全文获取类型
收费全文 | 701篇 |
免费 | 49篇 |
专业分类
电工技术 | 22篇 |
综合类 | 1篇 |
化学工业 | 191篇 |
金属工艺 | 10篇 |
机械仪表 | 15篇 |
建筑科学 | 23篇 |
能源动力 | 23篇 |
轻工业 | 152篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 121篇 |
一般工业技术 | 73篇 |
冶金工业 | 49篇 |
原子能技术 | 1篇 |
自动化技术 | 64篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 34篇 |
2021年 | 31篇 |
2020年 | 28篇 |
2019年 | 27篇 |
2018年 | 26篇 |
2017年 | 32篇 |
2016年 | 32篇 |
2015年 | 17篇 |
2014年 | 37篇 |
2013年 | 56篇 |
2012年 | 58篇 |
2011年 | 40篇 |
2010年 | 35篇 |
2009年 | 21篇 |
2008年 | 27篇 |
2007年 | 20篇 |
2006年 | 17篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 16篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 12篇 |
1998年 | 20篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有750条查询结果,搜索用时 15 毫秒
41.
42.
A method for encapsulation stress drift measurement based on the piezo-Hall effect is proposed. Accuracy of ±0.25 MPa for the sum of in-plane normal stresses is achieved. Using this method, the drift of die stress in IC plastic packages has been measured after temperature cycling. Stress relaxation with the time constant of about one day has been observed. 相似文献
43.
Wireless networks that utilize dynamic channel allocation (DCA) are known to perform better than those with fixed channel allocation, in terms of the call level QoS measures such as the handoff dropping probability. On account of this, the DCA networks are usually designed without the call admission control (CAC). However, given the decrease of cell sizes, together with ever increasing mobile phone and terminal population, dynamic channel allocation policies (such as channel borrowing) may not be sufficient to cope with the hot-spot area size and its traffic intensity. This paper analyses the performance of the DCA networks, both with and without the call admission control, under the hot-spot traffic regime. In such cases, the pure DCA approach fails to ensure sufficiently low level of QoS in both the hot-spot area and the surrounding cells. We propose a CAC policy that can stabilize the QoS under non-uniform traffic, whilst being easy to integrate in the distributed DCA policies. 相似文献
44.
Jelena Milosevic David S. Ashton & Michael J. Cocksedge 《International Journal of Food Science & Technology》2002,37(5):523-526
Olive oil is a major constituent of many food preparations and is used in margarine and as a cooking oil. Olive oil consists of lipidic components, mainly fatty acids, in differing proportions depending on the source of the olive and the method of preparation. Although several studies have been made on the lipid composition of the extracted oil, no detailed analysis has been made on olive skin as a discrete entity. Analysis by gas chromatography (GC) of an olive skin extract showed oleic acid (61.45%), palmitic acid (15.28%) and linoleic acid (11.69%) to predominate. Smaller amounts of other fatty acids, not previously detected in olive fruit, were also found to be present in olive skin. 相似文献
45.
W. Brenner G. Haddad H. Detter G. Popovic A. Vujanic N. Delic 《Microsystem Technologies》1997,3(2):68-71
A miniaturized torque sensor based on cable brake principle for the measurement of torque-characteristic of minimotors and
micromotors has been developed. The first generation torque sensor enables the measurement of torque of minimotors in the
range of μNm. Design principles and the production process are described. Experimental results show fair conformity with technical
data for minimotors.
Received: 30 October 1996 / Accepted: 14 November 1996 相似文献
46.
GM Evins DN Cameron JG Wells KD Greene T Popovic S Giono-Cerezo IK Wachsmuth RV Tauxe 《Canadian Metallurgical Quarterly》1995,172(1):173-179
Since the Latin American cholera epidemic began in 1991, 447 isolates of Vibrio cholerae O1 from the Western Hemisphere have been assayed by multilocus enzyme electrophoresis (MEE) to determine allelic variation among 16 enzyme-encoding genes. Two electrophoretic types (ETs) were identified among toxigenic isolates from Latin America: 323 were ET 4, the ET associated with the Latin American epidemic, and 29 were ET 3. Twenty-three of these ET 3 isolates had a distinctive antimicrobial resistance pattern also seen in isolates imported into the United States from Latin America and Southeast Asia. These resistant isolates had an identical ribotype and nearly identical pulsed-field gel electrophoresis (PFGE) patterns. Most nontoxigenic isolates analyzed were not precursors or descendants of toxigenic epidemic strains. MEE provided a population genetic frame-work for the interpretation of PFGE and ribotype data from the isolates in this study. All three methods identified 2 distinct strains of toxigenic V. cholerae O1 currently epidemic in Latin America. 相似文献
47.
