全文获取类型
收费全文 | 4651篇 |
免费 | 287篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 69篇 |
综合类 | 2篇 |
化学工业 | 1118篇 |
金属工艺 | 164篇 |
机械仪表 | 218篇 |
建筑科学 | 103篇 |
矿业工程 | 2篇 |
能源动力 | 161篇 |
轻工业 | 349篇 |
水利工程 | 21篇 |
石油天然气 | 11篇 |
武器工业 | 1篇 |
无线电 | 760篇 |
一般工业技术 | 909篇 |
冶金工业 | 440篇 |
原子能技术 | 35篇 |
自动化技术 | 587篇 |
出版年
2024年 | 12篇 |
2023年 | 36篇 |
2022年 | 130篇 |
2021年 | 200篇 |
2020年 | 119篇 |
2019年 | 103篇 |
2018年 | 157篇 |
2017年 | 147篇 |
2016年 | 156篇 |
2015年 | 146篇 |
2014年 | 193篇 |
2013年 | 305篇 |
2012年 | 278篇 |
2011年 | 317篇 |
2010年 | 248篇 |
2009年 | 250篇 |
2008年 | 221篇 |
2007年 | 198篇 |
2006年 | 168篇 |
2005年 | 114篇 |
2004年 | 113篇 |
2003年 | 105篇 |
2002年 | 74篇 |
2001年 | 96篇 |
2000年 | 79篇 |
1999年 | 64篇 |
1998年 | 159篇 |
1997年 | 126篇 |
1996年 | 86篇 |
1995年 | 68篇 |
1994年 | 70篇 |
1993年 | 61篇 |
1992年 | 39篇 |
1991年 | 43篇 |
1990年 | 26篇 |
1989年 | 32篇 |
1988年 | 27篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1977年 | 9篇 |
1976年 | 17篇 |
1975年 | 4篇 |
1974年 | 4篇 |
排序方式: 共有4950条查询结果,搜索用时 0 毫秒
11.
RG Wilde JT Billheimer SJ Germain EA Hausner PC Meunier DA Munzer JK Stoltenborg PJ Gillies DL Burcham SM Huang JD Klaczkiewicz SS Ko RR Wexler 《Canadian Metallurgical Quarterly》1996,4(9):1493-1513
Acyl-CoA:cholesterol acyltransferase (ACAT) is the enzyme largely responsible for intracellular cholesterol esterification. A systemic inhibitor of ACAT is believed to be able to slow or even reverse the atherosclerotic process. Towards that goal, a series of cyclic sulfides, derived from the hetero-Diels-Alder reaction of thioaldehydes with 1,3-dienes, and bearing carboxamide substituents, were prepared and evaluated for in vitro (in several tissues and species) and ex vivo ACAT inhibition. Minor changes in subsequent structure were found to have a significant effect in optimization of the biological activity of this series of compounds. 相似文献
12.
This study focuses on how to assess the optimal environmental investment decisions under economic and ecological uncertainty, and establishes the continuous time model using the real option approach to optimize environmental pollution policy. Unlike traditional cost benefit analysis, this work extends the model of [Pindyck, R.S., 2002. Optimal timing problems in environmental economics. Journal of Economic Dynamics and Control 26(9–10), 1677–1697], and attempts to identify the storage threshold of pollution stocks and the optimal timing for implementing environmental pollution decisions. 相似文献
13.
Takuma Suzuki Hang-Ju Ko Agus Setiawan Jung-Jin Kim Koh Saitoh Masami Terauchi Takafumi Yao 《Materials Science in Semiconductor Processing》2003,6(5-6):519-521
We report the successful growth of Ga-polar GaN epilayers on O-polar ZnO templates pre-deposited on c-sapphire. Prior to GaN growth, NH3 is exposed onto the ZnO template. The polarity of the GaN layers is confirmed by etching of the surface and by conversion beam electron diffraction (CBED), while the O-polar ZnO is confirmed by CBED. It is suggested that the NH3 pre-exposure helps form a Zn3N2 layer, which possesses inversion symmetry and inverts the crystal from anion polar to cation polar. 相似文献
14.
