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   3472篇
  免费   228篇
  国内免费   4篇
耳鼻咽喉   89篇
儿科学   76篇
妇产科学   36篇
基础医学   462篇
口腔科学   36篇
临床医学   335篇
内科学   513篇
皮肤病学   76篇
神经病学   596篇
特种医学   99篇
外科学   637篇
综合类   27篇
一般理论   2篇
预防医学   164篇
眼科学   164篇
药学   173篇
肿瘤学   219篇
  2023年   17篇
  2022年   19篇
  2021年   61篇
  2020年   27篇
  2019年   48篇
  2018年   67篇
  2017年   50篇
  2016年   67篇
  2015年   78篇
  2014年   103篇
  2013年   96篇
  2012年   201篇
  2011年   195篇
  2010年   102篇
  2009年   82篇
  2008年   194篇
  2007年   166篇
  2006年   159篇
  2005年   176篇
  2004年   171篇
  2003年   148篇
  2002年   144篇
  2001年   118篇
  2000年   120篇
  1999年   106篇
  1998年   45篇
  1997年   45篇
  1996年   32篇
  1995年   22篇
  1994年   29篇
  1993年   20篇
  1992年   45篇
  1991年   54篇
  1990年   37篇
  1989年   49篇
  1988年   56篇
  1987年   40篇
  1986年   47篇
  1985年   45篇
  1984年   18篇
  1983年   22篇
  1982年   18篇
  1979年   18篇
  1977年   20篇
  1970年   15篇
  1968年   14篇
  1967年   15篇
  1966年   13篇
  1914年   16篇
  1913年   25篇
排序方式: 共有3704条查询结果,搜索用时 15 毫秒
91.
中文:背景患者入院后可从不当消毒的环境表面获得多药耐药菌和艰难梭菌。本文确定了3种强化的终末消毒(入住同一病房的两名患者之间的消毒)策略,对感染耐甲氧西林金黄色葡萄球菌(MRSA)、耐万古霉素肠球菌(VRE)、艰难梭菌(CD)和多重耐药不动杆菌的影响。方法本文在美国东南部的9家医院开展了一项务实的、集群-随机、交叉研究。凡曾有感染或定植目标细菌感染患者居住过的病房,患者出院后随机采取4种消毒策略中的一种方法进行终末消毒:对照(季胺盐类消毒剂消毒,但凡遇到CD采用含氯消毒剂);UV(季胺盐类+UV-C消毒,但凡遇到CD采用含氯消毒剂+UV-C);含氯消毒剂;含氯消毒剂+UV-C。凡入住目标病房的患者被列为暴露人群。这4种终末消毒方法分别在每家医院连续实施7个月的周期。本文随机设计这几种消毒策略在每家医院内的实施顺序(1:1:1:1)。主要产出的结果是,观察暴露患者中目标细菌的感染的发生或定植情况,以及ITT人群中暴露患者CD感染发生率。本研究ClinicalTrials.gov注册编号:NCT01579370。结果共有31 226名患者暴露,其中21 395(69%)符合标准,包括4 916名对照组,5 178名UV组,5 438名含氯消毒剂组,以及5 863名含氯消毒剂+UV组。在对照组中,22 426个暴露日中有115名患者发生目标细菌的感染(51.3/10000暴露日)。在标准清洁策略的基础上增加UV消毒的暴露患者,其目标细菌感染的发生率明显较低(n=76;33.9/10 000暴露日;RR:0.70,95%CI:0.50~0.988;P=0.036)。含氯消毒剂组(n=101;41.6/10 000暴露日;RR:0.85,95%CI:0.69~1.04;P=0.116),或含氯消毒剂+UV组患者(n=131;45.6/10 000暴露日;RR:0.91,95%CI:0.76~1.09;P=0.303)的目标细菌的感染率,其差异无统计学意义。同样,在含氯消毒剂的基础上增加UV消毒,暴露患者中CD感染率也没有发生改变((n=38 vs 36;30.4 vs 31.6/10 000暴露日;RR:1.0,95%CI:0.57-1.75;P=0.997)。解释污染的医疗机构环境是获得病原微生物的重要来源;强化终末消毒可以降低这一风险。  相似文献   
92.

Objective

Consumption of energy- and nutrient-dense snacks are recommended for older people to maintain adequate nutrition. We evaluated the effects of dairy-based and energy-enriched berry products consumed as snacks on nutritional and functional status among vulnerable older people receiving home care services.

Design

Randomised controlled study.

Setting and participants

The study sample consisted of 85 home care clients, with mean age of 81.9 (SD 7.1) years in the intervention group (n=50) and 83.7 (SD 8.1) years in the control group (n=35), and 72% women in both groups.

Intervention

In the intervention group, the participants consumed both high-protein dairy-based products and energy-enriched berry purées for three months. The snack products provided nearly 300 kcal and 14 g protein per day.

