全文获取类型
收费全文 | 4295篇 |
免费 | 264篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 39篇 |
综合类 | 3篇 |
化学工业 | 1205篇 |
金属工艺 | 132篇 |
机械仪表 | 103篇 |
建筑科学 | 149篇 |
矿业工程 | 15篇 |
能源动力 | 152篇 |
轻工业 | 849篇 |
水利工程 | 48篇 |
石油天然气 | 18篇 |
无线电 | 179篇 |
一般工业技术 | 858篇 |
冶金工业 | 124篇 |
原子能技术 | 47篇 |
自动化技术 | 640篇 |
出版年
2024年 | 13篇 |
2023年 | 52篇 |
2022年 | 87篇 |
2021年 | 169篇 |
2020年 | 121篇 |
2019年 | 148篇 |
2018年 | 210篇 |
2017年 | 204篇 |
2016年 | 202篇 |
2015年 | 188篇 |
2014年 | 229篇 |
2013年 | 461篇 |
2012年 | 264篇 |
2011年 | 323篇 |
2010年 | 316篇 |
2009年 | 240篇 |
2008年 | 155篇 |
2007年 | 131篇 |
2006年 | 92篇 |
2005年 | 41篇 |
2004年 | 54篇 |
2003年 | 50篇 |
2002年 | 57篇 |
2001年 | 38篇 |
2000年 | 43篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 30篇 |
1996年 | 26篇 |
1995年 | 24篇 |
1994年 | 20篇 |
1993年 | 29篇 |
1992年 | 25篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1985年 | 23篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 43篇 |
1980年 | 29篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 34篇 |
1975年 | 25篇 |
1974年 | 20篇 |
1973年 | 23篇 |
排序方式: 共有4561条查询结果,搜索用时 0 毫秒
71.
We have found experimentally that rf SQUID's working in a nonhysteretic mode with small critical currents give exactly at resonance and at very low rf bias a triangular pattern with a period equal to half of one elementary quantum of magnetic flux. We discuss a possible explanation of this peculiar result. 相似文献
72.
B. Dimčić I. Cvijović M. T. Jovanović D. Božić O. Dimčić 《Journal of Materials Science》2006,41(13):4307-4313
This work considers structural and compression mechanical properties of three Ti3Al-based alloys processed by powder metallurgy. Mechanically alloyed powders were compacted by hot-pressing to non-porous
homogenous compacts. Prior to compression tests, all compacts were homogenized by a solution treatment at 1050°C (α + β region)
for 1h, followed by water quenching. The compression tests were performed from room temperature to 500°C in vacuum at a strain
rate of 2.4 × 10−3 s−1. Detailed microstructural characterization has been evaluated by scanning electron microscopy (SEM), followed by electron
dispersive spectroscopy (EDS) and X-ray diffraction analysis. Fracture topography was examined by SEM. The Ti3Al-Nb alloy exhibits the highest ductility in the whole temperature range, whereas addition of Mo to Ti3Al-Nb alloy yields the highest ultimate compression strength. A correlation between ductility and the fracture mode exists
for all materials. 相似文献
73.
Stones belong to porous materials where water in pores plays an important role during the freeze–thaw process. A thermophysical analysis based on the pulse transient method has been used to study an ageing cycle, namely the freeze–thaw cycle. Thermophysical analysis is based on measuring the thermophysical properties under specific thermodynamic conditions. The transient method determines the specific heat, thermal diffusivity, and thermal conductivity by a single measurement. A specimen of Sander sandstone was analyzed in both dry and water-saturated states. Typical anomalies of all thermophysical parameters at the freeze–thaw point as well as differences for the dry and saturated states were found. The changes of thermophysical parameters measured when using freeze–thaw cycles correspond to stone ageing. The freeze–thaw cycle can often be encountered in building physics, concrete construction, etcPaper presented at the Seventh Asian Thermophysical Properties Conference, August 23–28, 2004, Hefei and Huangshan, Anhui, P. R. China. 相似文献
74.
Franko Debra L.; Striegel-Moore Ruth H.; Bean Judy; Tamer Robert; Kraemer Helena C.; Dohm Faith-Anne; Crawford Patricia B.; Schreiber George; Daniels Stephen R. 《Canadian Metallurgical Quarterly》2005,24(6):586
Depression in adolescent girls may result in negative consequences in young adulthood. The Center for Epidemiologic Studies Depression Scale (CES-D) was administered to 1,727 Black and White girls ages 16 to 18 years who participated in the National Heart, Lung, and Blood Institute's Growth and Health Study. Three years later, women in the depressed groups were more likely to be current smokers, had attained a lower level of education, and reported lower self-worth relative to the nondepressed group. Body dissatisfaction, eating concerns, and loneliness were greater in the depressed groups. Relative to Black women, White women who were moderately depressed during adolescence reported more health care services utilization in young adulthood. Prevention efforts for depressed adolescents should be broadly focused to improve young adult outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
M. Kočvara 《Structural and Multidisciplinary Optimization》1997,14(4):256-263
We consider the minimum-compliance formulation of the truss topology problem with additional linear constraints on the displacements: the so-called displacement constraints. We propose a new bilevel programming approach to this problem. Our primal goal (upper-level) is to satisfy the displacement constraint as well as possible — we minimize the gap between the actual and prescribed displacement. Our second goal (lower level) is to minimize the compliance — we still want to find the stiffest structure satisfying the displacement constraints. On the lower level we solve a standard truss topology problem and hence we can solve it in the formulation suitable for the fast interior point alogrithms. The overall bilevel problem is solved by means of the so-called implicit programming approach. This approach leads to a nonsmooth optimization problem which is finally solved by a nonsmooth solver. 相似文献
76.
