全文获取类型
收费全文 | 18566篇 |
免费 | 477篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 245篇 |
综合类 | 9篇 |
化学工业 | 3616篇 |
金属工艺 | 284篇 |
机械仪表 | 319篇 |
建筑科学 | 1133篇 |
矿业工程 | 109篇 |
能源动力 | 515篇 |
轻工业 | 1412篇 |
水利工程 | 158篇 |
石油天然气 | 194篇 |
武器工业 | 1篇 |
无线电 | 1117篇 |
一般工业技术 | 2936篇 |
冶金工业 | 4367篇 |
原子能技术 | 165篇 |
自动化技术 | 2481篇 |
出版年
2022年 | 140篇 |
2021年 | 222篇 |
2020年 | 171篇 |
2019年 | 227篇 |
2018年 | 269篇 |
2017年 | 266篇 |
2016年 | 321篇 |
2015年 | 242篇 |
2014年 | 387篇 |
2013年 | 1119篇 |
2012年 | 668篇 |
2011年 | 880篇 |
2010年 | 681篇 |
2009年 | 667篇 |
2008年 | 864篇 |
2007年 | 881篇 |
2006年 | 695篇 |
2005年 | 728篇 |
2004年 | 573篇 |
2003年 | 578篇 |
2002年 | 517篇 |
2001年 | 338篇 |
2000年 | 312篇 |
1999年 | 315篇 |
1998年 | 365篇 |
1997年 | 335篇 |
1996年 | 318篇 |
1995年 | 343篇 |
1994年 | 277篇 |
1993年 | 319篇 |
1992年 | 281篇 |
1991年 | 173篇 |
1990年 | 243篇 |
1989年 | 295篇 |
1988年 | 213篇 |
1987年 | 220篇 |
1986年 | 219篇 |
1985年 | 271篇 |
1984年 | 265篇 |
1983年 | 232篇 |
1982年 | 222篇 |
1981年 | 217篇 |
1980年 | 175篇 |
1979年 | 191篇 |
1978年 | 182篇 |
1977年 | 181篇 |
1976年 | 159篇 |
1975年 | 184篇 |
1974年 | 171篇 |
1973年 | 137篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
Ready-to-drinks (RTDs) are composed of an alcoholic component and a soft-drink base and are primarily consumed by a youth market. The authors explored whether liking and experience with an RTD soft-drink base predicts liking for the RTD. Participants (N=350) from ages 12 to 30 years sampled 3 RTDs and their respective soft-drink and alcoholic components. For milk- and fruit-based RTDs, liking for and familiarity with their soft-drink base was the best predictor of liking for and familiarity with the RTD itself. For the Coke-based RTD, familiarity with and liking for bourbon best predicted familiarity with and liking for the RTD. All of these effects were consistent across blind and nonblind testing. The authors' results suggest that where there is perceptual similarity between the RTD and its soft-drink base, these beverages may provide an easy transition into alcohol consumption for novice drinkers. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
24.
This paper describes the elastic response of a block sample of compressible Chicago glacial clay under a variety of stresses and its relationship with the deformation characteristics at relatively large strains. The elastic shear stiffness was obtained from bender element tests during consolidation and shearing in drained triaxial stress probe tests. An empirical correlation was established based on the elastic shear stiffness in a preyield condition. By comparing the empirical correlation with the measured elastic shear stiffness in the stress region during probing, the changes of elastic shear stiffness were investigated. The departure of elastic shear stiffness from values computed by the empirical relation based on K0 loading directly relates to the yielding characteristics of the clay. The large-scale change of soil structure at yielding alters the well-established relationship between the elastic shear stiffness and stresses in the preyield condition. The mechanical yielding response of clays can be detected based on the systematic analysis of the elastic shear wave velocities. 相似文献
25.
