全文获取类型
收费全文 | 2462篇 |
免费 | 434篇 |
国内免费 | 105篇 |
专业分类
电工技术 | 47篇 |
综合类 | 271篇 |
化学工业 | 778篇 |
金属工艺 | 27篇 |
机械仪表 | 48篇 |
建筑科学 | 193篇 |
矿业工程 | 45篇 |
能源动力 | 21篇 |
轻工业 | 39篇 |
水利工程 | 37篇 |
石油天然气 | 126篇 |
武器工业 | 6篇 |
无线电 | 93篇 |
一般工业技术 | 156篇 |
冶金工业 | 558篇 |
原子能技术 | 10篇 |
自动化技术 | 546篇 |
出版年
2024年 | 4篇 |
2023年 | 19篇 |
2022年 | 23篇 |
2021年 | 34篇 |
2020年 | 45篇 |
2019年 | 38篇 |
2018年 | 61篇 |
2017年 | 75篇 |
2016年 | 126篇 |
2015年 | 139篇 |
2014年 | 179篇 |
2013年 | 200篇 |
2012年 | 126篇 |
2011年 | 172篇 |
2010年 | 164篇 |
2009年 | 173篇 |
2008年 | 163篇 |
2007年 | 154篇 |
2006年 | 190篇 |
2005年 | 147篇 |
2004年 | 140篇 |
2003年 | 125篇 |
2002年 | 78篇 |
2001年 | 76篇 |
2000年 | 38篇 |
1999年 | 24篇 |
1998年 | 30篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 12篇 |
1993年 | 19篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1981年 | 3篇 |
1966年 | 3篇 |
1962年 | 4篇 |
1959年 | 8篇 |
1958年 | 6篇 |
1957年 | 8篇 |
1956年 | 7篇 |
1955年 | 4篇 |
1954年 | 5篇 |
排序方式: 共有3001条查询结果,搜索用时 15 毫秒
81.
Simon von Danwitz 《International Journal of Project Management》2018,36(3):525-541
Although the management of inter-firm projects is increasingly being researched in a wide range of academic fields (project management, alliances and networks, organization studies), the findings of these studies rarely cross theoretical boundaries. In the present study, a systematic literature review of 219 contributions from 26 years of academic research on managing inter-firm projects identifies 22 key management issues underlying its contributions. Based on a two-dimensional framework (project stage and analytical sphere), a structured and integrative synthesis of relevant studies is outlined. Based on these findings, future investigations are proposed to focus on dynamic, contextual and structural aspects of the management of inter-firm projects. 相似文献
82.
包装企业实施绿色营销是企业提升持续竞争力的要求,是包装相关行业突破绿色贸易壁垒的要求,是我国发展循环经济的要求,也是世界环保潮流的要求。然而,我国包装企业存在专业化水平低、包装营销观念陈旧、包装产品定价不科学、销售模式落后、服务意识不强等问题。包装企业要在坚持绿色观念的基础上开展营销活动,遵循4R1D原则,把握市场趋势,制定反映环境成本的价格,完善销售渠道,先服务后生产,做好绿色公关。 相似文献
83.
Perceived support is consistently linked to good mental health, which is typically explained as resulting from objectively supportive actions that buffer stress. Yet this explanation has difficulty accounting for the often-observed main effects between support and mental health. Relational regulation theory (RRT) hypothesizes that main effects occur when people regulate their affect, thought, and action through ordinary yet affectively consequential conversations and shared activities, rather than through conversations about how to cope with stress. This regulation is primarily relational in that the types of people and social interactions that regulate recipients are mostly a matter of personal taste. RRT operationally defines relationships quantitatively, permitting the clean distinction between relationships and recipient personality. RRT makes a number of new predictions about social support, including new approaches to intervention. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
84.
通过对Desakota理论的简述,总结出Desakota理论承前启后的创新视野和学术价值,并以Desakota理论从亚洲视野的角度理解其对珠江三角洲地区城市化进程研究的影响和启示。 相似文献
85.
86.
