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   387800篇
  免费   25886篇
  国内免费   7717篇
耳鼻咽喉   4104篇
儿科学   9646篇
妇产科学   6735篇
基础医学   28441篇
口腔科学   8092篇
临床医学   68754篇
内科学   44012篇
皮肤病学   4650篇
神经病学   19999篇
特种医学   8318篇
外国民族医学   34篇
外科学   38876篇
综合类   56218篇
现状与发展   12篇
一般理论   31篇
预防医学   39030篇
眼科学   5354篇
药学   32267篇
  693篇
中国医学   32208篇
肿瘤学   13929篇
  2024年   1341篇
  2023年   6580篇
  2022年   10941篇
  2021年   15108篇
  2020年   14855篇
  2019年   19827篇
  2018年   17077篇
  2017年   14611篇
  2016年   12509篇
  2015年   11596篇
  2014年   23972篇
  2013年   24621篇
  2012年   21758篇
  2011年   23267篇
  2010年   18734篇
  2009年   17244篇
  2008年   16444篇
  2007年   17005篇
  2006年   14798篇
  2005年   12864篇
  2004年   10314篇
  2003年   8813篇
  2002年   6898篇
  2001年   6224篇
  2000年   5135篇
  1999年   4430篇
  1998年   3584篇
  1997年   3361篇
  1996年   2846篇
  1995年   2676篇
  1994年   2567篇
  1993年   2049篇
  1992年   2080篇
  1991年   1771篇
  1990年   1586篇
  1989年   1395篇
  1988年   1328篇
  1985年   3800篇
  1984年   4807篇
  1983年   3346篇
  1982年   3809篇
  1981年   3554篇
  1980年   3164篇
  1979年   2909篇
  1978年   2538篇
  1977年   1909篇
  1976年   2150篇
  1975年   1632篇
  1974年   1429篇
  1973年   1278篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
The purpose of this study was to assess the degree of consistency in student ratings of teacher effectiveness during the first year of medical school. Student ratings of teaching effectiveness represent a commonly used source of information that enters into the academic decision-making process. In medical school, student evaluations often represent a major source of information that is used in promotion and tenure decisions. It is essential that the precision of such ratings be ascertained so that decision-makers will know how much confidence to place in this source of information on teaching effectiveness. In this study, each member of a first-year medical school class was randomly assigned a two-digit identification number at the beginning of the spring semester, 1986. As the semester progressed students were asked to evaluate each full-time teacher in three major courses. Multiple instructors were utilized in each course (n = 10). Each teacher was evaluated immediately after lectures during the first (T1) and second (T2) halves of the course. Students evaluated the teacher a third time (T3) as part of the end-of-semester overall course evaluation. The teachers were evaluated on a short eight-item Likert-type scale that identified several key indicators of effective teaching. Students attached their anonymous identification numbers to individual ratings so that their responses could be matched in the analysis. The results indicate that medical students are only moderately consistent in the extent to which they evaluate teachers. This inconsistency varied by course and by instructors within courses.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
62.
63.
Abstract The aim of this study was to describe the periodontal conditions in 372 35–44-yr-old and 537 noninstitutionalized 65–74-yr-old Hong Kong Chinese who were examined clinically for loss of attachment, recession, probing depth, calculus, and bleeding after probing. Community Periodontal Index (CPI) data and treatment need indications were compiled from index teeth or their substitutes. The prevalence of loss of attachment varied considerably in both cohorts according to the definition of the threshold (≥6, ≥9, and ≥12 mm, respectively). The mean numbers of teeth with loss of attachment at the ≥6-mm threshold and at higher thresholds were small. In both age cohorts, about one-fifth of subjects had probing depths ≥6-mm, while al the ≥9-mm threshold only 2–3% were so affected. Although recession was an important component of loss of attachment in the younger cohort, in the older cohort the prevalence and extent of recession were greater than for probing depths at thresholds ≥4 mm. All subjects had one or more teeth with calculus, bleeding, or both, most teeth being so affected. Eighty-four of the 537 65–74-yr-old subjects were excluded either because of edentulousness or because extractions indicated for the remaining teeth would have rendered the subjects edentulous. The distribution of subjects according to their highest CPI score was remarkably similar for the two cohorts. No subjects in either age group were assessed as “healthy” (CPI code 0) or had “bleeding only” (code 1) as their highest score. While most subjects scored CPI code 2 or 3 us their highest score, only 17% of the younger and 15% of the older cohort scored Community Periodontal Index of Treatment Needs (CPITN) code 4. Differences in the mean number of sextants affected by CPI codes between the two cohorts were mainly due to a greater number of excluded sextants in the older cohort. CPI findings for 35–44-yr-olds differed little from those reported in 1984.  相似文献   
64.
