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   539篇
  免费   42篇
耳鼻咽喉   3篇
儿科学   19篇
妇产科学   15篇
基础医学   81篇
口腔科学   4篇
临床医学   50篇
内科学   90篇
皮肤病学   3篇
神经病学   86篇
特种医学   5篇
外科学   45篇
综合类   2篇
预防医学   61篇
眼科学   11篇
药学   47篇
中国医学   5篇
肿瘤学   54篇
  2024年   5篇
  2023年   20篇
  2022年   17篇
  2021年   29篇
  2020年   35篇
  2019年   36篇
  2018年   29篇
  2017年   20篇
  2016年   27篇
  2015年   26篇
  2014年   18篇
  2013年   34篇
  2012年   46篇
  2011年   44篇
  2010年   22篇
  2009年   14篇
  2008年   32篇
  2007年   26篇
  2006年   12篇
  2005年   16篇
  2004年   18篇
  2003年   9篇
  2002年   10篇
  2001年   2篇
  2000年   2篇
  1999年   1篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1984年   1篇
  1982年   2篇
  1980年   2篇
  1978年   1篇
  1976年   3篇
  1975年   1篇
  1971年   1篇
  1970年   1篇
  1969年   1篇
  1968年   1篇
  1966年   1篇
  1965年   1篇
  1961年   1篇
  1951年   1篇
  1950年   1篇
  1924年   1篇
  1923年   1篇
排序方式: 共有581条查询结果,搜索用时 15 毫秒
41.
Raul Zamora-Ros  Valerie Cayssials  Mazda Jenab  Joseph A. Rothwell  Veronika Fedirko  Krasimira Aleksandrova  Anne Tjønneland  Cecilie Kyrø  Kim Overvad  Marie-Christine Boutron-Ruault  Franck Carbonnel  Yahya Mahamat-Saleh  Rudolf Kaaks  Tilman Kühn  Heiner Boeing  Antonia Trichopoulou  Elissavet Valanou  Effie Vasilopoulou  Giovanna Masala  Valeria Pala  Salvatore Panico  Rosario Tumino  Fulvio Ricceri  Elisabete Weiderpass  Torkjel M. Sandanger  Cristina Lasheras  Antonio Agudo  Maria-Jose Sánchez  Pilar Amiano  Carmen Navarro  Eva Ardanaz  Emily Sonestedt  Bodil Ohlsson  Lena Maria Nilsson  Martin Rutegård  Bas Bueno-de-Mesquita  Kay-Thee Khaw  Nicholas J. Wareham  Kathryn Bradbury  Heinz Freisling  Isabelle Romieu  Amanda J. Cross  Paolo Vineis  Augustin Scalbert 《European journal of epidemiology》2018,33(11):1063-1075
Polyphenols may play a chemopreventive role in colorectal cancer (CRC); however, epidemiological evidence supporting a role for intake of individual polyphenol classes, other than flavonoids is insufficient. We evaluated the association between dietary intakes of total and individual classes and subclasses of polyphenols and CRC risk and its main subsites, colon and rectum, within the European Prospective Investigation into Cancer and Nutrition (EPIC) study. The cohort included 476,160 men and women from 10 European countries. During a mean follow-up of 14 years, there were 5991 incident CRC cases, of which 3897 were in the colon and 2094 were in the rectum. Polyphenol intake was estimated using validated centre/country specific dietary questionnaires and the Phenol-Explorer database. In multivariable-adjusted Cox regression models, a doubling in total dietary polyphenol intake was not associated with CRC risk in women (HRlog2?=?1.06, 95% CI 0.99–1.14) or in men (HRlog2?=?0.97, 95% CI 0.90–1.05), respectively. Phenolic acid intake, highly correlated with coffee consumption, was inversely associated with colon cancer in men (HRlog2?=?0.91, 95% CI 0.85–0.97) and positively associated with rectal cancer in women (HRlog2?=?1.10, 95% CI 1.02–1.19); although associations did not exceed the Bonferroni threshold for significance. Intake of other polyphenol classes was not related to colorectal, colon or rectal cancer risks. Our study suggests a possible inverse association between phenolic acid intake and colon cancer risk in men and positive with rectal cancer risk in women.  相似文献   
42.
