首页 | 官方网站   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   2595篇
  免费   143篇
  国内免费   16篇
医药卫生   2754篇
  2023年   16篇
  2022年   19篇
  2021年   56篇
  2020年   36篇
  2019年   51篇
  2018年   56篇
  2017年   63篇
  2016年   62篇
  2015年   82篇
  2014年   100篇
  2013年   123篇
  2012年   172篇
  2011年   169篇
  2010年   111篇
  2009年   78篇
  2008年   154篇
  2007年   157篇
  2006年   137篇
  2005年   142篇
  2004年   144篇
  2003年   116篇
  2002年   104篇
  2001年   68篇
  2000年   61篇
  1999年   48篇
  1998年   25篇
  1997年   22篇
  1996年   24篇
  1995年   12篇
  1994年   9篇
  1993年   20篇
  1992年   42篇
  1991年   27篇
  1990年   18篇
  1989年   22篇
  1988年   23篇
  1987年   13篇
  1986年   15篇
  1985年   22篇
  1984年   9篇
  1983年   11篇
  1982年   8篇
  1981年   7篇
  1980年   10篇
  1979年   20篇
  1978年   10篇
  1977年   12篇
  1976年   7篇
  1975年   7篇
  1972年   7篇
排序方式: 共有2754条查询结果,搜索用时 31 毫秒
11.
BACKGROUND: It has been argued that lay interviewers' use of fully-structured interviews could lead to a diagnostic pattern different to that by treating physicians. Clinical interviewers in community samples should probably identify cases that are closer to those seen in clinical settings. The greatest advantage of using clinical interviewers consists of the immediate assessment of a possible psychopathology, i.e. the evaluation of current disorders. METHODS: Two thousand three hundred and sixty-three citizens from the community of Sesto Fiorentino, Italy, were interviewed by their own general practitioners using the Mini International Neuropsychiatric Interview (MINI). Positive cases for any lifetime psychiatric disorder as well as a random sample of the negative cases were re-interviewed by psychiatrists or trained residents in psychiatry using the Florence Psychiatric Interview (FPI). RESULTS: The point prevalence for any current disorder was 8.7%; the two disorders with the highest prevalence were generalised anxiety disorder (2.9%) and major depressive episode (2.7%). The figures increase about 50% when the sub-threshold sequelae of previous disorders are considered. Current comorbidity was generally high. The one-year prevalence of any disorder was 10.6%. Ninety-two percent of the cases sought help, 82% were being treated at the moment of interview. Social impairment was considerable. CONCLUSIONS: The period prevalence rates for most of the disorders considered were generally comparable with the range defined by previous studies conducted in other Western countries, despite using different methodologies. Conversely, the use of health facilities, the treatment received and the social impairment were much higher than those reported by the other studies, suggesting a greater similarity with the clinical samples.  相似文献   
12.
The relative balance between Th1 and Th2 cytokines appears crucial, since the role of cytokines has been evaluated in several studies by comparison of clinically heterogeneous groups of patients. The aim of this study is to determine the role of proinflammatory Th1 cytokines, interleukin-12 (IL-12) and gamma interferon (IFN-γ), and anti-inflammatory Th2 cytokines, IL-4 and IL-10, in a homogeneous group of patients with uncomplicated Plasmodium falciparum malaria. Levels of IL-12, IFN-γ, Il-4, and IL-10 in serum for 20 adult patients and 15 healthy control subjects were determined by an immunoenzymatic assay. Serum levels of Th1 cytokines, IL-12 (8.6 ± 2.8 pg/ml; controls, 3.2 ± 0.7 pg/ml) and IFN-γ (39.2 ± 67.6 pg/ml; controls, 8.4 ± 6.3 pg/ml), were significantly increased at admission; 3 days later, levels of IL-12 in serum remained significantly high (8.8 ± 2.6 pg/ml), whereas IFN-γ levels returned to control values. The anti-inflammatory response of Th2 cytokines (IL-10 and IL-4) was distinct. Levels of IL-10 in serum were not significantly increased at day 0 and day 3 (306.6 ± 200.4 pg/ml and 56.6 ± 38.4 pg/ml, respectively; controls, 17.4 ± 9.0 pg/ml). In contrast, levels of IL-4 in serum were not increased on admission (3.4 ± 1.2 pg/ml; controls, 2.4 ± 0.8 pg/ml), but at day 3 a moderate and significant increase of IL-4 levels was observed (4.5 ± 1.7 pg/ml). In conclusion, the increase of Th1 cytokine IL-12 and IFN-γ levels during the acute phase of uncomplicated P. falciparum malaria may reflect an early and effective immune response regulated by proinflammatory Th1 cytokines, and in particular IFN-γ may play a role in limiting progression from uncomplicated malaria to severe and life-threatening complications.  相似文献   
13.
