全文获取类型
收费全文 | 2726篇 |
免费 | 232篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 39篇 |
化学工业 | 775篇 |
金属工艺 | 58篇 |
机械仪表 | 89篇 |
建筑科学 | 101篇 |
矿业工程 | 9篇 |
能源动力 | 102篇 |
轻工业 | 552篇 |
水利工程 | 17篇 |
石油天然气 | 18篇 |
无线电 | 142篇 |
一般工业技术 | 368篇 |
冶金工业 | 272篇 |
原子能技术 | 27篇 |
自动化技术 | 393篇 |
出版年
2024年 | 6篇 |
2023年 | 29篇 |
2022年 | 78篇 |
2021年 | 185篇 |
2020年 | 89篇 |
2019年 | 109篇 |
2018年 | 121篇 |
2017年 | 128篇 |
2016年 | 140篇 |
2015年 | 72篇 |
2014年 | 133篇 |
2013年 | 228篇 |
2012年 | 171篇 |
2011年 | 195篇 |
2010年 | 150篇 |
2009年 | 145篇 |
2008年 | 126篇 |
2007年 | 93篇 |
2006年 | 86篇 |
2005年 | 55篇 |
2004年 | 48篇 |
2003年 | 62篇 |
2002年 | 43篇 |
2001年 | 34篇 |
2000年 | 15篇 |
1999年 | 20篇 |
1998年 | 83篇 |
1997年 | 50篇 |
1996年 | 34篇 |
1995年 | 28篇 |
1994年 | 25篇 |
1993年 | 25篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 7篇 |
排序方式: 共有2962条查询结果,搜索用时 296 毫秒
991.
Perfilino E. Ferreira Júnior Jos R.A. Torreo Paulo C.P. Carvalho 《Pattern recognition letters》2009,30(14):1321-1334
When filtering an input image, the Green’s functions of matching equations are capable of inducing a broad class of motions, a property that has led to their use in several computer graphics and computer vision applications. In all such applications, the Green’s functions of second-order differential equations have been considered, even though no justification has been given for their preference over simpler, first-order equations. Here we present a study of first-order one-dimensional matching equations, both in the uniform and in the affine motion models. Comparing their Green’s functions with those of the corresponding second-order cases, we find evidence for the latter’s superiority in motion synthesis. We also propose and discuss a general discretization scheme for Green’s functions of one-dimensional matching equations, showing that the affine motion model is particularly sensitive to the sampling frequency. In this case, we advocate the use of area sampling, for allowing realistic motion simulations. 相似文献
992.
In earlier work, we have shown that two variants of weak fairness can be expressed comparatively easily in the timed process
algebra PAFAS. To demonstrate the usefulness of these results, we complement work by Walker (Form Asp Comput 1:273–292, 1989)
and study the liveness property of Dekker’s mutual exclusion algorithm within our process algebraic setting. We also present
some results that allow to reduce the state space of the PAFAS process representing Dekker’s algorithm, and give some insight
into the representation of fair behaviour in PAFAS. 相似文献
993.
Evaluation of a three-dimensional model for the prediction of heat transfer in power station boilers
This paper reports an evaluation of a full three-dimensional mathematical model of a power station boiler with emphasis on the heat transfer phenomena. The model is based on the numerical solution of the equations governing conservation of mass, momentum and energy and transport equations of scalar quantities. The radiative heat transfer is modelled using the discrete transfer method. The model was applied to a power station boiler of the Portuguese Electricity Utility where an experimental study was recently carried out. Measurements of gas temperature, species concentrations and incident heat fluxes to the walls were compared with the predictions for standard operating conditions, partial load operation and low excess air conditions. Comparison of the results with the measurements has shown that in general a good agreement was achieved, but in some cases only qualitative agreement was found. More detailed measurements would be needed to allow a better evaluation of the model and to identify the sources of discrepancy. Nevertheless, the model proved to be a useful tool for the analysis of the heat transfer in utility boilers. 相似文献
994.
995.
996.
Conflicts over Water Resource Management in Brazil: A Case Study of Inter-Basin Transfers 总被引:1,自引:1,他引:0
Developing countries such as Brazil, with limited track-records in dealing with environmental conflicts on a participatory
basis, or whose legal frameworks establishing water resource management practices have been introduced only recently, need
mechanisms that streamline and strengthen democratic negotiating and decision processes. Increasingly common worldwide, transferring
water is developing into a specific source of disputes whose solutions are becoming significant, particularly in the developing
countries. This paper analyzes the application of the strategic choice methodology in a dispute over transferring water between
two river basins, which is a situation not covered by specific legislation in Brazil. This analysis leads to the conclusion
that the application of this methodology is particularly relevant in cases such as this, where decisions are taken on an incremental
basis over time, within a context of political, administrative and legal uncertainties. 相似文献
997.
