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   3944篇
  免费   237篇
  国内免费   15篇
耳鼻咽喉   33篇
儿科学   130篇
妇产科学   75篇
基础医学   638篇
口腔科学   87篇
临床医学   309篇
内科学   1044篇
皮肤病学   32篇
神经病学   399篇
特种医学   100篇
外科学   603篇
综合类   15篇
预防医学   198篇
眼科学   44篇
药学   293篇
中国医学   13篇
肿瘤学   183篇
  2023年   18篇
  2022年   48篇
  2021年   81篇
  2020年   48篇
  2019年   87篇
  2018年   116篇
  2017年   66篇
  2016年   102篇
  2015年   87篇
  2014年   118篇
  2013年   138篇
  2012年   239篇
  2011年   242篇
  2010年   128篇
  2009年   118篇
  2008年   191篇
  2007年   203篇
  2006年   217篇
  2005年   191篇
  2004年   191篇
  2003年   192篇
  2002年   147篇
  2001年   118篇
  2000年   117篇
  1999年   107篇
  1998年   44篇
  1997年   38篇
  1996年   37篇
  1995年   22篇
  1994年   20篇
  1993年   15篇
  1992年   80篇
  1991年   69篇
  1990年   53篇
  1989年   62篇
  1988年   42篇
  1987年   44篇
  1986年   37篇
  1985年   38篇
  1984年   23篇
  1983年   22篇
  1982年   20篇
  1980年   19篇
  1979年   33篇
  1978年   12篇
  1977年   15篇
  1974年   11篇
  1973年   12篇
  1967年   10篇
  1966年   15篇
排序方式: 共有4196条查询结果,搜索用时 0 毫秒
51.
52.
Coronary artery endothelial and myocardial ultrastructure was studied in guinea-pig heart-lung preparations (HLP) subjected to ischemic cardiac arrest induced by three hypothermic solutions. Two of the solutions used had high potassium chloride concentration ("Alabama" and "St. Thomas") while the third, instead, was a bicarbonate buffer (Kreb's solution). Five experimental groups were studied. In group 1 (control) the HLP were not subjected to cardiac arrest. Groups 2, 3, and 4 were subjected to a period of cardiac arrest of 30, 60, and 120 minutes respectively. In group 5, HLP were reperfused with blood for 30 minutes after 60 minutes of cardiac arrest. A thin ring of the left anterior descending coronary artery and myocardial fragments were obtained at the end of each experiment and were analyzed by means of transmission electron microscopy (TEM). Functional parameters were recorded in group 5. HLP perfused with Alabama solution showed a well-preserved endothelium and myocardium. HLP perfused with Krebs solution showed slight changes of the endothelial glycocalix only in group 4. Further, HLP perfused with Krebs solution showed extensive myocardial lesions (groups 3 and 4). These ischemic changes were not completely reversed after reperfusion (group 5). HLP perfused with St. Thomas solution showed only endothelial changes. These lesions were mainly characterized by: disappearance of the glycocalix and pynocytotic vesicles, endothelial cell bulging (group 2), and loss of the endothelial continuity (groups 3, 4, and 5). Hemodynamic parameters were significantly changed only in the Krebs-perfused HLP which showed a deterioration of the cardiac function related to the ischemic damage.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
53.
Free oxygen radicals are produced after coronary artery occlusion and reperfusion. Polyunsaturated fatty acids are oxidized by free radicals to lipid peroxides. Measurements of plasma malondialdehyde (MDA) formed by the breakdown of lipid peroxides are often used as markers of lipid peroxidation. The effect of intravenous nitroglycerin on plasma MDA levels was studied in 43 patients who received thrombolytic therapy for acute myocardial infarction. Plasma MDA levels in patients were elevated on admission to the hospital compared with healthy controls, and normalized within 48 hours. A greater increase in plasma MDA concentrations after thrombolysis was found in patients with noninvasive signs of reperfusion than in patients judged to have a persistent occlusion. In the 23 patients receiving immediate intravenous nitroglycerin infusion, plasma MDA levels did not change from baseline to 90 minutes (0.92 ± 0.22 and 0.92 ± 0.23 μmol/L, p = 0.99), whereas a significant increase was found in the 20 control patients who did not receive nitroglycerin (from 0.83 ± 0.22 to 1.01 ± 0.30 μmol/L, p = 0.0004) (p = 0.036 for the difference between groups). Successful reperfusion after thrombolytic therapy entails increased lipid peroxidation. Intravenous nitroglycerin reduces lipid peroxidation during myocardial ischemia and reperfusion.  相似文献   
54.
55.
56.
