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   6668篇
  免费   477篇
  国内免费   24篇
耳鼻咽喉   49篇
儿科学   195篇
妇产科学   211篇
基础医学   995篇
口腔科学   154篇
临床医学   688篇
内科学   1395篇
皮肤病学   170篇
神经病学   810篇
特种医学   162篇
外科学   635篇
综合类   19篇
一般理论   3篇
预防医学   577篇
眼科学   124篇
药学   454篇
中国医学   26篇
肿瘤学   502篇
  2024年   12篇
  2023年   69篇
  2022年   95篇
  2021年   201篇
  2020年   121篇
  2019年   198篇
  2018年   208篇
  2017年   194篇
  2016年   212篇
  2015年   213篇
  2014年   248篇
  2013年   353篇
  2012年   555篇
  2011年   582篇
  2010年   291篇
  2009年   273篇
  2008年   419篇
  2007年   430篇
  2006年   392篇
  2005年   408篇
  2004年   347篇
  2003年   329篇
  2002年   317篇
  2001年   73篇
  2000年   63篇
  1999年   80篇
  1998年   39篇
  1997年   44篇
  1996年   31篇
  1995年   20篇
  1994年   26篇
  1993年   18篇
  1992年   32篇
  1991年   40篇
  1990年   34篇
  1989年   17篇
  1988年   21篇
  1987年   19篇
  1986年   16篇
  1985年   13篇
  1984年   21篇
  1983年   10篇
  1982年   8篇
  1981年   11篇
  1980年   7篇
  1979年   9篇
  1978年   6篇
  1977年   5篇
  1974年   5篇
  1973年   5篇
排序方式: 共有7169条查询结果,搜索用时 15 毫秒
31.
Chlorella vulgaris, an unicellular green algae, or its acetone-extract (Ac-Ex) were administered orally to Meth A tumor bearing BALB/c or (BALB/c DBA/2)F1 (CDF1) mice. When CDF1 mice were fed daily with 10% dried powder of Chlorella vulgaris (CVP) containing diet before and after Meth A tumor inoculation, the growth of rechallenged Meth A tumor was significantly suppressed in an antigen-specific manner. Augmentation of antitumor resistance was exhibited also by Winn assay using lymph node cells of tumor-bearing mice orally administered with CVP or Ac-Ex. Antigen-specific concomitant immunity in these mice were mediated by cytostatic T cells but not by cytotoxic T cells. Natural killer cells seemed not to contribute in antitumor resistance in this system.  相似文献   
32.
The prototype cone-beam CT (CBCT) has a larger beam width than the conventional multi-detector row CT (MDCT). This causes a non-uniform angular distribution of the x-ray beam intensity known as the heel effect. Scan conditions for CBCT tube current are adjusted on the anode side to obtain an acceptable clinical image quality. However, as the dose is greater on the cathode side than on the anode side, the signal-to-noise ratio on the cathode side is excessively high, resulting in an unnecessary dose amount. To compensate for the heel effect, we developed a heel effect compensation (HEC) filter. The HEC filter rendered the dose distribution uniform and reduced the dose by an average of 25% for free air and by 20% for CTDI phantoms compared to doses with the conventional filter. In addition, its effect in rendering the effective energy uniform resulted in an improvement in image quality. This new HEC filter may be useful in cone-beam CT studies.  相似文献   
33.
34.
We describe a de novo balanced reciprocal translocation between the long arms of chromosomes 5 and 8 [46,XX,t(5;8)(q35;q24.1)] in a 15-month-old girl with a typical Sotos syndrome phenotype. Involvement of the 5q35 region was previously reported (Maroun et al. [1994: Am J Med Genet 50:291-293]) as one of translocation breakpoints in the present patient. We suggest that the gene responsible for Sotos syndrome is located to a distal long-arm region of chromosome 5.  相似文献   
35.
Acute hypercalcaemia was observed in a 54 year old woman followed up over a five year period for a lymphocytic non-Hodgkin lymphoma, a complication which is rare in chronic lymphoproliferative disorders except multiple myeloma. This case is of interest from 3 points of view: haematological: the simultaneous occurrence of hypercalcaemia (4.80 mmol/l) and of a leukaemic phase (19,300 lymphocytes/mm3) with no signs of "transformation" of the haemopathy; physiopathological: increased osteoclastic bone resorption and a rise in serum parathormone (0.21 to 4.82 ng/ml); therapeutic: efficacy of oral ethane 1, hydroxy 1, 1 diphosphonate (20 mg/kg/day) in treating the hypercalcaemia.  相似文献   
36.
