全文获取类型
收费全文 | 75290篇 |
免费 | 452篇 |
国内免费 | 680篇 |
专业分类
电工技术 | 1442篇 |
综合类 | 50篇 |
化学工业 | 11217篇 |
金属工艺 | 3444篇 |
机械仪表 | 2639篇 |
建筑科学 | 1650篇 |
矿业工程 | 504篇 |
能源动力 | 1883篇 |
轻工业 | 6412篇 |
水利工程 | 858篇 |
石油天然气 | 2303篇 |
武器工业 | 41篇 |
无线电 | 7234篇 |
一般工业技术 | 16485篇 |
冶金工业 | 12409篇 |
原子能技术 | 2628篇 |
自动化技术 | 5223篇 |
出版年
2022年 | 580篇 |
2021年 | 926篇 |
2020年 | 743篇 |
2019年 | 840篇 |
2018年 | 1550篇 |
2017年 | 1564篇 |
2016年 | 1778篇 |
2015年 | 945篇 |
2014年 | 1555篇 |
2013年 | 3562篇 |
2012年 | 2356篇 |
2011年 | 2818篇 |
2010年 | 2368篇 |
2009年 | 2641篇 |
2008年 | 2618篇 |
2007年 | 2552篇 |
2006年 | 2182篇 |
2005年 | 1911篇 |
2004年 | 1838篇 |
2003年 | 1788篇 |
2002年 | 1705篇 |
2001年 | 1677篇 |
2000年 | 1671篇 |
1999年 | 1562篇 |
1998年 | 3665篇 |
1997年 | 2598篇 |
1996年 | 1934篇 |
1995年 | 1521篇 |
1994年 | 1325篇 |
1993年 | 1349篇 |
1992年 | 994篇 |
1991年 | 1050篇 |
1990年 | 1071篇 |
1989年 | 1050篇 |
1988年 | 940篇 |
1987年 | 874篇 |
1986年 | 877篇 |
1985年 | 934篇 |
1984年 | 777篇 |
1983年 | 767篇 |
1982年 | 675篇 |
1981年 | 689篇 |
1980年 | 661篇 |
1979年 | 646篇 |
1978年 | 620篇 |
1977年 | 773篇 |
1976年 | 930篇 |
1975年 | 580篇 |
1974年 | 551篇 |
1973年 | 543篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
V. N. Kostin O. N. Vasilenko A. V. Byzov 《Russian Journal of Nondestructive Testing》2018,54(9):654-661
It is shown that by measuring the magnetic field in a specially shaped hole made in the magnetic circuit of a measuring transducer and the tangential component of the magnetic field in the transducer’s interpolar space near the surface of an object being magnetized, it is possible to locally determine the relative values of the magnetic properties of the test-object substance. The physical rationale is provided for a technique that makes it possible to determine the entirety of hysteresis characteristics and significantly expand the ranges of measurement of magnetic properties. The difference is established between the structural sensitivities of magnetic properties locally determined in terms of “flux–internal field” (the properties of matter) and “flux in the product–current in the windings” (the properties of “body”) coordinates. It is shown that it is possible and expedient to simultaneously measure and jointly analyze the magnetic characteristics of matter and “body”. Information is provided on the DIUS-1.15M mobile hardware–software system, intended for implementing single- and multiparameter techniques of monitoring the structure–phase and stress–strain states of ferromagnetic materials and objects based on the proposed measurement procedures. 相似文献
972.
The presentation of high-tech projects (including research and development projects) submitted to funding competitions is considered. Two-stage development of such presentations is proposed. The first step is to ensure that the selected set of characteristics is representative and may be estimated with sufficient precision. The next step is to introduce a mathematically formalized business model of the project, permitting its financial evaluation. This model must adequately and transparently identify the financial potential of the economic cluster that will implement the submitted project. Embodied in software, this model must support stress testing of the high-technology project and optimization of its characteristics. 相似文献
973.
O. V. Ermakova 《Russian Engineering Research》2018,38(6):462-465
Assessment of the difficulty and cost of research and development relating to distributed aviation systems is considered. A problem is that the participants in development projects may assess them subjectively. Analysis of the basic methods used to assess the difficulty and cost of research and development in industry and associated fields reveals their deficiencies. 相似文献
974.
A mechatronic motorized spindle with hydrostatic bearings and a contact-free piezohydraulic generator of resonant axial spindle microoscillations is proposed. The boundary problem is solved for a nonsteady Reynolds equation in laminar motion, with no cavitation of the working fluid. On that basis, analytical formulas are derived for the dynamic-pressure distribution of the working fluid and the dynamic axial force created in the gap of the piezohydraulic generator. 相似文献
975.
S. S. Abdurakipov O. A. Gobyzov M. P. Tokarev V. M. Dulin 《Optoelectronics, Instrumentation and Data Processing》2018,54(5):513-519
A method for automatic determination of combustion regimes using flame images on the basis of a convolutional neural network on labeled data is under consideration. It is shown that the accuracy of regime classification reaches 98% on the flame images of a gas burner. The results of the operation of the convolutional neural network and classification using different linear models are compared. 相似文献
976.
S.?M.?BorzovEmail author O.?I.?Potaturkin 《Optoelectronics, Instrumentation and Data Processing》2018,54(6):582-599
Various methods of spectral-spatial classification of hyperspectral data are reviewed. Papers devoted to the most popular ways of using spatial information for increasing the accuracy of classification maps are considered. It is shown that the best results are obtained by using preprocessing of “raw” data before the procedures of pixel-wise spectral classification. Disadvantages, limits, and possible directions for developing existing methods are investigated and analyzed. 相似文献
977.
