全文获取类型
收费全文 | 1169篇 |
免费 | 72篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 311篇 |
金属工艺 | 20篇 |
机械仪表 | 24篇 |
建筑科学 | 43篇 |
矿业工程 | 5篇 |
能源动力 | 56篇 |
轻工业 | 160篇 |
水利工程 | 11篇 |
石油天然气 | 2篇 |
无线电 | 78篇 |
一般工业技术 | 202篇 |
冶金工业 | 131篇 |
原子能技术 | 8篇 |
自动化技术 | 172篇 |
出版年
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 47篇 |
2020年 | 21篇 |
2019年 | 32篇 |
2018年 | 54篇 |
2017年 | 44篇 |
2016年 | 35篇 |
2015年 | 25篇 |
2014年 | 41篇 |
2013年 | 85篇 |
2012年 | 69篇 |
2011年 | 83篇 |
2010年 | 55篇 |
2009年 | 54篇 |
2008年 | 41篇 |
2007年 | 54篇 |
2006年 | 45篇 |
2005年 | 28篇 |
2004年 | 30篇 |
2003年 | 24篇 |
2002年 | 28篇 |
2001年 | 14篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 40篇 |
1997年 | 22篇 |
1996年 | 23篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有1242条查询结果,搜索用时 746 毫秒
1.
2.
M Jarman HM Coley IR Judson TJ Thornton DE Wilman G Abel CJ Rutty 《Canadian Metallurgical Quarterly》1993,36(26):4195-4200
In exploring the structural features which determine the antitumor activity of 2,4,6-tris-[(hydroxymethyl)methylamino]-1,3,5-triazine (trimelamol, 1), we have synthesized analogues in which the methyl groups have been replaced by the electron-withdrawing substituents 2,2,2-trifluoroethyl (5), propargyl (13), and cyanomethyl (15) via the respective tris(alkylamino)triazines 3, 12, and 14. Three mono[(hydroxymethyl)amino]triazines (4, 7, and 10) were also prepared. All the new tris(hydroxymethyl) derivatives showed cytotoxicities toward a variety of experimental rodent and human ovarian tumor cell lines similar to those shown by 1, the cyanomethyl analogue (15) having the most favorable profile. Mono(hydroxymethyl) derivatives (4 and 7) were ca. one-third as toxic. The new tris(hydroxymethyl) analogues were more stable to aqueous hydrolysis than was 1. Half-life (pH 7.5) values were, for 1, 120 min, for 5, 690 min, for 13, 450 min, and for 15, 275 min, but at pH 2.0, 15 (t1/2 350 min) was the most stable. This cyanomethyl analogue was also the most water-soluble, being comparable to 1 whereas 5 and 13 were poorly soluble. 相似文献
3.
Paulo S. André António L. Teixeira Armando N. Pinto Lara P. Pellegrino Berta B. Neto José F. Rocha Joäo L. Pinto Paulo N. Monteiro 《ETRI Journal》2006,28(2):257-259
In this letter, we will evaluate the performance degradation of a 40 km high‐speed (40 Gb/s) optical system, induced by optical fiber variations of the chromatic dispersion induced by temperature changes. The chromatic dispersion temperature sensitivity will be estimated based on the signal quality parameters. 相似文献
4.
An evaluation of the Spanish CSIC performance in Biotechnology, as compared with those of the French CNRS and the Italian
CNR, has been carried out to determine the balance between the generation of scientific knowledge and the transfer of technology.
This study shows a high scientific productivity mostly in journals with moderate impact factor, a low generation of patents
and an insufficient transfer of knowledge to the Spanish companies. Other indicators confirm the existence of competitive
human resources in biotechnological research producing scientific knowledge of interest for the development of patents and
that cooperates successfully at European level. 相似文献
5.
Abel Cadenillas 《Systems & Control Letters》2002,47(5):433-444
We consider a stochastic control problem with linear dynamics with jumps, convex cost criterion, and convex state constraint, in which the control enters the drift, the diffusion, and the jump coefficients. We allow these coefficients to be random, and do not impose any Lp-bounds on the control.
