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   2915篇
  免费   160篇
  国内免费   6篇
耳鼻咽喉   35篇
儿科学   46篇
妇产科学   105篇
基础医学   377篇
口腔科学   346篇
临床医学   206篇
内科学   585篇
皮肤病学   70篇
神经病学   238篇
特种医学   59篇
外科学   279篇
综合类   12篇
一般理论   3篇
预防医学   269篇
眼科学   39篇
药学   259篇
中国医学   17篇
肿瘤学   136篇
  2023年   28篇
  2022年   55篇
  2021年   101篇
  2020年   65篇
  2019年   94篇
  2018年   111篇
  2017年   87篇
  2016年   77篇
  2015年   102篇
  2014年   123篇
  2013年   165篇
  2012年   204篇
  2011年   246篇
  2010年   145篇
  2009年   104篇
  2008年   175篇
  2007年   176篇
  2006年   143篇
  2005年   134篇
  2004年   118篇
  2003年   99篇
  2002年   72篇
  2001年   60篇
  2000年   45篇
  1999年   54篇
  1998年   24篇
  1997年   16篇
  1996年   6篇
  1995年   8篇
  1994年   8篇
  1993年   6篇
  1992年   18篇
  1991年   21篇
  1990年   26篇
  1989年   20篇
  1988年   15篇
  1987年   8篇
  1986年   18篇
  1985年   7篇
  1984年   16篇
  1983年   13篇
  1981年   7篇
  1979年   5篇
  1978年   5篇
  1976年   5篇
  1974年   6篇
  1973年   8篇
  1970年   4篇
  1969年   4篇
  1967年   4篇
排序方式: 共有3081条查询结果,搜索用时 0 毫秒
81.
Early experiments have resulted in the establishment of an efficient methodology for the production of a yellow fever vaccine in chicken embryo fibroblasts (CEF) using the 17DD virus strain [Freire, M.S., Mann, G.F., Marchevsky, R.S., Yamamura, A.M., Almeida, L.F., Jabor, A.V., Malachias, J.M., Coutinho, E.S., Galler, R., 2005. Production of yellow fever 17DD vaccine virus in primary culture of chicken embryo fibroblasts: yields, thermo and genetic stability, attenuation and immunogenicity. Vaccine 23, 2501-2512]. To investigate the role of the interferon system in vaccine virus yields, CEF cultures seeded at high and low cell densities and infected with the yellow fever 17DD virus were used. The supernatants of these cultures were tested for the presence of interferon by an assay based on the reduction of cytopathic effect of a challenge virus (Sindbis), for the enzymatic activity of the interferon-induced 2',5'-oligoadenylate synthetase and for the expression of 2',5'-oligoadenylate synthetase mRNA. The presence of interferon and its influence in the replication of yellow fever 17DD virus in CEF cultures was clearly demonstrated.  相似文献   
82.
Fungal keratitis is recognized as a significant cause of ocular morbidity and blindness especially in developing countries. In this study, we aimed to present the molecular identification and susceptibility of Fusarium isolates causing fungal keratitis in a university hospital in southern Brazil. The samples were identified using the second largest subunit of the RNA polymerase gene (RPB2) and the translation elongation factor 1-alpha (TEF1), while the antifungal susceptibility was tested by the broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI) methodology. The majority of the isolates belonged to the Fusarium solani species complex (F. solani, F. keratoplasticum and F. falciforme) and Fusarium oxysporum species complex. Antifungal susceptibility has shown that amphotericin B and natamycin were the most effective antifungals across all isolates, followed by voriconazole. Variation among Fusarium complexes in their antifungal sensitivities was observed in our study. The identification of Fusarium species from human samples is important not only from an epidemiological viewpoint, but also for choosing the appropriate antifungal agent for difficult-to-treat Fusarium infections such as keratitis.  相似文献   
83.
Cardiac remodeling (CR) is a structural change of the heart due to chronic hemodynamic overload related to changes in both myocyte and extracellular matrix (ECM). We investigated that the imbalance of collagen V promotes cardiomyocyte apoptosis that contributes to heart failure and cell death. Aortic stenosis was induced surgically and male Wistar rats were randomized to 18 weeks (Sham 18?w, n?=?12; AoS 18?w, n?=?12) and severe of heart failure (Sham HF, n?=?12; AoS HF, n?=?12) groups. Functional and structural echocardiogram, immunohistochemistry for Ki-67, TUNEL assay and Immunofluorescence for collagen were performed. Our main results were: (1) Progressive reduction of cardiac functional capacity due to cardiac remodeling with decreased eject fraction in heart failure; (2) Imbalance of collagen deposition with increased, crowded and irregular collagen I in situ expression; (3) Dysregulation of dynamic control of collagen fibers with exposed epitopes of collagen V; (4) Additional apoptosis that are dependent to cardiac injury. The collagen V expression in cardiac remodeling is for the first time described and may be related to additional apoptosis and autoimmune response. Our findings suggest a critical role of collagen V in cardiac remodeling to modulate and promote heart failure and death.  相似文献   
84.
