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   31015篇
  免费   2328篇
  国内免费   573篇
耳鼻咽喉   3024篇
儿科学   1772篇
妇产科学   1508篇
基础医学   2849篇
口腔科学   2114篇
临床医学   2222篇
内科学   3251篇
皮肤病学   668篇
神经病学   1645篇
特种医学   536篇
外科学   3164篇
综合类   2480篇
现状与发展   2篇
一般理论   3篇
预防医学   4442篇
眼科学   534篇
药学   2216篇
  12篇
中国医学   573篇
肿瘤学   901篇
  2024年   95篇
  2023年   631篇
  2022年   1126篇
  2021年   1440篇
  2020年   1268篇
  2019年   1401篇
  2018年   1236篇
  2017年   1254篇
  2016年   1235篇
  2015年   1204篇
  2014年   1979篇
  2013年   2613篇
  2012年   1550篇
  2011年   1704篇
  2010年   1353篇
  2009年   1378篇
  2008年   1427篇
  2007年   1320篇
  2006年   1136篇
  2005年   1012篇
  2004年   870篇
  2003年   789篇
  2002年   637篇
  2001年   590篇
  2000年   487篇
  1999年   392篇
  1998年   358篇
  1997年   315篇
  1996年   264篇
  1995年   262篇
  1994年   234篇
  1993年   196篇
  1992年   196篇
  1991年   170篇
  1990年   151篇
  1989年   137篇
  1988年   134篇
  1987年   100篇
  1986年   103篇
  1985年   181篇
  1984年   164篇
  1983年   129篇
  1982年   122篇
  1981年   97篇
  1980年   102篇
  1979年   89篇
  1978年   67篇
  1977年   48篇
  1976年   49篇
  1975年   36篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Early catch-up growth and subsequent overweight are suggested to be associated with later cardiovascular diseases and later type II diabetes. However, the impact of early catch-up growth and childhood overweight on the development of asthma has been less studied, particularly in children born with very low birth weight (VLBW). A birth cohort of 74 VLBW children (birth weight < or = 1500 g) was followed from birth and investigated on asthma at 12 yr of age. Early rapid weight gain was in one way defined as an increase of weight > or =1 standard deviation score (SDS) at 6 months of corrected postnatal age. Current overweight was defined by body mass index (BMI) exceeding 21.2 and 21.7 kg/m(2), respectively, for boys and girls at 12 yr of age. Current asthma was diagnosed by a pediatrician, according to asthma ever in combination with a positive response to hypertonic saline bronchial provocation test and/or wheeze at physical examination at 12 yr old. Being overweight at 12 yr of age was associated with an increased risk for current asthma in the VLBW children [crude odds ratio (OR): 5.5, 95% confidence interval (CI): 1.3-22.2]. After adjustment for early weight gain and neonatal risk, the OR of overweight increased nearly three times (adjusted OR: 15.3, 95% CI: 2.5-90.6). Early rapid weight gain seemed to be inversely associated with current asthma (adjusted OR: 0.49 for an increase of weight equal to 1 SDS, 95% CI: 0.23-1.02, p = 0.06). In addition, early rapid weight gain was inversely associated with the magnitude of bronchial responsiveness at 12 yr (coefficient -1.15, p < 0.01). There was a strong and positive association between overweight and asthma at 12 yr of age in the VLBW children. This strong association had been reduced by early rapid weight gain, possibly via the reduction of bronchial responsiveness.  相似文献   
12.
目的 探讨抗精神病药(APD)引起患者体质量增加及其相关因素。方法 对6 7例首次住院单用APD治疗的精神分裂症患者进行住院及出院后4个月的随访评估。结果 各时点体质量增加与GI评分无相关性,在出院时与BPRS、SAPS减分值有相关性,而随访期与SANS减分值有相关意义。逐步回归分析显示,在α=0 .0 5水平上,进入回归方程的因素依次为:APD品种,最大服药剂量与服药时间的积,阴性症状,病前1a最佳功能水平。结论 APD治疗中的体质量增加是与疗效无关的药物不良反应,受药物、精神症状及综合社会心理因素等方面的影响,而饮食与活动的中介作用不应低估。控制体质量增加有重要的医学及社会意义。  相似文献   
13.
