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   11993篇
  免费   823篇
  国内免费   30篇
耳鼻咽喉   57篇
儿科学   413篇
妇产科学   267篇
基础医学   1831篇
口腔科学   129篇
临床医学   1643篇
内科学   2220篇
皮肤病学   185篇
神经病学   1485篇
特种医学   247篇
外科学   1024篇
综合类   101篇
一般理论   18篇
预防医学   1411篇
眼科学   220篇
药学   770篇
中国医学   22篇
肿瘤学   803篇
  2024年   19篇
  2023年   117篇
  2022年   163篇
  2021年   396篇
  2020年   206篇
  2019年   346篇
  2018年   361篇
  2017年   253篇
  2016年   261篇
  2015年   319篇
  2014年   426篇
  2013年   663篇
  2012年   987篇
  2011年   963篇
  2010年   474篇
  2009年   456篇
  2008年   777篇
  2007年   811篇
  2006年   736篇
  2005年   703篇
  2004年   678篇
  2003年   625篇
  2002年   593篇
  2001年   87篇
  2000年   52篇
  1999年   96篇
  1998年   139篇
  1997年   117篇
  1996年   92篇
  1995年   72篇
  1994年   68篇
  1993年   68篇
  1992年   40篇
  1991年   49篇
  1990年   31篇
  1989年   45篇
  1988年   39篇
  1987年   34篇
  1986年   43篇
  1985年   29篇
  1984年   41篇
  1983年   42篇
  1982年   51篇
  1981年   46篇
  1980年   36篇
  1979年   19篇
  1976年   17篇
  1974年   21篇
  1923年   18篇
  1922年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A series of studies conducted in the same region found that programmatic, community-based health and social service interventions have a positive impact on client well-being. These proactive interventions, designed to address the full range of health and social needs, were usually provided at the same–or even lower–costs as uncoordinated, illness-focused care. The results of this series suggest that across-the-board health care reduction, atleast in a system of national health insurance, will produce poorer results, at higher cost, for people with chronic conditions living in the community. Policy planners need more research that concentrates on comparisons of outcomes between and within different models of health and social service delivery. The studies should be designed to help them determine who benefits from different serviceconfigurations carried out within a range of policy environments at various costs.  相似文献   
102.
There is a need to evaluate community support programmes for elderly people. In this randomized control trial (RCT), we determined the effectiveness of 'friendly visitors' in a volunteer programme of a visiting nurses organization in Southern Ontario, Canada. The Volunteer Friendly Visitor Programme was developed to support elderly people receiving homemaking and nursing care in the community. Volunteers are screened, trained, interviewed and matched to homebound elderly clients for general interest, visit expectations and personality. Volunteers spend three to four hours on average per week with clients socializing in mutually agreed-upon ways. The nursing staff identified clients who were lonely for this additional support. These newly-referred clients were randomly allocated to receive a friendly visitor or not for six weeks. Those receiving the volunteer visitor improved in life satisfaction and two social support measures: worth and social integration. Thus, the addition of volunteer visitors to planned homemaking and nursing care made a difference for elderly in the community.  相似文献   
103.
· Background: It has been previously described that Wagner disease is linked to chromosome 5q13-q14. This study was carried out to describe the ophthalmological aspects and report the results of genetic linkage analysis in a large pedigree affected by Wagner disease. · Methods: Fourty members of one same family agreed to be examined. · Results: Twenty patients presented vitreoretinal degeneration in both eyes without any extra-ocular abnormalities. In young patients, visual acuity was usually normal after correction of frequent mild myopia. Presenile cataracts progressed by the third decade and required removal for visual rehabilitation. The primary disorder involved an abnormal vitreous. A few avascular vitreous bands were usually the only optical feature in the mostly empty vitreous cavity. A circumferential vitreous condensation formed in contact with the retina on many spots. Less common retinal findings included retinal detachment, abnormal retinal pigmentation, progressive atrophy of the RPE simulating choroideremia and lattice degeneration. Genetic analysis revealed a highly significant linkage (lod score >5.0) between the disease and 10 markers of the chromosome 5q13-q14 region. Two recombination events allowed us to refine the linked interval to 20 cM between the D5S650 and D5S618 markers. · Conclusion: Ophthalmological aspects of Wagner’s disease appear to progress with age. Regular ophthalmological examination is important for detecting retinal abnormalities. The gene involved in Wagner’s disease lies in a 20 cM interval on chromosome 5q13-q14. Received: 30 June 1998 Revised version received: 5 October 1998 Accepted: 6 October 1998  相似文献   
104.
