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   1708篇
  免费   122篇
  国内免费   6篇
耳鼻咽喉   10篇
儿科学   92篇
妇产科学   61篇
基础医学   191篇
口腔科学   49篇
临床医学   229篇
内科学   288篇
皮肤病学   31篇
神经病学   66篇
特种医学   146篇
外科学   172篇
综合类   90篇
一般理论   4篇
预防医学   168篇
眼科学   24篇
药学   88篇
  1篇
中国医学   19篇
肿瘤学   107篇
  2022年   10篇
  2021年   38篇
  2020年   17篇
  2019年   31篇
  2018年   40篇
  2017年   27篇
  2016年   20篇
  2015年   52篇
  2014年   55篇
  2013年   58篇
  2012年   78篇
  2011年   89篇
  2010年   63篇
  2009年   54篇
  2008年   68篇
  2007年   77篇
  2006年   46篇
  2005年   44篇
  2004年   47篇
  2003年   53篇
  2002年   31篇
  2001年   30篇
  2000年   27篇
  1999年   22篇
  1998年   33篇
  1997年   29篇
  1996年   37篇
  1995年   30篇
  1994年   30篇
  1993年   23篇
  1992年   27篇
  1991年   39篇
  1990年   30篇
  1989年   39篇
  1988年   46篇
  1987年   33篇
  1986年   37篇
  1985年   29篇
  1984年   36篇
  1983年   31篇
  1982年   16篇
  1981年   15篇
  1980年   17篇
  1979年   23篇
  1978年   18篇
  1977年   15篇
  1976年   16篇
  1975年   14篇
  1974年   10篇
  1972年   15篇
排序方式: 共有1836条查询结果,搜索用时 31 毫秒
71.
Trisomy 14 mosaicism is a rare chromosomal defect with only 20 cases reported in the literature. We describe a child with trisomy 14 mosaicism who has some previously described and some novel phenotypic features. Trisomy 14 mosaicism was demonstrated in both blood lymphocytes and from skin fibroblasts, and with normal parents and siblings. This child had no evidence of neurodevelopmental delay at 6 years of age on formal testing, suggesting that mental retardation is not universal in this condition. This child did not demonstrate neurodevelopmental delay, which as been reported universally among children with trisomy 14 mosaicism.  相似文献   
72.
Global biodiversity in river and riparian ecosystems is generated and maintained by geographic variation in stream processes and fluvial disturbance regimes, which largely reflect regional differences in climate and geology. Extensive construction of dams by humans has greatly dampened the seasonal and interannual streamflow variability of rivers, thereby altering natural dynamics in ecologically important flows on continental to global scales. The cumulative effects of modification to regional-scale environmental templates caused by dams is largely unexplored but of critical conservation importance. Here, we use 186 long-term streamflow records on intermediate-sized rivers across the continental United States to show that dams have homogenized the flow regimes on third- through seventh-order rivers in 16 historically distinctive hydrologic regions over the course of the 20th century. This regional homogenization occurs chiefly through modification of the magnitude and timing of ecologically critical high and low flows. For 317 undammed reference rivers, no evidence for homogenization was found, despite documented changes in regional precipitation over this period. With an estimated average density of one dam every 48 km of third- through seventh-order river channel in the United States, dams arguably have a continental scale effect of homogenizing regionally distinct environmental templates, thereby creating conditions that favor the spread of cosmopolitan, nonindigenous species at the expense of locally adapted native biota. Quantitative analyses such as ours provide the basis for conservation and management actions aimed at restoring and maintaining native biodiversity and ecosystem function and resilience for regionally distinct ecosystems at continental to global scales.  相似文献   
73.
