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   27697篇
  免费   1762篇
  国内免费   151篇
耳鼻咽喉   362篇
儿科学   689篇
妇产科学   710篇
基础医学   4267篇
口腔科学   447篇
临床医学   2217篇
内科学   6921篇
皮肤病学   920篇
神经病学   2791篇
特种医学   713篇
外科学   2816篇
综合类   132篇
一般理论   11篇
预防医学   2022篇
眼科学   532篇
药学   1851篇
中国医学   60篇
肿瘤学   2149篇
  2023年   278篇
  2022年   632篇
  2021年   1051篇
  2020年   542篇
  2019年   837篇
  2018年   891篇
  2017年   668篇
  2016年   792篇
  2015年   853篇
  2014年   1160篇
  2013年   1336篇
  2012年   2058篇
  2011年   2122篇
  2010年   1182篇
  2009年   1090篇
  2008年   1701篇
  2007年   1755篇
  2006年   1606篇
  2005年   1519篇
  2004年   1339篇
  2003年   1247篇
  2002年   1047篇
  2001年   274篇
  2000年   288篇
  1999年   342篇
  1998年   219篇
  1997年   164篇
  1996年   132篇
  1995年   115篇
  1994年   80篇
  1993年   87篇
  1992年   124篇
  1991年   131篇
  1990年   125篇
  1989年   146篇
  1988年   110篇
  1987年   95篇
  1986年   93篇
  1985年   81篇
  1984年   61篇
  1983年   55篇
  1982年   42篇
  1979年   55篇
  1978年   46篇
  1977年   42篇
  1975年   52篇
  1974年   53篇
  1973年   57篇
  1972年   47篇
  1971年   55篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Hepatitis C is the most common indication for liver transplantation. Recurrence of HCV is universal leading to graft failure in up to 40% of all patients. The differentiation between acute rejection and recurrent hepatitis C is crucial as rejection treatments are likely to aggravate HCV recurrence. Histological examination of liver biopsy remains the gold standard for diagnosis of acute rejection but has failed in the past to distinguish between acute rejection and recurrent hepatitis C. We have recently reported that C4d as a marker of the activated complement cascade is detectable in hepatic specimen in acute rejection after liver transplantation. In this study, we investigate whether C4d may serve as a specific marker for differential diagnosis in hepatitis C reinfection cases. Immunohistochemical analysis of 97 patients was performed. A total of 67.7% of patients with acute cellular rejection displayed C4d-positive staining in liver biopsy whereas 11.8% of patients with hepatitis C reinfection tested positive for C4d. In the control group, 6.9% showed C4d positivity. For the first time we were able to clearly demonstrate that humoral components, represented by C4d deposition, play a role in acute cellular rejection after LTX. Consequently C4d may be helpful to distinguish between acute rejection and reinfection after LTX for HCV.  相似文献   
42.

Background  

Streptococcus (S.) pneumoniae meningitis has a high lethality despite antibiotic treatment. Inflammation is a major pathogenetic factor, which is unresponsive to antibiotics. Therefore adjunctive therapies with antiinflammatory compounds have been developed. TNF484 is a TNF-alpha converting enzyme (TACE) inhibitor and has been found efficacious in experimental meningitis. Toll-like receptor 2 (TLR2) contributes to host response in pneumococcal meningitis by enhancing bacterial clearing and downmodulating inflammation. In this study, TNF484 was applied in mice, which lacked TLR2 and exhibited a strong meningeal inflammation.  相似文献   
43.
OBJECTIVE: We investigated whether newborns respond differently to novel and deviant sounds during quiet sleep. METHODS: Twelve healthy neonates were presented with a three-stimulus oddball paradigm, consisting of frequent standard (76%), infrequent deviant (12%), and infrequent novel stimuli (12%). The standards and deviants were counterbalanced between the newborns and consisted of 500 and 750 Hz tones with two upper harmonics. The novel stimuli contained animal, human, and mechanical sounds. All stimuli had a duration of 300 ms and the stimulus onset asynchrony was 1s. Evoked magnetic responses during quiet sleep were recorded and averaged offline. RESULTS: Two deflections peaking at 345 and 615 ms after stimulus onset were observed in the evoked responses of most of the newborns. The first deflection was larger to novel and deviant stimuli than to the standard and, furthermore, larger to novel than to deviant stimuli. The second deflection was larger to novel and deviant stimuli than to standards, but did not differ between the novels and deviants. CONCLUSIONS: The two deflections found in the present study reflect different mechanisms of auditory change detection and discriminative processes. SIGNIFICANCE: The early brain indicators of novelty detection may be crucial in assessing the normal and abnormal cortical function in newborns. Further, studying evoked magnetic fields to complex auditory stimulation in healthy newborns is needed for studying the newborns at-risk for cognitive or language problems.  相似文献   
44.
Adult wound repair occurs with an initial inflammatory response, reepithelialization, and the formation of a permanent scar. Although the inflammatory phase is often considered a necessity for successful adult wound healing, fetal healing studies have shown the ability to regenerate skin and to heal wounds in a scarless manner in the absence of inflammation. The cyclooxygenase-2 (COX-2) enzyme, a known mediator of inflammation, has been shown to contribute to a variety of inflammatory conditions and to the development of cancer in many organs. To examine the role of COX-2 in the wound healing process, incisional wounds were treated topically with the anti-inflammatory COX-2 inhibitor celecoxib. Acutely, celecoxib inhibited several parameters of inflammation in the wound site. This decrease in the early inflammatory phase of wound healing had a significant effect on later events in the wound healing process, namely a reduction in scar tissue formation, without disrupting reepithelialization or decreasing tensile strength. Our data suggest that in the absence of infection, adult wound healing is able to commence with decreased inflammation and that anti-inflammatory drugs may be used to improve the outcome of the repair process in the skin by limiting scar formation.  相似文献   
45.
