全文获取类型
收费全文 | 49052篇 |
免费 | 3739篇 |
国内免费 | 111篇 |
专业分类
耳鼻咽喉 | 468篇 |
儿科学 | 1833篇 |
妇产科学 | 1293篇 |
基础医学 | 6118篇 |
口腔科学 | 427篇 |
临床医学 | 6263篇 |
内科学 | 8872篇 |
皮肤病学 | 999篇 |
神经病学 | 4987篇 |
特种医学 | 960篇 |
外科学 | 5136篇 |
综合类 | 395篇 |
现状与发展 | 1篇 |
一般理论 | 86篇 |
预防医学 | 6936篇 |
眼科学 | 843篇 |
药学 | 3416篇 |
中国医学 | 60篇 |
肿瘤学 | 3809篇 |
出版年
2024年 | 57篇 |
2023年 | 512篇 |
2022年 | 815篇 |
2021年 | 1814篇 |
2020年 | 1104篇 |
2019年 | 1793篇 |
2018年 | 1896篇 |
2017年 | 1459篇 |
2016年 | 1549篇 |
2015年 | 1627篇 |
2014年 | 2289篇 |
2013年 | 2990篇 |
2012年 | 4481篇 |
2011年 | 4405篇 |
2010年 | 2405篇 |
2009年 | 1989篇 |
2008年 | 3450篇 |
2007年 | 3393篇 |
2006年 | 3154篇 |
2005年 | 2955篇 |
2004年 | 2550篇 |
2003年 | 2135篇 |
2002年 | 1862篇 |
2001年 | 213篇 |
2000年 | 137篇 |
1999年 | 215篇 |
1998年 | 301篇 |
1997年 | 216篇 |
1996年 | 175篇 |
1995年 | 155篇 |
1994年 | 114篇 |
1993年 | 98篇 |
1992年 | 65篇 |
1991年 | 46篇 |
1990年 | 47篇 |
1989年 | 50篇 |
1988年 | 34篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 37篇 |
1983年 | 36篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1978年 | 20篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Jennifer R. Jamison 《Australian and New Zealand journal of public health》1995,19(5):522-524
Abstract: To ascertain whether the diet of young students in health-related courses conformed to Australian dietary targets for 1995 and to identify nutritional needs in view of dietary targets for 2000, 246 undergraduate students analysed their weighed diet for three or five days. Eight often male participants were meeting the dietary goals for 1995 for fibre and fat intake and six of ten were meeting the goals for 2000. More female participants were meeting the goals for fat, but less than half of the females were meeting the 1995 goals for fibre. Some 84 per cent of females, but only 29 per cent of males, were meeting the 1995 dietary goals for sodium. Few participants derived 10 per cent or less of their energy from saturated fat or 10 per cent of their energy from polyunsaturated fatty acids. Substantial numbers of participants failed to meet the recommended daily intakes of zinc, calcium, magnesium and iron (females). Education of specific subgroups and modifications to food production and processing are proposed. 相似文献
92.
Sherilyn Gross Karen Helm Jennifer J. Gruntmeir Wayne S. Stillman David W. Pyatt Richard D. Irons 《European journal of haematology》1997,59(5):318-326
Abstract: Our current understanding of human haematopoietic stem cell biology is based in part on the characterization of human CD34+ bone marrow cell differentiation in vitro. CD34 is highly expressed on early stem cells and haematopoietic progenitor cells with clonogenic potential and is gradually lost during differentiation and commitment. However, CD71 (transferrin receptor) is expressed at low levels on early stem cells and generally increases during haematopoietic progenitor cell proliferation. We reasoned that the combination of these surface markers would provide a useful framework for the simultaneous analysis of multiple lineage differentiation of CD34+ haematopoietic progenitor cells in liquid culture. In this report, we identify the phenotype of distinct subpopulations of myeloid, erythroid and lymphoid cells in liquid suspension culture using differential expression of CD34 vs. CD71 in combination with specific lineage markers. Freshly isolated human CD34+ bone marrow cells were introduced into suspension culture and monitored over a 6-d period using 3-colour flow cytometry. This is the first demonstration that differential expression of CD34 vs. CD71 can be used to simultaneously monitor differentiation of multiple haematopoietic cell lineages in liquid suspension culture, facilitating the study of cytokine-, drug- or chemical-induced alterations in haematopoietic progenitor cell differentiation in vitro. 相似文献
93.
