全文获取类型
收费全文 | 6237篇 |
免费 | 453篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 38篇 |
儿科学 | 199篇 |
妇产科学 | 187篇 |
基础医学 | 735篇 |
口腔科学 | 88篇 |
临床医学 | 836篇 |
内科学 | 1121篇 |
皮肤病学 | 60篇 |
神经病学 | 550篇 |
特种医学 | 136篇 |
外科学 | 938篇 |
综合类 | 105篇 |
一般理论 | 28篇 |
预防医学 | 805篇 |
眼科学 | 65篇 |
药学 | 401篇 |
中国医学 | 8篇 |
肿瘤学 | 406篇 |
出版年
2023年 | 71篇 |
2022年 | 124篇 |
2021年 | 299篇 |
2020年 | 137篇 |
2019年 | 250篇 |
2018年 | 270篇 |
2017年 | 165篇 |
2016年 | 146篇 |
2015年 | 154篇 |
2014年 | 220篇 |
2013年 | 309篇 |
2012年 | 420篇 |
2011年 | 470篇 |
2010年 | 212篇 |
2009年 | 196篇 |
2008年 | 311篇 |
2007年 | 275篇 |
2006年 | 261篇 |
2005年 | 276篇 |
2004年 | 234篇 |
2003年 | 192篇 |
2002年 | 184篇 |
2001年 | 94篇 |
2000年 | 97篇 |
1999年 | 68篇 |
1998年 | 45篇 |
1997年 | 26篇 |
1996年 | 28篇 |
1995年 | 35篇 |
1994年 | 35篇 |
1993年 | 31篇 |
1992年 | 63篇 |
1991年 | 71篇 |
1990年 | 78篇 |
1989年 | 66篇 |
1988年 | 59篇 |
1987年 | 53篇 |
1986年 | 62篇 |
1985年 | 42篇 |
1984年 | 30篇 |
1983年 | 28篇 |
1982年 | 25篇 |
1980年 | 26篇 |
1979年 | 41篇 |
1978年 | 35篇 |
1977年 | 25篇 |
1976年 | 29篇 |
1971年 | 30篇 |
1970年 | 35篇 |
1967年 | 27篇 |
排序方式: 共有6706条查询结果,搜索用时 25 毫秒
71.
A population-based study of the relationship between salt intake, bone resorption and bone mass 总被引:5,自引:0,他引:5
Jones G Beard T Parameswaran V Greenaway T von Witt R 《European journal of clinical nutrition》1997,51(8):561-565
OBJECTIVE: To explore the relationship between urinary sodium (the best measure of salt intake), urinary calcium, urinary deoxypyridinoline (DPYR) and bone mass. DESIGN: Cross-sectional study. SETTING: Population based sample of healthy Hobart residents. SUBJECTS: One hundred and fifty-four (M = 34, F = 120) subjects invited to take part from a systematic sample of the electoral roll and a single newspaper advertisement. RESULTS: In both sexes, urinary sodium correlated moderately with urinary DPYR (r = 0.32, P < 0.0001) and urinary calcium (r = 0.37, P < 0.0001). In multivariate analysis, the combination of urinary sodium, total body bone area, age and sex explained 22% of the variation in log-transformed DPYR (P < 0.00001). In univariate analysis, both urinary sodium and urinary DPYR were strongly associated with bone mineral content and bone mineral density at all sites but this association disappeared after adjustment for confounders particularly body weight. CONCLUSIONS: This study has shown that salt intake is associated with markers of bone resorption in a population-based sample of males and females and appears likely to be a risk factor for osteoporosis despite the lack of a demonstrable association between bone mass and a single measure of urinary sodium excretion. Further studies are needed to define the effect of salt intake on bone mass and fractures more clearly. These studies will need to be either longitudinal or interventional in design with repeated measures of urinary sodium so that habitual sodium intake can be accurately assessed and regression dilution bias can be minimised. 相似文献
72.
Sautter FJ Brailey K Uddo MM Hamilton MF Beard MG Borges AH 《Journal of traumatic stress》1999,12(1):73-88
Symptoms of posttraumatic stress disorder (PTSD), psychosis, general psychopathology, role functioning, violence potential, and cognitive and emotional aspects of psychotic states were compared in three groups of veterans. Groups were defined on the basis of their DSM-IV diagnoses: Psychotic disorder and war-related PTSD, war-related PTSD without psychotic symptoms, and psychotic disorder without PTSD. Veterans with PTSD and a comorbid psychotic disorder showed significantly higher levels of positive symptoms of psychosis, general psychopathology, paranoia, and violent thoughts, feelings, and behaviors than the other two groups. These data show that patients with comorbid PTSD and psychotic disorder show levels of cognitive, emotional, and behavioral disturbance that far exceed the levels of disturbance seen in patients with PTSD without psychosis or in patients with psychotic disorder. 相似文献
73.