ContextPsychological distress is associated with adverse health outcomes in serious illness and magnified among patients of low socioeconomic status. Aspects of one's culture, such as religion and spirituality, can influence these patients' coping response to distress. Advanced chronic kidney disease (CKD) is a serious illness that disproportionately affects patients of low socioeconomic status, but a theory-based understanding of this group's lived experience of CKD is lacking.ObjectivesWe explored the cognitions, emotions, and coping behaviors of patients with CKD with emphasis on those of low socioeconomic status. We further inquired into any influences of religion or spirituality.MethodsWe interviewed 50 English-speaking or Spanish-speaking adults with advanced CKD from three medical centers in Nashville, Tennessee. Analyses occurred with isolation of themes; development of a coding system; and creation of a conceptual framework using an inductive-deductive approach.ResultsMedian age was 65 years; median annual income was $17,500 per year; and 48% of participants had not progressed beyond high school. Key beliefs (awareness of mortality and lack of control) influenced patients' emotions (existential distress in the form of death anxiety, prognostic uncertainty, and hopelessness) and coping behaviors (acceptance, avoidance, emotion regulation via spirituality, and seeking social support via a religious community).ConclusionIndividuals with advanced CKD and low socioeconomic status lack control over disease progression, experience death anxiety and existential distress, and emphasize spirituality to cope. Our study identifies novel components for a psychotherapeutic intervention for patients with advanced CKD at high risk for adverse health outcomes.  相似文献   
57.
In this work, we propose that for further studies of the physiopathology and treatment for inflammatory bowel diseases, an integral view of the conditions, including the triad of microbiota–heat shock proteins (HSPs)–probiotics, ought to be considered. Microbiota is the complex microbial flora that resides in the gut, affecting not only gut functions but also the health status of the whole body. Alteration in the microbiota’s composition has been implicated in a variety of pathological conditions (e.g., ulcerative colitis, UC), involving both gut and extra-intestinal tissues and organs. Some of these pathologies are also associated with an altered expression of HSPs (chaperones) and this is the reason why they may be considered chaperonopathies. Probiotics, which are live microorganisms able to restore the correct, healthy equilibrium of microbiota composition, can ameliorate symptoms in patients suffering from UC and modulate expression levels of HSPs. However, currently probiotic therapy follows ex-adiuvantibus criteria, i.e., treatments with beneficial effects but whose mechanism of action is unknown, which should be changed so the probiotics needed in each case are predetermined on the basis of the patient’s microbiota. Consequently, efforts are necessary to develop diagnostic tools for elucidating levels and distribution of HSPs and the microbiota composition (microbiota fingerprint) of each subject and, thus, guide specific probiotic therapy, tailored to meet the needs of the patient. Microbiota fingerprinting ought to include molecular biology techniques for sequencing highly conserved DNA, e.g., genes encoding 16S RNA, for species identification and, in addition, quantification of each relevant microbe.  相似文献   
58.
ObjectiveTo examine the effect of older versus younger age on change in anthropometric and metabolic measures during extended treatment of psychotic depression with sertraline plus olanzapine.MethodsTwo hundred and sixty-nine men and women aged 18–85 years with an episode of psychotic depression were treated with open-label sertraline plus olanzapine for up to 12 weeks. Participants who remained in remission following an 8-week stabilization phase were eligible to participate in a 36-week randomized controlled trial (RCT) that compared the efficacy and tolerability of sertraline plus olanzapine with sertraline plus placebo. Weight, waist circumference and plasma lipids, glucose, HbA1c, and insulin were measured at regular intervals during the acute, stabilization and randomized phases of the study. Linear mixed models were used to analyze the trajectories of anthropometric and metabolic measures.ResultsParticipants aged 60 years or older experienced less weight gain and less increase in cholesterol during the combined acute and stabilization phases of the study compared with those aged 18–59 years. At the acute-stabilization termination visit, mean weight in older participants was 6.5 lb. less than premorbid weight, whereas it was 17.9 lb. more than premorbid weight in younger participants. In the RCT, there was a significant interaction of treatment and age group for the trajectory of weight, but the post hoc tests that compared age groups within each treatment arm were not statistically significant. There were no clinically significant differences between younger and older participants in glycemic measures.ConclusionOlder patients with psychotic depression experienced less increase in weight and total cholesterol than their younger counterparts during acute and stabilization treatment with sertraline plus olanzapine. In the older group, weight gained during the acute and stabilization phases appeared to be partial restoration of weight lost during the index episode of depression, whereas weight gain in younger participants was not.  相似文献   
59.

