全文获取类型
收费全文 | 1640篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 48篇 |
金属工艺 | 11篇 |
机械仪表 | 19篇 |
建筑科学 | 11篇 |
能源动力 | 9篇 |
轻工业 | 62篇 |
水利工程 | 2篇 |
无线电 | 30篇 |
一般工业技术 | 81篇 |
冶金工业 | 1333篇 |
原子能技术 | 1篇 |
自动化技术 | 36篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 27篇 |
2012年 | 13篇 |
2011年 | 17篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 16篇 |
2007年 | 11篇 |
2006年 | 21篇 |
2005年 | 9篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 36篇 |
1998年 | 430篇 |
1997年 | 208篇 |
1996年 | 146篇 |
1995年 | 92篇 |
1994年 | 80篇 |
1993年 | 76篇 |
1992年 | 9篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 24篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 25篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 28篇 |
1976年 | 88篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1970年 | 2篇 |
排序方式: 共有1646条查询结果,搜索用时 15 毫秒
71.
To date, the visualization of beta2-adrenergic receptor (beta2AR) trafficking has been largely limited to immunocytochemical analyses of acute internalization events of epitope-tagged receptors in various transfection systems. The development of a beta2AR conjugated with green fluorescent protein (beta2AR-GFP) provides the opportunity for a more extensive optical analysis of beta2AR sequestration, down-regulation, and recycling in cells. Here we demonstrate that stable expression of beta2AR-GFP in HeLa cells enables a detailed temporal and spatial analysis of these events. Time-dependent colocalization of beta2AR-GFP with rhodamine-labeled transferrin and rhodamine-labeled dextran following agonist exposure demonstrates receptor distribution to early endosomes (sequestration) and lysosomes (down-regulation), respectively. The observed temporal distribution of beta2AR-GFP was consistent with measures of receptor sequestration and down-regulation generated by radioligand-receptor binding assays. Cells stimulated with different beta-agonists revealed time courses of beta2AR-GFP redistribution reflective of the intrinsic activity of each agonist. 相似文献
72.
In studies of T cell responses to synthetic peptides we have observed agonist and antagonist activities associated with contaminants identified within the parent synthesis. The synthesis of two candidate analogues implied by a peptide contaminant formed during the synthesis of La 51-58 (IMIKFNRL) has been carried out. The peptide contaminant was 17-18 Da smaller than the parent peptide consistent with a modified asparagine residue at position 6 and so we synthesised both an aspartimide and a nitrile analogue, representing cyclisation or dehydration of the asparagine residue. The candidate aspartimide and nitrile analogues both bound empty MHC class I molecules to form allo determinants recognised by monoclonal antibodies. These results demonstrate that altered synthetic peptides can bind class I MHC molecules and prompt caution in the use of synthetic peptides as a source of immunising antigen. 相似文献
73.
A method has been developed for the measurement of peak concentrations of extinguishing agents. The values will be used to provide design data for total flooding automatic systems. The values obtained are outside the true limits of flammability and therefore contain a built-in safety factor. The significance of these measurements is discussed in relation to the protection provided by an automatic system. 相似文献
74.
Six patients with classical transient ischemic attacks that were not directly related to extracranial carotid disease are presented. These cases were selected to include a variety of pathologic conditions: one case each of brain tumor, arteriovenous malformation, chronic subdural hematoma, cervical spondylosis, and two cases of giant intracranial aneurysms. These case histories are significant because they illustrate that without complete angiographic investigation, tragic results could have and did occur in some cases. Transient ischemic attacks should be considered as a symptom of various possible pathologic conditions, and a careful search for the cause must be pursued aggressively. 相似文献
75.
The application of alumino silicate alkali ion sources to the study of ion desorption of surface gas
Investigations are described which illustrate the compatibility of alumino silicate alkali ion sources with an UHV (~10?11 torr) vacuum environment. The application of the sources to the determination of ion desorption efficiency of surface gas is demonstrated, as well as their use as a basis for a technique of ion stimulated surface gas analysis. 相似文献
76.
77.
A numerical model for two-dimensional magnetic field problems called the graph-theoretic field model is presented. The theoretical framework of the model places the finite difference and Finite element method in a unifying perspective and brings the solution of magnetic field problems into the well-proven realm of computer-aided design of discrete physical systems. The field distribution in a transformer core is obtained to illustrate the modeling procedure. 相似文献
78.
Low-ash vitrinite concentrates of representative South African coals have been prepared and analysed. Various properties when plotted against carbon content show inflections at to 2% lower carbon content than normal British coals. These differences are ascribed to the heating effects of dolerite intrusions. 相似文献
79.
Germfree mice were immunized orally or intraperitoneally for 6 weeks with heat-killed vaccines of indigenous Escherichia coli or nonindigenous E. coli O 127: B8 before colonization with these strains. The mice exhibited increases in specific serum antibodies and intestinal immunoglobulin A reacting with the E coli antigens. Prior immunization did not reduce the gastrointestinal population levels of the E. coli strains attained 3 and 7 days after colonization. Neither oral nor intraperitoneal immunization with the E. coli strains before colonization decreased the incidence of bacterial translocation to the mesenteric lymph nodes or reduced the number of viable E. coli cells per mesenteric lymph node. There also was no relation in individual mice between serum antibody titers and the numbers of viable E. coli cells translocating to the mesenteric lymph nodes. Thus, prior vaccination with E. coli in this study did not decrease the incidence or reduce the numbers of viable E. coli translocating to the mesenteric lymph nodes in gnotobiotic mice monoassociated with E. coli. 相似文献
80.
PM Johnson AO Ogbimi MJ Diver AW Thomson RD Bremner CH Horne 《Canadian Metallurgical Quarterly》1980,59(2):437-440
Placental protein 5 (PP5), pregnancy-specific glycoprotein (SP1), pregnancy-associated alpha 2-glycoprotein (SP3) and chorionic gonadotrophin could not be demonstrated in appreciable molar quantities in the soluble fraction from microvillous plasma membrane preparations isolated from the syncytiotrophoblast of full-term human placentae. However, progesterone, total oestriol and placental lactogen may have some association with this membrane. 相似文献