全文获取类型
收费全文 | 19124篇 |
免费 | 321篇 |
国内免费 | 36篇 |
专业分类
电工技术 | 222篇 |
综合类 | 18篇 |
化学工业 | 2162篇 |
金属工艺 | 292篇 |
机械仪表 | 341篇 |
建筑科学 | 561篇 |
矿业工程 | 24篇 |
能源动力 | 274篇 |
轻工业 | 1791篇 |
水利工程 | 121篇 |
石油天然气 | 32篇 |
无线电 | 1541篇 |
一般工业技术 | 2162篇 |
冶金工业 | 7869篇 |
原子能技术 | 176篇 |
自动化技术 | 1895篇 |
出版年
2023年 | 49篇 |
2022年 | 134篇 |
2021年 | 238篇 |
2020年 | 127篇 |
2019年 | 194篇 |
2018年 | 235篇 |
2017年 | 223篇 |
2016年 | 266篇 |
2015年 | 160篇 |
2014年 | 310篇 |
2013年 | 668篇 |
2012年 | 512篇 |
2011年 | 663篇 |
2010年 | 509篇 |
2009年 | 507篇 |
2008年 | 584篇 |
2007年 | 574篇 |
2006年 | 469篇 |
2005年 | 469篇 |
2004年 | 375篇 |
2003年 | 384篇 |
2002年 | 341篇 |
2001年 | 334篇 |
2000年 | 320篇 |
1999年 | 489篇 |
1998年 | 2474篇 |
1997年 | 1547篇 |
1996年 | 1007篇 |
1995年 | 660篇 |
1994年 | 547篇 |
1993年 | 598篇 |
1992年 | 214篇 |
1991年 | 191篇 |
1990年 | 219篇 |
1989年 | 214篇 |
1988年 | 220篇 |
1987年 | 168篇 |
1986年 | 172篇 |
1985年 | 219篇 |
1984年 | 126篇 |
1983年 | 111篇 |
1982年 | 102篇 |
1981年 | 132篇 |
1980年 | 132篇 |
1979年 | 97篇 |
1978年 | 57篇 |
1977年 | 239篇 |
1976年 | 414篇 |
1975年 | 65篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
RM Martín‐Aranda E Ortega‐Cantero ML Rojas‐Cervantes MA Vicente‐Rodríguez MA Baares‐Muoz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(2):234-238
α,β‐Unsaturated nitriles have been synthesized by Knoevenagel condensation of a carbonylic compound with malononitrile, assisted by sonochemical irradiation. Two alkaline‐promoted clays (Li+‐ and Cs+‐exchanged saponites) have been employed as catalysts. The influence of the carbonylic compound (benzaldehyde or cyclohexanone) and the use of a solvent on the catalytic activity have been studied. Remarkable increase in the conversion values has been found when the reaction is activated by ultrasound, as compared with the thermal activation. In this green, solvent‐free procedure, α,β‐unsaturated nitriles have been produced in very high yields (97%) when the Cs+‐saponite is used as catalyst. Copyright © 2004 Society of Chemical Industry 相似文献
52.
Wisse M. Feliksdal G. Van Frankkenhuyzen J. Moyer B. 《Robotics & Automation Magazine, IEEE》2007,14(2):52-62
In this article, we presented our passive-based biped Denise. Using only two foot contact switches as sensors and simple on/off pneumatic muscle action, it walks at 0.4 m/s and can handle floor disturbances up to 6 mm (leg length is 0.7 m). Its simplicity, efficiency, and die natural look of its motions make it a promising lead for the development of commercially viable humanoid robots. The aim of this article is to provide other researchers enough details so that they can reproduce the work or use it as a basis for future research. 相似文献
53.
An adaptable die is one that not only produces the correct geometrical shape, but also is designed through an adaptable method to impart other desirable properties to the product or process. In this first part of a series of papers, six kinematically admissible velocity fields are developed for use in upper bound models for axisymmetric extrusion through various dies, including extrusion through adaptable dies. Three base velocity fields are presented:
- (1) assuming proportional angles in the deformation zone,
- (2) assuming proportional areas in the deformation zone, or
- (3) assuming proportional distances from the centerline in the deformation zone.
54.
On-body communications around the human torso are considered, using ultra-wideband transmissions. The velocity of the diffracted wave propagating around the body is extracted from frequency- domain spatial correlation analyses. 相似文献
55.
C. L. J. A. Verbraak J. Van Dam A. K. Van Der Vegt 《Polymer Engineering and Science》1985,25(7):431-433
Orientation-induced crystallization of crystallizable polymer melts can occur, under certain conditions, during flow through converging channels. Attempts have been made to achieve this phenomenon in a two-phase system, i.e., during simultaneous extrusion of a continuous concentric core of polypropylene within a polystyrene matrix through a conical duct. On one occasion, using Carlona P SY6100 (MFI = 11.0) with Hostyren N2000-V-01 (MFI = 25.0), a highly oriented polypropylene thread with a modulus of 14.6 GPa and a melting point of 178°C was extruded at a die temperature of approximately 170°C and a pressure lower than 40 MPa. It is, in principle, possible to form highly oriented, fiber-like structures as reinforcing elements in a polymer matrix. 相似文献
56.
RM Bionta G Blewitt CB Bratton D Casper A Ciocio R Claus M Crouch ST Dye S Errede GW Foster W Gajewski KS Ganezer M Goldhaber TJ Haines TW Jones D Kielczewska WR Kropp JG Learned JM LoSecco J Matthews HS Park LR Price F Reines J Schulz S Seidel E Shumard D Sinclair HW Sobel JL Stone L Sulak R Svoboda G Thornton van der Velde JC C Wuest 《Canadian Metallurgical Quarterly》1987,36(1):30-36
57.
58.
Nagle H.T. Fritzemeier R.R. Van Well J.E. McNamer M.G. 《Industrial Electronics, IEEE Transactions on》1989,36(2):151-163
As the level of microprocessor complexity increases to several hundred thousand transistors for a single-chip machine, it is becoming very difficult to test commercially available designs to the level of fault coverage desired by some customers. In order to achieve near 100-percent coverage of single stuck-at faults, future microprocessors must be designed with special testing features (designed for testability). The authors describe the testing problem for microprocessors, including the various methods of generating test sets and their application by the user. A survey of the testability features of some of today's commercially available microprocessors is presented. Suggestions for testability features for future-generation microprocessors are also discussed 相似文献
59.
60.
Xiaoming Zhou Martin Jacobsson Henk Uijterwaal Piet Van Mieghem 《International Journal of Communication Systems》2008,21(6):643-663
Although packet delay and loss are two important parameters of the Internet performance, to the best of our knowledge, the evolution of large‐scale IPv6 delay and loss performance has previously not been studied. In this paper, we analyze more than 600 end‐to‐end IPv6 paths between about 26 testboxes of RIPE Network Coordination Centre over two years, and compare the delay and loss performance over time with their IPv4 counterparts. We present and discuss the measurement methodologies and show that IPv6 paths have a higher delay and loss than their IPv4 counterparts. The main reason for the worse performance stems from IPv6‐in‐IPv4 tunnels rather than from native IPv6 paths and such tunnels are still widely used today. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献