全文获取类型
收费全文 | 3293篇 |
免费 | 38篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 152篇 |
金属工艺 | 9篇 |
机械仪表 | 16篇 |
建筑科学 | 28篇 |
能源动力 | 20篇 |
轻工业 | 57篇 |
水利工程 | 8篇 |
石油天然气 | 15篇 |
无线电 | 121篇 |
一般工业技术 | 208篇 |
冶金工业 | 2573篇 |
原子能技术 | 46篇 |
自动化技术 | 66篇 |
出版年
2021年 | 12篇 |
2019年 | 13篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 20篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 45篇 |
2012年 | 34篇 |
2011年 | 31篇 |
2010年 | 37篇 |
2009年 | 24篇 |
2008年 | 33篇 |
2007年 | 27篇 |
2006年 | 31篇 |
2005年 | 24篇 |
2004年 | 18篇 |
2003年 | 25篇 |
2002年 | 27篇 |
2001年 | 15篇 |
2000年 | 25篇 |
1999年 | 90篇 |
1998年 | 710篇 |
1997年 | 454篇 |
1996年 | 306篇 |
1995年 | 165篇 |
1994年 | 142篇 |
1993年 | 160篇 |
1992年 | 20篇 |
1991年 | 36篇 |
1990年 | 36篇 |
1989年 | 35篇 |
1988年 | 39篇 |
1987年 | 39篇 |
1986年 | 39篇 |
1985年 | 30篇 |
1984年 | 13篇 |
1983年 | 19篇 |
1982年 | 23篇 |
1981年 | 26篇 |
1980年 | 22篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1977年 | 94篇 |
1976年 | 168篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1972年 | 14篇 |
1971年 | 7篇 |
1970年 | 11篇 |
排序方式: 共有3331条查询结果,搜索用时 0 毫秒
151.
152.
AE Kammer 《Canadian Metallurgical Quarterly》1976,35(9):1992-1999
In insects gas exchange may be: 1) entirely passive, when metabolic rate is low; 2) enhanced automatically by muscle contractions that produce movements, e.g., wing movements in flight; or 3) produced by ventilatory movements, particularly of the abdomen. In terrestrial insects such as locusts and cockroaches ventilatory movements are governed by a dominant oscillator in the metathoracic or anterior abdominal ganglion. The dominant oscillator overrides local oscillators in the abdominal ganglia and thus sets the rhythm for the entire abdomen, and it also controls spiracle opening and closing in several thoracic and abdominal segments. This ventilatory control mechanism appears to be different from that generating metachronal rhythms such as occur in the ventilatory and locomotory movements of aquatic arthropods. There are now several examples of rhythms, both ventilatory and locomotory, that can be generated by the central nervous system in the absence of phasic sensory feedback, but the mechanism of rhythm production is not known. Studies of ganglionic output suggest that neuronal oscillators can produce a range of frequencies and that some oscillators may be employed in more than one function or behavior. The mechanisms by which central oscillators are coupled to the output motorneurons are also not known; large phase changes suggest that in some cases different coupling interneurons are active. Intracellular recordings from identified neurons have begun to clarify the important roles of interneurons in the production of motor patterns. 相似文献
153.
154.
D. T. Stuss; E. F. Kaplan; D. F. Benson; W. S. Weir; Steven Chiulli; F. F. Sarazin 《Canadian Metallurgical Quarterly》1982,96(6):913
Although it is frequently stated that the frontal lobes play a significant role in memory function, research proof has been ambiguous at best. The present study investigated this problem by administering a variety of memory tests (e.g., Wechsler Memory Scale, WAIS) to 16 schizophrenic patients who had undergone prefrontal leukotomy approximately 25 yrs earlier. Ss were divided into 3 groups on the basis of recovery after surgery. Two comparison groups (5 psychiatric and 5 normal controls) were established to control for psychiatric symptomatology, years of institutionalization, age, and years of education. Results indicate that large bilateral orbitofrontal lesions may not result in amnesia; in fact, the nonoperated schizophrenic control group performed the most poorly. Proactive interference was demonstrated, however, resulting in significant impairment for all Ss with prefrontal lobe damage despite normal scores on commonly used memory tests. Ability to maintain consistent and directed attention and to overcome interference is proposed as a role of the frontal lobes in memory function. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
155.
156.
157.
158.
159.
Phasic changes in cardiac reactivity to innocuous stimuli, presented in a sensory disparity paradigm, were used to evaluate habituation and learning processes in five decerebrate subjects. Three subjects showed systematic changes over trials in the pattern of cardiac response to simple auditory or visual stimuli, indicative of habituation. In addition, tests for associative learning were given after repeated presentations of two paired stimuli. The appearance of a marked cardiac orienting response, to the unpredictable omission of the second stimulus, documented the development of a conditioned association in these same three subjects. One additional subject failed to show a consistent pattern of response to the stimuli, and another demonstrated a consistent response which was not subject to habituation. Overall, these findings support the view that learning processes are not solely the product of the cerebral hemispheres, but reflect general integrative features of the human neuraxis. 相似文献
160.
A 4-month-old infant with congenital glaucoma had been treated with a topical antibiotic-corticosteroid for three months. This fact complicated initial management, delaying definitive diagnosis and therapy. Topical steroid therapy in infants can produce a condition simulating congenital glaucoma. Since there is little rationale for using topical steroids to treat most infantile external disease processes, they are best avoided. When steroids are used for a prolonged period, some strategy for detecting glaucoma should be adopted. 相似文献