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   2059篇
  免费   7篇
电工技术   13篇
综合类   2篇
化学工业   62篇
金属工艺   30篇
机械仪表   9篇
建筑科学   53篇
能源动力   11篇
轻工业   65篇
水利工程   7篇
无线电   32篇
一般工业技术   93篇
冶金工业   1634篇
原子能技术   11篇
自动化技术   44篇
  2022年   6篇
  2021年   4篇
  2019年   9篇
  2018年   8篇
  2017年   8篇
  2016年   4篇
  2014年   12篇
  2013年   30篇
  2012年   20篇
  2011年   24篇
  2010年   13篇
  2009年   10篇
  2008年   20篇
  2007年   18篇
  2006年   16篇
  2005年   10篇
  2004年   19篇
  2003年   13篇
  2002年   13篇
  2001年   6篇
  2000年   10篇
  1999年   61篇
  1998年   531篇
  1997年   295篇
  1996年   173篇
  1995年   114篇
  1994年   98篇
  1993年   102篇
  1992年   25篇
  1991年   19篇
  1990年   24篇
  1989年   17篇
  1988年   18篇
  1987年   25篇
  1986年   19篇
  1985年   25篇
  1984年   3篇
  1983年   9篇
  1982年   6篇
  1981年   13篇
  1980年   23篇
  1979年   3篇
  1978年   11篇
  1977年   48篇
  1976年   90篇
  1975年   4篇
  1973年   4篇
  1971年   4篇
  1967年   3篇
  1919年   2篇
排序方式: 共有2066条查询结果,搜索用时 15 毫秒
101.
This paper reports two cases of orbital apex syndrome. The most salient clinical signs, ophthalmoplegia and eyelid ptosis, arose from perineural spread of facial squamous cell carcinomas that were previously excised with tumour-free surgical margins and exhibited no signs of local or other regional recurrence. The interest of these two cases lies in the fairly rare occurrence of this type of tumour spread and the highly aggressive nature of the tumour, unequivocal diagnosis of which usually arrives too late for a surgical solution. Awareness of the possibility of such perineural spread may allow the clinician to establish an early diagnosis and thus undertake radical surgery, thereby increasing the likelihood of success in combination with postoperative radiotherapy.  相似文献   
102.
103.
We have developed an on-line archive of neuronal geometry to encourage the use of realistic dendritic structures in morphometry and for neuronal modeling, located at web address www.neuro.soton.ac.uk. Initially we have included full three-dimensional representations of 87 neurons from the hippocampus, obtained following intracellular staining with biocytin and reconstruction using Neurolucida. The archive system includes a structure editor for correcting any departures from valid branching geometry and which allows simple errors in the digitisation to be corrected. The editor employs a platform-independent file format which enforces the constraints that there should be no isolated branches and no closed loops. It also incorporates software for interconversion between the archive format and those used by various neuronal reconstruction and modelling packages. The raw data from digitisation software can be included in the archive as well as edited reconstructions and any further information available. Cross-referenced tables and indexes are updated automatically and are sorted according to a number of fields including the cell type, contributor, submission date and published reference. Both the archive and the structure editor should facilitate the quantitative use of full three-dimensional reconstructions of neurons from the hippocampus and other brain regions.  相似文献   
104.
This review highlights the most interesting features of null cell adenomas and oncocytomas of the pituitary gland. Recently, application of sensitive methods have documented a very low amount of active hormone production in these clinically nonfunctioning tumours. However, further studies are needed to clarify the histogenesis of null cell adenomas and oncocytomas.  相似文献   
105.