We obtain a stochastic maximum principle for this model that provides both necessary and sufficient conditions of optimality. This is the first version of the stochastic maximum principle that covers the consumption–investment problem in which there are jumps in the price system. 相似文献
6.
7.
Mario Mariani Ugo Ravasio Armando Buttafava Antonio Faucitano 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,265(1):245-250
The effect of gamma irradiation in air is investigated in two thermoplastic polyesters (PET and PEN), in order to evaluate the influence of aromatic density and the role of oxygen on radiation resistance. EPR measurements were carried out to detect radical stability against oxygen permeation and to provide radical characterization. Viscometric data reveal a different behaviour between films and thick samples. Positron annihilation spectra show a decrease of ortho-positronium intensity, which is more marked in film samples. ortho-positronium lifetime does not depend on the radiation dose. 相似文献
8.
Testing of the multi-application small light water reactor (MASLWR) passive safety systems 总被引:1,自引:0,他引:1
Jose N. Reyes John Groome Brian G. Woods Eric Young Kent Abel You Yao Yeon Jong Yoo 《Nuclear Engineering and Design》2007,237(18):1999-2005
Experimental thermal hydraulic research has been conducted at Oregon State University for the purpose of assessing the performance of a new reactor design concept, the multi-application small light water reactor (MASLWR). The MASLWR is a pressurized light water reactor design with a net output of 35 MWe that uses natural circulation in both normal and transient operation. Due to its small size, portability and modularity, the MASLWR design is well suited to help fill the potential need for grid appropriate reactor designs for smaller electricity grids as may be found in developing or remote regions. The purpose of the OSU MASLWR test facility is to assess the operation of the MASLWR under normal full operating pressure and full temperature conditions and to assess the passive safety systems under transient conditions. The data generated by the testing program will be used to assess computer code calculations and to provide a better understanding of the thermal-hydraulic phenomena in the design of the MASLWR NSSS. During this testing program, four tests were conducted at the OSU MASLWR test facility. These tests included one design basis accident and one beyond design basis accident. During the performance of these tests, plant operations to include start up, normal operation and shut down evolutions were demonstrated successfully. 相似文献
9.
Fischer U. Schenk W. Salzsieder E. Albrecht G. Abel P. Freyse E.-J. 《IEEE transactions on bio-medical engineering》1987,(8):575-582
To test the hypothesis that only an adaptive algorithm would guarantee optimal feedback control of glycemia in insulin-dependent diabetes, fasting chronically diabetic dogs at rest were subjected to short-term artificial beta cell treatment. Insulin was applied intravenously and an oral glucose load was given during the experiment. Employing the same dosing algorithm, three different control strategies were employed in a random order on different days: adaptive control (minimum variance controller, Test A), fixed command control using on-line parameter estimates (Test B), and fixed command control using off-line individually optimized dosage constants (Test C). Comparison was made to nondiabetic control animals. The glycemic profiles were entirely normal in Test A and C, but were distinctly elevated in Test B. The peripheral hyperinsulinaemia could, however, not be avoided by adaptive control. It is concluded that the restoration of physiological blood glucose control in insulin-dependent diabetes requires dosage parameters which are either continually adapted to the actual situation (adaptive control) or are optimized to meet the individual's needs. In the latter case, fixed command control may be employed. Peripheral hyperinsulinaemia cannot be avoided as long as insulin is administered by a posthepatic route. 相似文献
10.
Luis Armando Rosas Rivera Norma F. Hubele PhD Frederick P. Lawrence PhD 《Computers & Industrial Engineering》1995,29(1-4):55-58
Process capability indices (PCIs) are used in industry to assess percentages of nonconforming parts. An underlying assumption is that the output process measurements are distributed as normal random variables. When normal distributions are assumed, but different distributions are present - such as skew, heavy-tailed, and short-tailed distributions - the percentages of nonconforming parts are significantly different than the computed PCIs indicate. Data arising from nonnormal distributions can sometimes be transformed to conform to the normality assumption and the PCI's computed for the transformed data. In this paper, the effect of the transformation on the estimate of nonconforming parts is examined for three examples of nonnormal distributions - gamma, lognormal, and Weibull. The results of this experimental analysis suggest that data transformation can be useful for estimating an interval for Cpk values and the number of nonconforming parts. 相似文献