全文获取类型
收费全文 | 3351篇 |
免费 | 39篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 120篇 |
化学工业 | 397篇 |
金属工艺 | 1570篇 |
机械仪表 | 32篇 |
建筑科学 | 16篇 |
矿业工程 | 1篇 |
能源动力 | 53篇 |
轻工业 | 88篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 256篇 |
一般工业技术 | 271篇 |
冶金工业 | 429篇 |
原子能技术 | 55篇 |
自动化技术 | 99篇 |
出版年
2023年 | 6篇 |
2022年 | 18篇 |
2021年 | 17篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 18篇 |
2017年 | 17篇 |
2016年 | 32篇 |
2015年 | 15篇 |
2014年 | 37篇 |
2013年 | 111篇 |
2012年 | 105篇 |
2011年 | 92篇 |
2010年 | 61篇 |
2009年 | 101篇 |
2008年 | 121篇 |
2007年 | 105篇 |
2006年 | 98篇 |
2005年 | 83篇 |
2004年 | 80篇 |
2003年 | 105篇 |
2002年 | 124篇 |
2001年 | 126篇 |
2000年 | 101篇 |
1999年 | 126篇 |
1998年 | 242篇 |
1997年 | 210篇 |
1996年 | 157篇 |
1995年 | 99篇 |
1994年 | 103篇 |
1993年 | 162篇 |
1992年 | 157篇 |
1991年 | 136篇 |
1990年 | 51篇 |
1989年 | 38篇 |
1988年 | 32篇 |
1987年 | 31篇 |
1986年 | 34篇 |
1985年 | 32篇 |
1984年 | 41篇 |
1983年 | 25篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1976年 | 15篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有3391条查询结果,搜索用时 31 毫秒
21.
22.
23.
24.
An intrinsic guanine nucleotide exchange inhibitor in Gi2 alpha. Significance of G-protein self-suppression which antagonizes receptor signal 总被引:1,自引:0,他引:1
T Okamoto Y Murayama SM Strittmatter T Katada S Asano E Ogata I Nishimoto 《Canadian Metallurgical Quarterly》1994,269(19):13756-13759
The alpha subunit of Gi2 (Gi2 alpha) is a member of the heterotrimeric G protein family, which transduces receptor signals as a proto-oncogene product. We have found a novel self-suppressive region in Gi2 alpha near its C terminus. A polypeptide consisting of residues 338-352 of Gi2 alpha (Gi2 alpha-339-352) antagonizes receptor- and receptor peptide-stimulated Gi2 alpha activation, without affecting basal activity. Antagonism by Gi2 alpha-338-352 is attributable to an interaction with activated Gi2 alpha, which is not competitive with receptor polypeptides. Combined with the reports suggesting the presence of self-suppressive domains in a juxta-C-terminal portion of Gi2 alpha and G(o) alpha, this study supports the hypothesis that Gi2 alpha-338-352 constitutes an intrinsic guanine nucleotide exchange inhibitor, which in turn antagonizes receptor stimulation, suggesting that G proteins are activated by receptors through relaxation of a self-suppressive conformation. 相似文献
25.
Masahiro Asari Shinichi Iwamoto Tatsuki Okamoto Hiromasu Fukagawa 《Electrical Engineering in Japan》1992,112(1):25-38
The recent increase in the demand for power in urban areas has caused changes in the way power is supplied. Underground distribution systems have been introduced for convenience in urban areas and to prevent injuries in case of a crisis. As a result, many new types of power cables are being used. One type, XPLE cables (also called CV cables) have been rapidly taking the place of conventional cables such as OF or SL cables since the 1960s because of their relatively easy installation and maintainability. However, distribution cables used under severe environmental conditions deteriorate rapidly (due mainly to water treeing), and some cables experience insulation breakdown. Therefore, many diagnostic methods have been developed, though they have not been very effective. By combining methods, a high reliability can be achieved in comparison to the use of a single method. However, processing the data is difficult for on-site personnel, so many experts are required. But there is a lack of qualified experts, hence we have turned to the development of expert systems. 相似文献
26.
T Yamatsuji T Okamoto S Takeda Y Murayama N Tanaka I Nishimoto 《Canadian Metallurgical Quarterly》1996,15(3):498-509
APP is a transmembrane precursor of beta-amyloid. In dominantly inherited familial Alzheimer's disease (FAD), point mutations V6421, V642F and V642G have been discovered in APP695. Here we show that expression of these mutants (FAD-APPs) causes a clone of COS cells to undergo apoptosis associated with DNA fragmentation. Apoptosis by the three FAD-APPs was the highest among all possible V642 mutants; normal APP695 had no effect on apoptosis, suggesting that apoptosis by APP mutants in this system is phenotypically linked to the FAD trait. FAD-APP-induced apoptosis was sensitive to bcl-2 and most probably mediated by heteromeric G proteins. This study presents a model system allowing analysis of the mechanism for FAD-APP-induced cytotoxicity. 相似文献
27.
T Yamazaki A Katsumi K Kagami Y Okamoto I Sugiura M Hamaguchi T Kojima J Takamatsu H Saito 《Canadian Metallurgical Quarterly》1996,87(11):4643-4650
The molecular basis for a hereditary type I protein S (PS) deficiency was investigated. DNA sequence analysis in the proband showed a novel missense mutation substituting Cys (TGT) for Arg474 (CGT) that is a highly conserved amino acid residue among the related proteins. This missense mutation cosegregated with the type I PS deficiency in this family. Transient expression studies showed that the secretion of the recombinant Cys-mutant PS was markedly decreased compared with that of the recombinant wild-type PS, reproducing the observed phenotype of type I deficiency. Stable expression and pulse-chase experiments demonstrated an intracellular degradation and an impaired secretion of the recombinant Cys-mutant PS. Furthermore, the substitution of Arg474 by Ala or Glu, but not by Lys, markedly reduced the secretion of the recombinant PS mutants in transient expression studies, suggesting that a positively charged basic amino acid might be needed at residue 474 and might play a key role in the protein structure and conformation of the sex hormone binding globulin-homology domain of the PS molecule. We postulate that the loss of the highly conserved Arg474 might be responsible for the type I PS deficiency inherited in this family. 相似文献
28.
29.
30.