Measurements

The Mini Nutritional Assessment (MNA), body mass index (BMI), mid-arm muscular area (MAMA) and concentrations of plasma albumin and prealbumin and blood haemoglobin were used to determine nutritional status, and handgrip strength was used to determine functional status at baseline and after the intervention. Results: After adjustment for age and gender, the intervention showed a significant effect on MNA scores (2.1, 95% [CI]: 1.0 to 3.3) (p=0.003), albumin concentration (2.0 g/L, 95% [CI]: 1.1 to 3.2) (p=0.006) and handgrip strength of the right hand in women (2.4 kg, 95% [CI]: 1.2 to 3.3) (p=0.007). The MNA scores improved in the intervention group, while albumin concentration and handgrip strength decreased in the control group.

Conclusions

Regular use of dairy- and energy-enriched berry-based snacks may improve or maintain nutritional and functional status among older people in home care.
  相似文献   
93.
BACKGROUND: Ligaments may be subjected to higher than normal loads when one of the complementary ligament restraints of a joint or the ligament itself is injured. Damage can accumulate in a ligament due to cyclic and static loading under these increased loads, but it remains unknown whether one type of loading will cause rupture faster than the other in medial collateral ligament. METHODS: The objective of this study was to compare the time and strain behaviour of normal rabbit medial collateral ligaments under static and cyclic loading over a wide range of applied stresses, with particular emphasis on time-to-rupture. Stresses were normalized to ultimate tensile strength and selected from three regions of the stress-strain curve: two linear-region stresses (60% and 30% of the ultimate tensile strength) and one stress at the transition from the toe-region to the linear-region (15% of the ultimate tensile strength). FINDINGS: Cyclic loading caused faster rupture than static loading at all stresses. Strain-time profiles were different in that the increase in strain (strain relative to initial strain) was greater under static than cyclic loading prior to rupture. However, steady-state strain rate (when increase in strain reaches a plateau in the secondary strain stage) was greater under cyclic than static loading. INTERPRETATIONS: These results suggest that cyclic loading is more detrimental than static loading in ligaments that are subjected to higher than normal stresses following injury of a complementary restraint or the ligament itself.  相似文献   
94.
95.
Background contextLumbar interbody fusion (LIF) techniques have been used for years to treat a number of pathologies of the lower back. These procedures may use an anterior, posterior, or combined surgical approach. Each approach is associated with a unique set of complications, but the exact prevalence of complications associated with each approach remains unclear.PurposeTo investigate the rates of perioperative complications of anterior lumbar interbody fusion (ALIF), posterior/transforaminal lumbar interbody fusion (P/TLIF), and LIF with a combined anterior-posterior interbody fusion (APF).Study design/settingRetrospective review of national data from a large administrative database.Patient samplePatients undergoing ALIF, P/TLIF, or APF.Outcome measuresPerioperative complications, length of stay (LOS), total costs, and mortality.MethodsThe Nationwide Inpatient Sample database was queried for patients undergoing ALIF, P/TLIF, or APF between 2001 and 2010 as identified via International Classification of Diseases, ninth revision codes. Univariate analyses were carried out comparing the three cohorts in terms of the outcomes of interest. Multivariate analysis for primary outcomes was carried out adjusting for overall comorbidity burden, race, gender, age, and length of fusion. National estimates of annual total number of procedures were calculated based on the provided discharge weights. Geographic distribution of the three cohorts was also investigated.ResultsAn estimated total of 923,038 LIFs were performed between 2001 and 2010 in the United States. Posterior/transforaminal lumbar interbody fusions accounted for 79% to 86% of total LIFs between 2001 and 2010, ALIFs for 10% to 15%, and APF decreased from 10% in 2002 to less than 1% in 2010. On average, P/TLIF patients were oldest (54.55 years), followed by combined approach (47.23 years) and ALIF (46.94 years) patients (p<.0001). Anterior lumbar interbody fusion, P/TLIF, and combined surgical costs were $75,872, $65,894, and $92,249, respectively (p<.0001). Patients in the P/TLIF cohort had the greatest number of comorbidities, having the highest prevalence for 10 of 17 comorbidities investigated. Anterior-posterior interbody fusion group was associated with the greatest number of complications, having the highest incidence of 12 of the 16 complications investigated.ConclusionsThese data help to define the perioperative risks for several LIF approaches. Comparison of outcomes showed that a combined approach is more expensive and associated with greater LOS, whereas ALIF is associated with the highest postoperative mortality. These trends should be taken into consideration during surgical planning to improve clinical outcomes.  相似文献   
96.
The question of whether genetic polymorphisms of CYP2D6 can affect treatment outcome in patients with early post-menopausal oestrogen receptor (ER)-positive breast cancer has been a matter of debate over the past few years. In this article we revisit the hypothesis of CYP2D6 being a potential tamoxifen outcome predictor and provide detailed insight into the ongoing controversy that prevented the CYP2D6 marker from being accepted by the scientific and clinical community. We summarize the available pharmacokinetic, pharmacodynamic and pharmacogenetic evidence and resolve the controversy based on the recognized methodological and statistical issues. The cumulative evidence suggests that genotyping for CYP2D6 is clinically relevant in post-menopausal women. This is important, because the clarification of this issue has the potential to resolve a clinical management question that is relevant to hundreds of thousands of women diagnosed with ER-positive breast cancer each year, who should not be denied effective endocrine therapy.  相似文献   
