全文获取类型
收费全文 | 4889篇 |
免费 | 220篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 141篇 |
综合类 | 1篇 |
化学工业 | 1117篇 |
金属工艺 | 88篇 |
机械仪表 | 111篇 |
建筑科学 | 184篇 |
矿业工程 | 7篇 |
能源动力 | 203篇 |
轻工业 | 545篇 |
水利工程 | 21篇 |
石油天然气 | 8篇 |
无线电 | 472篇 |
一般工业技术 | 765篇 |
冶金工业 | 678篇 |
原子能技术 | 57篇 |
自动化技术 | 723篇 |
出版年
2023年 | 47篇 |
2022年 | 131篇 |
2021年 | 207篇 |
2020年 | 97篇 |
2019年 | 111篇 |
2018年 | 130篇 |
2017年 | 128篇 |
2016年 | 155篇 |
2015年 | 106篇 |
2014年 | 168篇 |
2013年 | 329篇 |
2012年 | 249篇 |
2011年 | 284篇 |
2010年 | 185篇 |
2009年 | 193篇 |
2008年 | 222篇 |
2007年 | 180篇 |
2006年 | 154篇 |
2005年 | 148篇 |
2004年 | 128篇 |
2003年 | 135篇 |
2002年 | 110篇 |
2001年 | 99篇 |
2000年 | 66篇 |
1999年 | 88篇 |
1998年 | 211篇 |
1997年 | 160篇 |
1996年 | 123篇 |
1995年 | 81篇 |
1994年 | 87篇 |
1993年 | 79篇 |
1992年 | 39篇 |
1991年 | 31篇 |
1990年 | 26篇 |
1989年 | 38篇 |
1988年 | 26篇 |
1987年 | 39篇 |
1986年 | 28篇 |
1985年 | 36篇 |
1984年 | 21篇 |
1983年 | 29篇 |
1982年 | 20篇 |
1981年 | 21篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 16篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1974年 | 14篇 |
1973年 | 13篇 |
排序方式: 共有5121条查询结果,搜索用时 31 毫秒
11.
Kawahito S. Ueda S. Ishida M. Nakamura T. Usui S. Nagaoka S. 《IEEE transactions on bio-medical engineering》1994,41(4):400-406
A CMOS integrated circuit for a noninvasive biological-signal telemetry system specified for use in medical and physiological studies of the influence of weightlessness in space is presented. The system can monitor multichannel (4 channels maximum) biological signals from multiple subjects (4 subjects maximum) in real time by using time multiplexing. A key technique so-called synchronized multiple-subject telemetry, to achieve multiple-subject telemetry has been proposed. This technique utilizes bidirectional optical transmissions with direct and scattered infrared lights between an observer and each of the subjects. An experimental CMOS IC to give a small light-weight low-power, and smart telemetry instrument for use on animals has been developed. This IC is for evaluating circuit blocks of the implantable monolithic telemetry instrument. The major circuit blocks include CMOS digital circuits for synchronization, subject selection and time multiplexing, analog circuits for pulse interval modulation, and other blocks such as a CMOS optical pulse receiver and an LED driver. A preliminary experimental multichannel telemetry from two subjects has been performed with the implemented IC chips, and the principal operation of the multiple-subject optical biotelemetry has been demonstrated 相似文献
12.
The supercharged flap is one which is expected to attain better survival, by anastomosing the distal vessels of the flap to the recipient vessels. An experimental study is reported to determine whether the vessel to be anastomosed should be an artery, a vein, or both. The authors advise anastomosing an artery and a vein, but they believe that arterial inflow is more important than venous drainage. 相似文献
13.
Two oscillating superleak transducers, one serving as generator, the other as detector, of first and second sound, situated at opposite ends of a one-dimensional resonance cavity, are considered. Included in the analysis are the dissipative effects of normal viscous slip and thermal diffusion through the porous membrane. The calculated amplitude and linewidth of the receiver response, both close to and away from the membrane resonance, show good agreement with available experimental data. 相似文献
14.
This paper presents a robustness analysis of the optimal solution of the step tracking problem in a one-degree of freedom control architecture, for the discrete-time multivariable (MIMO) case. It is shown that the resulting closed loop becomes arbitrarily fragile, i.e. the sensitivity peak becomes arbitrarily large, for certain reference directions. The cause of this problem is that the optimal controller depends on the reference direction. The paper shows that this dependence can be eliminated with an alternative formulation of the optimal problem where the cost is averaged over all reference directions. 相似文献
15.
