全文获取类型
收费全文 | 9326篇 |
免费 | 1373篇 |
国内免费 | 658篇 |
专业分类
电工技术 | 809篇 |
综合类 | 1528篇 |
化学工业 | 635篇 |
金属工艺 | 187篇 |
机械仪表 | 589篇 |
建筑科学 | 453篇 |
矿业工程 | 148篇 |
能源动力 | 204篇 |
轻工业 | 247篇 |
水利工程 | 146篇 |
石油天然气 | 170篇 |
武器工业 | 116篇 |
无线电 | 1393篇 |
一般工业技术 | 1537篇 |
冶金工业 | 229篇 |
原子能技术 | 63篇 |
自动化技术 | 2903篇 |
出版年
2024年 | 16篇 |
2023年 | 131篇 |
2022年 | 158篇 |
2021年 | 257篇 |
2020年 | 335篇 |
2019年 | 367篇 |
2018年 | 389篇 |
2017年 | 409篇 |
2016年 | 469篇 |
2015年 | 426篇 |
2014年 | 530篇 |
2013年 | 658篇 |
2012年 | 691篇 |
2011年 | 694篇 |
2010年 | 494篇 |
2009年 | 535篇 |
2008年 | 545篇 |
2007年 | 574篇 |
2006年 | 505篇 |
2005年 | 411篇 |
2004年 | 371篇 |
2003年 | 377篇 |
2002年 | 289篇 |
2001年 | 262篇 |
2000年 | 237篇 |
1999年 | 163篇 |
1998年 | 157篇 |
1997年 | 165篇 |
1996年 | 113篇 |
1995年 | 95篇 |
1994年 | 91篇 |
1993年 | 68篇 |
1992年 | 68篇 |
1991年 | 47篇 |
1990年 | 43篇 |
1989年 | 30篇 |
1988年 | 32篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1966年 | 5篇 |
1964年 | 13篇 |
1963年 | 6篇 |
1958年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Delevoye-Turrell Yvonne; Giersch Anne; Wing Alan M.; Danion Jean-Marie 《Canadian Metallurgical Quarterly》2007,116(1):56
Many everyday activities depend on the capacity to organize and smoothly execute motor sequences. The authors tested the hypothesis that a sequencing deficit is associated with schizophrenia. They used a new method to distinguish between lower and higher order mechanisms for the impairment. The 1st task involved triggered sequences in which sensory information from 1 movement was the cue for initiation of the following movement. Results showed that the motor sequences were performed as fluently in patients as in controls. The 2nd and 3rd tasks involved sequences in which the entire movement sequence could be preplanned. Patients executed the sequences less fluently than controls but only under the condition where action sequences were required. Furthermore, the patients' fluency deficit increased with sequence complexity. The high discrimination power of Task 3 gave the authors a means to control for a potential psychometric confound involving differential discriminating power and to argue in favor of a specific higher order motor fluency deficit in patients with schizophrenia. It is suggested that basic lower order mechanisms that integrate sensory information with outgoing motor commands are preserved in schizophrenia, whereas higher order integrative mechanisms that are required for the smooth coordination of motor sequences are impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
992.
已往库存论中的决策模型,它是把现实过程用数学的方法进行分析,得到决策值,但不能看到决策的过程,不能反映出现实生活中的不确定性、动态性。运用Delphi 7.0和SQL server 2000对销售过程进行了动态仿真,利用Newsboy模型的推广(S,s)订购策略来监控库存并做出决策,这样就体现出此过程的不确定性、动态性;且举出了一个仿真商品销售的实例,对其中的一些关键技术,如何仿真、算法的实现等进行了阐述。 相似文献
993.
In this report, we describe the nature of intermediate order in silicon as determined by recent measurements on thin films using transmission electron microscopy (TEM) and Raman scattering. The TEM images show in addition to the expected continuous random network (CRN), the presence of highly ordered quasi-one-dimensional “chain-like objects” (CLO's) that are 1–2 nm wide and tens of nm long that meander and show some evidence of cross-linking with each other. The presence of these objects correlate to a Raman feature centered at 490 cm−1 whose width is 35–40 cm−1, and is used to quantify the heterogeneity in terms of the CLO and CRN (=475 cm−1 scattering) concentrations. The 490 and 35 cm−1 values are consistent with bond angle deviations approaching 0°, and thus reinforces an association with the CLOs. We find that in reference quality a-Si:H (made using pure SiH4), the CLO concentration is about 5 vol%, while in state-of-the-art material using high H2 levels of dilution during processing, it increases to about 15%. Increased stability of such material to light-soaking is thus not mediated by a direct volumetric replacement of poor with high-quality components. Rather, an important characteristic of intermediate order in silicon is the low-dimensional aspect of its order, which allows it to influence more total volume than which it is itself composed. Consistent with these and other recent findings, we propose a tensegrity model of amorphous silicon. 相似文献
994.
