全文获取类型
收费全文 | 310642篇 |
免费 | 3579篇 |
国内免费 | 1913篇 |
专业分类
电工技术 | 6102篇 |
综合类 | 303篇 |
化学工业 | 45549篇 |
金属工艺 | 14051篇 |
机械仪表 | 9484篇 |
建筑科学 | 7753篇 |
矿业工程 | 965篇 |
能源动力 | 7912篇 |
轻工业 | 29816篇 |
水利工程 | 2620篇 |
石油天然气 | 3601篇 |
武器工业 | 44篇 |
无线电 | 37264篇 |
一般工业技术 | 59571篇 |
冶金工业 | 60915篇 |
原子能技术 | 6348篇 |
自动化技术 | 23836篇 |
出版年
2021年 | 2398篇 |
2019年 | 2154篇 |
2018年 | 3791篇 |
2017年 | 3691篇 |
2016年 | 4111篇 |
2015年 | 2797篇 |
2014年 | 4610篇 |
2013年 | 14122篇 |
2012年 | 7590篇 |
2011年 | 10311篇 |
2010年 | 8445篇 |
2009年 | 9341篇 |
2008年 | 9891篇 |
2007年 | 9943篇 |
2006年 | 8975篇 |
2005年 | 8219篇 |
2004年 | 7876篇 |
2003年 | 7824篇 |
2002年 | 7752篇 |
2001年 | 7829篇 |
2000年 | 7269篇 |
1999年 | 7774篇 |
1998年 | 19592篇 |
1997年 | 13768篇 |
1996年 | 10595篇 |
1995年 | 7975篇 |
1994年 | 7038篇 |
1993年 | 6911篇 |
1992年 | 4945篇 |
1991年 | 4944篇 |
1990年 | 4576篇 |
1989年 | 4467篇 |
1988年 | 4293篇 |
1987年 | 3722篇 |
1986年 | 3668篇 |
1985年 | 4257篇 |
1984年 | 3768篇 |
1983年 | 3444篇 |
1982年 | 3161篇 |
1981年 | 3208篇 |
1980年 | 3046篇 |
1979年 | 2867篇 |
1978年 | 2811篇 |
1977年 | 3528篇 |
1976年 | 5022篇 |
1975年 | 2454篇 |
1974年 | 2325篇 |
1973年 | 2285篇 |
1972年 | 1910篇 |
1971年 | 1731篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A method to estimate the acquisition time for the clock and data recovery (CDR) IC using the linear phase-locked loop (PLL) technique is proposed. Estimations using the method follow the measured acquisition time for the PLL with any loop parameters, which makes it possible to design the CDR IC for various targets. 相似文献
992.
The procedure of testing adhesives for glulam production depends in Europe on the kind of resin. For example the testing of phenol-formaldehyde resins (PF-resins) includes the boiling test method, because the curing rate of these resins show a significant correlation between the strength after boiling and the resistance to moisture influence. On the other hand this test method is commonly insufficient for testing other resins. The results of investigations of glulam based on different kinds of resins show that there is a possibility to substitute the boiling test by a short-time accelerated aging method (KZB-Test) which will offer the same differentiation. 相似文献
993.
Stress Intensity Factors for Complete Circumferential Surface Cracks in Thermally Shocked Pipes In the case of an emergency cooling of a reactor thermal stresses are generated in the pipes of the primary loop, which may be described conservatively as a thermal shock problem. In this paper complete interior circumferential surface cracks loaded by these thermal stresses are considered. By means of the weight function method stress intensity factors were calculated for this loading case. 相似文献
994.
