全文获取类型
收费全文 | 397篇 |
免费 | 18篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 86篇 |
金属工艺 | 33篇 |
机械仪表 | 5篇 |
建筑科学 | 10篇 |
能源动力 | 14篇 |
轻工业 | 30篇 |
水利工程 | 6篇 |
无线电 | 11篇 |
一般工业技术 | 104篇 |
冶金工业 | 83篇 |
原子能技术 | 1篇 |
自动化技术 | 30篇 |
出版年
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2017年 | 9篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 9篇 |
2011年 | 29篇 |
2010年 | 24篇 |
2009年 | 25篇 |
2008年 | 22篇 |
2007年 | 17篇 |
2006年 | 18篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 19篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 18篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1963年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有415条查询结果,搜索用时 343 毫秒
131.
Jack W. Reich Victoria Dillon Ursula F. Fritsch Karen K. Church 《Drug development and industrial pharmacy》1987,13(4):739-802
This paper examines in detail the Waxman/Hatch Act and the NDA Rewrite, from both an implementation point of view and from a world-wide research and development perspective. The central theme of these regulatory changes appears to be consistent with U.S. drug policy of the past two decades, i.e., cost containment, primarily, followed by uniformity and efficiency in the regulatory review process. These recent changes, just as the 1962 Drug Ammendments 22 years earlier, will continue to have profound effects upon the sites at which pharmaceutical research and development is carried out. 相似文献
132.
133.
The radiation initiated grafting of N-vinylpyrrolidone (NVP) onto copolymers of vinyl fluoride/vinylidene fluoride (VF/VF2) with compositions of 75/25 mol-%, 50/50 mol-% and 20/80 mol-% VF/VF2 has been investigated. The active species, initiating the grafting, have been created by accelerated electrons (160 keV) applying preirradiation technique in vacuo. The time conversion curves present a characteristic temperature dependence. Increasing grafting temperature rises the initial grafting rate. The final (saturation) grafting yield increases with temperature up to 333 K, and then declines. This behaviour was described by the influences of glass transition on the rate of termination in the semicrystalline trunk polymers. The grafting rate (at constant irradiation dose and grafting temperature) decreases with increasing VF2 content in the copolymers. The reason is discussed by means of a semiquantitative mathematical analysis of the graft kinetics applying “non-steady-state”-conditions. The grafting rate does not depend on dose rate, but strongly depends on irradiation dose passing a maximum. This maximum has been interpreted by means of “Differential-Interference-Contrast”-microscopy. The enthalpies of melting ΔHm of the semicrystalline copolymers decrease after grafting with increasing grafting yield. This change is due to the partial destroying of crystalline regions in the trunk copolymers caused by stresses arising from grafted polymer chains. The membrane resistance of films grafted through is <10 Ω cm2. The membranes proved to be permeable for urea. 相似文献
134.
Die Sauerstoffdrücke im System Mn3O4-MnO-O2. Beschreibung einer Versuchsanordnung zur statischen Gleichgewichtsmessung bei hohen Temperaturen. Isothermische Aufbauten und Messung der Zersetzungsdrücke im univarianten Bereich des Systems. Homogenitätsbereiche des MnO und Mn3O4 zwischen 1345 bis 1560 °C. Berechnung der Schmelz- und Erstarrungslinie des MnO. Bestimmung des Eutektikums MnO–Mn3O4. Erörterung zum Schmelzpunkt des Mn3O4. 相似文献
135.
136.
C.E Miller C Basu G Fritsch T Hildebrandt J.R Hutchinson 《Journal of the Royal Society Interface》2008,5(21):465-475
This study quantifies the shape change in elephant manus and pes anatomy with increasing body mass, using computed tomographic scanning. Most manus and pes bones, and manus tendons, maintain their shape, or become more gracile, through ontogeny. Contrary to this, tendons of the pes become significantly more robust, suggesting functional adaptation to increasingly high loads. Ankle tendon cross-sectional area (CSA) scales the highest in the long digital extensor, proportional to body mass(1.08+/-0.21), significantly greater than the highest-scaling wrist tendon (extensor carpi ulnaris, body mass(0.69+/-0.09)). These patterns of shape change relate to the marked anatomical differences between the pillar-like manus and tripod-like pes, consistent with differences in fore- and hindlimb locomotor function. The cartilaginous predigits (prepollux and prehallux) of the manus and pes also become relatively more robust through ontogeny, and their pattern of shape change does not resemble that seen in any of the 10 metacarpals and metatarsals. Their CSAs scale above isometry proportional to body mass(0.73+/-0.09) and body mass(0.82+/-0.07) respectively. We infer a supportive function for these structures, preventing collapse of the foot pad during locomotion. 相似文献
137.
