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   1612篇
  免费   93篇
  国内免费   51篇
耳鼻咽喉   10篇
儿科学   71篇
妇产科学   34篇
基础医学   175篇
口腔科学   143篇
临床医学   137篇
内科学   304篇
皮肤病学   27篇
神经病学   138篇
特种医学   153篇
外科学   139篇
综合类   22篇
一般理论   1篇
预防医学   147篇
眼科学   34篇
药学   157篇
中国医学   16篇
肿瘤学   48篇
  2023年   10篇
  2022年   24篇
  2021年   36篇
  2020年   29篇
  2019年   50篇
  2018年   47篇
  2017年   26篇
  2016年   33篇
  2015年   45篇
  2014年   60篇
  2013年   70篇
  2012年   110篇
  2011年   116篇
  2010年   74篇
  2009年   67篇
  2008年   68篇
  2007年   96篇
  2006年   67篇
  2005年   49篇
  2004年   38篇
  2003年   35篇
  2002年   43篇
  2001年   29篇
  2000年   28篇
  1999年   34篇
  1998年   48篇
  1997年   37篇
  1996年   40篇
  1995年   26篇
  1994年   19篇
  1993年   23篇
  1992年   17篇
  1991年   12篇
  1990年   18篇
  1989年   33篇
  1988年   35篇
  1987年   27篇
  1986年   23篇
  1985年   17篇
  1984年   9篇
  1983年   11篇
  1982年   9篇
  1981年   9篇
  1980年   9篇
  1978年   9篇
  1977年   11篇
  1976年   8篇
  1975年   8篇
  1974年   3篇
  1968年   3篇
排序方式: 共有1756条查询结果,搜索用时 15 毫秒
91.
Tourette syndrome (TS) and chronic motor/vocal tics (CMVT) are both common disorders in patients with obsessive compulsive disorder (OCD). However, there have been few studies evaluating the differences between the OCD with TS and OCD with CMVT subgroups. This study was conducted in order to further investigate possible differences between the expression of the OCD phenotype in OCD with TS and that seen in OCD with CMVT. One hundred and fifty-nine outpatients referred to an OCD research program were evaluated using the following instruments: the Structured Clinical Interview for DSM-IV; the Yale-Brown Obsessive Compulsive Scale; the Yale Global Tic Severity Scale; and the USP-HARVARD Repetitive Behaviors Interview. Patients were divided into three groups: OCD patients without tics (OCD − TICS, n = 98), OCD patients with chronic motor or vocal tics (OCD + CMVT, n = 31) and OCD patients with TS (OCD + TS, n = 30). OCD + CMVT patients were similar to OCD + TS patients regarding the frequency of intrusive sounds, repeating behaviors, counting and tic-like compulsions (in both cases more frequent than in OCD − TICS patients). For age at obsessive-compulsive (OC) symptom onset, sensory phenomena score, number of comorbidities, frequency of somatic obsessions, bodily sensations and just-right perceptions, OCD + CMVT patients tended to be in between the other two groups. Our results suggest that there are qualitative and quantitative differences in the phenotypic expression of tic disorders in OCD patients, depending on whether the subject has TS or only CMVT.  相似文献   
92.
The authors prospectively studied transcranial Doppler changes in patients with refractory congestive heart failure before and after cardiac transplantation. They evaluated 22 patients preoperatively and 14 patients after transplantation. Mean postoperative flow velocity increased by 53.3% (p < 0.0001). Preoperative waveform changes became normal after transplantation.  相似文献   
93.
94.
Nitric oxide (NO) is a paramagnetic gas that has been implicated in a wide range of biologic functions. The common pathway to evoke the functional response frequently involves the formation of an iron- nitrosyl complex in a target (heme) protein. In this study, we report on the interactions between NO and cobalt-containing vitamin B12 derivatives. Absorption spectroscopy showed that of the four Co(III) derivatives (cyanocobalamin [CN-Cbl], aquocobalamin [H2O-Cbl], adenosylcobalamin [Ado-Cbl], and methylcobalamin [MeCbl]), only the H2O- Cbl combined with NO. In addition, electron paramagnetic resonance spectroscopy of H2O-Cbl preparations showed the presence of a small amount of Cob-(II)alamin that was capable of combining with NO. The Co(III)-NO complex was very stable, but could transfer its NO moiety to hemoglobin (Hb). The transfer was accompanied by a reduction of the Co(III) to Co(II), indicating that NO+ (nitrosonium) was the leaving group. In accordance with this, the NO did not combine with the Hb Fe(II)-heme, but most likely with the Hb cysteine-thiolate. Similarly, the Co(III)-NO complex was capable of transferring its NO to glutathione. Ado-Cbl and Me-Cbl were susceptible to photolysis, but CN- Cbl and H2O-Cbl were not. The homolytic cleavage of the Co(III)-Ado or Co(III)-Me bond resulted in the reduction of the metal. When photolysis was performed in the presence of NO, formation of NO-Co(II) was observed. Co(II)-nitrosyl oxidized slowly to form Co(III)-nitrosyl. The capability of aquocobalamin to combine with NO had functional consequences. We found that nitrosylcobalamin had diminished ability to serve as a cofactor for the enzyme methionine synthase, and that aquocobalamin could quench NO-mediated inhibition of cell proliferation. Our in vitro studies therefore suggest that interactions between NO and cobalamins may have important consequences in vivo.  相似文献   
95.