将逻辑程序系统由一阶逻辑中解放出来是复杂对象推理所迫切需要的.本文提出扩展的逻辑程序语言HILOG并建立其语义理论,扩充了逻辑程序系统的形式语义.HILOG为一带类型语言.通过建立诸如p-包含及装配/拆卸等代数概念,本文扩充了逻辑满足及模型比较等概念,证明了一HILOG程序具有一最小模型闭包及标准(装配形式)最小模型的唯一性,提出了模型的p-相交定理及扩充的最小模型极小不动点性质.一阶逻辑程序语义在上述各方面恰为HILOG语义之特殊情况,二者语义上的联系提供了将HILOG程序映射到一阶系统的可能性. 相似文献
995.
Using the programming-language concept of continuations, we propose a new, multimodal analysis of quantification in Type Logical Grammar. Our approach provides a geometric view of in-situ quantification in terms of graphs, and motivates the limited use of empty antecedents in derivations. Just as continuations are the tool of choice for reasoning about evaluation order and side effects in programming languages, our system provides a principled, type-logical way to model evaluation order and side effects in natural language. We illustrate with an improved account of quantificational binding, weak crossover, wh-questions, superiority, and polarity licensing. 相似文献
996.
二氧化碳加氢直接合成二甲醚催化剂的研究——沉淀次序对复合催化剂结构和性能的影响 总被引:2,自引:0,他引:2
以草酸乙醇溶液为沉淀剂,采用不同的沉淀次序(并流、反加和正加)制备了CuO-ZnO-Al2O3/HZSM-5复合型催化剂,对CO2加氢直接合成二甲醚反应的催化活性顺序为:并流法催化剂>反加法催化剂>正加法催化剂。3种复合催化剂的还原温度由低到高的顺序为:并流法催化剂<反加法催化剂<正加法催化剂。在沉淀过程中,反加法和正加法均形成类胶体沉淀,相应催化剂的比表面积也较大。IR研究发现,催化剂在1101cm-1处表现Cu/Zn/Al氧化物与HZSM-5分子筛之间相互作用的IR吸收峰强度与其催化活性间存在对应关系。XRD结果表明,并流法得到的催化剂前驱体中有铜锌同形取代现象,有利于催化剂活性的发挥。 相似文献
997.
998.
介绍一种微波高频段带通滤波器的设计方法,同时给出一个滤波器的设计实例和测试结果。利用制作简单的园棒内导体结构,采用梳状线与同轴腔相结合的方式,实现窄带带通滤波器,达到结构紧凑、性能优良、方便组件集成的使用效果。 相似文献
999.
在取得土料场土料物理力学性质参数的情况下,遵循碾压试验基本原理、方法及参数组合,进行了现场碾压试验,通过试验成果的分析,得出了大坝碾压试验结论,为大坝土方填筑提供了技术依据。 相似文献
1000.
An adaptive numerical dissipation control in a class of high order filter methods for compressible MHD equations is systematically discussed. The filter schemes consist of a divergence-free preserving high order spatial base scheme with a filter approach which can be divergence-free preserving depending on the type of filter operator being used, the method of applying the filter step, and the type of flow problem to be considered. Some of these filter variants provide a natural and efficient way for the minimization of the divergence of the magnetic field (∇·B) numerical error in the sense that commonly used divergence cleaning is not required. Numerical experiments presented emphasize the performance of the ∇·B numerical error. Many levels of grid refinement and detailed comparison of the filter methods with several commonly used compressible MHD shock-capturing schemes will be illustratedA condensed version appears in the Proceedings of the International Conference on High Performance Scientific Computing, March 10-14, 2003, Hanoi, Vietnam. This is a revised version of a longer internal report, Feb. 19, 2004. The longer internal report was published as a RIACS Technical Report TR03.10, July 2003, NASA Ames Research Center 相似文献