Digital volume tomography (DVT) is an extension of panoramic tomography. With this diagnostic technique, characterized by high resolution, a narrow section width (0.125 mm) and three-dimensional display, small pathological processes can be well visualized. Twenty-five patients with the history of a progressive hearing loss were examined with DVT (Accu-I-tomo, Morita, Japan). The results were compared with pre- and intraoperative findings to evaluate the diagnostic value of DVT in cases of erosion of the ossicular chain. With high resolution and artifact-free demonstration of the middle ear and the ossicular chain, it was possible to define its continuity preoperatively by DVT in all 25 cases. An intact ossicular chain was found by DVT in 13 cases and was later confirmed by surgery. The predicted erosion of the ossicles was verified in 12 patients, and a tympanoplasty type III was performed. Digital volume tomography is an excellent technique to examine the middle ear cleft and inner ear, and expands the application of diagnostic possibilities in the lateral skull base. Therefore, improvement in preoperative diagnosis is achieved along with more accurate planning of the surgical procedure. Digital volume tomography delivers a small radiation dose with a high resolution and a low purchase price for the equipment.  相似文献   
14.
Serum and red blood cell folate in depression   总被引:2,自引:0,他引:2  
Serum folate concentrations were estimated in patients with major depressive disorders, lithium-treated patients, detoxified alcoholic patients and normal controls. Red blood cell (RBC) folate concentrations were also estimated in subgroups of patients with major depressive disorder and normal controls. Results showed significantly lower serum and RBC folate concentrations in patients with major depressive disorder than in normal controls. Lower serum folate concentrations were associated with greater severity of depression. There was no association between serum and RBC folate concentrations and endogenicity of depression or the presence of weight loss.  相似文献   
15.
OBJECTIVE: In the present study, we evaluated the anti-inflammatory activity of Poria cocos (PoCo) on experimentally induced irritant contact dermatitis (ICD) in a repeated sodium lauryl sulphate (SLS) irritation model. METHODS: The anti-irritative effect of PoCo was evaluated with a visual score and quantified by non-invasive bioengineering methods, namely chromametry and transepidermal water loss. Three concentrations of PoCo in base cream DAC (amphiphilic emollient; German pharmacopoeia) were tested in a 4-day repetitive irritation test using SLS. RESULTS: A statistically significant anti-inflammatory activity was observed for PoCo by all three methods when applied in parallel to the induction period of ICD. Application of PoCo after induction of ICD once a day for 5 days, starting just at the end of 4 days, was without any effect. CONCLUSION: An anti-inflammatory efficacy of PoCo on the elicitation phase of the ICD induced by repeated SLS test could be observed and quantified by three independent, non-invasive biophysical assessment parameters. This effect can be explained by its influence on pro-inflammatory enzymes, namely phospholipase A2.  相似文献   
16.
M. Sivak 《Obesity reviews》2006,7(3):295-296
Caloric consumption in a society with readily available food is likely to be approximately proportional to the number of hours of being awake. Thus, replacing 1 h of inactive wakefulness (e.g. watching TV), with sleeping is likely to result in a substantial reduction in caloric intake. Calculations are presented to illustrate the possible benefits of such a switch on weight reduction.  相似文献   
17.