 Reduction of an inwardly rectifying K+ current by thyrotropin-releasing hormone (TRH) and caffeine has been considered to be an important determinant of electrical activity increases in GH3 rat anterior pituitary cells. However, the existence of an inwardly rectifying K+ current component was recently regarded as a misidentification of an M-like outward current, proposed to be the TRH target in pituitary cells, including GH3 cells. In this report, an inwardly rectifying component of K+ current is indeed demonstrated in perforated-patch voltage-clamped GH3 cells. The degree of rectification varied from cell to cell, but both TRH and caffeine specifically blocked a fraction of current with strong rectification in the hyperpolarizing direction. Use of ramp pulses to continuously modify the membrane potential demonstrated a prominent blockade even in cells with no current reduction at voltages at which M-currents are active. Depolarization steps to positive voltages at the maximum of the inward current induced a caffeine-sensitive instantaneous outward current followed by a single exponential decay. The magnitude of this current was modified in a biphasic way according to the duration of the previous hyperpolarization step. The kinetic characteristics of the current are compatible with the possibility that removal from inactivation of a fast-inactivating delayed rectifier causes the hyperpolarization-induced current. Furthermore, the inwardly rectifying current was blocked by astemizole, a potent and selective inhibitor of human ether-á-go-go -related gene (HERG) K+ channels. Along with other pharmacological and kinetic evidence, this indicates that the secretagogue-regulated current is probably mediated by a HERG-like K+ channel. Addition of astemizole to current-clamped cells induced clear increases in the frequency of action potential production. Thus, an inwardly-rectifying K+ current and not an M-like outward current seems to be involved in TRH and caffeine modulation of electrical activity in GH3 cells. Received: 15 May 1997 / Received after revision and accepted: 24 July 1997  相似文献   
14.
Background: The differential tolerability profile of various interferon (IFN)-α preparations used in combination with ribavirin for the treatment of chronic hepatitis C needs to be elucidated. Approximately 8% of patients receiving recombinant IFNα-2b plus ribavirin discontinue treatment because of adverse events. Human leucocyte IFNα is deemed to have a better safety profile than recombinant IFNα. We therefore compared the safety profile and efficacy of ribavirin combined with leucocyte IFNα or with recombinant IFNα-2b in treatment-naive patients with chronic hepatitis C. Study design: We randomised 423 patients to either leucocyte IFNα 3MU three times weekly plus ribavirin (210 patients) or the same dose of recombinant IFNα-2b plus ribavirin (213 patients). Patients were treated for 24 weeks and followed-up for a further 48 weeks. The primary endpoint was the safety profile of the two therapies; the secondary endpoint was the rate of sustained response. Results: In patients receiving leucocyte IFNα, the total number of adverse events was lower than in the group receiving recombinant IFNα (259 vs 441 patients), and the percentage of patients discontinuing treatment because of adverse events or laboratory abnormalities was significantly reduced (4% vs 11%; p = 0.013). Sustained response was observed in 47% of patients receiving leucocyte IFNα plus ribavirin and in 44% of patients receiving IFNα-2b plus ribavirin. Conclusions: Both therapeutic regimens were effective in inducing a sustained response in naive patients. However, the safety profile of leucocyte IFNα plus ribavirin was more favourable than that observed with the administration of recombinant IFNα-2b plus ribavirin, suggesting that leucocyte IFNα may be an alternative option in patients with reduced tolerability to other IFNs.  相似文献   
15.
