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   26709篇
  免费   1694篇
  国内免费   139篇
耳鼻咽喉   286篇
儿科学   666篇
妇产科学   540篇
基础医学   4128篇
口腔科学   1174篇
临床医学   2444篇
内科学   6036篇
皮肤病学   695篇
神经病学   2357篇
特种医学   651篇
外科学   2561篇
综合类   100篇
一般理论   10篇
预防医学   2516篇
眼科学   589篇
药学   1760篇
中国医学   114篇
肿瘤学   1915篇
  2024年   33篇
  2023年   268篇
  2022年   625篇
  2021年   1070篇
  2020年   633篇
  2019年   851篇
  2018年   963篇
  2017年   669篇
  2016年   803篇
  2015年   861篇
  2014年   1154篇
  2013年   1462篇
  2012年   2271篇
  2011年   2362篇
  2010年   1241篇
  2009年   1027篇
  2008年   1765篇
  2007年   1700篇
  2006年   1554篇
  2005年   1452篇
  2004年   1246篇
  2003年   1093篇
  2002年   969篇
  2001年   155篇
  2000年   131篇
  1999年   153篇
  1998年   154篇
  1997年   128篇
  1996年   105篇
  1995年   83篇
  1994年   80篇
  1993年   75篇
  1992年   100篇
  1991年   91篇
  1990年   90篇
  1989年   82篇
  1988年   84篇
  1987年   65篇
  1986年   84篇
  1985年   92篇
  1984年   70篇
  1983年   62篇
  1982年   38篇
  1981年   38篇
  1979年   48篇
  1978年   37篇
  1977年   33篇
  1975年   35篇
  1974年   38篇
  1973年   31篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
51.
Patients often cite lack of retention and poor aesthetics as reasons for not wearing their partial dentures. Traditional metal alloy clasps have been shown to exert forces on abutment teeth that exceed those capable of producing tooth movement. In addition, metal display on anterior teeth is often unacceptable. The technopolymer materials are purported to have superior flexibility and exert less force than the metals. This study compared the flexibility and forces produced by technopolymer clasps with those exerted by cobalt-chromium and titanium clasps. The results showed that the technopolymer clasps were up to ten times as flexible as the metal clasps, and they returned to their pretest dimensions after being stretched. In addition, they exerted forces on the abutment teeth that fall within the range of those considered safe for use. This coupled with their pleasing aesthetics makes them suitable for use on periodontally compromised teeth, those with deep undercuts and on anterior teeth.  相似文献   
52.
Patients with Taylor-type focal cortical dysplasia (TTFCD) generally present with medically intractable epilepsy and impaired neurological and/or intellectual functioning. Surgery usually proves to be the only treatment approach leading to control of seizures. We describe a 17-year-old girl with TTFCD who exhibited a very long period of seizure remission. Combined clinical and neuroimaging findings were compatible with a diagnosis of a balloon cell-subtype TTFCD. As for the clinical course, partial motor seizures began at one year of age and ceased at five: our patient has had no seizure recurrence over a 12-year-follow-up. Moreover, throughout the 15-year follow-up, neurological examinations and cognitive abilities always remained within normal limits. Neuropsychological assessment clearly showed no impairments in executive functions: planning abilities, working memory, attention and impulse control, or constructive aspects of motor coordination. The predominant deficits pertained to verbal abilities in the context of borderline intellectual performances. To our knowledge, this case report documents the longest duration of seizure remission in a patient with TTFCD, thus emphasizing the possible benign course of such dysplastic lesions which usually have a poor prognosis, leading to early surgical treatment.  相似文献   
53.
In this study, ethnographic interviews were used to identify first-time fathers' experiences of the birth of their first child. Fourteen fathers were interviewed, and prenatal expectations of the experience are compared with the fathers' perceptions after the birth. Although the fathers expected to be treated as part of a laboring couple, they found that they were relegated to a supporting role. Initially the fathers were confident of their ability to support their wives, but they found that labor was more work than they had anticipated. They became fearful of the outcome, but hid these fears from their partners. Later, they found that their focus moved from their wives to their babies at the time of birth. The men all completed the experience with an enhanced respect for their wives. Fathers should be included in labor management plans and need support for their role as coach, particularly when their wives experience pain. They also need to be encouraged to eat and take a break from their wives' labor when appropriate.  相似文献   
54.
