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   1853篇
  免费   81篇
  国内免费   7篇
耳鼻咽喉   24篇
儿科学   34篇
妇产科学   37篇
基础医学   237篇
口腔科学   148篇
临床医学   108篇
内科学   370篇
皮肤病学   30篇
神经病学   292篇
特种医学   51篇
外科学   219篇
综合类   6篇
一般理论   1篇
预防医学   86篇
眼科学   94篇
药学   98篇
中国医学   19篇
肿瘤学   87篇
  2023年   14篇
  2022年   12篇
  2021年   49篇
  2020年   21篇
  2019年   42篇
  2018年   41篇
  2017年   23篇
  2016年   38篇
  2015年   59篇
  2014年   62篇
  2013年   95篇
  2012年   163篇
  2011年   160篇
  2010年   80篇
  2009年   80篇
  2008年   151篇
  2007年   113篇
  2006年   118篇
  2005年   105篇
  2004年   89篇
  2003年   92篇
  2002年   74篇
  2001年   36篇
  2000年   20篇
  1999年   30篇
  1998年   16篇
  1997年   13篇
  1996年   11篇
  1995年   3篇
  1994年   5篇
  1993年   8篇
  1992年   8篇
  1991年   9篇
  1990年   7篇
  1989年   8篇
  1988年   13篇
  1987年   8篇
  1986年   3篇
  1985年   5篇
  1984年   3篇
  1983年   6篇
  1980年   5篇
  1979年   10篇
  1978年   3篇
  1977年   3篇
  1976年   5篇
  1973年   5篇
  1972年   2篇
  1971年   3篇
  1970年   4篇
排序方式: 共有1941条查询结果,搜索用时 203 毫秒
141.
The aim of our study was to evaluate the benefits of supplementation with 800 mg/day of alpha-tocopherol with regard to cellular viability in HIV-1 seropositive patients undergoing anti-retroviral therapy. A total of 29 patients participated in the study, of whom 14 were given the supplement and 15 a placebo. The analyses were carried out before treatment commenced and after 60, 120 and 180 days. The plasma levels of HIV-1 RNA showed a significant decrease as a consequence of treatment time in the groups studied (p = 0.0001), although the difference between the treatments over time was not verified (p = 0.7343). The percentage of viable lymphocytes showed a significant increase as a consequence of treatment time in both groups studied (p = 0.0002) and a significant difference between the treatments over time (p = 0.0472). The percentage of lymphocytes in apoptosis showed a significant reduction over time (p = 0.0003), as well as a significant difference between the treatments over time (p = 0.0321). The significant increase in cellular viability indicates that supplementation with alpha-tocopherol offers an additional positive effect on cellular preservation in HIV-1 individuals undergoing anti-retroviral therapy; however, it represents an additional risk of anti-retroviral therapeutic failure, possibly due to drug-drug interaction involving up-regulation of metabolic clearance.  相似文献   
142.
143.
Obesity represents a continuously growing global epidemic and is associated with the development of type 2 diabetes mellitus. The etiology of type 2 diabetes is related to the resistance of insulin-sensitive tissues to its action leading to impaired blood glucose regulation. Photobiomodulation (PBM) therapy might be a non-pharmacological, non-invasive strategy to improve insulin resistance. It has been reported that PBM therapy in combination with physical exercise reduces insulin resistance. Therefore, the aim of this study was to investigate the effects of PBM therapy on insulin resistance in obese mice. Male Swiss albino mice received low-fat control diet (n?=?16, LFC) or high-fat diet (n?=?18, HFD) for 12 weeks. From 9th to 12th week, the mice received PBM therapy (LASER) or Sham (light off) treatment and were allocated into four groups: LFC Sham (n?=?8), LFC PBM (n?=?8), HFD Sham (n?=?9), and HFD PBM (n?=?9). The PBM therapy was applied in five locations: to the left and right quadriceps muscle, upper limbs and center of the abdomen, during 40 s at each point, once a day, 5 days a week, for 4 weeks (780 nm, 250 mW/cm2, 10 J/cm2, 0.4 J per site; 2 J total dose per day). Insulin signaling pathway was evaluated in the epididymal adipose tissue. PBM therapy improved glucose tolerance and phosphorylation of Akt (Ser473) and reversed the HFD-induced reduction of GLUT4 content and phosphorylation of AS160 (Ser588). Also, PBM therapy reversed the increased area of epididymal and mesenteric adipocytes. The results showed that chronic PBM therapy improved parameters related to obesity and insulin resistance in HFD-induced obesity in mice.  相似文献   
144.
145.