Plastic deformation in a multifunctional Ti-Nb-Ta-Zr-O alloy 总被引:7,自引:0,他引:7
S. Kuramoto T. Furuta J. H. Hwang K. Nishino T. Saito 《Metallurgical and Materials Transactions A》2006,37(3):657-662
Mechanisms for plastic deformation in the newly developed Ti-24 at. pct (Ta + Nb + V)-(Zr,Hf)-O alloys (Gum Metal) were investigated
in relation to their unique properties. Transmission electron microscopy revealed that the microstructure after deformation
was characterized by highly distorted crystal images, which are accompanied by numerous “giant faults.” Such plastic behavior
implies that a large amount of elastic stain energy was stored discretely and hierarchically during cold working. Calculated
elastic constants of the Ti-X (Nb,Ta,Mo,V) binary systems predicted that Young’s modulus in 〈001〉 and shear moduli along some
directions including slip systems in a bcc crystal were extraordinary small. The low modulus not only well explains the highly
distorted microstructure observed in the cold-worked specimens, but also signifies that ideal shear strength of the developed
alloys is a very small value, which is close to the practical strength required for plastic deformation in the alloy. This
implies that the giant faults observed in the deformed specimen were formed without the aid of dislocation glide. 相似文献
995.
An applicability of quinone biomarker to the analysis of hillslope runoff was investigated. At first, quinone profiles of three streams as well as a hillslope runoff in a forested headwater catchment were compared. The quinone composition of hillslope runoff differed from others. Moreover, there were remarkable differences in quinone profile of hillslope runoff under different rainfall conditions. Then, the behavior of quinone biomarker during the increase and decrease of hillslope runoff after a rainfall event was examined. The fractional changes in Q-9 (H2), Q-10 (H2), Q-11, MK-6 and MK-10 suggested the effect of interflow. 相似文献
996.
997.
Self-knowledge is a concept that is present in several philosophies. In this article, we consider the issue of whether or not a learning algorithm can in some sense possess self-knowledge. The question is answered affirmatively. Self-learning inductive inference algorithms are taken to be those that learn programs for their own algorithms, in addition to other functions.
La connaissance de soi est un concept qui se retrouve dans plusieurs philosophies. Dans cet article, les auteurs s'interrogent à savoir si un algorithme d' apprentissage peut dans une certaine mesure posséder la connaissance de soi. lis apportent une reponse positive a cette question. Les algorithmes d'inference inductive autodidactes sont ceux qui font l'apprentissage de programmes pour leurs propres algorithmes, en plus d' autres fonctions. 相似文献
La connaissance de soi est un concept qui se retrouve dans plusieurs philosophies. Dans cet article, les auteurs s'interrogent à savoir si un algorithme d' apprentissage peut dans une certaine mesure posséder la connaissance de soi. lis apportent une reponse positive a cette question. Les algorithmes d'inference inductive autodidactes sont ceux qui font l'apprentissage de programmes pour leurs propres algorithmes, en plus d' autres fonctions. 相似文献
998.
A monolithic microwave frequency divider IC with an operating range of 1.4?5.3 GHz was developed and fabricated in a standard bipolar technology. The circuit operates on the principle of `regenerative frequency division?. Compared to the most popular divider concepts based on a master-slave D-flip-flop, an almost twice as high input frequency can be divided, provided that the same technology is used. A further advantage is the low power consumption. 相似文献
999.
G. Lucovsky J.G. Hong C.C. Fulton N.A. Stoute Y. Zou R.J. Nemanich D.E. Aspnes H. Ade D.G. Schlom 《Microelectronics Reliability》2005,45(5-6):827
This paper uses X-ray absorption spectroscopy to study the electronic structure of the high-k gate dielectrics including TM and RE oxides. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d* states, which define the optical band gap, Eg, and the conduction band offset energy with respect to crystalline Si, EB. Eg and EB scale with the atomic properties of the TM and RE atoms providing important insights for identification high-k dielectrics that meet performance targets for advanced CMOS devices. 相似文献
1000.
Based on the system of the equations of motion of an elastic medium with tetragonal anisotropy, a comparative analysis of the curves of inverse velocities and the elastic-wave fronts in one crystallographic plane of a cubically anisotropic body has been made with the use of sections of the surfaces of inverse velocities and wave surfaces. 相似文献