The morphological types of ganglion cells in the dog and wolf retina were studied by intracellular staining with Lucifer Yellow. These retinae contain a range of ganglion cell types that closely correspond to those found in cat retina: alpha cells with large somata and large, relatively densely branched dendritic trees; beta cells with medium-sized somata and small, densely branched dendritic trees; and a variety of other types with smaller somata and varying dendritic branching patterns and dendritic field sizes. The correspondence of canine and cat ganglion cell types strengthens the view that there is a common set of ganglion cell types in carnivores. Alpha and beta cell dendritic trees of dog and wolf are monostratified in either the inner or the outer part of the inner plexiform layer, suggesting an on/off dichotomy in the response to light. Dendritic field sizes of dog alpha and beta cells increase from the central area to peripheral retina: alpha cell fields from 160-200 microns to about 1,100 microns diameter, and beta cell fields from 25 microns to about 360 microns diameter. These sizes are quantitatively very similar to those found in cat retina. The close qualitative and quantitative morphological correspondence of cat and dog ganglion cells suggests that they are also functionally very similar. It is likely that dog alpha cells have brisk-transient (Y), and dog beta cells brisk-sustained (X) concentric receptive fields. From the smallest beta cell sizes it is concluded that the visual acuity of the dog may be as good as that of the cat.  相似文献   
65.
整体护理改善护患关系的体会   总被引:2,自引:2,他引:0  
孟广霞 《天津护理》1998,6(4):160-161
整体护理的实施,重塑了护士的职业价值观,增加了护患之间的接触。护士能够在自己的专业范围内积极主动地解决病人的问题,挖掘了护理人员的自身潜力,加深了护患交流,使护患关系明显改善。  相似文献   
66.
Research on children's early writing development in the past has focused primarily on product and process. In reviewing the more recent research on early writing development, however, a new focus of context emerges. Occurrences of literacy are now being observed in the home, the school, and the community. With this new emphasis, comes the task of defining context. A definition of context reflects theoretical perspectives, areas of research interests, and types of methodologies employed in conducting research. Therefore, the purpose of this article is to address the following aspects of context: #op1#cp multidiscipline perspectives and definitions of context, #op2#cp contextual shifts observed between the home and the school, #op3#cp contextual factors present when learning how to write, and #op4#cp pedagogical implications for curriculum development.  相似文献   
67.
The axolemma membrane forms a stable and reproducible monomolecular layer at the air-aqueous interface. The major lipids and proteins are present in this monolayer in molar ratios similar to the original membrane. Acetylcholinesterase and Na-K-ATPase activities are preserved in the monolayer to levels of 64% and 25%, respectively. The total lipid fraction forms a homogeneously mixed phase. The presence of proteins in the monolayer introduces surface inhomogeneties. Among other features, this is revealed by the presence of two values of lateral pressure at which the monolayer shows partial or total collapse: a broad partial collapse at surface pressures between 13 to 30 mN/m and a sharp collapse point at 46 mN/m. The average molecular areas, the broad collapse point, and the variation of the surface potential per molecule suggest the relocation of protein components at surface pressures between 13 to 30 mN/m. The behavior is consistent with the extrusion and exposure of proteins toward the aqueous medium that depends on the lateral pressure. Schwann cells grown on coverslips coated with axolemma monolayers at 13 mN/m (beginning of the broad collapse) and 34 mN/m (above the broad collapse) recognize the difference in the surface organization of axolemma caused by the lateral pressure which affects their proliferation, morphology, and spatial pattern of organization. Our results show for the first time that response of Schwann cells depends on the intermolecular organization of the axolemma surface with which they interact. These results suggest that the local expression of putative surface molecules of axolemma that may mediate membrane recognition and the signalling of morphological and proliferative changes can be modulated by long range supramolecular properties. © 1993 Wiley-Liss, Inc.  相似文献   
68.
