全文获取类型
收费全文 | 3756篇 |
免费 | 83篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 283篇 |
综合类 | 4篇 |
化学工业 | 884篇 |
金属工艺 | 110篇 |
机械仪表 | 76篇 |
建筑科学 | 56篇 |
能源动力 | 159篇 |
轻工业 | 254篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 322篇 |
一般工业技术 | 590篇 |
冶金工业 | 784篇 |
原子能技术 | 92篇 |
自动化技术 | 226篇 |
出版年
2023年 | 18篇 |
2022年 | 39篇 |
2021年 | 59篇 |
2020年 | 30篇 |
2019年 | 20篇 |
2018年 | 42篇 |
2017年 | 42篇 |
2016年 | 88篇 |
2015年 | 38篇 |
2014年 | 79篇 |
2013年 | 179篇 |
2012年 | 134篇 |
2011年 | 157篇 |
2010年 | 130篇 |
2009年 | 154篇 |
2008年 | 152篇 |
2007年 | 135篇 |
2006年 | 134篇 |
2005年 | 118篇 |
2004年 | 95篇 |
2003年 | 95篇 |
2002年 | 101篇 |
2001年 | 66篇 |
2000年 | 60篇 |
1999年 | 88篇 |
1998年 | 323篇 |
1997年 | 224篇 |
1996年 | 150篇 |
1995年 | 85篇 |
1994年 | 86篇 |
1993年 | 94篇 |
1992年 | 51篇 |
1991年 | 50篇 |
1990年 | 46篇 |
1989年 | 45篇 |
1988年 | 28篇 |
1987年 | 37篇 |
1986年 | 27篇 |
1985年 | 35篇 |
1984年 | 30篇 |
1983年 | 34篇 |
1982年 | 30篇 |
1981年 | 28篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 42篇 |
1974年 | 8篇 |
1969年 | 9篇 |
排序方式: 共有3844条查询结果,搜索用时 9 毫秒
31.
Miyahara Daiki Ueda Itaru Hayashi Yu-ichi Mizuki Takaaki Sone Hideaki 《International Journal of Information Security》2021,20(5):729-740
International Journal of Information Security - Card-based cryptography is an attractive and unconventional computation model; it provides secure computing methods using a deck of physical cards.... 相似文献
32.
Kazunori Nagasaka Takeshi Yoshida Yoshihiro Kita Fumio Hashimoto 《International Journal of Machine Tools and Manufacture》1987,27(2)
For optimization of abrasive cut-off operation, wheel wear equation must be identified before the operation is optimized. The equation is obtained by using GMDH algorithm with successive determination of trends containing interactive terms. In the model equation factors of grinding fluid are taken into consideration in addition to the factors of wheel, work material, feed (table speed) and wheel speed. For the identification of the model wheel wear tests are performed under the experimental design treating the above-mentioned factors as independent variables. The grinding ratio (output in the model) can be predicted for combinations of various factors using the model. With the wheel wear equation and machining cost model, the optimum combination of wheel, fluid, feed and wheel speed can be selected for a given work material. The relationships between these variables and the costs are investigated. 相似文献
33.
This paper deals with the frame topology optimization under the frequency constraint and proposes an algorithm that solves a sequence of relaxation problems to obtain a local optimal solution with high quality. It is known that an optimal solution of this problem often has multiple eigenvalues and the feasible set is disconnected. Due to these two difficulties, conventional nonlinear programming approaches often converge to a local optimal solution that is unacceptable from a practical point of view. In this paper, we formulate the frequency constraint as a positive semidefinite constraint of a certain symmetric matrix, and then relax this constraint to make the feasible set connected. The proposed algorithm solves a sequence of the relaxation problems with gradually decreasing the relaxation parameter. The positive semidefinite constraint is treated with the logarithmic barrier function and, hence, the algorithm finds no difficulty in multiple eigenvalues of a solution. Numerical experiments show that global optimal solutions, or at least local optimal solutions with high qualities, can be obtained with the proposed algorithm. 相似文献
34.
Hiroki Kikuchi Shigeki Hashimoto Shinichiro Tajiri Tsuneo Hayashi Yutaka Sugawara Michio Oka Yoshiyuki Akiyama Akira Nakamura Naoya Eguchi 《Journal of the Society for Information Display》2009,17(3):263-269
Abstract— A high‐pixel‐rate, high‐contrast (30,000:1) wide‐color‐gamut grating‐light‐valve laser projector is reported. A new optical engine enabling high‐frame‐rate (240 Hz) scan projection is employed. Panoramic wide‐angle‐scan projection with a 64:9 aspect ratio was also developed. Speckle noise is eliminated using a simple but highly efficient technique. The optical throughput efficiency of the grating‐light‐valve laser projector is reviewed. 相似文献
35.
