全文获取类型
收费全文 | 7411篇 |
免费 | 52篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 84篇 |
综合类 | 2篇 |
化学工业 | 414篇 |
金属工艺 | 20篇 |
机械仪表 | 37篇 |
建筑科学 | 45篇 |
矿业工程 | 2篇 |
能源动力 | 25篇 |
轻工业 | 109篇 |
水利工程 | 9篇 |
石油天然气 | 6篇 |
无线电 | 327篇 |
一般工业技术 | 391篇 |
冶金工业 | 5400篇 |
原子能技术 | 29篇 |
自动化技术 | 564篇 |
出版年
2021年 | 26篇 |
2020年 | 18篇 |
2019年 | 26篇 |
2018年 | 26篇 |
2017年 | 31篇 |
2016年 | 20篇 |
2015年 | 26篇 |
2014年 | 23篇 |
2013年 | 134篇 |
2012年 | 64篇 |
2011年 | 78篇 |
2010年 | 85篇 |
2009年 | 85篇 |
2008年 | 94篇 |
2007年 | 71篇 |
2006年 | 80篇 |
2005年 | 70篇 |
2004年 | 48篇 |
2003年 | 81篇 |
2002年 | 76篇 |
2001年 | 67篇 |
2000年 | 55篇 |
1999年 | 232篇 |
1998年 | 1668篇 |
1997年 | 932篇 |
1996年 | 588篇 |
1995年 | 392篇 |
1994年 | 321篇 |
1993年 | 377篇 |
1992年 | 99篇 |
1991年 | 101篇 |
1990年 | 117篇 |
1989年 | 92篇 |
1988年 | 89篇 |
1987年 | 89篇 |
1986年 | 87篇 |
1985年 | 89篇 |
1984年 | 40篇 |
1983年 | 56篇 |
1982年 | 56篇 |
1981年 | 63篇 |
1980年 | 55篇 |
1979年 | 28篇 |
1978年 | 42篇 |
1977年 | 121篇 |
1976年 | 215篇 |
1975年 | 27篇 |
1974年 | 30篇 |
1972年 | 20篇 |
1970年 | 17篇 |
排序方式: 共有7464条查询结果,搜索用时 0 毫秒
71.
72.
High spatial order finite element method to solve Maxwell's equations in time domain 总被引:2,自引:0,他引:2
Pernet S. Ferrieres X. Cohen G. 《Antennas and Propagation, IEEE Transactions on》2005,53(9):2889-2899
This paper presents a finite element method with high spatial order for solving the Maxwell equations in the time domain. In the first part, we provide the mathematical background of the method. Then, we discuss the advantages of the new scheme compared to a classical finite-difference time-domain (FDTD) method. Several examples show the advantages of using the new method for different kinds of problems. Comparisons in terms of accuracy and CPU time between this method, the FDTD and the finite-volume time-domain methods are given as well. 相似文献
73.
74.
Y. Cohen K. Landskron N. Ttreault S. Fournier‐Bidoz B. Hatton G.A. Ozin 《Advanced functional materials》2005,15(4):593-602
The synthesis and characterization of a novel silicon–silica nanocomposite material are reported. A self‐assembly method allows the encapsulation of silicon nanoclusters within the channels of a periodic mesoporous silica thin film. The result is the formation of a silicon–silica nanocomposite film with bright, room‐temperature photoluminescence in the visible range, and a nanosecond luminescence lifetime. The properties of the nanocomposite material have been studied by several analytical techniques, which collectively show the existence within the channels of non‐diamondoid‐structure‐type silicon nanoclusters with various hydrogenated silicon sites. It is estimated that the silicon nanoclusters in the silica mesoporous films occupy up to 39 % of the accessible pore volume. The nanocomposite film shows improved resistance to air oxidation compared to crystalline silicon. The high loading and chemical stability to oxidation under ambient conditions are important advantages in terms of the development of silicon‐based light‐emitting diodes from this class of materials. 相似文献
75.
Cohen Lawrence H.; Burt Charles E.; Bjorck Jeffrey P. 《Canadian Metallurgical Quarterly》1987,23(4):583
A longitudinal design was used to test the effects of life events experienced by young adolescents and their parents. The criteria were the adolescents' depression, anxiety, and self-esteem. The longitudinal analysis revealed a significant effect for the adolescents' controllable, but not uncontrollable, negative events. However, causal analyses revealed that this effect was the result of the significant relation between initial adjustment and the subsequent occurrence of controllable life stress (e.g., school suspension). The longitudinal analysis also revealed the stress-protective role of positive events, but only with respect to girls' self-esteem. There was no longitudinal support for the role of the parents' negative life events. These findings do not support the etiological importance of an accumulation of relatively discrete negative events experienced by early adolescents and their parents, but they do suggest the need (a) to conceptualize (controllable) life stress as a dependent variable in future research on developmental psychopathology; (b) to examine gender differences in early adolescent life stress; and (c) to develop more sophisticated measures of family life stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
77.
