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   11160篇
  免费   558篇
  国内免费   23篇
耳鼻咽喉   80篇
儿科学   306篇
妇产科学   283篇
基础医学   1826篇
口腔科学   211篇
临床医学   1002篇
内科学   1849篇
皮肤病学   169篇
神经病学   1841篇
特种医学   472篇
外科学   1266篇
综合类   88篇
一般理论   3篇
预防医学   890篇
眼科学   131篇
药学   690篇
中国医学   29篇
肿瘤学   605篇
  2022年   65篇
  2021年   143篇
  2020年   94篇
  2019年   128篇
  2018年   158篇
  2017年   121篇
  2016年   160篇
  2015年   209篇
  2014年   269篇
  2013年   384篇
  2012年   659篇
  2011年   707篇
  2010年   419篇
  2009年   456篇
  2008年   609篇
  2007年   687篇
  2006年   659篇
  2005年   669篇
  2004年   627篇
  2003年   556篇
  2002年   581篇
  2001年   139篇
  2000年   88篇
  1999年   122篇
  1998年   141篇
  1997年   99篇
  1996年   93篇
  1995年   92篇
  1994年   71篇
  1993年   64篇
  1992年   50篇
  1991年   67篇
  1990年   55篇
  1989年   57篇
  1988年   46篇
  1985年   50篇
  1984年   53篇
  1982年   48篇
  1977年   46篇
  1974年   51篇
  1933年   71篇
  1932年   59篇
  1931年   57篇
  1930年   52篇
  1929年   44篇
  1928年   45篇
  1927年   52篇
  1926年   54篇
  1925年   49篇
  1924年   52篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
Positron emission tomography (PET) using radiolabeled amino acids has shown great potential for more accurate diagnostics of cerebral gliomas. O-(2-[18F]Fluoroethyl)-L-tyrosine (FET) is a new tracer for PET which can be produced with high efficiency and distributed on a wide clinical scale in Germany. In a biopsy-controlled study, a significant improvement of the detection of true tumor extent of cerebral gliomas could be demonstrated by the combined use of FET PET and MRT in comparison with MRT alone. Advantages of FET PET are an improved guidance of biopsies, an improved planning of surgery and radiation therapy, and the differentiation of tumor recurrence from unspecific post-therapeutic tissue changes. Furthermore, FET PET appears to be particularly valuable in the prognosis of low-grade gliomas.  相似文献   
995.
Objective Although alpha-blockers are effective in lowering blood pressure, they may increase heart rate, an unwanted effect that could negatively affect outcome. However, the alpha-blocker urapidil might not increase heart rate due to its additional effect on 5-HT1A receptors. Therefore, we compared the effects of urapidil on heart rate with those of another alpha-blocker, doxazosin. Methods We performed a randomised, double-blind, placebo-controlled, cross-over study in 12 healthy males who received single oral doses of 60 mg urapidil, 4 mg doxazosin and placebo. Four hours following drug intake, heart rate and blood pressure were measured at rest and during exercise. Results Both doxazosin and urapidil decreased blood pressure to the same extent. Compared to placebo, resting heart rate was significantly increased by doxazosin (+25%, P < 0.05) but not by urapidil (+12%, n.s.). Resting heart rate with doxazosin was significantly higher than with urapidil (P < 0.05). Similarly, the rate pressure product (RPP) at rest was increased by doxazosin (+17%, P < 0.05) but not by urapidil (+6%, n.s.). Conclusions We conclude that the increase in heart rate caused by urapidil is less pronounced than that with doxazosin, a property that might favour urapidil in the treatment of arterial hypertension. In addition, only doxazosin (but not urapidil) increased the RPP at rest, a finding that might be helpful to explain why this drug was never shown to improve outcome in the treatment of arterial hypertension.  相似文献   
996.
Neurologists have been analyzing the clinical behaviors that occur during seizures for many years. Several ictal behaviors have been defined in temporal lobe epilepsy (TLE). Ictal behaviors are especially important in the evaluation of epilepsy surgery candidates. We propose a new lateralizing sign in TLE originating from the nondominant hemisphere-the "hush" sign. Our patients were 30- and 21-year old women (Cases 1 and 2, respectively). Their epileptogenic foci were localized to the right mesial temporal region after noninvasive presurgical investigations. Case 1 had no cranial MRI abnormality, whereas cranial MRI revealed right hippocampal atrophy in Case 2. These women repeatedly moved their right index fingers to their mouth while puckering their lips during complex partial seizures. We have named this ictal behavior the "hush" sign. Anterior temporal lobectomy with amygdalohippocampectomy was performed in both patients, and pathological examinations revealed hippocampal sclerosis. The "hush" sign no longer occurred after seizures were controlled. They were seizure free as of 30 and 31 months of follow-up, respectively. We believe that the "hush" sign may be supportive of a diagnosis of TLE originating from the nondominant hemisphere. This sign may occur as a result of ictal activation of a specific brain region in this hemisphere.  相似文献   
997.
