全文获取类型
收费全文 | 3035篇 |
免费 | 219篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 30篇 |
综合类 | 8篇 |
化学工业 | 665篇 |
金属工艺 | 83篇 |
机械仪表 | 58篇 |
建筑科学 | 70篇 |
矿业工程 | 5篇 |
能源动力 | 182篇 |
轻工业 | 406篇 |
水利工程 | 34篇 |
石油天然气 | 14篇 |
无线电 | 306篇 |
一般工业技术 | 567篇 |
冶金工业 | 358篇 |
原子能技术 | 22篇 |
自动化技术 | 455篇 |
出版年
2024年 | 7篇 |
2023年 | 40篇 |
2022年 | 64篇 |
2021年 | 121篇 |
2020年 | 75篇 |
2019年 | 86篇 |
2018年 | 147篇 |
2017年 | 157篇 |
2016年 | 136篇 |
2015年 | 89篇 |
2014年 | 133篇 |
2013年 | 243篇 |
2012年 | 174篇 |
2011年 | 223篇 |
2010年 | 146篇 |
2009年 | 142篇 |
2008年 | 113篇 |
2007年 | 100篇 |
2006年 | 90篇 |
2005年 | 62篇 |
2004年 | 77篇 |
2003年 | 64篇 |
2002年 | 29篇 |
2001年 | 26篇 |
2000年 | 31篇 |
1999年 | 46篇 |
1998年 | 92篇 |
1997年 | 73篇 |
1996年 | 57篇 |
1995年 | 47篇 |
1994年 | 40篇 |
1993年 | 33篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 26篇 |
1989年 | 11篇 |
1988年 | 17篇 |
1987年 | 21篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1974年 | 8篇 |
1973年 | 8篇 |
排序方式: 共有3263条查询结果,搜索用时 10 毫秒
1.
2.
Prof. Dr. Britto S. Sandanaraj Pavankumar Janardhan Bhandari Mullapudi Mohan Reddy Akshay Bhagwan Lohote Dr. Bankanidhi Sahoo 《Chembiochem : a European journal of chemical biology》2020,21(3):408-416
The custom design of protein–dendron amphiphilic macromolecules is at the forefront of macromolecular engineering. Macromolecules with this architecture are very interesting because of their ability to self-assemble into various biomimetic nanoscopic structures. However, to date, there are no reports on this concept due to technical challenges associated with the chemical synthesis. Towards that end, herein, a new chemical methodology for the modular synthesis of a suite of monodisperse, facially amphiphilic, protein–dendron bioconjugates is reported. Benzyl ether dendrons of different generations (G1–G4) are coupled to monodisperse cetyl ethylene glycol to form macromolecular amphiphilic activity-based probes (AABPs) with a single protein reactive functionality. Micelle-assisted protein labeling technology is utilized for site-specific conjugation of macromolecular AABPs to globular proteins to make monodisperse, facially amphiphilic, protein–dendron bioconjugates. These biohybrid conjugates have the ability to self-assemble into supramolecular protein nanoassemblies. Self-assembly is primarily mediated by strong hydrophobic interactions of the benzyl ether dendron domain. The size, surface charge, and oligomeric state of protein nanoassemblies could be systematically tuned by choosing an appropriate dendron or protein of interest. This chemical method discloses a new way to custom-make monodisperse, facially amphiphilic, protein–dendron bioconjugates. 相似文献
3.
4.
Tek Bahadur Gurung Ram Prasad Dhakal Jay Dev Bista 《Lakes & Reservoirs: Research and Management》2006,11(3):141-148
The seasonal patterns of phytoplankton primary production, chlorophyll‐a concentration, cell number and several other limnological variables in Lake Phewa, located in the active monsoon zone in Central Himalaya, Nepal, were studied for a year beginning in April 2001. During the study period, the gross primary production and chlorophyll‐a concentrations were relatively low during the monsoon season. The phytoplankton cell number, represented by 24 genera, also fluctuated seasonally, but tended to increase in the pre‐ and post‐monsoon period. These results suggest that the monsoon plays a crucial role in the primary production and phytoplankton dynamics for Lake Phewa. Among the phytoplankton species, Microcystis aeruginosa, a representative species for eutrophic lakes, was the dominant phytoplankton. At the same time, however, it is clear that the lake is not yet heavily eutrophic. The present study suggests that the exchange of lake water during the monsoon season contributes to maintaining the health of the lake against further degradation. Nevertheless, the silt carried in the monsoon rain run‐off from the lake's catchment area suggests increasingly serious degradation problems for this small mountainous lake. 相似文献
5.
