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   14463篇
  免费   1209篇
  国内免费   30篇
耳鼻咽喉   170篇
儿科学   496篇
妇产科学   295篇
基础医学   2299篇
口腔科学   355篇
临床医学   1452篇
内科学   3065篇
皮肤病学   246篇
神经病学   1075篇
特种医学   513篇
外国民族医学   1篇
外科学   1993篇
综合类   133篇
一般理论   8篇
预防医学   1137篇
眼科学   332篇
药学   1157篇
  1篇
中国医学   14篇
肿瘤学   960篇
  2021年   224篇
  2020年   198篇
  2019年   251篇
  2018年   274篇
  2017年   266篇
  2016年   309篇
  2015年   280篇
  2014年   401篇
  2013年   538篇
  2012年   701篇
  2011年   662篇
  2010年   396篇
  2009年   374篇
  2008年   572篇
  2007年   610篇
  2006年   558篇
  2005年   539篇
  2004年   609篇
  2003年   496篇
  2002年   483篇
  2001年   421篇
  2000年   466篇
  1999年   407篇
  1998年   191篇
  1997年   158篇
  1996年   171篇
  1995年   149篇
  1994年   148篇
  1993年   145篇
  1992年   305篇
  1991年   337篇
  1990年   330篇
  1989年   347篇
  1988年   262篇
  1987年   279篇
  1986年   237篇
  1985年   288篇
  1984年   191篇
  1983年   164篇
  1982年   126篇
  1981年   103篇
  1980年   91篇
  1979年   165篇
  1978年   124篇
  1977年   107篇
  1976年   84篇
  1975年   97篇
  1974年   117篇
  1973年   105篇
  1972年   86篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
ABSTRACT

Measuring hope reliably and accurately remains an important research objective, not least in less prosperous settings where ‘holding on to hope’ may be critically important in the struggle against adverse life conditions. The State Hope Scale was designed for use in the US. Despite reported application in diverse cultures and using translations the scale has not been extensively validated outside US populations. This study contributes to a larger project exploring the measurement of hope and provides a critique of Snyder’s scale as used in a Tanzanian female population of 1021 urban microfinance participants. We evaluate the scale’s validity through assessment of the empirical distribution of scores, item response profiles, internal consistency and discriminatory ability. Participants mostly scored very high and many reached very near the maximum attainable score. Hardly any endorsed the negative half of the response scale. Several problems are discussed including poor discrimination and strong evidence of acquiescence response bias. We also found little association of the scale scores with hypothesised correlates of hope. Future improvements on the measurement of hope are recommended, especially in studies outside the narrow Western context in which the scale was devised.  相似文献   
2.
Non‐melanoma skin cancer frequently results from chronic exposure to ultraviolet (UV) irradiation. UV‐induced DNA damage activates cell cycle arrest checkpoints through degradation of the cyclin‐dependent kinase activators, the cell division cycle 25 (CDC25) phosphatases. We previously reported increased CDC25A in nonmelanoma skin cancer, but CDC25B and CDC25C had not been previously examined. Consequently, we hypothesized that increased expression of CDC25B and CDC25C increases tumor cell proliferation and skin tumor growth. We found that CDC25B and CDC25C were increased in mouse and human skin cancers. CDC25B was primarily cytoplasmic in skin and skin tumors and was significantly increased in the squamous cell carcinoma (SCC), while CDC25C was mostly nuclear in the skin, with an increased cytoplasmic signal in the premalignant and malignant tumors. Surprisingly, forced expression of CDC25B or CDC25C in cultured SCC cells did not affect proliferation, but instead suppressed apoptosis, while CDC25C silencing increased apoptosis without impacting proliferation. Targeting CDC25C to the nucleus via mutation of its nuclear export sequence, however, increased proliferation in SCC cells. Overexpression of CDC25C in the nuclear compartment did not hinder the ability of CDC25C to suppress apoptosis, neither did mutation of sites necessary for its interaction with 14‐3‐3 proteins. Analysis of apoptotic signaling pathways revealed that CDC25C increased activating phosphorylation of Akt on Ser473, increased inhibitory phosphorylation of proapoptotic BAD on Ser136, and increased the survival protein Survivin. Silencing of CDC25C significantly reduced Survivin levels. Taken together, these data suggest that increased expression of CDC25B or CDC25C are mechanisms by which skin cancers evade apoptotic cell death.  相似文献   
3.
4.
