全文获取类型
收费全文 | 14270篇 |
免费 | 1084篇 |
国内免费 | 50篇 |
学科分类
工业技术 | 15404篇 |
出版年
2024年 | 43篇 |
2023年 | 154篇 |
2022年 | 193篇 |
2021年 | 470篇 |
2020年 | 447篇 |
2019年 | 384篇 |
2018年 | 655篇 |
2017年 | 634篇 |
2016年 | 726篇 |
2015年 | 485篇 |
2014年 | 653篇 |
2013年 | 1546篇 |
2012年 | 782篇 |
2011年 | 890篇 |
2010年 | 751篇 |
2009年 | 778篇 |
2008年 | 670篇 |
2007年 | 598篇 |
2006年 | 462篇 |
2005年 | 326篇 |
2004年 | 326篇 |
2003年 | 320篇 |
2002年 | 347篇 |
2001年 | 337篇 |
2000年 | 264篇 |
1999年 | 217篇 |
1998年 | 384篇 |
1997年 | 289篇 |
1996年 | 168篇 |
1995年 | 121篇 |
1994年 | 119篇 |
1993年 | 91篇 |
1992年 | 64篇 |
1991年 | 78篇 |
1990年 | 47篇 |
1989年 | 53篇 |
1988年 | 47篇 |
1987年 | 26篇 |
1986年 | 30篇 |
1985年 | 48篇 |
1984年 | 38篇 |
1983年 | 39篇 |
1982年 | 38篇 |
1981年 | 33篇 |
1980年 | 31篇 |
1979年 | 28篇 |
1978年 | 23篇 |
1977年 | 20篇 |
1976年 | 27篇 |
1974年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 803 毫秒
81.
M. Hofbaur ÖVE N. Dourdoumas ÖVE 《e & i Elektrotechnik und Informationstechnik》1997,114(7-8):371-379
Qualitative-quantitative simulation is one of the most productive and promising research areas in Artificial Intelligence to emerge in recent years. This method provides an elegant way for an exhaustive analysis of uncertain dynamic systems. The application of the qualitative-quantitative simulation is shown in this paper. The important question about the stability of a quanlitatively described dynamical system is solved by a novel analytic method. 相似文献
82.
Assaderaghi F. Chen J. Solomon R. Chian T.-Y. Ko P.K. Hu C. 《Electron Device Letters, IEEE》1991,12(10):518-520
It has been found that the subthreshold currents of fully depleted silicon-on-insulator (SOI) MOSFETs show a transient behavior under certain front-gate and back-gate voltage conditions. The cause of this anomaly is explained, and applications for the phenomenon are pointed out. Particularly, a simple way to measure the silicon film thickness is suggested 相似文献
83.
B. J. Mayr ÖVE IEEE H. Weinrichter ÖVE IEEE 《e & i Elektrotechnik und Informationstechnik》1997,114(3):123-130
Modern communication systems offer high speed and reliable data transmission services. The quality of these services is achieved by combining coded multi-level modulation techniques and modern digital signal processing (Viterbi-decoding) in the receiver. In this paper we first present an introduction to Trellis Coded Modulation (TCM) and then some new results on unversal techniques adapted for the AWGN-channel as well as for the fading channel. It is shown that TCM is well suited for communication channels with time variant characteristics (e.g. mobile communication channels), especially when our new codes are applied. 相似文献
84.
S. P. Ashburn M. C. Öztürk J. J. Wortman G. Harris J. Honeycutt D. M. Maher 《Journal of Electronic Materials》1992,21(1):81-86
Titanium and cobalt germanides have been formed on Si (100) substrates using rapid thermal processing. Germanium was deposited
by rapid thermal chemical vapor deposition prior to metal evaporation. Solid phase reactions were then performed using rapid
thermal annealing in either Ar or N2 ambients. Germanide formation has been found to occur in a manner similar to the formation of corresponding silicides. The
sheet resistance was found to be dependent on annealing ambient (Ar or N2) for titanium germanide formation, but not for cobalt germanide formation. The resistivities of titanium and cobalt germanides
were found to be 20 μΩ-cm and 35.3μΩ-cm, corresponding to TiGe2 and Co2Ge, respectively. During solid phase reactions of Ti with Ge, we have found that the Ti6Ge5 phase forms prior to TiGe2. The TiGe2 phase was found to form approximately at 800° C. Cobalt germanide formation was found to occur at relatively low temperatures
(425° C); however, the stability of the material is poor at elevated temperatures. 相似文献
85.
A study is made of boron removal from Kizildere/Turkey geothermal waste water using the boron selective resin Amberlite IRA 743. The resin in salt form has no boron removal capacity if the solution is unable to neutralize the released acid during the exhaustion period. In the case of Kizildere waste water, with a pH value of 8.9 and high HCO3− content, single stage regeneration is feasible and the exhausted resin can be regenerated economically. According to a preliminary estimate, the electricity production cost would rise by 1 ¢/kWh. 相似文献
86.
The purpose of this study was to evaluate the relationship between the number of yolk sacs and amnionicity in monochorionic twin pregnancies scanned early in the first trimester. We retrospectively reviewed images of all monochorionic twins scanned between 6 and 9.5 weeks' gestation and with pathologic or sonographic confirmation of chorionicity-amnionicity. Each film was reviewed for the number of yolk sacs present, as well as for the gestational age at which the amniotic membrane was first visualized. Twenty monochorionic-diamniotic pregnancies and two monochorionic-monoamniotic pregnancies met the criteria for inclusion in the study. In diamniotic pregnancies scanned at less than 8 weeks' gestation, only the yolk sacs were identified; none of the dividing amniotic membranes were detected. Two yolk sacs were identified in all but one case. In this case, although one yolk sac was seen at 6 weeks, follow-up scanning at 8 weeks revealed two yolk sacs. In each of the monochorionic-monoamniotic twin pregnancies, one yolk sac was seen at 9 weeks and a single amnion encircled both embryos. We conclude that the sonographic identification of two yolk scas in monochorionic twins enables us to make the diagnosis of diamniotic twins early in the first trimester, before the amniotic membrane can be imaged. The presence of one yolk sac should prompt a follow-up ultrasonogram to assign amnionicity definitively. 相似文献
87.
88.
Jale Müslehiddinolu Paul Lobben Simon Leung Lori Spangler San Kiang 《Catalysis Today》2007,123(1-4):164-170
Hydrogenolysis of a carbobenzyloxy group (CBz) was studied utilizing molecular hydrogen in the presence of carbon-supported palladium catalyst. It was demonstrated that the kinetics of the reaction are greatly influenced by the presence of the CO2 by-product. It was found out that the presence of CO2 determines whether the reaction is first or zero order since it causes deactivation of the catalyst via inhibition. The effect of potassium carbonate (K2CO3) and triethylamine (TEA) as additives was investigated. A considerable solvent effect was also observed that may be explained by the variation of dispersion of the catalyst from one solvent to another. 相似文献
89.
本文对国内外微机在玻璃工业中的应用现状进行了综述与评价 ,主要讨论微机应用对玻璃工业的影响 ,并初步探讨了玻璃工业中微机应用的前景 相似文献
90.