全文获取类型
收费全文 | 44551篇 |
免费 | 2826篇 |
国内免费 | 1638篇 |
专业分类
电工技术 | 2453篇 |
综合类 | 2039篇 |
化学工业 | 8769篇 |
金属工艺 | 1669篇 |
机械仪表 | 2160篇 |
建筑科学 | 828篇 |
矿业工程 | 670篇 |
能源动力 | 8484篇 |
轻工业 | 4346篇 |
水利工程 | 265篇 |
石油天然气 | 957篇 |
武器工业 | 135篇 |
无线电 | 4902篇 |
一般工业技术 | 3730篇 |
冶金工业 | 1306篇 |
原子能技术 | 583篇 |
自动化技术 | 5719篇 |
出版年
2024年 | 103篇 |
2023年 | 799篇 |
2022年 | 1978篇 |
2021年 | 2279篇 |
2020年 | 1494篇 |
2019年 | 1416篇 |
2018年 | 1126篇 |
2017年 | 1450篇 |
2016年 | 1390篇 |
2015年 | 1407篇 |
2014年 | 2471篇 |
2013年 | 2653篇 |
2012年 | 2920篇 |
2011年 | 4049篇 |
2010年 | 3033篇 |
2009年 | 2896篇 |
2008年 | 2779篇 |
2007年 | 2769篇 |
2006年 | 2380篇 |
2005年 | 1806篇 |
2004年 | 1439篇 |
2003年 | 1165篇 |
2002年 | 1021篇 |
2001年 | 777篇 |
2000年 | 600篇 |
1999年 | 483篇 |
1998年 | 399篇 |
1997年 | 318篇 |
1996年 | 250篇 |
1995年 | 214篇 |
1994年 | 195篇 |
1993年 | 153篇 |
1992年 | 106篇 |
1991年 | 91篇 |
1990年 | 71篇 |
1989年 | 79篇 |
1988年 | 47篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 41篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 37篇 |
1981年 | 30篇 |
1980年 | 88篇 |
1979年 | 20篇 |
1977年 | 11篇 |
1975年 | 8篇 |
1973年 | 9篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
D. Helary O. Dugne X. Bourrat P.H. Jouneau F. Cellier 《Journal of Nuclear Materials》2006,350(3):332-335
Electron back-scattering diffraction (EBSD) can be successfully performed on SiC coatings for HTR fuel particles. EBSD grain maps obtained from thick and thin unirradiated samples are presented, along with pole figures showing textures and a chart showing the distribution of grain aspect ratios. This information is of great interest, and contributes to improving the process parameters and ensuring the reproducibility of coatings. 相似文献
82.
Joonyoung Park Sung-Hwan Han S. Senthilarasu Soo-Hyoung Lee 《Solar Energy Materials & Solar Cells》2007,91(8):751-753
Recent studies have reported that a thin interlayer between poly(3, 4-ethylene dioxythiophene)-poly(styrene sulfonic acid) (PEDOT: PSS) and an emissive polymer layer leads to a large increase in the performances of polymer light-emitting diodes (PLEDs) by preventing significant quenching of the radiative excitons at the PEDOT: PSS interface; therefore, acting as an efficient exciton-blocking layer. Using the similar idea, a thin interlayer was fabricated between PEDOT: PSS and the active layer of conjugated polymers/methanofullerene composites in a plastic solar cell. The interlayer consisted of a poly(fluorene)-based hole transporter spin-coated directly on top of the PEDOT: PSS layer. The devices with the interlayer exhibited a higher efficiency than in those without the interlayer. 相似文献
83.