Male Swiss-Webster mice were rendered tolerant to morphine by subcutaneous implantation of a morphine pellet, each containing 75 mg morphine base, for 3 days. Mice implanted with placebo pellets served as controls. A high degree of tolerance to the analgesic effect of morphine developed as evidenced by decreased analgesic response to various doses of morphine. A selective kappa-opiate agonist, U-50,488H (8, 16 and 32 mg/kg, i.p.) produced dose-dependent analgesic and hypothermic effects in mice implanted with placebo pellets. A significant decrease in the analgesic and hypothermic effects of U-50,488H was observed in morphine tolerant mice as compared to placebo-treated mice. Mice were rendered tolerant to U-50,488H by injecting the drug (25 mg/kg, i.p.) twice daily for 4 days. Vehicle injected mice served as controls. Tolerance to the analgesic and hypothermic effects of U-50,488H in mice injected chronically with the drug was evidenced by the decreases in the intensity of these responses when compared to those observed in vehicle injected controls. Morphine produced a dose-dependent analgesic and hypothermic effects in mice injected chronically with vehicle but the intensity of these effects was significantly lower in mice injected chronically with U-50,488H. These results indicate that a substantial tolerance to analgesic and hypothermic effects of U-50,488H develops in morphine tolerant mice. The effect of chronic injections of U-50,488H on the binding of [3H]ethylketocyclazocine (EKC) and [3H]D-Ala2,MePhe4,Gly-ol5-enkephalin (DAMGO) to whole brain and spinal cord kappa- and mu-opiate receptors was determined.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
78.
Two studies explored how domestic violence may be implicitly or explicitly sanctioned and reinforced in cultures where honor is a salient organizing theme. Three general predictions were supported: (a) female infidelity damages a man's reputation, particularly in honor cultures; (b) this reputation can be partially restored through the use of violence; and (c) women in honor cultures are expected to remain loyal in the face of jealousy-related violence. Study 1 involved participants from Brazil (an honor culture) and the United States responding to written vignettes involving infidelity and violence in response to infidelity. Study 2 involved southern Anglo, Latino, and northern Anglo participants witnessing a "live" incident of aggression against a woman (actually a confederate) and subsequently interacting with her. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
79.
Tuberculous meningitis remains an important illness that can be difficult to diagnose in a timely fashion and carries significant morbidity. We present a retrospective review of the cases of tuberculous meningitis diagnosed and treated at a single institution. Fifty-eight cases were identified and stratified according to stage of disease at presentation. Four patients (7%) died; three (5%) developed severe neurological sequelae. Poor outcomes were largely confined to cases presenting in an advanced stage and at the extremes of age. Corticosteroids were administered to 56 patients and may have contributed to the comparatively good outcome in these cases. 相似文献
80.
This work utilizes proteoliposomes reconstituted with renal Na(+)-K(+)-ATPase to study effects of electrical potential (40-80 mV) on activation of pump-mediated fluxes of Na+ or Rb+ (K+) ions and on inhibitory effects of Rb+ ions or organic cations. The latter include guanidinium derivatives that are competitive Na(+)-like antagonists (David, P., Mayan, H., Cohen, H., Tal, D. M., and Karlish, S.J.D. (1992) J. Biol. Chem. 267, 1141-1149). Cytoplasmic side-positive diffusion potentials significantly decreased the K0.5 of Na+ at the cytoplasmic surface for activation of ATP-dependent Na(+)-K+ exchange but did not affect the inhibitory potency of Rb+ (K+) or any Na(+)-like antagonist. Diffusion potentials did not affect activation of Rb(+)-Rb+ exchange by Rb+ ions at the cytoplasmic surface and had only a minor effect on Rb+ activation at the extracellular surface. Previously, we proposed that the cation binding domain consists of two negatively charged sites, to which two K+ or two Na+ ions bind, and one neutral site for the third Na+ (Glynn, I. M., and Karlish, S.J.D. (1990) Annu. Rev. Biochem. 59, 171-205). The present experiments suggest that binding of a Na+ ion in the neutral site at the cytoplasmic surface is sensitive to voltage. By contrast, binding of Rb+ ions at the extracellular surface of renal pumps appears to be only weakly or insignificantly affected by voltage. Inferences on the identity of the charge-carrying steps, based on experiments using proteoliposomes, are discussed in relation to recent evidence that dissociation of Na+ or association of K+ ions, at the extracellular surface, represent the major charge-carrying steps. 相似文献