Leishmaniasis is endemic in 98 countries and territories worldwide. The therapies available for leishmaniasis have serious side effects, thus prompting the search for new therapies. The present study investigated the antileishmanial activities of 2,3-diarylsubstituted quinoxaline derivatives against Leishmania amazonensis. The antiproliferative activities of 6,7-dichloro-2,3-diphenylquinoxaline (LSPN329) and 2,3-di-(4-methoxyphenyl)-quinoxaline (LSPN331) against promastigotes and intracellular amastigotes were assessed, and the cytotoxicities of LSPN329 and LSPN331 were determined. Morphological and ultrastructural alterations were examined by electron microscopy, and biochemical alterations, reflected by the mitochondrial membrane potential (ΔΨm), mitochondrial superoxide anion (O2·) concentration, the intracellular ATP concentration, cell volume, the level of phosphatidylserine exposure on the cell membrane, cell membrane integrity, and lipid inclusions, were evaluated. In vivo antileishmanial activity was evaluated in a murine cutaneous leishmaniasis model. Compounds LSPN329 and LSPN331 showed significant selectivity for promastigotes and intracellular amastigotes and low cytotoxicity. In promastigotes, ultrastructural alterations were observed, including an increase in lipid inclusions, concentric membranes, and intense mitochondrial swelling, which were associated with hyperpolarization of ΔΨm, an increase in the O2· concentration, decreased intracellular ATP levels, and a decrease in cell volume. Phosphatidylserine exposure and DNA fragmentation were not observed. The cellular membrane remained intact after treatment. Thus, the multifactorial response that was responsible for the cellular collapse of promastigotes was based on intense mitochondrial alterations. BALB/c mice treated with LSPN329 or LSPN331 showed a significant decrease in lesion thickness in the infected footpad. Therefore, the antileishmanial activity and mitochondrial mechanism of action of LSPN329 and LSPN331 and the decrease in lesion thickness in vivo brought about by LSPN329 and LSPN331 make them potential candidates for new drug development for the treatment of leishmaniasis.  相似文献   
146.
147.
148.
Much literature has been written in the field of child psychiatry regarding the placebo as a tool to test drug efficacy in clinical trials, but quite little regarding the placebo effect itself or its clinical use in child psychiatry. In this article, we aim to critically review the literature regarding the placebo effect in children and adolescents with mental disorders, focusing especially on factors influencing the placebo effect and how they may influence the interpretation of clinical trials. The placebo effect seems to be more marked in children than adults, and particularly in children and adolescents with depression, although it is pervasive across ages and is present in non-psychiatric conditions as well. The use of a placebo in clinical trials as a comparator with drugs that have moderate efficacy at most makes it difficult to obtain positive results, and much effort is needed to design very high quality clinical trials that may overcome the limitations of using a placebo. In addition, the placebo effect across ages and clinical conditions must be tested directly (compared with no treatment whenever possible), in order to characterise which placebos work for what and to determine their use in clinical settings.  相似文献   
149.
Six lycorine derivatives were prepared, characterized, and evaluated for their in vitro anti‐Trichomonas vaginalis activity. Compounds bearing an acetyl ( 2 ), lauroyl ( 3 ), benzoyl ( 4 and 5 ), and p‐nitrobenzoyl ( 6 and 7 ) groups were synthesized. The best activity was achieved with lycorine esterified at C‐2 position with lauroyl group. Preliminary structure–activity relationship points that unprotected OH group at C‐1 and C‐2 is not necessary to the antiparasitic activity, and none of the derivative was less active than lycorine. The lycorine structural requisites required to kill this amitochondriate cell seem to be different in comparison with the derivatives most active against other parasites and tumor cell lines, both mitochondriated cells. This result is an important contribution with our ongoing studies regarding the mechanism of action of the Amaryllidaceae alkaloids on T. vaginalis cell death opening a new perspective to optimize this innovative pharmacological potential.  相似文献   
150.
Little is known about the changes that take place in the adolescent brain over the first few years following the onset of psychosis. The present longitudinal study builds on an earlier cross-sectional report demonstrating brain abnormalities in adolescent-onset psychosis patients with a recent-onset first episode of psychosis. Magnetic resonance imaging studies were obtained at baseline and 2 years later from 21 adolescents with psychosis and 34 healthy controls matched for age, gender, and years of education. Whole-brain volumes and gray matter (GM) and cerebrospinal fluid (CSF) volumes of the frontal, parietal, temporal, and occipital lobes were measured at baseline and at 2-year follow-up. In the frontal lobe, the rate of GM volume loss was significantly higher in male patients (2.9% and 2.0%, respectively, for left and right) than in controls (1.2% and 0.7%, respectively, for left and right). In the left frontal lobe, male patients showed a significantly higher rate of CSF volume increase than controls (8.6% vs 6.4%). These differences in rates of volume change were observed in male and female patients, although only males showed significant time x diagnosis interactions. This negative finding in females should be interpreted with caution as the study was underpowered to detect change in women due to limited sample size. An exploratory analysis revealed that schizophrenia and nonschizophrenia psychotic disorders showed similar volume change patterns relative to controls. Change in clinical status was not correlated with longitudinal brain changes. Our results support progression of frontal lobe changes in males with adolescent-onset psychosis.  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