灶的淋巴结,图像无法区分而视为原发灶。8枚假阳性淋巴结为患者在原发病灶基础上并发不同程度的肺部疾病和淋巴结炎症,使其糖代谢率增高。结论假阳性出于(1)淋巴结的短径小于PET/CT的空间分辨率;(2)淋巴结内的小癌灶糖代谢率较低;(3)紧邻原发灶的淋巴结与原发灶无法区分。原发肿瘤合并肺部疾病是导致PET/CT出现假阳性的重要原因。  相似文献   
70.
逆转录-聚合酶链反应检测胃癌淋巴结微转移   总被引:1,自引:0,他引:1  
目的 检测胃癌常规病理检查阴性的淋巴结微转移的发生及与其它临床参考指标的关系。方法 利用逆转录-聚合酶链反应(RT-PCR)方法检测68枚胃癌胃周淋巴结癌胚抗原(CEA)mRNA基因表达,同时比较RT-PCR与免疫组化(IHC)方法的检测敏感性。结果 CEAmRNA RT-PCR是一种很敏感的方法,可以检测1/10^6个转移的癌细胞;检测19例胃癌患者取材的68枚胃周淋巴结,IHC阳性率28%(19/68),RT-PCR阳性率57%(39-68),两组之间差异有非常显著性意义(P<0.01);RT-PCR阳性率与胃部临床参考指标密切相关,且随着病期进展而增大。结论 CEA mRNA RT-PCR是比免疫组化更敏感的方法,可以预测胃癌淋巴结微转移,能够有效地避免已有微小转移的患者被漏诊。  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