BACKGROUND: The complaint of chronic hair loss frequently affects female subjects and there is little or no objective technology available in the general dermatology or even in the hair clinics to guide the observer in the management of the patient. The purpose of this report is to share the results of refined hair growth measurements that were collected in 92 female subjects complaining about hair loss. METHODS: Clinically they were classified as having a patterned hair loss according to Ludwig (L; n=50), diffuse hair loss (D; n=13) or no visible hair loss but complaining of hair shedding (N; n=29). Two scalp sites on the top of the head and one occipital site were investigated after clipping by close-up photography before and after a hair dye (contrast enhancement, CE). Forty-eight hours later a new photograph was taken after CE in view of phototrichogram analysis (CE-PTG). Finally a last hair clip was performed 30 days later and hair thickness and length determined for linear growth measurements (LHGR). RESULTS: Herein we confirm that the top of the head shows usually a higher hair density than occipital sites, a physiological observation that applies both to men and women. From the technological perspective, we also document that CE improves hair detection in all sites. Interestingly, in affected patients (L and D) the relative increase of hair counts after CE was much higher (range +22.4% to +28.3%) compared with apparently unaffected females (N; range +8.2% to +9.7%). This increase in hair counts was only due in part to the presence of less pigmented thinning hair (thickness less than 40 microm). Such thin hairs were found in statistically significantly higher proportions in younger patients with mildly severe (grade I) patterned alopecia (Ludwig: L). In other patients with hair loss and in more severe forms of patterned alopecia - especially in older patients - the thin hair is not detected in abnormal proportions. In all sites slower growth rates and decreased anagen percentages indicate a defective hair replacement programme distinguishing L patterns from diffuse hair loss and from apparently unaffected patients complaining of chronic hair loss. Globally, we also noted that increasing age is associated with significant regression of scalp hair (decreased hair counts, thinner hair and slower LHGR). CONCLUSION: On the basis of the present data together with female data from the literature and our own studies in male subjects, we suggest a three-step mechanism leading to hair loss 1.Shortening of growth phase the hair cycle with maintained thick hair, i.e. more frequent hair cycling that leads to more hair shedding. 2.Intermittent production of short thin hair, i.e. morphological evidence of miniaturisation. 3.Very occasional or almost no hair production, i.e. dormant follicles or irreversible follicular atrophy. Depending on the genetic background, hormonal microenvironment in the scalp and conditioning of individual hair follicle bio-responses, female and male patterned hair loss may end up into different phenotypes.  相似文献   
18.
Abstract Although numerous investigators have reported on self-perceived oral health status in adult and older adult populations, few have examined how these perceptions change over time. This paper uses data from a longitudinal oral health survey of community-dwelling Canadians aged 50 years and over to explore this issue. Data were collected at baseline and after 3 years. Change was assessed using a global transition judgement and change scores on four subjective oral health status indicators. These indicators addressed chewing capacity, oral and facial pain symptoms, other oral symptoms, and the psychosocial impact of oral disorders. Overall, 23.0% reported that their oral health had worsened over this period, 66.5% that it had remained the same and 10.5% that it had improved. Change scores on the four indicators showed a similar pattern and were significantly associated with these global judgements. Over the same period, substantial proportions lost one or more teeth, acquired new coronal or root DPS increments or experienced loss of periodontal attachment. An additional 17% complained of dry mouth. However, the only clinical indicator associated with changing perceptions of oral health was tooth loss. Of interest was the fact that rates of tooth loss were equally high among those who reported a worsening of oral health and those who reported an improvement. This suggests that the impact of tooth loss on health status may be positive or negative depending upon the condition of the teeth lost.  相似文献   
19.
PROBLEM: To determine if heparin may act directly with antiphospholipid antibodies (APA) to prevent recurrent pregnancy loss (RPL). METHOD: Patients were seen at the University of Texas Southwestern Medical Center. Twenty women with a history of RPL (≥3 miscarriages), positive APA, and an otherwise normal evaluation were treated with heparin in two daily subcutaneous dosages during a successful pregnancy. APA levels were obtained prior to conception and again at 6, 20, and 30 weeks. RESULTS: Heparin reduced APA binding to cardiolipin and phosphatidylserine in a dose-dependent fashion in ELISA. Heparin affinity chromatography absorbed over 80% of the IgG anticardiolipin antibody in serum from women with high levels of APA. Women treated with increasing dosages of heparin during pregnancy had inversely decreasing levels of IgG anticardiolipin antibody. CONCLUSION: Heparin may act by directly binding APA in vivo, thereby decreasing the adverse effects of APA in women with APA associated RPL.  相似文献   
20.
Abstract A female patient exhibiting functional hearing loss in her left ear demonstrated reduced amplitude of P3 component in event-related potentials (ERP) to left monaural stimulation, with preserved N1 and N2 components to stimulation of either ear. This result suggested that stimuli in the affected ear were conducted successfully up to the auditory cortex but that further processing in higher brain regions was 'repressed'. Event-related potential examination for such hysterical disorders could be useful in clarifying their brain mechanism and offer a useful diagnostic clue to its nature.  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