Fallopian tube (FT) and endometrial urocortin 1 (Ucn1) and corticotropin-releasing hormone (CRH)-receptor (CRH-R1/CRH-R2) expression were examined using quantitative real-time polymerase chain reaction (RT-PCR) and immunohistochemistry in nonpregnant and pregnant women (intrauterine, IUP; ectopic pregnancy, EP). Tubal Ucn1 messenger RNA (mRNA) expression was higher in luteal compared to follicular phase (P < .01) and equivalent to follicular phase in FT from EP. Tubal CRH-R1/CRH-R2 mRNA was lower in luteal phase (P < .05) and in FT from EP compared to follicular phase (P < .01). Ucn1 mRNA was lower in endometrium from EP compared to IUP (P < .05). Corticotropin-releasing hormone-R1 mRNA was higher in endometrium from EP compared to viable IUP (P < .05). No differences were observed in CRH-R2 expression. Corticotropin-releasing hormone-R1 protein was primarily localized to epithelium of FT and endometrium. Quantitative analysis of tubal CRH-R1 protein expression reflected that seen at the mRNA level but endometrial expression was equivocal. The demonstration of attenuated tubal/endometrial Ucn1/CRH-R expression in EP further supports a role of the CRH-family in embryo implantation.  相似文献   
85.
Melanomacrophages are the pigmented cells present in the hematopoietic organs. Besides melanin, hemosiderin and lipofuscin are also observed in the melanomacrophages. For the liver, however, numerous studies relate these cells to immunological and metabolic functions. Therefore, the aim of this study is to evaluate the hepatic metabolism by quantifying melanin, hemosiderin and lipofuscin in the anuran Eupemphix nattereri submitted to varying thermal conditions. E. nattereri adult males were separated into three groups, as follows: (i) five animals in the control group were kept at room temperature (27°C); (ii) 30 animals were submitted to hyperthermic (35.1°C); and (iii) 30 to hypothermic (18.9°) conditions. In each experiment, the animals were analyzed and separated into two different treatments: (1) immediately after undergoing the stress; and, (2) after recovering from the stress caused by the stimulus, at three distinct times (12 hr, 24 hr, and 48 hr). Both hyperthermia and hypothermia decreased hepatic pigmentation after thermal stress. The recovered animals of both experimental treatments showed as much pigmentation as the control animals. Thermal stress alters hemosiderin and lipofuscin as well, which may be related to liver function catabolism. In conclusion, liver pigmentation decreased due to temperature variation and duration of thermal stimulation to which the animals were exposed. The increase in temperature rather than hypothermia led to more drastic physiological disorders. In this study, we observed that thermal stress for a short period compromises the morphology and liver function, as observed by the changing pigmentation of melanomacrophages. These analyses can be used as biomarkers of environmental effects. Anat Rec, 297:864–875, 2014. © 2014 Wiley Periodicals, Inc.  相似文献   
86.
The trematode Schistosoma mansoni, an important parasite of humans, is the principle agent of the disease schistosomiasis. In the human host, one of the most important stress factors of this parasite is the oxidative stress generated by both the metabolism of the worm and the immune system of the host. The proteasomal system is responsible for protein homeostasis during oxidative stress. The 26S proteasome is a multicatalytic protease formed by two compartments, a 20S core and regulatory particle 19S, and controls the degradation of intracellular proteins, hence regulating many cellular processes. In the present report, we describe the biochemical characterization and role of the 20S proteasome in the response of adult S. mansoni worms exposed to hydrogen peroxide. Characterization of the response to the oxidative stress included the evaluation of viability, egg production, mortality, tegument integrity, and both expression and activity of proteasome. We observed decreases in viability, egg production as well as 100 % mortality at the higher concentrations of hydrogen peroxide tested. The main changes observed in the tegument of adult worms were peeling as well as the appearance of bubbles and a decrease of spines on the tubercles. Furthermore, there were increases in 26S activity to the same extent as 20S proteasome activity, although there was increase of 20S proteasome content, suggesting that degradation of protein oxidized in adult worms is due to the 20S proteasome. It was demonstrated that adult S. mansoni worms are sensitive to oxidative stress, and that a variety of processes in this parasite are altered under this condition. The work contributes to a better understanding of the mechanisms employed by S. mansoni to survive under oxidative stress.  相似文献   
87.

