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   178082篇
  免费   9399篇
  国内免费   1038篇
耳鼻咽喉   2000篇
儿科学   5351篇
妇产科学   4080篇
基础医学   24938篇
口腔科学   5919篇
临床医学   14869篇
内科学   41236篇
皮肤病学   4367篇
神经病学   16793篇
特种医学   4932篇
外国民族医学   7篇
外科学   18455篇
综合类   786篇
一般理论   68篇
预防医学   17241篇
眼科学   3033篇
药学   12381篇
中国医学   732篇
肿瘤学   11331篇
  2023年   1446篇
  2022年   3188篇
  2021年   5666篇
  2020年   3350篇
  2019年   4751篇
  2018年   6930篇
  2017年   4852篇
  2016年   4755篇
  2015年   5188篇
  2014年   6942篇
  2013年   9051篇
  2012年   13677篇
  2011年   14164篇
  2010年   7883篇
  2009年   6736篇
  2008年   11363篇
  2007年   11339篇
  2006年   10511篇
  2005年   10068篇
  2004年   9077篇
  2003年   8236篇
  2002年   7539篇
  2001年   2211篇
  2000年   2119篇
  1999年   2044篇
  1998年   1350篇
  1997年   1021篇
  1996年   890篇
  1995年   763篇
  1994年   703篇
  1993年   612篇
  1992年   971篇
  1991年   766篇
  1990年   742篇
  1989年   652篇
  1988年   601篇
  1987年   581篇
  1986年   544篇
  1985年   446篇
  1984年   384篇
  1983年   333篇
  1982年   280篇
  1981年   221篇
  1980年   230篇
  1979年   256篇
  1978年   243篇
  1977年   208篇
  1976年   192篇
  1975年   194篇
  1974年   203篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
BACKGROUND: High rates of morbidity and mortality are observed in patients with advanced heart failure (AHF). AHF is now considered the most costly syndrome in cardiology owing to the substantial economic burden associated with hospitalizations for acute decompensation. A management program that involves specialized follow-up by a multidisciplinary team has been suggested as a desirable strategy for improving outcomes for these patients. ObjectivE: To evaluate the impact of a specialized outpatient heart failure (HF) follow-up program for patients with AHF on frequency and duration of hospitalization for HF and functional status. METHODS: We retrospectively studied 167 consecutive patients with AHF who were referred to the outpatient HF follow-up program in our institution between January and November 2002, of whom 147 followed for > or =30 days were included in the analysis. In addition to demographic and baseline clinical characteristics, HF medication and NYHA functional class, the number and duration of hospitalizations for HF during the previous 12 months were recorded and compared at the time of referral and after a follow-up period of 6.5+/-3 months. RESULTS: Of the 147 patients analyzed (aged 60.8+/-13 years; 79% male; left ventricular ejection fraction 27+/-11%), 67% were in NYHA functional class III, 20% in class II and 13% in class IV at the time of referral. There was a significant improvement in functional class during the mean follow-up period: 55% of the patients were in class III, 37% in class II, 5% in class I and 3% in class IV (p<0.0001). The proportion of patients on beta-blockers or spironolactone increased from 33% and 51% at the time of referral to 69% and 71% respectively after referral (p<0.0001). In the 12 months before referral, 39% of the patients had been hospitalized for acute decompensation of HF (87 hospitalizations - mean 7.2/month) versus 13% of the patients during the mean follow-up period (25 hospitalizations - 3.8/month, p<0.0001). No significant differences were found in the proportion of patients on angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, digoxin or diuretics, or in the mean duration of hospitalization before and after referral. ConclusioN: The specialized follow-up of patients with AHF by a team with expertise in HF resulted in significant therapeutic optimization. Increased use of beta-blockers and spironolactone was associated with significant improvement in functional capacity and significant reduction in hospitalizations.  相似文献   
102.
Atopy may be associated with a reduced T-cell function early in life, particularly regarding maturation of Th1 responses. The T-cell surface molecules CD2 and CD28 are involved in important T-cell activation pathways. Stimulation via the CD2 receptor increases the responsiveness to interleukin (IL)-12, which is a potent inducer of Th1 responses, whereas CD28 stimulation is critical for Th2 differentiation. Our aim was to prospectively study the expression of the cell-surface markers CD2 and CD28 on T-cells in relation to development of atopic disease. Children (n = 172) were followed from birth to 18 months and the cumulative history of atopic disease was recorded. Blood samples were obtained at birth and at 18 months, and in a subgroup of 78 infants also at 3, 6 and 12 months. Flow cytometry was used to analyze the T-cell markers CD2 and CD28, the latter also within the subsets of T-helper (CD4+) and T-cytotoxic (CD8+) cells. At 18 months, 31 children had and 118 did not have atopic symptoms. At this age, skin prick test (SPT) positive children with atopic symptoms with or without an atopic family history (AFH) showed a lower expression of CD2 mode fluorescence intensity (FI) as well as a lower proportion of CD2+ cells, as compared with non-sensitized children with neither atopic symptoms nor AFH. This was accompanied by a higher expression of CD28 FI on CD2+CD8+CD28+ cells. No significant differences were seen at time points before 18 months, although the proportion of CD2+ tended to be low also earlier in life. In conclusion, the observed reduced expression of CD2 in atopic infants may support previous findings that atopy is associated with a reduced CD2 function. The high CD28 FI in SPT positive children with atopic symptoms may possibly be a consequence of a TH2-skewed immune system.  相似文献   
103.