Wen Ma Daniel E. Mack Robert Vaßen Detlev Stöver 《Journal of the American Ceramic Society》2008,91(8):2630-2635
Perovskite-type SrZrO3 was investigated as an alternative to yttria-stabilized zirconia (YSZ) material for thermal barrier coating (TBC) applications. Three phase transformations (orthorhombic↔pseudo-tetragonal↔tetragonal↔cubic) were found only by heat capacity measurement, whereas the phase transformation from orthorhombic to pseudo-tetragonal was found in thermal expansion measurements. The thermal expansion coefficients (TECs) of SrZrO3 coatings were at least 4.5% larger than YSZ coatings up to 1200°C. Mechanical properties (Young's modulus, hardness, and fracture toughness) of dense SrZrO3 showed lower Young's modulus, hardness, and comparable fracture toughness with respect to YSZ. The "steady-state" sintering rate of a SrZrO3 coating at 1200°C was 1.04 × 10−9 s−1 , which was less than half that of YSZ coating at 1200°C. Plasma-sprayed coatings were produced and characterized. Thermal cycling with a gas burner showed that at operating temperatures ∼1250°C the cycling lifetime of SrZrO3 /YSZ double-layer coating (DLC) was more than twice as long as SrZrO3 coating and comparable to YSZ coating. However, at operating temperatures >1300°C, the cycling lifetime of SrZrO3 /YSZ DLC was comparable to the optimized YSZ coating, indicating SrZrO3 might be a promising material for TBC applications at higher temperatures compared with YSZ. 相似文献
138.
Mièle A Blanchin N Raynaud P Quesne B Giraud JM Fottorino R Bérard P Ansoborlo E Franck D Blanchardon E Challeton-de Vathaire C Lebaron-Jacobs L Poncy JL Piechowski J Fritsch P 《Radiation protection dosimetry》2007,127(1-4):350-355
A didactic software, MEthodes DOsimètriques de REférence (MEDOR), is being developed to provide help in the interpretation of biological data. Its main purpose is to evaluate the pertinence of the application of different models. This paper describes its first version that is focused on inhalation exposure to actinide aerosols. With this tool, sensitivity analysis on different parameters of the ICRP models can be easily done for aerosol deposition, in terms of activity and particle number, actinide biokinetics and doses. The user can analyse different inhalation cases showing either that dose per unit intake cannot be applied if the aerosol contains a low number of particles or that an inhibition of the late pulmonary clearance by particle transport can occur which contributes to a 3-4 fold increase in effective dose as compared with application of default parameters. This underlines the need to estimate systematically the number of deposited particles, as well as to do chest monitoring as long as possible. 相似文献
139.
Claudia Gerdes Julia Schuppan Arnd-Rüdiger Grimmer Michael Bolte Wolfgang Saak Detlev Haase Thomas Müller 《SILICON》2010,2(4):217-227
The structure and bonding of 7-silanorbornadienes was investigated using X-ray Diffraction (XRD), solid-state NMR spectroscopy
and density functional calculations. The solid state structures of four benzo-7-silanorbornadienes (4a, c, d, e) and of one dibenzo-7-silabenzonorbornadiene (5a) are reported and compared with the results of previous structural investigations. The most prominent features of the molecular
structures of all 7-silanorbornadienes are very long Si-C(bridgehead) bonds (d(SiC) = 190.6–196.8 pm) and very acute CSiC
bond angles α (α(CSiC) = 78.7–83.9°). All newly investigated 7-silanorborndienes show for tetracoordinated silicon nuclei
extremely deshielded 29Si NMR resonances (δ29Si = 65.6–31.6). Solid State NMR investigations for 7-silanorbornadienes anti-4a, b reveal highly anisotropic chemical shift tensors of axial or nearly axial symmetry (4a: δ11 = 161, δ22 = δ33 = −11; 4b: δ11 = 113, δ22 = 14, δ33 = −15). The dominating, strongly deshielding δ11 component is oriented almost perpendicular to the plane spanned by the two bridgehead carbon atoms and the bridging silicon
atom. The DFT calculations suggest that the origin of the strong deshielding is a small energy difference between the frontier
orbitals, which are strongly localized at the silicon atom. In addition the computations reveal that both the long SiC bonds
and the strongly deshielded 29Si NMR chemical shift are direct consequences of the bonding situation in 7-silanorbornadienes which are characterized by
through space interaction of the C=C double bonds and by hyperconjugation between the SiC σ-bonds and the unoccupied orbitals
of the C=C double bonds. 相似文献
140.
This study analyzes the relationship between the specialization of a region in certain industries and the efficiency of the
region in generating new knowledge. The efficiency measure is constructed by relating regional R&D input and output. An inversely
u-shaped relationship is found between regional specialization and R&D efficiency, indicating the presence of externalities
of both Marshall and Jacobs’ type. Further factors influencing efficiency are externalities resulting from high R&D intensity
of the local private sector as well as knowledge from local public research institutions. The impact of both the specialization
and the additional factors is, however, different for regions at different efficiency levels. 相似文献