The genetic diversity of HIV-1 strains in Chad was documented with a total of 107 samples from patients attending the general hospital in N'Djamena, the capital city of Chad. The genetic subtypes were identified in the V3-V5 env and p24 gag regions by sequence and phylogenetic tree analyses. Of the 107 strains, 78 had the same subtype/CRF designation between env and gag. Four subtypes and three CRFs were found to cocirculate: subtype A, 20.5%; subtype D, 18.7%; CRF02_AG, 13.1%; CRF11_cpx, 13.1%; subtype G, 3.7%; CRF01_AE, 2.8%; and subtype F1, 0.9%. The remaining 29 strains (27%) had discordant subtypes or CRF designations between env and gag; in 15 of these 29 strains, a CRF was involved in the recombination event, and 10 were subtype G in gag and subtype A in env, forming a separate subcluster within subtypes G and A. Subtype D strains represent almost 20% of the HIV-1 strains circulating in Chad and form a separate subcluster in gag and env. Nearly full-length genome sequencing for two such strains (99TCD-MN011 and 99TCD-MN012) revealed that they represent nonrecombinant subtype D variants. Compared with neighboring countries, the genetic subtype distribution of HIV-1 strains in Chad is unique for several reasons: lower prevalence of CRF02, high prevalence of CRF11 and subtype D, and absence of CRF06. These data clearly show that subtype distribution is very heterogeneous in Africa, probably the result of different founder effects.  相似文献   
16.
17.
The surface expression of given HLA class I alleles protects target cells from lysis mediated by natural killer (NK) clones specific for these (or related) alleles. We could define two groups of NK clones specifically recognizing either Cw4 and related C alleles (“group 1”) or Cw3 and related C alleles (“group 2”), respectively. Monoclonal antibodies (mAb) to class I molecules should interfere with the interaction between NK receptors and class I molecules, thus resulting in lysis of protected target cells. However, none of the numerous available mAb to class I molecules had this effect. Therefore, we attempted to select new mAb on the basis of their ability to induce lysis of Cw4- or Cw3-protected lymphoblastoid cell lines by “group 1” or “group 2” NK clones, respectively. From mice immunized with phytohemagglutinin (PHA)-activated lymphocytes expressing either Cw3 or Cw4 alleles, two mAb were selected, the 6A4 (IgG1) and the A6-136 (IgM), on the basis of their ability to induce lysis of protected target cell. Both mAb immunoprecipitated molecules which, in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gave two bands of 45 and 12 kDa, typical of the class I heavy chain and β2 microglobulin, respectively. It has been proposed (but not proven), that self major histocompatibility complex class I molecules protect normal cells from autologous NK cell lysis. Thus, we used the 6A4 and A6-136 mAb to assess this possibility directly. Cw4-specific (“group 1”) and Cw3-specific (“group 2”) NK clones were isolated from donors expressing the corresponding (or related) protective C alleles. None of these clones lysed autologous PHA-induced blasts, used as target cells. However, addition of the F(ab′)2 of 6A4 mAb or the A6-136 mAb resulted in lysis of autologous target cells by “group 1” or “group 2” NK clones, respectively. These data provide direct evidence that the expression of class I molecules protects normal cells from lysis by autologous NK cells.  相似文献   
18.
19.
20.
Dysfunction of neutrophils (polymorphonuclear leukocytes [PMNL]) and macrophagic cells occurs as a consequence of human immunodeficiency virus type 1 (HIV-1) infection. Macrophages contribute to the resolution of early inflammation ingesting PMNL apoptotic bodies. This study investigated macrophage ability to phagocytose PMNL apoptotic bodies in patients with HIV-1 infection in comparison with uninfected individuals and the effect of HIV Nef protein on apoptotic body phagocytosis to determine if phagocytic activity is impaired by HIV infection. Monocytes/macrophages were isolated from 10 HIV-1-infected patients and from five healthy volunteers, whereas PMNL were isolated from healthy volunteers. Macrophage phagocytosis of apoptotic PMNL was determined by staining of apoptotic bodies with fluorescein-conjugated concanavalin A or with fluorescein-labeled phalloidin. Our data show significant impairment of PMNL apoptotic body macrophage phagocytosis in subjects with HIV-1 infection presenting a concentration of CD4(+) T lymphocytes of >200/mm(3) and in particular in those with <200 CD4(+) T lymphocyte cells/mm(3). In addition, HIV-1 recombinant Nef protein is able to decrease phagocytosis of apoptotic PMNL from normal human macrophages in a dose-dependent manner. The results of our study suggest that impaired macrophage phagocytosis of PMNL apoptotic bodies may contribute to the persistence of the inflammatory state in HIV-infected subjects, especially during opportunistic infections that are often favored by defective phagocytic activity.  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-23

京公网安备 11010802026262号