全文获取类型
收费全文 | 436784篇 |
免费 | 5640篇 |
国内免费 | 1545篇 |
专业分类
电工技术 | 7436篇 |
综合类 | 337篇 |
化学工业 | 65769篇 |
金属工艺 | 17765篇 |
机械仪表 | 13638篇 |
建筑科学 | 10286篇 |
矿业工程 | 2675篇 |
能源动力 | 11229篇 |
轻工业 | 38922篇 |
水利工程 | 4840篇 |
石油天然气 | 9480篇 |
武器工业 | 27篇 |
无线电 | 51646篇 |
一般工业技术 | 86853篇 |
冶金工业 | 77674篇 |
原子能技术 | 9580篇 |
自动化技术 | 35812篇 |
出版年
2021年 | 3693篇 |
2020年 | 2782篇 |
2019年 | 3492篇 |
2018年 | 5997篇 |
2017年 | 6038篇 |
2016年 | 6608篇 |
2015年 | 4173篇 |
2014年 | 7056篇 |
2013年 | 19686篇 |
2012年 | 11725篇 |
2011年 | 15915篇 |
2010年 | 12608篇 |
2009年 | 14082篇 |
2008年 | 14621篇 |
2007年 | 14555篇 |
2006年 | 13053篇 |
2005年 | 11893篇 |
2004年 | 11195篇 |
2003年 | 10992篇 |
2002年 | 10424篇 |
2001年 | 10859篇 |
2000年 | 9913篇 |
1999年 | 10415篇 |
1998年 | 25161篇 |
1997年 | 17614篇 |
1996年 | 13382篇 |
1995年 | 10183篇 |
1994年 | 8875篇 |
1993年 | 8992篇 |
1992年 | 6655篇 |
1991年 | 6386篇 |
1990年 | 6155篇 |
1989年 | 5977篇 |
1988年 | 5882篇 |
1987年 | 4906篇 |
1986年 | 4885篇 |
1985年 | 5772篇 |
1984年 | 5283篇 |
1983年 | 4910篇 |
1982年 | 4484篇 |
1981年 | 4504篇 |
1980年 | 4375篇 |
1979年 | 4267篇 |
1978年 | 4127篇 |
1977年 | 4528篇 |
1976年 | 5486篇 |
1975年 | 3679篇 |
1974年 | 3452篇 |
1973年 | 3622篇 |
1972年 | 3000篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
PCR-based procedures in detection and DNA-fingerprinting of Salmonella from samples of animal origin
A. del Cerro S. M. Soto E. Landeras M. A. Gonzlez-Hevia J. A. Guijarro M. C. Mendoza 《Food microbiology》2002,19(6):567
The usefulness of selected PCR-protocols for the detection of Salmonella in 117 samples of animal origin (17 raw minced meat, 27 raw chicken meat, 8 raw sausages, and 25 egg samples, as well as 18 poultry faecal, and caecal swabs samples) and DNA-fingerprinting typing is shown. To establish an accurate PCR-procedure for Salmonella detection the following parameters were evaluated: two pre-PCR concentration procedures, centrifugation and immunomagnetic separation (IMS) using Dynabeads anti- Salmonella; the specificity and sensitivity of 10 sets of primers; and different conditions of the amplification reaction. In light of the results obtained from the use of PCR-based procedures alone or in combination with conventional methods, the following findings can be underlined: First, IMS is more efficient than centrifugation in the recovery of Salmonella. Second, the selected IMS/PCR-detection protocol is less time-consuming (45 h) than the IMS/culture procedure (90 h), and a good concordance between them was found when the Kappa coefficient was calculated (0·87). Third, PCR-ribotyping technique showed a very low discrimination power, being able to differentiate only three profiles. Fourth, RAPD technique using specific primers supports previous works in which it was proposed as a simple and useful tool for discriminating isolates between and within serotypes. Fifth, The efficiency, rapidity, and flexibility of the PCR-protocols applied were high, and they can be performed using two PCR-programs and the same basic equipment. 相似文献
102.
103.
104.
Consideration was given to the decision making procedures based on the fuzzy messages of experts whose preferences on the set of collective decisions can also be fuzzy. 相似文献
105.
I. N. Polandov V. K. Novik O. K. Gulish B. P. Bogomolov V. B. Morozov 《Measurement Techniques》1989,32(9):888-890
Translated from Izmeritel'naya Tekhnika, No. 9, pp. 34–35, September, 1989. 相似文献
106.
R. Sankarasubramanian C. S. Jog T. A. Abinandanan 《Metallurgical and Materials Transactions A》2002,33(4):1083-1090
We examine the symmetry-breaking transitions in equilibrium shapes of coherent precipitates in two-dimensional (2-D) systems
under a plane-strain condition with the principal misfit strain components ε*
xx
and ε*
yy
. For systems with cubic elastic moduli, we first show all the shape transitions associated with different values of t=ε*
yy
/ε*
xx
. We also characterize each of these transitions, by studying its dependence on elastic anisotropy and inhomogeneity. For
systems with dilatational misfit (t=1) and those with pure shear misfit (t=−1), the transition is from an equiaxed shape to an elongated shape, resulting in a break in rotational symmetry. For systems
with nondilatational misfit (−1<t<1; t ≠ 0), the transition involves a break in mirror symmetries normal to the x- and y-axes. The transition is continuous in all cases, except when 0<t<1. For systems which allow an invariant line (−1≤t<0), the critical size increases with an increase in the particle stiffness. However, for systems which do not allow an invariant
line (0<t≤1), the critical size first decreases, reaches a minimum, and then starts increasing with increasing particle stiffness;
moreover, the transition is also forbidden when the particle stiffness is greater than a critical value. 相似文献
107.
Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples. 相似文献
108.
109.
110.
V. L. Ozol' L. F. Kandyba N. T. Bychenkov L. A. Zbarskii B. E. Koropov 《Metallurgist》1989,33(8):156-156
Lenin Dnepropetrovsk Pipe Plant. Translated from Metallurg, No. 8, p. 39, August, 1989. 相似文献