全文获取类型
收费全文 | 633篇 |
免费 | 25篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 117篇 |
金属工艺 | 14篇 |
机械仪表 | 45篇 |
建筑科学 | 33篇 |
能源动力 | 23篇 |
轻工业 | 57篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 84篇 |
一般工业技术 | 127篇 |
冶金工业 | 67篇 |
原子能技术 | 2篇 |
自动化技术 | 74篇 |
出版年
2023年 | 9篇 |
2022年 | 12篇 |
2021年 | 18篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 11篇 |
2017年 | 21篇 |
2016年 | 24篇 |
2015年 | 19篇 |
2014年 | 32篇 |
2013年 | 42篇 |
2012年 | 41篇 |
2011年 | 51篇 |
2010年 | 37篇 |
2009年 | 34篇 |
2008年 | 39篇 |
2007年 | 22篇 |
2006年 | 27篇 |
2005年 | 18篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 4篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 21篇 |
1997年 | 7篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有658条查询结果,搜索用时 15 毫秒
71.
This bibliography is compiled to assist in locating papers related to the application of scanning electron microscopy (SEM) to cerebrospinal-fluid-contacting surfaces in vertebrates. The use of SEM by neuroscientists has continued apace since the publication of the first bibliography in 1980. SEM studies now include more than 50 species of vertebrates and range from cyclostomes to humans; they encompass development from embryo to senescence and concern both normal and pathologic morphology. Although remarkable strides have been made toward a greater understanding of many aspects of the structure and function of cerebrospinal-fluid-contacting surfaces, many significant problems await the judicious application of scanning electron microscopy. 相似文献
72.
The melt polymerization of nylon 4, I was studied, starting with nylon-salt and nylon prepolymers (ηinh=0.25). With nylon-salt only low molecular polymers were obtained, while with prepolymers the inherent viscosity could be raised to 0.77 (3h, 270°, vac.). The cyclization of tetra methylene diamine to pyrrolidine seem to be the major disturbing factor. The polymer is glassy and could easily be melt pressed. The torsion modulus of the material at 20°C was high (1.8 109 Pa) and remained high to near its Tg (138°C). 相似文献
73.
The aim of this study was to assess the reproducibility of a number of simplified clearance methods using chromium-51 ethylenediamine tetraacetic acid (51Cr-EDTA) and to compare these with the multiple blood sample technique. Twenty-four healthy volunteers were enrolled into the study. The test was performed twice, 1 week apart and under similar physiological conditions. After intravenous injection of the tracer, 13 blood samples were taken between 5 and 240 min. The reference clearance was calculated after adapting a bi-exponential fit on the whole plasma disappearance curve. Simplified methods included the slope intercept method using different combinations of blood samples (2 and 4 h; 2, 3 and 4 h; 1.5, 2, 3 and 4 h; 1.5, 2 and 3 h) and several single clearance methods (Constable 3 h; Groth 3 h; Groth 4 h). The standard deviation of the differences between the first and second measurements were similar for all methods, confirming the comparable reproducibility of these methods. 相似文献
74.
三端双向晶闸管用于控制AC电源负载。在大多数应用中,三端双向晶闸管会消耗大量电能,因而需要考虑散热。同时必须计算散热器的大小并预测最高结点温度Tjmax。散热设计和分析是设计和开发过程的基本部分。散热设计需要几个计算阶段,涉及到功率、热阻和温度升高。本文介绍的便是这些计算。 相似文献
75.
H Kim EK Ham YI Kim JG Chi HS Lee SH Park YM Jung NK Myung MJ Lee JJ Jang 《Canadian Metallurgical Quarterly》1998,131(2):177-183
We have shown previously that normal B cells share, with Epstein-Barr virus-transformed and malignant B cells, the ability to activate the alternative pathway (AP) of complement in vitro, resulting in the deposition of C3 fragments on the cell surface. Complement receptor type 2 (CR2, CD21) has been implicated directly as the site for formation of an AP convertase, which provides nascent C3b for deposition at secondary sites on the B-cell surface. In the present study, we have examined C3 fragment deposition in vitro in more detail by (1) assessing the importance of locally generated C3b for the deposition process, (2) investigating whether CR2 is the sole requirement for conferring AP activation capacity on a cell, and (3) determining whether CR2's function, as an AP activator, has different structural requirements from ligand binding. Increasing the availability of native C3, by increasing the serum (NHS) concentration, resulted in enhanced C3 fragment deposition on the B cells, whereas use of factor 1-depleted NHS, which showed massive fluid phase C3 conversion during the incubation, diminished the deposition. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting of untreated and hydroxylamine-treated lysates from B cells, after in vitro activation, revealed that the majority of C3 fragments (primarily iC3b and C3dg) had been covalently bound to the cell surface. Transfection of COS cells with wild-type CR2 or a deletion mutant lacking 11 of the molecule's 15 homologous domains, but retaining the ligand-binding site, revealed that expression of intact CR2 conferred a 12-fold increase in AP-activating capacity on these cells, while no increase in AP activity was apparent on cells transfected with the mutant CR2. 相似文献
76.
Cord blood was obtained from 164 neonates at birth and investigated for the presence of aflatoxins. 14 of the samples were neonates without jaundice and 150 from neonates with jaundice. There was significant reduction (P > 0.05) in birth weight of jaundiced neonates with aflatoxin. Neonates with jaundice have high mean concentration of aflatoxin B1 (32.3 ng/ml and 35.6 ng/ml). Aflatoxin G1 was not detected in any of the groups. The rate of detection was higher in wet (81.8%) than dry season (50.0%). These findings show that neonates are exposed to aflatoxin prenatally and that high incidence of jaundice occurred in the wet warm months. 相似文献
77.
