全文获取类型
收费全文 | 13228篇 |
免费 | 1259篇 |
国内免费 | 226篇 |
专业分类
电工技术 | 385篇 |
综合类 | 347篇 |
化学工业 | 3129篇 |
金属工艺 | 546篇 |
机械仪表 | 561篇 |
建筑科学 | 656篇 |
矿业工程 | 171篇 |
能源动力 | 423篇 |
轻工业 | 1737篇 |
水利工程 | 154篇 |
石油天然气 | 202篇 |
武器工业 | 22篇 |
无线电 | 1190篇 |
一般工业技术 | 2450篇 |
冶金工业 | 625篇 |
原子能技术 | 112篇 |
自动化技术 | 2003篇 |
出版年
2024年 | 59篇 |
2023年 | 223篇 |
2022年 | 439篇 |
2021年 | 629篇 |
2020年 | 476篇 |
2019年 | 366篇 |
2018年 | 573篇 |
2017年 | 583篇 |
2016年 | 669篇 |
2015年 | 556篇 |
2014年 | 704篇 |
2013年 | 1202篇 |
2012年 | 864篇 |
2011年 | 977篇 |
2010年 | 745篇 |
2009年 | 752篇 |
2008年 | 704篇 |
2007年 | 637篇 |
2006年 | 543篇 |
2005年 | 419篇 |
2004年 | 321篇 |
2003年 | 315篇 |
2002年 | 326篇 |
2001年 | 201篇 |
2000年 | 167篇 |
1999年 | 131篇 |
1998年 | 143篇 |
1997年 | 106篇 |
1996年 | 107篇 |
1995年 | 104篇 |
1994年 | 69篇 |
1993年 | 71篇 |
1992年 | 54篇 |
1991年 | 47篇 |
1990年 | 34篇 |
1989年 | 32篇 |
1988年 | 29篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 34篇 |
1984年 | 20篇 |
1983年 | 22篇 |
1982年 | 19篇 |
1981年 | 27篇 |
1980年 | 19篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1976年 | 15篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
This paper introduces genetic algorithms (GA) as a complete entity, in which knowledge of this emerging technology can be integrated together to form the framework of a design tool for industrial engineers. An attempt has also been made to explain “why” and “when” GA should be used as an optimization tool 相似文献
52.
根据转炉炼钢的物理化学反应机理,从质量平衡和能量平衡的计算出发,通过小参数变动,导出了增量式静态模型中矿石方程和供氧方程的系数。所得结论与新日铁资料基本相符。同时,还进行了炉料和产物的计算,分析了改变废钢比对生产的影响。 相似文献
53.
D.A. van Beek K.L. Man M.A. Reniers J.E. Rooda R.R.H. Schiffelers 《The Journal of Logic and Algebraic Programming》2006,68(1-2):129
The hybrid χ (Chi) formalism integrates concepts from dynamics and control theory with concepts from computer science, in particular from process algebra and hybrid automata. It integrates ease of modeling with a straightforward, structured operational semantics. Its ‘consistent equation semantics’ enforces state changes to be consistent with delay predicates, that combine the invariant and flow clauses of hybrid automata. Ease of modeling is ensured by means of the following concepts: (1) different classes of variables: discrete and continuous, of subclass jumping or non-jumping, and algebraic; (2) strong time determinism of alternative composition in combination with delayable guards; (3) integration of urgent and non-urgent actions; (4) differential algebraic equations as a process term as in mathematics; (5) steady-state initialization; and 6) several user-friendly syntactic extensions. Furthermore, the χ formalism incorporates several concepts for complex system specification: (1) process terms for scoping that integrate abstraction, local variables, local channels and local recursion definitions; (2) process definition and instantiation that enable process re-use, encapsulation, hierarchical and/or modular composition of processes; and (3) different interaction mechanisms: handshake synchronization and synchronous communication that allow interaction between processes without sharing variables, and shared variables that enable modular composition of continuous-time or hybrid processes. The syntax and semantics are illustrated using several examples. 相似文献
54.