The purpose of this study was to present normative values for thumb abduction and adduction and also to present measures of reliability of the measuring system arising from the use of the Ab-Adductometer. With the Ab-Adductometer, we obtained abductor and adductor measurements of intrinsic muscle strength of the healthy hand thumb in 600 volunteers. Handgrip strength values were obtained with the Jamar dynamometer. Age and male-female specific reference ranges for the Ab-Adductometer and the Jamar dynamometer are presented. This study, with a very large number of volunteer subjects, 600, presents reference ranges for pure palmar adduction and abduction of the thumb. The results indicate that the Ab-Adductometer is a clinically useful device for the purpose of quantitatively measuring thumb adduction and abduction strength at various starting angles of thumb abduction relative to the plane of the palm. The device may be especially helpful in the evaluation of compressive neuropathies of the median or ulnar nerves such as carpal tunnel syndrome or cubital tunnel syndrome as well as for primary disease of the peripheral nerves that affect intrinsic muscles and for thumb function in proximal conditions such as tetraplegia and brachial plexopathy.  相似文献   
104.
Apical ballooning is a novel clinical entity reported in different contexts of physical and psychological stress, which is more common in middle-aged women. Of unknown etiology, the syndrome is characterized by a sudden and transient dilatation of the left ventricular apex in the absence of obstructive atherosclerotic coronary disease or evidence of myocardial necrosis, with total late recovery of ventricular function. The authors report the case of a 53-year-old woman who was admitted to the emergency room with left arm ischemia and low cardiac output, requiring ventilatory support. Left catheterization showed typical medial and apical myocardial dysfunction, with normal coronary arteries. Transesophageal echocardiography revealed a thrombus attached to the lower face of the aortic arch, which probably explained the thromboembolism of the arm but was unlikely to be the cause of the left ventricular dysfunction since there were no enzymatic or electrocardiographic signs of myocardial necrosis and normal wall motion was fully recovered.  相似文献   
105.
106.
107.
108.
BACKGROUND/PURPOSE: The polysaccharide-rich composition of Aloe vera extracts (Aloe barbadensis Miller), often used in cosmetic formulations, may impart moisturizing properties to the product. The aim of this study was to evaluate the effect of cosmetic formulations containing different concentrations of freeze-dried Aloe vera extract on skin hydration, after a single and a 1- and 2-week period of application, by using skin bioengineering techniques. METHODS: Stable formulations containing 5% (w/w) of a trilaureth-4 phosphate-based blend were supplemented with 0.10%, 0.25% or 0.50% (w/w) of freeze-dried Aloe vera extract and applied to the volar forearm of 20 female subjects. Skin conditions in terms of the water content of the stratum corneum and of transepidermal water loss (TEWL) (Corneometer CM 825 and Tewameter TM 210) were analysed before and after a single and 1- and 2-week period of daily application. RESULTS: After a single application, only formulations supplemented with 0.25% and 0.50% (w/w) of Aloe vera extract increased the water content of the stratum corneum, while after the 2-week period application, all formulations containing the extract (0.10%, 0.25% and 0.50%) had the same effect, in both cases as compared with the vehicle. TEWL was not modified after a single and after 1- and 2-week period of application, when compared with the vehicle. CONCLUSION: Our results show that freeze-dried Aloe vera extract is a natural effective ingredient for improving skin hydration, possibly through a humectant mechanism. Consequently, it may be used in moisturizing cosmetic formulations and also as a complement in the treatment of dry skin.  相似文献   
109.
110.
OBJECTIVE: To examine the economic consequences of effective antihypertensive treatment using the novel vasodilating beta1-adrenoceptor antagonist nebivolol (Nebilet) from the perspective of the healthcare provider. METHODS: The evaluation was based on a postmarketing surveillance study in Germany involving 8682 moderately hypertensive patients. Using the Framingham Risk Model, the antihypertensive effectiveness of nebivolol after 6 weeks of treatment was extrapolated to estimate the reductions in 10-year risks of cardiovascular events. Data sources included direct costs for medical and invasive cardiovascular interventions in Germany, costs of therapy in the US and the UK, and estimates on the prevalence of cardiovascular events issued by the American Heart Association. RESULTS: Six-week antihypertensive treatment resulted in a DBP reduction of 13.7 mm Hg. The rate of responders, defined as those patients achieving DBP <90 mm Hg, was 70%. SBP was reduced by 26.1 mm Hg. According to the Framingham Risk Model, 313 deaths would be avoided. Coronary heart disease (CHD) could be reduced by 94 cases (from 1339 to 1245 events) and 150 strokes would be avoided (from 518 to 368 events) in a 10-year period. This reduction of 244 cardiovascular events among the 8682 patients investigated corresponded to cost savings of between Euro 250,000 and Euro 2.5 million, depending on the healthcare environment and the intervention applied. CONCLUSION: Treatment of moderately hypertensive patients with nebivolol can be considered cost effective. Nebivolol has the potential to decrease the overall long-term costs of medical care for patients with hypertension.  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