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   17845篇
  免费   1111篇
  国内免费   138篇
耳鼻咽喉   112篇
儿科学   494篇
妇产科学   370篇
基础医学   2879篇
口腔科学   347篇
临床医学   1481篇
内科学   4520篇
皮肤病学   301篇
神经病学   1819篇
特种医学   450篇
外科学   1332篇
综合类   48篇
一般理论   5篇
预防医学   1395篇
眼科学   208篇
药学   1330篇
  1篇
中国医学   61篇
肿瘤学   1941篇
  2024年   76篇
  2023年   208篇
  2022年   392篇
  2021年   677篇
  2020年   409篇
  2019年   541篇
  2018年   583篇
  2017年   484篇
  2016年   547篇
  2015年   596篇
  2014年   752篇
  2013年   1000篇
  2012年   1621篇
  2011年   1619篇
  2010年   891篇
  2009年   799篇
  2008年   1307篇
  2007年   1205篇
  2006年   1153篇
  2005年   996篇
  2004年   907篇
  2003年   758篇
  2002年   652篇
  2001年   84篇
  2000年   47篇
  1999年   94篇
  1998年   122篇
  1997年   99篇
  1996年   93篇
  1995年   50篇
  1994年   44篇
  1993年   49篇
  1992年   28篇
  1991年   25篇
  1990年   23篇
  1989年   9篇
  1988年   12篇
  1987年   17篇
  1986年   10篇
  1985年   7篇
  1984年   17篇
  1983年   11篇
  1982年   12篇
  1981年   10篇
  1980年   9篇
  1979年   6篇
  1978年   5篇
  1975年   5篇
  1973年   10篇
  1971年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The risk of needing help with household tasks or of requiring care in old age increases. Using semi-structured, qualitative interviews, beliefs about the usefulness versus uselessness of planning ahead for future care needs (FCN) were investigated in 23 East German, 10 U.S., and 10 Canadian elderly-community dwelling women ( S 65 years). Primary reasons in favor of planning for FCN were: gaining a feeling of security regarding the future, avoiding being a burden to potential helpers, and coping with one's present health conditions. Factors that prevent planning for FCN were: the difficulty foreseeing FCN, the lack of resources to plan, and low levels of perceived vulnerability. The women dealt with the contradictions between these factors that promote and prevent preparation by making general plans which could be adapted in the case of needing help by developing alternative plans or by avoidance of thinking about possible future health crises.  相似文献   
83.
84.
85.
86.
This study examined factors affecting young adults' attitudes about nonfatal suicidal behavior. It evaluated how respondent sex, respondent gender identity, the precipitant of the suicidal act (i.e., a relationship loss, an achievement failure, or a physical illness), and gender of the suicidal person influence reactions to a suicidal decision. In this study of nonfatal suicidal behavior, like in studies of suicide, attitudes were least negative when the suicidal act was in response to a physical illness. Men were more likely to agree with and accept the suicidal decision than women. Androgynous persons, on the other hand, tended to view the decision to kill oneself as foolish, independent of precipitant. They also reported less agreement, acceptance, and sympathy for such decision. The implications of these findings for the prevention of suicidal behaviors are considered. Because gender seems to play a role in the acceptability of suicidal behavior, prevention programs ought to explicitly examine gender issues in attitudes toward suicidal behavior.  相似文献   
87.
88.
Mesenchymal stem cells (MSCs) from bone marrow (BM) and sub-cutaneous fat are known to differentiate into neural cells under appropriate stimuli. We describe here the neural-like differentiation of human MSCs obtained from spleen and thymus, induced either with chemical factors or with co-culture with human Schwann cells (Sc). Under the effect of neural differentiation medium, most MSCs from BM, fat, spleen and thymus acquired morphological changes suggestive of cells of astrocytic/neuronal and oligodendroglial lineages with general up-regulation of neural molecules not correlated with morphological changes. The process was transient and reversible, as MSCs recovered basal morphology and phenotype, as well as their multilineage differentiation potential. Thus, we hypothesized that chemical factors may prime MSCs for neural differentiation, by inducing initial and poorly specific changes. By contrast, co-cultures of MSCs of different origin with Sc induced long-lasting and Sc differentiation, i.e., the expression of Sc myelin proteins for up to 12 days. Our results show that a MSC reservoir is present in tissues other than BM and fat, and that MSCs of different origin have similar neural differentiation potential. This evidence provides new insights into BM-like tissue plasticity and may have important implications for future therapeutic interventions in chronic neuropathies.  相似文献   
89.
BACKGROUND AND OBJECTIVE: To compare the effectiveness of antimicrobial photodynamic therapy (PDT), standard endodontic treatment and the combined treatment to eliminate bacterial biofilms present in infected root canals. STUDY DESIGN/MATERIALS AND METHODS: Ten single-rooted freshly extracted human teeth were inoculated with stable bioluminescent Gram-negative bacteria, Proteus mirabilis and Pseudomonas aeruginosa to form 3-day biofilms in prepared root canals. Bioluminescence imaging was used to serially quantify bacterial burdens. PDT employed a conjugate between polyethylenimine and chlorin(e6) as the photosensitizer (PS) and 660-nm diode laser light delivered into the root canal via a 200-micro fiber, and this was compared and combined with standard endodontic treatment using mechanical debridement and antiseptic irrigation. RESULTS: Endodontic therapy alone reduced bacterial bioluminescence by 90% while PDT alone reduced bioluminescence by 95%. The combination reduced bioluminescence by >98%, and importantly the bacterial regrowth observed 24 hours after treatment was much less for the combination (P<0.0005) than for either single treatment. CONCLUSIONS: Bioluminescence imaging is an efficient way to monitor endodontic therapy. Antimicrobial PDT may have a role to play in optimized endodontic therapy.  相似文献   
90.
OBJECTIVE: Defects in glycosylation of alpha-dystroglycan are associated with several forms of muscular dystrophy, often characterized by congenital onset and severe structural brain involvement, collectively known as dystroglycanopathies. Six causative genes have been identified in these disorders including fukutin. Mutations in fukutin cause Fukuyama congenital muscular dystrophy. This is the second most common form of muscular dystrophy in Japan and is invariably associated with mental retardation and structural brain defects. The aim of this study was to determine the genetic defect in two white families with a dystroglycanopathy. METHODS: The six genes responsible for dystroglycanopathies were studied in three children with a severe reduction of alpha-dystroglycan in skeletal muscle. RESULTS: We identified pathogenic fukutin mutations in these two families. Affected children had normal intelligence and brain structure and shared a limb girdle muscular dystrophy (LGMD) phenotype, had marked elevation of serum creatine kinase, and were all ambulant with remarkable steroid responsiveness. INTERPRETATION: Our data suggest that fukutin mutations occur outside Japan and can be associated with much milder phenotypes than Fukuyama congenital muscular dystrophy. These findings significantly expand the spectrum of phenotypes associated with fukutin mutations to include this novel form of limb girdle muscular dystrophy that we propose to name LGMD2L.  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