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   2910篇
  免费   194篇
  国内免费   5篇
耳鼻咽喉   20篇
儿科学   109篇
妇产科学   201篇
基础医学   410篇
口腔科学   77篇
临床医学   260篇
内科学   777篇
皮肤病学   43篇
神经病学   359篇
特种医学   64篇
外科学   259篇
综合类   11篇
一般理论   2篇
预防医学   181篇
眼科学   29篇
药学   144篇
中国医学   3篇
肿瘤学   160篇
  2023年   35篇
  2022年   50篇
  2021年   128篇
  2020年   49篇
  2019年   115篇
  2018年   125篇
  2017年   84篇
  2016年   92篇
  2015年   80篇
  2014年   127篇
  2013年   164篇
  2012年   232篇
  2011年   208篇
  2010年   116篇
  2009年   108篇
  2008年   177篇
  2007年   162篇
  2006年   175篇
  2005年   164篇
  2004年   153篇
  2003年   111篇
  2002年   112篇
  2001年   15篇
  2000年   21篇
  1999年   15篇
  1998年   27篇
  1997年   16篇
  1996年   18篇
  1995年   9篇
  1994年   10篇
  1993年   22篇
  1992年   6篇
  1991年   16篇
  1990年   10篇
  1989年   10篇
  1988年   15篇
  1987年   11篇
  1986年   15篇
  1985年   9篇
  1983年   12篇
  1982年   4篇
  1981年   7篇
  1978年   5篇
  1976年   4篇
  1975年   8篇
  1974年   7篇
  1973年   4篇
  1967年   8篇
  1966年   4篇
  1933年   3篇
排序方式: 共有3109条查询结果,搜索用时 20 毫秒
991.
992.
Absolute uterine factor infertility (UFI) refers to the refractory causes of female infertility stemming from the anatomical or physiological inability of a uterus to sustain gestation. Today, uterine factor infertility affects 3-5% of the population. Traditionally, although surrogacy and adoption have been the only viable options for females affected by this condition, the uterine transplant is currently under investigation as a potential medical alternative for women who desire to go through the experience of pregnancy. Although animal models have shown promising results, human transplantation cases have only been described in case reports and a successful transplant leading to gestation is yet to occur in humans. Notwithstanding the intricate medical and scientific complexities that a uterine transplant places on the medical minds of our time, ethical questions on this matter pose a similar, if not greater, challenge. In light of these facts, this article attempts to present the ethical issues in the context of experimentation and standard practice which surround this controversial and potentially paradigm-altering procedure; and given these, introduces "The Montreal Criteria for the Ethical Feasibility of Uterine Transplantation", a set of proposed criteria required for a woman to be ethically considered a candidate for uterine transplantation.  相似文献   
993.
994.
Background: While health insurance claims data are often used to estimate the costs of renal replacement therapy in patients with end-stage renal disease (ESRD), the accuracy of methods used to identify patients receiving dialysis — especially peritoneal dialysis (PD) and hemodialysis (HD) — in these data is unknown.♦ Methods: The study population consisted of all persons aged 18 - 63 years in a large US integrated health plan with ESRD and dialysis-related billing codes (i.e., diagnosis, procedures) on healthcare encounters between January 1, 2005, and December 31, 2008. Using billing codes for all healthcare encounters within 30 days of each patient’s first dialysis-related claim (“index encounter”), we attempted to designate each study subject as either a “PD patient” or “HD patient.” Using alternative windows of ± 30 days, ± 90 days, and ± 180 days around the index encounter, we reviewed patients’ medical records to determine the dialysis modality actually received. We calculated the positive predictive value (PPV) for each dialysis-related billing code, using information in patients’ medical records as the “gold standard.”♦ Results: We identified a total of 233 patients with evidence of ESRD and receipt of dialysis in healthcare claims data. Based on examination of billing codes, 43 and 173 study subjects were designated PD patients and HD patients, respectively (14 patients had evidence of PD and HD, and modality could not be ascertained for 31 patients). The PPV of codes used to identify PD patients was low based on a ± 30-day medical record review window (34.9%), and increased with use of ± 90-day and ± 180-day windows (both 67.4%). The PPV for codes used to identify HD patients was uniformly high — 86.7% based on ± 30-day review, 90.8% based on ± 90-day review, and 93.1% based on ± 180-day review.♦ Conclusions: While HD patients could be accurately identified using billing codes in healthcare claims data, case identification was much more problematic for patients receiving PD.  相似文献   
995.
Behavior Genetics - Externalizing behavior is substantially affected by genetic effects, which are moderated by environmental exposures. However, little is known about whether these moderation...  相似文献   
996.
Abstract

