全文获取类型
收费全文 | 106752篇 |
免费 | 11777篇 |
国内免费 | 6565篇 |
专业分类
电工技术 | 14457篇 |
技术理论 | 21篇 |
综合类 | 10286篇 |
化学工业 | 11318篇 |
金属工艺 | 3404篇 |
机械仪表 | 5231篇 |
建筑科学 | 13190篇 |
矿业工程 | 3269篇 |
能源动力 | 13817篇 |
轻工业 | 2526篇 |
水利工程 | 2385篇 |
石油天然气 | 2967篇 |
武器工业 | 1188篇 |
无线电 | 8278篇 |
一般工业技术 | 11645篇 |
冶金工业 | 5765篇 |
原子能技术 | 1555篇 |
自动化技术 | 13792篇 |
出版年
2024年 | 628篇 |
2023年 | 2222篇 |
2022年 | 3395篇 |
2021年 | 3848篇 |
2020年 | 4181篇 |
2019年 | 3745篇 |
2018年 | 3360篇 |
2017年 | 3943篇 |
2016年 | 4363篇 |
2015年 | 4310篇 |
2014年 | 7022篇 |
2013年 | 7219篇 |
2012年 | 7414篇 |
2011年 | 8396篇 |
2010年 | 6498篇 |
2009年 | 6685篇 |
2008年 | 6316篇 |
2007年 | 6799篇 |
2006年 | 5688篇 |
2005年 | 4593篇 |
2004年 | 3781篇 |
2003年 | 3204篇 |
2002年 | 2809篇 |
2001年 | 2359篇 |
2000年 | 2030篇 |
1999年 | 1677篇 |
1998年 | 1332篇 |
1997年 | 1097篇 |
1996年 | 974篇 |
1995年 | 808篇 |
1994年 | 696篇 |
1993年 | 573篇 |
1992年 | 479篇 |
1991年 | 390篇 |
1990年 | 324篇 |
1989年 | 312篇 |
1988年 | 246篇 |
1987年 | 159篇 |
1986年 | 155篇 |
1985年 | 158篇 |
1984年 | 146篇 |
1983年 | 96篇 |
1982年 | 122篇 |
1981年 | 73篇 |
1980年 | 69篇 |
1979年 | 55篇 |
1978年 | 42篇 |
1977年 | 37篇 |
1964年 | 26篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
阐述了时空效应规律在软土深基坑工程中的运用情况,实践证明,运用时空效应规律,能可靠而合理地利用土体自身在基坑开挖过程中控制土体位移的潜力而达到保护环境的目的。 相似文献
82.
L. V. El’nikova 《Journal of Superconductivity and Novel Magnetism》2007,20(2):197-199
We describe the lyotropic liquid crystalline phase transitions in the lipid mixture dipalmitoil-PC/dilauroy-PC/cholesterol
by 3D spin-1 lattice model. The formation of nanoscale domains with the characteristic size about 300 nm was studied in experiments
on confocal fluorescence microscopy (CFM) (G. V. Feigenson and J. T. Buboltz, Biophys. J.
80, 2775 (2001)). The structure parameters of the lamellar vesicle in dipalmitoil-PC-rich phase, corresponding to these regions,
are verified by numerical Monte Carlo simulations on the lattice. We point its superconductivity analogy properties at the
region of phase stability for composition-dependent nanoscopic region. 相似文献
83.
新经济增长理论对我国人力资本发展的借鉴 总被引:3,自引:0,他引:3
新经济增长理论为人力资本理论注入了新的内容,为各国如何利用人力资本发展经济提供了理论指导。分析了新经济增长理论中有关人力资本的理论,以此对我国经济和人力资本的发展提出了一些借鉴;收益递增模型。 相似文献
84.
