全文获取类型
收费全文 | 15943篇 |
免费 | 1571篇 |
国内免费 | 630篇 |
专业分类
电工技术 | 934篇 |
技术理论 | 2篇 |
综合类 | 906篇 |
化学工业 | 2790篇 |
金属工艺 | 980篇 |
机械仪表 | 1022篇 |
建筑科学 | 1211篇 |
矿业工程 | 546篇 |
能源动力 | 467篇 |
轻工业 | 1046篇 |
水利工程 | 278篇 |
石油天然气 | 1218篇 |
武器工业 | 108篇 |
无线电 | 1788篇 |
一般工业技术 | 2028篇 |
冶金工业 | 836篇 |
原子能技术 | 150篇 |
自动化技术 | 1834篇 |
出版年
2024年 | 29篇 |
2023年 | 350篇 |
2022年 | 483篇 |
2021年 | 745篇 |
2020年 | 613篇 |
2019年 | 508篇 |
2018年 | 587篇 |
2017年 | 595篇 |
2016年 | 500篇 |
2015年 | 687篇 |
2014年 | 843篇 |
2013年 | 906篇 |
2012年 | 1034篇 |
2011年 | 1071篇 |
2010年 | 928篇 |
2009年 | 907篇 |
2008年 | 922篇 |
2007年 | 771篇 |
2006年 | 805篇 |
2005年 | 670篇 |
2004年 | 532篇 |
2003年 | 439篇 |
2002年 | 430篇 |
2001年 | 365篇 |
2000年 | 336篇 |
1999年 | 394篇 |
1998年 | 292篇 |
1997年 | 275篇 |
1996年 | 238篇 |
1995年 | 213篇 |
1994年 | 170篇 |
1993年 | 120篇 |
1992年 | 101篇 |
1991年 | 64篇 |
1990年 | 61篇 |
1989年 | 43篇 |
1988年 | 27篇 |
1987年 | 25篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
61.
62.
Peng Hou Sali Cao Tao Zhang Zhengjun Cai Juanjuan Liu 《Drug development and industrial pharmacy》2015,41(2):263-271
The goal of this study was to enhance the absorption of a new water-insoluble antitumor lead compound, T-OA (3β-hydroxyolea-12-en-28-oic acid-3, 5, 6-trimethylpyrazin-2-methyl ester). Early-stage preparation discovery concept (EPDC) was employed in this study. Based on this concept, a microemulsion system was chosen as the method of improving bioavailability. The solubility of T-OA was checked in different oils, surfactants and cosurfactants. Ternary phase diagrams were constructed to evaluate the microemulsion domain. Developed high-performance liquid chromatography method was used to determine drug content. The transparent o/w microemulsion formulation composed of oleic acid (oil), Tween 80 (surfactant), ethanol (co-surfactant) and water enhanced the solubility of T-OA up to 20?mg/mL. It was characterized in terms of appearance, content, viscosity, zeta potential, conductivity, morphology and particle size. The particle size distribution, viscosity, conductivity and zeta potential were found to be 70?nm, 15.57?MPa?s, 44.1?μS?cm?1 and ?0.174, respectively. Oral bioavailability of T-OA microemulsion and oleic acid solution were checked by using rat model. Contrast to the solid dispersion and proto drug, the area-under-the-curve (AUC) of T-OA microemulsion and oleic acid solution were significantly enhanced. The relative bioavailability of T-OA microemulsion was found to be 5654.7%, which is 57-fold higher than the pure drug. Improved T-OA solubility in microemulsion was found sustained 48?h in dilution study. While the solid dispersion may precipitate under the gastrointestinal circumstance based on dilution results. The in-vivo and in-vitro results indicated that, compare to improve the solubility, it is more important to maintain and prolong the T-OA dissolved status, for improvement of the in-vivo absorption. 相似文献
63.
Iron‐mediated activators generated by electron transfer for atom‐transfer radical polymerization of methyl methacrylate using ionic liquid as ligand and Fe(0) wire as reducing agent 下载免费PDF全文
Liangjiu Bai Suqi Huang Wenxiang Wang Hui Xu Hou Chen Yuzhong Niu Minghua Wang 《Polymer International》2015,64(12):1754-1761
1‐Butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) as a typical ionic liquid (IL) effectively acted as ligand for the control of iron‐mediated activators generated by electron transfer for atom‐transfer radical polymerization of methyl methacrylate (MMA) in the presence of a limited amount of oxygen, using FeCl3.6H2O as the catalyst and Fe(0) wire as the reducing agent. The polymers obtained with BMIMPF6 had controlled molecular weights and low Mw/Mn values (<1.40). Moreover, a well‐defined final product PMMA without additional processing was easily obtained and the reducing agent (iron wire) could be recycled and reused effectively just by washing three times with solvents. 相似文献
64.
