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   8667篇
  免费   738篇
  国内免费   20篇
耳鼻咽喉   366篇
儿科学   230篇
妇产科学   229篇
基础医学   1002篇
口腔科学   159篇
临床医学   822篇
内科学   1766篇
皮肤病学   138篇
神经病学   1111篇
特种医学   390篇
外科学   1049篇
综合类   199篇
一般理论   10篇
预防医学   687篇
眼科学   126篇
药学   623篇
  1篇
中国医学   7篇
肿瘤学   510篇
  2021年   93篇
  2020年   58篇
  2019年   91篇
  2018年   124篇
  2017年   95篇
  2016年   97篇
  2015年   149篇
  2014年   187篇
  2013年   266篇
  2012年   316篇
  2011年   384篇
  2010年   235篇
  2009年   224篇
  2008年   347篇
  2007年   399篇
  2006年   377篇
  2005年   382篇
  2004年   360篇
  2003年   336篇
  2002年   295篇
  2001年   299篇
  2000年   355篇
  1999年   300篇
  1998年   140篇
  1997年   115篇
  1996年   91篇
  1995年   105篇
  1994年   98篇
  1993年   81篇
  1992年   197篇
  1991年   160篇
  1990年   215篇
  1989年   194篇
  1988年   199篇
  1987年   188篇
  1986年   186篇
  1985年   181篇
  1984年   127篇
  1983年   115篇
  1982年   73篇
  1981年   85篇
  1980年   71篇
  1979年   103篇
  1978年   75篇
  1977年   75篇
  1976年   53篇
  1975年   67篇
  1974年   56篇
  1973年   62篇
  1972年   58篇
排序方式: 共有9425条查询结果,搜索用时 46 毫秒
41.
This study was undertaken to record the Brainstem Evoked Responses in a group of 20 diabetic patients with normal hearing and were compared with responses of another group of 20 normal individuals. Eighth nerve transmission till the level of cochlear nucleus was found to be normal in diabetics. The delay in latency of Wave III, IV and V and interpeak latencies (I–III, I–V) were noted to be statistically significant, thus suggesting the presence of central neuropathy in patients with diabetes. No significant sex difference on latency of waves was observed.  相似文献   
42.
Transcranial Doppler ultrasound (TDU) recording is presented as a diagnostic method for the evaluation of the cerebral cross-flow in patients in whom, for therapeutic reasons, ligature or resection of the common or internal carotid artery is planned. Examinations were performed under normal conditions and while using manual compression of the ipsilateral carotid artery. Patients with various skull base and neck tumors were examined and in all patients an immediate decrease of the flow velocity in the middle cerebral artery (MCA) of 25 to 90% was registered. In 39% of these patients the flow velocity of the MCA reached 90% or more of its value under normal conditions within a short interval. In 29% of the patients the flow velocity of this vessel under manual compression of the carotid artery remained under 50% of its original value. In 68% of the cases TDU recording with manual compression of the carotid artery showed reliable results for the function of cerebral collateralization as a prognostic factor of ischemic risk due to hemodynamic changes after carotid ligature. In these cases no further examination of the cerebral cross-flow conditions was carried out. This method is convenient, harmless to the patient, inexpensive, does not require sophisticated equipment, and yields reproducible results when compared with cerebral angiography.  相似文献   
43.
Objective:  This study determined the clinical predictors of suicidal behavior during a 2-year follow-up of patients with bipolar disorder presenting with a major depressive episode (MDE).
Method:  Sixty four patients with DSM-III-R bipolar disorder were assessed at presentation for treatment of an MDE. Correlates of past suicidal behavior were determined by comparing patients with and without a history of suicide attempts using a t -test, Wilcoxon test or chi-squared test of independence on individual explanatory variables. Putative predictors of attempts during the follow-up period were tested separately using Cox proportional hazards regression analysis.
Results:  Twelve of 64 patients had at least one suicide attempt in the follow-up period, five of them attempted in the first 2 months and seven around or shortly after the 1-year follow-up visit. All attempters had a history of past suicide attempts. Most predictors of future suicidal behavior were correlates of past suicidal behavior. Family history of suicide acts and comorbid borderline personality disorder predicted early attempts, while younger age, high hostility scores, number of past attempts, subjective pessimism as reflected in depression and suicidal ideation, and few reported reasons for living predicted suicidal acts during the whole period.
Conclusion:  In this data set of bipolar patients we noted an intriguing picture of two clusters of suicide attempts. Hostility was the strongest risk factor. These findings may have implications in both the identification of at-risk patients and the timing of clinical interventions including aggressive pharmacotherapeutic prophylaxis to prevent relapse or recurrence of depressive symptomatology.  相似文献   
44.
Objectives:  The aims of this paper are to provide an overview of neuroimaging findings specific to bipolar disorder and suicide, and to consider rational approaches to the design of future in vivo studies in youth at risk.
Methods:  Neuroimaging and related neurobiological literature pertaining to bipolar disorder and suicide in adult and pediatric samples was reviewed in a non-quantitative manner.
Results:  Specific structural and functional brain findings in bipolar disorder are described, where possible in the context of relevant current neurobiological theories of etiology. Diagnostic and prognostic implications are discussed.
Conclusions:  The simultaneous use of complementary neurobiological approaches may be a powerful way of identifying and validating factors reliably associated with bipolar disorder and suicide. A profile of neurobiological markers with which to screen for bipolar disorder and suicide risk may provide for earlier and more accurate diagnosis, perhaps even in the pre- or subsyndromal stages in high-risk youth.  相似文献   
45.
