全文获取类型
收费全文 | 2620篇 |
免费 | 47篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 76篇 |
综合类 | 2篇 |
化学工业 | 450篇 |
金属工艺 | 66篇 |
机械仪表 | 48篇 |
建筑科学 | 37篇 |
能源动力 | 71篇 |
轻工业 | 170篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 337篇 |
一般工业技术 | 376篇 |
冶金工业 | 815篇 |
原子能技术 | 69篇 |
自动化技术 | 149篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 32篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2018年 | 31篇 |
2017年 | 15篇 |
2016年 | 25篇 |
2015年 | 24篇 |
2014年 | 32篇 |
2013年 | 102篇 |
2012年 | 56篇 |
2011年 | 81篇 |
2010年 | 78篇 |
2009年 | 57篇 |
2008年 | 95篇 |
2007年 | 67篇 |
2006年 | 71篇 |
2005年 | 75篇 |
2004年 | 81篇 |
2003年 | 61篇 |
2002年 | 62篇 |
2001年 | 55篇 |
2000年 | 54篇 |
1999年 | 67篇 |
1998年 | 291篇 |
1997年 | 211篇 |
1996年 | 136篇 |
1995年 | 84篇 |
1994年 | 82篇 |
1993年 | 81篇 |
1992年 | 44篇 |
1991年 | 36篇 |
1990年 | 41篇 |
1989年 | 28篇 |
1988年 | 26篇 |
1987年 | 32篇 |
1986年 | 19篇 |
1985年 | 32篇 |
1984年 | 37篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1981年 | 31篇 |
1980年 | 26篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 28篇 |
1975年 | 8篇 |
1972年 | 7篇 |
排序方式: 共有2675条查询结果,搜索用时 140 毫秒
71.
1. To see whether presynaptic activation paired with postsynaptic depolarization is necessary for the induction of long-term potentiation (LTP) in visual cortex or whether an activation of postsynaptic receptors in conjunction with depolarization is sufficient, we carried out perforated patch-clamp recordings with nystatin from cultured cortical neurons of rats. 2. Recorded neurons were monosynaptically activated either by electrical stimulation of an adjacent neuron or by direct activation of glutamate on "hot spots" of dendrites through iontophoresis or pressure ejection. In experiments in which cultured neurons were stained immunocytochemically with antibody against synaptophysin after electrophysiological recordings, hot spots were found to correspond to probable synaptic sites. 3. Excitatory postsynaptic currents (EPSCs) evoked by test stimulation applied to the adjacent neuron at 0.1 Hz were recorded at a holding potential of -60 or -70 mV for 5-10 min after an establishment of the whole cell recording configuration. Then, stimulation was paired with postsynaptic depolarization (0 mV for 200 ms) at 1 Hz for 30 or 60 s. LTP of EPSCs was induced in 7 of the 15 cells from which stable recordings were obtained for 18-30 min after pairing. 4. When postsynaptic depolarization was paired with direct glutamate application in the absence of presynaptic stimulation in 12 cells, only 1 showed LTP. Postsynaptic depolarization alone did not induce LTP in any of the six cells tested. Also, presynaptic stimulation alone did not induce LTP in any of the five cells tested. 5. These results suggest that the concurrent activation of presynaptic elements with postsynaptic depolarization is necessary for the induction of LTP in visual cortex. 相似文献
72.
T Kimura N Hatano M Wada K Iwata Y Kurosaki T Nakayama T Yamaura H Nakajima 《Canadian Metallurgical Quarterly》1995,18(11):1556-1559
The disposition of diadenosine 5'5"'-P1,P4-tetraphosphate (Ap4A), an endogenous dinucleotide, was investigated in rats. The degradation of Ap4A in rat plasma was very rapid and could be explained by a Michaelis-Menten equation: Km and Vmax values were 1.69 micrograms/ml and 4.32 micrograms/min/ml, respectively. Ap4A was degraded in rat plasma to ATP and AMP, but not to 2 ADP molecules, and these nucleotides were further degraded through adenosine. The degradations kinetics were examined. After intravenous bolus injection, Ap4A in plasma declined rapidly and the rate of elimination was dose-dependent: the biological half-life was about 3s at the dose of 1 mg/kg and was longer at 3 mg/kg. When Ap4A was administered by intravenous infusion (0.5 or 1.0 mg/kg/min), the plasma level rapidly reached a steady-state, which then rapidly declined after stopping the infusion. 相似文献
73.
We report the use of extreme broadband, high reflectivity >99.5%, optical parametric oscillator (OPO) cavity mirrors. A continuous-wave, doubly resonant, OPO demonstrated tuning over a range of 791-1620 nm with a single mirror set. Wavelength tuning was performed by temperature tuning the nonlinear material of lithium triborate. Narrow linewidth oscillation was confirmed throughout the tuning range, and threshold pump power increased gradually from 50 mW near the degeneracy to 800 mW at the tuning band edge in a double-pass pumping configuration. 相似文献
74.
Masaharu Komori Fumi Takeoka Jungchul Kang Yukihiko Kimura 《Artificial Life and Robotics》2011,16(2):162-164
The range of speed or torque of motors is limited to some degree. Industrial vehicles working in factories are required to
output a large force when they carry loads, and also to move with high velocity when they move to their destination. However,
it is impossible to realize both those requirements if a conventional reduction device is used. Velocity variation devices
using gears are widely used to change the velocity ratio between the input and output shafts. However, the motion transmission
from the input shaft to the output shaft is interrupted during the velocity ratio variation process. In order to solve this
problem, a velocity variation method that can transmit motion continuously is proposed, in which a motion transmitting element
is used. In this report, a motion transmitting element using the geometrical analysis method is proposed, a method of expressing
the curve using dispersed points is proposed, and a method of calculating the inclination and the distances along the curve
is developed. Based on the proposed methods, the geometrical form of the transmitting element is analyzed. 相似文献
75.