105.
Videodensitometric analysis of myocardial contrast echocardiography is traditionally performed off line. Recently, an online contrast ultrasound analysis system, Acoustic Densitometry (Hewlett-Packard), was introduced. We compared pixel intensities acquired with Acoustic Densitometry to pixel intensities derived from videodensitometry. A tissue phantom was imaged in phase I using three transducer frequencies (2.5, 3.5, and 5.0 MHz). In phase II, an in vitro flowing tube model with various concentrations of Albunex® was imaged at two flow rates, 0.6 and 1.2 m/sec, and at two transducer frequencies, 2.5 and 3.5 MHz. The relationship between pixel intensities yielded by the two systems for identical ultrasound signals was determined with linear regression. Intensities derived with Acoustic Densitometry strongly correlated with those derived from the offline videodensitometry system. The intensities were related by a predictive multiplicative factor based on display characteristics of the two systems. These results suggest that semiquantitative, online perfusion analysis with Acoustic Densitometry is as sensitive as analysis offline with videodensitometry.  相似文献   
106.
  1. The effect of chronic saccharin (benzosulphimide) consumption on glucose homeostasis was examined in normal lean +/+ mice and genetically obese hyperglycaemic insulin-resistant ob/ob mice.
  2. Consumption of a 5% (w/v) sodium saccharin solution for 7 weeks prevented the development of hyperglycaemia, improved glucose tolerance (area under curve decreased by 51%), reduced the extent of hyperinsulinaemia (by 21%), and reduced excessive weight gain (by 18%) in ob/ob mice.
  3. Consumption of 5% (w/v) sodium saccharin temporarily decreased hyperphagia at the beginning of treatment, decreased hepatic glycogen content (by 47%), increased abdominal muscle glycogen content (by 82%), but did not significantly alter the hypoglycaemic response to exogenous insulin in ob/ob mice.
  4. Consumption of a 1% (w/v) sodium saccharin solution did not prevent the development of hyperglycaemia in ob/ob mice.
  5. Normal lean +/+ mice consuming 5% (w/v) sodium saccharin solution showed a marginal decrease (by 8%) in glycaemia, and glucose tolerance was improved (area under curve decreased by 30%) without a significant change in the insulin response to glucose or the hypoglycaemic effect of exogenous insulin.
  6. The results suggest that chronic consumption of saccharin can defer the development of hyperglycaemia and improve glucose homeostasis in insulin-resistant ob/ob mice through a mechanism that is independent of insulin.
  相似文献   
107.
Protein tyrosine kinases (PTKs) are a family of enzymes sharing a highly conserved catalytic domain which phosphorylates substrate proteins on tyrosine residues. PTKs play a major role in the transduction of the mitogenic signal and are involved in the control of cell proliferation, differentiation, and transformation processes. PTKs can be subdivided into two major types: membrane associated PTKs consisting essentially of growth factor receptors (receptor tyrosine kinases or RTKs) and cytosolic PTKs involved in the intracellular transduction of mitogenic and differentiation signals. From January 1988 to January 1992, PTK activity was assayed in cytosolic fractions prepared from 350 T1-T2, N0-N1 M0, breast carcinomas. Enzymatic activity was measured using phosphate transfer from [32P]-ATP to poly-Glu-Tyr as an artificial substrate. According to our previously reported pilot study, we chose a cut-off value of 12 pmol32P incorporated min–1 mg–1 protein, corresponding to the median value. We found positive PTK levels ( 12 pmol/min/mg) to be correlated with a loss of differentiation according to Scarff-Bloom grade (p < 0.001), negative PR (p = 0.03) and ER status (p = 0.04). With a median follow-up of 30 months (0–82), patients with a positive PTK level presented a smaller 3-year disease free survival than in the PTK negative group of patients (p = 0.07). In Cox multivariate analysis including pT, pN, Scarff-Bloom grade, PR and ER, PTK activity does not emerge as a significant prognostic factor.  相似文献   
108.
