全文获取类型
收费全文 | 8225篇 |
免费 | 104篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 58篇 |
综合类 | 2篇 |
化学工业 | 693篇 |
金属工艺 | 60篇 |
机械仪表 | 147篇 |
建筑科学 | 201篇 |
矿业工程 | 10篇 |
能源动力 | 120篇 |
轻工业 | 386篇 |
水利工程 | 37篇 |
石油天然气 | 27篇 |
无线电 | 544篇 |
一般工业技术 | 835篇 |
冶金工业 | 4567篇 |
原子能技术 | 77篇 |
自动化技术 | 568篇 |
出版年
2021年 | 59篇 |
2020年 | 44篇 |
2019年 | 56篇 |
2018年 | 52篇 |
2017年 | 55篇 |
2016年 | 51篇 |
2015年 | 42篇 |
2014年 | 80篇 |
2013年 | 217篇 |
2012年 | 97篇 |
2011年 | 177篇 |
2010年 | 140篇 |
2009年 | 126篇 |
2008年 | 185篇 |
2007年 | 166篇 |
2006年 | 147篇 |
2005年 | 137篇 |
2004年 | 117篇 |
2003年 | 119篇 |
2002年 | 154篇 |
2001年 | 113篇 |
2000年 | 113篇 |
1999年 | 241篇 |
1998年 | 1312篇 |
1997年 | 785篇 |
1996年 | 545篇 |
1995年 | 303篇 |
1994年 | 278篇 |
1993年 | 304篇 |
1992年 | 79篇 |
1991年 | 111篇 |
1990年 | 86篇 |
1989年 | 102篇 |
1988年 | 127篇 |
1987年 | 86篇 |
1986年 | 78篇 |
1985年 | 95篇 |
1984年 | 78篇 |
1983年 | 56篇 |
1982年 | 66篇 |
1981年 | 72篇 |
1980年 | 88篇 |
1979年 | 56篇 |
1978年 | 60篇 |
1977年 | 180篇 |
1976年 | 355篇 |
1975年 | 35篇 |
1974年 | 47篇 |
1973年 | 41篇 |
1972年 | 29篇 |
排序方式: 共有8332条查询结果,搜索用时 18 毫秒
21.
Why was there a preponderance of women engaged in laboratory-based studies of animal behavior in Britain in the early years of the 20th century? As a new experimental subject with recently neglected potential, animal psychology then represented an opportunity for women to make further inroads into academic science. Because the study of psychology before World War I offered negligible professional opportunities for the application of the subject, the intake of students was restricted. Perhaps this encouraged academic access to it by aspiring female scientists who felt that career prospects, uncertain and socially unexpected of them in any case, were worth chancing for greater long-term rewards. The academic circumstances and contributions of 3 British female pioneers in experimental comparative psychology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
22.
A new spreadsheet-cell-object-oriented algorithm for the first-order reliability method is proposed and illustrated for cases with correlated nonnormals and explicit and implicit performance functions. The new approach differs from the writers earlier algorithm by obviating the need for computations of equivalent normal means and equivalent normal standard deviations. It obtains the solution faster and is more efficient, robust, and succinct. Other advantages include ease of initialization prior to constrained optimization, ease of randomization of initial values for checking robustness, and fewer required optimization constraints during spreadsheet-automated search for the design point. Two cases with implicit performance functions, namely an asymmetrically loaded beam on Winkler medium and a strut with complex supports are analyzed using the new approach and discussed. Comparisons are also made between the proposed approach and that based on Rosenblatt transformation. 相似文献
23.
Emergency department status boards: user-evolved artefacts for inter- and intra-group coordination 总被引:1,自引:1,他引:0
Robert L. Wears Shawna J. Perry Stephanie Wilson Julia Galliers James Fone 《Cognition, Technology & Work》2007,9(3):163-170
Large, easily viewed status boards are commonly used in some healthcare settings such as emergency departments, operating
theaters, intensive care units, and inpatient wards. Because these artefacts were developed by front-line users, and have
little to no supervisory or regulatory control, they offer valuable insights into the theories of work and hazard held by
those users. Although the status boards case were locally developed over many years for within-group coordination, they have
also become useful for between-group coordination across organizational boundaries. In this paper, we compare and contrast
the use of such status boards in two disparate settings: a US emergency department, and a UK pediatric ward, and note striking
similarities in their form and usage, despite the large differences in setting. 相似文献
24.
While information systems continue to be promoted within organizations as tools to support strategic decision-making, there is growing concern over the ability of such systems to model the social and political complexity of the situations to which they are being applied. This paper examines the nature of organizational decision-making and the use of computer-based systems to support this activity. The debate queries the extent to which such artifacts should be allowed to become enmeshed and embedded within the strategic decision-making activities of organizations which operate within increasingly complex environments. 相似文献
25.
Y Yang SE Raper JA Cohn JF Engelhardt JM Wilson 《Canadian Metallurgical Quarterly》1993,90(10):4601-4605
Cystic fibrosis (CF) is an inherited disease of epithelial cell ion transport that is associated with pathology in multiple organ systems, including lung, pancreas, and liver. As treatment of the pulmonary manifestations of CF has improved, management of CF liver disease has become increasingly important in adult patients. This report describes an approach for treating CF liver disease by somatic gene transfer. In situ hybridization and immunocytochemistry analysis of rat liver sections indicated that the endogenous CFTR (cystic fibrosis transmembrane conductance regulator) gene is primarily expressed in the intrahepatic biliary epithelial cells. To specifically target recombinant genes to the biliary epithelium in vivo, recombinant adenoviruses expressing lacZ or human CFTR were infused retrograde into the biliary tract through the common bile duct. Conditions were established for achieving recombinant gene expression in virtually all cells of the intrahepatic bile ducts in vivo. Expression persisted in the smaller bile ducts for the duration of the experiment, which was 21 days. These studies suggest that it may be feasible to prevent CF liver disease by genetically reconstituting CFTR expression in the biliary tract, using an approach that is clinically feasible. 相似文献
26.
27.
Ehrlichia spp. from human and equine sources in the northeastern Unites States were detected by PCR, isolated, and propagated in the HL-60 promyelocytic leukemia cell line. Growth of Ehrlichia from both equine and human sources was enhanced by addition of retinoic acid, which causes granulocytic differentiation of the HL-60 cells. DNA sequencing of a portion of the 16S rDNA gene supported the hypothesis that the same pathogen was responsible for both equine and human granulocytic ehrlichiosis. 相似文献
28.
29.
30.
KE Goodwill C Sabatier C Marks R Raag PF Fitzpatrick RC Stevens 《Canadian Metallurgical Quarterly》1997,4(7):578-585
Tyrosine hydroxylase (TyrOH) catalyzes the conversion of tyrosine to L-DOPA, the rate-limiting step in the biosynthesis of the catecholamines dopamine, adrenaline, and noradrenaline. TyrOH is highly homologous in terms of both protein sequence and catalytic mechanism to phenylalanine hydroxylase (PheOH) and tryptophan hydroxylase (TrpOH). The crystal structure of the catalytic and tetramerization domains of TyrOH reveals a novel alpha-helical basket holding the catalytic iron and a 40 A long anti-parallel coiled coil which forms the core of the tetramer. The catalytic iron is located 10 A below the enzyme surface in a 17 A deep active site pocket and is coordinated by the conserved residues His 331, His 336 and Glu 376. The structure provides a rationale for the effect of point mutations in TyrOH that cause L-DOPA responsive parkinsonism and Segawa's syndrome. The location of 112 different point mutations in PheOH that lead to phenylketonuria (PKU) are predicted based on the TyrOH structure. 相似文献