Functional or unexplained medical symptoms (physical symptoms that are not adequately explained by organic factors and where a major role for psychological factors is assumed) are common amongst children in the general population but can also be an expression of somatisation and somatoform disorders. Co-morbid psychopathology is common. We describe measures mostly used in research into problems related to somatisation in children and adolescents that may be helpful to clinical researchers. Some address the nature and severity of physical symptoms, others document illness attitudes, beliefs and functional impairment, and a third group assesses emotional symptoms. Questionnaires can be helpful for clinicians in quantifying (i) the nature and severity of somatic symptoms and associated functional impairment, (ii) contributory health attitudes and illness beliefs and (iii) co-morbid or primary anxiety and depressive disorders. Together with pain and activity diaries and careful documentation of school attendance, these measures may also be helpful in monitoring treatment response.  相似文献   
46.
According to contemporary views, the glutamatergic system is implicated in the pathogenesis of schizophrenia, and atypical neuroleptics exert their effects (at least partially) through the glutamatergic system. Immunoreactive glutamate-metabolising enzymes, such as glutamine synthetase-like protein (GSLP) and two glutamate dehydrogenase isoenzymes (GDH), have been discovered in human platelets. The amount of GSLP in the platelets of 40 chronic patients with schizophrenia was found to be significantly higher than in 33 controls (consistent with our previous finding of increased amounts of GSLP in the prefrontal cortex of chronic schizophrenia patients). Moreover, survival analysis of the group of patients treated with olanzapine for 28 weeks showed that the larger amount of GSLP measured in platelets before treatment, the shorter the treatment time needed to achieve a positive clinical response (defined a priori as > or = 20% reduction in PANSS total score from the initial level before the treatment). Hence, GSLP level may serve as a predictor of the treatment duration to achieve a positive outcome with olanzapine. Both GSLP and GDH were found significantly changed in the course of treatment; hence, treatment with olanzapine influences the amounts of glutamate-metabolising enzymes in the platelets of chronic schizophrenia patients.  相似文献   
47.
The purpose of this study was to describe MR findings in full-thickness tears of the rotator cuff. Of 102 shoulders examined by MR imaging, 31 were found to have a full-thickness tendon tear at arthroscopy/bursoscopy (five shoulders) or open surgery (26 shoulders). All shoulders were imaged in oblique coronal and axial planes. MR images of the 102 shoulders were evaluated for (1) the presence of fluid in the subacromial and subdeltoid bursae; (2) abnormal signal of the supraspinatus, subscapularis, infraspinatus, and teres minor tendons; (3) interruption of tendon continuity and thinning of the tendon; and (4) proximal retraction of the junction of the muscle and tendon. The presence or absence of each finding was determined by consensus of two radiologists, who interpreted the images without knowledge of the surgical findings. Results in those 31 shoulders with proved full-thickness tears were: fluid in the subacromial bursae (29 shoulders), interruption of tendinous continuity (22 shoulders), focally increased signal of the tendon equivalent to that of water (27 shoulders), and musculotendinous retraction (24 shoulders). The finding of subacromial fluid was a sensitive indicator (93%) of a full-thickness tear, and interruption of tendinous continuity was a specific finding (96%) in diagnosing a full-thickness tear. Our experience shows interruption of tendon continuity is the most specific MR finding of full-thickness rotator cuff tears, while subacromial fluid is the most common finding.  相似文献   
48.
The present work tries to establish the antioxidant capacity of the peripheral nervous tissue of the rat, in terms of the enzymatic activities present in this tissue that either prevent the formation of activated species as the semiquinone radical (DT-diaphorase), protect against activated oxygen species (superoxide dismutase, glutathione peroxidase), conjugate natural toxic products or xenobiotics (glutathione S-transferases, especially the activity conjugating 4-hydroxy-nonenal), or complete the glutathione system metabolism (glutathione disulfide reductase, γ-glutamyl transpeptidase). All the activities studied are lower in this tissue than they are in liver, except for γ-glutamyl transpeptidase. The relevance of the results obtained and its possible relationship with different neuropathies is discussed. It is concluded that the peripheral nervous tissue is by far less protected than the liver against oxidative damage.  相似文献   
49.
Central administration of ACTH in rats induces yawning and stretching. In order to study the effects of REM sleep deprivation on ACTH-induced yawning, the peptide was injected immediately after the REM sleep deprivation period or 24 h later. REM sleep deprivation impaired ACTH-induced yawning, but after a 24-hour recovery period, rats displayed a number of yawns similar to those in control animals. Implications for an involvement of dopaminergic and mainly cholinergic systems are discussed.  相似文献   
50.
Hereditary hypertriglyceridemic rats (hHTg) were developed as a new genetic model for the study of relationships between blood pressure (BP) and metabolic abnormalities. This strain has been produced by selective inbreeding from Wistar rats according to the rise of plasma triglycerides induced by a high-sucrose diet. Though hHTg rats display hypertriglyceridemia, impaired glucose tolerrance, hyperinsulinemia, insulin resistance and increased BP even without nutritional stimuli, high sucrose feeding further aggravates these symptoms. High plasma triglycerides levels in hHTg rats seem to be a consequence of their hyperproduction. Impaired insulin action is responsible for the defective glucoregulation in this strain. The loss of insulin responsiveness might be due to a reduction in the number of glucose transporters. Highly significant relationships among plasma triglycerides, ouabain-resistant Na+ transport and BP were demonstrated in the hHTg rats. Segregating populations (F2 hybrids) should be used for genetic analysis of the primary role of lipid and/or ion transport abnormalities in the pathogenesis of this form of genetic hypertension.  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