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   2871篇
  免费   318篇
  国内免费   21篇
耳鼻咽喉   32篇
儿科学   85篇
妇产科学   58篇
基础医学   363篇
口腔科学   48篇
临床医学   303篇
内科学   539篇
皮肤病学   65篇
神经病学   277篇
特种医学   141篇
外科学   441篇
综合类   73篇
一般理论   2篇
预防医学   303篇
眼科学   52篇
药学   291篇
肿瘤学   137篇
  2021年   39篇
  2020年   29篇
  2019年   45篇
  2018年   56篇
  2017年   35篇
  2016年   42篇
  2015年   50篇
  2014年   58篇
  2013年   90篇
  2012年   111篇
  2011年   135篇
  2010年   90篇
  2009年   61篇
  2008年   119篇
  2007年   138篇
  2006年   125篇
  2005年   124篇
  2004年   104篇
  2003年   100篇
  2002年   119篇
  2001年   116篇
  2000年   107篇
  1999年   69篇
  1998年   48篇
  1997年   50篇
  1996年   43篇
  1995年   33篇
  1994年   21篇
  1993年   27篇
  1992年   55篇
  1991年   69篇
  1990年   60篇
  1989年   75篇
  1988年   76篇
  1987年   63篇
  1986年   61篇
  1985年   61篇
  1984年   52篇
  1983年   36篇
  1982年   18篇
  1981年   21篇
  1979年   26篇
  1978年   23篇
  1977年   38篇
  1976年   29篇
  1975年   29篇
  1974年   31篇
  1973年   28篇
  1972年   16篇
  1968年   18篇
排序方式: 共有3210条查询结果,搜索用时 15 毫秒
31.
32.
OBJECTIVE: To describe the attitudes that women with chronic pelvic pain (CPP) attending gynaecology clinics have to their consultations and to determine the ways in which their health care can be improved. DESIGN: Qualitative study using semistructured individual interviews. SETTING: UK gynaecology outpatient clinics in district general and teaching hospitals. SAMPLE: Twenty-six women with CPP. METHODS: Semistructured individual interviews were conducted. Data gathering and analysis followed a grounded theory approach. MAIN OUTCOME MEASURES: Women's wishes regarding their care and their actual experiences of care. RESULTS: Four main themes emerged. The women wanted (a) personal care, which they often did not receive; (b) to feel understood and to be taken seriously, although they often felt dismissed, which applied both to women with and without an explanation for their pain; (c) explanation as much as cure, but an adequate explanation was often not provided; and (d) to be reassured, which often they were not. Effective reassurance was complex as it included general reassurance and specific reassurance about cause and treatment. CONCLUSIONS: Improvements are needed in the outpatient care of women presenting with CPP. Changes should focus on providing more personal care, so that presenting problems are seen to be taken seriously, findings and management are appropriately explained, and women are more effectively reassured. Interventions need to be developed that meet these needs and tested to determine if they are feasible, acceptable, and improve outcomes.  相似文献   
33.
Malondialdehyde (MDA) is a product of lipid peroxidation and prostaglandin biosynthesis. It is mutagenic and carcinogenic and the major adduct formed by reaction with DNA, a highly fluorescent pyrimidopurinone (M1-dG), has been detected in healthy human liver and leukocyte DNA. Analytical methods used so far for the detection of M1- dG have not been applied to a large number of individuals or variety of samples. Often, only a few microg of DNA from human tissues are available for analysis and a very sensitive assay is needed in order to detect background levels of M1-dG in very small amounts of DNA. In this paper, the development of an immunoslot blot (ISB) assay for the measurement of MI-dG in 1 microg of DNA is described. The limit of detection of the assay is 2.5 adducts per 10(8) bases. A series of human samples were analysed and levels of 5.6-9.5 (n = 8) and 3.1-64.3 (n = 42) of M1-dG per 10(8) normal bases were detected in white blood cell and gastric biopsy DNA, respectively. Results on four human samples were compared with those obtained using an HPLC/32P-post- labelling (HPLC/PPL) method previously developed and indicated a high correlation between M1-dG levels measured by the two assays. The advantages of ISB over other assays including HPLC/PPL, such as the possibility of analysing 1 microg DNA/sample and the fact that it is less time-consuming and laborious, means that it can be more easily used for routine analysis of a large number of samples in biomonitoring studies.   相似文献   
34.