Malecki EA Cook BM Devenyi AG Beard JL Connor JR 《Journal of the neurological sciences》1999,170(2):112-118
Hypotransferrinemia (hpx/hpx) is a genetic defect in mice resulting in <1% of normal plasma transferrin (Tf) concentrations; heterozygotes for this mutation (+/hpx) have low circulating Tf concentrations. These mice provide a unique opportunity to examine the role of Tf in Fe and Mn transport in the brain. Twenty weanling wild-type BALB/cJ mice, 15 +/hpx mice, and 12 hpx/hpx mice of both sexes were injected i.v. with either 54MnCl(2) or 59FeCl(3) either 1 h or 1 week before killing at 12 weeks of age. Total brain counts of 54Mn and 59Fe were measured, and regional brain distributions were assessed by autoradiography. Hypotransferrinemia did not affect total brain Mn uptake. However, 1 week after i.v. injection, hpx/hpx mice had less 54Mn in forebrain structures including cerebral cortex, corpus callosum, striatum, and substantia nigra. The +/hpx mice had the highest total brain 59Fe accumulation 1 h after i.v. injection. A striking effect of regional distribution of 59Fe was noted 1 week after injection; in hpx/hpx mice, 59Fe was located primarily in choroid plexus, whereas in +/+ and +/hpx mice 59Fe was widely distributed, with relatively high amounts in cerebral cortex and cerebellum. We interpret these data to mean that Tf is necessary for the transport of Fe but not Mn across the blood-brain barrier, and that there is a Tf-independent uptake mechanism for iron in the choroid plexus. Additionally, these data suggest that endogenous synthesis of Tf is necessary for Fe transport from the choroid plexus. 相似文献
74.
The mechanism of Ara-C-induced apoptosis of differentiating cerebellar granule neurons 总被引:3,自引:0,他引:3
Neurotoxicity is one of the side-effects of the therapeutically useful antitumour agent, Ara-C (or 1-beta-d-arabinofuranosyl-cytosine, cytarabine). This agent is also reported to induce cell death of cultured neurons. In this study, we show that Ara-C-induced death of differentiating rat cerebellar granule neurons is prevented by cycloheximide at concentrations corresponding to its action in preventing protein synthesis. The death is accompanied by cleavage of the caspase substrate poly ADP ribose polymerase (PARP) and c-Abl-dependent activation of the stress-activated protein kinases c-Jun N-terminal kinase and p38. However, c-Jun levels do not rise and the activation of the stress-activated protein kinases is not required for this form of neuronal death. Cyclin-dependent kinase (cdk) activity and inappropriate cell-cycle re-entry have been implicated in some forms of death in differentiated neurons. Here we show that Ara-C-induced death of cerebellar granule neurons is prevented by an inhibitor of cdk4, whereas inhibition of cdk1, -2 and -5 mimics the death, and non-cdk4/6 cdks are inhibited by Ara-C treatment. Cdk1 and -2 are dramatically down-regulated during neuronal differentiation, and neither Ara-C nor inhibition of these cdks induces death in mature neurons. This mechanism could also play a significant role in the neurotoxicity associated with the therapeutic use of Ara-C, as cdk levels can be upregulated in stressed neurons of adult brain. We propose that the balance between cdk4/6 and cdk1/2/5 activity may determine the survival of early differentiating neurons, and that DNA-damaging agents may induce neuronal death by inhibiting cdk1/2/5 under conditions which require these activities for survival. 相似文献
75.
J A Brennan A K Walsh J D Beard A A Bolia P R Bell 《European journal of vascular surgery》1991,5(1):13-17
A prospective vein graft screening programme was established in order to improve graft patency in the period 1-12 months after operation. Patient assessment consisted of ankle:brachial pressure index (ABPI) measurement before and after exercise, and Duplex scanning. Thirty-nine grafts have been followed up, with 19 stenoses detected in 18 grafts (46%) using Duplex. Of these 18 grafts, six had a serial fall in resting ABPI, median 0.14 (range 0.11-0.33), and nine had a post-exercise ABPI fall, median 0.19 (range 0.13-0.4). The remaining three had a normal ABPI but were unable to exercise. Fifteen grafts have been treated, 12 by percutaneous transluminal angioplasty (PTA), and three by surgery. One stenosis treated with PTA recurred within 3 months and was repaired with a vein patch. Since screening was implemented no grafts in the programme have occluded. This study indicates that simple ABPI measurements can be used to screen "at risk" grafts for evaluation with Duplex scanning, without jeopardising graft patency. 相似文献
76.
77.