重组人红细胞生成素治疗肾性贫血的临床分析   总被引:1,自引:0,他引:1  
目的 观察重组人红细胞生成素 (RhEPO)对肾性贫血的治疗作用。方法 根据使用EPO剂量的不同将 39例慢性肾衰竭并血液透析病人分成 4组 ,观察治疗后 2、4、12个月时与治疗前 (0月 )相比红细胞数 (RBC)、红细胞比积 (Hct)及血红蛋白含量 (Hb)的变化。结果  2 4例使用EPO10 0 - 15 0IU/ (kg·w) (6 0 0 0IU/w - 90 0 0IU/w) ,治疗后RBC、Hct、Hb较治疗前有显著升高 (P≤ 0 .0 0 1) ;5例使用EPO5 0IU/ (kg·w) (30 0 0IU/w) +间断输血患者 ,其RBC、Hct、Hb升高不显著 ;10例不用EPO而单纯输血患者 ,其RBC、Hct、Hb无明显变化 (P >0 .0 5 )。结论 EPO能较好地纠正肾性贫血 ;单纯输血不能治疗肾性贫血  相似文献   
69.
目的:探讨铲状电极经尿道前列腺电汽化切割术中的手术经验及疗效。方法:总结了120例经尿道前列腺电汽化切割手术的治疗资料。结果:术后随访1月~2年,120倒手术患者118例治愈,2例于术后出现急性肾衰,经保守对症治疗痊愈,2例出现压力性尿失禁,经对症治疗好转。结论:铲状电极行前列腺组织的汽化切割,优于滚轮汽化电极或电极弧,术中术后出血少,术中术野清晰,安全可靠。  相似文献   
70.
Ciclesonide is an onsite-activated inhaled corticosteroid (ICS) for the treatment of asthma. This study compared the efficacy, safety and effect on quality of life (QOL) of ciclesonide 160 microg (ex-actuator; nominal dose 200 microg) vs. budesonide 400 microg (nominal dose) in children with asthma. Six hundred and twenty-one children (aged 6-11 yr) with asthma were randomized to receive ciclesonide 160 microg (ex-actuator) once daily (via hydrofluoroalkane metered-dose inhaler and AeroChamber Plus spacer) or budesonide 400 microg once daily (via Turbohaler) both given in the evening for 12 wk. The primary efficacy end-point was change in forced expiratory volume in 1 s (FEV1). Additional measurements included change in daily peak expiratory flow (PEF), change in asthma symptom score sum, change in use of rescue medication, paediatric and caregiver asthma QOL questionnaire [PAQLQ(S) and PACQLQ, respectively] scores, change in body height assessed by stadiometry, change in 24-h urinary cortisol adjusted for creatinine and adverse events. Both ciclesonide and budesonide increased FEV1, morning PEF and PAQLQ(S) and PACQLQ scores, and improved asthma symptom score sums and the need for rescue medication after 12 wk vs. baseline. The non-inferiority of ciclesonide vs. budesonide was demonstrated for the change in FEV1 (95% confidence interval: -75, 10 ml, p = 0.0009, one-sided non-inferiority, per-protocol). In addition, ciclesonide and budesonide showed similar efficacy in improving asthma symptoms, morning PEF, use of rescue medication and QOL. Ciclesonide was superior to budesonide with regard to increases in body height (p = 0.003, two-sided). The effect on the hypothalamic-pituitary-adrenal axis was significantly different in favor of ciclesonide treatment (p < 0.001, one-sided). Both ciclesonide and budesonide were well tolerated. Ciclesonide 160 microg once daily and budesonide 400 microg once daily were effective in children with asthma. In addition, in children treated with ciclesonide there was significantly less reduction in body height and suppression of 24-h urinary cortisol excretion compared with children treated with budesonide after 12 wk.  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