全文获取类型
收费全文 | 7957篇 |
免费 | 334篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 51篇 |
综合类 | 6篇 |
化学工业 | 840篇 |
金属工艺 | 218篇 |
机械仪表 | 315篇 |
建筑科学 | 55篇 |
能源动力 | 158篇 |
轻工业 | 361篇 |
水利工程 | 17篇 |
石油天然气 | 3篇 |
无线电 | 851篇 |
一般工业技术 | 956篇 |
冶金工业 | 3873篇 |
原子能技术 | 61篇 |
自动化技术 | 536篇 |
出版年
2023年 | 67篇 |
2022年 | 69篇 |
2021年 | 134篇 |
2020年 | 103篇 |
2019年 | 114篇 |
2018年 | 169篇 |
2017年 | 149篇 |
2016年 | 167篇 |
2015年 | 126篇 |
2014年 | 230篇 |
2013年 | 303篇 |
2012年 | 286篇 |
2011年 | 342篇 |
2010年 | 230篇 |
2009年 | 272篇 |
2008年 | 222篇 |
2007年 | 199篇 |
2006年 | 198篇 |
2005年 | 159篇 |
2004年 | 147篇 |
2003年 | 139篇 |
2002年 | 118篇 |
2001年 | 105篇 |
2000年 | 71篇 |
1999年 | 194篇 |
1998年 | 1370篇 |
1997年 | 740篇 |
1996年 | 456篇 |
1995年 | 284篇 |
1994年 | 227篇 |
1993年 | 273篇 |
1992年 | 57篇 |
1991年 | 56篇 |
1990年 | 57篇 |
1989年 | 44篇 |
1988年 | 33篇 |
1987年 | 55篇 |
1986年 | 36篇 |
1985年 | 27篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 66篇 |
1976年 | 114篇 |
1975年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有8301条查询结果,搜索用时 31 毫秒
101.
102.
103.
104.
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
105.
In this study, we discuss the composition effect of 240 nm and 1.56 μm-silica particles on strength and fracture toughness
by examining two parameters, fragility and glass transition temperature, that were derived from the thermo-viscoelasticity
measurements. Experimental results showed that the composites had a lower fragility with higher strength and fracture toughness
as the content of nanoparticles was increased regardless of glass transition temperature. The improvement in mechanical properties
from adding nanoparticles was definitely explained by the fragility represented the heterogeneity in polymer matrix, and this
was related to the interaction between particles and matrix. The fragility was found to be an effective parameter for evaluating
strength and fracture toughness of epoxy composite containing a bidispersion of nano and micron-silica particles. 相似文献
106.
107.
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
108.
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
109.
110.