全文获取类型
收费全文 | 1275篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 73篇 |
综合类 | 5篇 |
化学工业 | 195篇 |
金属工艺 | 50篇 |
机械仪表 | 23篇 |
建筑科学 | 35篇 |
能源动力 | 41篇 |
轻工业 | 56篇 |
水利工程 | 26篇 |
无线电 | 148篇 |
一般工业技术 | 149篇 |
冶金工业 | 391篇 |
原子能技术 | 22篇 |
自动化技术 | 72篇 |
出版年
2024年 | 8篇 |
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 20篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 19篇 |
2014年 | 13篇 |
2013年 | 36篇 |
2012年 | 33篇 |
2011年 | 51篇 |
2010年 | 20篇 |
2009年 | 56篇 |
2008年 | 43篇 |
2007年 | 29篇 |
2006年 | 35篇 |
2005年 | 42篇 |
2004年 | 37篇 |
2003年 | 37篇 |
2002年 | 21篇 |
2001年 | 36篇 |
2000年 | 30篇 |
1999年 | 25篇 |
1998年 | 125篇 |
1997年 | 99篇 |
1996年 | 50篇 |
1995年 | 40篇 |
1994年 | 29篇 |
1993年 | 30篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 7篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 21篇 |
1973年 | 5篇 |
1972年 | 10篇 |
排序方式: 共有1286条查询结果,搜索用时 0 毫秒
51.
Optimum design of a grazing-incidence flat-field spectrograph with a spherical varied-line-space grating 总被引:1,自引:0,他引:1
A grazing-incidence spectrograph is designed by use of the flat-field image-focusing property of a spherical varied-line-space grating. Optimum grating parameters for mechanical ruling are selected by application of genetic algorithms. Two gratings, one for 2-5-nm and the other for 5-20-nm spectral regions, are designed, and their fabrication tolerances are analyzed. 相似文献
52.
Current switching in power control devices sometimes has serious noise difficulties. This paper presents a method of testing and measuring noise immunity. The noise immunity of a thyristor with magnetic core or unijunction transistor is analyzed and measured. The experiment agrees well with the theory. 相似文献
53.
Tsubota T Taki S Nakayama K Mason JI Kominami S Harada N Kita I 《Reproduction (Cambridge, England)》2001,121(4):587-594
The Japanese black bear, Ursus thibetanus japonicus, is a seasonal breeder and shows delayed implantation for several months during pregnancy. The objective of this study was to clarify the steroidogenic capability of the corpus luteum and placenta during pregnancy, including both delayed implantation and fetal development, by immunolocalization of steroidogenic enzymes in these organs of the Japanese black bear. Ovaries and placentae from 15 wild Japanese black bears, which had been killed legally by hunters and were thought to be pregnant, were used in an immunocytochemical study to localize the cholesterol side chain cleavage cytochrome P450 (P450scc), 3beta-hydroxysteroid dehydrogenase (3betaHSD), 17alpha-hydroxylase cytochrome P450 (P450c17) and aromatase cytochrome P450 (P450arom) by the avidin-biotin-peroxidase complex method using polyclonal antisera raised in mammals against P450scc, 3betaHSD, P450c17 and P450arom. P450scc and 3betaHSD were localized in all luteal cells throughout pregnancy. P450c17 was present in a few luteal cells, especially in the outer area of the corpus luteum throughout pregnancy, but the number of positively immunostained cells decreased during the post-implantation period. Cells positively immunostained for P450c17 were significantly smaller than negatively immunostained cells (P < 0.01). P450arom was present sporadically in a few luteal cells throughout pregnancy, but the number of positively immunostained cells decreased during the post-implantation period. The size of cells positively immunostained for P450arom was not significantly different from that of negatively immunostained cells. The whole placenta was negatively immunostained for P450scc, 3betaHSD and P450c17, but P450arom was present in the syncytiotrophoblasts and endothelial cells of maternal blood vessels. These results indicate that, in the Japanese black bear, corpora lutea are a source of progesterone which may play an important role in the maintenance of delayed implantation and fetal development during pregnancy. Corpora lutea have a minimum capability to synthesize androgen in small luteal cells and oestrogen in normal-sized luteal cells during pregnancy, and placentae have the ability to synthesize oestrogen during late pregnancy. 相似文献
54.
