全文获取类型
收费全文 | 406篇 |
免费 | 41篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 101篇 |
金属工艺 | 10篇 |
机械仪表 | 10篇 |
建筑科学 | 11篇 |
能源动力 | 17篇 |
轻工业 | 91篇 |
水利工程 | 5篇 |
无线电 | 23篇 |
一般工业技术 | 45篇 |
冶金工业 | 56篇 |
原子能技术 | 6篇 |
自动化技术 | 67篇 |
出版年
2023年 | 2篇 |
2022年 | 15篇 |
2021年 | 17篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 18篇 |
2012年 | 20篇 |
2011年 | 38篇 |
2010年 | 15篇 |
2009年 | 18篇 |
2008年 | 17篇 |
2007年 | 16篇 |
2006年 | 16篇 |
2005年 | 7篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 10篇 |
1998年 | 22篇 |
1997年 | 12篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有447条查询结果,搜索用时 15 毫秒
81.
K. G. Fertitta A. L. Holmes F. J. Ciuba R. D. Dupuis F. A. Ponce 《Journal of Electronic Materials》1995,24(4):257-261
In this paper, we describe the growth and characterization of high-quality GaN heteroepitaxial films grown on basal-plane sapphire substrates using metalorganic chemical vapor deposition. The quality of these films is analyzed by a variety of methods, including high-resolution x-ray diffraction, optical transmission spectroscopy, transmission electron microscopy (TEM), room temperature photoluminescence, and room-temperature Hall measurements. The x-ray diffraction full width at half maximum value of ΔΘ ~37 arc s is the narrowest reported to date for any III-V nitride film on any substrate. The x-ray rocking curves for ~0.48 μm thick GaN/Al2O3 heteroepitaxial layers exhibit Pendellösung fringes, indicating that even relatively thin films can be of high quality. High-resolution TEM lattice images further attest to the excellent structural quality, showing the films to be completely free of stacking faults. Furthermore, no evidence of columnar growth is observed. 相似文献
82.
R Tal-Singer C Peng M Ponce De Leon WR Abrams BW Banfield F Tufaro GH Cohen RJ Eisenberg 《Canadian Metallurgical Quarterly》1995,69(7):4471-4483
The entry of herpes simplex virus (HSV) into mammalian cells is a multistep process beginning with an attachment step involving glycoproteins gC and gB. A second step requires the interaction of glycoprotein gD with a cell surface molecule. We explored the interaction between gC and the cell surface by using purified proteins in the absence of detergent. Truncated forms of gC and gD, gC1(457t), gC2(426t), and gD1(306t), lacking the transmembrane and carboxyl regions were expressed in the baculovirus system. We studied the ability of these proteins to bind to mammalian cells, to bind to immobilized heparin, to block HSV type 1 (HSV-1) attachment to cells, and to inhibit plaque formation by HSV-1. Each of these gC proteins bound to conformation-dependent monoclonal antibodies and to human complement component C3b, indicating that they maintained the same conformation of gC proteins expressed in mammalian cells. Biotinylated gC1(457t) and gC2(426t) each bind to several cell lines. Binding was inhibited by an excess of unlabeled gC but not by gD, indicating specificity. The attachment of gC to cells involves primarily heparan sulfate proteoglycans, since heparitinase treatment of cells reduced gC binding by 50% but had no effect on gD binding. Moreover, binding of gC to two heparan sulfate-deficient L-cell lines, gro2C and sog9, both of which are mostly resistant to HSV infection, was markedly reduced. Purified gD1 (306t), however, bound equally well to the two mutant cell lines. In contrast, saturating amounts of gC1(457t) interfered with HSV-1 attachment to cells but failed to block plaque formation, suggesting a role for gC in attachment but not penetration. A mutant form of gC lacking residues 33 to 123, gC1(delta 33-123t), expressed in the baculovirus system, bound significantly less well to cells than did gC1(457t) and competed poorly with biotinylated gC1(457t) for binding. These results suggest that residues 33 to 123 are important for gC attachment to cells. In contrast, both the mutant and wild-type forms of gC bound to immobilized heparin, indicating that binding of these proteins to the cell surface involves more than a simple interaction with heparin. To determine that the contribution of the N-terminal region of gC is important for HSV attachment, we compared several properties of a mutant HSV-1 which contains gC lacking amino acids 33 to 123 to those of its parental virus, which contains full-length gC. The mutant bound less well to cells than the parental virus but exhibited normal growth properties.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
83.
84.
85.
Maríaa del R. Moreira Alejandra G. Ponce Carlos E. Del Valle Sara I. Roura 《Journal of food science》2006,71(2):S188-S192
Heat shocks not only produced a reduction in the initial content of ascorbic acid but also affected the rate of degradation of ascorbic acid during refrigerated storage. Samples treated at higher temperatures presented faster rates of degradation. The heat shocks produced an initial reduction in the counts of mesophilic aerobic microorganisms, with greater reductions associated with the higher shock temperatures. However, high shock temperatures promoted faster microbial growths during storage, probably due to the liberation of nutrients by the disruption of membrane barriers. The sensory attributes of lettuce leaves subjected to heat shocks presented mixed results. Thermal treatments affected the enzymatic activity, reducing browning phenomena, but also caused deleterious effects on surface color and texture of lettuce leaves. Heat shocks of 50°C could be useful for short‐term preservation of minimally processed lettuce, where the high rate of metabolic processes cause great deterioration of fresh products. 相似文献
86.