Gabriel Allison S.; Diefendorff James M.; Erickson Rebecca J. 《Canadian Metallurgical Quarterly》2011,96(5):1095
Focusing on a sample of nurses, this investigation examined the relationships of daily task accomplishment satisfaction (for direct and indirect care tasks) with changes in positive and negative affect from preshift to postshift. Not accomplishing tasks to one's satisfaction was conceptualized as a daily workplace stressor that should increase daily negative affect and decrease daily positive affect from preshift to postshift. Further, because of the greater centrality of direct care nursing tasks to nursing work role identities (relative to indirect care tasks), we expected that task accomplishment satisfaction (or lack thereof) for these tasks would have stronger effects on changes in affect than would task accomplishment satisfaction for indirect care tasks. We also examined 2 person-level resources, collegial nurse–physician relations and psychological resilience, as moderators of the relationships among these daily variables, with the expectation that these resources would buffer the harmful effects of low task accomplishment satisfaction on nurse affect. Results supported almost all of the proposed effects, though the cross-level interactions were observed only for the effects of indirect care task accomplishment satisfaction on affect and not for direct care task accomplishment satisfaction on affect. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
87.
Social dominance theory (Sidanius & Pratto, 1999) contends that institutional-level mechanisms exist that reinforce and perpetuate existing group-based inequalities, but very few such mechanisms have been empirically demonstrated. We propose that gendered wording (i.e., masculine- and feminine-themed words, such as those associated with gender stereotypes) may be a heretofore unacknowledged, institutional-level mechanism of inequality maintenance. Employing both archival and experimental analyses, the present research demonstrates that gendered wording commonly employed in job recruitment materials can maintain gender inequality in traditionally male-dominated occupations. Studies 1 and 2 demonstrated the existence of subtle but systematic wording differences within a randomly sampled set of job advertisements. Results indicated that job advertisements for male-dominated areas employed greater masculine wording (i.e., words associated with male stereotypes, such as leader, competitive, dominant) than advertisements within female-dominated areas. No difference in the presence of feminine wording (i.e., words associated with female stereotypes, such as support, understand, interpersonal) emerged across male- and female-dominated areas. Next, the consequences of highly masculine wording were tested across 3 experimental studies. When job advertisements were constructed to include more masculine than feminine wording, participants perceived more men within these occupations (Study 3), and importantly, women found these jobs less appealing (Studies 4 and 5). Results confirmed that perceptions of belongingness (but not perceived skills) mediated the effect of gendered wording on job appeal (Study 5). The function of gendered wording in maintaining traditional gender divisions, implications for gender parity, and theoretical models of inequality are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
88.
Instability of granular material may lead to catastrophic events such as the gross collapse of earth structures, and thus it is an important topic in geotechnical engineering. In this paper, we adopt the micromechanics approach for constitutive modeling, in which the soil is considered an assembly of particles, and the stress-strain relationship for the assembly is determined by integrating the behavior of the interparticle contacts in all orientations. Although analyses regarding material instability have been extensively studied for a soil element at the constitutive level, it has not been considered at the interparticle contact level. Through an eigenvalue analysis, two modes of instability are identified at the local contact level: the singularity of tangential stiffness matrix and the loss of positiveness of second-order work. The constitutive model is applied to simulate drained and undrained triaxial tests on Toyoura sand of various densities under various confining pressures. The predictions are compared with experimentally measured instability at the assembly level. The modes of stability at the interparticle contact level and their relations to the overall instability of the assembly are also analyzed. 相似文献
89.
This paper presents simulations of the mechanical behavior of reconstituted and natural soils using a new model presented in a companion paper and referred to as the “Sydney soil model.” It is demonstrated that the performance of the proposed model is essentially the same as that of modified Cam clay model when describing the behavior of clays in laboratory reconstituted states. The model has also been employed to simulate the drained and undrained behavior of structured clays and sands, including calcareous clay and sand. Five sets of conventional triaxial tests and one set of true triaxial tests have been considered. It is demonstrated that the new model provides satisfactory qualitative and quantitative modeling of many important features of the behavior of structured soils, particularly in capturing various patterns of the stress and strain behavior associated with soil type and structure. A general discussion of the model parameters is also included. It is concluded that the Sydney soil model is suitable for representing the behavior of many soils if their ultimate state during shearing can be defined by an intrinsic and constant stress ratio M* and a unique relationship between mean effective stress and voids ratio, i.e., a unique p′-e curve. 相似文献
90.
峰均比(PAR)过高是正交频分复用(OFDM)技术亟待解决的关键问题之一。在基于判决指导信道估计的叠加训练序列OFDM系统中,提出一种选择性叠加训练序列降低系统PAR的方法。该方法使用多个相互独立的训练序列分别与数据序列叠加,选择其中PAR性能最好的用于传输,接收端完成信道估计的同时消除了训练序列对数据序列的影响,因此没有增加接收端的复杂度。计算机仿真结果表明:该方法在不增加接收端复杂度的前提下,有效降低了系统PAR,且对信道估计性能不造成任何影响,因此该方法可用于实际系统中。 相似文献