全文获取类型
收费全文 | 27379篇 |
免费 | 2982篇 |
国内免费 | 1972篇 |
专业分类
电工技术 | 2069篇 |
综合类 | 3004篇 |
化学工业 | 3056篇 |
金属工艺 | 3307篇 |
机械仪表 | 2008篇 |
建筑科学 | 4383篇 |
矿业工程 | 890篇 |
能源动力 | 625篇 |
轻工业 | 1417篇 |
水利工程 | 963篇 |
石油天然气 | 654篇 |
武器工业 | 306篇 |
无线电 | 1986篇 |
一般工业技术 | 5184篇 |
冶金工业 | 1147篇 |
原子能技术 | 307篇 |
自动化技术 | 1027篇 |
出版年
2024年 | 133篇 |
2023年 | 397篇 |
2022年 | 650篇 |
2021年 | 847篇 |
2020年 | 880篇 |
2019年 | 818篇 |
2018年 | 763篇 |
2017年 | 1061篇 |
2016年 | 1172篇 |
2015年 | 1125篇 |
2014年 | 1456篇 |
2013年 | 1611篇 |
2012年 | 1913篇 |
2011年 | 2020篇 |
2010年 | 1470篇 |
2009年 | 1598篇 |
2008年 | 1537篇 |
2007年 | 1744篇 |
2006年 | 1662篇 |
2005年 | 1419篇 |
2004年 | 1210篇 |
2003年 | 1081篇 |
2002年 | 886篇 |
2001年 | 773篇 |
2000年 | 710篇 |
1999年 | 605篇 |
1998年 | 456篇 |
1997年 | 392篇 |
1996年 | 355篇 |
1995年 | 306篇 |
1994年 | 246篇 |
1993年 | 201篇 |
1992年 | 191篇 |
1991年 | 128篇 |
1990年 | 113篇 |
1989年 | 110篇 |
1988年 | 70篇 |
1987年 | 50篇 |
1986年 | 33篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 23篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1977年 | 2篇 |
1959年 | 2篇 |
1955年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The relation between the initial unbalance and the output signal of bridge circuits when acted upon simultaneously by the
physical factor being measured and the temperature of the surroundings when the bridge is supplied from a voltage or current
source is investigated. Analytic relations are obtained which explain the temperature dependence of the useful output voltage
under external physical action.
__________
Translated from Izmeritel’naya Tekhnika, No. 1, pp. 48–49, 2007. 相似文献
22.
O'Driscoll Michael P.; Poelmans Steven; Spector Paul E.; Kalliath Thomas; Allen Tammy D.; Cooper Cary L.; Sanchez Juan I. 《Canadian Metallurgical Quarterly》2003,10(4):326
This study examined organizational family-responsive policies, perceptions of the organization as family supportive, and supervisor support as issues that may be salient to the experience of conflict between paid employment (work) and family roles. Data were collected from 355 managerial personnel in New Zealand. Although work-family conflict and psychological strain were strongly linked, the availability of organizational policies had no significant association with levels of conflict or strain, whereas policy usage was related only to work-to-family interference and not to family-to-work interference. On the other hand, perceptions of the organization as family supportive and supervisor support for work-family balance displayed significant relationships with key variables, highlighting the importance of these variables for interventions designed to ameliorate the negative impact of work-family conflict on managerial well-being. Implications for the effective implementation of family-responsive interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
指出了为发展ADSL而提高市话音频铜线电缆的传输质量和维护水平的必要性,分析了铜线电缆线对有关指标参数低劣的原因和对传输ADSL的影响,并提出了一些改进的意见。 相似文献
24.
In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within
the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour;
the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian
(ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several
representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental
data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle
with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks
to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present
spurious oscillations.
Received: 20 March 2002 / Accepted: 15 October 2002
The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged. 相似文献
25.
Sixiong Han Yasuaki Ichikawa 《International journal for numerical methods in engineering》1995,38(24):4081-4100
In this paper, a mathematical model is proposed for the problem of the scattering of plane waves in a three-dimensional cracked materials. Instead of obtaining closed-form solutions as in conventional theoretical analysis methods, this approach, called the Equivalent Nodal Force (ENF) method formulates the mechanical effects of cracks as an equivalent nodal force in a numerical procedure, and physically translates cracked material into an equivalent continuous one. Several mechanical relations between waves and cracks are evident from this method. Also the results of several numerical calculations are presented and these are compared with those obtained by the conventional methods. 相似文献
26.
27.
本文研究了经济分析基本方法之一最优等效替代法的实质,系统地导出了被评价方案的绝对经济指标与相对经济指标的关系,并结合典型案例分析指出了该方法的应用条件,对正确进行建设项目的经济评价具有现实意义。 相似文献
28.
无间隙原子钢的微观结构特征和塑性应变比 总被引:1,自引:0,他引:1
采用X射线衍射的ODF和LP分析技术,SEM电子通道花样和蚀坑技术观测,研究了超深冲无间隙原子钢板的微观结构特征。结果表明:控制化学成分、保证基体纯净、优选工艺参数,促进强的γ-〈111〉∥N.D纤维织构的形成是获得优异成型性的关键。用CMTP方法,由ODF织构数据从理论计算了塑性应变比(r),表明rm值高达3.18。文中讨论了再结晶织构形成机制。 相似文献
29.
对于遂昌金矿合理的采场结构参数,目前没有理想的确定方法。本文联系上盘围岩的构造裂隙,矿房的支护形式等提出采场稳定跨度判断指标。经40个采场的检验,值信度达97.5%。 相似文献
30.
Zhen Wang 《Applied Composite Materials》1995,2(4):257-264
A bimodal Weibull distribution function was applied to analyse the strength distribution of glass fibre bundles under tensile impact. The simulation was performed using a one-dimensional damage constitutive model. The results show that there were two concurrent flaw populations in the fracture process. The regression analysis using the bimodal Weibull distribution function was in good agreement with experiment. 相似文献