全文获取类型
收费全文 | 3548篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
综合类 | 3篇 |
化学工业 | 26篇 |
金属工艺 | 3篇 |
机械仪表 | 2篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 3篇 |
轻工业 | 12篇 |
石油天然气 | 1篇 |
武器工业 | 2篇 |
无线电 | 15篇 |
一般工业技术 | 9篇 |
冶金工业 | 3440篇 |
自动化技术 | 28篇 |
出版年
2022年 | 2篇 |
2020年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 1篇 |
2011年 | 32篇 |
2010年 | 5篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 122篇 |
1998年 | 1127篇 |
1997年 | 657篇 |
1996年 | 392篇 |
1995年 | 198篇 |
1994年 | 179篇 |
1993年 | 231篇 |
1992年 | 14篇 |
1991年 | 28篇 |
1990年 | 28篇 |
1989年 | 42篇 |
1988年 | 36篇 |
1987年 | 33篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 22篇 |
1981年 | 15篇 |
1980年 | 27篇 |
1979年 | 3篇 |
1978年 | 14篇 |
1977年 | 78篇 |
1976年 | 141篇 |
1975年 | 5篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1955年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有3557条查询结果,搜索用时 15 毫秒
121.
122.
This paper describes a tool to aid the development of computer vision applications for pixel-level diagnosis. A conceptual framework for constructing pixel processors is described. The proposed tool is based on two domains: one deals with numerical images, named features, and the other deals with symbolic images, named classes. A reduced set of image and operator types is defined. Based on it, an object-oriented language is described. The main objects define features and classes and their associated operators, namely procedures, classifiers, and rules. All system control is goal oriented and is designed to provide symbolic images as results when a request is received from a higher level of the image understanding system. Some knowledge engineering concepts, such as certainty control and instances, are also included. 相似文献
123.
综述了近年来以环己烯、环己酮、环己醇或环己烷等作原料,以过氧化氢或氧气等为氧源,采用不同的催化体系清洁合成己二酸的新进展.指出:在这些方法中,改性的分子筛及负载型催化剂-双氧水体系将是今后己二酸清洁合成的重点研究方向. 相似文献
124.
弱碱三元复合驱与强碱三元复合驱的对比 总被引:9,自引:0,他引:9
三元复合驱即将成为大庆油田的主导开发技术,为了推荐出合适的三元复合驱类型,对比研究了弱碱三元复合驱与强碱三元复合驱。研究表明,弱碱三元复合驱可以比水驱提高采收率20%以上,与强碱三元复合驱相当;弱碱三元复合驱与强碱三元复合驱乳化液粘度都超过100 mPa.s,两种类型三元复合乳化能力相差不多,甚至弱碱三元复合驱乳化能力还略强一些;在注采能力、采油速度方面,弱碱三元复合驱甚至高于强碱三元复合驱;特别是在结垢程度上,弱碱三元复合驱比强碱三元复合驱弱,对生产井的影响较小。因此,在三元复合驱推广应用时应当选用弱碱三元复合驱。 相似文献
125.
A.I. Abou-AlyR. Awad S.A. MahmoudM.ME. Barakat 《Journal of Alloys and Compounds》2011,509(27):7381-7388
This work studied X-ray powder diffraction (XRD), electrical resistivity and electron paramagnetic resonance (EPR) measurements for Bi1.8Pb0.4Sr2Ca2.1Cu3−xRuxO10+δ (0.0 ≤ x ≤ 0.4) superconducting samples. XRD analysis and electrical resistivity data showed that the low-content of Ru, x ≤ 0.05, enhanced both the phase formation and the superconducting transition temperature of (Bi, Pb)-2223 phase. A phase change from (Bi, Pb)-2223 phase to (Bi, Pb)-2212 phase was reported for x ≥ 0.15. Two EPR lines were observed for 0.0 ≤ x ≤ 0.075, indicating the presence of both (Bi, Pb)-2223 and (Bi, Pb)-2212 phases. While, one EPR line was observed for x ≥ 0.15, corresponding to the (Bi, Pb)-2212 phase formation. The number of spins (N) participating in the resonance and its spin paramagnetic susceptibility (χ), for the two phases, were calculated as a function of both Ru-content and temperature. In addition, we reported the variation of activation energy (Ea), Curie constant (C), Curie temperature (θ) and effective magnetic moment (μ) with Ru-content. 相似文献
126.
