全文获取类型
收费全文 | 2654篇 |
免费 | 64篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 7篇 |
综合类 | 3篇 |
化学工业 | 166篇 |
金属工艺 | 9篇 |
机械仪表 | 14篇 |
建筑科学 | 35篇 |
矿业工程 | 1篇 |
能源动力 | 30篇 |
轻工业 | 147篇 |
水利工程 | 13篇 |
石油天然气 | 10篇 |
无线电 | 51篇 |
一般工业技术 | 94篇 |
冶金工业 | 2032篇 |
原子能技术 | 4篇 |
自动化技术 | 106篇 |
出版年
2023年 | 2篇 |
2022年 | 17篇 |
2021年 | 17篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 25篇 |
2017年 | 18篇 |
2016年 | 35篇 |
2015年 | 24篇 |
2014年 | 46篇 |
2013年 | 44篇 |
2012年 | 43篇 |
2011年 | 41篇 |
2010年 | 43篇 |
2009年 | 21篇 |
2008年 | 35篇 |
2007年 | 41篇 |
2006年 | 32篇 |
2005年 | 18篇 |
2004年 | 37篇 |
2003年 | 18篇 |
2002年 | 21篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 66篇 |
1998年 | 711篇 |
1997年 | 330篇 |
1996年 | 243篇 |
1995年 | 123篇 |
1994年 | 113篇 |
1993年 | 129篇 |
1992年 | 17篇 |
1991年 | 28篇 |
1990年 | 30篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 27篇 |
1986年 | 17篇 |
1985年 | 14篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1978年 | 1篇 |
1977年 | 27篇 |
1976年 | 108篇 |
1971年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有2722条查询结果,搜索用时 0 毫秒
121.
Uncertainty evaluation for repeated measurements has been discussed previously by various researchers and two ways of proceeding were proposed, dependent upon whether or not there is a significative difference in the individual results of repeated measurements. In this paper, the analysis of variance perspective is used to clarify and unify the ideas of previous works. It is shown that the two above-mentioned approaches involve the use of two different estimators for the evaluation of the random component of the standard uncertainty. Based on this, the efficiency of the two estimators is compared in order to propose a procedure for correct and efficient use of previous approaches to perform the uncertainty evaluation for repeated measurements. 相似文献
122.
The use of online analytical processing (OLAP) systems as data sources for data mining techniques has been widely studied and has resulted in what is known as online analytical mining (OLAM). As a result of both the use of OLAP technology in new fields of knowledge and the merging of data from different sources, it has become necessary for models to support imprecision. We, therefore, need OLAM methods which are able to deal with this imprecision. Association rules are one of the most used data mining techniques. There are several proposals that enable the extraction of association rules on DataCubes but few of these deal with imprecision in the process. The main problem observed in these proposals is the complexity of the rule set obtained. In this paper, we present a novel association rule extraction method that works over a fuzzy multidimensional model which is capable of representing and managing imprecise data. Our method deals with the problem of reducing the complexity of the result obtained by using fuzzy concepts and a hierarchical relation between them. 相似文献
123.
Maria Concepcion Serrano Eun Ji Chung Guillermo. A. Ameer 《Advanced functional materials》2010,20(2):192-208
When elastomers were first proposed as useful materials for regenerative medicine a few decades ago, their high versatility and suitability for a diverse and wide range of in vivo applications could not have been predicted. Due to their ability to recover after deformation, these materials were first introduced in tissue engineering in an attempt to mimic the mechanical properties of the extracellular matrix. Furthermore, elastomeric characteristics have been described as important criteria for cell interaction by modulating cellular behavior. From soft to hard tissues, elastomers have demonstrated degradation, mechanical, and biocompatibility requirements in accordance with the target tissue. In this feature article, biodegradable synthetic polyester elastomers that have been reported in the literature are discussed, with special focus on those that show promise for in vivo tissue replacement. Their satisfactory performance in vivo shows the promise of elastomers for use in regenerative medicine. However, further investigation is required to demonstrate the prospect of elastomer‐based therapies in clinical trials. 相似文献
124.