A motivational model of rural students' intentions to persist in, versus drop out of, high school. 总被引:1,自引:0,他引:1
Using self-determination theory, the authors tested a motivational model to explain the conditions under which rural students formulate their intentions to persist in, versus drop out of, high school. The model argues that motivational variables underlie students' intentions to drop out and that students' motivation can be either supported in the classroom by autonomy-supportive teachers or frustrated by controlling teachers. LISREL analyses of questionnaire data from 483 rural high school students showed that the provision of autonomy support within classrooms predicted students' self-determined motivation and perceived competence. These motivational resources, in turn, predicted students' intentions to persist, versus drop out, and they did so even after controlling for the effect of achievement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
Argyris G. Kagiannas Thanassis Didis Dimitris Th. Askounis John Psarras 《国际能源研究杂志》2003,27(2):173-186
The needs that an energy supply system must meet are constantly changing, due to technological, social and political reasons. Effective energy planning is a dynamic process that is repeated periodically and adjusts to changing conditions. Energy decision makers and planners are no longer able to rely on inductive decision making since they have to investigate the effect of various decision parameters and possible future changes. To help in this process, models have been developed where estimates of future load growth, candidate power plants, fuels and other key factors can be introduced, from which the planners can evaluate decision parameters and the available alternatives. The paper presents the different methodologies and practices that are used by 11 energy models for energy demand forecasting, supply side management and generation expansion planning, demand side management and integrated resource planning. The paper concludes to the presentation of a strategic appraisal of the examined energy models appropriate for energy planning in Mozambique. Three models are proposed for conducting demand forecasting, generation expansion planning and demand side management. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
86.
87.
Academically selective schools are intended to affect academic self-concept positively, but theoretical and empirical research demonstrates that the effects are negative. The big-fish--little-pond effect (BFLPE), an application of social comparison theory to educational settings, posits that a student will have a lower academic self-concept in an academically selective school than in a nonselective school. This study, the largest cross-cultural study of the BFLPE ever undertaken, tested theoretical predictions for nationally representative samples of approximately 4,000 15-year-olds from each of 26 countries (N=103,558) who completed the same self-concept instrument and achievement tests. Consistent with the BFLPE, the effects of school-average achievement were negative in all 26 countries (M beta=-.20, SD=.08), demonstrating the BFLPE's cross-cultural generalizability. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
A. G. ATKINS Z. CHEN B. COTTERELL 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(1):67-77
In this paper, energy dissipation rate D vs. Δa curves in ductile fracture are predicted using a ‘conversion’ between loads, load‐point displacements and crack lengths predicted by NLEFM and those found in real ELPL propagation. The NLEFM/ELPL link was recently discovered for the DCB testpiece, and we believe it applies to other cracked geometries. The predictions for D agree with experimental results. The model permits a crack tip toughness R(Δa) which rises from Jc and saturates out when (if) steady state propagation is reached after a transient stage in which all tunnelling, crack tip necking and shear lip formation is established. JR is always greater than the crack tip R(Δa) and continues to rise even after R(Δa) levels off. The analysis is capable of predicting the usual D vs. Δa curves in the literature which have high initial values and fall monotonically to a plateau at large Δa. It also predicts that D curves for CCT testpieces should be higher than those for SENB/CT, as found in practice. The possibility that D curves at some intermediate Δa may dip to a minimum below the levelled‐off value at large Δa is predicted and confirmed by experiment. Recently reported D curves that have smaller initial D than the D‐values after extensive propagation can also be predicted. The testpiece geometry and crack tip R(Δa) conditions required to produce these different‐shaped D vs. Δa curves are established and confirmed by comparison with experiment. The energy dissipation rate D vs. Δa is not a transferable property as it depends on geometry. The material characteristic R(Δa) may be the ‘transferable property’ for scaling problems in ELPL fracture. How it can be deduced from D vs. Δa curves (and by implication, JR vs. Δa curves) is established. 相似文献
89.
本文通过对中州分公司正在考虑建设的信息网建设实际情况,结合山东分公司、广西分公司取得的经验,对计量管理信息网的应用进行了探讨。 相似文献