IntroductionCompulsive buying (CB) is currently classified as an impulse control disorder (ICD) not otherwise classified. Compulsive buying prevalence is estimated at around 5% of the general population. There is controversy about whether CB should be classified as an ICD, a subsyndromal bipolar disorder (BD), or an obsessive-compulsive disorder (OCD) akin to a hoarding syndrome. To further investigate the appropriate classification of CB, we compared patients with CB, BD, and OCD for impulsivity, affective instability, hoarding, and other OCD symptoms.MethodEighty outpatients (24 CB, 21 BD, and 35 OCD) who were neither manic nor hypomanic were asked to fill out self-report questionnaires.ResultsCompulsive buying patients scored significantly higher on all impulsivity measures and on acquisition but not on the hoarding subdimensions of clutter and “difficulty discarding.” Patients with BD scored higher on the mania dimension from the Structured Clinical Interview for Mood Spectrum scale. Patients with OCD scored higher on obsessive-compulsive symptoms and, particularly, higher on the contamination/washing and checking dimensions from the Padua Inventory; however, they did not score higher on any hoarding dimension. A discriminant model built with these variables correctly classified patients with CB (79%), BD (71%), and OCD (77%).ConclusionPatients with CB came out as impulsive acquirers, resembling ICD- rather than BD- or OCD-related disorders. Manic symptoms were distinctive of patients with BD. Hoarding symptoms other than acquisition were not particularly associated with any diagnostic group.  相似文献   
96.
97.
98.
Resting neutrophils may be "primed" to augmented effector function, eg, superoxide (O2-) production in the respiratory burst, upon a second stimulation with a variety of soluble agonists including formylated methionyl-leucyl-phenylalanine (FMLP) and phorbol myristate acetate (PMA). At priming concentrations of FMLP (5 x 10(-9) mol/L) that did not initiate O2- generation, two metabolic activities were noted: (1) approximately a threefold increase in the baseline intracellular calcium (Ca++i) level, that was not dependent on extracellular Ca++, and (2) a rapid rise in intracellular pH that was blocked by 5-(N,N- dimethyl) amiloride (DA), that had no effect on the Ca++i response to priming. Furthermore, there were no significant increases in inositol metabolites in cells primed and stimulated with FMLP compared with cells receiving the stimulating dose of FMLP alone and pretreatment with pertussis toxin (PT) (before the addition of the priming -5 x 10(- 9) mol/L dose of FMLP), whereas abolishing the response to FMLP during the second stage of stimulation, had (1) no effect on FMLP-primed cells subsequently stimulated with PMA, and (2) only partially ablated the rise in Ca++i initiated with FMLP. That FMLP priming involved distinctive processes to those of the well characterized FMLP-coupled Ca++-dependent activation cascade was shown by the full priming effect attained in a Ca++-free buffer, which did not sustain an O2- response to a second-stage FMLP stimulation, but sustained a primed response to PMA. These data demonstrate that FMLP primes human neutrophils by a Ca++-independent and PT-insensitive pathway, offering a functional model for studying heterogeneous FMLP receptor-coupled reactions.  相似文献   
99.
Our aim was to determine whether histological changes occur in the cutaneous portion of pectoralis major flaps employed for upper aero-digestive tract reconstruction and, if present, to characterize these changes and try to infer their cause. Seven patients submitted to repair of aero-digestive tract defects secondary to cancer resection with pectoralis major myocutaneous flap were included in this study. All patients received adjuvant radiotherapy. Biopsies were taken from: the cutaneous portion of the flap; buccal mucosa; irradiated neck skin and chest skin opposite the donor site. Histological changes toward a “mucosalization” occur in the cutaneous portion of the pectoralis major flaps, characterized by disappearance of the horny layer or a reduction of its thickness and a decrease of the amount of cutaneous appendages. These changes are probably a result of continuous exposure to the intraoral environment in association with radiotherapy effects and may represent an advantageous adaptation for the patient.  相似文献   
100.
Kirkpatrick  JB; Hayman  LA 《Radiology》1987,162(2):509-511
Patchy white-matter lesions occur in the magnetic resonance (MR) imaging brain studies of 20%-30% of neurologically healthy elderly subjects. To determine the frequency of histologically verifiable white-matter lesions at autopsy in such subjects the authors examined serial, microscopic, whole brain sections from 15 clinically healthy subjects aged 52-72 years. Small white-matter lesions were found in 12. In these 12, zones of atrophic perivascular demyelination were present in eight brains. These are not the familiar thrombotic, embolic, or ischemic vascular lesions that produce acute necrosis. This mild vascular insufficiency produces atrophy, which has been recognized in the pathology literature but whose clinical significance remains unknown. Other lesions seen were small vascular malformations in the centrum ovale in four brains, diverticula of the lateral ventricle extending into the white matter in three, and an isolated central white-matter infarction in one. All of these lesions are probably the basis of the patchy white-matter lesions seen on MR imaging studies in the neurologically healthy elderly population.  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