OBJECTIVES:

Atrial fibrillation is the most common sustained arrhythmia and is associated with poor outcomes, including stroke. The ability of anticoagulation therapy to reduce the risk of stroke has been well established; however, the prevalence of anticoagulation therapy use in the Public Health System is unknown. The aim of this study is to evaluate both the prevalence of anticoagulation therapy among patients with atrial fibrillation and the indications for the treatment.

METHODS:

In this cross-sectional study, we included consecutive patients who had atrial fibrillation documented by an electrocardiogram performed between September 2011 and March 2012 at a university hospital of the Public Health System. The variables analyzed included the risk of a thromboembolic event and/or bleeding, the use of antiplatelet or anticoagulation therapy, the location where the electrocardiogram report was initially reviewed and the specialty of the physician who initially reviewed it.

RESULTS:

We included 162 patients (mean age 68.9 years, 56% men). Hypertension (90.1%), heart failure (53.4%) and stroke (38.9%) were the most prevalent diseases found. Only 50.6% of the patients knew that they had atrial fibrillation. Regarding the use of therapy, only 37.6% of patients classified as high risk according to the CHADS2 scores and 35.5% according to the CHA2DS2VASc used oral anticoagulation. A presumptive diagnosis of heart failure and the fact that the electrocardiogram was evaluated by a cardiologist were the only independent predictors of the use of anticoagulants.

CONCLUSIONS:

Our study found a low prevalence of oral anticoagulation therapy among patients with atrial fibrillation and an indication for stroke prophylaxis for the use of this therapy, including among those with high CHADS2 and CHA2DS2VASc scores.  相似文献   
88.
Objective: To present a case of an early treatment of cardiac intraperitoneal teratoma (IPT) in a newborn and its associated systematic literature review.

Methods: We presented a case of a newborn with IPT but without hydrops and having a good perinatal outcome after cardiac surgery. Using the PubMed database, we conducted a systematic literature review of articles regarding cases with cardiac IPT diagnosed and treated in the neonatal period and published in English from 2004 onward. We excluded cases that involved fetal death or interrupted gestation events.

Results: In total, 38 cases of IPT from 31 articles were included. The mean?±?standard deviation of the gestational age at diagnosis and delivery were 27.9?±?5.7 and 33.0?±?3.5 weeks, respectively, and that of birth weight was 2373?±?834.5?g. The majority of fetuses (42.1%) were males. Pericardial effusion was the most common symptom (60.5%) followed by hydrops (42.1%) and respiratory distress (42.1%). Intrauterine procedure was not performed in 63.1% of cases, and 71.0% of newborns were alive.

Conclusions: IPT in newborns is usually associated with a good prognosis without the need for intrauterine procedures. Cases with IPT-related death are associated with hemodynamic impairment in fetuses with hydrops.  相似文献   
89.
Rheumatoid arthritis (RA) is a chronic inflammatory synovitis, with destruction of juxtaarticular cartilage and bone, likely mediated by lipid mediators, cytokines, and proteases released from inflammatory leukocytes. The mechanisms regulating leukocyte activation in rheumatoid synovium are not fully elucidated. A new family of cell surface proteins termed leukocyte immunoglobulin-like receptors (LIRs) has been shown in vitro to modulate cellular responses through immunoreceptor tyrosine-based inhibitory motifs or through association with the Fc receptor gamma chain that contains immunoreceptor tyrosine-based activation motifs. We studied the expression of inhibitory and activating LIRs in the synovium of six RA patients, three osteoarthritis patients, and three controls by immunohistochemistry. The synovium from patients with early RA showed extensive expression of the inhibitory LIR-2 and the activating LIR-7 on macrophages and neutrophils. Some mast cells and endothelial cells expressed LIR-7. There was limited expression of LIRs in synovium from two patients with long-standing RA, patients with osteoarthritis, and controls. LIR-2 recognizes MHC class I molecules. We therefore suggest that LIRs may regulate the activation of infiltrating leukocytes in synovial tissue and are a potential therapeutic target.  相似文献   
90.
There are reports describing both provocation and inhibition of neurogenic pulmonary edema by anesthetic drugs. Therefore, we compared the effect of two types of anesthesia on the formation of neurogenic pulmonary edema in rats with balloon-induced acute spinal cord injury. Animals with sham procedure (group 1) were anesthesized by intraperitoneal sodium pentobarbital. In the experimental groups, rats were submitted to acute spinal cord lesion by insufflations of a balloon in the epidural space at T8 for 1 min (group 3 under i.p. sodium pentobarbital and group 2 under i.p. xylazine-ketamine anesthesia). In rats with pentobarbital anesthesia, systolic blood pressure doubled the baseline value during compression, whereas this effect was less pronounced in the ketamine-xylazine group. The pulmonary index (100 x wet lung weight/body weight) was 0.395 (+/-0.018) in sham-operated rats, rose to 0.499 (+/-0.060) in group 2, and was maximum under pentobarbital anesthesia (0.639+/-0.14; p=0.0018). Histologic examination of the spinal cord showed parenchymal ruptures and acute hemorrhage. Comparison of the pulmonary index with histologic slides of lung parenchyma revealed that relevant intra-alveolar edema occurred only for index values above 0.55. On electron microscopy, endothelial alterations, and damage of the alveolar lining cells were found. Our study indicates that neurogenic pulmonary edema caused by spinal cord injury is less pronounced in rats under xylazine-ketamine anesthesia, when compared with pentobarbital.  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