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   670篇
  免费   73篇
  国内免费   3篇
耳鼻咽喉   7篇
儿科学   6篇
妇产科学   1篇
基础医学   63篇
口腔科学   10篇
临床医学   62篇
内科学   179篇
皮肤病学   8篇
神经病学   86篇
特种医学   21篇
外科学   60篇
综合类   12篇
一般理论   1篇
预防医学   92篇
眼科学   33篇
药学   67篇
中国医学   7篇
肿瘤学   31篇
  2023年   10篇
  2022年   32篇
  2021年   51篇
  2020年   24篇
  2019年   32篇
  2018年   30篇
  2017年   23篇
  2016年   27篇
  2015年   27篇
  2014年   26篇
  2013年   27篇
  2012年   44篇
  2011年   47篇
  2010年   6篇
  2009年   22篇
  2008年   23篇
  2007年   18篇
  2006年   33篇
  2005年   18篇
  2004年   21篇
  2003年   13篇
  2002年   17篇
  2000年   9篇
  1999年   5篇
  1995年   3篇
  1994年   6篇
  1992年   10篇
  1991年   10篇
  1990年   10篇
  1989年   11篇
  1988年   5篇
  1987年   11篇
  1986年   5篇
  1985年   10篇
  1984年   7篇
  1983年   5篇
  1982年   7篇
  1981年   3篇
  1979年   5篇
  1978年   3篇
  1977年   5篇
  1976年   3篇
  1975年   3篇
  1973年   6篇
  1972年   3篇
  1970年   2篇
  1969年   2篇
  1968年   3篇
  1967年   3篇
  1966年   2篇
排序方式: 共有746条查询结果,搜索用时 15 毫秒
731.
AIM: To study whether N-acetyltransferase 2 (NAT2) genotypes and phenotypes are associated with increased risk factor for gastric cancer in Omani patients and to study the clinico-pathological correlations and the prognostic signifi cance of NAT2.METHODS: Genomic DNA was extracted from peripheral blood of 100 gastric cancer patients and 100 control subjects. NAT2 genotyping was performed using DNA sequencing. The prognostic significance of NAT2 and other clinicopathological features was assessed by univariate and multivariate analyses.RESULTS: We observed no significant association between NAT2 genotypes and phenotypes and gastric cancer risk. The NAT2 phenotype polymorphisms and gastric cancer risk predisposition were not modified by concomitant H pylori infection and smoking. There was no significant association between NAT2 and clinicopathological features, and NAT2 had no independent prognostic signifi cance.CONCLUSION: In the current study, NAT2 genotypes and phenotypes are not associated with gastric cancer risk predisposition. Moreover NAT2 phenotypes had no clinicopathological associations or prognostic signif icance.  相似文献   
732.
Among hemorheologic parameters, plasma viscosity is one of the most studied in epidemiology, so that it has emerged as an independent risk factor. In diabetes, plasma viscosity is frequently elevated. For this reason we tried to define characteristics of non-insulin dependent diabetics with high plasma viscosity (>1.45 mPa.s) and whether they were more insulin resistant and/or exhibited other hemorheologic disturbances. 12 subjects (age 56.1+/-11.7; BMI 28.6+/-4.8) were thus found to have a value of plasma viscosity >1.45 mPa.s. They were compared to 20 age and BMI-matched NIDDMs. Patients have similar insulin sensitivity, HbA1c, and fibrinogen. RBC aggregation, rigidity and hematocrit were not significantly different. Whole blood viscosity at high shear rate was slightly higher (p=0.05). When corrected for hematocrit whole blood viscosity is no longer different. However, hematocrit was not lower in subjects with hpl >1.45. By contrast blood pressure was markedly higher (systolic: 177.5+/-2.5 mmHg vs 140+/-8 mmHg, p<10(-8); diastolic 110+/-14 vs 83+/-9 mmHg, p<10(-9); mean 132+/-18 mmHg vs 102+/-7 mmHg p<10(-9)). Therefore, in NIDDM, higher plasma viscosity, regardless insulin resistance and adiposity, is strongly related to blood pressure.  相似文献   
733.
In comparison to the general population, individuals with diabetes suffer a 3- to 4-fold increased risk for developing complications of atherosclerosis and vascular insufficiency. This fact should be taken into account to develop a suitable determinant for the early detection of these complications and subsequently reduce the adverse effect of type 2 diabetes. In vitro experiments have shown that the products of glucose auto-oxidation and Amadori adducts are both potential sources of Nε-(carboxymethyl)lysine (CML). Excessive formation of CML on low density lipoprotein (LDL) has been proposed to be an important mechanism for the dyslipidemia and accelerated atherogenesis observed in patients with type 2 diabetes. It has been postulated that the uptake of CML-LDL by LDL receptors is impaired, thereby decreasing its clearance from the blood circulation. Alternatively, the uptake of these modified LDL particles by scavenger receptors on macrophages and vascular smooth muscle cells (SMCs) and by AGE receptors on endothelial cells, SMCs, and monocytes is highly enhanced and this, in turn, is centrally positioned to contribute to the pathogenesis of diabetic vascular complications especially coronary artery disease. The present review summarizes the up-to-date information on effects and mechanism of type 2 diabetes-associated coronary atherosclerosis induced by CML-LDL modification.  相似文献   
734.
CONTEXT: Polycystic ovary syndrome (PCOS) represents the most common endocrine abnormality in women of reproductive age. The cause of PCOS remains largely unknown, but studies suggest an intrinsic ovarian abnormality. OBJECTIVE: The objective of the study was to test our hypothesis that differences in granulosa cell proliferation and apoptosis may underlie abnormalities that affect follicular development. DESIGN: Granulosa cells were prepared from follicular fluid aspirated from 4- to 8-mm follicles of unstimulated ovaries during routine laparoscopy or laparotomy from women with anovulatory PCOS and those with regular ovulatory cycles. SETTING: The study was conducted at a university hospital. PATIENTS: Fourteen women with anovulatory PCOS and nine women with regular ovulatory cycles participated in the study. MAIN OUTCOME MEASURES: Immunocytochemistry on granulosa cells to investigate apoptotic and proliferation rates, together with real-time RT-PCR to analyze gene expression profiles of apoptotic regulators, was measured. RESULTS: Significantly lower apoptotic rates were found in granulosa cells from patients with PCOS, compared with women with regular ovulatory cycles (P=0.004). Lower apoptotic rates were associated with decreased levels of the apoptotic effector caspase-3 (P=0.001) and increased levels of the anti-apoptotic survival factor cellular inhibitor of apoptosis proteins-2 in the PCOS group that were coupled to higher proliferation rates (P=0.032). Gene expression profiling confirmed the immunocytochemical findings. CONCLUSIONS: Our findings indicate that there are significant differences in the rate of cell death and proliferation in granulosa cell populations in PCOS patients. These are associated with decreased expression of apoptotic effectors and increased expression of a cell survival factor. These results provide new insights that may be useful in developing specific therapeutic intervention strategies in PCOS.  相似文献   
735.