Mark Sanford Carolyn Byrne Susan Williams Sandy Atley Jennifer Miller Heather Allin 《Revue canadienne de psychiatrie》2003,48(2):78-86
OBJECTIVE: This study assessed the feasibility and efficacy of a parent-education group for families with young children and a parent with depression. We designed the program to be readily disseminated if shown to be effective. METHOD: We recruited 44 parents with depression from clinics and family doctors in Hamilton, Ontario, and randomly assigned them to receive the parenting program or to a wait-list control group. The outcomes measured included knowledge of depression, parenting, family relationships, depression symptoms, child depressive symptoms, and functioning. We used analysis of covariance to test for posttreatment differences between experimental and control groups. RESULTS: Of the treatment group, 27% dropped out at posttreatment, and 43% by follow-up. Those who dropped out had more severe depression at baseline than did those who completed the program, and there was selective loss of parents with more severe depression in the experimental group. In intention-to-treat analyses at posttreatment, probands in the experimental group reported more improvements on family functioning, parenting sense of competence, and family and parent conflict than did control subjects. Standardized effect sizes (ES) were medium (0.4 to 0.6). When baseline depressive symptom scores were controlled in the analyses, the between-group differences were reduced, showing that selective loss of participants may have influenced the findings. CONCLUSIONS: On balance, the results are encouraging and support the further development and evaluation of the group intervention. However, the study does not provide unequivocal evidence in support of the program. Before it is transferred to other settings, the program needs further modification to improve participation by parents with more severe depression and further evaluation of its effectiveness. 相似文献
94.
95.
Interobserver variability in neonatal cranial ultrasonography 总被引:1,自引:0,他引:1
Jennifer Pinto Nigel Paneth Elias Kazam Ram Kairam Sylvan Wallenstein Walter Rose David Rosenfeld Steven Schonfeld Irving Stein Thomas Witomski 《Paediatric and perinatal epidemiology》1988,2(1):43-58
The reliability of cranial ultrasound diagnosis in the premature neonate was examined using data from an ongoing multicentre study of the epidemiology and long-term consequences of neonatal brain haemorrhage. First week ultrasound films (obtained at 4 hours, 24 hours and 7 days) from 60 study subjects were randomly selected for independent review by two groups of experienced interpreters, and results were recorded separately for observations (i.e. presence or absence of an abnormal echodense area on a film) and interpretations (i.e. presence or absence of haemorrhage or ventricular dilatation) in each hemisphere. Because of deaths in the first week of life, the total number of films examined was 138. Concordance on the presence or absence of an abnormal echodensity was examined for each individual film for three areas of interest: the germinal matrix, the ventricles and the parenchyma. Concordance on the presence or absence of haemorrhage or ventricular dilatation was examined only for the seventh-day film, or the final film prior to death. Finally, concordance was analysed with the diagnostic interpretations grouped into categories thought to differ prognostically for long-term outcome. In general, concordance was poorest for germinal matrix lesions and best for parenchymal lesions. Concordance was lower for observations made on each individual film than it was for interpretation of the final film in each case. Fifty-five of 60 cases (92%) were assigned to the same major prognostic category by both readers. Ultrasound review conferences were held periodically and there was evidence that concordance in ultrasound reading and interpretation improved during the course of the study. 相似文献
96.
97.
98.
99.
On the Importance of Age-Adjustment Methods in Ecological Studies of Social Determinants of Mortality 总被引:1,自引:0,他引:1
Objective. To illustrate the potential sensitivity of ecological associations between mortality and certain socioeconomic factors to different methods of age-adjustment.