Dynamic RSVP protocol 总被引:5,自引:0,他引:5
Geng-Sheng Kuo Po-Chang Ko 《Communications Magazine, IEEE》2003,41(5):130-135
RSVP is a resource reservation setup protocol that can be used by a host to request specific QoS for multicast multimedia flows on the Internet. Multiprotocol label switching (MPLS) architecture also needs RSVP. The fact that the resolutions of the display system used in different receiver nodes might have different, multi-resolution characteristics is supported in the MPEG-4 standard, and the EZW compression algorithm can cease decoding at any point in the bitstream. However, RSVP does not provide a more flexible mechanism. In this article we propose an extension of RSVP to provide the needed mechanism, coined dynamic RSVP (DRSVP), to dynamically adjust reserved resources on nodes without much effort. It provides different video resolutions to different receiver nodes with different needed reserved resources. Therefore, it does not waste precious Internet resources to transmit unnecessary multimedia packets. 相似文献
15.
To identify possible sources of the observed differences in the career choices of women and men, three facets of career preferences were examined: the relative importance attributed to career-related aspects, the within-aspect preferences (i.e., desirable characteristics of occupations), and the structure of aspects derived from these within-aspect preferences. The career-related preferences of 2,000 young adults who were in the process of making their career decisions were analyzed. These career-related preferences were elicited during their dialogues with a computer-assisted career guidance system. The analyses revealed (a) only small gender differences in the relative importance of the aspects, (b) considerable gender differences in the within-aspect preferences, and (c) certain gender differences in the structure of aspects. The findings and their possible theoretical and practical implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
A reinjection experiment has been conducted in an attempt to sustain reservoir pressure and steam production and to extract remaining heat energy in the superheated reservoir in the Matsukawa vapor-dominated geothermal field. This experiment was undertaken because the increase in superheat of produced steam and the decline of steam production are the current major issues for stable operation of the power plant. Almost all the reinjected fluid into well MR 1 was recovered from well M5, and the steam production of well M5 has increased by approximately 67%. 相似文献
17.
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
18.
By comparing the experimental data of the Sauter-mean-diameter d 32 and the hold up ? with models from literature, there are presented equations for d 32 and ? for the used conical turbine in gas-liquid systems. The necessary adjustment of the proportionality constants of the literature equations will be explained on the basis of fluiddynamical phenomena. It can be established by fluid-dynamical results of a former study carried out with laser-doppler-anemometry. Coalescence phenomena are taken into account in the model using an analogy to bubble columns. The analogy to bubble columns turns out to be suitable. Arguments for the necessity of considering the local fluiddynamics in the modelling of dispersions are presented. 相似文献
19.
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
20.
Ma Z.J. Chen J.C. Liu Z.H. Krick J.T. Cheng Y.C. Hu C. Ko P.K. 《Electron Device Letters, IEEE》1994,15(3):109-111
It has been reported that high-temperature (~1100°C) N2 O-annealed oxide can block boron penetration from poly-Si gates to the silicon substrate. However, this high-temperature step may be inappropriate for the low thermal budgets required of deep-submicron ULSI MOSFETs. Low-temperature (900~950°C) N2O-annealed gate oxide is also a good barrier to boron penetration. For the first time, the change in channel doping profile due to compensation of arsenic and boron ionized impurities was resolved using MOS C-V measurement techniques. It was found that the higher the nitrogen concentration incorporated at Si/SiO2 interface, the more effective is the suppression of boron penetration. The experimental results also suggest that, for 60~110 Å gate oxides, a certain amount of nitrogen (~2.2%) incorporated near the Si/SiO2 interface is essential to effectively prevent boron diffusing into the underlying silicon substrate 相似文献