全文获取类型
收费全文 | 5189篇 |
免费 | 42篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 45篇 |
综合类 | 3篇 |
化学工业 | 522篇 |
金属工艺 | 36篇 |
机械仪表 | 59篇 |
建筑科学 | 139篇 |
矿业工程 | 4篇 |
能源动力 | 58篇 |
轻工业 | 216篇 |
水利工程 | 28篇 |
石油天然气 | 2篇 |
无线电 | 359篇 |
一般工业技术 | 480篇 |
冶金工业 | 2893篇 |
原子能技术 | 35篇 |
自动化技术 | 353篇 |
出版年
2021年 | 31篇 |
2019年 | 20篇 |
2018年 | 39篇 |
2017年 | 34篇 |
2016年 | 31篇 |
2015年 | 18篇 |
2014年 | 46篇 |
2013年 | 161篇 |
2012年 | 67篇 |
2011年 | 99篇 |
2010年 | 83篇 |
2009年 | 81篇 |
2008年 | 100篇 |
2007年 | 93篇 |
2006年 | 78篇 |
2005年 | 89篇 |
2004年 | 75篇 |
2003年 | 77篇 |
2002年 | 68篇 |
2001年 | 71篇 |
2000年 | 65篇 |
1999年 | 133篇 |
1998年 | 827篇 |
1997年 | 459篇 |
1996年 | 357篇 |
1995年 | 238篇 |
1994年 | 185篇 |
1993年 | 211篇 |
1992年 | 79篇 |
1991年 | 66篇 |
1990年 | 79篇 |
1989年 | 87篇 |
1988年 | 70篇 |
1987年 | 77篇 |
1986年 | 71篇 |
1985年 | 70篇 |
1984年 | 42篇 |
1983年 | 40篇 |
1982年 | 43篇 |
1981年 | 52篇 |
1980年 | 54篇 |
1979年 | 35篇 |
1978年 | 28篇 |
1977年 | 107篇 |
1976年 | 176篇 |
1975年 | 27篇 |
1974年 | 26篇 |
1973年 | 19篇 |
1972年 | 19篇 |
1971年 | 18篇 |
排序方式: 共有5232条查询结果,搜索用时 15 毫秒
1.
2.
Jokerst N.M. Gaylord T.K. Glytsis E. Brooke M.A. Cho S. Nonaka T. Suzuki T. Geddis D.L. Shin J. Villalaz R. Hall J. Chellapa A. Vrazel M. 《Advanced Packaging, IEEE Transactions on》2004,27(2):376-385
This paper explores design options for planar optical interconnections integrated onto boards, discusses fabrication options for both beam turning and embedded interconnections to optoelectronic devices, describes integration processes for creating embedded planar optical interconnections, and discusses measurement results for a number of integration schemes that have been demonstrated by the authors. In the area of optical interconnections with beams coupled to and from the board, the topics covered include integrated metal-coated polymer mirrors and volume holographic gratings for optical beam turning perpendicular to the board. Optical interconnections that utilize active thin film (approximately 1-5 /spl mu/m thick) optoelectronic components embedded in the board are also discussed, using both Si and high temperature FR-4 substrates. Both direct and evanescent coupling of optical signals into and out of the waveguide are discussed using embedded optical lasers and photodetectors. 相似文献
3.
I. Tsukanov M. Hall 《International journal for numerical methods in engineering》2003,56(13):1949-1972
In this paper we discuss the data structure and algorithms for the direct application of generalized Leibnitz rules to the numerical computation of partial derivatives in forward mode. The proposed data structure provides constant time access to the partial derivatives, which accelerates the automatic differentiation computations. The interaction among elements of the data structure is explained by several numerical examples. The paper contains analysis of the developed data structure and algorithms. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
5.
6.
Degenerate oligonucleotide primers were used in a polymerase chain reaction (PCR) to amplify a region of the recA sequence of Streptococcus gordonii Challis. The resulting PCR fragment was cloned into the suicide vector pAM6199 and introduced into strain Challis, giving rise to recombination-deficient strains in which the recA gene was specifically inactivated. 相似文献
7.
Maribel Plascencia‐Jatomea Miguel A Olvera‐Novoa Jos Luis Arredondo‐Figueroa George M Hall Keiko Shirai 《Journal of the science of food and agriculture》2002,82(7):753-759
This study provides information on the use of shrimp head silage protein hydrolysate (SPH) as an alternative protein source for tilapia feeding. Six diets (28% protein, 12% lipid) were prepared where fishmeal protein was replaced at levels of 0 (control), 10, 15, 20, 25 and 30% with the hydrolysate. The diets were supplied to Nile tilapia fry (338 mg initial weight) stocked in plastic recirculating 20 l tanks (10 animals per tank), with three replicates per treatment. After an 8 week experimental period, fish fed the diets containing 10 and 15% SPH showed significantly better performance in terms of final body weight, weight gain (%), mean daily weight gain (mg day?1), specific growth ratio and feed conversion ratio than those fed the control diet (fishmeal as protein source) and higher‐SPH diets. It is concluded that shrimp head hydrolysate is a promising alternative protein source for tilapia feeding, improving growth ratio at dietary inclusion levels as high as 15%. In addition, the diets with added shrimp silage protein were well accepted by the fish, which avidly consumed the feed during the experiment. © 2002 Society of Chemical Industry 相似文献
8.
9.
Tan J.C. Crossley P.A. McLaren P.G. Hall I. Farrell J. Gale P. 《Power Delivery, IEEE Transactions on》2002,17(1):68-74
This paper describes a sequential tripping strategy used in a wide area back-up protection expert system (BPES) to combat situations in which protection relays have maloperated or information is missing. The BPES is an innovative back-up protection scheme designed to prevent the occurrence of widespread blackouts. The BPES evaluates the certainty that transmission lines are likely to be affected by the fault and uses a sequential tripping strategy to isolate the fault if a firm decision is not available due to maloperated relays and/or missing information. The mode of analysis and the sequential tripping strategy ensures that the BPES will clear a fault at minimum risk to the network. An example is included to demonstrate how the certainty factor based sequential tripping strategy is employed by the BPES to clear a fault which occurred on the South Western part of the UK National Grid System 相似文献
10.
T. A. Hall 《Journal of microscopy》1991,164(1):67-79
When a microregion in a thin section of frozen-dried and embedded tissue is analysed by the conventional electron-probe X-ray continuum-normalization method, the measured quantity is in mmol of element per kg of embedded specimen. As each microregion contains an unknown amount of embedding medium, this quantity generally lies indeterminately somewhere within the wide range between mmol of element per kg of hydrated tissue and mmol of element per kg of dehydrated tissue. However, if a ‘tag’ element is incorporated in the embedding medium, the contribution of the medium to the local continuum count in each probed field should be measurable, and the X-ray data may then unambiguously yield mmol of element per kg of dehydrated tissue. This result should not be affected by shrinkage on freeze-drying or by incomplete replacement of water by embedding medium. The same X-ray data can additionally provide estimates of mmol of element per unit volume, mmol of element per kg of hydrated tissue and local dry-mass fraction. However, these estimates are subject to errors due to tissue shrinkage, incomplete replacement of water and beam damage. 相似文献