The theory that adolescence is universally a time of emotional turmoil has been disproved, yet research indicates higher rates of negative affect among adolescents than preadolescents. This study evaluates the relationship of distressed affect in early adolescence to the experience of stressful life events. 483 5th–9th graders provided experience sampling reports on their daily emotional states; data on recent major events in the child's life were obtained from the child and a parent. Findings indicate that older students in this age range encountered more negative events than younger ones, including more peer, school, and family events, and that experience of multiple negative events had a stronger association with daily negative affect among the older students. These findings suggest that the higher rates of daily distress experienced in adolescence may be partly attributable to the greater number of negative life events encountered by some youths. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
Bj?rn?VerrelstEmail author Ronald?Van?Ham Bram?Vanderborght Frank?Daerden Dirk?Lefeber Jimmy?Vermeulen 《Autonomous Robots》2005,18(2):201-213
This paper reports on the bipedal robot Lucy which is actuated by pleated pneumatic artificial muscles. This novel actuator is very suitable to be used in machines which move by means of legs. Besides its high power to weight ratio the actuator has an adaptable passive behavior, meaning the stiffness of the actuator can be changed on-line. This allows to change the natural frequency of the system while controlling angular joint positions. The main control concept intended for Lucy is joint trajectory control while selecting appropriate actuator compliance characteristics in order to reduce control efforts and energy consumption which is of great importance towards the autonomy of legged robots. Presently Lucy has made her first steps with the implementation of basic control strategies.The pleated pneumatic artificial muscle and its characteristics will be discussed briefly and the design of Lucy which is made modular on mechanical as well as electronic hardware level will be described in detail. To pressurize the muscles, a lightweight valve system has been developed which will be presented together with the fundamental control aspects of a joint actuated with two antagonistically setup artificial muscles. Additionally the first experimental results will be shown and briefly discussed.Björn Verrelst (1972) Study of Mechanical Engineering at the Vrije Universiteit Brussel, graduated in 1996. Since 1998 researcher and teaching assistant at the Vrije Universiteit Brussel. The focus of his research is the use of pneumatic artificial muscles in the walking biped Lucy for dynamically balanced walking.Ronald Van Ham (1976) Study of Electro-Mechanical Engineering at the Vrije Universiteit Brussel, graduated in 1999. Since 1999 researcher and teaching assistant at the Vrije Universiteit Brussel. The focus of his research is the use of adaptable compliance of pneumatic artificial muscles in the walking biped Lucy.Bram Vanderborght (1980) Study of Mechanical Engineeringat the Vrije Universiteit Brussel, graduated in 2003. Since 2003 researcher at the Vrije Universiteit Brussel, supported by the Fund for Scientific Research Flanders (Belgium). The focus of his research is the use of adaptable compliance of pneumatic artificial muscles in the dynamically balanced biped Lucy.Frank Daerden (1966) Study of Mechanical Engineering at the Vrije Universiteit Brussel. Ph.D. in Applied Sciences, Vrije Universiteit Brussel, 1999. Research and teaching assistant at the Vrije Universiteit Brussel, 1991–1999. Doctor-Assistant at the dept. of Mechanical Engineering, Vrije Universiteit Brussel since 1999, visiting Professor since 2003.Dirk Lefeber (1956) Study of Civil Engineering at the Vrije Universiteit Brussel. Ph.D. in Applied Sciences, Vrije Universiteit Brussel, 1986. Professor at the dept. of Mechanical Engineering, head of the Multibody Mechanics Research Group, Vrije Universiteit Brussel.Jimmy Vermeulen (1973) Study of Mechanical Engineering at the Vrije Universiteit Brussel. Ph.D. in Applied Sciences, Vrije Universiteit Brussel, 2004. Research and teaching assistant at the Vrije Universiteit Brussel, 1996–2004. Post-Doctoral researcher at the dept. of Mechanical Engineering, Vrije Universiteit Brussel since 2004. The focus of his research is trajectory generation and control of dynamically balanced legged robots. 相似文献
79.
Pellets pressed from sponge palladium powder were sintered both isothermally and with constant heating rates using a precision
low force dilatometer. Computer analysis of the data is used to determine shrinkage and shrinkage rate behavior during the
sintering operation. The data are used in conjunction with metallographic examination to correlate the shrinkage phenomena
to the change in grain size and pore morphology. The results show a characteristic shrinkage rate behavior associated with
grain growth during sintering which can effectively halt densification. 相似文献
80.
Mun-Seok Choi Sung-Hoon Kim Young-Hyeok Kim Ill Won Kim Soon-Jong Jeong Jae-Sung Song Jae-Shin Lee 《Journal of Electroceramics》2008,20(3-4):225-229
Ag–ceramic composite materials were investigated as low-cost internal electrodes for low firing piezoelectric multilayer ceramic
actuators (MLCA). Ag–ceramic pastes were prepared by adding Pb(Mg1/3Nb2/3)O3–Pb(Zr0.475,Ti0.525)O3 (PMNZT) ceramic powders to a commercial Ag paste in the range of 0 to 50 wt.%. PMNZT/Ag–PMNZT multilayered laminates were
fabricated using tape casting and subsequently cofired at 925°C for 10 h. The addition of PMNZT into Ag electrode decreased
the thermal shrinkage mismatch between the composite layers, which led to improve mass producibility of MLCA through reducing
delamination probability during cofiring process. 相似文献