全文获取类型
收费全文 | 535466篇 |
免费 | 103359篇 |
国内免费 | 73017篇 |
专业分类
电工技术 | 57881篇 |
技术理论 | 1篇 |
综合类 | 60970篇 |
化学工业 | 65844篇 |
金属工艺 | 49093篇 |
机械仪表 | 32182篇 |
建筑科学 | 38789篇 |
矿业工程 | 28073篇 |
能源动力 | 16748篇 |
轻工业 | 59967篇 |
水利工程 | 18847篇 |
石油天然气 | 24658篇 |
武器工业 | 8498篇 |
无线电 | 64462篇 |
一般工业技术 | 55684篇 |
冶金工业 | 22044篇 |
原子能技术 | 7719篇 |
自动化技术 | 100382篇 |
出版年
2024年 | 4728篇 |
2023年 | 10133篇 |
2022年 | 19163篇 |
2021年 | 23879篇 |
2020年 | 20889篇 |
2019年 | 24342篇 |
2018年 | 26155篇 |
2017年 | 29440篇 |
2016年 | 27814篇 |
2015年 | 33207篇 |
2014年 | 36464篇 |
2013年 | 39657篇 |
2012年 | 45557篇 |
2011年 | 43959篇 |
2010年 | 41298篇 |
2009年 | 37280篇 |
2008年 | 36890篇 |
2007年 | 35625篇 |
2006年 | 30462篇 |
2005年 | 25443篇 |
2004年 | 22123篇 |
2003年 | 15793篇 |
2002年 | 14986篇 |
2001年 | 13368篇 |
2000年 | 11118篇 |
1999年 | 6805篇 |
1998年 | 4558篇 |
1997年 | 4030篇 |
1996年 | 3827篇 |
1995年 | 3776篇 |
1994年 | 3065篇 |
1993年 | 2836篇 |
1992年 | 2764篇 |
1991年 | 2010篇 |
1990年 | 1591篇 |
1989年 | 1502篇 |
1988年 | 1125篇 |
1987年 | 379篇 |
1986年 | 327篇 |
1985年 | 229篇 |
1984年 | 169篇 |
1983年 | 135篇 |
1982年 | 185篇 |
1981年 | 215篇 |
1980年 | 217篇 |
1979年 | 130篇 |
1976年 | 227篇 |
1975年 | 203篇 |
1972年 | 235篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
J. Va'vra J. Kadyk J. Wise P. Coyle 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,370(2-3):352-366
Among the photocathodes used for particle identification based on the Cherenkov Ring Imaging technique, the TMAE molecule is still the best in terms of quantum efficiency. Despite the fact that TMAE gaseous photocathodes have already been used in a number of large experiments, one still seeks answers to many detailed questions. We present a systematic study of gaseous photocathodes based on TMAE mixed with helium, hydrocarbon and CF4-based gases at normal pressure. The study includes a measurement of the electron drift velocity, gas quenching properties, single electron pulse height spectra and anode wire aging. The paper makes recommendations for carrier gas mixtures to obtain the best quenching, and suggests how to manage TMAE wire aging. This study was motivated by a specific particle identification detector proposal, the Fast Drift CRID proposed for the B-factory at SLAC. 相似文献
12.
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone. 相似文献
13.
14.
Tatsuya Hanaoka Hisashi Ishitani Ryuji Matsuhashi Yoshikuni Yoshida 《Applied Energy》2002,72(3-4):705-721
The objective of this study is to evaluate the potential for recovering fluorocarbons as measures for the abatement of global warming. In this study, we focused on the three different kinds of fluorocarbons: CFCs, HCFCs and HFCs, and targeted refrigerant use because of the availability of relevant data. We first estimated future fluorocarbon emissions from the targeted appliances; we next compared those emissions in the units of CO2 equivalent to the level of CO2 emissions in 1990 from a quantitative point of view. As the result of this study, it was found that fluorocarbon emissions in 1999 and 2010 would be equal to approximately 7 and 3% of the level of CO2 emissions in 1990 respectively. Moreover, if we implement a 100% recovery rate in every recovery route, we can reduce a large amount of emissions which correspond to approximately 2–5% of the level of CO2 emissions in 1990, even if we take into account the energy-related CO2 emissions by the transportation and decomposition of fluorocarbons. 相似文献
15.
16.
化学镀非晶态Ni—B合金的研究 总被引:1,自引:0,他引:1
本文通过化学镀方法在铜和钢上沉积非晶态Ni-B合金。着重讨论了还原剂浓度、络合剂浓度对化学镀沉积速率的影响;分析了它的耐蚀原因和其显微硬度随退火温度的变化情况并就其应用和发展略作说明。 相似文献
17.
Multi-valued and universal binary neurons (MVN and UBN) are the neural processing elements with the complex-valued weights and high functionality. It is possible to implement an arbitrary mapping described by partially defined multiple-valued function on the single MVN. An arbitrary mapping described by partially defined or fully defined Boolean function, which can be non-threshold, may be implemented on the single UBN. The quickly converging learning algorithms exist for both types of neurons. Such features of the MVN and UBN may be used for solving the different problems. One of the most successful applications of the MVN and UBN is their usage as basic neurons in the Cellular Neural Networks (CNN). It opens the new effective opportunities in nonlinear image filtering and its applications to noise reduction, edge detection and solving of the super resolution problem. A number of experimental results are presented to illustrate the performance of the proposed algorithms.An erratum to this article can be found at 相似文献
18.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
19.
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
20.
Inaki Arrazola Agn s Plainfoss Henri Prade Claudette Testemale 《Information Systems》1989,14(6):487-492
This paper presents different approaches which enable a data base management system to obtain a plausible fuzzy estimate for an attribute value of an item for which the information is not explicitly stored in the data base. This can be made either by a kind of analogical reasoning from information about particular items or by means of expert rules which specify the (fuzzy) sets of possible values of the attribute under consideration, for various classes of items. Another kind of expert rules enables the system to compute an estimate from the attribute value of another item provided that, in other respects, this latter item sufficiently resembles the item, the value of which we are interested in; then these expert rules are used either for controlling the analogical reasoning process or for enlarging the scope of application of the first kind of expert rules. The different approaches are discussed in the framework of possibility theory. 相似文献