David C. Whitehead Katherine M. Goulden Roy D. Hartley 《Journal of the science of food and agriculture》1985,36(5):311-318
The distribution of 10 nutrient elements was assessed in three fractions of herbage samples of perennial ryegrass, tall fescue, white clover and lucerne. The cell wall fraction, prepared by mechanical disintegration of undried material, contained the following proportions of the total herbage content of the major elements: N, 2.9–16.4%; P, 3.0–6.9%; S, 3.6–17.2%; Ca, 11.3–51.8%; Mg. 6.4–27.6% and K, 0.1–1.7%. Substantial though more variable proportions of the trace element cations, Fe, Mn, Zn and Cu were also present in the cell wall fraction. The extent to which the elements were soluble in water was assessed by analysis of the water-insoluble fraction prepared from freeze-dried samples of each herbage. The proportions of the total herbage content of the major elements soluble in water were: N, 30–57%; P, 80–92%; S, 35–71%; Ca, 48–69%; Mg. 65–83% and K, 90–96%. With the trace element cations the proportions soluble in water were more variable, though they were generally less than 70% of the total. The extent to which the various elements were soluble in 80% aqueous ethanol was assessed by analysis of the insoluble fraction prepared from freeze-dried materials. With each of the major elements, smaller proportions of the total herbage content were soluble in 80% ethanol than in water, which may reflect in part the lower solubility of proteins and pectin. With the trace element cations, the differences in solubility between 80% ethanol and water were generally small and inconsistent. 相似文献
84.
CDC15, an essential cell cycle gene in Saccharomyces cerevisiae, encodes a protein kinase domain 总被引:17,自引:0,他引:17
The cell division cycle gene CDC15 is essential for the late nuclear division in the yeast Saccharomyces cerevisiae. The amino acid sequence of the 974 amino acids/110 kDa CDC15 gene product, as deduced from the nucleotide sequence, includes an aminoterminal protein kinase domain which contains a primary sequence mosaic showing patterns specific for protein serine/threonine kinases besides those for protein tyrosine kinases. Many protein kinases non-essential for growth are known. CDC15 represents an essential protein kinase like CDC7 and CDC28. A carboxyterminal deletion of 32 amino acids renders the protein inactive. 相似文献
85.
A three-dimensional (3D), two-phase, isothermal model of direct methanol fuel cells (DMFCs) was employed to investigate effects of electron transport through the backing layer and the land in bipolar plates. It was found that the electronic resistance of the backing layer, affected by backing layer electronic conductivity, backing layer thickness and flow channel width, played a relatively important role in determining the current density distribution and cell performance. In order to ignore the electron transport effect on the average current density, the minimum electronic conductivity of the backing layer has to be 1000 S m−1, with the relative error in the average current density less than 5%, under the given conditions. 相似文献
86.
The feasibility of a new alloy design concept utilizing the principle of ‘tungsten bronze effect’ is critically evaluated for the development of metallic bipolar plates for proton exchange membrane fuel cell (PEMFC). An austenitic stainless steel (ASS) is modified with W and La to improve the stability of the passive film in an acidic environment as well as to reduce the contact resistance by the tungsten bronze effect. The experimental ASS containing W and La was evaluated in a simulated PEMFC environment of H3PO4 and H2SO4 solutions at 80 °C, and the electrical property was evaluated by performing a contact resistance test. The test results show that the ASS modified with W and La has good passive film stability for corrosion resistance and low contact resistance. The X-ray photoelectron spectroscopy (XPS) analysis clearly suggests the possibility of the tungsten bronze effect from the change in valency state of W6+ to W5+ in the passive film formed on the modified ASS. The feasibility of a new alloy design concept utilizing the ‘tungsten bronze effect’ is well demonstrated; however, more study is highly required for the development of metallic bipolar plates of PEMFC. 相似文献
87.
88.
To study the conservation of peroxisomal targeting signals, we have determined the intracellular localization of human peroxisomal catalase when expressed in yeast. Using immunofluorescence, differential centrifugation and immunoelectron microscopy, we show that the protein is targeted to the peroxisomes of the heterologous cell and assembled in its active tetrameric form. These data show the conservation of the catalase targeting signal and import specificity between human and yeast peroxisomes. 相似文献
89.
本文以国产单滴行列式制瓶机为研究对象,对行列式制瓶机使用技术、维修技术进行较为全面的论述,探讨以提高行列式制瓶机完好率和利用率,降低故障停机时间,提高企业经济效益为目的的行列式制瓶机技术管理模式。 相似文献
90.