High avidity CTLs for two self-antigens demonstrate superior in vitro and in vivo antitumor efficacy
HJ Zeh D Perry-Lalley ME Dudley SA Rosenberg JC Yang 《Canadian Metallurgical Quarterly》1999,162(2):989-994
A majority of the human tumor-associated Ags characterized to date are derived from nonmutated "self"-proteins. Little is currently understood about the nature of the self-reactive lymphocytes that recognize these Ags. We recently characterized two nonmutated tumor-associated Ags for the B16 murine melanoma: tyrosinase-related protein-2 (TRP-2) and the endogenous retroviral envelope protein, p15E. We previously reported that both TRP-2 and p15E reactive CTL could be detected in the spleens of naive animals after a single in vitro stimulation using 10(-5)-10(-6) M of the appropriate Kb-binding 9-amino acid epitope. In this report we show that the CTL found in naive animals are low avidity lymphocytes, that respond only to high concentrations of peptide in vitro. We demonstrate that titration of in vitro-stimulating peptide to limiting concentrations distinguishes qualitative differences in the lymphocyte reactivity to these two Ags between vaccinated and unvaccinated animals. We further demonstrate that in vitro expansion of CTL in either high or low concentrations of stimulating peptide generated CTL cultures with different avidities for the relevant epitopes. CTL expanded in low concentrations demonstrated higher avidity for peptide-pulsed targets and better tumor recognition, when compared to CTL generated in the presence of high concentrations of Ag. More importantly, high avidity CTL demonstrated superior in vivo antitumor activity. These results demonstrate that qualitative differences in the CTL that recognize these two self-Ags are critically important to their in vitro and in vivo anti-tumor efficacy. 相似文献
127.
Studied the role of affect as a mediator of the overjustification effect and proposed that negative affect has a critical detrimental influence on intrinsic motivation, either as a reaction derived from self-perception and evaluation processes or as a factor that acts independently of these cognitive activities. Two studies, with 180 undergraduates, used the typical overjustification paradigm to test these hypotheses. In Exp I, the overjustification effect was successfully replicated for both behavioral and self-report measures of intrinsic motivation. It is important that the negative affect paralleled these results and was greatest in those conditions in which intrinsic motivation was predicted and found to be low (e.g., expected reward). In Exp II, affect was directly manipulated, independently of the cognitive manipulations. Results show that the induced positive affect erased the decrease in intrinsic motivation that was observed in Exp I. It is suggested that what determines the decrease in intrinsic interest in any activity is, in part, the amount of negative affect that becomes associated with the activity. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
128.
All systems currently used for routine hemodialysis require heparin administration to prevent blood clotting in the extracorporeal circuit. We tested the hypothesis that population-based statistical techniques can be used to predict heparin concentrations during routine hemodialysis. Two predictive models were developed, one based on nonlinear mixed effects modeling (NONMEM) and the other on a multilayer perceptron neural network. Serial clotting time data were obtained from forty-nine patients and used to develop the models. The models were used to predict the clotting times of 70 patients in a prospective test. We determined that the neural network provided greater precision, had fewer outliers in its predictions, and did not have the model misspecification in bolus administration that the NONMEM predictions demonstrated. A final NONMEM model was developed using all data from 119 patients to identify important covariates for predicting the heparin pharmacodynamic parameters, volume of distribution, and clearance. Both the volume of distribution and clearance increased following the initiation of dialysis and as the patient's baseline clotting time increased. The volume of distribution also increased as the patient's weight increased but was decreased by smoking and diabetes. Population-based statistical techniques may provide a useful alternative to existing methods for prescribing heparin. 相似文献
129.
130.