首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1145篇
  免费   37篇
  国内免费   3篇
工业技术   1185篇
  2024年   2篇
  2023年   10篇
  2022年   38篇
  2021年   34篇
  2020年   18篇
  2019年   28篇
  2018年   30篇
  2017年   30篇
  2016年   40篇
  2015年   21篇
  2014年   57篇
  2013年   85篇
  2012年   77篇
  2011年   67篇
  2010年   65篇
  2009年   60篇
  2008年   63篇
  2007年   46篇
  2006年   46篇
  2005年   35篇
  2004年   31篇
  2003年   34篇
  2002年   27篇
  2001年   21篇
  2000年   18篇
  1999年   10篇
  1998年   36篇
  1997年   18篇
  1996年   20篇
  1995年   12篇
  1994年   11篇
  1993年   13篇
  1992年   9篇
  1991年   5篇
  1990年   8篇
  1989年   5篇
  1988年   3篇
  1987年   5篇
  1986年   4篇
  1985年   5篇
  1984年   4篇
  1982年   3篇
  1981年   6篇
  1980年   4篇
  1977年   4篇
  1976年   6篇
  1974年   1篇
  1973年   4篇
  1972年   1篇
  1970年   2篇
排序方式: 共有1185条查询结果,搜索用时 15 毫秒
51.
An identification procedure for determination of coefficients of pulse transfer function is proposed. This procedure is applicable for the case when measurement noises of input and output are independent of input to a process and the variances of the noises are known only in the form of the ratio. The noises can be colored. The criterion used for identification is given by extending the mean-square equation error. The optimal estimates are obtained from the eigenvector of a linear operator which corresponds to the least eigenvalue. The theoretical analysis is given and the direction for the practical usage is suggested to use the least-square error criterion.  相似文献   
52.
This paper is concerned with the structural identification of linear multivariable systems and an interactive identification package. The structural identification is done by taking the time-invariant subsystem from the realizations of the input-output relations identified using data of disjoint time intervals, and the statistical hypothesis test is employed to determine the order, where the input-output relation is identified based on the generalized least squares method using the possibly larger model for the plant. The identification package is for the identification of the input-output relation of a linear multivariable system, for the structural identification based on the realization and for data management.  相似文献   
53.
Nishimukai M  Wakisaka T  Hara H 《Lipids》2003,38(12):1227-1235
Plasmalogens, a subclass of phospholipids, are widely distributed in human and animals, and are taken into the body as food. However, no data exist on the intestinal absorption or fate of ingested plasmalogen. Here, we determined whether dietary plasmalogen is absorbed and whether blood and tissue concentrations increased in normal male Wistar rats by using four separate experiments. Phospholipids containing more than 20 wt% of plasmalogen extracted from the bovine brain were incorporated into test diets (10–15 wt%). In experiment 1, we estimated the absorption rate by measuring the plasmalogen vinyl ether bonds remaining in the alimentary tract of rats after the ingestion of 2 g of test diet containing 91 μmol plasmalogen. The absorption rate of plasmalogen was nearly 80 mol% after 4 h, comparable to the total phospholipid content in the test diet. In experiment 2, we observed no degradation of the plasmalogen vinyl ether bonds under in vitro conditions simulating those of the stomach and small intestinal lumen. In experiment 3 we confirmed a comparable absorption (36 mol%) by using a closed loop of the upper small intestine in anesthetized rats 90 min after injecting a 10 wt% brain phospholipid emulsion. Feeding a test diet containing 10 wt% brain phospholipids for 7 d increased plasmalogen concentration threefold in blood plasma and by 25% in the liver; however, no increases were seen in blood cells, skeletal muscle, brain, lungs, kidneys, or adipose tissue (experiment 4). We concluded that dietary plasmalogen is absorbed from the intestine and contributes to a large increase in plasmalogen levels in blood plasma.  相似文献   
54.
中国液态锂铅包层材料研究进展   总被引:2,自引:0,他引:2  
液态锂铅包层是国际上普遍关注和最有发展潜力的聚变堆包层概念设计之一,而包层材料是液态锂铅包层的核心问题之一.目前,液态锂铅包层普遍选用低活化铁素体/马氏体钢(RAFM钢)作为结构材料,液态锂铅作为中子倍增剂及氚增殖剂.另外,部分设计采用了耐高温、电绝缘流道插件作为功能材料,以降低磁流体动力学效应及提高冷却剂出口温度(高于700℃).为适应液态包层的发展需求,中国科学院等离子体物理研究所FDS团队联合国内外相关研究单位,进行了具有中国自主知识产权的中国低活化马氏体钢(CLAM钢)及液态锂铅包层功能材料研发,并开展了锂铅热对流及强迫对流回路的设计、研制及腐蚀实验研究,以研究液态金属锂铅的流动特性及其与结构和功能材料的相容性.同时建立了聚变堆材料数据库平台,为促进中国聚变堆液态包层及材料技术的研究和发展提供数据支持.  相似文献   
55.