Atkinson Donald R.; Ponce Francisco Q.; Martinez Francine M. 《Canadian Metallurgical Quarterly》1984,31(4):588
Surveyed 63 male and 64 female Mexican-American community college students to determine their attitude toward acculturation. Ss were then randomly assigned to receive written material describing the sex, ethnicity, and attitude toward acculturation of a counselor they subsequently heard in a tape-recorded excerpt of a counseling session. After reading the written introduction and listening to the counseling excerpt, Ss rated the counselor's credibility and attractiveness on the Counselor-Effectiveness Rating Scale (CERS). A repeated measures ANOVA revealed a significant interaction between attitude similarity and the repeated factor (CERS subscales). Post hoc analyses indicated that Ss' ratings of their willingness to see the counselor were significantly lower than other credibility ratings for those Ss who were exposed to a counselor with a dissimilar attitude. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Sylvain Petitjean Jean Ponce David J. Kriegman 《International Journal of Computer Vision》1992,9(3):231-255
This article presents an algorithm for computing the exact aspect graph of an opaque solid bounded by a smooth algebraic surface. Orthographic projection is assumed. The algorithm is based on a catalog of visual events available from singularity theory. It uses curve tracing, cell decomposition, homotopy continuation, and ray tracing to construct the regions of the view sphere delineated by visual-event curves. The algorithm has been fully implemented, and examples are presented. 相似文献
88.
S Siles V Garrigues J Ponce C Gálvez J Berenguer 《Canadian Metallurgical Quarterly》1997,89(6):445-456
OBJECTIVE: To develop guidelines for predicting colonic disease on the basis of clinical parameters. EXPERIMENTAL DESIGN: A prospective study of the clinical data prior to colonoscopy. On the basis of the endoscopic findings, the patients were divided into three diagnostic groups: absence of significant disease, significant benign disease and malignant disease. The patient population was divided randomly into two subgroups. The clinical data from one of them was used to build a database which, using Bayes' theorem, was compared with the variables from the other subgroup to predict the diagnosis for each patient. PATIENTS: A total of 336 patients (170 males and 166 females; mean age: 58 years; range: 15 to 87 years) were evaluated. RESULTS: When the endoscopic findings were grouped on the basis of their clinical importance, 211 patients (63%) belonged to the group without significant disease, 60 patients (18%) had significant benign disease and 65 (19%) presented a neoplastic disease. Of the 21 variables selected for use in the database, 6 showed statistically significant differences in terms of the absence or presence of malignant disease: age, absence of previous similar episodes, weight loss, rectal bleeding, lack of improvement and the presence of a mass on digital rectal examination. The predictive model differentiated patients with neoplasm from those without malignant disease, but was not capable of identifying differences among the latter. The model was useful for assessing the risk of malignant disease for each patient. CONCLUSIONS: The predictive model obtained is a useful tool for establishing the diagnosis and the priority in the performance of colonoscopy. 相似文献
89.
María S. Giménez Ana M. Ponce de Ascheri María E. Elorza de Orellano Liliana Oliveros Fanny Zirulnik de Hodara Mirta R. Bonomi Luis A. Giménez 《Lipids》1989,24(11):985-987
Male goats (“Criolla Argentina” breed), castrated at 45 days of age, showed altered lipid metabolism 180 days after castration
as compared to control goats. Subcutaneous, perirenal and omental adipose tissues of castrated goats showed increases in fatty
acid synthetase, glucose-6-phosphate dehydrogenase and NADP-isocitrate dehydrogenase activities. Castration increased the
amount of total lipids and triglycerides, but did not modify the amount of cholesterol, phospholipid and protein in the three
types of adipose tissue. The incorporation of [1-14C]acetate into fatty acids of subcutaneous and perirenal adipose tissue was increased in castrated goats in relation to noncastrated
goats. Our results suggest that removal of gonadal steroids increases significantly the rate of lipogenesis in adipose tissue
of male goats. 相似文献
90.
P Nos V Garrigues E Caballero MC Cano R Sopena J Ponce 《Canadian Metallurgical Quarterly》1998,21(8):386-390
The evaluation of gastric emptying by the double isotope technique involves some methodologic conditioning. Among them contamination correction or interference in the energy windows of the activity of the two isotopes used in the marking of the solids and fluids of the test food are important. The results of an experiment in which a phantom was used to evaluate the contamination between indio 111 (DTPA-Ca111In) and technecium 99m (colloid99mTc). Three test studies were posteriorly performed in healthy volunteers and 27 studies in a control group (13 males, mean age of 33 years, mean body mass index 39.02 kg/m). In these studies the contamination was corrected with the acquisition, following an initial swallow of juice marked with 111In, of activity in the windows of both isotopes. The contamination of 111In (isotope of greatest radiation energy) in the window of 99mTc was 24% in the phantom and 20%, 23% and 26% in the three initial study tests. The mean contamination in the control group was of 22% with limits of 19% to 29% and a standard deviation of 3%. Despite the comparable results, the usefulness of the individualized contamination calculation in the studies of gastric emptying with dual isotope to minimize the methodologic errors of this technique is discussed. 相似文献