全文获取类型
收费全文 | 998篇 |
免费 | 54篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 24篇 |
化学工业 | 222篇 |
金属工艺 | 7篇 |
机械仪表 | 18篇 |
建筑科学 | 31篇 |
矿业工程 | 2篇 |
能源动力 | 22篇 |
轻工业 | 57篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 134篇 |
一般工业技术 | 222篇 |
冶金工业 | 163篇 |
原子能技术 | 3篇 |
自动化技术 | 147篇 |
出版年
2023年 | 3篇 |
2022年 | 12篇 |
2021年 | 24篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 20篇 |
2017年 | 30篇 |
2016年 | 32篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 50篇 |
2012年 | 37篇 |
2011年 | 43篇 |
2010年 | 31篇 |
2009年 | 40篇 |
2008年 | 44篇 |
2007年 | 38篇 |
2006年 | 42篇 |
2005年 | 29篇 |
2004年 | 27篇 |
2003年 | 32篇 |
2002年 | 33篇 |
2001年 | 27篇 |
2000年 | 18篇 |
1999年 | 18篇 |
1998年 | 55篇 |
1997年 | 42篇 |
1996年 | 39篇 |
1995年 | 25篇 |
1994年 | 16篇 |
1993年 | 20篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1056条查询结果,搜索用时 15 毫秒
131.
132.
Goh Z. Tan K.-C. Tan B.T.G. 《Vision, Image and Signal Processing, IEE Proceedings -》1998,145(1):23-29
The authors examine the possibility of improving the quality of speech obtained with continuously variable slope delta-modulation (CVSD), a speech coding method that has been quite widely employed in mobile radios. CVSD is well-known for its robustness and implementation simplicity, but the quality of the resultant speech (commonly at 16 kbps) is often not very satisfactory. Through their study, the authors obtain two crucial findings on the characteristics of the disturbance/noise introduced by CVSD. Based on their findings, they develop a method for estimating the short-time power spectra of CVSD noise, and this enables them to apply existing speech enhancement methods to effectively suppress CVSD noise. Performance assessments based on objective measures such as signal-to-noise ratio (SNR), segmental SNR, and COSH distortion measure, and informal subjective listening tests have all indicated significant improvements in speech quality 相似文献
133.
Perceptions of personal and group discrimination in 5 domains (jobs, pay, loans, promotions, and clubs) were investigated via telephone interviews with 902 respondents from different ethnic groups in Toronto. The reported analyses concern 6 ethnic groups, representing "visible," racial minorities (Blacks, Chinese, and South Asians) as well as White minorities (Italians, Jews, and Portuguese). The personal/group discrimination discrepancy (i.e., perceiving greater discrimination toward one's group than oneself personally) was observed to varying extent across all domains and ethnic groups, though with some exceptions. Visible minorities perceived greater discrimination toward their group than did White minorities, especially in the economic domains of jobs, pay, and promotions. Among visible minorities, Black respondents perceived higher levels of group and personal discrimination than most other ethnic groups across domains, followed in turn by Chinese and South Asian respondents. By contrast, White minority group members perceived considerably less group or personal discrimination than members of visible minorities, except for Jewish respondents who reported greater group discrimination in joining clubs than any other ethnic group. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
134.
We have demonstrated previously that growth hormone (GH) activates focal adhesion kinase (FAK), and this activation results in the tyrosine phosphorylation of two FAK substrates, namely paxillin and tensin. We now show here in Chinese hamster ovary cells stably transfected with rat GH receptor cDNA that human (h)GH induces the formation of a large multiprotein signaling complex centered around another FAK-associated protein, p130(Cas) and the adaptor protein CrkII. hGH stimulates the tyrosine phosphorylation of both p130(Cas) and CrkII, their association, and the association of multiple other tyrosine-phosphorylated proteins to the complex. Both the c-Src and c-Fyn tyrosine kinases are tyrosine phosphorylated and activated by cellular hGH stimulation and form part of the multiprotein signaling complex as does tensin, paxillin, IRS-1, the p85 subunit of phosphatidylinositol 3-kinase, C3G, SHC, Grb-2, and Sos-1. c-Cbl and Nck are also tyrosine-phosphorylated by cellular stimulation with hGH and associate with the p130(Cas)-CrkII complex. c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) is activated in response to hGH in accordance with the formation of the abovementioned signaling complex, and hGH stimulated JNK/SAPK activity is increased in CrkII overexpressing NIH3T3 cells compared with vector transfected NIH3T3 cells. The formation of such a large multiprotein signaling complex by GH, with the resultant activation of multiple downstream effector molecules, may be central to many of the pleiotropic effects of GH. 相似文献
135.