Objectives:  The goal of this retrospective study was to examine factors differentiating persons with bipolar disorder who did or did not have comorbid lifetime substance use disorders (SUD) at an index assessment. We also explored the chronology of onset of mood and SUD.
Methods:  We studied 146 subjects with DSM-defined bipolar disorder. Subgroups with and without lifetime SUD were compared on demographic and clinical measures.
Results:  Substance abuse disorders in this bipolar sample were associated with male sex, impulsive-aggressive traits, comorbid conduct and Cluster B personality disorders, number of suicide attempts and earlier age at onset of a first mood episode. In a multivariable logistic regression analysis, male sex and aggression and possibly earlier age at mood disorder onset were associated with SUD. In those with or without SUD, the first mood episode tended to be depressive and to precede the onset of SUD.
Conclusions:  In persons with bipolar disorder, an earlier age of onset and aggressive traits appear to be factors associated with later development of comorbid SUD.  相似文献   
46.
The pattern of cancer in white and Asian (Indian, Pakistani, and Bangladeshi) children living in the West Midlands Health Authority Region was investigated using age standardised incidence rates. Two sets of rates were calculated, a 10 year rate (1982-91) using survey based estimates of the ethnic population and a four year rate (1989-92) using the ethnic population counts from the 1991 census. The 10 year rates showed a significantly higher annual incidence of cancer in Asian (159.1/million/year) than in white (130.8) children. The pattern of cancers in Asian children was different, with an excess of lymphomas and germ cell tumours, and a deficit of rhabdomyosarcomas. These findings were confirmed by the four year rates. Although underestimation of the Asian population probably contributes to the apparent excess, there remains cause for concern that UK Asian children may be at higher risk of cancer. Accurate ethnic population figures and confirmatory studies are urgently required.  相似文献   
47.
Summary Twenty-five shoulders were dissected in cadavers in order to observe the presence of the inferior transverse ligament, the spinoglenoid ligament, and its relationship to the spinoglenoid notch and the suprascapular nerve. The ligament was found to be absent in 50% of females and rudimentary in one female, but absent in only 13% of the male shoulders. The distance between the ligament and the bone, and from the ligament to the nerve was similar in males and females, but the variation was greater in males. These findings may explain the observation that distal suprascapular nerve entrapment occurs mostly in men.
Résumé Les auteurs ont disséqué vingt-cinq épaules de cadavres afin de vérifier la présence d'un ligament transversal inférieur, le ligament spinoglénoïdien, ainsi que ses rapports avec l'échancrure spino-glénoïdienne et le nerf sus-scapulaire. L'absence de ce ligament a été constatée chez 50% des sujets féminins et il était rudimentaire chez l'un d'entre eux. Chez les sujets masculins, il n'était absent que dans 13% des cas. La distance entre le ligament et l'os, et entre le ligament et le nerf était semblable chez les hommes et chez les femmes, mais les variations étaient plus importantes chez les hommes. Ces observations peuvent expliquer que la compression distale du nerf sus-scapulaire survienne plus fréquemment chez l'homme.
  相似文献   
48.
This paper introduces the idea of castration desire: the desire to lose the penis to strengthen identification with the mother, to deny difference and thereby maintain the phantasy of fusion. Castration desire is therefore linked to the regressive part of the personality that seeks to avoid differentiation. In this context, castration anxiety is seen as a later development that actively promotes separation and individuation from the mother. These issues are explored using clinical and mythological examples.  相似文献   
49.
50.
These investigations test the hypothesis developed previously, that there are biomolecules which control and integrate cellular differentiation. Our specific interest in cellular differentiation lies in the area of what we refer to as basal or primitive cellular differentiation mechanisms. These mechanisms are common to all cells, and are required for simple recognition and growth regulation. We have investigated two models, the IMR-90 human fetal lung fibroblast model as a representative of normal growth control, and the CG model, canine glioma cells, a transplantable growth transformed cell line. These two models represent normal, and aberrant cellular differentiation control. In previous studies we have shown that the arrangement of the cell surface oligosaccharide structure on these cell types are predictive of phenotypic transition. We have developed, and partially characterized a series of BIOMODULATORS (BM) which delay the onset of display of neoplastic cells. Three classes of BIOMODULATOR have been explored; (1) a large molecular weight natural product (25-35 kDa), PokeWeed Mitogen (PWM); (2) a small molecular weight natural product (500 Da) Cellular Activator and Differentiator (CAD) and a number of natural and synthetic analogs; and (3) an indolizidine alkaloid natural product, Swainsonine (Sw) which has a known cellular target (oligosaccharide biosynthesis). Preliminary data is presented which structurally links some of these BIOMODULATORS in terms of their effective stereochemistry. These BIOMODULATORS, when used before PDL 38, prevent the cell surface oligosaccharide display changes typical of morphological senescence and delay their onset to PDL 100 or more. These BIOMODULATORS also appear to have regulatory effects on the neoplastic cell models. This re-regulation results in increases in generation time and an increase in the ability of these cells to be recognized by cytotoxic lymphocytes. Proton NMR linewidth measurements of the fraction of 'bound' water associated with the cellular surface of treated and untreated cell populations showed induced physical changes in the cell surface related to the use of the BIOMODULATOR and correlated to the oligosaccharide display changes. These data were interpreted as indicating an increase in the organizational level of these cells. The data for normal and neoplastic cell populations are compared and contrasted in an effort to form the basis for an analytical approach to the control and integration of differentiation mechanisms.  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