Aim

To report the national prevalence of metabolic syndrome (MetS) and its risk factors among adult Malaysians (>18 years old) based on World Health Organization (WHO), the National Cholesterol Education Program Expert Panel III (ATP III), International Diabetes Federation (IDF) and the ‘Harmonized’ criteria.

Methods

A multi-stage stratified sampling method was used to select 4341 subjects from Peninsular and East Malaysia. Subjects underwent physical and clinical examinations.

Results

Based on the WHO, ATP III, IDF and Harmonized definitions, the overall crude prevalences of MetS were 32.1, 34.3, 37.1 and 42.5%, respectively. Regardless of the criteria used, MetS was higher in urban areas, in females, in the Indian population and increased significantly with age. Risk factors also increased with age; abdominal obesity was most prevalent (57.4%), was higher in females (64.2%) and was highest in Indians (68.8%). Hypertension was higher in males (56.5%) and highest among Malaysians (52.2%). In contrast, the Chinese had the highest prevalence of hypertriglyceridaemia (47.4%).

Conclusions

Malaysia has a much higher prevalence of MetS compared with other Asian countries and, unless there is immediate intervention to reduce risk factors, this may pose serious implications on the country's healthcare costs and services.  相似文献   
736.
To develop an ultra-sensitive and selective NOx gas sensor with an ultra-low detection limit, expanded graphite/NiAl layered double hydroxide (EG/NA) nanowires were synthesized by using hydrothermal method with EG as a template and adjusting the amount of urea in the reaction. X-ray diffraction and transmission electron microscopy showed EG/NA3 nanowires with a diameter of 5–10 nm and a length greater than 100 nm uniformly dispersed on the expanded graphite nanosheet (>8 layers). The synergy between NiAl layered double hydroxide (NiAl-LDH) and expanded graphite (EG) improved the gas sensing properties of the composites. As expected, gas sensing tests showed that EG/NA composites have superior performance over pristine NiAl-LDH. In particular, the EG/NA3 nanowire material exhibited an ultra-high response (Ra/Rg = 17.65) with ultra-fast response time (about 2 s) to 100 ppm NOx, an ultra-low detection limit (10 ppb) and good selectivity at room temperature (RT, 24 ± 2 °C), which could meet a variety of application needs. Furthermore, the enhancement of the sensing response was attributed to the nanowire structure formed by NiAl-LDH in the EG interlayer and the conductive nanonetwork of interwoven nanowires.