Particle exposure has traditionally been monitored as mass concentration of PM10 (particles with an aerodynamic diameter less than 10 microm), more recently also as PM2.5. The mass concentration is strongly influenced by the large particles. Therefore, particle mass is a poor measure for characterizing the amount of the small, possibly more biologically potent particles. We used polystyrene particles (PSP) ranging in diameter from 0.0588 to 11.14 microm, carbon black (CB), and diesel exhaust particles (DEP), to study the adjuvant effect of particles on the immune response to the allergen ovalbumin (OVA) after sc injection into the footpad of BALB/cA mice. At a given mass dose, the small particles (0.0588 and 0.202 microm PSP, CB, and DEP) increased the allergen-specific IgE serum levels to a substantially higher degree than the larger particles (1.053, 4.64, and 11.14 microm PSP). Further, in the draining lymph node during the primary response, the fine particles (0.202 microm) with OVA increased cell numbers, expression of surface markers (CD19, MHC class II, CD86, and CD23) and ex vivo production of IL-4 and IL-10, whereas the largest (11.14 microm) particles did not. Linear regression analyses indicated that the IgE response was not predicted by particle mass (R2 = 0.06), but was predicted by the total particle surface area (R2 = 0.64), number of particles (R2 = 0.62), and particle diameter (R2 = 0.58). In conclusion, we found that fine particles exerted stronger adjuvant effects on allergic responses than larger particles at equal mass doses. Consequently, the dose described as total particle surface area or particle number predicts the adjuvant effect of particles better than the currently used particle mass.  相似文献   
43.
The survival of 1098 patients with ulcer perforation in Norway during the period 1952–1990 was compared with expected survival. Cox regression models incorporating population mortality rates, were used to analyse effects of sex, age, year of birth, and year at risk on excess mortality. Survival was lower in patients than in the general population through a follow-up period of 38 years. Relative survival was lower in women as compared to men, due to more delayed treatment. Long-term survival was lower after praepyloric perforations than after the other perforation types. Relative survival was higher in patients treated 1952–1970 than in those treated more recently. However, adjustment for year of birth revealed a decline in short-term mortality with calendar time, which is in accordance with improved management during the study period. Relative mortality, particularly long-term mortality, was higher in younger birth cohorts, suggesting a shift towards more serious etiologies.  相似文献   
44.
The effects of three model endocrine disruptors, prochloraz, ketoconazole and genistein on steroidogenesis were tested in the adrenocortical H295R cell line to demonstrate that a broader mechanistic understanding can be achieved in one assay by applying chemical analysis to the H295R assay. Seven key steroid hormones (pregnenolone, progesterone, dehydroepiandrosterone, androstenedione, testosterone, estrone and 17β-estradiol) were analyzed using a novel and thoroughly validated GC-MS/MS method. In addition to the simultaneous quantification of 7 steroid hormones, the present method also negates the potential problems of cross-reactivity that can be encountered in some immunoassays. Although all 3 test compounds decrease the concentrations of the main sex steroids, the chemicals exerted different effects upstream in the pathway. Exposure to prochloraz resulted in increased hormone levels upstream of steroid 17 alpha-hydroxylase/17,20 lyase (P450c17) and decreases downstream. Ketoconazole inhibited the entire pathway, while exposure to genistein resulted in increased hormone levels upstream of 3-β-hydroxysteroid dehydrogenase (3β-HSD) and decreases downstream. The results demonstrate that chemical analysis combined with the H295R cell assay is an useful tool for studying the mechanisms by which endocrine disruptors interfere with the steroidogenic pathway.  相似文献   
45.
Objective: To compare the multi-biomarker disease activity (MBDA) score with the DAS28-CRP and CRP for predicting risk of radiographic progression in patients with rheumatoid arthritis.

