全文获取类型
收费全文 | 6285篇 |
免费 | 148篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 474篇 |
综合类 | 18篇 |
化学工业 | 1718篇 |
金属工艺 | 154篇 |
机械仪表 | 165篇 |
建筑科学 | 204篇 |
矿业工程 | 8篇 |
能源动力 | 264篇 |
轻工业 | 568篇 |
水利工程 | 22篇 |
石油天然气 | 10篇 |
无线电 | 354篇 |
一般工业技术 | 1080篇 |
冶金工业 | 533篇 |
原子能技术 | 232篇 |
自动化技术 | 655篇 |
出版年
2023年 | 32篇 |
2022年 | 54篇 |
2021年 | 100篇 |
2020年 | 57篇 |
2019年 | 67篇 |
2018年 | 83篇 |
2017年 | 73篇 |
2016年 | 124篇 |
2015年 | 88篇 |
2014年 | 163篇 |
2013年 | 369篇 |
2012年 | 201篇 |
2011年 | 342篇 |
2010年 | 288篇 |
2009年 | 329篇 |
2008年 | 343篇 |
2007年 | 294篇 |
2006年 | 228篇 |
2005年 | 245篇 |
2004年 | 199篇 |
2003年 | 191篇 |
2002年 | 189篇 |
2001年 | 129篇 |
2000年 | 118篇 |
1999年 | 136篇 |
1998年 | 238篇 |
1997年 | 169篇 |
1996年 | 126篇 |
1995年 | 84篇 |
1994年 | 115篇 |
1993年 | 102篇 |
1992年 | 72篇 |
1991年 | 87篇 |
1990年 | 63篇 |
1989年 | 87篇 |
1988年 | 72篇 |
1987年 | 56篇 |
1986年 | 82篇 |
1985年 | 70篇 |
1984年 | 64篇 |
1983年 | 65篇 |
1982年 | 77篇 |
1981年 | 59篇 |
1980年 | 49篇 |
1979年 | 50篇 |
1978年 | 47篇 |
1977年 | 36篇 |
1976年 | 50篇 |
1975年 | 23篇 |
1973年 | 19篇 |
排序方式: 共有6459条查询结果,搜索用时 15 毫秒
31.
A molecular orbital approach to materials design has recently made great progress. This approach is based on the electronic structure calculations by the DV-Xα cluster method. In this paper recent progress in this approachis reviewed. In particular 相似文献
32.
Highly transparent cellulose hydrogels with physical crosslinkage were prepared from nonaqueous organic cellulose solutions and viscose by coagulating and regenerating cellulose in an aqueous solution containing a water‐miscible organic solvent. Nonaqueous organic cellulose solutions used were LiCl/dimethylacetamide, paraformaldehyde/dimethyl sulfoxide, and triethylammonium chloride/dimethyl sulfoxide. Preparation conditions and physical properties of the transparent cellulose hydrogels were studied. The transparency of the cellulose hydrogels depended on the composition of the aqueous solution containing the organic solvent. Furthermore, transparent cellulose hydrogels from viscose showed high tensile strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3020–3025, 2003 相似文献
33.
Yamaoka M. Maeda N. Shinozaki Y. Shimazaki Y. Nii K. Shimada S. Yanagisawa K. Kawahara T. 《Solid-State Circuits, IEEE Journal of》2006,41(3):705-711
The power consumption of a low-power system-on-a-chip (SoC) has a large impact on the battery life of mobile appliances. General SoCs have large on-chip SRAMs, which consume a large proportion of the whole LSI power. To achieve a low-power SoC, we have developed embedded SRAM modules, which use some low-power SRAM techniques. One technique involves expanding the write margin; another is a power-line-floating write technique, which enables low-voltage write operation. The power-line-floating write technique makes it possible to lower the minimum operating supply voltage by 100 mV. The other techniques involve using a process-variation-adaptive write replica circuit and reducing leakage current. These techniques reduce active power during write operations by 18% and reduce active leakage of the word-line driver by 64%. The prototype SRAM modules achieve 0.8-V operation, and a 512-kb SRAM module achieves 48.4-/spl mu/A active leakage and 7.8-/spl mu/A standby leakage with worst-leakage devices. 相似文献
34.
