收费全文 | 31670篇 |
免费 | 3605篇 |
国内免费 | 767篇 |
耳鼻咽喉 | 294篇 |
儿科学 | 879篇 |
妇产科学 | 446篇 |
基础医学 | 1869篇 |
口腔科学 | 338篇 |
临床医学 | 2848篇 |
内科学 | 3120篇 |
皮肤病学 | 763篇 |
神经病学 | 859篇 |
特种医学 | 3915篇 |
外国民族医学 | 21篇 |
外科学 | 2984篇 |
综合类 | 3850篇 |
现状与发展 | 3篇 |
预防医学 | 3089篇 |
眼科学 | 375篇 |
药学 | 3603篇 |
26篇 | |
中国医学 | 823篇 |
肿瘤学 | 5937篇 |
2024年 | 64篇 |
2023年 | 490篇 |
2022年 | 935篇 |
2021年 | 1284篇 |
2020年 | 1173篇 |
2019年 | 1197篇 |
2018年 | 1260篇 |
2017年 | 1213篇 |
2016年 | 1305篇 |
2015年 | 1309篇 |
2014年 | 2497篇 |
2013年 | 2835篇 |
2012年 | 2035篇 |
2011年 | 2203篇 |
2010年 | 1648篇 |
2009年 | 1464篇 |
2008年 | 1515篇 |
2007年 | 1390篇 |
2006年 | 1201篇 |
2005年 | 1075篇 |
2004年 | 897篇 |
2003年 | 823篇 |
2002年 | 707篇 |
2001年 | 637篇 |
2000年 | 508篇 |
1999年 | 467篇 |
1998年 | 401篇 |
1997年 | 371篇 |
1996年 | 342篇 |
1995年 | 274篇 |
1994年 | 233篇 |
1993年 | 213篇 |
1992年 | 180篇 |
1991年 | 206篇 |
1990年 | 165篇 |
1989年 | 190篇 |
1988年 | 143篇 |
1987年 | 139篇 |
1986年 | 131篇 |
1985年 | 176篇 |
1984年 | 154篇 |
1983年 | 96篇 |
1982年 | 121篇 |
1981年 | 75篇 |
1980年 | 77篇 |
1979年 | 70篇 |
1978年 | 26篇 |
1977年 | 45篇 |
1976年 | 34篇 |
1975年 | 18篇 |
Background Context
Low back pain (LBP) is a common complaint in clinical practice of multifactorial origin. Although obesity has been thought to contribute to LBP primarily by altering the distribution of mechanical loads on the spine, the additional contribution of obesity-related conditions such as diabetes mellitus (DM) to LBP has not been thoroughly examined.Purpose
To determine if there is a relationship between DM and LBP that is independent of body mass index (BMI) in a large cohort of adult survey participants.Study Design
Retrospective analysis of prospectively collected National Health and Nutrition Examination Survey (NHANES) data to characterize associations between LBP, DM, and BMI in adults subdivided into 6 subpopulations: normal weight (BMI 18.5–25), overweight (BMI 25–30), and obese (BMI >30) diabetics and nondiabetics. Diabetes was defined with glycohemoglobin A1c (HbA1c) ≥6.5%.Patient Sample
11,756 participants from NHANES cohort.Outcome Measures
Percentage of LBP reported.Methods
LBP reported in the 1999-2004 miscellaneous pain NHANES questionnaire was the dependent variable examined. Covariates included HbA1c, BMI, age, and family income ratio to poverty as continuous variables as well as race, gender, and smoking as binary variables. Individuals were further subdivided by weight class and diabetes status. Regression and graphical analyses were performed on the study population as a whole and also on subpopulations.Results
Increasing HbA1c did not increase the odds of reporting LBP in the full cohort. However, multivariate logistic regression of the 6 subpopulations revealed that the odds of LBP significantly increased with increasing HbA1c levels in normal weight diabetics. No other subpopulations reported significant relationships between LBP and HbA1c. LBP was also significantly associated with BMI for normal weight diabetics and also for obese subjects regardless of their DM status.Conclusions
LBP is significantly related to DM status, but this relationship is complex and may interact with BMI. These results support the concept that LBP may be improved in normal weight diabetic subjects with improved glycemic control and weight loss, and that all obese LBP subjects may benefit from improved weight loss alone. 相似文献Methods: Tumour and surrounding tissue were modeled by elliptical two- and three-dimensional computational phantoms having six different nanoparticle distributions. Nanoparticles were modeled as point heat sources having amplitude-dependent loss power. The total number of nanoparticles was fixed, and their spatial distribution and heat output were varied. Heat transfer was computed by solving the Pennes’ bioheat equation using finite element methods (FEM) with temperature-dependent blood perfusion. Local temperature was regulated using a proportional-integral-derivative (PID) controller. Tissue temperature, thermal dose and tissue damage were calculated. The required minimum thermal dose delivered to the tumor was kept constant, and heating power was adjusted for comparison of both the heating methods.
Results: Modulated power heating produced lower and more homogeneous temperature distributions than did constant power heating for all studied nanoparticle distributions. For a concentrated nanoparticle distribution, located off-center within the tumor, the maximum temperatures inside the tumor were 16% lower for modulated power heating when compared to constant power heating. This resulted in less damage to surrounding normal tissue. Modulated power heating reached target thermal doses up to nine-fold more rapidly when compared to constant power heating.
Conclusions: Controlling the temperature at the tumor-healthy tissue boundary by modulating the heating power of magnetic nanoparticles demonstrably compensates for a variable nanoparticle distribution to deliver effective treatment. 相似文献
Methods: Using the Schedule for Clinical Assessment in Neuropsychiatry, tedium vitae was assessed in 130 stroke survivors attending rehabilitation in a large Nigerian university hospital. Global cognitive and executive dysfunctions were evaluated, respectively, using the Mini Mental State Examination and the modi?ed Indiana University Token test. All participants had their index stroke 3 to 24 months before recruitment into the study. We also examined a comparative group of 130 age, gender, and education matched apparently normal persons who were unrelated to the stroke survivors. Associations were explored using univariate and multivariate logistic regression analyses.
Results: Tedium vitae was experienced by 16 (12.3%) stroke survivors compared with 5 (3.9%) in the comparative group (O. R = 3.5, 95% C. I = 1.3–9.9, p = 0.018). Among stroke survivors, those who were retired were more likely to experience tedium vitae (56.2%, p = 0.045). In analyses adjusting for the effect of systemic hypertension, cognitive dysfunction, retirement and marital separation, there was a 3.5-fold increase in the odds of experiencing tedium vitae after surviving a stroke (O. R = 3.5, 95% C. I = 1.1–11.6, p = 0.042).
Conclusions: Tedium vitae is a common suicidal experience after stroke and may be among the earliest perceptible pointer to impending poststroke suicide. It is easy to assess and may be less costly to obtain an adequate sample size in studies aiming to understand the phenomenon of suicide in the stroke population. 相似文献