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   1022篇
  免费   1篇
电工技术   2篇
化学工业   17篇
金属工艺   8篇
机械仪表   6篇
建筑科学   1篇
能源动力   1篇
轻工业   1篇
水利工程   1篇
石油天然气   11篇
无线电   4篇
一般工业技术   62篇
冶金工业   898篇
原子能技术   9篇
自动化技术   2篇
  2021年   3篇
  2019年   2篇
  2018年   5篇
  2017年   7篇
  2016年   3篇
  2014年   3篇
  2013年   7篇
  2012年   3篇
  2011年   9篇
  2010年   6篇
  2009年   12篇
  2008年   8篇
  2007年   4篇
  2006年   9篇
  2005年   4篇
  2004年   5篇
  2003年   3篇
  2002年   5篇
  2001年   6篇
  2000年   3篇
  1999年   9篇
  1998年   272篇
  1997年   144篇
  1996年   112篇
  1995年   71篇
  1994年   48篇
  1993年   58篇
  1992年   12篇
  1991年   22篇
  1990年   18篇
  1989年   7篇
  1988年   5篇
  1987年   7篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1982年   8篇
  1981年   6篇
  1980年   9篇
  1978年   4篇
  1977年   25篇
  1976年   40篇
  1975年   3篇
  1974年   2篇
  1972年   3篇
  1971年   5篇
  1970年   3篇
  1968年   3篇
  1967年   2篇
  1964年   2篇
排序方式: 共有1023条查询结果,搜索用时 15 毫秒
111.
We investigated the hypothesis that different prefrontal brain systems (i.e., dorsal vs. ventral) and sex contribute differentially to cognitive deficit in schizophrenia. Performance was assessed among clinically stable, chronic schizophrenic outpatients and matched normal control subjects on olfactory identification [on the University of Pennsylvania Smell Identification Test (UPSIT)] and on executive functions [using the Wisconsin Card Sorting Test (WCST)]. Patients were impaired on both tests compared to controls, and male schizophrenics were impaired on the WCST compared to female schizophrenics. The pattern of results suggests that gender differences on the UPSIT are mildly accentuated in schizophrenia. The data support our previous study indicating that UPSIT performance is largely independent of the executive or attentional deficits typically associated with schizophrenia, with the exception of verbal ability. Further research with larger samples is required to test the hypothesis that there is a severely impaired subgroup of male patients with diffuse prefrontal dysfunctions.  相似文献   
112.
The clinical learning environment (CLE) is an interactive network of forces influencing student learning outcomes in the clinical setting. This study used mixed methods to identify factors characterizing students' perceptions of the CLE. The sample consisted of 229 undergraduate students in the second or third year of their biophysical nursing strand. The five subscales of the Clinical Learning Environment Scale, 'staff-student relationships', 'nurse manager commitment', 'patient relationships', 'student satisfaction' and 'hierarchy and ritual', were supported by qualitative data obtained from student interviews. Interpersonal relationships between the participants in the CLE were crucial to the development of a positive learning environment. Student satisfaction with the CLE was both a result of, and influential in creating, a positive learning environment. Nurse educators, clinical venues, and all others participating in the undergraduate nursing students' clinical education, must collaborate in order to create a CLE which promotes the development of well-educated registered nurses capable of providing safe, cost-effective patient care.  相似文献   
113.
The paper is based on the analysis of 235 young and middle-age patients with non-traumatic cerebral hemorrhage. Tactics of treatment is determined for each group depending on bleeding localization in accordance with World Health Organization's classification (1981). Operative treatment is recommended for lateral site of hematomas of 25 cm3 and more signs of media structures dislocation of 5 mm and more. With the development of hypertension-hydrocephal syndrome surgical intervention is directed at its elimination and where possible at hematoma's ablation. The amount of operative interventions is limited in case of medial and mixed variants of hemorrhages especially when bleedings affect mesencephal structures. In conditions of a neurosurgical clinic a pharmacotherapy is used as an independent one, as a preparation for surgical treatment as well as during operation and in postoperative period.  相似文献   
114.
