全文获取类型
收费全文 | 12850篇 |
免费 | 488篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 121篇 |
综合类 | 4篇 |
化学工业 | 1723篇 |
金属工艺 | 174篇 |
机械仪表 | 224篇 |
建筑科学 | 178篇 |
矿业工程 | 17篇 |
能源动力 | 285篇 |
轻工业 | 1331篇 |
水利工程 | 64篇 |
石油天然气 | 45篇 |
无线电 | 399篇 |
一般工业技术 | 1098篇 |
冶金工业 | 6876篇 |
原子能技术 | 49篇 |
自动化技术 | 761篇 |
出版年
2024年 | 25篇 |
2023年 | 78篇 |
2022年 | 211篇 |
2021年 | 350篇 |
2020年 | 227篇 |
2019年 | 289篇 |
2018年 | 304篇 |
2017年 | 332篇 |
2016年 | 281篇 |
2015年 | 208篇 |
2014年 | 283篇 |
2013年 | 528篇 |
2012年 | 411篇 |
2011年 | 446篇 |
2010年 | 316篇 |
2009年 | 351篇 |
2008年 | 306篇 |
2007年 | 262篇 |
2006年 | 220篇 |
2005年 | 142篇 |
2004年 | 142篇 |
2003年 | 154篇 |
2002年 | 117篇 |
2001年 | 79篇 |
2000年 | 83篇 |
1999年 | 285篇 |
1998年 | 2169篇 |
1997年 | 1223篇 |
1996年 | 896篇 |
1995年 | 469篇 |
1994年 | 388篇 |
1993年 | 418篇 |
1992年 | 68篇 |
1991年 | 103篇 |
1990年 | 78篇 |
1989年 | 84篇 |
1988年 | 90篇 |
1987年 | 76篇 |
1986年 | 81篇 |
1985年 | 61篇 |
1983年 | 10篇 |
1982年 | 29篇 |
1981年 | 46篇 |
1980年 | 69篇 |
1979年 | 10篇 |
1978年 | 22篇 |
1977年 | 141篇 |
1976年 | 334篇 |
1975年 | 18篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Estimates of loudness balance were obtained for acoustically and electrically presented 250 Hz sine signals from a patient who uses the Ineraid multichannel cochlear implant. Acoustic and electric loudness matching was possible because the patient evidenced a 25 dB HL threshold at 250 Hz in his nonimplanted ear. The level of the electrical stimulus in microamperes required for a balance of loudness grew linearly with equal increments in decibels for the acoustic stimulus. These data, in concert with the very limited data from previous studies, provide a rationale for using a logarithmic transformation of acoustic to electric intensity in signal processors for cochlear implants. 相似文献
52.
B. Herreros G. Lifante A. Kling J.C. Soares M.F. da Silva P.D. Townsend P.J. Chandler J. Olivares J.M. Cabrera 《Optical Materials》1996,6(4):281-286
We present a structural study of two Nd3+/MgO codoped LiNbO3 waveguides fabricated by two different methods: ion-implantation and proton-exchange. Rutherford backscattering spectrometry in combination with channelling was used to study the influence of the waveguide fabrication method on the possible modification of the LiNbO3 crystal structure within the waveguiding layer. The results show that the ion-implanted waveguide mainly maintains the same properties as the virgin crystal, apart from a deterioration of a thin surface layer, whilst the proton-exchanged waveguide exhibits a quite different behaviour, although its surface is less damaged. 相似文献
53.
JR Monties J Trinkl T Mesana PJ Havlik JL Demunck 《Canadian Metallurgical Quarterly》1996,61(1):463-468
For decades, research for developing a totally implantable artificial ventricle has been carried on. For 4 to 5 years, two devices have been investigated clinically. For many years, we have studied a rotary (but not centrifugal) pump that furnishes pulsatile flow without a valve and does not need external venting or a compliance chamber. It is a hypocycloidal pump based on the principle of the Maillard-Wankel rotary compressor. Currently made of titanium, it is activated by an electrical brushless direct-current motor. The motor-pump unit is totally sealed and implantable, without noise or vibration. This pump was implanted as a left ventricular assist device in calves. The midterm experiments showed good hemodynamic function. The hemolysis was low, but serious problems were encountered: blood components collecting on the gear mechanism inside the rotor jammed the pump. We therefore redesigned the pump to seal the gear mechanism. We used a double system to seal the open end of the rotor cavity with components polished to superfine optical quality. In addition, we developed a control system based on the study of the predicted shape of the motor current. The new design is now underway. We hope to start chronic experiments again in a few months. If the problem of sealing the bearing could be solved, the Cora ventricle could be used as permanent totally implantable left ventricular assist device. 相似文献
54.
