全文获取类型
收费全文 | 1153篇 |
免费 | 35篇 |
专业分类
电工技术 | 101篇 |
综合类 | 4篇 |
化学工业 | 267篇 |
金属工艺 | 19篇 |
机械仪表 | 32篇 |
建筑科学 | 30篇 |
能源动力 | 79篇 |
轻工业 | 62篇 |
水利工程 | 3篇 |
无线电 | 104篇 |
一般工业技术 | 256篇 |
冶金工业 | 66篇 |
原子能技术 | 31篇 |
自动化技术 | 134篇 |
出版年
2023年 | 4篇 |
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 12篇 |
2016年 | 26篇 |
2015年 | 15篇 |
2014年 | 36篇 |
2013年 | 72篇 |
2012年 | 49篇 |
2011年 | 47篇 |
2010年 | 59篇 |
2009年 | 51篇 |
2008年 | 61篇 |
2007年 | 51篇 |
2006年 | 39篇 |
2005年 | 52篇 |
2004年 | 35篇 |
2003年 | 40篇 |
2002年 | 29篇 |
2001年 | 32篇 |
2000年 | 21篇 |
1999年 | 24篇 |
1998年 | 28篇 |
1997年 | 29篇 |
1996年 | 36篇 |
1995年 | 22篇 |
1994年 | 19篇 |
1993年 | 30篇 |
1992年 | 12篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1974年 | 4篇 |
1972年 | 2篇 |
排序方式: 共有1188条查询结果,搜索用时 15 毫秒
91.
Takao Morimura Masayuki Hasaka Kunikazu Shimoda Hiromichi Nakashima 《Journal of Electronic Materials》2010,39(9):2149-2153
The thermoelectric half-Heusler compounds Ti
x
NiSn0.998Sb0.002 (x = 1.0 to 1.2) and Ti
y
Zr0.25Hf0.25NiSn0.998Sb0.002 (y = 0.5 to 0.65) with nonstoichiometric nominal compositions were prepared by spin-casting and subsequent annealing at 1073 K
for 24 h. The dimensionless figure of merit ZT at room temperature was maximized at x = 1.1 and y = 0.6 in Ti-rich compounds through an increase in absolute Seebeck coefficients despite a decrease in electrical conductivities.
ZT reached 0.07 at x = 1.1 and 0.14 at y = 0.6. In powder x-ray diffraction analysis, minor phases of β-Sn, TiNi, Ti2Sn, and Ti5Sn3 were observed in addition to a major phase of half-Heusler. The quantity of the minor phases was minimized at x = 1.1 and y = 0.55, where the absolute Seebeck coefficients are maximized. In transmission electron microscopic (TEM) analysis of Ti0.55Zr0.25Hf0.25NiSn0.998Sb0.002, crystal grains of the half-Heusler phase, from several hundred nanometers to several micrometers in size, were observed.
TEM energy-dispersive spectroscopy measurements indicated that fluctuations of Ti, Zr, and Hf compositions within the Ti-site
in the half-Heusler phase may occur. Thermoelectric properties were improved at x = 1.1 and y = 0.6 rather than at the stoichiometric compositions of x = 1.0 and y = 0.5 due to minimization of the precipitate quantities. 相似文献
92.
93.
We investigated author information in scientific articles by approximately 7,000 researchers for a quantitative analysis of
researchers’ international mobility. From top journals, we traced the movements of more than 2,200 researchers in the research
domains of robotics, computer vision and electron devices. We categorized countries’ characteristics for the balance between
the inflow and the outflow of researchers moving internationally. Flow patterns of international mobility confirm that the
United States, China and India exhibit the greatest global flows of researchers, with Singapore and Hong Kong attracting remarkable
numbers of researchers from other countries. International mobility focusing on institutions reveals that universities in
Singapore receive as many foreign researchers as do research universities in the United States. Furthermore, firms and international
collaborative research institutes act as alternative receivers to the universities in the electron devices research domain. 相似文献
94.
95.
Dense samples of the higher boride YB22C2N have been fabricated through the spark plasma sintering (SPS) method with different sintering aids. YB22C2N is a representative of a series of newly discovered rare-earth borocarbonitrides, which may be the long-awaited n-type counterpart of boron carbide, “B4C.” The effect of Si, SiC, Al, and TiC additions on the sintering process of YB22C2N has been studied. The best sintered bodies with densities higher than 90% of theoretical density were obtained by means
of SPS at 1700°C. We show that the additive choice and pressure have an effect on grain size and density. An investigation
of the effect of atmosphere on the sintering behavior has also been carried out. It was found that sinterability is enhanced
under nitrogen atmosphere. Thermoelectric properties of the materials sintered with additives have been evaluated, and we
discuss their dependences on the fabrication process route. 相似文献
96.