Using a formula based on the concept by N. C. Andreasen (see record 1982-29376-001) and N. C. Andreasen and S. Olsen (see record 1982-30452-001) of classifying subtypes into positive, negative, and mixed schizophrenia, 312 persons institutionalized with Diagnostic and Statistical Manual of Mental Disorders (DSM-III) schizophrenia were retrospectively examined. 59 Ss were classified into the positive symptom subtype, 33 into the negative symptom subtype, and 220 into the mixed symptom subtype. Symptom subtypes were compared on traditional demographic and outcome indicators, as well as on a dimension critical to rehabilitation (i.e., measures of degree of assistance necessary to perform functional skills). No significant differences were found among the subtypes on demographic items and traditional indicators of outcome such as level of vocational functioning or independent living. However, on measures of degree of assistance necessary to perform functional skills, significant differences were found among the symptom subtypes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
136.
If chalcopyrite is roasted with sulphur at 400–450°C pyrite and idaite or bornite are produced. Bornite plus pyrite are also prepared by roasting a 1:1 mixture of chalcopyrite and covellite. These copper-iron sulphides were leached with acidified aqueous cupric sulphate solutions containing acetonitrile or hydracrylonitrile and the results are compared with leaching with acidified cupric chloride in brine. The nitrile route has the advantage of a less corrosive sulphate medium for subsequent copper recovery processes.Bornite appears to be the most attractive product from the roasting of sulphur and chalcopyrite because much of its copper can be readily leached. Iron reports to the solution only in the latter stages of extraction. Up to 80% of the copper in this bornite is leached with CuSO4/RCN/H2O at 60°C. Copper is recovered from the resulting cuprous sulphate solution by electrowinning with inert anode. The products are copper cathodes and cupric sulphate, which is recycled. The leach residue may be used to reactivate further chalcopyrite or is leached of its copper by established routes. 相似文献
137.
A convenient method, not involving ashing or acid digestion, for the determination of inorganic phosphorus content in crude
palm oil, is developed. Direct extraction from solvent-diluted palm oil by dilute acid allows the inorganic phosphates to
be analyzed by the usual phosphomolybdenum blue complex. Using this method, phosphate analyses in palm oil samples were correlated
with other oil quality parameters and the results discussed. 相似文献
138.
Ultrasonic energy is widely used in wire bonding for microelectronics packaging. It is necessary to ensure that the maximum ultrasonic vibration displacement occurs at or near the tip of the bonding tool (capillary) for optimal performance. In this study, amplitude profiles of ultrasonic vibrations along capillaries were measured with load using a laser interferometer. This provided valuable information in understanding and improving capillary performance. The method was applied to real time applications to optimize capillary designs and bonding processes for specific bonding applications. First, the application of a new capillary material with different zirconia compositions was evaluated. The new material with certain amount of zirconia composition showed that it was the capillary material of choice for ultra-fine pitch wire bonding. Next, comparative analysis was conducted to investigate the ultrasonic energy transfer of a new ‘slimline’ bottleneck and the conventional bottleneck. The actual bonding response of the molded slimline bottleneck showed comparable performance with the ground conventional bottleneck using the same bonding parameters. Finally, optimization of a 60-μm-bond-pad-pitch process was performed on a wire bonder. Within the optimized parameter ranges, the ultrasonic displacement of the capillary was monitored. For all possible combinations of bond force and bond power, the ultrasonic displacement of the capillary increased with increasing bond power, without drastic changes caused by bond force changes. This indicated that the selected process window was located in a stable region. 相似文献
139.
Fallahi M. Chatenoud F. Templeton I.M. Dion M. Wu C.M. Delage A. Barber R. 《Photonics Technology Letters, IEEE》1992,4(10):1087-1089
The authors demonstrate the fabrication and room temperature operation of an electrically pumped circular-grating surface-emitting distributed-Bragg-reflector laser. An InGaAs/GaAs single quantum well (SQW) graded-index separate confinement heterostructure (GRINSCH) structure was grown by one-step molecular beam epitaxy (MBE). Circular gratings were defined by focused ion beam lithography. The lasing wavelength was 942 nm, and the threshold current was 280 mA. This is the first demonstration of these lasers with no epitaxial regrowth 相似文献
140.
Goh H. L. Tan K. K. Huang S. de Silva C. W. 《Industrial Informatics, IEEE Transactions on》2006,2(4):221-230
There is a growing trend in developing the wireless machine-to-machine (M2M) communication for factory automation. Currently, most wireless protocols for infrastructureless mobile ad-hoc networks focus on the mobility issue and are mainly suitable for narrowband radio devices. The mechanisms for route update and discovery that work well for wireless mobile ad-hoc networks prove to be redundant and instead add to processing overheads in a static wireless factory setting. This paper presents the development and implementation of a new wireless routing protocol, Bluewave, that caters specifically to wireless communication between machines in a factory setting. Bluewave utilizes features of Bluetooth technology when performing the route setup. The merits of the proposed protocol, in terms of shorter initialization time and route setup time, are duly discussed. A case study illustrating the application of Bluewave to an online condition-based maintenance scenario is presented. Experimental results obtained are furnished to show the viability of Bluewave in industrial automation 相似文献