Fellers Gloria; McInnis Charles; Cappelli Mario; Cragg Susan; Vaillancourt Raymond 《Canadian Metallurgical Quarterly》1987,19(1):108
The WAIS-R Information subtest was combined with 21 potential substitute Canadian content items and group-administered to 119 high school students ranging in age from 16 to 19 years. Seven acceptable substitute items were identified. Mean scores on the American items for the 16-17 and 18-19 age groups suggested that Canadians of these ages are not penalized by American content with respect to either Verbal or Full Scale IQ. Nevertheless, the research identified eight Information items, four easier and four more difficult than the standard WAIS-R implies. Similar results were noted in two previous studies of the WAIS-R, and indicate the extreme caution required for the clinical interpretation of intra test scatter. There is also evidence that item difficulty within the Information subtest may vary with the age of the subject. These results were considered indicative of the necessity for Canadian content Information items and the development of Canadian norms for an adapted WAIS-R Information subtest. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
Fadwa T. Eljack Ahmed F. Abdelhady Mario R. Eden Frederico B. Gabriel Xiaoyun Qin Mahmoud M. El-Halwagi 《Computers & Chemical Engineering》2005,29(11-12):2304
Decoupling the constitutive equations from the balance and constraint equations allows for reformulating a conventional forward problem into two reverse problems. The first reverse problem is the reverse of a simulation problem, where the process model is solved in terms of the constitutive (synthesis/design) variables instead of the process variables, thus providing the synthesis/design targets. The second reverse problem (reverse property prediction) solves the constitutive equations to identify unit operations, operating conditions and/or products by matching the synthesis/design targets. Visualization of the problem is achieved by employing recently developed property clustering techniques, which allows a high-dimensional problem to be visualized in two or three dimensions. The clusters by definition satisfy intra-stream and inter-stream conservation through linear “mixing” rules, which allows for the development of consistent additive rules along with their ternary representation. 相似文献
17.
Kenji Nomura Hiromichi OhtaKazushige Ueda Toshio Kamiya Masahiro HiranoHideo Hosono 《Thin solid films》2003,445(2):322-326
We have investigated the characteristics of transparent metal-insulator-semiconductor field-effect transistors (MISFETs) fabricated using InGaO3(ZnO)m (m=integer) single-crystalline thin films as n-channel layers and amorphous alumina as gate insulator films. The MISFETs exhibit good characteristics such as insensitivity to visible light illumination, off-current as low as ∼1 nA with a positive threshold voltage of ∼3 V and on/off current ratio of 105. The field-effect mobility increased from ∼1 to ∼10 cm2 (V s)−1 as the m-value increased. Room temperature Hall mobility also increased. However, unexpectedly these values were lower than the field-effect mobility. It is explained by existence of shallow localized state in the homologous compounds. 相似文献
18.
Nerea Burgos María Paulis M. Mirari Antxustegi Mario Montes 《Applied catalysis. B, Environmental》2002,38(4):251-258
Pt impregnated metallic monoliths prepared from anodised aluminium foils were tested to study their catalytic activity in complete oxidation of volatile organic compound (VOC) mixtures. The VOCs oxidised were 2-propanol, toluene, methyl ethyl ketone (MEK), acetone and their mixtures. Complete oxidation was obtained in all cases except for the case of 2-propanol, where acetone was found as an oxidation intermediate. Even if the adsorption of the VOC on the Al2O3 is governed by its polarity, the reactivity is mainly affected by the competition of the oxygen atoms chemisorbed on the Pt particles. 相似文献
19.
Preliminary experiments using two chemicals (CaO, a quicklime, and a cationic nitrogen-bearing precipitant, EC-004) to remove silica from geothermal brine were undertaken at the Mokai geothermal plant, New Zealand. The brine was mixed with the reagent (CaO or EC-004). The reaction was studied from the start of the experiment (NRT, 0 min, no retaining time) and after 15 min (15RT) at 90 °C. The concentration of silica in the brine was initially 954 mg/l, and decreased linearly with increasing reagent concentration. When CaO is added, the silica concentration at 15RT was 200 mg/l lower than at NRT and became almost zero on addition of 1.5 g/l. In contrast, when EC-004 is added, the total silica concentration nearly reaches the solubility of amorphous silica at 90 °C. In order to prevent silica scaling in Mokai brines cooled to 90 °C, the CaO and EC-004 added should be individually adjusted to 0.5 g/l and 80 mg/l, respectively. 相似文献
20.
T Doi S Takemura H Onodera M Ueda M Deguchi R Nakahara N Ichio S Nakanishi N Seto K Yanagida M Kondo 《Canadian Metallurgical Quarterly》1997,46(11):1108-1113
One of the anaphylatoxins, C5a, is known to increase the expression of the complement receptors, CR1 and CR3, on PMNs which play important roles in the phagocytosis. We measured the expression of these receptors before and after the stimulation with C5a and C5a-receptors (C5aR) on PMNs in patients with systemic lupus erythematosus (SLE). PMNs from 16 patients and 11 normal controls were tested. All the patients with SLE were administered with prednisolone orally and were in the inactive stage. The CR1 expression in SLE was significantly weak (p < 0.01) before and after stimulation with 4.55 nM (50 micrograms/ml) of C5a. There was no significant difference of CR3 expression before stimulation. However, after the stimulation with C5a, the increase of CR3 on PMNs from SLE was significantly small (p < 0.01). C5aR on PMNs showed no difference between the two groups. However, the expression of C5aR was significantly suppressed in patients treated with a high dosage of prednisolone (> = 10 mg/day) compared to those with a low dosage of prednisolone (< 10 mg/day). There was no significant difference of CR1 and CR3 expression between these groups. It is concluded that the increase of CR1 and CR3 on PMNs by C5a in small in SLE, of which impaired increase is not due to C5aR on PMNs, and that the expression of C5aR is suppressed by prednisolone. 相似文献