This study was designed to determine which objective acoustic or aerodynamic parameters allowed a homogeneous group of patients with unilateral vocal fold paralysis (UVFP) to be distinguished from an age-matched and smoking-matched control group and to search for linear correlations between the objective parameters and the subjective breathiness ratings. Eight patients with recent-onset UVFP and 12 controls were prospectively studied. The acoustic parameters measured for the vowel /a/ at a comfortable frequency and intensity were: jitter, shimmer, harmonics-to-noise ratio, cepstral peak prominence, the difference between the levels of the first two harmonics and the relative energy above 6 kHz. Aerodynamic parameters included the mean flow rate during a sustained /a/ and intraoral pressure during the production of the phoneme /pi/. The long-term average spectrum was calculated for 40 s of text, and the relative average energies in four frequency bands were compared. Six judges rated a mid-/a/ sample using a five-parameter scale with four levels of severity. Nonparametric statistical analysis revealed significant differences ( P<.05) between the UVFP group and the control group for 14 of the 19 parameters studied. Correlations between the objective parameters and perceived breathiness differed in the two groups. Correlations were not always as expected as based on previous literature reports. These measurements provided an objective qualification of voice in patients with UVFP and successfully distinguished them from the normal controls. The objective acoustic and aerodynamic measurements had generally low linear correlations with breathiness ratings in the control group. Higher correlations were seen in the UVFP group, in which breathiness was best correlated with airflow measurements.  相似文献   
109.
PURPOSE: Lung adenocarcinoma presenting as malignant pleural effusion (MPE) is common in Taiwan. Microscopically, the involved pleurae are infiltrated by numerous tumor foci, which suggests that the cancer cells are highly invasive. Overexpression of HER-2/neu has been related to proliferation, antiapoptosis, and the high invasiveness of various cancer cells. We therefore were interested in studying the role of HER-2/neu in MPE-associated adenocarcinoma cell lung cancer (ADCLC). Experimental Design: The expression of HER-2/neu in pleural effusion was measured by ELISA. The HER-2/neu protein expression on tumor cells was evaluated by immunohistochemical (IHC) staining, and gene amplification was assayed by fluorescence in situ hybridization. RESULTS: The mean value of HER-2/neu in pleural effusions of patients with ADCLC and other nonmalignant lung diseases was 9.9 and 2.7 ng/ml, respectively. The difference is statistically significant (P < 0.001). Compared with cytokeratin 19 fragment CYFRA 21-1, the performance of HER-2/neu as a tumor marker in pleural effusion diagnosis was better. Overexpression of HER-2/neu in tumor tissues was found in 70% (23 of 32) of patients with MPE-associated ADCLC, 30% (13 of 43) with stage I/II non-small cell lung cancer (NSCLC), and 44% (14 of 32) with stage III NSCLC. The incidence of HER-2/neu overexpression in tumor tissues of patients with MPE-associated ADCLC was significantly higher than that of patients with stage I-III NSCLC without MPE. HER-2/neu gene amplification was uncommon (1.9%). The correlation between the IHC H-score in tumor samples and the pleural effusion level of HER-2/neu was significant (P < 0.01). A higher incidence of HER-2/neu expression beyond the cutoff point (5.5 ng/ml) in pleural effusions was also found in patients whose IHC H-scores were >50. CONCLUSIONS: These findings indicate that HER-2/neu is important in the pathogenesis of MPE-associated ADCLC and is a potential tumor marker for a diagnosis of pleural effusion.  相似文献   
110.
BACKGROUND AND PURPOSE: As there are few studies examining the impact of radiotherapy on sexuality, we assessed the effect of radiotherapy for carcinoma of the cervix on sexual health and the ability of the LENT system to assess sexual function. MATERIALS AND METHODS: Using the vagina and sexual dysfunction scales of the LENT SOMA scales, subjective scores were measured prospectively before initiation of radiotherapy for 89 women, and at the following times after the start of treatment: 21, 70, 200, 400, 600 and 800 days. RESULTS: There was considerable variation in pre-radiotherapy scores that was not related to disease stage (P=0.054), but was related to patient age (P=0.037, for the average vagina scores and P=0.039 for the maximum vagina scores) The scores were influenced by prior surgery (P<0.0005 for maximum and average vagina scores, P=0.042 average and 0.017 maximum sexual dysfunction scores). For 48 patients for whom data were available at the first three time points, the vagina scores decreased significantly by 70 days compared to pre-radiotherapy scores, but not for sexual dysfunction. There was heterogeneity in the pattern of changes of scores over time: for some women there was no change in vagina subsection score, some increased, and some decreased. CONCLUSIONS: The work has shown variation both in pre-treatment sexual function and in the pattern of changes seen following radiotherapy. Our questionnaire proved useful to score subjective sexual and vaginal problems as given in the LENT subjective scales. Further study is needed to assess the effectiveness of the scales in assessing late effects.  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