The inhibition of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to the GABAA receptor by the insecticide γ-hexachlorocyclohexane, lindane, was studied in several brain regions and using different membrane preparation methods, both in vitro and after dosing the animals with the chemical. In the latter studies, the amount of lindane remaining in the membrane suspensions used for binding assays was determined. In vitro data showed values of IC50 from 150 to 1675 nM, varying in function of the membrane preparation method used. This may account for the discrepancies in IC50 values found in the literature. IC50 values within the range of 150–250 nM were determined using extensively washed membranes from several brain regions, so no evidence arose for brain regional differences in the affinity of lindane for the TBPS binding site. After different schedules of acute treatment with lindane, we found a manifest relationship between the extent of the observable inhibition of [35S]TBPS binding and the lindane amount remaining in the membrane suspensions used for binding assays. This relationship was in good agreement with the in vitro data, so no support for an in vivo acute regulation of the binding site was obtained.  相似文献   
55.
Members of the SR family of pre-mRNA splicing factors are phosphoproteins that share a phosphoepitope specifically recognized by monoclonal antibody (mAb) 104. Recent studies have indicated that phosphorylation may regulate the activity and the intracellular localization of these splicing factors. Here, we report the purification and kinetic properties of SR protein kinase 1 (SRPK1), a kinase specific for SR family members. We demonstrate that the kinase specifically recognizes the SR domain, which contains serine/arginine repeats. Previous studies have shown that dephosphorylated SR proteins did not react with mAb 104 and migrated faster in SDS gels than SR proteins from mammalian cells. We show that SRPK1 restores both mobility and mAB 104 reactivity to a SR protein SF2/ASF (splicing factor 2/alternative splicing factor) produced in bacteria, suggesting that SRPK1 is responsible for the generation of the mAb 104-specific phosphoepitope in vivo. Finally, we have correlated the effects of mutagenesis in the SR domain of SF2/ASF on splicing with those on phosphorylation of the protein by SRPK1, suggesting that phosphorylation of SR proteins is required for splicing.  相似文献   
56.
We used arthrotomography to study the glenoid labrum in 114 patients. Sixty-nine of the patients had anatomic instability of the shoulder (including recurrent dislocation and subluxation of the shoulder), and 45 patients had functional instability of the shoulder (denoted by chronic pain, clicking of the joint, and the sensation that an unstable condition exists without the objective signs of it). Labral tears were revealed arthrotomographically in 86% of the patients with anatomic instability, while only 40% of the patients with functional instability had labral abnormalities, and these were primarily of minor severity. Fifty-six patients (44 of whom had anatomic instability; 12, functional instability) required surgery. The surgical findings were correlated with the arthrotomographic findings, and no false-positive results were revealed. However, arthrotomography demonstrated only part of the pathologic condition of two patients. These results confirm that there is a strong correlation between labral pathologic conditions and anatomic instability of the shoulder. Arthrotomographic studies have a great impact on the selection of therapy in cases of both anatomic and functional instability of the shoulder.  相似文献   
57.
A 20-day treatment with LF15-0195, a deoxyspergualine analog, induced long-term heart allograft survival in the rat without signs of chronic rejection. LF15-0195-treated recipients did not develop an anti-donor alloantibody response. Analysis of graft-infiltrating cells, IL10, TNFalpha, IFNgamma mRNA and iNOS protein expression in allografts, 5 days after transplantation, showed that they were markedly decreased in allografts from LF15-0195-treated recipients compared with allografts from untreated recipients. Surprisingly, spleen T cells from LF15-0195 recipients, 5days after grafting, were able to proliferate strongly in vitro, when stimulated with donor cells, but had reduced mRNA expression for IFNy compared with spleen T cells from untreated graft recipients. Furthermore, when T cells from naive animals were stimulated in vitro, using anti-CD3 and anti-CD28, LF15-0195 also increased T-cell proliferation in a dose-dependent fashion: however, these cells expressed less of the Th1 -related cytokines, IFNgamma and IL2, compared with untreated cells, suggesting that LF15-0195 could act on T-cell differentiation. In conclusion, we show here that a short-term treatment with LF15-0195 induced long-term allograft tolerance, decreasing the in situ anti-donor response, and we illustrate evidence for the development of regulatory mechanisms.  相似文献   
58.