Data Sources. Secondary analysis employing state-level data from several publicly available sources. Crude and age-adjusted mortality rates for 1990 are obtained from the U.S. Centers for Disease Control. The Gini coefficient for family income and percent of persons below the federal poverty line are from the U.S. Bureau of Labor Statistics. Putnam's (2000) Social Capital Index was downloaded from http://www.bowlingalone.com ; the Social Mistrust Index was calculated from responses to the General Social Survey, following the method described in Kawachi et al. (1997) . All other covariates are obtained from the U.S. Census Bureau.
Study Design. We use least squares regression to estimate the effect of several state-level socioeconomic factors on mortality rates. We examine whether these statistical associations are sensitive to the use of alternative methods of accounting for the different age composition of state populations. Following several previous studies, we present results for the case when only mortality rates are age-adjusted. We contrast these results with those obtained from regressions of crude mortality on age variables.
Principal Findings. Different age-adjustment methods can cause a change in the sign or statistical significance of the association between mortality and various socioeconomic factors. When age variables are included as regressors, we find no significant association between mortality and either income inequality, minority racial concentration, or social capital.
Conclusions. Ecological associations between certain socioeconomic factors and mortality may be extremely sensitive to different age-adjustment methods. 相似文献
Data Sources. Secondary analysis employing state-level data from several publicly available sources. Crude and age-adjusted mortality rates for 1990 are obtained from the U.S. Centers for Disease Control. The Gini coefficient for family income and percent of persons below the federal poverty line are from the U.S. Bureau of Labor Statistics. Putnam's (2000) Social Capital Index was downloaded from http://www.bowlingalone.com ; the Social Mistrust Index was calculated from responses to the General Social Survey, following the method described in Kawachi et al. (1997) . All other covariates are obtained from the U.S. Census Bureau.
Study Design. We use least squares regression to estimate the effect of several state-level socioeconomic factors on mortality rates. We examine whether these statistical associations are sensitive to the use of alternative methods of accounting for the different age composition of state populations. Following several previous studies, we present results for the case when only mortality rates are age-adjusted. We contrast these results with those obtained from regressions of crude mortality on age variables.
Principal Findings. Different age-adjustment methods can cause a change in the sign or statistical significance of the association between mortality and various socioeconomic factors. When age variables are included as regressors, we find no significant association between mortality and either income inequality, minority racial concentration, or social capital.
Conclusions. Ecological associations between certain socioeconomic factors and mortality may be extremely sensitive to different age-adjustment methods. 相似文献
100.
Hideto Kitano Jennifer M Young Jian Cheng Lan Wang Patricia D Hurn Stephanie J Murphy 《Journal of cerebral blood flow and metabolism》2007,27(7):1377-1386
Inhalation anesthetics are effective chemical preconditioning agents in experimental cerebral ischemia. However, previous work has been performed exclusively in male animals. We determined if there is a gender difference in ischemic outcome after isoflurane preconditioning (IsoPC), and if this sex-specific response is linked to differences in Akt phosphorylation or expression of neuronal inducible cell-death putative kinase (NIPK), a negative modulator of Akt activation. Young and middle-aged male and female mice were preconditioned for 4 h with air (sham PC) or 1.0% IsoPC and recovered for 24 h. Cortices were subdissected from preconditioned young male and female mice for measurement of Akt phosphorylation (Western blot) and NIPK mRNA (quantitative polymerase chain reaction). Additional cohorts underwent 2 h of reversible middle cerebral artery occlusion. Lastly, male and female Akt1(+/+) and Akt1(-/-) mice were studied to determine if gender differences in ischemic outcome after IsoPC is Akt1-dependent. Infarction volume was determined at 22 h reperfusion (2,3,5-triphenyltetrazolium chloride). As expected, IsoPC decreased ischemic damage as compared with sham PC in young and middle-aged male mice. In contrast, IsoPC markedly increased infarction in young female mice and had no effect in middle-aged female mice. Cortical phospho-Akt was increased by IsoPC versus sham PC only in male mice. No increase was observed in IsoPC female mice. NIPK mRNA was higher in female mice than in male mice regardless of preconditioning status. Male IsoPC neuroprotection was lost in Akt1-deficient male mice. We conclude that IsoPC is beneficial only in ischemic male brain and that sex differences in IsoPC are mediated through Akt activation and basal NIPK expression. 相似文献