Summary The aim of this study was to assess the prevalence of psychiatric disturbance in three primary medical care settings (Brasilandia, Servidor and Barra Funda) in a large city of a developing country and the effect of relevant sociodemographic factors (sex, age, marital status, occupation, migration, colour of skin and housing) on minor psychiatric morbidity.The prevalence rates of psychiatric morbidity were estimated at two levels: for minor and for severe psychiatric disturbance. The extent of minor psychiatric morbidity was found to be very high in the three primary medical care clinics (Brasilandia 56%, Servidor 50% and Barra Funda 47%) and about one-quarter of persons attending each clinic presented a severe psychiatric disturbance.Two factors were found to be associated with minor psychiatric morbidity (sex and family income per capita) when the joint effects of the sociodemographic variables were investigated. Women were more likely than men to present a minor psychiatric disturbance and the lower the family income the higher the risk of minor psychiatric morbidity. These findings are discussed in the light of the mental health of the urban poor living in the large cities of developing countries.  相似文献   
37.
Prevention Science - The long-term sustainment of bullying prevention programs has rarely been investigated. This study addresses this gap by identifying facilitators and barriers to the systematic...  相似文献   
38.
There is a lack of robust evidence regarding outcomes for day care use among older people living with long-term conditions (LTCs). Day care is provided by independent, private and voluntary and charitable sectors. This systematic review aims to establish current evidence of outcomes for older people with LTCs attending day care services and outcomes on carers, across all service models. Narrative synthesis of quantitative and qualitative data was undertaken. The review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A systematic literature search was carried out across eight electronic databases and reference lists of key journals between 2004 and October 2020 were searched. Searches returned 1,202 unique titles. Forty-five articles from 16 countries met the criteria on review of title, abstract and full article. There is limited evidence suggesting improved levels of perceived psychological health, quality of life, perceived general health, physical health and functioning for older people attending day care who have LTCs. The respite function of day care resulted in positive outcomes for carers. Studies evaluating outcomes for participants or carers were limited in quantity and quality. There is limited information regarding outcomes for day care attendance for older people with multiple LTCs from existing literature. Further research focusing on LTCs and day care attendance would benefit this field.  相似文献   
39.
BACKGROUND: IgE to cross-reacting carbohydrate determinants has already been described by several authors, but their function and distribution are still a matter of debate. In previous studies we showed how the presence of IgE to bromelain could be a useful and simple marker of the presence of IgE to carbohydrate epitopes. METHODS: A survey of 1,831 subjects with a suspected allergic respiratory disease has been carried out by detecting IgE to bromelain. Data were analysed on the basis of demographical and allergological parameters. To find out whether a glycoprotein is capable of triggering an allergic reaction, 1,076 subjects were also skin tested with several purified molecules bearing carbohydrate side chains differing in number, composition and complexity. RESULTS: An overall prevalence of 23% of positive IgE to cross-reacting carbohydrate determinants was recorded. Prevalence varied when subsets of non-allergic (5%), non-pollen-allergic (10%), and pollen-allergic (31%) subjects were considered. Prevalence further increased in subsets with multiple pollen sensitization (71%), and with a previous pollen immunotherapy course (46%), whereas minor differences were found in gender and age distribution. Almost all the allergenic extracts recorded negative in the skin test gave a positive IgE test in vitro. A higher correlation was found mainly with plant-derived allergenic extracts, whereas a lower one was recorded with mites and fungi. Horseradish peroxidase was the only glycoprotein capable of exerting a positive skin test in 21% of the subjects with IgE to cross-reacting carbohydrate determinants, 80% of them having IgE to the HRP molecule. CONCLUSIONS: IgE to cross-reacting carbohydrate determinants are common among the allergic population and the binding to skin test negative allergenic extracts further confirms their poor biological activity. Further studies on horseradish peroxidase should be carried out to define the role of the glycan side chains in its allergenic activity.  相似文献   
40.
Triplication of chromosomal region 1p36.3 is a rare genomic rearrangement. In this report, we delineate the phenotypic spectrum associated with 1p36.3 triplications. We describe four patients with microtriplications of variable size, but with a strong phenotypic overlap, and compare them to previously described patients with an isolated triplication or duplication of this region. The 1p36.3 triplication syndrome is associated with a distinct phenotype, characterized by global developmental delay, moderate intellectual disability, seizures, behavioral problems, and specific facial dysmorphic features, including ptosis, hypertelorism, and arched eyebrows. The de novo occurrence of these microtriplications demonstrates the reduced reproductive fitness associated with this genotype, in contrast to 1p36.3 duplications which are mostly inherited and can be associated with similar facial features but with a less severe developmental phenotype. The shared triplicated region encompasses four disease-related genes of which GABRD and SKI are most likely to contribute to the phenotype.  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