全文获取类型
收费全文 | 35723篇 |
免费 | 3752篇 |
国内免费 | 2550篇 |
专业分类
电工技术 | 2576篇 |
技术理论 | 8篇 |
综合类 | 5224篇 |
化学工业 | 2791篇 |
金属工艺 | 901篇 |
机械仪表 | 2314篇 |
建筑科学 | 3423篇 |
矿业工程 | 1285篇 |
能源动力 | 1257篇 |
轻工业 | 498篇 |
水利工程 | 1029篇 |
石油天然气 | 883篇 |
武器工业 | 596篇 |
无线电 | 3251篇 |
一般工业技术 | 4319篇 |
冶金工业 | 2202篇 |
原子能技术 | 326篇 |
自动化技术 | 9142篇 |
出版年
2024年 | 143篇 |
2023年 | 587篇 |
2022年 | 753篇 |
2021年 | 968篇 |
2020年 | 1121篇 |
2019年 | 1024篇 |
2018年 | 1078篇 |
2017年 | 1222篇 |
2016年 | 1311篇 |
2015年 | 1341篇 |
2014年 | 2042篇 |
2013年 | 2515篇 |
2012年 | 2255篇 |
2011年 | 2577篇 |
2010年 | 2052篇 |
2009年 | 2160篇 |
2008年 | 2226篇 |
2007年 | 2340篇 |
2006年 | 2175篇 |
2005年 | 1890篇 |
2004年 | 1527篇 |
2003年 | 1269篇 |
2002年 | 1101篇 |
2001年 | 883篇 |
2000年 | 768篇 |
1999年 | 675篇 |
1998年 | 528篇 |
1997年 | 472篇 |
1996年 | 397篇 |
1995年 | 384篇 |
1994年 | 316篇 |
1993年 | 270篇 |
1992年 | 248篇 |
1991年 | 179篇 |
1990年 | 146篇 |
1989年 | 167篇 |
1988年 | 129篇 |
1987年 | 66篇 |
1986年 | 91篇 |
1985年 | 67篇 |
1984年 | 66篇 |
1983年 | 47篇 |
1982年 | 53篇 |
1981年 | 41篇 |
1980年 | 31篇 |
1979年 | 31篇 |
1978年 | 29篇 |
1977年 | 26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 15 毫秒
11.
基于模式理论光栅椭偏参数反演的数值模拟 总被引:5,自引:2,他引:3
将一种广泛用于求解系统优化问题的方法——正单纯形法,求解光栅的椭偏方程。首先,利用求解光栅的傅立叶模式理论对TE和TM波的复反射系数进行求解。然后计算出其相应的椭偏参数(△,Ψ),并在该值的基础上加入不同偏差的随机高斯噪声,将加入噪声后的值(△m,Ψm)作为模拟测量值。最后使用优化算法进行反演。通过对几种常用面形光栅椭偏参数的数值模拟,一方面表明傅立叶模式理论计算光栅的椭偏参数不仅精度高。而且速度快;另一方面表明利用正单纯形法得到的光栅参数值很接近于正演时假设的参数值,从而从理论上证明了利用椭偏法测量光栅各种光学参数的可行性。 相似文献
12.
An analysis is made of the characteristic features and problems of the optimal processing of the results of measurements in the case of a random observation function utilizing a nonlinear Kalman filter. A method is proposed for increasing the convergence domain of the filter with additional processing of measurements in the frequency domain. 相似文献
13.
Starting from a microscopic Hamiltonian defined on a semi-infinite cubic lattice, and employing a mean-field approximation, the surface parameters relevant for wetting in confined ternary mixtures are derived. These are found in terms of the microscopic coupling constants, and yield a physical interpretation of their origins. In comparison with the standard expression for the surface free-energy density, several new terms arising from the derivation are identified. The influence of the surface parameters on a predicted unbinding transition in a mixture of oil, water, and amphiphile demonstrate that existing results are robust to the addition of the extra surface terms. 相似文献
14.