Henny M. Borsboom Tatjana Claasen-Vujčić Harry J. G. Gaykema Toon Mehlkopf 《Magma (New York, N.Y.)》1997,5(1):33-37
The birdcage resonator is frequently used in conventional MRI because of its excellent attributes. Its use in low-field MRI
is restricted to field strengths higher than, for example, 0.1 T, dependent on the size of the coil. This is because of the
intrinsically low inductance value of the birdcage coils. Furthermore, the sensitivity of the birdcage at low field strengths
is significantly lower when compared to, for example, the solenoid. Both problems can be overcome with the multiturn technique
and a novel wound birdcage coil. The quadrature mode wound birdcage coil presented in this paper can be used at frequencies
as low as 100 kHz. Its sensitivity is also increased when compared to the conventional strip-ring birdcage. Homogeneity effective
volume, and methods to increase the resonator bandwidth to match the signal bandwidth are left intact. The latter is a typical
low-field problem. 相似文献
77.
Martina Bečvářová 《NTM》2004,12(1):40-48
The paper describes the Czech project in the history of mathematics which was initiated at the Faculty of Mathematics and
Physics of Charles University in Prague at the end of the eighties of the 20th century. Its main aim is to map the development
of mathematical research in the Czech lands in the second half of the nineteenth and the first half of the twentieth century.
The main result of this project is the production of monographs. These chart out the life and work of some prominent Czech
personalities-mathematicians who have had substantial influence on the development of Czech mathematics. The aim of the project,
the structure of the monographs and the general method are discussed in the paper. 相似文献
78.
V. A. Baranov V. A. Kalinnikov V. V. Karpukhin N. V. Khomutov A. S. Korenchenko S. M. Korenchenko N. P. Kravchuk N. A. Kuchinskii D. A. Mzhaviya A. M. Rozhdestvenskii V. V. Sidorkin Z. B. Tsamalaidze T. Sakhelashvili E. Frlež D. Počanić W. Li R. C. Minehart L. C. Smith W. A. Stephens K. O. H. Ziock W. Bertl R. Horisberger S. Ritt R. Schnyder H. P. Wirtz B. G. Ritchie I. Supek T. Kozlowski 《Instruments and Experimental Techniques》2005,48(2):168-176
The construction and characteristics of the PIBETA spectrometer are described. This spectrometer is designed to implement a program of precise measurement of pion decay + 0 + e
+ + e at the Paul Scherrer Institute (Switzerland). A spherical calorimeter, consisting of 240 crystals of pure CsI scintillator and embracing a solid angle of 3, is the main detector of the setup. In addition, the spectrometer is composed of an active collimator (which also acts as a beam degrader), a segmented active plastic target, two multiwire cylindrical proportional chambers, a 20-element cylindrical plastic hodoscope, and veto counters of cosmic muons.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 39–48.Original Russian Text Copyright © 2005 by Baranov, Kalinnikov, Karpukhin, Khomutov, A. Korenchenko, S. Korenchenko, Kravchuk, Kuchinskii, Mzhaviya, Rozhdestvenskii, Sidorkin, Tsamalaidze, Sakhelashvili, Frlez, Poanic, Li, Minehart, Smith, Stephens, Ziock, Bertl, Horisberger, Ritt, Schnyder, Wirtz, Ritchie, Supek, Kozlowski. 相似文献
79.
Kaisa Grönman Risto Soukka Terhen Järvi‐Kääriäinen Juha‐Matti Katajajuuri Mika Kuisma Heta‐Kaisa Koivupuro Margareetta Ollila Marja Pitkänen Olli Miettinen Frans Silvenius Rabbe Thun Helena Wessman Lassi Linnanen 《Packaging Technology and Science》2013,26(4):187-200
The environmental impacts of packages have been found to be relatively small compared with the food items they contain. Furthermore, from the environmental and operational point of view, the most significant task of the package is to protect the product, which is important to acknowledge in the packaging design process. This study introduces a guiding framework for designing sustainable food packaging. In this approach, the entire life cycle of the product–package combination is taken into consideration. The emphasis is on the prevention of food losses in packaging design as a major environmental criterion. Consideration of the properties of both the package and the product itself when designing the final package will lead to a better end result with smaller product losses and environmental impacts. By using different assessment methods in the different stages of the packaging design, the sustainability of the package can be enhanced. The decision making of the packaging designer is facilitated with methods that are introduced step by step and in a certain order that will also allow for corrective measures through back‐loops in the design process. The purpose is to integrate sustainability aspects at all stages firmly into the design process. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
80.
Nataša Djordjević Filijović Aleksandar Pavlović Ivan Vučković Katarina Nikolić Danica Agbaba 《Drug development and industrial pharmacy》2015,41(3):502-514
Stress stability testing represents an important part of the drug development process. It is used as an important tool for the identification of degradation products and degradation pathways, as well as for the assessment of changes in physical form of drug molecules. The impact of excipients on the stability of olanzapine confirms that levels of impurities and degradants are limiting parameters and are therefore used for stability evaluation. The major degradation product of olanzapine was identified as 2-methyl-5,10-dihydro-4H-thieno[2,3-b][1,5]benzodiazepine-4-one (III). The structure of III was determined by using LC-MS, IR and NMR. Compatibility and stress stability results demonstrated that tablet formulations of olanzapine are sensitive to temperature and moisture. In samples protected from moisture, the increase in concentration of III was shown to be highly temperature dependent and the degradation followed zero-order kinetics. In addition, studies of olanzapine with excipients and in formulated tablets revealed polymorphic phase changes in some samples, influenced by a combination of stress temperature and humidity conditions. Polymorphic transitions were monitored using x-ray powder diffraction (XRPD) analysis and exhibited no correlation between the phase change (appearance of a new polymorph) and the degradation process. 相似文献