Ivana Mašić Ilija Ilić Rok Dreu Svetlana Ibrić Jelena Parojčić Stanko Srčič 《Drug development and industrial pharmacy》2014,40(1):23-32
Objective: The aim of this study was to investigate the influence of process parameters, binder content and binder addition method on characteristics of the granules obtained by melt granulation (MG) in fluidized bed.Methods: Spray-on experiments were performed according to 23 full factorial design. The effect of binder content, molten binder feed rate, and spray air pressure on granule size and size distribution, granule shape, ?owability and drug release rate was investigated. In the in situ experiments, the influence of binder particle size and binder content was evaluated. Solid-state characterization was performed by means of differential scanning calorimetry, X-ray powder diffraction and Fourier transform infrared spectroscopy.Results: Size of the granules obtained by spray-on procedure was significantly influenced by binder content and spray air pressure, while the width of particle size distribution was mainly affected by binder feed rate. Spray air pressure showed the most significant influence on granule shape. It was shown that smooth and spherical particles with good flow properties may be obtained by both procedures, spray-on and in situ MG. The results obtained indicated the influence of agglomeration mechanism on granule sphericity, with higher degree of granule sphericity observed when immersion and layering was the dominant mechanism. Paracetamol release from granulates was very rapid, but after compression of the granules into tablets, drug release was considerably slower. Solid-state analysis confirmed that the physical form of the granulate components remained unaffected after the MG process.Conclusion: The results presented indicate that MG in fluidized bed could be a good alternative to conventional granulation techniques. 相似文献
48.
During the last few years, several models have been proposed for the calculation of green roof thermal behavior, but the validation studies of such models are lacking a comprehensive set of highly accurate data. In this study, an experimental laboratory setup was used to create different environmental conditions and to measure sensible heat fluxes to/from a vegetated roof assembly. This experimental setup has been successfully used for different wind velocities (0–3 m/s) to create free and forced convection conditions around green roof tested samples. Furthermore, our study proposed a “basic model” for calculations of the convective heat transfer at green roof assemblies, which is a modified version of the Newton’s cooling law, calibrated and then validated with different sets of data. For forced convection flow regimes, the proposed “basic model” resulted in RMSE (Root Mean Square Error) of 11 W/m2 and R2 value of 0.81. Similarly, the model provided RMSE of 6.6 W/m2 and R2 of 0.90 for sensible heat fluxes with free convection conditions. In the future, this model will be used in on-site experimental studies to understand its performance under wind conditions that exhibit a much wider range than the studied velocity range near the leaf canopy. 相似文献
49.
Kotoni D Ciogli A Molinaro C D'Acquarica I Kocergin J Szczerba T Ritchie H Villani C Gasparrini F 《Analytical chemistry》2012,84(15):6805-6813
A new chiral stationary phase for ultrahigh-pressure liquid chromatography (UHPLC) applications was prepared by covalent attachment of the Whelk-O1 selector to spherical, high-surface-area 1.7-μm porous silica particles. Columns of varying dimensions (lengths of 50, 75, 100, and 150 mm and internal diameters of 3.0 or 4.6 mm) were packed and characterized in terms of permeability, efficiency, retention, and enantioselectivity, using both organic and water-rich mobile phases. A conventional HPLC Whelk-O1 column based on 5.0-μm porous silica particles and packed in a 250 mm × 4.6 mm column was used as a reference. Van Deemter curves, generated with low-molecular-weight solutes on a 100 mm × 4.6 mm column packed with the 1.7-μm particles, showed H(min) (μm) and μ(opt) (mm/s) values of 4.10 and 5.22 under normal-phase and 3.74 and 4.34 under reversed-phase elution conditions. The flat C term of the van Deemter curves observed with the 1.7-μm particles allowed the use of higher-than-optimal flow rates without significant efficiency loss. Kinetic plots constructed from van Deemter data confirmed the ability of the column packed with the 1.7-μm particles to afford subminute separations with good efficiency and its superior performances in the high-speed regime, compared to the column packed with 5.0-μm particles. Resolutions in the time scale of seconds were obtained using a 50-mm-long column in the normal phase or polar organic mode. The intrinsic kinetic performances of 1.7-μm silica particles are retained in the Whelk-O1 chiral stationary phase, clearly demonstrating the potentials of enantioselective UHPLC in terms of high speed, throughput, and resolution. 相似文献
50.
Weikle R.M. II Kim M. Hacker J.B. De Lisio M.P. Popovic Z.B. Rutledge D.B. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1992,80(11):1800-1809
Although quasi-optical techniques are applicable to a large variety of solid-state devices, special attention is given to transistors, which are attractive because they can be used as either amplifiers or oscillators. Experimental results for MESFET bar-grid and planar grid oscillators are presented. A MESFET grid amplifier that receives only vertically polarized waves at the input and radiates horizontally polarized waves at the output is discussed. These planar grids can be scaled for operation at millimeter- and submillimeter-wave frequencies. By using modern IC fabrication technology, planar grid oscillators and amplifiers containing thousands of devices can be built, thereby realizing an efficient means for large-scale power combining 相似文献