Methods: Published studies of the MBDA score and radiographic progression with ≥100 patients per cohort were evaluated. Rates of radiographic progression over 1?year were determined across the low/moderate/high categories for MBDA score (low/moderate/high: <30, 30–44, >44), DAS28-CRP (low/moderate/high: ≤2.67, >2.67–4.09, >4.09) and CRP (low/moderate/high: ≤10, >10–30, >30?mg/L), with positive and negative predictive value (PPV, NPV) and relative risk (RR) determined for high vs. not-high (i.e. low and moderate combined) categories. Patient-level data from studies having all three measures was pooled to: (1) determine a combined RR for radiographic progression in the high vs. not-high categories for each measure; and (2) compare the predictive ability of MBDA score vs. DAS28-CRP by comparing the rates of radiographic progression observed in subgroups created by cross-classifying the high and not-high categories of each measure.

Results: Five cohorts were identified for inclusion (total N=929). In each, radiographic progression was more frequent with increasing MBDA scores. Among the three cohorts with requisite data, PPVs were generally similar using categories of MBDA score, DAS28-CRP or CRP but NPVs were greater for MBDA score (93–97%) than DAS28-CRP or CRP (77–87%). RRs for radiographic progression were greater when based on categories of MBDA score than DAS28-CRP or CRP and the combined RR was greater for MBDA score (4.6, p?<?.0001) than DAS28-CRP (1.7, p?=?.02) or CRP (1.7, p?=?.002). For patients cross-classified by MBDA score and DAS28-CRP, high vs. not-high MBDA score significantly predicted radiographic progression independently of DAS28-CRP.

Conclusions: High and not-high MBDA scores were associated with increased and low risk, respectively, for radiographic progression over one year. MBDA score was a better predictor of radiographic progression than DAS28-CRP or CRP.  相似文献   
46.

Objectives  

We investigated inequalities in self-rated health between immigrants, their descendants, and ethnic Danes and explored mediation by socioeconomic position and interactions between country of origin and socioeconomic position.  相似文献   
47.
It is recognized that the pH of exposure solutions can influence the toxicity and bioaccumulation of ionizing compounds. The present study investigates whether it can be considered a general rule that an ionizable compound is more toxic and more bioaccumulative when in the neutral state. Three processes were identified to explain the behavior of ionizing compounds with changing pH: the change in lipophilicity when a neutral compound becomes ionized, electrical attraction, and the ion trap. The literature was screened for bioaccumulation and toxicity tests of ionizing organic compounds performed at multiple pH levels. Toxicity and bioconcentration factors (BCFs) were higher for acids at lower pH values, whereas the opposite was true for bases. The effect of pH was most pronounced when pH?-?pK(a) was in the range of -1 to 3 for acids, and -3 to 1 for bases. The factor by which toxicity and BCF changed with pH was correlated with the lipophilicity of the compound (log?K(OW) of the neutral compound). For both acids and bases, the correlation was positive, but it was significant only for acids. Because experimental data in the literature were limited, results were supplemented with model simulations using a dynamic flux model based on the Fick-Nernst-Planck diffusion equation known as the cell model. The cell model predicts that bases with delocalized charges may in some cases show declining bioaccumulation with increasing pH. Little information is available for amphoteric and zwitterionic compounds; however, based on simulations with the cell model, it is expected that the highest toxicity and bioaccumulation of these compounds will be found where the compounds are most neutral, at the isoelectric point.  相似文献   
48.
49.
Preclinical studies have been carried out during the past four decades to investigate the different mechanisms of action of valproate (VPA). The mechanisms of VPA which seem to be of clinical importance include increased GABAergic activity, reduction in excitatory neurotransmission, and modification of monoamines. These mechanisms are discussed in relation to the various clinical uses of the drug. VPA is widely used as an antiepileptic drug with a broad spectrum of activity. In patients, VPA possesses efficacy in the treatment of various epileptic seizures such as absence, myoclonic, and generalized tonic-clonic seizures. It is also effective in the treatment of partial seizures with or without secondary generalization and acutely in status epilepticus. The pharmacokinetic aspects of VPA and the frequent drug interactions between VPA and other drugs are discussed. The available methods for the determination of VPA in body fluids are briefly evaluated. At present, investigations and clinical trials are carried out and evaluated to explore the new indications for VPA in other conditions such as in psychiatric disorders, migraine and neuropathic pain. Furthermore, the toxicity of VPA, both regarding commonly occurring side effects and potential idiosyncratic reactions are described. Derivatives of VPA with improved efficacy and tolerability are in development.  相似文献   
50.
Manchiraju et al. (International Journal of Mental Health and Addiction, 1–15, 2016) published the Compulsive Online Shopping Scale (COSS) in the International Journal of Mental Health and Addiction (IJMHA). To develop their measure of compulsive online shopping, Manchiraju and colleagues adapted items from the seven-item Bergen Shopping Addiction Scale (BSAS) and its’ original 28-item item pool. Manchiraju et al. did not add or remove any of the original seven items, and did not substantially change the content of any of the 28 items on which the BSAS was based. They simply added the word “online” to each existing item. Given that the BSAS was specifically developed to take into account the different ways in which people now shop and to include both online and offline shopping, there does not seem to be a good rationale for developing an online version of the BSAS. It is argued that the COSS is not really an adaptation of the BSAS but an almost identical instrument based on the original 28-item pool.  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