全文获取类型
收费全文 | 27387篇 |
免费 | 2109篇 |
国内免费 | 60篇 |
专业分类
耳鼻咽喉 | 244篇 |
儿科学 | 1051篇 |
妇产科学 | 852篇 |
基础医学 | 3566篇 |
口腔科学 | 341篇 |
临床医学 | 4402篇 |
内科学 | 4672篇 |
皮肤病学 | 366篇 |
神经病学 | 2534篇 |
特种医学 | 595篇 |
外科学 | 2503篇 |
综合类 | 425篇 |
一般理论 | 55篇 |
预防医学 | 3875篇 |
眼科学 | 464篇 |
药学 | 1629篇 |
中国医学 | 24篇 |
肿瘤学 | 1958篇 |
出版年
2023年 | 130篇 |
2022年 | 219篇 |
2021年 | 519篇 |
2020年 | 326篇 |
2019年 | 528篇 |
2018年 | 557篇 |
2017年 | 416篇 |
2016年 | 462篇 |
2015年 | 526篇 |
2014年 | 730篇 |
2013年 | 1228篇 |
2012年 | 1741篇 |
2011年 | 1759篇 |
2010年 | 949篇 |
2009年 | 905篇 |
2008年 | 1729篇 |
2007年 | 1903篇 |
2006年 | 1741篇 |
2005年 | 1727篇 |
2004年 | 1683篇 |
2003年 | 1523篇 |
2002年 | 1498篇 |
2001年 | 310篇 |
2000年 | 283篇 |
1999年 | 287篇 |
1998年 | 386篇 |
1997年 | 303篇 |
1996年 | 274篇 |
1995年 | 247篇 |
1994年 | 240篇 |
1993年 | 210篇 |
1992年 | 202篇 |
1991年 | 176篇 |
1990年 | 223篇 |
1989年 | 176篇 |
1988年 | 196篇 |
1987年 | 180篇 |
1986年 | 159篇 |
1985年 | 206篇 |
1984年 | 190篇 |
1983年 | 165篇 |
1982年 | 213篇 |
1981年 | 178篇 |
1980年 | 168篇 |
1979年 | 120篇 |
1978年 | 131篇 |
1977年 | 112篇 |
1975年 | 107篇 |
1974年 | 105篇 |
1973年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
51.
Previously reported attenuation of skin postural vasoconstriction in women during the luteal menstrual cycle phase may be
due to a progesterone-mediated decrease in myogenic or veno-arteriolar (VAR) mechanisms. Skin perfusion was measured in the
shin and foot dorsum by Laser Doppler Fluxometry during leg dependency that increased vascular transmural pressure below (myogenic
constriction only) and above (myogenic and VAR) the 25 mmHg threshold for activation of the VAR, and during venous distension
to activate the VAR alone (cuff inflation to 50 mmHg). In six young women with normal menstrual cycles, vasoconstrictor responses
to all interventions did not differ between days 7–13 (follicular) and 18–23 (luteal) of the normal menstrual cycle when progesterone
levels were low and at their peak respectively. In eight women taking combined oral contraceptives (OC) and tested during
pill consumption days, reductions in foot skin perfusion were smaller (P = 0.05) than in the luteal phase of the normal cycle for leg dependency below (−36.9 ± 5.2% OC vs. −52.5 ± 7.8% luteal, mean ± S.E.M.)
and above (−43.7 ± 3.4% OC vs. −55.1 ± 4.8% luteal) the VAR threshold, and for venous distension (−53.1 ± 2.6% OC vs. 66.4 ± 5.5%
luteal). In women with normal menstrual cycles, impaired postural vasoconstriction may be confined to those who experience
pre-menstrual symptoms rather than a direct effect of endogenous hormones. Reduced vasoconstriction in the dependent foot
during OC use is consistent with the known vasodilator action of exogenous hormones and its long-term effects 相似文献
52.
Scott W. Powers Kelly C. Byars Monica J. Mitchell Susana R. Patton Teresa Schindler Margaret H. Zeller 《Children's Health Care》2003,32(4):297-311
This pilot study examined a behavioral treatment to increase calorie intake in toddlers with cystic fibrosis. Eight toddlers were randomly assigned to behavioral plus nutrition (BEH) or nutrition intervention (NTR) conditions. Calorie intake and weight were measured at pre- and posttreatment. The BEH group showed a trend for changes in calorie intake pre- to posttreatment (p = .07; 40% increase). Results for the BEH and NTR groups did not differ significantly. Most participants achieved weight gains consistent with normal growth. Seventy-five percent had not shown this pattern during the year prior to intervention. These results support the feasibility and potential for behavioral interventions in this age group. 相似文献
53.
Margaret J. Tango Evelyn Safaris Margarita Romanella Atousa Aminian Marina Katerelos Christine Somerwille RIek G. Tearle Martin J. Pearse Anthony J.E d'Apice 《Xenotransplantation》1997,4(1):25-33
Abstract: Transgenic expression of the human complement regulatory molecule CD59 in mice and genetic deletion of the major xenoantigen galactose α 1,3 galactose (Gal KO) each resulted in partial protection of spleen cells from lysis by human serum. These protective effects were additive when the two genetic modifications were combined. However, when the effects of these genetic modifications were examined in an ex vivo model in which mouse hearts were perfused with human plasma, it was Gal KO which was the modification which determined protection. CD59 expression alone was not protective and CD59 expression in combination with Gal knockout did not result in a significant additional increase in protection over and above that provided by Gal knockout alone. The likely explanation for this discrepancy between the in vitro and ex vivo data is that the H2-Kb promoter used to drive CD59 expression results I in substantially less expression on endothelium than on spleen cells. 相似文献
54.