Effect of a cognitive behavioral intervention on reducing symptom severity during chemotherapy. 总被引:4,自引:0,他引:4
Charles Given Barbara Given Mohammad Rahbar Sangchoon Jeon Ruth McCorkle Bernadine Cimprich Andrzej Galecki Sharon Kozachik Albert Brady Mary Jo Fisher-Malloy Kathy Courtney Elizabeth Bowie 《Journal of clinical oncology》2004,22(3):507-516
PURPOSE: To describe a randomized trial of a cognitive behavioral intervention on reducing symptom severity among patients diagnosed with solid tumors and undergoing a first course of chemotherapy and to determine whether the intervention had an additive or interactive effect on symptom severity in the presence of supportive care medications. PATIENTS AND METHODS: Patients (N = 237) were accrued from comprehensive and community cancer centers, interviewed, and randomly assigned to either the experimental intervention (n = 118) or conventional care (n = 119). A symptom severity index, based on summed severity scores across 15 symptoms, was the primary outcome. Each patient's site of cancer, stage at diagnosis, chemotherapy protocols, and use of supportive medications were learned from medical records. RESULTS: Groups were equivalent at baseline, and attrition by characteristics by group was not different. The proportion of patients not receiving chemotherapy at 10 and 20 weeks did not differ by group. At the 10- and 20-week observations, there was a significant interaction between the experimental group and baseline symptom severity. Patients in the experimental group who entered the trial with higher symptom severity reported significantly lower severity at 10 and 20 weeks. Controlling for chemotherapy treatment status at follow-up and supportive care medications did not alter the effect of the experimental intervention. CONCLUSION: Compared with conventional care alone, the experimental intervention was effective among patients who entered the trial with higher levels of symptom severity. Age, sex, site or stage of cancer, and supportive medications did not modify the effect of this cognitive behavioral intervention on symptom severity. 相似文献
78.
James A Talcott Judithy Manola Jack A Clark Irving Kaplan Clair J Beard Sonya P Mitchell Ronald C Chen Michael P O'Leary Philip W Kantoff Anthony V D'Amico 《Journal of clinical oncology》2003,21(21):3979-3986
PURPOSE: Understanding the distinctive patterns of treatment-related dysfunction after alternative initial treatments for early prostate cancer (PC) may improve patients' choice of treatment and later help them adjust to its consequences. We characterized the time course of treatment complications while adjusting for potentially confounding pretreatment factors hindering other observational studies. PATIENTS AND METHODS: In a prospective cohort study of 417 men we assessed urinary, bowel, and sexual function from before primary treatment to 24 months after. To control for potential confounding, we measured sociodemographic and PC prognostic factors, medical comorbidity, and pretreatment function commonly affected by PC and its treatment. RESULTS: Patients who underwent external beam radiotherapy (EBRT), radical prostatectomy (RP), and brachytherapy (BT) differed significantly in sociodemographic factors, cancer prognostic factors, and pretreatment symptom status, especially sexual function. Urinary incontinence increased sharply after RP, while bowel problems and urinary irritation/obstruction rose after EBRT and BT. Sexual dysfunction increased in all patients, particularly after radical prostatectomy, and nerve-sparing surgical technique had little apparent benefit. There was no change in urinary function and little change in overall bowel function after 12 months, but the time course of sexual dysfunction varied by treatment and, for bowel function, by symptom. Multiple regression modeling confirmed that treatment influences all 24-month outcomes, but residual confounding persisted. CONCLUSION: Pretreatment function and the primary treatment modality for early stage PC strongly predict the affected organ systems and time course of dysfunction. With this information, patients and their physicians may refine their choice of treatment and better anticipate its consequences. 相似文献
79.
80.
Kinetic analysis shows that iron deficiency decreases liver vitamin A mobilization in rats 总被引:2,自引:0,他引:2
In view of evidence that nutritional status of iron and vitamin A may affect the other nutrient's metabolism, we used model-based compartmental analysis to examine effects of iron deficiency on whole-body vitamin A dynamics in rats. Weanling male Sprague-Dawley rats were fed the AIN93G diet with 2.5 nmol retinyl palmitate/g and either 45 [control (CN)] or 4 microg/g Fe [iron-deficient (ID)] for 8 wk. ID rats consumed food ad libitum; CN rats were food-restricted so that their body weights were the same as ID rats. Two rats/group were killed; liver vitamin A was determined and used for vitamin A balance calculations. [(3)H]Retinol-labeled plasma was administered intravenously to remaining rats, and 27 serial blood samples were collected for 7 wk. At killing, plasma vitamin A was 0.52+/-0.12 (ID, n = 5) vs. 1.34+/-0.12 micromol/L (CN, n = 6; P<0.001), and liver vitamin A was 809+/-94 (ID) vs. 112+/-24 nmol (CN, P<0.001). Plasma tracer data were fit to a three- or four-compartment model using the Simulation, Analysis and Modeling computer program and kinetic parameters were calculated. Vitamin A transfer rate between the retinyl ester storage pool [14+/-3 (ID) vs. 24+/-4 nmol/d (CN), P<0.05] and plasma was lower in ID rats. Vitamin A remained longer in the body [44+/-11 (ID) vs. 22+/-3 d (CN), P<0.05]. Adjusted mean disposal rate was lower in ID (10.0) than CN rats (19.9 nmol/d), as was estimated vitamin A absorption efficiency [58% (ID) vs. 76% (CN)]. Our results suggest that iron deficiency inhibits mobilization of vitamin A stores and may decrease the absorption and irreversible utilization of vitamin A. 相似文献