Requirements engineering in health care: the example of chemotherapy planning in paediatric oncology
Health care is characterized by highly complex processes of patient care that require unusual amount of communication between different health care professionals of different institutions. Sub-optimal processes can significantly impact on the patient’s health, increase the consumption of services and resources and in severe cases can lead to the patient death. For these reasons, requirements engineering for the development of information technology in health care is a complex process as well: without constant and rigorous evaluation, the impact of new systems on the quality of care is unknown and it is possible that badly designed systems significantly harm patients. To overcome these limitations, we present and discuss an approach to requirements engineering that we applied for the development of applications for chemotherapy planning in paediatric oncology. Chemotherapy planning in paediatric oncology is complex and time-consuming and errors must be avoided by all means. In the multi-hospital/multi-trial-centre environment of paediatric oncology, it is especially difficult and time-consuming to analyse requirements. Our approach combines a grounded theory approach with evolutionary prototyping based on the constant development and refinement of a generic domain model, in this case a domain model for chemotherapy planning in paediatric oncology. The prototypes were introduced in medical centres and final results show that the developed generic domain model is adequate. 相似文献
15.
Reviews the book by Baruss (see record 2003-02669-000), which reviews the experimental and phenomenological research on alterations of consciousness, ranging from sleep and dreaming to mystical and near-death experience. The reviewer suggests there is a clear agenda announced by the book's subtitle, "An Empirical Analysis for Social Scientists." In the view of Baruss, all too often in states of consciousness research a preoccupation with theory has kept investigators from full engagement with the actual data. The book provides readable and at times appropriately controversial discussions of empirical literature on dreaming and lucid dreams, daydreaming and fantasy proneness, hypnosis, dissociative identity disorder, shamanism and possession states, psychedelic drug research, parapsychology, trance-chanelling and mediumship, the alien abduction syndrome, classical mystical experience, out-of-body and near-death experiences, and recent attempts by MacDonald and others to assess individual differences in spirituality through multifactor questionnaires. However, the reviewer believes that the breadth of coverage of both recent and past research is too often highly selective, and that the author's rejection of theory is both questionable in itself and more illusion than reality. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
17.
This article deals with the kinetics of two-step anionic polymerization by way of a non-steady state method. Several molecular parameters can be evaluated using the formulae developed. A bimodal molecular weight distribution function for the resulting polymer is derived from the set of kinetic differential equations, which is in agreement with the experimental data reported. 相似文献
18.
本文介绍的基于信息的智能控制理论的发展过程,主要分为智能控制的信息指标和智能控制的信息结构分析两部分,文中在最后对这套理论可能的发展方向进行了探讨。 相似文献
19.
Anthony E. Bentley 《国际强度与非线性控制杂志
》1994,4(1):119-160
》1994,4(1):119-160
Two different control systems were developed using quantitative feedback theory for weld quality improvement. The first application to be discussed was designed for the resistance pinch welding process and uses electrode displacement and force as feedback parameters. A correlation between weld quality and electrode displacement is established for constant electrode force. The system is capable of producing repeatable welds of consistent quality, with wide variations in weld parameters. This is the first time feedback control has been successfully applied to pinch welding. The second example presented in this paper was developed for penetration control of the gas-tungsten-arc welding process. The feedback signal is obtained by measuring the amount of light emitted from the back side of the weld. Welds of constant penetration have been demonstrated in tests with travel speeds varying from 1.5 to 6 inches per minute and with 200 per cent changes in part thickness. 相似文献
20.
不等波纹函数低通原型的理论及应用 总被引:3,自引:0,他引:3
本文提出不等波纹函数低通原型,并对其理论进行初步探讨。切比雪夫函数及最平坦型巴特活兹函数皆为其特例。文中给出不等波纹函数的几个性质,最后给出两个应用实例,消除耦合环自感部分的影响;抑制高次模的微带圆盘腔带通滤波器。 相似文献