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   7125篇
  免费   479篇
  国内免费   21篇
耳鼻咽喉   32篇
儿科学   211篇
妇产科学   192篇
基础医学   1204篇
口腔科学   163篇
临床医学   662篇
内科学   1524篇
皮肤病学   286篇
神经病学   681篇
特种医学   209篇
外科学   598篇
综合类   45篇
一般理论   3篇
预防医学   675篇
眼科学   68篇
药学   510篇
中国医学   26篇
肿瘤学   536篇
  2023年   51篇
  2022年   73篇
  2021年   159篇
  2020年   165篇
  2019年   207篇
  2018年   216篇
  2017年   165篇
  2016年   201篇
  2015年   231篇
  2014年   288篇
  2013年   367篇
  2012年   557篇
  2011年   554篇
  2010年   319篇
  2009年   265篇
  2008年   460篇
  2007年   481篇
  2006年   463篇
  2005年   431篇
  2004年   361篇
  2003年   350篇
  2002年   301篇
  2001年   82篇
  2000年   63篇
  1999年   57篇
  1998年   63篇
  1997年   48篇
  1996年   46篇
  1995年   36篇
  1994年   28篇
  1993年   25篇
  1992年   33篇
  1991年   35篇
  1990年   35篇
  1989年   22篇
  1988年   26篇
  1987年   21篇
  1986年   28篇
  1985年   24篇
  1984年   12篇
  1983年   14篇
  1982年   22篇
  1981年   21篇
  1979年   13篇
  1978年   16篇
  1977年   14篇
  1976年   15篇
  1974年   13篇
  1971年   14篇
  1967年   11篇
排序方式: 共有7625条查询结果,搜索用时 31 毫秒
51.
The solutions of methyl methacrylate (MMA) and naphthalene (N), of 2-naphthyl methacrylate (2-NM) and of 1-naphthyl methacrylate (1-NM) in chloroform, acetone, acetonitrile and N,N-dimethylformamide are studied by 1H NMR spectroscopy. In chloroform and in pure MMA, N causes a shift of the signal of the high field vinyl proton Ha of MMA to higher field, whereas in acetone and acetonitrile the signal of Ha has the τ-value for MMA in the absence of N. The Ha signals of 2-NM and 1-NM in acetone, acetonitrile and N,N-dimethylformamide shift downfield as compared with those in chloroform. The τ-value of the downfield vinyl proton Hb does not vary with a change of the solvent. The separation of the vinyl signals Δ=τ(Ha)—τ(Hb) becomes equal to that of pure MMA. The formation of 1:1 complexes between the electron donating naphthalene ring and the electron accepting methacrylic double bond is assumed. The stability constant of the MMA-N complex is 0,22 1.mol?1. Some structures for the complexes are proposed on the basis of molecular models of the monomer molecules. The results confirm the known theories for the influence of the solvents in radical polymerization of MMA. They can explain the kinetic changes of polymerization of 2-NM and 1-NM.  相似文献   
52.
Journal of Public Health - Offshore wind energy is a fast growing market. Accordingly, a correspondingly large number of employees are working at the wind farms. Owing to the harsh operating...  相似文献   
53.
The European Journal of Health Economics - The goal of this study is to provide empirical evidence of the impact of nurse staffing levels on seven nursing-sensitive patient outcomes (NSPOs) at the...  相似文献   
54.
This study aimed to estimate the incidence of hospital‐acquired pressure injury (PI) and its risk factors in inpatient and intensive care units of five hospitals (two public and three private) in the city of Sao Paulo, Brazil. A 6‐month follow‐up prospective cohort study (n = 1937) was conducted from April to September 2013. Baseline and follow‐up measurements included demographic and care information, as well as risk assessments for both undernutrition (NRS‐2002) and PI (Braden scale). Poisson regression with robust variance was used for data analysis. A total of 633 patients (32.60%) showed risk for PI. The incidence rate of PI was of 5.9% (9.9% in public hospitals vs 4.1% in private hospitals) and was higher in intensive care units, compared to inpatient care units (10% vs 5.7%, respectively). Risk for PI increased with age (RR = 1.05; 95% CI 1.04‐1.07); was higher in in public hospitals, compared to private hospitals (RR = 4.39; 95% CI 2.92‐6.61); in patients admitted for non‐surgical reasons compared to those admitted for surgical reasons (RR = 1.91; 95% CI 1.12‐3.27); in patients with longer hospital stays (RR = 1.04; 95% CI 1.03‐1.06); high blood pressure (RR = 1.76; 95% CI 1.17‐2.64); or had a risk for undernutrition (RR = 3.51; 95% CI 1.71‐7.24). Higher scores in the Braden scale was associated with a decreased risk of PI (RR = 0.79; 95% CI 0.75‐0.83). The results of our study indicate that 5.9% of all patients developed PI and that the most important factors that nurses should consider are: patient age, care setting, length of hospitalization, comorbidities, reason for admission and nutrition when planning and implementing PI‐preventative actions.  相似文献   
55.