Aim

To find an association between Y chromosome polymorphisms and some ethnic groups.

Methods

Short tandem repeats (STR) and single-nucleotide polymorphisms (SNP) on the Y chromosome were typed in 311 unrelated men from four different ethnic groups – Italians from northern Italy, Albanians, Africans from the Maghreb region, and Indo-Pakistanis, using the AmpFlSTR® Yfiler PCR Amplification Kit and the SNaPshot Multiplex Kit.

Results

STRs analysis found 299 different haplotypes and SNPs analysis 11 different haplogroups. Haplotypes and haplogroups were analyzed and compared between different ethnic groups. Significant differences were found among all the population groups, except between Italians and Indo-Pakistanis and between Albanians and Indo-Pakistanis.

Conclusions

Typing both STRs and SNPs on the Y chromosome could become useful in determining ethnic origin of a potential suspect.Determining the ethnic origin of a suspect through DNA analysis of biological stains left at the crime scene is an important part of criminal investigations. To discriminate between different ethnic groups, short tandem repeat (STR) autosomal marker analysis (1-6) can be complemented by single-nucleotide polymorphism (SNP) assays, which have have been demonstrated to be more useful for this purpose (7,8). The introduction of new markers, mostly from the Y chromosome, offers a better power of discrimination to define even sub-populations of different ethnic groups (9-11). This study aims to compare a sample of Italian men from Brescia (northern Italy) with a sample of men from each of three main ethnic groups living in Brescia county (Albanians, North Africans, Indo-Pakistanis), through STRs and SNPs Y chromosome typing, in order to find the data useful in defining the ethnic origin.  相似文献   
60.
Anxiety and depression in Parkinson’s disease (PD) reduce well-being of the patients. Emotional alterations influence motor skills and cognitive performance; moreover, they contribute significantly and independently to worsen rehabilitative treatment response. We investigated anxiety, depression, and quality of life in PD patients subjected to multidisciplinary rehabilitative training. The self-controlled study included 100 PD patients (49 males and 51 females with the mean age of 64.66 years) admitted to 60 days hospitalization rehabilitative program, between January 2017 and December 2018. Motor, cognitive, linguistic abilities, and functional independence were evaluated at admission (T0 baseline visit) and 60 days after (T1) the multidisciplinary rehabilitation including motor exercises, speech therapies, and cognitive intervention. The multidisciplinary rehabilitation improved functional status in PD patients and exerted its positive effects on mood, motor abilities, autonomy in the activities of daily life, perception of quality of life, cognitive performance and speech skills. Non-motor symptoms may worsen severe disability and reduce quality of life. They are often poorly recognized and inadequately treated. Nonetheless, multidisciplinary rehabilitative training represents an optimal strategy to improve disease management. The study was approved by Istituito di Ricovero e Cura a Carattere Scientifico (IRCCS) Centro Neurolesi “Bonino-Pulejo” Ethical Committee (approval No. 6/2016) in June 2016.  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