Clinical versus ultrasonographic evaluation of scrotal disorders   总被引:1,自引:0,他引:1  
Clinical and ultrasonographic examinations of scrotal disorders were compared in 166 patients in order to determine their ability to distinguish between those diseases requiring surgery and those requiring clinical follow-up only. Ultrasound examinations were efficient in discriminating between normal and pathological findings. Extra-testicular lesions were readily differentiated from testicular ones. Although both clinical and ultrasonographic examinations had high sensitivity (90%) in detecting testicular cancer, the number of false positive findings was smaller after ultrasound examination. This gave a predictive value of a positive test of 53% after ultrasound examination but only 33% after clinical examination. Ultrasound examination may, therefore, reduce the number of surgical explorations in the scrotum and should be performed in patients with suspected testicular pathology based on history and palpatory findings.  相似文献   
5.
6.
Increased peripheral NK cells in aborting women are considered as a predictor of immunological miscarriages. Here, we investigated the diagnostic value of the NK count at the time of abortion. Peripheral NK cells were counted by flow cytometry in 44 women undergoing therapeutic termination of first trimester missed pregnancy (A = 24) or elective abortion (B = 20). Histology of the extracted material was performed and immunological lesions (villitis, intervillositis, vascular thrombosis, increased fibrinoid necrosis) were recorded. Twenty first trimester pregnant women (C1) and 20 nonpregnant women (C2) served as controls. In 20 women of groups A and B (A1 = 10, B2 = 10) count was repeated after 5 days. At abortion time, the NK percentage and number did not differ between groups A and B (18.18%, 360 versus 15.61%, 374), but there was a statistically significant difference between A and C1 (18.18% versus 13.6%, P < 0.03). When histology negative (11) and positive (8) cases were excluded from groups A and B, respectively, NKs were slightly higher in group A (18.18–19.76%) and significantly lower in B (15.61–13.07%, P < 0.05). At the time of second count, aborters' NKs decreased (A1 = 16.64 versus 13.6 and 10.6 in groups C1 and C2 –P = 0.01, respectively). In group B, NK percentage was equal to that of nonpregnant women (10.94 versus 10.6). At the time of abortions, NKs increase only in cases of immune‐mediated miscarriages. Their – in time – count may contribute to the diagnosis of immmunological abortions.  相似文献   
7.
8.
9.
This study estimated the effects of changing multiple levels and combinations of nutrition information format, load, expression, and order on consumers' perceptions of label usefulness in purchase decisions using adaptive conjoint analysis. A shopping mall intercept survey, which was administered by a marketing research firm, assessed consumer preferences for 12 label alternatives produced on Campbell's soup cans to portray nutrition information realistically; 252 of 258 respondents completed the computer interactive interview. Consumers significantly preferred the bar graph format to the bar graph/nutrient density and traditional label formats. Consumers considered the bar graph/nutrient density format to be as useful as the traditional label format. There was a highly significant difference among the three levels of information load; the most information load was preferred regardless of nutrient importance. Consumers significantly preferred nutrition information stated in absolute numbers and percentages vs in absolute numbers only in traditional, or in percentages only expressions. There was a significant difference between consumer preferences for the two types of information order. The findings indicate that consumers clearly preferred the nutrition label that displayed all nutrient values using a bar graph format, offered the most information load, and expressed nutrient values using both absolute numbers and percentages. Consumers also preferred nutrition information rearranged in an order that grouped nutrients that should be consumed in adequate amounts on the top, calories in the middle, and nutrients that should be consumed in lesser amounts on the bottom of the label.  相似文献   
10.
Isolates of Haemophilus influenzae type b (Hib) can be divided into three antigenic groups based on their reactivities with a set of two monoclonal antibodies (MAbs) directed against epitopes in the oligosaccharide region of Hib lipooligosaccharide (LOS) (P. A. Gulig, C. C. Patrick, L. Hermanstorfer, G. H. McCracken, Jr., and E. J. Hansen, Infect. Immun. 55:513-520, 1987). Approximately 24% of Hib strains react with both of these LOS-specific MAbs. Immunoprecipitation experiments involving several of these strains indicated that the epitopes recognized by these MAbs resided in two different LOS molecules, both of which were synthesized by these particular Hib strains. In addition, Western blot (immunoblot) analysis of proteinase K-treated cell extracts of these strains that had been subjected to sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis revealed two different LOS staining patterns when they were probed independently with the two MAbs. Colony blot radioimmunoassay of hundreds of colonies of one of these Hib strains showed that each colony bound both MAbs. Immune electron microscopy confirmed that individual cells of this same Hib strain expressed both types of LOS molecule at the same time. An antibody accessibility radioimmunoassay was used to show that different Hib strains of this type varied in the relative amounts of each of the two MAbs that they could bind to their cell surfaces. These findings indicate that some Hib strains can synthesize two antigenically distinct LOS molecules simultaneously.  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