头皮糠疹是常见病是多发病,临床表现为头皮红斑和脱屑,提示皮损部位表皮结构和功能异常,头皮角质层代谢紊乱,最近对头皮糠疹病因和病理的研究证实马拉色菌,皮脂分泌和个体敏感性是形成上述皮损的3个关键因素,硫氧吡啶锌(PTZ或ZPT)可以有效地杀灭马拉色菌,PTZ的颗粒大小和形状对其在头皮的生物利用度有明显的影响。此外,PTZ的抗菌效果有赖于其分子结构的完整性,在外用制剂中加入附加的游离锌,可以有效防止PTZ解离,从而提高其疗效。  相似文献   
35.
BackgroundResearch indicates a possible relationship between adolescent depressive symptoms and physical activity, yet few studies have examined whether trajectories of adolescent physical activity differ among adolescents with and without elevated depressive symptoms.PurposeThis study documented change in physical activity from ages 12–17 years among youth with and without elevated depressive symptoms, and examined the influences of key family, physiological, and demographic covariates on activity patterns.MethodsData were from 371 youth. The sample was 50% female; 76% White, 12% African American, 4% Hispanic, 2% Asian, 2% American Indian, and 4% other or mixed races. Mean age was 12.05 years (SD = 1.63) at Time 1. Latent growth curve modeling (LGM), a cohort-sequential design, and a multiple-group design by level of depressive symptoms were employed.ResultsAdolescent physical activity declined significantly from ages 12–17 for those with and without elevated depressive symptoms. Adolescents with elevated symptoms had lower initial levels of physical activity than individuals without. For youth with low depressive symptoms, male sex and parental support of physical activity were related to higher initial levels of physical activity. For youth with elevated depressive symptoms, male sex, being White, and parental support were related to higher initial levels of physical activity. Additionally, for both groups, increases in parent physical activity were related to less of a decline in adolescent physical activity trajectories.ConclusionsFindings highlight the importance of parental support in promoting physical activity among adolescents with and without elevated depressive symptoms.  相似文献   
36.
Aims The aim was to estimate the incidence of severe hypoglycaemia requiring emergency ambulance assistance, its management and associated costs. Methods A retrospective observational study used routinely collected data for a 1‐year period from December 2009 to November 2010 from the South Central Ambulance Service National Health Service Trust, UK. The main outcome was episodes reported by ambulance personnel and costs were estimated from published data. Results During the 1‐year study period, 398 409 emergency calls were received, of which 4081 (1.02%) were coded as hypoglycaemia. The overall numbers (and annual rate) of hypoglycaemia recorded among people ≥ 15 years with presumed diabetes was 3962 (2.1%), but for those aged 15–35 years was 516 (7.5%) and for those aged ≥ 65 years was 1886 (1.9%). Of those attended, 1441 (35.3%) were taken to hospital. The estimated total cost of initial ambulance attendance and treatment at scene was £553 000; if transport to hospital was necessary, the additional ambulance costs were £223 000 plus emergency department costs of £140 000; and the cost of primary care follow‐up was estimated as £61 000. The average cost per emergency call was £263. The estimated annual cost of emergency calls for severe hypoglycaemia is £13.6m for England. Conclusions Our estimates suggest prevalence of severe hypoglycaemia attended by the emergency services is high in younger age groups and lower for older age groups, although the absolute numbers of severe events in older age groups contribute substantially to the overall costs of providing emergency assistance for hypoglycaemia.  相似文献   
37.
38.
Purpose:?To compare a consumer-directed personal assistance services (PAS) programme with an agency-directed PAS programme.

Method:?A convenience sample was used for this cross-sectional study with one data collection point. Outcomes were compared for consumer-directed and agency-directed PAS. Hierarchical regressions were also used to determine the predictors of outcomes across PAS programmes. In-home interviews were conducted by a trained data collector from April 2000 to December 2001.