56.
The histologic findings of 325 necropsies of rheumatic patients at the National Institute of Cardiology in Mexico, between 1980-1985 were studied forty five of them had Aschoff nodules plus valvular inflammation-Out of these 45 cases two groups were formed: children-adolescent group (24 cases) and an adult group (21 cases). The clinical, histologic and laboratory findings were compared. Clinical records were reviewed searching for history of rheumatic fever. Active rheumatic fever was suspected in 16 patients in the younger group (67%) and only in 3 adults (14.2%). As far as Jones' criteria is concerned, the most common finding was carditis, principally in the younger group (83%). In the adult group, it appeared in 50% of the patients. All other criteria were only occasionally seen or could not be identified during the patients lifetime. The most common laboratory finding which could suggest active rheumatic fever were: a high levels of anti-streptolysin in younger patients (95%) and elevation of erythro-sedimentation in adults (83%). We conclude that in active rheumatic fever of the adult; Jones criteria are not met, so the illness is difficult to recognize, and there is clinical-histologic discrepancy. In this context the disease has a "silent" evolution.  相似文献   
57.
A prospective study in order to determine level knowledge of the population about health, before and after the implantation of the Integral Medical Attention Programme to the Family, was carried out at the outpatient services in the "Pedro Borrás" Teaching Community Polyclinic Health Area. Of the population attending to this outpatient area, 917 individuals older than 15 years, were selected at random. These individuals were surveyed at the beginning of the study (November 1986), in order to collect data of main necessary aspects that the population must be acquainted with on health condition and health promotion, and were surveyed again after six months of the performance of the system (May 1987), and results of both surveys were compared and shown in tables with statistical data. The main programmes for health promotion before the implantation of the new system were, known, effectively, by the population in ratios ranging 0.26-0.49. After the performance of the new programme it was observed how the level of knowledge raises to 0.31-0.70, and knowledges on obesity and sedentary habits (0.69) and on prevention of accidents (0.70) becomes significative. We consider all these changes depending on a greater educational work by the physician and nurse in charge of the plan.  相似文献   
58.
Facially amphiphilic polymers carrying cationic and hydrophobic groups on the same repeat unit have shown promising antimicrobial activity and biocompatibility, yet they are prone to suffer from protein adhesion which may induce biofilm formation. To overcome this problem, poly(diitaconate)-based copolymers with cationic/hydrophobic and protein-repellent/charge-neutral repeat units are synthesized. The bioactivity profile of surface-attached polymer networks made from these copolymers depends on the ratio of the cationic and charge-neutral repeat units. In all cases, the protein adhesion is substantially reduced compared to purely cationic polymers. At a 50:50 ratio, the polymer coatings are partially protein-repellent and antimicrobial, yet slightly cell toxic. At an intermediate composition of 30:70, they are still antimicrobial and the cell compatibility is substantially improved. The long-term stability of these materials still has to be determined to judge their suitability for medical applications.  相似文献   
59.
Polish abortions     
Rich V 《Lancet》1994,343(8905):1090
  相似文献   
60.
Chromosome 11q13 markers and D-type cyclins in breast cancer   总被引:7,自引:0,他引:7  
Summary One in six primary human breast cancers has DNA amplification centered on the cyclin D1 gene (CCND1) on chromosome 11q13. This genetic abnormality is preferentially associated with estrogen-receptor positive tumors and may define a sub-class of patients with an adverse prognosis. AlthoughCCND1 has the credentials of a cellular oncogene, being a target for chromosomal translocation and retroviral integration, the 11q13 amplicon encompasses several other markers andCCND1 is not the only candidate for the key gene on the amplified DNA. To assess their relative importance, we have constructed a physical map of the amplified DNA and compared the extent and frequency of amplification across the region. Since it is likely that the gene providing the selective force for amplification will be expressed at elevated levels, we have also examined expression of both RNA and protein. By these criteria, cyclin D1 remains the strongest candidate for the key oncogene on the amplicon and we are currently investigating the functional consequences of its over-expression.Presented by Gordon Peters at the 16th Annual San Antonio Breast Cancer Symposium, San Antonio TX, USA, November 4, 1993; Minisymposium on Molecular Genetics in Breast Cancer.  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