65.
为实现气化灰综合利用和降低腻子粉制备成本,研究了利用气化灰替代水泥制备腻子粉的技术可行性。以气化灰和 42.5水泥为主要原料,配以少量的羟丙基甲基纤维素和可分散性乳胶粉,制备气化灰基腻子粉,实验考察原料配方变化对腻子粉的性能影响。研究结果表明:利用气化灰替代水泥制品制备腻子粉具有可行性。其中,气化灰替代 50%水泥时,腻子粉的粘结强度为 0.82 Mpa,各项性能均优于建筑外墙用腻子粉标准 JG/T 157—2009要求。在相同条件下,气化灰替代不超过 70%的水泥时,腻子粉的粘结强度及其他指标均满足建筑外墙用腻子粉标准 JG/T 157—2009要求。 相似文献
66.
67.
Microstructural evolution and densification behavior of porous kaolin-based mullite ceramic added with MoO3 were investigated. The results indicated that MoO3 addition not only lowered the secondary mullitization temperature to below 950?°C, but also facilitated effectively the anisotropic growth of mullite grains. Fine mullite whiskers grew and interlocked with one another in the pre-existing pore regions, in-situ forming a stiff 3D skeleton structure of mullite whiskers, which arrested further densification of the sample. On the other hand, due to the great capillary attraction of small pores, the liquid phase tended to spread over small grains, which favored the growth from small mullite grains into whiskers at the expense of the liquid phase. Consequently, competitive mechanisms of sintering and crystal growth of mullite functioned, which further limited the sample densification. As a result, the total linear shrinkage of the sample added with MoO3 after firing at 1400?°C was only ??2.75%, and its porosity was retained at as high as 67%. 相似文献
68.
Bin Li Guangqi Li Junhong Chen Haiyang Chen Xinming Xing Xinmei Hou Yong Li 《Ceramics International》2018,44(8):9395-9400
Elongated β–Si3N4 crystals have a significant influence on the mechanical property of Fe–Si3N4 composite. In this paper, the formation mechanism of elongated β–Si3N4 crystals in Fe–Si3N4 composite was investigated. During the preparation process, β–Si3N4 crystals developed in a spiral and layer growth mechanism in the dense areas. They kept growing from the dense areas and formed radially distributed elongated crystals with hexagonal prismatic morphology as time went on. As for the formation mechanism, the (100) crystal plane of β–Si3N4 from Si-N-O melt is mainly the vicinal crystal planes growth with different angles from the (100) crystal plane. At the later stage, the crystallization and the diffusion forces in Si-N-O molten phase decreased. However, the short range diffusion remained active and resulted in the gradient distribution of N content near the boundary. With the temperature decreasing, the disappearance of the short range diffusion implied the end of the crystallization process of the elongated β–Si3N4 crystals. 相似文献
69.
Crystal Structures and Phase Behavior of Sulfadiazine and a Method for the Preparation of Aggregates with Good Performance 下载免费PDF全文
Songgu Wu Shichao Du Mingyang Chen Kangli Li Lina Jia Dejiang Zhang Estevao G. J. Macaringue Baohong Hou Junbo Gong 《化学工程与技术》2018,41(3):532-540
The solvate and the solvent‐free form of sulfadiazine (SD) were investigated. SD was found to exist in one solvent‐free form and the N‐methylpyrrolidone (NMP) solvate form. The NMP solvate was shown to be a channel‐type compound. The intrinsic properties of the solvents were used to evaluate the effects of solubility on the phase transformation of SD and the NMP solvate. The SD phase could transform to the NMP solvate by NMP‐mediated phase transformation, which was governed by crystallization of the NMP solvate. The crystalline NMP solvate could transform to the solvent‐free solid state through solid‐solid transformation upon heating or water penetration‐mediated phase transformation. The rate of this water penetration‐mediated phase transformation of the NMP solvate to SD was unusually fast. It can be used to obtain SD aggregates of well‐defined shape and good powder properties. 相似文献
70.
Salim Hengky K. Padfield Rory Lee Chew Tin Syayuti Khadijah Papargyropoulou Effie Tham Mun Hou 《Clean Technologies and Environmental Policy》2018,20(3):529-538
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food... 相似文献