全文获取类型
收费全文 | 2878篇 |
免费 | 61篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 230篇 |
金属工艺 | 23篇 |
机械仪表 | 54篇 |
建筑科学 | 25篇 |
矿业工程 | 6篇 |
能源动力 | 32篇 |
轻工业 | 106篇 |
水利工程 | 5篇 |
石油天然气 | 15篇 |
无线电 | 68篇 |
一般工业技术 | 133篇 |
冶金工业 | 2121篇 |
原子能技术 | 8篇 |
自动化技术 | 93篇 |
出版年
2023年 | 9篇 |
2022年 | 18篇 |
2021年 | 33篇 |
2020年 | 26篇 |
2019年 | 31篇 |
2018年 | 28篇 |
2017年 | 42篇 |
2016年 | 35篇 |
2015年 | 24篇 |
2014年 | 31篇 |
2013年 | 81篇 |
2012年 | 44篇 |
2011年 | 40篇 |
2010年 | 51篇 |
2009年 | 57篇 |
2008年 | 38篇 |
2007年 | 30篇 |
2006年 | 33篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 14篇 |
2002年 | 21篇 |
2001年 | 11篇 |
2000年 | 12篇 |
1999年 | 92篇 |
1998年 | 684篇 |
1997年 | 375篇 |
1996年 | 246篇 |
1995年 | 151篇 |
1994年 | 120篇 |
1993年 | 120篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 17篇 |
1989年 | 26篇 |
1988年 | 25篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 21篇 |
1984年 | 1篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 63篇 |
1976年 | 96篇 |
1975年 | 4篇 |
1964年 | 1篇 |
排序方式: 共有2942条查询结果,搜索用时 109 毫秒
81.
M Delgado EJ Munoz-Elias Y Kan I Gozes M Fridkin DE Brenneman RP Gomariz D Ganea 《Canadian Metallurgical Quarterly》1998,273(47):31427-31436
82.
BK Yoder WG Richards C Sommardahl WE Sweeney EJ Michaud JE Wilkinson ED Avner RP Woychik 《Canadian Metallurgical Quarterly》1996,50(4):1240-1248
Autosomal recessive polycystic kidney disease (ARPKD) is characterized by the formation of large collecting tubule and ductular cysts that often result in renal insufficiency within the first decade of life. Understanding the process leading to cyst formation will require the identification and characterization of genes involved in the etiology of this disease. In this regard, we previously described the generation of a mouse model (TgN737Rpw) for ARPKD and the cloning of a candidate gene. Here we show direct involvement of the Tg737 gene in collecting duct cyst formation by expressing the wild-type Tg737 cDNA as a transgene in TgN737Rpw mutants. In contrast to TgN737Rpw mutants, the "rescued" animals survive longer, have normal renal function and normal localization of the EGFr to the basolateral surfaces of collecting duct epithelium. 相似文献
83.
P Gennis L Miller EJ Gallagher J Giglio W Carter N Nathanson 《Canadian Metallurgical Quarterly》1996,3(6):568-573
Thirty-five male patients, aged 34-79 yr, with definite rheumatoid arthritis (RA) were recruited from out-patient clinics and randomized to receive monthly injections of testosterone enanthate 250 mg or placebo as an adjunct therapy for 9 months. Endpoints included disease activity parameters and bone mineral density (BMD). At baseline, there were negative correlations between the ESR and serum testosterone (r = -0.42, P < 0.01) and BMD (hip, r = -0.65, P < 0.01). A total of 29.6% of all patients had at least one vertebral fracture, most having multiple fractures. Back pain, however, was not more prevalent in fracture patients (55% vs 50%). Disease activity was significantly higher in the fracture group (joint score P < 0.05, rheumatoid factor P < 0.01). Thirty patients completed the trial, 15 receiving testosterone and 15 receiving placebo. There were significant rises in serum testosterone, dihydrotestosterone and oestradiol in the treatment group. There was no significant effect of treatment on disease activity overall, five patients receiving testosterone underwent a "flare'. Differences in mean BMD following testosterone or placebo were non-significant (spine: +1.2% vs -1.1%; femur: -0.3% vs +0.3%). There was no suggestion of a positive effect of testosterone on disease activity in men with RA. 相似文献
84.
An ant colony optimization approach to a permutational flowshop scheduling problem with outsourcing allowed 总被引:1,自引:0,他引:1
This paper deals with the scheduling problem of minimizing the makespan in a permutational flowshop environment with the possibility of outsourcing certain jobs. It addresses this problem by means of the development of an ant colony optimization-based algorithm. This new algorithm, here named as flowshop ant colony optimization is composed of two combined ACO heuristics. The results show that this new approach can be used to solve the problem efficiently and in a short computational time. 相似文献
85.