S Matsuo Y Takeuchi S Hayashi A Kinugasa T Sawada 《Canadian Metallurgical Quarterly》1994,10(3):237-240
A patient with unusual Hutchinson-Gilford syndrome (progeria) is reported. This 7-year-old boy had all the characteristics of progeria, except for coxa valga and the "horse-riding" stance. A previous cerebral infarction was detected in the right putamen on cranial magnetic resonance imaging. During treadmill exercise test electrocardiography, ST depression suggested the existence of arteriosclerotic lesions. Skin fibroblast culture exhibited 76% DNA-repair capacity compared to normal. He has not manifested endocrinologic abnormalities. From these findings it is concluded that this patient has an incomplete case of Hutchinson-Gilford syndrome and that a correlation may exist between the clinical features and the degree of DNA-repair capacity. 相似文献
36.
Taiju Takahashi Yukihiro Kudoh Yuichi Saito Yoshihiro Aoyagi 《Journal of the Society for Information Display》2023,31(3):101-111
Recently, there has been considerable research on optical devices, such as liquid crystal (LC) lenses and special optical plates, using LCs. In such devices, relatively small LC cells are frequently used, or unique LC orientations are required. As an LC orientation process, we focused on the LC director's orientation induced by the magnetic force line distribution of a small neodymium magnet. We propose a simple method for obtaining radial orientation, which is rather difficult to obtain using the ordinary rubbing method. The initial orientation in the LC cell is a vertical orientation cell with almost zero azimuth anchoring. With the proposed method, the reorientation process is performed with an assisting electric field and a small permanent magnet, unlike the conventional magnetic field orientation process that requires a large electromagnet. Furthermore, a polymer stabilization treatment is used to fix the obtained radial orientation pattern in the LC cell. After the treatment, the applying voltage can control the tilt angle of the director in weak polymer treatment, and a completely fixed orientation pattern can be obtained that in strong. 相似文献
37.
Kim HB Hayashi M Nakatani K Kitamura N Sasaki K Hotta J Masuhara H 《Analytical chemistry》1996,68(3):409-414
Ion-exchange processes of a cationic dye (Rhodamine B; RhB) were studied for individual polymer particles (diameter of 16-20 μm) by laser trapping microspectroscopy and confocal fluorescence laser microspectroscopy. The absorbance of RhB at 565 nm adsorbed on a cation-exchange particle increased linearly with the concentration of RhB in the aqueous phase, while it was independent of the particle diameter. Fluorescence intensity profile measurements of RhB along the particle diameter by confocal fluorescence microspectroscopy directly proved that ion exchange took place in the surface layer (~2-μm thickness) of the particle in the initial stage (1 h). Diffusion of RhB in the particle was very slow, and ion exchange proceeded gradually to the inner volume in the order of days. The ion-exchange processes were analyzed on the basis of simulation of the time course of the concentration profile of RhB in the particle, and the diffusion coefficient of RhB was determined to be (2-4) × 10(-11) cm(2)·s(-1). 相似文献
38.
H Toyoshima S Hayashi N Tanabe K Miyanishi T Satoh Y Aizawa T Izumi 《Canadian Metallurgical Quarterly》1996,59(3-4):81-95
Epidemiological features, risk factors and preventive methods of sudden death (SD) derived from studies the authors have performed since 1987 together with colleagues in Niigata University School of Medicine were reviewed. When SD was defined as death occurring within 24 hours of the onset of symptoms, the annual incidence was 145/100,000 for people aged 15 years and older in Niigata Prefecture. The incidence increased sharply along with the advance of age, while the proportion of SD to natural death due to circulatory diseases was higher in younger people. Though diseases of the circulatory system made up approximately 90 percent of all causes of death, SD due to ischemic heart disease was less frequent in Japan than in western countries. SD showed various patterns in seasonal and "within-a-day" occurrences according to sex, age and cause of death. The months of the highest SD occurrence differed by occupation and matched the busiest work periods. A decrease in sleeping hours and mental stress experienced during the preceding week were related to the occurrence of both sudden death and non-fatal acute myocardial infarction. People having structural circulatory diseases were shown to be predisposed to SD when stress occurred, because fatal arrhythmia is easily induced by the above factors in such people. Health examinations were shown to have preventive effects, though limited, against SD. Differences in the resuscitated rates in cases where a witness was present and where one was not indicates that educating people about correct resuscitation methods is important to minimizing SD. 相似文献
39.
40.
The purpose of this study was to design an endoscopic dissector handle and objectively assess its usability. The handles were designed with increased contact area between the fingers and thumb and the eye rings, and the eye rings were modified to have a more perpendicular insertion angle to the finger midline. Four different handle models were compared, including a conventional product. Subjects performed dissection, exclusion, grasping, precision manipulation and precision handling tasks. Electromyography and subjective evaluations were measured. Compared to conventional handles, the designated handle reduced the muscle load in the extensor and flexor muscles of the forearm and increased subjective stability. The activity of the first dorsal interosseous muscle was sometimes influenced by the shape of the other parts. The ergonomically designed endoscopic dissector handle used in this study achieved high usability. Medical instrument designs based on ergonomic concepts should be assessed with objective indices.
Practitioner Summary: The endoscopic dissector handles were designed with increased contact area and more suitable insertion angle between the fingers and thumb and the eye rings. Compared to conventional handles, the designated handle reduced the muscle load in the extensor and flexor muscles of the forearm and increased subjective stability. 相似文献