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   3918篇
  免费   310篇
  国内免费   7篇
耳鼻咽喉   25篇
儿科学   92篇
妇产科学   151篇
基础医学   508篇
口腔科学   12篇
临床医学   767篇
内科学   755篇
皮肤病学   56篇
神经病学   281篇
特种医学   66篇
外科学   348篇
综合类   47篇
一般理论   7篇
预防医学   603篇
眼科学   24篇
药学   257篇
中国医学   5篇
肿瘤学   231篇
  2023年   17篇
  2022年   36篇
  2021年   87篇
  2020年   49篇
  2019年   75篇
  2018年   106篇
  2017年   78篇
  2016年   72篇
  2015年   82篇
  2014年   123篇
  2013年   213篇
  2012年   249篇
  2011年   286篇
  2010年   147篇
  2009年   147篇
  2008年   261篇
  2007年   279篇
  2006年   276篇
  2005年   237篇
  2004年   260篇
  2003年   235篇
  2002年   211篇
  2001年   39篇
  2000年   47篇
  1999年   49篇
  1998年   52篇
  1997年   41篇
  1996年   44篇
  1995年   42篇
  1994年   28篇
  1993年   26篇
  1992年   24篇
  1991年   22篇
  1990年   29篇
  1989年   16篇
  1988年   12篇
  1987年   11篇
  1986年   17篇
  1984年   15篇
  1983年   15篇
  1982年   18篇
  1981年   20篇
  1980年   11篇
  1979年   17篇
  1978年   24篇
  1977年   9篇
  1976年   7篇
  1975年   9篇
  1974年   11篇
  1972年   9篇
排序方式: 共有4235条查询结果,搜索用时 15 毫秒
71.
72.
Tulman L  Fawcett J 《Cancer nursing》2007,30(3):205-212
The Comprehensive Inventory of Functioning-Cancer (CIF-CA) was developed to measure actual and desired functional status in women with cancer. CIF-CA items were taken from the Inventory of Functional Status-Cancer, which measures only actual performance of usual activities. Six CIF-CA subscales measure the extent to which women perform usual personal care, family care, household, social, community, and occupational activities following diagnosis of cancer (actual functional status) and the level at which they wish to perform those activities (desired functional status). Reliability and construct validity estimates were obtained using a sample of 190 women with breast, lung, or colon cancer. Internal consistency reliability using average correlations for subscale item to subscale total scores ranged from 0.68 to 0.93 for actual functional status and from 0.61 to 0.85 for desired functional status. Internal consistency reliability coefficients for subscale to total CIF-CA scores ranged from 0.46 to 0.86 for actual functional status and from 0.62 to 0.83 for desired functional status. Initial construct validity coefficients, using subscale to subscale scores, ranged from 0.10 to 0.61 for actual functional status and from 0.33 to 0.62 for desired functional status. The data support continued development of the CIF-CA.  相似文献   
73.
74.
75.
Antibiotic-resistant pathogens are increasingly more prevalent and problematic. Traditional antibiotics are no longer a viable option for dealing with these multidrug-resistant microbes and so new approaches are needed. Bacteriophage-derived proteins such as endolysins could offer one effective solution. Endolysins are bacteriophage-encoded peptidoglycan hydrolases that act to lyse bacterial cells by targeting their cell’s wall, particularly in Gram-positive bacteria due to their naturally exposed peptidoglycan layer. These lytic enzymes have received much interest from the scientific community in recent years for their specificity, mode of action, potential for engineering, and lack of resistance mechanisms. Over the past decade, a renewed interest in endolysin therapy has led to a number of successful applications. Recombinant endolysins have been shown to be effective against prominent pathogens such as MRSA, Listeria monocytogenes, Staphylococcus strains in biofilm formation, and Pseudomonas aeruginosa. Endolysins have also been studied in combination with other antimicrobials, giving a synergistic effect. Although endolysin therapy comes with some regulatory and logistical hurdles, the future looks promising, with the emergence of engineered “next-generation” lysins. This review will focus on the likelihood that endolysins will become a viable new antimicrobial therapy and the challenges that may have to be overcome along the way.  相似文献   
76.