Blood donors reactive by enzyme-linked immunosorbent assay for antibody to the human immunodeficiency virus (HIV) who showed atypical patterns of viral core protein reactivity on Western blot were monitored for several months. Characterization of their antibodies was performed by 1) use of recombinant HIV proteins; 2) determination of cross-reactivity to HTLV-I, HTLV-II, and HTLV-IV: 3) assessment of immune status; and 4) identification of potentially interfering autoantibodies. Nineteen of 20 donors maintained the same HIV antibody reactivity throughout the follow-up period; the other donor became fully antibody-positive. Eighteen of 20 donors' sera showed clear reactivity with HIV recombinant core proteins. Ten of 19 donor samples demonstrated cross-reactivity to HTLV-IV; 3 of these 10 also cross-reacted with HTLV-I. The immune status of all donors was normal, although the medical histories and HLA antibody screens suggested possible autoimmune reactivity in 9 of 18 donors. During follow-up interviews, three donors reported possible risk factors for HIV infection that had not been acknowledged at the time of blood donation. We conclude that exclusion of donors with these atypical serologic test results is warranted while further studies to determine significance are being conducted.  相似文献   
74.
目的 探讨用改进的倒谱方法估计平均骨小梁间距(mean trabecular bone spacing,MTBS)的可行性.方法 提出了一种基于反向滤波器的改进的倒谱分析方法用于估计MTBS,并将该方法应用于仿真及离体牛胫骨松质骨中的实验信号.结果 改进的倒谱方法能有效减少超声换能器脉冲响应和组织散射特性对倒谱的干扰,而且实现简单,计算量小.结论 相比于传统的倒谱方法,改进的倒谱方法在估计MTBS时, 对弥散散射和噪声有更强的鲁棒性,因此估计MTBS的精度更高.  相似文献   
75.
目的探讨α-珠蛋白生成障碍性贫血产前诊断在降低出生缺陷中的效果。方法选择2003年1月至2012年7月进行α-珠蛋白生成障碍性贫血产前诊断的妊娠1 037例,采用聚合酶链反应结合琼脂糖凝胶电泳和反向点杂交技术对脐带血和原位培养后的羊水或绒毛组织检测α珠蛋白基因,同时对合并β-珠蛋白生成障碍贫血者进行β-珠蛋白基因检测。结果 1 037例妊娠中α-珠蛋白生成障碍性贫血检出率为79.27%,其中血红蛋白H(Hb Bart′s)胎儿水肿综合征292例,HbH病45例;同时检出中间型、重型β-珠蛋白生成障碍贫血5例,β-珠蛋白生成障碍贫血杂合子28例,包括α复合β-珠蛋白生成障碍贫血26例,终止妊娠339例。结论α-珠蛋白生成障碍性贫血产前干预是防止该类患儿出生的有效措施,同时应加强复合型珠蛋白生成障碍贫血的干预。  相似文献   
76.
目的分析自闭症儿童父母的心理状况,实施及时有效的健康教育。方法采用症状自评量表(SCL-90)、抑郁自评量表(SDS)、焦虑自评量表(SAS )对89例自闭症儿童父母进行测评。并对这些父母实施有效的健康教育,对健康教育前的测评结果分别同国内常模、健康教育后比较。结果在健康教育实施前,自闭症儿童父母SCL-90、SAS、SDS得分均高于全国常模,差异有统计学意义(P<0.01);健康教育前后得分比较差异有统计学意义(P<0.01)。结论自闭症儿童父母普遍存在心理问题,及时开展健康教育能改善其心理状况。  相似文献   
77.
寰椎椎弓根螺钉置钉技巧探讨   总被引:2,自引:0,他引:2  
[目的]探讨寰椎椎弓根螺钉固定治疗寰枢椎不稳的置钉技巧。[方法]总结2000年10月~2008年9月应用寰椎椎弓根螺钉技术治疗寰枢椎不稳患者66例,置钉132枚。术中在直视下依据手感行寰椎椎弓根螺钉置钉,复位固定。[结果]本组66例132枚螺钉均成功置入,复位固定满意。术中未发现脊髓、神经根、椎动脉等损伤。术后患者症状及神经脊髓功能均有不同程度恢复。96枚螺钉术后行CT检查,其中91枚位置良好(94.89%)。全部病例内固定无松动、断裂,植骨均融合。[结论]术前影像学测量,术中显露寰椎后弓、直视下依据手感置钉、X线确定进钉方向,是安全置钉的技巧。  相似文献   
78.