Typical (TPP) and atypical (APP) perfusion patterns (PP) may be seen in ictal SPECT of patients with temporal lobe epilepsy (TLE). APP may pose problem in the lateralization of the epileptogenic zone (EZ). We aimed to investigate predictive variables for the occurrence of TPP and APP. Fifty-one TLE patients were submitted to successful anterior-mesial temporal lobectomy. Univariate (UVA) and multivariate (MVA) analysis were performed upon clinical data, distribution of interictal spikes, and ictal chronology of seizures. From MVA, a final predictive model (FPM) was determined to better predict TPP and APP. Forty patients showed TPP (78.5%) and 11 patients APP (21.5%). Accuracy of ictal SPECT was higher in the unilateral (UIS) than in the bilateral (BIS) interictal spikes group (P = 0.05). FPM showed that patients exhibiting BIS, with shorter proportion of the electrographic seizure occurring after completion of tracer injection, and longer clinical than EEG seizure duration had more APP (P = 0.003). Generalized tonic-clonic seizures did not result in more APP. We concluded that analysis of ictal SPECT in TLE requires the knowledge of TPP and APP, the distribution of interictal spikes on temporal lobes and the ictal chronology of seizures. BIS showed that beyond a more complex epileptogenicity and seizure propagation, they may also lead to APP.  相似文献   
59.
Ischemia negatively affects mitochondrial function by inducing the mitochondrial permeability transition (MPT). The MPT is triggered by oxidative stress, which occurs in mitochondria during ischemia as a result of diminished antioxidant defenses and increased reactive oxygen species production. It causes mitochondrial dysfunction and can ultimately lead to cell death. Therefore, drugs able to minimize mitochondrial damage induced by ischemia may prove to be clinically effective. We analyzed the effect of carvedilol, a beta-blocker with antioxidant properties, on mitochondrial dysfunction. Carvedilol decreased levels of TBARS (thiobarbituric acid reactive substances), an indicator of oxidative stress, which is consistent with its antioxidant properties. Regarding cell death by apoptosis, although ischemia did increase caspase-8-like activity, there were no changes in caspase-3-like activity, which is activated downstream of caspase-8; this may indicate that the apoptotic cascade is not activated by 60 minutes of ischemia. We conclude that carvedilol protects ischemic mitochondria by preventing oxidative mitochondrial damage, and, by so doing, it may also inhibit the formation of the MPT pore.  相似文献   
60.
Summary: The most common human viruses have different abilities to establish persistent chronic infection. Virus‐specific T‐cell responses are critical in the control of virus replication and in the prevention of disease in chronic infection. A large number of phenotypic markers and a series of functions have been used to characterize virus‐specific CD4+ and CD8+ T‐cell responses, and these studies have shown great phenotypic and functional heterogeneity of the T‐cell responses against different viruses. The heterogeneity of the T‐cell response has been proposed to be specific to each virus. However, over the past 2 years, several studies have provided evidence that the phenotypic and functional heterogeneity of CD4+ and CD8+ T‐cell responses is predominantly regulated by the levels of antigen load. The levels of antigen load modulate the phenotypic and functional patterns of the T‐cell response within the same virus infection. Furthermore, the functional characterization of virus‐specific CD4+ and CD8+ T‐cell responses has identified signatures of protective antiviral immunity. Polyfunctional, i.e. interleukin‐2 and interferon‐γ (IFN‐γ) secretion and proliferation, and not monofunctional, i.e. IFN‐γ secretion, CD4+ and CD8+ T‐cell responses represent correlates of protective antiviral immunity in chronic virus infections.  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