Expanded graphite/NiAl-LDH nanowires for ultra-sensitive, ultra-low detection limits and selective NOx gas detection at room temperature.  相似文献   
737.
738.
The present study focuses on fabrication of magnetic activated carbon (M-AC) using tire waste and its potential investigation for adsorption of Cr (VI) from wastewater. The composite material (M-AC) was synthesized by pyrolysis followed by in situ magnetization method, and characterized by FTIR, FESEM, EDX, and XRD analysis. The maximum adsorption of Cr (VI) ion over composite adsorbent was found (~99.5%) to occur at pH 2, sample volume 10 mL, adsorbent dose 100 mg, contact time 30 min. The adsorption process was endothermic, feasible, spontaneous, and was found to follow pseudo second order of the reaction. The Cr ion could be completely desorbed (~99.3%) from the composite adsorbent by using 20 mL of 2 M NaOH solution. The composite adsorbent was regenerated by continuous adsorption and desorption for 5 consecutive cycles by using 10 mL 0.1 M HCl solution. M-AC also performed well in case of tannery wastewater by removing about 97% of Cr (VI).  相似文献   
739.
This study evaluated the cytotoxicity of methacrylate‐based resins containing dimethyl sulfoxide (DMSO). DMSO was incorporated into hydrophobic (R2) and hydrophilic (R5) resins at weight concentrations of 0, 0.01, 0.1, 1, 5, or 10 w/w %. Resin discs (n = 10/group) were prepared. Human gingival fibroblasts (HGF‐1) were exposed to resin eluates for 24 h. Furthermore, dentin barrier test was performed using 3‐D cultures of odontoblast‐like cells (SV40 transfected pulp derived cells) with dentin slices of 400 µm thickness (n = 8). After acid etching of dentin, DMSO‐modified resins were applied into the cavity part of the device and light‐cured for 20 s. Cell viability (%) was assessed by MTT and analyzed spectrometrically. Data were analyzed by ANOVA and Tukey test (α = 0.05). Resin eluates showed statistically significantly lower % cell viability for all neat and DMSO‐modified resins than seen for the negative control. Moreover, DMSO‐R5 eluates resulted in significantly lower % cell viability than DMSO‐R2 emulates. The dentin barrier test showed that DMSO‐R2 did not result in significantly lower % cell viability, whereas incorporation of 1‐10 w/w % DMSO into R5 resulted in significantly lower % of cell viability. Incorporating DMSO into hydrophilic self‐etching resins may increase cytotoxicity. The biocompatibility is not influenced by the addition of DMSO into hydrophobic resin.  相似文献   
740.
Objective—To determine the relations of plasma levels of brain natriuretic peptide (BNP), atrial natriuretic factor (ANF), N-terminal ANF (N-ANF), cyclic guanosine monophosphate (cGMP; the cardiac peptide second messenger), and plasma catecholamines to left ventricular function and to prognosis in patients admitted with acute myocardial infarction.
Design—Plasma hormones and ventricular function (radionuclide ventriculography) were measured 1-4 days after myocardial infarction in 220 patients admitted to a single coronary care unit. Radionuclide scanning was repeated 3-5 months after infarction. Clinical events were recorded over a mean period of 14 months.
Results—Both early and late left ventricular ejection fraction (LVEF) were most closely related to plasma BNP (r = −0.60, n = 220, p < 0.001; and r = −0.53, n = 192, p < 0.001, respectively), followed by ANF, N-ANF, cGMP, and the plasma catecholamines. Early plasma BNP concentrations less than twofold the upper limit of normal (20 pmol/l) had 100% negative predictive value for LVEF < 40% at 3-5 months after infarction. In multivariate analysis incorporating all the neurohormonal factors, only BNP remained independently predictive of LVEF < 40% (p < 0.005). Survival analysis by median levels of candidate predictors identified BNP as the most powerful discriminator for death (p < 0.0001). No early deaths (within 4 months) occurred in patients with plasma BNP concentrations below the group median (27 pmol/l), and over follow up only three of 26 deaths occurred in this subgroup. Of all episodes of left ventricular failure, 85% occurred in patients with plasma BNP above the median (p < 0.001). In multivariate analyses, BNP alone gave additional predictive information beyond sex, age, clinical history, LVEF, and plasma noradrenaline for both subsequent onset of LVF and death.
Conclusions—Plasma BNP measured within 1-4 days of acute myocardial infarction is a powerful independent predictor of left ventricular function, heart failure, or death over the subsequent 14 months, and superior to ANF, N-ANF, cGMP, and plasma catecholamines.

Keywords: cardiac natriuretic peptides; noradrenaline; myocardial infarction; heart failure  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