OBJECTIVES: To demonstrate a clear-cut M response recorded from the severely affected thigh muscles to the stimulation of the upper limb nerves in a serial of patients with late poliomyelitis. METHODS: Fifteen patients with late poliomyelitis, 7 patients with spinal cord disorders and 11 control subjects were included. Evoked muscle responses were investigated in quadriceps femoris and/or thigh adductor muscles to the stimulation of the brachial plexus, median and ulnar nerves. RESULTS: Evoked muscle responses were obtained from the thigh muscles in all 12 late polio patients with proximal lower extremity involvement. The response could not be recorded from the thigh muscles neither in the 3 polio patients with upper extremity involvement nor in the healthy control subjects and in patients with other spinal cord disorders of anterior horn cell. CONCLUSIONS: It is proposed that the electrical stimulation of the arm nerves produce interlimb descending muscle responses in the severely affected atrophic thigh muscles of the patients with late polio. This finding suggests that there might be a focal and/or specific loss of inhibitory interneurons between injured and normal motor neurons and increased facilitatory synaptic action at the end of long propriospinal descending fibers in the case of late poliomyelitis.  相似文献   
998.
The authors report the case of a 70-year-old woman who developed a Brown–Sequard-syndrome within 6 weeks caused by an intramedullary spinal cord metastasis of an occult renal cell carcinoma. Intramedullary metastases are rare and represent only 4–8.5% of central nervous system metastases. An important feature of intramedullary metastases is the rapid progression of neurological deficits which necessitates rapid treatment. There are only eight earlier reports of intramedullary metastasis due to renal cell carcinoma (Schiff D, O'Neill BP. Intramedullary spinal cord metastases: clinical features and treatment outcome. Neurology 1996;47:906–12; Belz P. Ein Fall von intramedullaerer Grawitz-Metastase im Lumbalmark. Frankfurt Z Pathol 1912;10:431–44; Gaylor JB, Howie JW. Brown–Sequard-syndrome. A case of unusual aetiology. J Neurol Neurosurg Psychiatry 1938;1:301–5; Kawakami Y, Mair WGP. Haematomyelia due to secondary renal carcinoma. Acta Neuro Pathol 1973;26:85–92; Strang RR. Metastatic tumor of the cervical spinal cord. Med J Aust 1962;1:205–6; Von Pfungen. Über einige Fälle von Haematomyelie nichttraumatischen Ursprungs. Wien Klin Rdsch 1906;20:44–50; Weitzner S. Coexistent intramedullary metastasis and syringomyelia of cervical spinal cord. Report of a case. Neurology 1960;674–8). To the best of our knowledge this is the first report on a patient in whom symptoms from the metastasis of a renal cell carcinoma preceded the detection of the primary tumor. This report presents the clinical, neuroradiological and histopathological findings of an intramedullary metastasis of a renal cell carcinoma and provides an overview of the literature on intramedullary spinal cord metastases.  相似文献   
999.
Antenatal maternal long-term hypoxia (LTH) can alter serotonin (5-HT) and calcium (Ca(2+)) signaling in fetal pulmonary arteries (PAs) and is associated with persistent pulmonary hypertension of the newborn (PPHN). In humans, the antenatal maternal hypoxia can be secondary to smoking, anemia, and chronic obstructive pulmonary disorders. However, the mechanisms of antenatal maternal hypoxia-related PPHN are unresolved. Because both LTH and 5-HT are associated with PPHN, we tested the hypothesis that antenatal maternal LTH can increase 5-HT-mediated PA contraction and associated extracellular Ca(2+) influx through L-type Ca(2+) channels (Ca(L)), nonselective cation channels (NSCCs), and reverse-mode sodium-calcium exchanger (NCX) in the near-term fetus. We performed wire myography and confocal-Ca(2+) imaging approaches on fetal lamb PA (~ 140 days of gestation) from normoxic ewes or those acclimatized to high-altitude LTH (3801 m) for ~110 days. Long-term hypoxia reduced the potency but not the efficacy of 5-HT-induced PA contraction. Ketanserin (100 nmol/L), a 5-HT(2A) antagonist, shifted 5-HT potency irrespective of LTH, while GR-55562 (1 μmol/L), a 5-HT(1B/D) inhibitor, antagonized 5-HT-induced contraction in normoxic fetuses only. Various inhibitors for Ca(L), NSCC, and reverse-mode NCX were used in contraction studies. Contraction was reliant on extracellular Ca(2+) regardless of maternal hypoxia, NSCC was more important to contraction than Ca(L), and reverse-mode NCX had little or no role in contraction. Long-term hypoxia also attenuated the effects of 2-APB and flufenamic acid and reduced Ca(2+) responses observed by imaging studies. Overall, LTH reduced 5HT(1B/D) function and increased NSCC-related Ca(2+)-dependent contraction in ovine fetuses, which may compromise pulmonary vascular function in the newborn.  相似文献   
1000.
Triclocarban (TCC; 3,4,4'-trichlorocarbanilide) is an antimicrobial agent used widely in various personal hygiene products including soaps. Recently, TCC has been shown to enhance testosterone-induced effects in vitro and to enlarge accessory sex organs in castrated male rats. This study was designed to evaluate the effects of TCC on intact age-matched male rats and on human prostate LNCaP and C4-2B cells. Seven-week-old male Sprague-Dawley rats received either a normal diet or a diet supplemented with TCC (0.25% in diet) for 10 days. Triclocarban induced hyperplasia of accessory sex organs in the absence of significant qualitative histological changes. Serum luteinizing hormone (LH) and testosterone were not significantly altered by TCC treatment. In prostate cancer-derived LNCaP and C4-2B cells, TCC potentiated androgen actions via androgen receptor-dependent actions. In conclusion, TCC significantly affects intact male reproductive organs and potentiates androgen effects in prostate cancer cells.  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