P Cruz R Almeida M Gon?alves G Marote J Silva C Cavaleiro V Jacinto 《Canadian Metallurgical Quarterly》1994,7(5):277-280
Ocular paresis is a usual diagnosis in neuro-ophthalmologic consultation, and its aetiology is indeed a challenge. The authors studied 3400 records concerning this consultation, between 1982 and the third quarter of 1993. During this period 221 cases with ocular paresis were selected. During this retrospective study we point out the following items: the cranial nerve affected; the neuro-ophthalmologic semiology; the aetiology and clinical evolution, according to the age groups. From 221 cases selected, 111 were paresis from the VIth pair (50.2%), 88 from the IIIrd pair (39.8%), 14 multiple paresis (6.4%) and 8 paresis from the IVth pair (3.6%). The most frequent complaint was diplopia (> 90%). As far as the aetiological diagnosis is concerned, this was easier to establish in patients > 50 years of age. In this age group the most usual aetiology was vascular and traumatic pathologies. In younger patients the most frequent pathologies were traumatic and tumoral. The prognostic was better in the vascular group, the paresis recovery being > 50% in all other pathologies, except the tumoral one. 相似文献
55.
Four cannulated cows in a 4 x 4 Latin square design were used to study the effects of supplemental dietary fatty acids from roasted soybeans combined with tallow or partially hydrogenated fats, varying in esterification and fatty acid chain length, on nutrient digestion and lactation performance. Diets were formulated to contain (DM basis) 48% forage in addition to 1.5% fatty acids from roasted soybeans and 2.5% fatty acids from tallow, partially hydrogenated tallow triglycerides, partially hydrogenated tallow fatty acids, or a blend of 30% tallow and 70% hydrogenated fatty acids that were rich in palmitic acid. Apparent total tract digestibilities of OM, N, and NDF were similar among diets. Supplemental fat as fatty acids, compared with triglycerides, increased digestibilities of total fatty acids and C18:1 in the small intestine, perhaps indicating that lipolysis was rate-limiting. Fatty acids also increased milk fat percentage and efficiency of 4% FCM production. Although intake of C16 fatty acids was higher for cows fed the fat rich in palmitic acid than for those fed the tallow fatty acids, total duodenal flows of C16 fatty acids were similar, and digestibility in the small intestine was unaffected. Dry matter intake, 4% FCM production, and milk protein percentage were similar among treatments. 相似文献
56.
57.
58.
DL Zealear CL Rainey GD Herzon JL Netterville RH Ossoff 《Canadian Metallurgical Quarterly》1996,105(9):689-693
This study represents the first attempt to electrically pace the paralyzed human larynx. The goal was to determine if electrical stimulation of the posterior cricoarytenoid muscle could produce functional abduction of the vocal fold in pace with inspiration. An external apparatus was used to sense inspiration and reanimate the unilaterally paralyzed larynx of a thyroplasty patient. Stimuli were delivered through a needle electrode to locate and pace the abductor muscle. The magnitude of electrically induced abduction was comparable to spontaneous movement on the normal side. The abduction was appropriately timed with inspiration: this finding demonstrated that this simple pacing system could effectively modulate stimulation with patient respiration. 相似文献
59.
A method of posterior mitral annulus remodeling is presented. The posterior annulus is divided into three segments, each segment encircled by a suture that is passed in a tourniquet. Coaptation of the leaflets can be achieved by tightening the tourniquets while the ventricle is being filled. This technique is simple and quick, avoids the use of foreign material, and requires less expertise and judgment than traditional annuloplasties. 相似文献
60.