97.
OBJECTIVE: Mast cells are thought to participate in the pathogenesis of inflammatory bowel disease (IBD). In this study, urinary excretion of N-methylhistamine (UMH), a stable metabolite of the mast cell mediator histamine, was evaluated as an indicator of disease activity in patients with IBD. METHODS: Urinary excretion of UMH (microg/mmol creatinine x m2 body surface area) was measured by radioimmunoassay in 55 controls, 56 patients with Crohn's disease, and in 36 patients with ulcerative colitis. Excretion rates were correlated with clinical, serological, and endoscopic disease activity, disease extent, and location. RESULTS: Urinary excretion of UMH was found to be significantly elevated in IBD. Patients with active Crohn's disease (7.1 +/- 4.2, p = 0.002 vs controls) and active ulcerative colitis (8.1 +/- 4.8, p = 0.02 vs controls) had higher rates of UMH excretion than patients in remission (6.3 +/- 3.8 and 5.2 +/- 2.3, respectively) or controls (4.6 +/- 1.9). In Crohn's disease and ulcerative colitis, a significant correlation of UMH excretion with clinical disease activity was obtained (Crohn's Disease Activity Index r2 = 0.58, Clinical Activity Index r2 = 0.57, p < 0.0001). Serologically, orosomucoid showed the best positive correlation with disease activity (Crohn's Disease Activity Index r2 0.80, Clinical Activity Index r2 = 0.86, p < 0.0001), but UMH excretion was found to reflect disease activity more accurately than C-reactive protein (Crohn's Disease Activity Index r2 = 0.46, Clinical Activity Index r2 = 0.42, p < 0.0001). No association between UMH excretion and disease type or localization could be found in Crohn's disease. However, UMH excretion correlated strongly with endoscopic severity of inflammation in Crohn's disease (Crohn's Disease Endoscopic Index of Severity r2 = 0.70, p < 0.0001) or disease extent in ulcerative colitis. CONCLUSIONS: Urinary excretion of the histamine metabolite UMH is enhanced in IBD. It appears to represent an integrative parameter to monitor clinical and endoscopic disease activity in IBD, which appears to be influenced most likely by mediators released from histamine-containing cells, such as intestinal mast cell subtypes.  相似文献   
98.
Summary 5-Bromodeoxyuridine (BrdUrd) injected into the muscular tissue of fish bearing melanoma or neuroblastoma induces the production of virus-like particles in these tumors. The particles in the melanoma are morphologically similar to papovaviruses of polyoma-type, those in the neuroblastoma resemble oncornavirouses of B- and C-type.Supported by the Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 103 Zellenergetik und Zelldifferenzierung, Marburg, and by Justus-Liebig-Universität GießenThis paper contains parts of the doctoral dissertation of G. Kollinger  相似文献   
99.
Phytochromes are red- and far-red-sensing photoreceptors that detect the quantity, quality, and duration of light throughout the entire life cycle of plants. Phytochromes accumulate in the cytoplasm in the dark. As one of the earliest responses after light illumination, phytochromes localize to the nucleus where they become associated with discrete nuclear bodies (NBs). Here, we describe the steady-state dynamics of Arabidopsis phytochrome B (phyB) localization in response to different light conditions and define four phyB subnuclear localization patterns: diffuse nuclear localization, small and numerous NBs only, both small and large NBs, and large NBs only. We show that phyB nuclear import is not sufficient for phyB NB formation. Rather, phyB accumulation in NBs is mainly determined by the percentage of the total amount of phyB protein that is in the active phyB conformer, with large NBs always correlating with strong phyB responses. A genetic screen to identify determinants required for subnuclear localization of phyB resulted in several phyB mutants, mutants deficient in phytochrome chromophore biosynthesis, and mutations in at least one previously uninvestigated locus. This study lays the groundwork for future investigations to identify the molecular mechanisms of light-regulated partitioning of plant photoreceptors to discrete subnuclear domains.  相似文献   
100.
The identification of valid biomarkers for outcome prediction of diseases and improvement of drug response, as well as avoidance of side effects is an emerging field of interest in medicine. The concept of individualized therapy is becoming increasingly important in the treatment of patients with epilepsy, as predictive markers for disease prognosis and treatment outcome are still limited. Currently, the clinical decision process for selection of an antiepileptic drug (AED) is predominately based on the patient’s epileptic syndrome and side effect profiles of the AEDs, but not on effectiveness data. Although standard dosages of AEDs are used, supplemented, in part, by therapeutic monitoring, the response of an individual patient to a specific AED is generally unpredictable, and the standard care of patients in antiepileptic treatment is more or less based on trial and error. Therefore, there is an urgent need for valid predictive biomarkers to guide patient-tailored individualized treatment strategies in epilepsy, a research area that is still in its infancy. This review focuses on genomic factors as part of an individual concept for AED therapy summarizing examples that influence the prognosis of the disease and the response to AEDs, including side effects.  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