The Relationship Between Daily Life Stress and Gastrointestinal Symptoms in Women with Irritable Bowel Syndrome 总被引:3,自引:0,他引:3
Rona L. Levy Kevin C. Cain Monica Jarrett Margaret M. Heitkemper 《Journal of behavioral medicine》1997,20(2):177-193
Research on irritable bowel syndrome (IBS), a functional disorder of the gastrointestinal (GI) system, has linked GI symptoms to stress. This study examined the relationship between daily stress and GI symptoms across women and within woman in IBS patients (n = 26), IBS nonpatients (IBS-NP; n = 23), and controls (n = 26), controlling for menstrual cycle phase. Women (ages 20–45) completed daily health diaries for two cycles in which they monitored daily GI symptoms and stress levels. The Life Event Survey (LES) was used as a retrospective measure of self-reported stress. The across-women analyses showed higher mean GI symptoms and stress in the IBS and IBS-NP groups relative to controls but no group differences in LES scores. The within-woman analyses found a significant and positive relationship between daily stress and daily symptoms in both the IBS-NP and the IBS groups. Controlling for menstrual cycle had no substantial impact on the results. 相似文献
55.
56.
57.
Adolf Pfefferbaum Edith V. Sullivan Margaret J. Rosenbloom Paula K. Shear Daniel H. Mathalon Kelvin O. Lim 《Psychiatry Research: Neuroimaging》1993,50(4):257-274
This cross-sectional study used a semi-automated analysis technique to quantify regional brain cerebrospinal fluid (CSF) volumes derived from computed tomography (CT) in 84 healthy men ranging from 21 to 82 years of age and 28 patients meeting Research Diagnostic Criteria for alcohol dependence. The goals were to replicate an earlier CT study of an independent sample of alcoholic and control subjects (Pfefferbaum et al., 1988a; Zipursky et al., 1988) and to compare CT assessments of brain changes with magnetic resonance imaging (MRI) assessments made in the same alcoholic patients (Pfefferbaum et al., 1992). Regional brain changes associated with normal aging were derived by regression analysis, using CT data collected from the healthy control subjects. As in the earlier CT study and in the concurrent MRI study, ventricular and sulcal CSF volumes in alcoholic patients were greater than would be expected for their age. Furthermore, the present CT study replicated the previous CT and MRI findings of a positive relationship between age and CSF volume enlargement in alcoholic patients over and above the normal age-related increase in CSF volume, suggesting greater vulnerability of the aging brain to alcohol. Comparison of CT-and MRI-derived estimates of ventricular and cortical sulcal volume revealed high correlations (>0.80). MRI and CT produced similar absolute ventricular volumes, while MRI produced larger sulcal volume estimates than did CT. The difference in sulcal volume estimate may be due to differences between CT and MRI in slice thickness and sensitivity to partial volume effects. 相似文献
58.
The epidemiology of severe injuries to children in northern Manhattan: methods and incidence rates 总被引:6,自引:0,他引:6
Leslie L. Davidson ‡ § Maureen S. Durkin‡ § Patricia O'Connor| Barbara Barlow† Margaret C. Heagarty 《Paediatric and perinatal epidemiology》1992,6(2):153-165
The epidemiology of injury incidence in inner-city children has not previously been described. This study presents the methods used and the incidence rates found for severe injury (causing hospitalisation or death) in a population of 89,000 children under age 17 years in northern Manhattan, a largely poor area of New York City. The average annual incidence rate (measured from 1983 to 1987) for severe injuries to children under 17 was 846/100,000 a year. The vast majority (79%) were classified as unintentional. Nine per cent were due to assault, 3% were self-inflicted and in an additional 9% the intention was unclear. Classified by cause, the highest incidence (per 100,000/year) was found for falls (218), vehicle-related (141, primarily pedestrian), ingestion (119) and burns (110). Guns caused 3% of the injuries (27). The death rate from injury was 18.7/100,000, 36% of which was due to homicide. In an additional 28%, intentional injury was suspected. The suicide rate was 0.4/100,000. The leading causes of injury death included guns and burns (both 2.7/100,000). Compared with childhood injury rates in predominantly rural and suburban populations, the rates reported here for northern Manhattan are higher for overall injury incidence (fatal and non-fatal) and for homicide, but lower for injury mortality not due to homicide. 相似文献
59.
60.
Alcohol and Platelet Function 总被引:3,自引:0,他引:3
Epidemiological studies have shown that moderate consumption of alcoholic beverages is inversely related to the incidence of the complications of coronary artery disease. The protective effect of ethanol may be partially attributable to an inhibitory effect of ethanol on platelets. This article summarizes the experimental observations that ethanol inhibits platelet responses to specific physiological agonists. In alcoholics, various platelet defects have been observed, but these may be influenced by metabolic factors rather than the presence of ethanol alone. The acute effects of ethanol on platelet functions both in vivo and ex vivo will be reviewed. Evidence will be presented demonstrating that ethanol added acutely in vitro inhibits phospholipase A2 in stimulated platelets. The interaction of ethanol with other signal transduction pathways will also be discussed. 相似文献