The influence of the Bi content on the fillet-lifting phenomenon in Sn-3Ag-Bi alloys was investigated. The peculiar composition
dependence on the fillet-lifting exists in Sn-3Ag-xBi alloys. With fillet-lifting, they are 3–20%Bi. Without fillet-lifting,
they are 0–1%Bi, 30%Bi, and above. This is related to the alloy solidification characteristics, in particular, the amount
of latent heat release near the final solidification temperature (solidus temperature) during solidification. Fillet-lifting
is likely to occur in the alloy with a latent heat released which is insufficient for alleviation of the temperature gradient
in the solder joint. A new predictable index for the occurrence of fillet-lifting is proposed as the fillet-lifting resistant
index (FRI) that correlates well with the fillet-lifting occurrence rate. The fillet-lifting does not occur when a solder
alloy has a FRI of 0.75 and above. The magnitude of the solidification temperature range (T) does not necessarily correlate
with the fillet-lifting, because there are some alloys without fillet-lifting in spite of their having a wide T. There is
also little correlation between the fillet-lifting and the formation of a Bi concentration at the solder/Cu land interface,
previously thought to cause fillet-lifting. The Bi concentration at the solder/Cu land interface may occur as a consequence
of the Sn consumption by the intermetallic compound formation with the Cu dissolving into the molten solder and existing at
the interface rather than the solidification segregation. 相似文献
97.
Takao Yasui Noritada Kaji Yukihiro Okamoto Manabu Tokeshi Yasuhiro Horiike Yoshinobu Baba 《Microfluidics and nanofluidics》2013,14(6):961-967
Recent developments of nanofabrication techniques have created a trend switching from randomly ordered polymeric matrices, such as gel, to highly ordered sieving nanostructures in the separation of biomolecules. These nanostructures have enormous potential for fast separation of biomolecules, while nanostructure-based separation techniques suffer from critical scaling problems; they are efficient in handling less than nanoliter amounts of sample fluids, but most biomolecule samples are available in a liquid volume that is over several microliter, leading to a reduction in sensitivity and resolution. In this study, we developed a nanopillar array chip integrated with an easy and rapid on-line stacking method and achieved fast DNA separation with high sensitivity and high resolution. The developed on-line stacking method is based on the balance of two forces driven by electric fields: electroosmotic flow (EOF) and electrophoresis. The EOF mobility from the microchannel to the nanopillar-channel is drastically decreased, while, on the other hand, electrophoresis has constant mobilities in the whole length of the channels. The on-line stacking was realized at the well-balanced position of the two forces, and the on-line stacking using the nanopillar array chip can also be achieved within 10 s by just applying electric voltages without any other special reagents and materials. After applying on-line stacking using the nanopillar array chip, the relative fluorescence intensity increased 1,000-fold, and the resolution was twice as good as that without on-line stacking. 相似文献
98.
Quantitative analysis of collaborative and mobility networks 总被引:1,自引:0,他引:1
This study proposes a quantitative analysis of researcher mobility (i.e. transfer from one institution to another) and collaborative
networks on the basis of author background data extracted from biographical notes in scientific articles to identify connections
that are not revealed via simple co-authorship analysis. Using a top-ranked journal in the field of computer vision, we create
a layered network that describes various aspects of author backgrounds, demonstrating a geographical distribution of institutions.
We classify networks according to various dimensions including authors, institutions and countries. The results of the quantitative
analysis indicate that mobility networks extend beyond the typical collaborative networks describing institutional and international
relationships. We also discuss sectoral collaboration considering the mobility networks. Our findings indicate a limitation
of collaborative analysis based on bibliometric data and the importance of tracing researcher mobility within potential networks
to identify the true nature of scientific collaboration. 相似文献
99.
Takao Kume Yoichi Ikeda Takaya Iseki Hisataka Yakabe Hiroyuki Tanaka Hideaki Hikosaka Yasuhiro Takagi Masaya Ito 《International Journal of Hydrogen Energy》2013
We have been developing a hydrogen production module with a Pd-based membrane on catalyst (MOC) from natural gas. The MOC module is expected to be more compact and cheaper than the conventional hydrogen production module. To evaluate the hydrogen production performance of the MOC module and to clear the factor that dominates the effective hydrogen production, we compared the reforming performance of the catalytic support without hydrogen permeable membrane and the MOC module at various reaction conditions. As a result, it was cleared that hydrogen permeation through the membrane improves the methane conversion drastically in the MOC module by comparing with the support only module and changing the experimental conditions. 相似文献
100.
Hydrogels that contain phosphate groups in side chains were studied for their usefulness in drug‐delivery soft contact lenses (SCLs). Naphazoline, a model drug having a cationic group, was incorporated into an SCL because of its phosphate groups and was released over a period of about 14 h. For the SCL, the naphazoline content was equivalent to the phosphate group content. It is suggested that drug‐delivery SCLs can be designed to contain the needed amount of a drug through the choice of the ionic group for the ligand. Furthermore, the SCL having amide groups and phosphate groups had high transparency and an unchanged shape. It is suggested that amide groups and phosphate groups must be introduced into the polymer in equimolar amounts to give the necessary polymer–drug interaction. Therefore, hydrogels having a drug‐delivery system were synthesized by the inclusion of a phosphate group and an amide group. These hydrogels are also applicable to SCL materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 731–735, 2005 相似文献