全文获取类型
收费全文 | 32659篇 |
免费 | 3175篇 |
国内免费 | 1627篇 |
专业分类
电工技术 | 2283篇 |
技术理论 | 2篇 |
综合类 | 2228篇 |
化学工业 | 5281篇 |
金属工艺 | 1688篇 |
机械仪表 | 2203篇 |
建筑科学 | 3176篇 |
矿业工程 | 892篇 |
能源动力 | 898篇 |
轻工业 | 2614篇 |
水利工程 | 650篇 |
石油天然气 | 1579篇 |
武器工业 | 264篇 |
无线电 | 3940篇 |
一般工业技术 | 3754篇 |
冶金工业 | 1246篇 |
原子能技术 | 429篇 |
自动化技术 | 4334篇 |
出版年
2024年 | 135篇 |
2023年 | 593篇 |
2022年 | 1167篇 |
2021年 | 1645篇 |
2020年 | 1146篇 |
2019年 | 924篇 |
2018年 | 996篇 |
2017年 | 1132篇 |
2016年 | 1038篇 |
2015年 | 1309篇 |
2014年 | 1694篇 |
2013年 | 1942篇 |
2012年 | 2212篇 |
2011年 | 2326篇 |
2010年 | 2164篇 |
2009年 | 2032篇 |
2008年 | 1857篇 |
2007年 | 1780篇 |
2006年 | 1699篇 |
2005年 | 1454篇 |
2004年 | 972篇 |
2003年 | 900篇 |
2002年 | 863篇 |
2001年 | 779篇 |
2000年 | 717篇 |
1999年 | 749篇 |
1998年 | 527篇 |
1997年 | 502篇 |
1996年 | 485篇 |
1995年 | 393篇 |
1994年 | 332篇 |
1993年 | 217篇 |
1992年 | 172篇 |
1991年 | 112篇 |
1990年 | 91篇 |
1989年 | 83篇 |
1988年 | 64篇 |
1987年 | 41篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1977年 | 4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 31 毫秒
91.
泥浆制备中工艺改造的研究 总被引:1,自引:0,他引:1
根据室条件下粉磨试验结果,发现球磨过程中筛上料变化存在的突变范围,提出两次加料一次加水可改变泥浆颗粒分布,并找出适宜的加料种类与时间。另外给予测粒度分布提供了宝贵的试验基础数据。 相似文献
92.
93.
Kaloyeros A.E. Stan M.R. Arkles B. Geer R. Eisenbraun E.T. Raynolds J.E. Gadre A. Yongqiang Xue Ryan J. 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(11):2345-2352
Theoretical treatments forecast that bistable CMOS devices using electronic charge as a state variable will operate at their maximum thermal dissipation limit possibly as early as 2012. The problem is further compounded by increasing manufacturing challenges associated with the ever decreasing logic switch dimensions. These challenges require the development of new fabrication strategies that replace or complement current top-down lithography with bottom-up protocols using controlled self-assembly of nanomaterial building blocks. To answer some of these issues, this paper focuses on a new device paradigm consisting of an arene-metal-arene conformational switch, addressable through capacitive, inductive, or resonant-tunneling field coupling. The operating principle is based on voltage-tunable modulation in quantum electron transmission. The switch is open (off) when the metal ion is displaced to a position at a C-H bond on the arene ring due to an externally applied bias. Conversely, when the external bias is removed, the metal ion moves to an axis- symmetric position on the arene ring, and the switch is closed (on). The paper presents a summary of the architecture, operating principle, and advantages of the conformational switch, along with associated findings from proof-of-concept theoretical and experimental studies of its target specifications and performance. The paper also discusses opportunities and challenges related to the integration of conformational switches into hybrid CMOS-molecular and monolithic (all molecular) circuits. 相似文献
94.
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
95.
96.
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
97.
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
98.
袁永强 《有色冶金设计与研究》2003,24(3):39-42
结合工程实例,对采用传统的短木桩加新兴的土工合成材料——土工网及碎石垫层构成复合基础,处理河岸挡墙软基进行探讨,该方法在软土层厚度不超过4.0m的条件下,技术可靠,施工简单,工期短,造价低。 相似文献
99.
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
100.