M.?A.?Mukutadze E.?O.?Lagunova V.?V.?VasilenkoEmail author 《Journal of Machinery Manufacture and Reliability》2018,47(3):271-277
This work presents a method of formation of an accurate self-similar solution of the problem of hydrodynamic calculation of a wedge-shaped support (slide block, guide) operating in the presence of a lubricating material and melt of the guide. Based on the equation of motion of an viscous incompressible liquid for a “thin layer” and the expression for the energy dissipation rate, an analytical dependence is obtained for the profile of the melted surface of the guide. In addition, the main performance characteristics of the friction couple considered are defined. The influence of the parameter specified by the melt of the guide on the bearing capacity and friction force is estimated. 相似文献
978.
Urea–formaldehyde-bonded wood products are limited to interior nonstructural applications because of their poor durability under cyclic moisture or humid environments. The stability of solid-wood joints and particleboards can be enhanced by bonding with urea–formaldehyde adhesives modified with di- and trifunctional amines at an effective resin formaldehyde-to-urea mol ratio (F/U) of 1.6; however, particleboard formaldehyde emissions were not improved over those from boards made with unmodified adhesives and were unacceptably high. The relative effectiveness of selected modifications was investigated at resin form aldehyde-to-urea (F/U) molar ratios of 1.4 and 1.2 Solid-wood joints and particleboards made with modified adhesives, an unmodified adhesive, and a phenol formaldehyde (PF) resin were subjected to cyclic soak-dry (cyclic stress) treatments and moist-heat aging. Formaldehyde emissions from particleboards were also determined. At F/U 1.4, the resistance of solid-wood joints made with modified adhesives to cyclic stress and moist-heat aging was equal to that of PF-bonded joints and superior to that of joints bonded with unmodified adhesive. The resistance of particleboards made with modified adhesives was greater than that of boards made with unmodified adhesive but less than that of PF-bonded board. Solid-wood joints and particleboards made with F/U 1.4 resins performed better than did those made with F/U 1.2 resins. Particleboards made with F/U 1.2 resins had formaldehyde emissions well below the standard, and room temperature aging or bonding at high temperature reduced emissions substantially. © 1994 John Wiley & Sons, Inc. 1 1 This article is a US Government work and, as such, is in the public domain in the United States of America. 相似文献
979.
J. C. Moreland G. L. Wilkes C. G. Moreland S. S. Sankar E. O. Stejskal R. B. Turner 《应用聚合物科学杂志》1994,52(9):1175-1180
High-resolution solid-state 13C-NMR has been used to study the phase separation and molecular motion in two series of polyurethane foams. These two series differ by one possessing the additive of lithium chloride, LiCl. NMR relaxation times can map the motion throughout the polymer molecule and detect changes in that motion arising from either microseparation or phase mixing between the different segments. There are only slight changes in the soft segment T1p(13C) values as well as an increase in the hard segment T1p(1H) values with increase in the hard segment content for the foams studied. The T1p(1H) and T1p(13C) values do indicate that the phase separation of the hard and soft segments is similar for all foams. A decrease in the T1p(1H) and T1p(13C) values with increasing LiCl content indicates that the motion of the soft segments is restricted more by the hard segments. This is explained by more phase mixing in the foams containing the LiCl additive. © 1994 John Wiley & Sons, Inc. 相似文献
980.
R. M. Holsti-Miettinen J. V. Seppl O. T. Ikkala I. T. Reima 《Polymer Engineering and Science》1994,34(5):395-404
Superior impact properties were obtained when maleic anhydride grafted styrene ethylene/butylene styrene block copolymer (SEBS-g-MAH) was used as a compatibilizer in blends of polyamide 6 (PA 6) and isotactic polypropylene (PP), where polyamide was the majority phase and polypropylene the minority phase. The optimum impact properties were achieved when the weight relation PA:PP was 80:20 and 10 wt% SEBS-g-MAH was added. The blend morphology was systematically investigated. Transmission electron microscopy (TEM) indicated that the compatibilizer forms a cellular structure in the PA phase in addition to acting as an interfacial agent between the two polymer phases. In this cellular-like morphology the compatibilizer appears to form the continuous phase, while polyamide and polypropylene form separate dispersions. In microscopy, PA appeared as a fine dispersion and PP as a coarse dispersion. The mechanical properties indicated that in fact PA, too, is continuous, and the blend can be interpreted as possessing a modified semi-interpenetrating network (IPN) structure with separate secondary dispersion of PP. The coarser PP dispersion plays an essential role in impact modification. Binary blends of the compatibilizer and one blend component were also investigated separately. The same cellular structure was observed in the binary PA/SEBS-g-MAH blends, and SEBS-g-MAH again appeared to form the continuous phase when the elastomer concentration was at least 10 to 20 wt%. By contrast, in PP/SEBS-g-MAH only conventional dispersion of elastomeric SEBS-g-MAH was observed up to 40 wt% elastomer. Impact strength was improved and the elastic modulus was lowered in both PA/SEBS-g-MAH and PP/SEBS-g-MAH blends when the elastomer content was increased. The changes in modulus indicate that the semi-IPN-like structure is formed in the binary PA/SEBS-g-MAH blends as well as in the ternary structure. 相似文献