New pixel driving circuit using self‐discharging compensation method for high‐resolution OLED micro displays on a silicon backplane 下载免费PDF全文
Kei Kimura Yusuke Onoyama Taizo Tanaka Naobumi Toyomura Hideyuki Kitagawa 《Journal of the Society for Information Display》2017,25(3):167-176
A new 4T2C pixel circuit formed on a silicon substrate is proposed to realize a high‐resolution 7.8‐μm pixel pitch AMOLED microdisplay. In order to achieve high luminance uniformity, the pixel circuit compensates its Vth variation of the MOSFET for the driving transistor internally by using self‐discharging method. Also presented are 0.5‐in Quad‐VGA and 1.25‐in wide Quad‐XGA microdisplays with the proposed pixel circuit. 相似文献
76.
M Kusunoki K Kimura M Nakamura Y Isaka S Yoneda H Abe 《Canadian Metallurgical Quarterly》1981,1(4):413-417
The contribution of hematocrit (Ht) changes on cerebral blood flow (CBF) and brain oxygenation in ischemic cerebrovascular disease is still controversial. In the present study, effects of Ht variations of CBF and oxygen delivery were investigated in patients with ischemic cerebrovascular disease. CBF was measured by the Xe-133 intracarotid injection method in 27 patients, whose diagnoses included completed stroke, reversible ischemic neurological deficit, and transient ischemic attack. Ht values in the patients ranged from 31 to 53%. There was a significant inverse correlation between CBF and Ht in these Ht ranges. Oxygen delivery, i.e., the product of arterial oxygen content and CBF, increased with Ht elevation and reached the maximum level in the Ht range of 40-45% and then declined. The CBF-Ht and oxygen transport-Ht relations observed in our study were similar to those in the glass-tube model studies by other workers rather than to those in intact animal experiments. From these results, it is conceivable that in ischemic cerebrovascular disease, the vasomotor adjustment was impaired in such a manner that the relations among Ht, CBF, and oxygen delivery were different from those in healthy subjects. Further, an "optimal hematocrit" for brain oxygenation was also discussed. 相似文献
77.
T. Sasaki N. Yoneyama A. Suzuki I. Ito N. Kobayashi Y. Ikemoto H. Kimura N. Hanasaki H. Tajima 《Journal of Low Temperature Physics》2006,142(3-4):377-382
The electronic phase separation on macroscopic scale is studied in the organic Mott system κ-(BEDT-TTF)2Cu[N(CN)2]Br by means of scanning microregion infrared spectroscopy using the synchrotron radiation. The phase separation appears in
the vicinity of the Mott boundary in the single crystals of which the band width is controlled by partly substituting the
BEDT-TTF molecule with the deuterated one. The transport properties under the phase separation are considered to be influenced
by the percolation process of the domains. 相似文献
78.
Ichiro Takano Yoshiharu Arai Michiko Sasaki Yoshio Sawada Kaori Yamada Takayoshi Yagasaki Yuji Kimura 《Vacuum》2006,80(7):788-792
Biodegradable plastics can be used as conventional plastics, while on disposal they decompose to water and carbon dioxide by microorganisms existing in natural environment. Products using biodegradable plastics have recently been developed in many companies pursuing ecology. In this study, surface modification of biodegradable plastics was carried out by inert ion beams for improvement of photo deterioration under an ultraviolet ray. The hardness of biodegradable plastics tended generally to decrease with irradiation of an ultraviolet ray. In this method, the hardness of ion-bombarded biodegradable plastics was kept at an initial value under an ultraviolet ray, because the modified layer by ion bombardment intercepted an ultraviolet ray. The hardness of He+ ion-bombarded biodegradable plastics showed larger value than that of Ar+ ion bombardment. He+ ion bombardment at ion energy of 10 keV produced the suitable property with both of high transmittance of a visible ray and high interception of an ultraviolet ray in a surface layer of biodegradable plastics. 相似文献
79.
In system identification, the error evolution is composed of two decoupled parts: one is the identifying information on the current estimation residual, while the other is past arithmetic errors. Previous recursive algorithms only considered how to update current prediction errors. Up to now, research has mostly been based on recursive least-squares (RLS) methods. In this note, a general recursive identification method is proposed for discrete systems. Using this new algorithm, a recursive empirical frequency-domain optimal parameter (REFOP) estimate is established. The REFOP method has the advantage of resisting disturbance noise. Some simulations are included to illustrate the new method's reliability. 相似文献
80.
Nakano Hirofumi Ishizaka Kazuhisa Obata Motoki Kimura Keiji Kasahara Hironori 《International journal of parallel programming》2003,31(3):211-223
Effective use of cache memory is getting more important with increasing gap between the processor speed and memory access speed. Also, use of multigrain parallelism is getting more important to improve effective performance beyond the limitation of loop iteration level parallelism. Considering these factors, this paper proposes a coarse grain task static scheduling scheme considering cache optimization. The proposed scheme schedules coarse grain tasks to threads so that shared data among coarse grain tasks can be passed via cache after task and data decomposition considering cache size at compile time. It is implemented on OSCAR Fortran multigrain parallelizing compiler and evaluated on Sun Ultra80 four-processor SMP workstation using Swim and Tomcatv from the SPEC fp 95. As the results, the proposed scheme gives us 4.56 times speedup for Swim and 2.37 times on 4 processors for Tomcatv respectively against the Sun Forte HPC Ver. 6 update 1 loop parallelizing compiler. 相似文献