全文获取类型
收费全文 | 2005篇 |
免费 | 26篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 127篇 |
综合类 | 2篇 |
化学工业 | 430篇 |
金属工艺 | 130篇 |
机械仪表 | 24篇 |
建筑科学 | 23篇 |
能源动力 | 97篇 |
轻工业 | 116篇 |
水利工程 | 8篇 |
无线电 | 221篇 |
一般工业技术 | 305篇 |
冶金工业 | 356篇 |
原子能技术 | 44篇 |
自动化技术 | 152篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 31篇 |
2020年 | 17篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 15篇 |
2016年 | 35篇 |
2015年 | 17篇 |
2014年 | 46篇 |
2013年 | 91篇 |
2012年 | 70篇 |
2011年 | 109篇 |
2010年 | 60篇 |
2009年 | 98篇 |
2008年 | 75篇 |
2007年 | 78篇 |
2006年 | 83篇 |
2005年 | 64篇 |
2004年 | 45篇 |
2003年 | 55篇 |
2002年 | 64篇 |
2001年 | 61篇 |
2000年 | 50篇 |
1999年 | 55篇 |
1998年 | 152篇 |
1997年 | 71篇 |
1996年 | 75篇 |
1995年 | 54篇 |
1994年 | 67篇 |
1993年 | 42篇 |
1992年 | 38篇 |
1991年 | 37篇 |
1990年 | 32篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 13篇 |
1975年 | 4篇 |
1972年 | 4篇 |
排序方式: 共有2035条查询结果,搜索用时 15 毫秒
21.
Solitary DFB laser diodes with 174 kHz beat linewidth are applied to a 10 Gbit/s optical BPSK homodyne detection system for the first time: a sensitivity of -38.9 dBm was achieved. A three-electrode laser forms the local oscillator and is modulated with a partial push-pull scheme to improve its frequency response 相似文献
22.
X. J. Liu R. Kainuma I. Ohnuma K. Ishida K. Oikawa 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(12):53-59
Phase diagrams and a thermodynamic database constructed by the Calculation of Phase Diagrams approach offer powerful tools
for alloy design and materials development. This article presents recent progress on the thermodynamic database for microsolders
and copper-based alloys, which is useful for the development of lead-free solders and prediction of interfacial phenomena
between solders and the copper substrate in electronic packaging technology. In addition, examples of phase diagram applications
are presented to facilitate the development of Co-Cr-based magnetic recording media in hard disks and new ferromagnetic shape-memory
alloys.
For more information, contact K. Ishida, Tohoku University, Department of Materials Science, Graduate School of Engineering,
Aoba-yama 02, Sendai 980-8579, Japan. 相似文献
23.
Mechanical alloying of polymer/metal systems 总被引:2,自引:0,他引:2
24.
Characterization of C-S-H from Highly Reactive β-Dicalcium Silicate Prepared from Hillebrandite 总被引:1,自引:1,他引:0
Yoshihiko Okada Hideki Ishida Kaori Sasaki J. Francis Young Takeshi Mitsuda 《Journal of the American Ceramic Society》1994,77(5):1313-1318
β-dicalcium silicate synthesized by thermal dissociation of hydrothermally prepared hillebrandite (Ca2 (SiO3 )(OH)2 ) exhibits extremely high hydration activity. Characterization of the hydrates obtained and investigation of the hydration mechanism was carried out with the aid of trimethylsilylation analysis, 29 Si magic angle spinning nuclear magnetic resonance, transmission electron microscopy selected area electron diffraction, and XRD. The silicate anion structure of C-S-H consisted mainly of a dimer and a single-chain polymer. Polymerization advances with increasing curing temperature and curing time. The C-S-H has an oriented fibrous structure and exhibits a 0.73-nm dreierketten in the longitudinal direction. On heating, the C-S-H dissociates to form β-C2 S. The temperature at which βC2 S begins to form decreases with increasing chain length of the C-S-H or as the Ca/Si ratio becomes higher. The high activity of β-C2 S is due to its large specific surface area and the fact that the hydration is chemical-reaction-rate-controlled until its completion. As a result, the hydration progresses in situ and C-S-H with a high Ca/Si ratio is formed. 相似文献
25.
26.