OBJECTIVES: The objectives of this paper are to review the structure of dentine as it pertains to adhesive bonding and to describe the importance of resin permeation into dentinal tubules and into spaces created between collagen fibrils by acid-etching during resin bonding. The advantages and disadvantages of separate acid-etching, priming and adhesive applications are discussed. DATA SOURCES: Although not an exhaustive review, the concepts included in the review were obtained from the dentine bonding literature. STUDY SELECTION: Attempts were made to critically evaluate what is known about dentine permeability and adhesion and what remains to be discovered. Speculations were made on a number of controversial issues that are not yet resolved. CONCLUSIONS: Acid-etching of dentine produces profound changes in the chemical composition and physical properties of the matrix which can influence the quality of resin-dentine bonds, their strength and perhaps their durability. 相似文献
998.
JC Winck L Delgado T Shiang A Carvalho FF Rodrigues 《Canadian Metallurgical Quarterly》1996,51(2):120-122
BACKGROUND: The effects of abrupt discontinuation and tapering of total parenteral nutrition (TPN) on glucose concentration were compared in patients < 3 years of age. METHODS: Serial glucose concentrations were measured over 120 minutes after abrupt discontinuation as compared with tapering (decreasing infusion rate by 50% for 1 hour before discontinuation). Serial insulin concentrations were measured after abrupt discontinuation. RESULTS: There was a significantly greater decrease in glucose concentration from baseline at 30 minutes after abrupt discontinuation as compared with tapering. Fifty-five percent (6/11) of the patients developed hypoglycemia (glucose concentration < 40 mg/dL) after abrupt discontinuation. Age, glucose infusion rate, and serum insulin concentrations were not predictive of the development of hypoglycemia. The tapering regimen did not prevent hypoglycemia, which developed in 20% (2/10). CONCLUSION: The high incidence of hypoglycemia after TPN discontinuation in children < 3 years of age requires monitoring of serum glucose concentration when initiating intermittent TPN until tolerance is documented. 相似文献
999.
Eduardo N. Dvorkin Rita G. Toscano 《International journal for numerical methods in engineering》2003,58(12):1803-1816
A new rigid‐viscoplastic model that includes the effect of thermal strains when modelling steady‐state metal‐forming processes was developed. A symmetric approximation to the resulting non‐symmetric stiffness matrix was derived. The thermo‐mechanical flow formulation was implemented using the pseudo‐concentrations technique. The new formulation was numerically tested showing that it provides reliable results. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
1000.
Alfredo Aires Eduardo Rosa Rosa Carvalho 《Journal of the science of food and agriculture》2006,86(10):1512-1516
Broccoli (Brassica oleracea L. var. italica cv. Marathon) sprouts are a rich source of glucosinolates, particularly 4‐methylsulfinylbutyl glucosinolate (glucoraphanin), the precursor of the chemoprotective isothiocyanate, sulforaphane. Sulfur and nitrogen fertilization have been shown to influence the pattern and levels of glucosinolates in mature broccoli, but little information is available on the fertilization of sprouts, a transient stage of broccoli growth, which have been recommended for salads. Therefore, an experiment was set up to evaluate the effect of N and S fertilization on the glucosinolate content of the aerial part and roots of broccoli sprouts. Nitrogen was tested at 0, 45.5, 91.0 mg L?1 and sulfur at 0, 14.6 and 29.2 mg L?1. The results showed that total glucosinolates in the aerial part were significantly higher (P < 0.001) than in the roots. The major glucosinolates in the aerial part were 4‐methylsulfinylbutyl and 3‐methylsulfinylpropyl whereas in the roots they were 2‐phenylethyl and 4‐methylthiobutyl. Fertilization of broccoli sprouts had a significant (P < 0.001) detrimental effect on the levels of aliphatic glucosinolates whereas the opposite was noted for indole and aromatic glucosinolates, for some of the fertilization combinations tested. Overall, the results indicate that broccoli sprouts do not benefit from fertilization. Copyright © 2006 Society of Chemical Industry 相似文献