K.P. Pipe R.J. Ram 《Photonics Technology Letters, IEEE》2003,15(4):504-506
By measuring the total energy flow from an optical device, we can develop new design strategies for thermal stabilization. Here we present a comprehensive model for heat exchange between a semiconductor laser diode and its environment that includes the mechanisms of conduction, convection, and radiation. We perform quantitative measurements of these processes for several devices, deriving parameters such as a laser's heat transfer coefficient, and then demonstrate the feasibility of thermal probing for the nondestructive wafer-scale characterization of optical devices. 相似文献
6.
A comprehensive study of hazelnut oil composition with comparisons to other vegetable oils,particularly olive oil. 总被引:4,自引:0,他引:4
Benitez-Sánchez Pedro Luis León-Camacho Manuel Aparicio Ramón 《European Food Research and Technology》2003,218(1):13-19
Crude and refined hazelnut oils from different countries were characterised by major and minor compounds. Fatty acids, triacylglycerides, waxes, sterols, methyl-sterols, terpenic and aliphatic alcohols, tocopherols, tocotrienols and hydrocarbons were identified and quantified by gas chromatography and high-performance liquid chromatography. The levels of these chemical compounds in hazelnut oils together with the equivalent carbon numbers and triacylglyceride carbon numbers, were compared with the results of analyses of samples of other vegetable oils. The statistical procedure of cluster analysis was used to characterise hazelnut oils versus other edible oils. 相似文献
7.
8.
A. K. Srivastava Ram M. Shrestha S. C. Srivastava Rabin Shrestha Dharam Paul 《国际能源研究杂志》2003,27(7):671-685
The power sector in India at present comprises of five separate regional electricity grids having practically no integrated operation in between them. This study analyses the utility planning, environmental and economical effects of integrated power sector development at the national level in which the regional electric grids are developed and operated as one integrated system. It also examines the effects of selected CO2 emission reduction targets in the power sector and the role of renewable power generation technologies in India. The study shows that the integrated development and operation of the power system at the national level would reduce the total cost including fuel cost by 4912 million $, total capacity addition by 2784 MW, while the emission of CO2, SO2 and NOx would be reduced by 231.6 (1.9%), 0.8 (0.9%), 0.4 (1.2%) million tons, respectively, during the planning horizon. Furthermore, the study shows that the expected unserved energy, one of the indices of generation system reliability, would decrease to 26 GWh under integrated national power system from 5158 GWh. As different levels of CO2 emission reduction targets were imposed, there is a switching of generation from conventional coal plants to gas fired plants, clean coal technologies and nuclear based plants. As a result the capacity expansion cost has increased. It was found that wind power plant is most attractive and economical in the Indian perspective among the renewable options considered (Solar, wind and biomass). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
Ram Bilas 《Bulletin of Materials Science》1993,16(2):109-116
X-ray diffraction, electron paramagnetic resonance, microwave absorption and resistivity measurements were carried out on
YBa2−x
Bi
x
Cu3O7 (0≤x≤0·5) superconductors in order to study the effect of bismuth on the structural and superconducting properties. A decrease
in sintering temperature increased the amount of impurity phase. Transition from an orthorhombic (superconducting) phase to
tetragonal structure produced no significant change in EPR zero-field signal at liquid nitrogen temperature (LNT). The non-resonance
signal height decreased on higher concentration of bismuth. Sintered YBa2−x
Bi
x
Cu3O7 superconductor had a strong EPR zero-field signal at LNT. We have evaluated particle size from XRD and EPR studies. The average
particle size was about 0·4μm. 相似文献
10.
Corrosion rates were measured at the exposed spots of rebars near three corners of Muddy Creek Bridge located in northern West Virginia using a 3LP device. Also, chloride contents of the concrete samples taken from the vicinity of the spots were analyzed using a wet chemical method that had been developed in this study. The average corrosion rate over the three spots was 4.66 mA/m2, which is in the range of corrosion damage possible in 10–15 years. The average chloride content of the concrete over the three spots was 703 parts per million (ppm), which is well above the threshold limit value of 260 ppm. Although the corrosion rate measurement method using a 3LP device is by manual operation, it is found to be reliable and effective, and, thus, recommended for future studies of this kind of research. The wet chemical method developed in this study is found to be effective. 相似文献