An efficient, convenient and quantitative method for characterising polyester end-groups is described. We have found that trichloroacetyl isocyanate (TAI) reacts rapidly and quantitatively with both carboxyl [C(O)OH] and hydroxyl (OH) chain ends to form derivatives that can be readily determined by 1H NMR spectroscopy. The TAI capped end-groups give rise to characteristic imidic NH resonances in a normally clear region of the 1H NMR spectrum [δ∼10-11.5 for C(O)-O-C(O)-NH-C(O)CCl3 from C(O)OH, δ∼8-9 for O-C(O)-NH-C(O)CCl3 from OH]. The method has been successfully applied to quantitative determination of the end-groups of a wide variety of oligomeric polyesters. It has also been applied to higher molecular weight polyesters including commercial, bottle grade, poly(ethylene terephthalate) (PET) and PET based copolyesters (e.g. PETG). 相似文献
26.
27.
The results of study of the effects of yttria stabilization (0–6 mol.%) on the room-temperature fracture behavior and toughening mechanisms in zirconia-reinforced MoSi2 are presented in this paper. Transformation toughening is shown to occur only in composites reinforced with zirconia particles stabilized with 2 mol.% yttria. However, the fracture toughness levels are comparable in the other composites with yttria levels between 0 and 6 mol.%. Toughening in the other composites is attributed to the combined effects of residual stress, microcrack shielding/anti-shielding and/or crack deflection. A rigorous micromechanics-based model is presented for the estimation of residual stress levels in brittle materials reinforced with phases that can transform during cooling or under stress. The model is applied successfully to the rationalization of the observed fracture and toughening phenomena. 相似文献
28.
Richard Quon 《电子产品世界》2002,(22):29-30,40
如今高性能通信系统有多种形式,在企业网络中,它也许是路由器,或是将以太局域网(LAN)的数据转发至OC-48 SONET光网络的多业务转换装置;在蜂窝网络中,它可能是第三代宽带无线网络控制器(RNC),将基站(BTS)的移动蜂窝电话呼叫发送至公共交换电话网(PSTN);在存储网络中,它可以是将服务器的数据备份至廉价磁盘冗余阵列(RAID)的光纤通道存储转换器。无论何种特殊类型的网络,这些系统的共同用途是接收来自信息源的数据,决定它需要发至何处,并有效地将它传送至目的地。为了支持这些关键功能,需要有一套通用通信元件或“基本构… 相似文献
29.
All leaders in health care today are charged with the responsibility of transforming present practices into new and different ones that are needed for the future. The structural side of transforming is ultimately easier than the human side. However, the most frequent failures come from not concentrating sufficiently on the behavioral side of the change. Structural and psychological change must occur simultaneously and embrace each other for best results. 相似文献
30.
Rahul Sarpeshkar Richard F. Lyon Carver Mead 《Analog Integrated Circuits and Signal Processing》1998,16(3):245-274
Low-power wide-dynamic-range systems are extremely hard to build. The biological cochlea is one of the most awesome examples of such a system: It can sense sounds over 12 orders of magnitude in intensity, with an estimated power dissipation of only a few tens of microwatts. In this paper, we describe an analog electronic cochlea that processes sounds over 6 orders of magnitude in intensity, and that dissipates 0.5 mW. This 117-stage, 100 Hz to 10 KHz cochlea has the widest dynamic range of any artificial cochlea built to date. The wide dynamic range is attained through the use of a wide-linear-range transconductance amplifier, of a low-noise filter topology, of dynamic gain control (AGC) at each cochlear stage, and of an architecture that we refer to as overlapping cochlear cascades. The operation of the cochlea is made robust through the use of automatic offset-compensation circuitry. A BiCMOS circuit approach helps us to attain nearly scale-invariant behavior and good matching at all frequencies. The synthesis and analysis of our artificial cochlea yields insight into why the human cochlea uses an active traveling-wave mechanism to sense sounds, instead of using bandpass filters. The low power, wide dynamic range, and biological realism make our cochlea well suited as a front end for cochlear implants. 相似文献