Claude Robert Concepción S. Wilson Jean-François Gaudy Charles-Daniel Arreto 《Scientometrics》2007,73(2):231-256
During the 1974–2004 period, the sleep literature had quadrupled (2384 publications in 1974, and 9721 in 2004) while overall
scientific productivity had only doubled. The set of the seven most productive countries (USA, Japan, United Kingdom, Germany,
France, Canada and Italy) in sleep research, and the geographical region distribution remained stable over the three decades.
On the other hand several indicators appeared in the sleep research literature during the 1990s: the increasing productivity
of sleep researchers; the growing number of countries publishing on sleep; the continuous creation of sleep-focused journals;
the scattering of sleep publication among increasingly more scientific journals; the turnover among the leading journals;
and the emergence of new entities such as China, Turkey, and the European Union. 相似文献
55.
We give a parametrized family of rational interval maps of degree two, each ergodic, exact and preserving a measure equivalent to a Lebesgue measure. The family includes the unique quadratic Chebyshev polynomial as its only polynomial map. We extend the family to other settings on the circle and real line. We also give numerical approximations to the entropy of the equivalent invariant measure and the Hausdorff dimension of the singular measure of maximal entropy. 相似文献
56.
The behavior of an ultrasonic shot peening process is observed and analyzed by using a model of inelastic hard spheres in a gravitational field that are fluidized by a vibrating bottom wall (sonotrode) in a cylindrical chamber. A marked heterogeneous distribution of impacts appears when the collision between the shot and the side wall becomes inelastic with constant dissipation. This effect is one order of magnitude larger than the simple heterogeneity arising from boundary collision on the cylinder. Variable restitution coefficients bring the simulation closer to the general observation and allow the investigation of peening regimes with changing shot density. We compute within this model other physical quantities (impact velocities, impact angle, temperature and density profile) that are influenced by the number N of spheres. 相似文献
57.
Haley William E.; Larson Dale G.; Kasl-Godley Julia; Neimeyer Robert A.; Kwilosz Donna M. 《Canadian Metallurgical Quarterly》2003,34(6):626
Professional psychologists are increasingly likely to encounter opportunities to work with patients and families facing end-of-life issues. Psychologists can provide psychological assessment, intervention for patients and families, consultation with and support of health care team members, grief therapy, and program development and evaluation. Psychological services are useful for healthy individuals who wish to make thoughtful plans about their own future care, patients with life-limiting illnesses, families stressed by providing end-of-life care, bereaved individuals, and health care providers who face issues of burnout and strain. Several challenges for psychologists working in end-of-life care are noted, including training, development of clear roles, and reimbursement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
58.
Animesh Chakrabarti Man Mohan Sharma 《Journal of the American Oil Chemists' Society》1992,69(12):1251-1253
Anhydrous esterification of myristic acid with propylene was carried out in the temperature range of 110–145°C and pressure
from 190–195 psig in the presence of Amberlyst-15 (cation exchange resin) and Filtrol-24 (acid-treated clay) as catalysts.
The product ester, isopropyl myristate finds use in cosmetic and topical medicinal preparations where good absorption through
the skin is desired. Filtrol-24 is the catalyst of choice, and the recommended operating temperature is 130°C with a pressure
of 190 psig. 相似文献
59.
60.
Simpson Jeffry A.; Rholes William S.; Nelligan Julia S. 《Canadian Metallurgical Quarterly》1992,62(3):434
Examined how adult attachment styles moderate spontaneous behavior between dating couples when 1 member of the dyad is confronted with an anxiety-provoking situation. 83 dating couples were unobtrusively videotaped for 5 min in a waiting room while the woman waited to participate in an "activity" known to provoke anxiety in most people. Independent observers then evaluated each partner's behavior on several dimensions. Results revealed that persons with more secure attachment styles behaved differently than persons with more avoidant styles in terms of physical contact, supportive comments, and efforts to seek and give emotional support. Findings are discussed in the context of theory and research on attachment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献