Marissa Vargas‐Ramirez Antonio Romero‐Serrano Rodolfo Morales Miguel Angeles‐Hernandez Federico Chavez‐Alcala Javier Castro‐Arellano 《国际钢铁研究》2001,72(5-6):173-181
A mathematical model earlier proposed has been improved to predict the kinetics of multicomponent reactions in the hot metal pretreatment through the injection of reactive fluxes. It is assumed that there are two reaction zones along the flux injection operation: a transitory reaction between the rising particles and the bulk metal, and the permanent reaction between the metal and the top slag. A criterion to estimate the fraction of solids which will react with molten iron in a three‐phase jet (gas‐solid‐liquid) was considered; this fraction of solids carries out the transitory reaction. The model also takes into account the thermodynamic changes produced in the metal and slag due to the chemical reactions. Calculated results of the model are in good agreement with experimental results for the desulfurization of hot metal through the injection of CaO‐SiO2‐CaF2‐FeO‐Na2O reagents at 1400 ‐ 1450 °C. Two kinds of hot metal were tested, one with a low carbon mass content of 3 % and the other with a high carbon mass content of 4.5 %. 相似文献
125.
SH Bernstein J Fay S Frankel N Christiansen MR Baer C Jacobs C Blosch R Hanna G Herzig 《Canadian Metallurgical Quarterly》1999,43(2):141-144
PURPOSE: The recombinant human interleukin-1 receptor (rhu IL-1R) is a soluble truncated form of the type 1 full-length membrane-bound receptor that binds IL-1 with identical affinity to that of the membrane form. As such, it may have clinical potential by sequestering IL-1, thereby preventing it from binding to its membrane-bound receptor and eliciting a biological effect. As IL-1 has been shown to regulate leukemic cell proliferation in an autocrine fashion, a phase I trial of rhu IL-1R was conducted in patients with relapsed and refractory acute myeloid leukemia (AML). METHODS: The study group comprised 11 patients who were sequentially treated on one of three dose levels, receiving a single intravenous (i.v.) bolus dose on day 1 followed by 13 days of daily subcutaneous (s.c.) injections with the option of an additional 14 days of treatment if a response of stable disease or better was achieved. Dose level 1 i.v. bolus 500 microg/m2, s.c. dose 250 microg/m2 per day (five patients); dose level 2 i.v. bolus 1000 microg/m2, s.c. dose 500 microg/m2 per day (three patients); dose level 3 i.v. bolus 2000 microg/m2, s.c. dose 1000 microg/m2 per day (three patients). Owing to limited drug availability, the study was designed to only examine these three dose levels. RESULTS: rhu IL-IR was well tolerated. There was no grade 3 or 4 non-hematological toxicity related to the study drug and the maximum tolerated dose was not reached. No IL-1R-blocking antibodies developed during the course of the study. Serum levels of IL-1beta, IL-6 and TNF were undetectable before, during and after rhu IL-IR administration. The terminal half-life after i.v. dosing was at least 7-12 h, and after s.c. dosing 2-4 days. Serum levels of rhu IL-1R up to 360- and 25-fold those of pretreatment levels were achieved after i.v. and s.c. dosing respectively. No patient had a complete, partial or minor response to treatment; four had stable disease and seven had progressive disease. CONCLUSIONS: rhu IL-1R therapy was safe but did not have any apparent antileukemic effect at the doses administered. 相似文献
126.
127.
Anders Olsson Jan Oscarsson Erik Serrano Bo Källsner Marie Johansson Bertil Enquist 《Holz als Roh- und Werkstoff》2013,71(3):319-333
Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3,600 mm³, a coefficient of determination as high as 0.68–0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles. 相似文献
128.
Mona Ibrahim Karine Groenen Serrano Laure Noe Ccile Garcia Marc Verelst 《Electrochimica acta》2009,55(1):155-158
Nanoparticles of magnetites (Fe3O4) are synthesized with a new process based on electro-precipitation in ethanol medium. A mechanism pathway is proposed consisting of a Fe(OH)3 precipitation followed by the reduction of iron hydroxide to magnetite in the presence of hydroxyl ions which are generated at the cathode. 相似文献
129.
DD Roman SH Kubo S Ormaza GS Francis AJ Bank SJ Shumway 《Canadian Metallurgical Quarterly》1997,19(5):692-697
Seventeen patients with severe cardiomyopathy underwent neuropsychological evaluation prior to and at least 1 year after successful heart transplantation. Study candidates were screened, and individuals with a history of stroke, cardiac arrest, or medical and neurological conditions which might affect brain function were excluded. Pre-transplant testing revealed normal intelligence and normal attentional, language, and executive abilities but impaired recent memory. Following heart transplant, memory functioning improved significantly, reaching normal levels. Other cognitive abilities remained unchanged. Results suggest that cardiomyopathy is associated with mesial temporal dysfunction, possibly attributable to inadequate or reduced cerebral blood flow and related hypometabolism. This cerebral dysfunction is potentially reversible following successful transplantation, which restores cardiac output and cerebrovascular perfusion. 相似文献
130.