The purpose of this study was to test hypothesized relationships of the health promotion model (HPM) as a means of predicting moderate‐to‐vigorous physical activity (MVPA) among urban, adolescent girls. A secondary analysis of baseline data from a group randomized controlled trial was conducted. The study involved eight urban schools in the Midwestern United States. The sample included girls (N = 517) in the 5th–8th grades. Data were collected on age, body mass index, pubertal status, enjoyment, self‐efficacy, social support, options for physical activity (PA), and commitment to PA. MVPA was measured via accelerometers worn by the girls for 7 days. Structural equation modeling was used to analyze study aims. Mean age of the sample was 11.8 years (standard deviation [SD] = 1.0). Girls attained an average of 3.0 (SD = 1.2) minutes per hour of MVPA. Self‐efficacy had a positive direct (β = .337; p < .001) and total effect (β = .310; p < .001) on MVPA. Social support and options for PA were not significant predictors of commitment to PA or MVPA. Commitment to PA had a negative but nonsignificant effect (β = ?.056; p = .357) on MVPA. The model predicted 10.1% of the variance in MVPA with 9.6% of the variance predicted by self‐efficacy. Limitations include lack of longitudinal analysis and inability to generalize the results to other populations such as boys. PA self‐efficacy continues to emerge as a significant predictor of MVPA in the HPM. Continued theory testing is needed to better understand the correlates and determinants of PA among adolescent girls before designing theory‐based interventions to promote PA.  相似文献   
77.
The authors explored the relationship between assault, substance use disorders, and personality disorders by interviewing 82 substance-dependent inpatients with a structured interview concerning physical and sexual assault as well as the Structured Clinical Interview for DSM-III-R, parts I and II. Sixty percent of subjects met criteria for a personality disorder. Individuals who had experienced assault (n = 43) were more likely to have all types of personality disorder diagnoses (P ≤ 0.001). Those who reported childhood assault were more likely to have Cluster B personality disorders and to meet criteria for more than two personality disorder diagnoses (P ≤ 0.05) compared with those who reported adult assault only. Personality disorders were commonly diagnosed in this group of treatment-seeking, substance-dependent individuals. The effect of substance abuse as well as assault on the development and presentation of personality disorders is likely to be substantial.  相似文献   
78.
Partially purified extracts from 33 human tumors of several histologic types were used as competing antigens in a radioimmunoassay for the p30 protein of an endogenous primate type C virus (M7). Antigens immunologically related to the p30 protein of the M7 virus were detected in two tumors. Like viral p30 antigens previously identified in tissues of several other primates, the antigens found in human tumors crossreact with the p30 protein of the feline RD-114 virus but are unrelated by similar immunologic criteria to the p30 proteins of several other mammalian type C viruses. Gel filtration shows that most of the antigenic activity co-chromatographs with authentic p30 protein. These results, along with those showing nucleic acid sequences related to those of an endogenous primate type C virus in the DNA of human cells, make it clear that humans, like other primates, have type C viral sequences in their genome and can, in some circumstances, express at least one type C viral protein.  相似文献   
79.
Neural abnormalities commonly associated with autism spectrum disorders include prefrontal cortex (PFC) dysfunction and cerebellar pathology in the form of Purkinje cell loss and cerebellar hypoplasia. It has been reported that loss of cerebellar Purkinje cells results in aberrant dopamine neurotransmission in the PFC which occurs via dysregulation of multisynaptic efferents from the cerebellum to the PFC. Using a mouse model, we investigated the possibility that developmental cerebellar Purkinje cell loss could disrupt glutamatergic cerebellar projections to the PFC that ultimately modulate DA release. We measured glutamate release evoked by local electrical stimulation using fixed-potential amperometry in combination with glutamate selective enzyme-based recording probes in urethane-anesthetized Lurcher mutant and wildtype mice. Target sites included the mediodorsal and ventrolateral thalamic nuclei, reticulotegmental nuclei, pedunculopontine nuclei, and ventral tegmental area. With the exception of the ventral tegmental area, the results indicated that in comparison to wildtype mice, evoked glutamate release was reduced in Lurcher mutants by between 9 and 72 % at all stimulated sites. These results are consistent with the notion that developmental loss of cerebellar Purkinje cells drives reductions in evoked glutamate release in cerebellar efferent pathways that ultimately influence PFC dopamine release. Possible mechanisms whereby reductions in glutamate release could occur are discussed.  相似文献   
80.
