全文获取类型
收费全文 | 4157篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 36篇 |
金属工艺 | 2篇 |
机械仪表 | 3篇 |
建筑科学 | 4篇 |
轻工业 | 22篇 |
无线电 | 7篇 |
一般工业技术 | 14篇 |
冶金工业 | 4066篇 |
自动化技术 | 11篇 |
出版年
2022年 | 2篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 130篇 |
1998年 | 1369篇 |
1997年 | 763篇 |
1996年 | 457篇 |
1995年 | 272篇 |
1994年 | 230篇 |
1993年 | 236篇 |
1992年 | 29篇 |
1991年 | 54篇 |
1990年 | 39篇 |
1989年 | 37篇 |
1988年 | 48篇 |
1987年 | 45篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 1篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 21篇 |
1980年 | 31篇 |
1978年 | 8篇 |
1977年 | 81篇 |
1976年 | 134篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1959年 | 1篇 |
1955年 | 1篇 |
1931年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有4166条查询结果,搜索用时 15 毫秒
31.
SM Vul'' 《Canadian Metallurgical Quarterly》1977,26(4):67-70
One of the pathways of improving the psychological selection of the flying personnel is to study properties of the personality responsible for flying tasks. It is important to form an ideal of personality properties of the pilot and navigator. With this purpose a special set of psychological methods allowing a comprehensive study of the personality was used. The results helped to identify personality properties typical of pilots and navigators and to suggest that high achievements in the professional activity of pilots and navigators are associated with their personality characteristics and correct selection of the flying specialty. 相似文献
32.
33.
Rat dams, given intravenous injections of heat-killed Streptococcus mutans 6715, mutant C211 demonstrated significant agglutinin activity to the homologous S. mutans in colostrum, milk, and serum. This antibody activity was associated with the immunoglobulin G (IgG) class. High titers of anti-S. mutans antibody associated with the IgG class were also exhibited in the sera and saliva of the offspring that suckled these dams. After challenge with the homologous, live S. mutans, these offspring developed significantly fewer caries on all molar surfaces than did nonimmunized infected controls. A secretory immune response (manifested by the presence of specific IgA antibody to S. mutans in colostrum and milk) was elicited (i) in rat dams locally injected, in the region of the mammary gland, with heat-killed S. mutans antigen, and (ii) in other rat dams that were provided formalin-killed S. mutans in their drinking water. Offspring suckling these dams were challenged with virulent S. mutans before weaning and developed significantly fewer caries than did their infected controls. These findings clearly suggest that passively derived IgG or IgA antibodies to S. mutans are protective against dental caries. 相似文献
34.
35.
36.
Hypertension and tachycardia are well known features of acute porphyria and have been shown to be related to increased circulating catecholamines. The mechanism by which circulating catecholamines are increased was studied using the isolated perfused rat heart and human platelets as a model of adrenergic neuronal function. It was found that neither delta-aminolevulinate (ALA) nor porphobilinogen (PBG) blocked uptake or caused release in the isolated perfused rat heart. Platelets from six patients with acute prophyria, three in remission and three latent, with matching normal controls were studied with regard to their uptake of [(3)H]norepinephrine in the presence of ALA or PBG. It was found that ALA and PBG significantly reduced uptake and accumulation of [(3)H]-norepinephrine in patients with acute porphyria; however, no similar reduction in uptake and accumulation was observed in the platelets of normal controls. Therefore, it appears that there is a latent defect in the catecholamine uptake and (or) accumulation of platelets of patients with acute prophyria which only manifests itself in the presence of ALA or PBG. If platelet uptake serves as a model of adrenergic neuron uptake, this suggests that elevated circulating catecholamine levels during acute attacks of acute porphyria are caused at least partially by blockade of re-uptake into the sympathetic neurons. 相似文献
37.
38.
SS Grigorian OG Baklavadzhian SM Minasian TsI Adamian ES Gevorkian SG Sarkisian 《Canadian Metallurgical Quarterly》1997,83(11-12):49-56
Effects of single, double, and rhythmic stimulation upon hypothalamic neurons responding to the 1st excitatory phase of lateral vestibular nucleus stimulation, were studied. The data obtained show that activation of some hypothalamic neurons following stimulation of the lateral vestibular nucleus has a monosynaptic character. The findings suggest that ascending afferents from the lateral vestibular nucleus to the hypothalamus pass via oligo- as well as polysynaptic pathways. 相似文献
39.
S Corbalan-Garcia SM Margarit D Galron SS Yang D Bar-Sagi 《Canadian Metallurgical Quarterly》1998,18(2):880-886
The guanine nucleotide exchange factor Sos mediates the coupling of receptor tyrosine kinases to Ras activation. To investigate the mechanisms that control Sos activity, we have analyzed the contribution of various domains to its catalytic activity. Using human Sos1 (hSos1) truncation mutants, we show that Sos proteins lacking either the amino or the carboxyl terminus domain, or both, display a guanine nucleotide exchange activity that is significantly higher compared with that of the full-length protein. These results demonstrate that both the amino and the carboxyl terminus domains of Sos are involved in the negative regulation of its catalytic activity. Furthermore, in vitro Ras binding experiments suggest that the amino and carboxyl terminus domains exert negative allosteric control on the interaction of the Sos catalytic domain with Ras. The guanine nucleotide exchange activity of hSos1 was not augmented by growth factor stimulation, indicating that Sos activity is constitutively maintained in a downregulated state. Deletion of both the amino and the carboxyl terminus domains was sufficient to activate the transforming potential of Sos. These findings suggest a novel negative regulatory role for the amino terminus domain of Sos and indicate a cooperation between the amino and the carboxyl terminus domains in the regulation of Sos activity. 相似文献
40.