We propose the experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional accelerator and with laser wake field accelerated electrons for studying extreme field limits in the nonlinear interaction of electromagnetic waves. The regimes of dominant radiation reaction, which completely changes the electromagnetic wave-matter interaction, will be revealed in the laser plasma experiments. This will result in a new powerful source of ultra short high brightness gamma-ray pulses. A possibility of the demonstration of the electron-positron pair creation in vacuum in a multi-photon processes can be realized. This will allow modeling under terrestrial laboratory conditions neutron star magnetospheres, cosmological gamma ray bursts and the Leptonic Era of the Universe.  相似文献   
115.
76Ge-enriched germane has been ultrapurified by low-temperature distillation. The nature and concentration of molecular impurities in the germane samples were determined by gas chromatography/mass spectrometry, high-resolution Fourier transform IR spectroscopy, and gas chromatography. The distillate contains no more than 10−5 mol % hydrocarbons, 10−4 mol % carbon dioxide, 10−3 to 10−1 mol % digermane and trigermane, and <3 × 10−5 mol % other impurities. A distinctive feature of the impurity composition of the isotopically enriched germane samples is the presence of silicon tetrafluoride and sulfur hexafluoride impurities.  相似文献   
116.
Human Error Identification (HEI) techniques have been used to predict human error in high risk environments for the past two decades. Despite the lack of supportive evidence for their efficacy, their popularity remains unabated. The application of these approaches is ever-increasing, to include product assessment. The authors feel that it is necessary to prove that the predictions are both reliable and valid before the approaches can be recommended with any confidence. This paper provides evidence to suggest that human error identification techniques in general, and SHERPA in particular, may be acquired with relative ease and can provide reasonable error predictions.  相似文献   
117.
118.
Transient periodic increases in the extracellular K+ concentration (20 mM, 30 sec, 3-6 episodes) led to the appearance of a kindling-like state in local neuronal networks of field CA1 of rat hippocampal slices. A criterion for the appearance of this state was a reduction in the threshold for the generation of multiple population discharges and an increase in the total number of population spikes within discharges (epileptiform activity). This state correlated with potentiation of excitatory postsynaptic potentials (EPSP) (long-term increases in pyramidal neuron excitability), but not with potentiation of glutamatergic synaptic transmission in field CA1 of hippocampal slices. The role of the various Ca2+ channels in inducing and maintaining the kindling-like state in rat hippocampal sections, evoked by periodic increases in the extracellular K+ concentration, is discussed.  相似文献   
119.
Cold exposure increases TRH gene expression in hypothalamic and raphe nuclei and results in a vagal activation of gastric function. We investigated the role of medullary TRH receptors in cold (4-6 C, 90 min)-induced stimulation of gastric motor function in fasted conscious rats using intracisternal injections of TRH receptor (TRHr) antisense oligodeoxynucleotides (100 microg twice, -48 and -24 h). The gastric emptying of a methyl-cellulose solution was assessed by the phenol red method. TRH (0.1 microg) or the somatostatin subtype 5-preferring analog, BIM-23052 (1 microg), injected intracisternally increased basal gastric emptying by 34% and 47%, respectively. TRHr antisense, which had no effect on basal emptying, blocked TRH action but did not influence that of BIM-23052. Cold exposure increased gastric emptying by 64%, and the response was inhibited by vagotomy, atropine (0.1 mg/kg, i.p.), and TRHr antisense (intracisternally). Saline or mismatched oligodeoxynucleotides, injected intracisternally under similar conditions, did not alter the enhanced gastric emptying induced by cold or intracisternal injection of TRH or BIM-23052. These results indicate that TRH receptor activation in the brain stem mediates acute cold-induced vagal cholinergic stimulation of gastric transit, and that medullary TRH may play a role in the autonomic visceral responses to acute cold.  相似文献   
120.
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