Results:?Participants in the consumer-directed programme reported more choices over PAS and satisfaction with PAS. Self-reported outcomes were primarily predicted by the following variables: service arrangement, type of provider, importance of directing PAS, health status, number of personal assistants used in past 12 months, sufficient PAS hours received, and social support.

Conclusions:?Consumer-directed PAS enhances outcomes for many persons with disabilities. Self-reported outcomes are affected by many factors that could be addressed in PAS programme development.  相似文献   
39.
Choi  Y; Greenberg  SJ; Du  TL; Ward  PM; Overturf  PM; Brecher  ML; Ballow  M 《Blood》1996,87(6):2506-2512
B-cell acute lymphoblastic leukemia (B-ALL), more frequently than any other B-lineage neoplasm, exhibits oligoclonal Ig heavy chain (IgH) gene rearrangement in 15% to 43% of all cases studied. To study the molecular processes that promote multiple IgH rearrangements, a comprehensive sequence analysis of a B-ALL case was performed in which seven clonal IgH gene rearrangements were identified. The genetic profiles suggested that a single leukemic progenitor clone evolved into several subclones through dual processes of variable (VH) to preexisting diversity-joining (DJH) gene segment rearrangement and VH to VH gene replacement. Predominant IgH-V usage and the uniquely rearranged clonotype-specific VHDJH region gene sequences were identified using a novel DNA-based gene amplification strategy. Polymerase chain reaction (PCR) was directed by an IgH-J generic primer and a complement of family-specific IgH-V primers that defined the major B-cell IgH-V gene usage. Clonality of rearranged VHDJH bands was substantiated by high resolution denaturant gel electrophoretic analysis. Sequence patterns of the amplified VHDJH fragments segregated into two groups defined by common DJH sequences. Partial N region homology at the VHD junction as well as shared DJH sequences firmly established VH to VHDJH gene replacement as a mechanism generating clonal evolution in one group. In the second subset, oligoclonality was propagated by independent VH gene rearrangements to a common DJH precursor. The contributions of all clonal Ig-VHDJH repertoires for each group was approximately 50% and reflected a symmetric distribution of leukemic subclones generated by either process. Thus, oligoclonal rearrangements evolved by two independent, yet seemingly contemporaneous molecular genetic mechanisms. All seven clones displayed nonfunctional Ig-VHDJH recombinations. These observations may have relevance to the recombinatorial opportunities available during normal B-cell maturation.  相似文献   
40.
The cellular receptor for urokinase-type plasminogen activator (uPAR) binds pro-urokinase (pro-uPA) and facilitates its conversion to enzymatically active urokinase (uPA). uPA in turn activates surface- bound plasminogen to plasmin, a process of presumed importance for a number of biologic processes including cell migration and resolution of thrombi. We have previously shown that uPAR is expressed on the plasma membrane of circulating neutrophils, and we now report that stimulation with phorbol myristate acetate (PMA), FMLP, or tumor necrosis factor- alpha results in a rapid increase in the expression of uPAR. This process is accompanied by an increased cell-associated plasminogen activation after preincubation of neutrophils with pro-uPA in vitro. By subcellular fractionation of unstimulated neutrophils, 50% of uPAR is recovered in fractions containing latent alkaline phosphatase, corresponding to an intracellular compartment of easily mobilizable secretory vesicles distinct from both primary and specific granules, whereas the remaining 50% of uPAR is associated with a compartment eluting close to the specific granules. In contrast, the ligand pro-uPA is primarily (approximately 80%) found in the specific granules, but small amounts of pro-uPA/uPA (approximately 20%) coelute with latent alkaline phosphatase. Stimulation of neutrophils with FMLP results in translocation of uPAR as well as of pro-uPA from the secretory vesicles, whereas stimulation with PMA is required to translocate material from specific granules. Flow cytometry of neutrophils saturated with exogenous diisopropyl fluorophosphate-uPA shows a large excess (approximately 90%) of unoccupied uPAR on resting as well as FMLP- and PMA-stimulated neutrophils, suggesting a possible role for exogenous pro-uPA in providing neutrophils with a potential for plasminogen activation. These processes may be important for neutrophil extravasation and migration through extracellular matrix and for the contribution of neutrophils to resolution of thrombi.  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