Takaaki Wajima Tomoe Shimizu Yasuyuki Ikegami 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(6):921-927
BACKGROUND: This study aimed to investigate the synthesis of zeolites from paper sludge ash (PSA) with added diatomite to remove both NH4+ and PO43? for water purification. The PSA had low Si and significant Ca contents. Four types of diatomite: white (T‐W) and brown (T‐B) from deposits of marine origin in Takanosu, and white (S‐W) and gray (S‐G) from lacustrine deposits in Shonai, were added to NaOH solution to increase the Si content and thereby synthesize zeolites with high cation exchange capacity (CEC). RESULTS: The order of the amounts of Si extracted from the diatomite to the alkali solution was S‐W > T‐W = T‐B > S‐G, which correlates with the amorphous SiO2 content of diatomite. The original ash without addition of diatomite yielded hydroxysodalite with CEC of about 1.0 mmol g?1. For all samples, the addition of diatomite to the solution yielded zeolite‐P with a higher CEC, but the addition of excess Si inhibited the synthesis of zeolite‐P, and the CEC of the product was low. A product with high CEC including zeolite‐P was obtained in a solution with around 500 mmol L?1 of Si concentration, and had the ability to remove both NH4+ and PO43?. CONCLUSION: Diatomite has the potential for used as an additive for the synthesis of high CEC zeolite from PSA. The product with zeolite‐P exhibited relatively high CEC, capacity for NH4+ uptake, and the ability to remove PO43? by precipitation, which is preferable for water purification applications. Copyright © 2008 Society of Chemical Industry 相似文献
27.
H Ishida T Ohsawa H Nakada D Hashimoto T Ohkubo A Adachi S Itoyama 《Canadian Metallurgical Quarterly》2003,33(7):545-549
We report an unusual case of carcinosarcoma of the colon. An 80-year-old woman was admitted to our hospital with lower abdominal pain. Computed tomography showed a large pelvic mass, 18cm in maximal diameter, and barium enema and colonoscopy both showed a type-2 tumor in the sigmoid colon. We performed Hartmann's procedure with resection of the ileocolic segment. Immunohistochemical stains of the resected specimen revealed that most of the tumor consisted of spindle cell sarcoma with neural and muscle differentiation, while only the superficial area of an ulcerated lesion contained adenocarcinoma positive for carcinoembryonic antigen. The patient died of a fast-growing recurrent pelvic tumor 6 months postoperatively. Our experience of this case and our review of eight other cases in the English literature indicate that wide resection provides the best chance of cure, but careful postoperative follow-up is essential. 相似文献
28.
We constructed a probabilistic simulator that allows all the events in population dynamics such as death, birth, mutation,
and suppression/stimulation to be described by probabilistic rules. The simulator also facilitates a lattice used for expressing
distribution and diversity (number of distinct strains) of quasispecies. The simulator is used to investigate the diversity
threshold in HIV and T-cell interaction.
This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January
31–February 2, 2008 相似文献
29.
Recently, progress has been made in the Generalized Multi-Protocol Label Switching (GMPLS) and Automatic Switched Optical
Networks (ASON) standardizations. These technologies realize construction of large-scaled optical networks, interconnections
among single-domain Wavelength Division Multiplexing (WDM) networks, and direct communication over multi-domain WDM networks.
Meanwhile, it is known that the topology of the Internet exhibits the power-law attribute. Since the topology of the Internet,
which is constructed by interconnecting ASs, exhibits the power-law, there is a possibility that large-scale WDM networks,
which are constructed by interconnecting WDM networks, will also exhibit the power-law attribute. One of the structural properties
of a topology that adheres to the power-law is that most nodes have just a few links, although some have a tremendous number
of them. Another property is that the average distance between nodes is smaller than in a mesh-like network. A natural question
is how such a structural property performs in WDM networks. In this paper, we first investigate the property of the power-law
attribute of physical topologies for WDM networks. We compare the performance of WDM networks with mesh-like and power-law
topologies, and show that links connected to high-degree nodes are bottlenecks in power-law topologies. To relax this, we
introduce a concept of virtual fiber, which consists of two or more fibers, and propose its configuration method to utilize
wavelength resources more effectively. We compare performances of power-law networks with and without our method by computer
simulations. The results show that our method reduces the blocking probabilities by more than one order of magnitude. 相似文献
30.