Objective: This meta-analysis examines the predictive validity of client change language subtypes in motivational interviewing (MI) sessions addressing addictive behavior change. Method: A systematic review identified k?=?13 primary studies, contributing 16 MI conditions (N?=?1556). The pooled correlation coefficient was used to assess the significance, direction, and strength of seven language subtypes (i.e., reason, desire, need, ability, commitment, taking steps, and other) by three valences (i.e., frequency positive or change talk, frequency negative or sustain talk, and proportion change talk) and their relationship to subsequent engagement in addictive behavior. Results: For frequency measures, more sustain talk related to reason, desire, ability, and other were associated with more addictive behavior at follow up. Other change talk was associated with MI outcomes but in an unexpected direction (i.e., more addictive behavior). Proportion measures showed more proportion change talk-reason and -other statements were associated with less addictive behavior at follow up. Sensitivity analyses indicated some heterogeneity and instability of effect sizes, but no evidence of publication bias. Conclusions: This preliminary meta-analysis suggests that aggregate measures of change and sustain talk are comprised of statement subtypes that are not equally meaningful in predicting outcome following MI for addictive behavior change.  相似文献   
997.
998.

Background

Motivational impairments are a core feature of schizophrenia and although there are numerous reports studying this feature using clinical rating scales, objective behavioural assessments are lacking. Here, we use a translational paradigm to measure incentive motivation in individuals with schizophrenia.

Methods

Sixteen stable outpatients with schizophrenia and sixteen matched healthy controls completed a modified version of the Effort Expenditure for Rewards Task that accounts for differences in motoric ability. Briefly, subjects were presented with a series of trials where they may choose to expend a greater amount of effort for a larger monetary reward versus less effort for a smaller reward. Additionally, the probability of receiving money for a given trial was varied at 12%, 50% and 88%. Clinical and other reward-related variables were also evaluated.

Results

Patients opted to expend greater effort significantly less than controls for trials of high, but uncertain (i.e. 50% and 88% probability) incentive value, which was related to amotivation and neurocognitive deficits. Other abnormalities were also noted but were related to different clinical variables such as impulsivity (low reward and 12% probability). These motivational deficits were not due to group differences in reward learning, reward valuation or hedonic capacity.

Conclusions

Our findings offer novel support for incentive motivation deficits in schizophrenia. Clinical amotivation is associated with impairments in the computation of effort during cost-benefit decision-making. This objective translational paradigm may guide future investigations of the neural circuitry underlying these motivational impairments.  相似文献   
999.
1000.
Human γδ cells expressing TCRVγ9 are T lymphocytes with great potential for cancer immunotherapy and unconventional pattern of antigen specificity. These HLA-unrestricted lymphocytes are specifically reactive to non-peptide metabolites (phosphoantigens) and to the butyrophilin 3A (BTN3A/CD277) protein. Whether recognition of such highly different structures trigger the same activation signaling pathway remains unclear, however. Here we combined fluorescent cell barcoding and phosphoflow analysis of TCRVγ9+ T lymphocytes to compare simultaneously the level of several signaling phosphoproteins after activation by phosphoantigen (BrHPP) or by anti-BTN3A (monoclonal antibody 20.1). This approach shows that the same pathways involving ZAP70, PLCγ2, Akt, NFκB p65, MAPK p38 and Erk1, were induced by either of these stimuli. These data strongly suggest the TCRVγ9+ T lymphocytes detect phosphoantigens and butyrophilin A3 by the same recognition process.  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