Kyoko Kawagishi Hiroshi Harada Akihiro Sato Atsushi Sato Toshiharu Kobayashi 《JOM Journal of the Minerals, Metals and Materials Society》2006,58(1):43-46
The fourth-generation nickel-based single-crystal superalloys, which contain large amounts of refractory metals for strengthening
and platinum group metals for topologically close-packed phase prevention, show excellent high-temperature strength. However,
these alloying elements seem to decrease high-temperature oxidation resistance. In this study, nickel-based superalloys with
various amounts of tantalum, rhenium, and ruthenium were examined in isothermal and cyclic exposures at 1,100°C to investigate
the effect on the oxide growth rate and resistance to scale spallation. Ruthenium and rhenium were found to degrade the oxidation
resistance by the vaporization of their oxide. Tantalum-rich oxide in the spinel layer acts to stabilize ruthenium and rhenium
oxide in the scale. The addition of hafnium and yttrium is effective in improving the oxidation resistance of ruthenium-containing
nickel-based superalloys. 相似文献
35.
36.
The wide scattering in tool life of natural mono-crystalline diamond tools is considered to depend on intrinsic crystalline defects due to nitrogen impurities in raw diamond. In this paper, the correlation was investigated between the amounts and types of the impurity evaluated by infrared absorption (IRA) and the crater wear and chipping resistances. As a result, diamonds including less total amount of impurity show larger wear resistance and that with larger amount of B2-aggregates show larger chipping resistance. This suggests that the inspection by IRA can be a useful method for screening of raw diamond for highly durable cutting tools. 相似文献
37.
Yoshio Yamashita Hideyuki Jinbo Ryuji Kawazu Takateru Asano Hiroshi Umehara 《Polymer Engineering and Science》1991,31(12):855-859
LMR-UV (“low molecular weight resist for uv lithography”), a naphthoquinone-diazide sulfonic acid ester of a novolak resin, is a negative working resist. The mechanism of insolubilization of LMR-UV is based on the facts that the naphthoquinone-diazide moiety is decomposed to indenecarboxylic acid (polar compound) by photolysis upon UV irradiation and that the irradiated resist film insolubilizes in a non-polar developer. LMR-UV reliably forms 0.6 μm lines and spaces over a reflective substrate with steps by using a g-line stepper having a 0.35 NA lens. 0.6 μm-wide aluminum patterns over topography are obtained by use of g-line exposure and reactive ion etching. By use of an i-line aligner (NA = 0.42), LMR-UV resolves 0.25 μm space patterns with overhang profiles. The profiles are due to the large absorption coefficient of 3.8 μm?1. 0.3 μm wide aluminum patterns are formed by i-line exposure and lift-off metallization. 相似文献
38.
39.
Shinichi Nomura Takushi Hagita Hiroaki Tsutsui Yoshihisa Sato Ryuichi Shimada 《Electrical Engineering in Japan》2008,164(2):37-43
The objective of this work is to discuss the concept of back‐to‐back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back‐to‐back DC link. In this case, each converter of the back‐to‐back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two‐way switch is connected to the AC side of each converter. This two‐way switch can select the interconnected power systems. By using the two‐way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower‐cost power of each power network can be stored through two converters during the off‐peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back‐to‐back interconnection with SMES and discuses the optimal SMES configuration for a 300‐MW‐class back‐to‐back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20482 相似文献
40.
This paper investigates induced voltage characteristics from an overhead transmission line by applying a method of modeling of induced voltages proposed by the authors. EMTP simulation results obtained by the modeling method agree with analytical results obtained from a well‐known formula. The induced voltages are significantly dependent on the configuration of the overhead line. A horizontal line induces the largest voltage in a gas pipeline, and the voltage induced by a vertical twin‐circuit line is about 20% smaller than that induced by a vertical single‐circuit line. The method is applied to a real pipeline system and the simulation results show reasonable agreement with field test results. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 43–51, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20465 相似文献