全文获取类型
收费全文 | 30465篇 |
免费 | 2871篇 |
国内免费 | 1508篇 |
专业分类
电工技术 | 2026篇 |
技术理论 | 2篇 |
综合类 | 2090篇 |
化学工业 | 4956篇 |
金属工艺 | 1502篇 |
机械仪表 | 2019篇 |
建筑科学 | 3028篇 |
矿业工程 | 829篇 |
能源动力 | 829篇 |
轻工业 | 2512篇 |
水利工程 | 537篇 |
石油天然气 | 1362篇 |
武器工业 | 232篇 |
无线电 | 3726篇 |
一般工业技术 | 3555篇 |
冶金工业 | 1200篇 |
原子能技术 | 401篇 |
自动化技术 | 4038篇 |
出版年
2024年 | 153篇 |
2023年 | 576篇 |
2022年 | 1065篇 |
2021年 | 1449篇 |
2020年 | 1051篇 |
2019年 | 868篇 |
2018年 | 930篇 |
2017年 | 1043篇 |
2016年 | 970篇 |
2015年 | 1192篇 |
2014年 | 1573篇 |
2013年 | 1797篇 |
2012年 | 2020篇 |
2011年 | 2153篇 |
2010年 | 2008篇 |
2009年 | 1883篇 |
2008年 | 1742篇 |
2007年 | 1649篇 |
2006年 | 1585篇 |
2005年 | 1348篇 |
2004年 | 899篇 |
2003年 | 836篇 |
2002年 | 824篇 |
2001年 | 745篇 |
2000年 | 675篇 |
1999年 | 704篇 |
1998年 | 492篇 |
1997年 | 475篇 |
1996年 | 465篇 |
1995年 | 373篇 |
1994年 | 314篇 |
1993年 | 206篇 |
1992年 | 160篇 |
1991年 | 112篇 |
1990年 | 83篇 |
1989年 | 82篇 |
1988年 | 63篇 |
1987年 | 45篇 |
1986年 | 36篇 |
1985年 | 24篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 11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 15 毫秒
81.
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
82.
83.
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
84.
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
85.
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
86.
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
87.
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
88.
SJ Mihic Q Ye MJ Wick VV Koltchine MD Krasowski SE Finn MP Mascia CF Valenzuela KK Hanson EP Greenblatt RA Harris NL Harrison 《Canadian Metallurgical Quarterly》1997,389(6649):385-389
Volatile anaesthetics have historically been considered to act in a nonspecific manner on the central nervous system. More recent studies, however, have revealed that the receptors for inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine are sensitive to clinically relevant concentrations of inhaled anaesthetics. The function of GABA(A) and glycine receptors is enhanced by a number of anaesthetics and alcohols, whereas activity of the related GABA rho1 receptor is reduced. We have used this difference in pharmacology to investigate the molecular basis for modulation of these receptors by anaesthetics and alcohols. By using chimaeric receptor constructs, we have identified a region of 45 amino-acid residues that is both necessary and sufficient for the enhancement of receptor function. Within this region, two specific amino-acid residues in transmembrane domains 2 and 3 are critical for allosteric modulation of both GABA(A) and glycine receptors by alcohols and two volatile anaesthetics. These observations support the idea that anaesthetics exert a specific effect on these ion-channel proteins, and allow for the future testing of specific hypotheses of the action of anaesthetics. 相似文献
89.
90.
This paper first presents an unified discussion of real and complex boundary integral equations (BIEs) for two-dimensional potential problems. Relationships between real and complex formulations, for both usual and hypersingular BIEs, are discussed. Potential problems in bounded as well as in unbounded domains are of concern in this work. Quantities of particular interest are derivatives of the primary field that exhibit discontinuities across corners, as well as stress intensity factors at the tips of mode III cracks. The latter problem in an application of a recent generalization of the well-known Plemelj-Sokhotsky formulae. Numerical implementations and results for interior problems in bounded domains, as well as for crack problems in unbounded domains, are presented and discussed.C. Y. Hui is supported by the Material Science Center at Cornell University, which is funded by the National Science Foundation (DMR-MRL program). S Mukherjee acknowledges partial support from NSF grant number ECS-9321508 to Cornell University. 相似文献