Titanium dioxide (TiO2) powder-containing sheet composites, called TiO2 sheet, were prepared by a papermaking technique, and their photocatalytic efficiency was investigated. The TiO2 powders were homogeneously scattered over the fiber-mix networks tailored within the catalyst sheet. Under UV irradiation, the TiO2 paper could decompose p-hydroxyacetophenone (p-HAP), although the degradation efficiency by the TiO2 sheet was lower than that by the TiO2 powder. Scanning electron microscopy revealed that coverage of the TiO2 particles inside the sheet by alumina binder which was used to improve the sheet strength caused the deterioration of the photocatalytic performance. Internal addition of alumina binder made the TiO2 sheet porous and such a TiO2 sheet exhibited high photocatalytic performance equivalent to that of TiO2 powder. The porous structure of TiO2 sheet might contribute to effective transport of p-HAP to the surface of TiO2 particles inside the sheet, resulting in high degradation performance. In addition, TiO2 sheet prepared using TiO2 sol showed higher photocatalytic efficiency than TiO2 powder and it was indicated that the porous sheet structure might provide suitable conditions for TiO2 catalysis for photodecomposition.  相似文献   
56.
This study estimates pretreatment-posttreatment effect size benchmarks for the treatment of major depression in adults that may be useful in evaluating psychotherapy effectiveness in clinical practice. Treatment efficacy benchmarks for major depression were derived for 3 different types of outcome measures: the Hamilton Rating Scale for Depression (M. A. Hamilton, 1960, 1967), the Beck Depression Inventory (A. T. Beck, 1978; A. T. Beck & R. A. Steer, 1987), and an aggregation of low reactivity-low specificity measures. These benchmarks were further refined for 3 conditions: treatment completers, intent-to-treat samples, and natural history (wait-list) conditions. The study confirmed significant effects of outcome measure reactivity and specificity on the pretreatment-posttreatment effect sizes. The authors provide practical guidance in using these benchmarks to assess treatment effectiveness in clinical settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
57.
This paper presents a high-speed, high-sensitivity 512times512 CMOS image sensor with column parallel cyclic 12-bit ADCs and a global electronic shutter. Each pixel has a charge amplifier for high charge-to-voltage conversion gain despite of using a large-size photodiode, and two sample-and-hold stages for the global shutter and fixed pattern noise (FPN) canceling. High-speed column-parallel cyclic ADC arrays with 12-bit resolution having a small layout size of 0.09 mm 2 are integrated at both sides of image array. A technique for accelerating the conversion speed using variable clocking and sampling capacitance is developed. A digital gain control function using 14-bit temporal digital code is also set in the column parallel ADC. The fabricated chip in 0.25-mum CMOS image sensor technology achieves the full frame rate in excess of 3500 frames/s. The in-pixel charge amplifier achieves the optical sensitivity of 19.9 V/lxmiddots. The signal full scale at the pixel output is 1.8 V at 3.3-V supply and the noise level is measured to be 1.8mVrms, and the resulting signal dynamic range is 60 dB  相似文献   
58.
This paper presents a low-power low-voltage 10-bit 100-MSample/s pipeline analog-to-digital converter (ADC) using capacitance coupling techniques. A capacitance coupling sample-and-hold stage achieves high SFDR with 1.0-V supply voltage at a high sampling rate. A capacitance coupling folded-cascode amplifier effectively saves the power consumption of the gain stages of the ADC in a 90-nm digital CMOS technology. The SNDR and the SFDR are 55.3 dB and 71.5 dB, respectively, and the power consumption is 33 mW  相似文献   
59.
In previous studies, various stabilizing control methods for humanoids during the stance phase while hopping and running were proposed. Although these methods contribute to stability while hopping and running, it is possibility that the control during the flight phase could also affect the stability. In this study, we investigated whether the control during the flight phase can affect the stability of a humanoid while running. To achieve stable hopping, we developed a control system that accounts for the angular momentum of the whole body during the flight phase. In this system, the angular momentum generated by the motion of the lower body in each time interval is calculated during the flight phase, and the trunk joints are controlled to generate the angular momentum necessary to compensate for the deviation of the waist posture, which is used as the reference point for the motion coordinate system of the robot. Once the proposed control system was developed and simulated, we found that the hopping duration in the unconstrained state was extended.  相似文献   
60.
Niobium- or vanadium-doped anatase sols were prepared by hydrothermal treatment of 0.1 mol/dm3 peroxotitanium complex aqueous solutions dissolving 0–10 mol% niobium or vanadium at 100°C for 8 h. Niobium-doping caused the increase of lattice constants of anatase and the shape change of anatase crystal from spindle-like to cubic-like structure, but no change of the optical absorbance. Vanadium-doping caused the decrease of lattice constant of c -axis, the miniaturization of anatase crystal and the increase of optical absorbance at the wavelength from 350–700 nm.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号