Context  Clinical studies of omega-3 polyunsaturated fatty acids (PUFAs) have shown a reduction in sudden cardiac death, suggesting that omega-3 PUFAs may have antiarrhythmic effects. Objective  To determine whether omega-3 PUFAs have beneficial antiarrhythmic effects in patients with a history of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Design and Setting  Randomized, double-blind, placebo-controlled trial performed at 6 US medical centers with enrollment from February 1999 until January 2003. Patients  Two hundred patients with an implantable cardioverter defibrillator (ICD) and a recent episode of sustained VT or VF. Intervention  Patients were randomly assigned to receive fish oil, 1.8 g/d, 72% omega-3 PUFAs, or placebo and were followed up for a median of 718 days (range, 20-828 days). Main Outcome Measures  Time to first episode of ICD treatment for VT/VF, changes in red blood cell concentrations of omega-3 PUFAs, frequency of recurrent VT/VF events, and predetermined subgroup analyses. Results  Patients randomized to receive fish oil had an increase in the mean percentage of omega-3 PUFAs in red blood cell membranes from 4.7% to 8.3% (P<.001), with no change observed in patients receiving placebo. At 6, 12, and 24 months, 46% (SE, 5%), 51% (5%), and 65% (5%) of patients randomized to receive fish oil had ICD therapy for VT/VF compared with 36% (5%), 41% (5%), and 59% (5%) for patients randomized to receive placebo (P = .19). In the subset of 133 patients whose qualifying arrhythmia was VT, 61% (SE, 6%), 66% (6%), and 79% (6%) of patients in the fish oil group had VT/VF at 6, 12, and 24 months compared with 37% (6%), 43% (6%), and 65% (6%) of patients in the control group (P = .007). Recurrent VT/VF events were more common in patients randomized to receive fish oil (P<.001). Conclusion  Among patients with a recent episode of sustained ventricular arrhythmia and an ICD, fish oil supplementation does not reduce the risk of VT/VF and may be proarrhythmic in some patients.   相似文献   
79.
目的:性治疗法目前尚未普及,本研究旨在评价性治疗法联合西地那非治疗勃起功能障碍(ED)的疗效。方法:根据治疗方法的不同将在本院治疗随访过的3130例维吾尔族ED患者分成2组。对照组625例,单纯口服西地那非3个月;试验组2505例,采用性治疗法联合西地那非治疗3个月。采用国际勃起功能问卷表(IIEF-5)在各组治疗前、后进行疗效评估,并随访12个月。结果:对照组治疗前、后及在6个月、12个月随访的IIEF-5评分分别为12.80±3.76、18.10±2.61、17.35±2.73和16.64±2.63;试验组治疗前、后及在6个月、12个月随访的IIEF-5评分分别为12.73±3.52、19.06±4.07、19.86±2.42和20.47±2.38。两组治疗前后IIEF-5评分自身对比差异均有显著性(P<0.05)。组间比较,试验组较对照组6个月和12个月随访IIEF-5评分均有显著性差异(P<0.05)。结论:性治疗法联合西地那非治疗ED的效果优于单纯西地那非治疗,并在12个月的随访中稳定性良好。  相似文献   
80.
Sensitive skin syndrome was first described in 1977; however, no robust study has been carried out to evaluate its prevalence in Japan. A national representative sample of the Japanese population over the age of 18 years was taken. Individuals were questioned by telephone and selected according to the quota method. When asked “Do you have a sensitive skin?”, 52.84% of men and 55.98% of women answered “rather sensitive” or “very sensitive”. There was no significant difference (P = 0.22) between the two sexes. The non‐response rate among respondents was zero, suggesting that the term “sensitive skin” held a meaning for the majority of the population. Concerning questions about the onset of a rash, tingling or irritation in the presence of various factors, such as emotional issues, cold, heat, sun, dry air, air‐conditioning, water, air pollution and temperature variations, respondents with rather sensitive or very sensitive skin responded “yes” more often than others: approximately three‐times more often for water (18.97%/6.15%), air pollution (39.29%/12.45%) and warm climatic conditions (29.74%/9.8%). To our knowledge, this epidemiological study is the first to focus on sensitive skin among Japanese people of this century. It is of particular interest for two reasons: (i) it was conducted on a representative sample of the Japanese population; and (ii) the methodology used was identical to that used for sensitive skin assessment studies conducted in Europe and the USA, making it possible to draw certain comparisons.  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