Objectives. The purpose of this study was to address current gaps in the literature by examining the associations of fast food restaurant (FFR) density around the home and FFR proximity to the home, respectively, with body mass index (BMI) among a large sample of African American adults from Houston, Texas.Methods. We used generalized linear models with generalized estimating equations to examine associations of FFR density at 0.5-, 1-, 2-, and 5-mile road network buffers around the home with BMI and associations of the closest FFR to the home with BMI. All models were adjusted for a range of individual-level covariates and neighborhood socioeconomic status. We additionally investigated the moderating effects of household income on these relations. Data were collected from December 2008 to July 2009.Results. FFR density was not associated with BMI in the main analyses. However, FFR density at 0.5, 1, and 2 miles was positively associated with BMI among participants with lower incomes (P ≤ .025). Closer FFR proximity was associated with higher BMI among all participants (P < .001), with stronger associations emerging among those of lower income (P < .013) relative to higher income (P < .014).Conclusions. Additional research with more diverse African American samples is needed, but results supported the potential for the fast food environment to affect BMI among African Americans, particularly among those of lower economic means.Obesity and its associated health conditions are a growing problem in the United States, with obesity prevalence having more than doubled since the 1960s.1 The health care cost of Americans’ growing waistlines is substantial and expected to top $860 billion by 2030.2 Racial/ethnic disparities in obesity are of particular concern for the nation’s health, with African Americans experiencing the highest prevalence of obesity relative to other racial/ethnic groups.1 The National Health and Nutrition Examination Survey from 2009 to 2010 indicated that 38.8% of African American men and 58.5% of African American women were obese compared with 36.2% of non-Hispanic White men and 32.2% of non-Hispanic White women.3 Racial/ethnic disparities have also been cited for body mass index (BMI), with the gap in BMI growth widening between African Americans and Whites in recent decades.4To better understand the factors associated with these trends, researchers and policymakers are paying increased attention to the retail food environment. The growing availability of low-cost, calorie-dense consumables from fast food restaurants (FFRs) is one of the factors implicated in the nation’s rising BMI.5–7 The availability of FFRs may be particularly relevant to the growing racial/ethnic disparities in BMI because several studies support a higher density of FFRs among predominately African American neighborhoods relative to predominately White neighborhoods.8–11 Moreover, at least 1 study reports stronger relations between fast food availability and fast food consumption among non-White versus White populations.12 Thus, African Americans may be more likely to consume fast food if it is available, and it may be more available to them because FFRs tend to be clustered in African American neighborhoods. Not surprisingly, greater fast food consumption is associated with higher BMI.13–15Several studies examined associations between the availability of fast food and BMI. Fast food availability was most commonly conceptualized as the density of FFRs near a person’s home, work, or school environment. Findings about the associations of FFR density with BMI and overweight or obesity status, however, were mixed,5,11 with some studies supporting positive associations,16–19 and others citing null results.14,20 Less commonly, studies conceptualized fast food availability as the proximity of the closest FFR to a person’s home. Studies taking this approach yielded mixed results regarding relations between FFR proximity and fast food consumption,21,22 as well as between FFR proximity and BMI or obesity status.11,23 Unfortunately, most of these studies focused predominately on White populations, and many had methodological limitations (e.g., self-reported BMI) that could have contributed to mixed results.5,11 We found only a single study that focused on an all-African American sample, which yielded null results regarding associations between FFR density and BMI.24 Although this study had several strengths, including a sample of more than 4500 African Americans and investigator-measured BMI, limitations included only 1 conceptualization of FFR availability (FFR density), and the use of Euclidean distances (“as the crow flies”) in density buffer calculation, which may be less realistic than buffers based on road networks (i.e., the only places along which FFRs can be found).5 In addition, we found no previous studies that examined whether associations between FFR availability and BMI were moderated by household income. Because reasons cited for frequent fast food consumption include both accessibility and affordability,6 it might be that relations of FFRs and BMI are stronger among those of lower economic means for whom fast food might be more affordable than other dining options. Therefore, additional research is needed to better understand the relations of fast food availability and BMI among African Americans.The purpose of this study was to address current gaps in the literature by examining the associations of FFR density around the home and FFR proximity to the home, respectively, with BMI among a large sample of African American adults from Houston, Texas. We additionally investigated the moderating effects of household income on these relations.  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