Luiz Augusto da Cruz Meleiro Fernando José Von Zuben Rubens Maciel Filho 《Engineering Applications of Artificial Intelligence》2009,22(2):201-215
In the present work, a constructive learning algorithm was employed to design a near-optimal one-hidden layer neural network structure that best approximates the dynamic behavior of a bioprocess. The method determines not only a proper number of hidden neurons but also the particular shape of the activation function for each node. Here, the projection pursuit technique was applied in association with the optimization of the solvability condition, giving rise to a more efficient and accurate computational learning algorithm. As each activation function of a hidden neuron is defined according to the peculiarities of each approximation problem, better rates of convergence are achieved, guiding to parsimonious neural network architectures. The proposed constructive learning algorithm was successfully applied to identify a MIMO bioprocess, providing a multivariable model that was able to describe the complex process dynamics, even in long-range horizon predictions. The resulting identification model was considered as part of a model-based predictive control strategy, producing high-quality performance in closed-loop experiments. 相似文献
86.
PURPOSE: The effect of systematic and stochastic setup error on the dose delivered to the gap region for the three field radiation treatment of medulloblastoma is studied. The consequences of such setup error is discussed. METHODS AND MATERIALS: The treatment of medulloblastoma is typically a 3 field technique, in which two lateral cranial fields are matched with a spine field. The x-ray dose delivered to the region between the matched fields depends upon the gap size. The choice of the gap width between the cranial and spinal fields is controversial. It is currently a compromise between minimizing the risk of dose hot spots to the spine, and the associated clinical complications, as well as the magnitude of cold spots (underdosing) across the gap, with the associated risk of disease recurrence. In this paper, we examine the effect of gap width with a moving junction, referred to as "field feathering", on the dose across the field junction for a 6MV photon beam. In addition, we have studied 129 portal films and 40 simulation films to assess the accuracy and precision of patient setup during treatment with a plan involving feathered fields. Selected landmarks observable on both portal and simulation films were identified and the variation in the distances to the field edges measured. The distribution of patient setup error was convoluted with the beam profiles for a 6MV linac. These convoluted field edges were used obtain dose profiles across the gap region as a function of gap separation. The consequences for therapy are discussed. In addition, analysis of patient setup error on an alternative treatment involving beam modifiers to broaden the beam penumbra is discussed. RESULTS: The magnitude of the spatial stochastic and systematic setup error was determined to be approximately three and two millimeters respectively. The dosimetric consequences of patient setup error lead to over and under dosing in the spinal gap region for the three field technique. The degree of under or over dose depends on the nature and magnitude of the patient setup error. CONCLUSIONS: The effect of patient setup error can lead to significant dosimetric errors in the dose to the gap region depending on the magnitude of the setup errors. The effective over and under dose can be compensated by the use beams modifiers such as a beam spoiler or vibrating jaws. 相似文献
87.
Oliveira T.C. Filho I.M. de Lucena C.J.P. Alencar P.S.C. Cowan D.D. 《IEEE transactions on pattern analysis and machine intelligence》2004,30(3):145-159
Object-oriented frameworks are currently regarded as a promising technology for reusing designs and implementations. However, developers find there is still a steep learning curve when extracting the design rationale and understanding the framework documentation during framework instantiation. Thus, instantiation is a costly process in terms of time, people, and other resources. These problems raise a number of questions including: "How can we raise the level of abstraction in which the framework instantiation is expressed, reasoned about and implemented?" "How can the same high-level design abstractions that were used to develop the framework be used during framework instantiation instead of using source code as is done currently?" "How can we define extended design abstractions that can allow framework instantiation to be explicitly represented and validated?" We present an approach to framework instantiation based on software processes that addresses these issues. Our main goal is to represent the framework design models in an explicit and declarative way, and support changes to this design based on explicit instantiation tasks based on software processes while maintaining system integrity, invariants, and general constraints. In this way, the framework instantiation can be performed in a valid and controlled way. 相似文献
88.
L.S.L. Fernandes F.C. Moraes Filho J.B.A. Paulo J.A. Oliveira 《Control Engineering Practice》2013,21(8):1121-1127
The mixer-settler based on phase inversion (MSBPI) is a system used for treatment of wastewaters in order to reduce the content of oils and greases from wastewaters produced in oil industry. Its operation principle combines mixing, extraction and separation by decantation in a unique process. In particular, for control purpose, the level of the interface between organic solvent and water, in the separation section, is a critical variable to guarantee performance and security during operation of the MSBPI. In this work, an image-based detector to monitor the organic solvent–water interface level is proposed and a feedback control loop for the process is presented. Initially, a conventional controller (PID) was implemented and, subsequently, a strategy of gain scheduling adaptive control was developed in order to improve the process response in closed-loop. The experimental results showed that the adaptive control presented an efficient performance, even when disturbances of significant magnitude were applied to the process. 相似文献
89.
90.