BACKGROUND: The authors' objective was to provide data regarding the demographic, phenomenological, course of illness, associated psychiatric and medical comorbidity, family history, and psychiatric treatment response characteristics of rigorously diagnosed subjects who met DSM-IV criteria for intermittent explosive disorder. METHOD: Twenty-seven subjects meeting DSM-IV criteria for a current or past history of intermittent explosive disorder were given structured diagnostic interviews. The subjects' medical histories, family histories of psychiatric disorders, and responses to psychiatric treatments were also assessed. RESULTS: Most subjects described their intermittent explosive disorder symptoms as very distressing and/or highly problematic. All 27 subjects described aggressive impulses prior to their aggressive acts. Of 24 subjects who were systematically queried, 21 (88%) experienced tension with the impulses; 18 (75%), relief with the aggressive acts; and 11 (48%), pleasure with the acts. Most subjects stated that their aggressive impulses and acts were also associated with affective symptoms, particularly changes in mood and energy level. Twenty-five (93%) subjects had lifetime DSM-IV diagnoses of mood disorders; 13 (48%), substance use disorders; 13 (48%), anxiety disorders; 6 (22%), eating disorders; and 12 (44%), an impulse-control disorder other than intermittent explosive disorder. Subjects also displayed high rates of comorbid migraine headaches. First-degree relatives displayed high rates of mood, substance use, and impulse-control disorders. Twelve (60%) of 20 subjects receiving monotherapy with an antidepressant or a mood stabilizer reported moderate or marked reduction of their aggressive impulses and/or episodes. CONCLUSION: Intermittent explosive disorder appears to be a bona fide impulse-control disorder that may be related to mood disorder and may represent another form of affective spectrum disorder.  相似文献   
106.
We have provided evidence that the stimulatory effects of intravenous interleukin-1 (IL-1) on neurosecretory neurons in the paraventricular nucleus (PVH) that express corticotropin-releasing factor (CRF) depend specifically on the integrity of catecholaminergic projections originating in caudal medulla. Here we report on experiments designed to test alternative means by which circulating IL-1 might access medullary aminergic neurons, including mechanisms involving sensory components of the vagus, the area postrema, or perivascular cells bearing IL-1 receptors. Neither abdominal vagotomy nor area postrema lesions reliably altered Fos expression induced in the medulla or PVH in response to a moderately suprathreshold dose of IL-1beta. Cytokine-stimulated increases in CRF mRNA in the PVH were also unaffected by either ablation. By contrast, systemic administration of the cyclooxygenase inhibitor indomethacin resulted in parallel dose-related attenuations of IL-1 effects in hypothalamus and medulla. Microinjections of prostaglandin E2 (PGE2; >/=10 ng) in rostral ventrolateral medulla, the principal seat of IL-1-sensitive neurons that project to the PVH, provoked discrete patterns of cellular activation in hypothalamus and medulla that mimicked those seen in response to intravenous IL-1. We interpret these findings as supporting the hypothesis that paracrine effects of PGE2 released from perivascular cells in the medulla as a consequence of IL-1 stimulation and, acting through prostanoid receptors on or near local aminergic neurons that project to the PVH, contribute to the stimulatory effects of increased circulating IL-1 on neurons constituting the central limb of the hypothalamo-pituitary-adrenal axis.  相似文献   
107.
108.
MANOVA and repeated measures ANOVA approaches have provided evidence of a number of limitations in several event-related potential (ERP) studies due to violations of their statistical assumptions and the typically moderate size of the available sample. Alternative, computer-intensive methods based on permutation principles have recently been developed. Up to now this methodology has focused mostly on magnitude differences between scalp distributions as measured by t statistics. In this paper the scope of permutation techniques in ERP analysis was widened. A new statistic (D statistic) is introduced to compare the shapes of scalp distributions of ERPs. Additionally a general non-parametric combinatory technique is introduced to evaluate, by means of multivariate permutation tests, several time points and/or recording sites in ERP data. The methodology described here was used to test if two ERP components elicited during word-pair matching tasks to semantic or phonological incongruences had different scalp distributions.  相似文献   
109.
110.
Concern for outside review of medical research involving human subjects has been documented as far back as the early Nineteenth Century. It was not until 1966, however, when applicants for Public Health Service grant funding were subjected to such a requirement, that researchers were required to undergo review. Institutional Review Boards (IRB) are the bodies charged with performing the mandated screening functions by the Department of Health and Human Services (HHS) for federally funded projects and by the Food and Drug Administration (FDA) in the drug and device approval process.

This paper explores an IRB's responsibilities under the HHS and FDA regulations generally, and emphasizes several critical attendant issues including: the manufacturer's IRB; IRB members' individual liability; compensation for research injuries; civil rights protections afforded subjects; impact upon academic and health practitioner research; and effect upon drug and device approvals.  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