全文获取类型
收费全文 | 38344篇 |
免费 | 3928篇 |
国内免费 | 2092篇 |
专业分类
电工技术 | 2740篇 |
技术理论 | 3篇 |
综合类 | 2780篇 |
化学工业 | 6151篇 |
金属工艺 | 1917篇 |
机械仪表 | 2469篇 |
建筑科学 | 3621篇 |
矿业工程 | 1100篇 |
能源动力 | 1086篇 |
轻工业 | 3240篇 |
水利工程 | 688篇 |
石油天然气 | 1769篇 |
武器工业 | 347篇 |
无线电 | 4712篇 |
一般工业技术 | 4379篇 |
冶金工业 | 1480篇 |
原子能技术 | 530篇 |
自动化技术 | 5352篇 |
出版年
2024年 | 241篇 |
2023年 | 844篇 |
2022年 | 1533篇 |
2021年 | 2082篇 |
2020年 | 1521篇 |
2019年 | 1228篇 |
2018年 | 1311篇 |
2017年 | 1453篇 |
2016年 | 1312篇 |
2015年 | 1635篇 |
2014年 | 2121篇 |
2013年 | 2369篇 |
2012年 | 2648篇 |
2011年 | 2703篇 |
2010年 | 2479篇 |
2009年 | 2295篇 |
2008年 | 2121篇 |
2007年 | 2000篇 |
2006年 | 1916篇 |
2005年 | 1570篇 |
2004年 | 1054篇 |
2003年 | 1007篇 |
2002年 | 992篇 |
2001年 | 883篇 |
2000年 | 797篇 |
1999年 | 778篇 |
1998年 | 557篇 |
1997年 | 521篇 |
1996年 | 515篇 |
1995年 | 416篇 |
1994年 | 348篇 |
1993年 | 238篇 |
1992年 | 181篇 |
1991年 | 124篇 |
1990年 | 93篇 |
1989年 | 92篇 |
1988年 | 68篇 |
1987年 | 45篇 |
1986年 | 40篇 |
1985年 | 31篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1977年 | 6篇 |
1962年 | 42篇 |
1961年 | 39篇 |
1960年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A model of a human neural knowledge processing system is presented that suggests the following. First, an entity in the outside world lends to be locally encoded in neural networks so that the conceptual information structure is mirrored in its physical implementation. Second, the knowledge of problem solving is implemented in a quite implicit way in the internal structure of the neural network (a functional group of associated hidden neurons and their connections to entity neurons) not in individual neurons or connections. Third, the knowledge system is organized and implemented in a modular fashion in neural networks according to the local specialization of problem solving where a module of neural network implements an inter-related group of knowledge such as a schema, and different modules have similar processing mechanisms, but differ in their input and output patterns. A neural network module can be tuned just as a schema structure can be adapted for changing environments. Three experiments were conducted to try to validate the suggested cognitive engineering based knowledge structure in neural networks through computer simulation. The experiments, which were based on a task of modulo arithmetic, provided some insights into the plausibility of the suggested model of a neural knowledge processing system. 相似文献
92.
Bai-Huan Xu Dong-Ya Sun Cong Ding Xue-Zhong Liu Zi-Jing Xiao 《Materials Research Bulletin》2007,42(9):1633-1639
Layered nanocomposite PEG/WS2, intercalating oligomeric poly(ethylene glycol) (PEG6000) into the tungsten disulfide host galleries, was synthesized using the exfoliation-adsorption technique. X-ray diffraction revealed that the intercalated oligomer within the host galleries is in a double-layer arrangement with an interlayer expansion of about 8.8 Å. The optimum conditions were explored to prepare the single-phase product with a composition of Li0.12(PEG)1.51WS2. Thermal analyses suggested that the resulting material shows good thermal stability, with the decomposition of the interacted oligomeric chains within the disulfide galleries occurring at around 258 °C. Despite high conductivity of the host material, those of the PEG/WS2 nanocomposite were found to be high in the order of 1 × 10−2 S cm−1 at ambient temperature, resulted from the host guest-host charge transfers. 相似文献
93.
94.
介绍3J特级防火卷帘的各种重要功能特点,讨论其实用性与易用性以及推广该产品的必要性与可行性。 相似文献
95.
Huiping Hu Qiyuan Chen Zhoulan Yin Pingmin Zhang Lusheng Ye 《Metallurgical and Materials Transactions A》2003,34(13):793-797
The thermal decompositions of mechanically activated and nonactivated galenas were studied by thermogravimetry analysis (TGA)
at the heating rate of 10 K min−1 in argon. Results indicate that the initial temperature of thermal decomposition (abbreviated as T
di) in the TGA curves for different galenas decreases gradually with increased grinding time. The specific granulometric surface
area (S
G), the structural disorder, and the content of elemental sulfur of mechanically activated galenas were analyzed by an X-ray
diffraction (XRD) laser particle-size analyzer, XRD analysis, and the gravimetric method, respectively, which shows that the
specific granulometric surface area of mechanically activated galenas remains almost constant after a certain grinding time,
but the lattice distortions (ε) rise, the crystallite sizes (D) decrease, and the elemental sulfur contents of mechanically activated galenas increase with increased grinding time. The
results imply that the decrease of the initial temperature of thermal decomposition in the TGA curves for mechanically activated
galenas is mainly caused by the increase of lattice distortions, and the formation of new dangling bonds resulted from the
production of elemental sulfur of mechanically activated galenas with increased grinding time. Finally, the differences in
the thermal-decomposition reactivity between nonactivated and mechanically activated galenas were also discussed. 相似文献
96.
Fred Y. Ye 《Scientometrics》2007,71(3):407-413
There exists a quantitative relationship, which can be expressed as G=kF(lgP)N, where G is per capita GDP, F gross expenditure
on R&D as % of GDP, P patent applications, N Internet users per 10,000 inhabitants, and k a constant ranging from 0.4 to 1.2
in most countries. The mechanism of the relationship is explained in the paper. 相似文献
97.
本文在研究人类设计技能模型的基础上,建立暖通空调广义设计过程模式,提出暖通空调广义设计过程及其CAD系统的信息模型,并以此为基础建立了暖通空调广义CAD系统的框架。 相似文献
98.
纳米技术在中药开发中的应用 总被引:7,自引:0,他引:7
本文综述了纳米科技与中药制剂相结合的发展,阐述了纳米中药的概念、特性,介绍了纳米中药的制备技术,另外探讨了收集纳米粒子的方法,最后,着重展望了纳米技术在中药制剂中广泛的应用前景。 相似文献
99.
根据Requisition的词义和询价、招标、订购文件的意义,建议将不能准确表达意思的中文译词“请购”改成“询购”。 相似文献
100.
Parity space approach and H2 approach are two important fault detection approaches. This paper studies the relationship between these two approaches, which reveals frequency domain characteristics of the optimal solution of the parity space approach on the one side and provides a numerical solution of the H2-optimal design of residual generators on the other side. 相似文献