Mitsukazu Ochi Daisuke Nii Yasufumi Suzuki Miyuki Harada 《Journal of Materials Science》2010,45(10):2655-2661
Epoxy/zirconia hybrid materials were synthesized from a bisphenol-A type epoxy resin, zirconium-tetra-n-propoxide and acetic acid via in situ polymerization. Acetic acid was used to control the hydrolysis and condensation reaction of the zirconium-tetra-n-propoxide. As a result, the zirconia produced by the in situ polymerization was uniformly dispersed into the epoxy matrix on a nano scale or less, and the hybrid materials exhibited an excellent optical transparency. With the increasing zirconia contents, the storage modulus in the rubbery region increased and the peak area of tanδ in the glass transition temperature region decreased. These results indicate that their heat resistance of the hybrid materials could be improved by hybridization with zirconia. Furthermore, the refractive indices of the hybrid materials were significantly improved with the increasing zirconia contents. 相似文献
55.
Takashi Yasuno Takuya Kamano Takayuki Suzuki Kazuo Uemura Hironobu Harada Yu Kataoka 《Electrical Engineering in Japan》2000,131(2):30-39
This paper introduces a human skill base control algorithm using artificial neural networks and fuzzy reasoning for an autonomous mobile robot. Neural networks are used to select a suitable motion control pattern in actual environments. The back propagation algorithm adjusts the weights of the neural networks so that the selected motion control pattern corresponds to the action, which is obtained by the operator's behavior decision skill. To realize the selected motion control pattern, the orientation angle and the speed of the mobile robot are determined by fuzzy reasoning in which fuzzy rules are also automatically tuned so as to simulate the operator's control skill. We have implemented and tested the proposed control algorithm on an autonomous mobile robot and some experimental results demonstrate the effectiveness of the proposed control algorithm for the autonomous mobile robot. © 2000 Scripta Technica, Electr Eng Jpn, 131(2): 30–39, 2000 相似文献
56.
Laboratory accumulation and excretion experiments of 4-nonylphenols (NP) and 4-tert-octylphenol (OP) were performed for killifish (Oryzias latipes). The bioconcentration factors (BCF, wet weight) in the whole fish were mean +/- SD of 167 +/- 23 (n = 4) for NP and 261 +/- 62 (n = 4) for OP. The biological half-lives in the whole fish were 9.9 h for NP and 7.7 h for OP. Parallel to the laboratory experiments, field survey on the chemicals contamination for water and ayu fish (Plecoglossus altivelis) from rivers flowing into Lake Biwa was performed. The contamination was not so high in agreement with the laboratory experimental data and the field BCF values (wet weight) in the ayu fish were 21 +/- 15 (n = 8) for NP and 297 +/- 194 (n = 3) for OP. 相似文献
57.
Y Katayama K Kojima T Yoshino Y Matsuo M Isokawa T Yano H Oka M Yamaguchi S Deguchi J Tsuchiyama K Hayashi T Teshima K Shinagawa F Ishimaru E Omoto M Harada 《Canadian Metallurgical Quarterly》1997,97(3):626-634
In two-thirds of patients with splenic lymphoma with villous lymphocytes (SLVL) a small amount of M-protein can be detected in association with the presence of plasma cells in the peripheral blood (PB) and/or bone marrow (BM). However, it is not known whether lymphoma cells and plasma cells originate from the same clone. In this report we describe a case of SLVL which was characterized by the presence of marked monoclonal gammopathy (IgG-kappa 90 g/l) and increased plasma cells in the BM. In an attempt to elucidate the origin of lymphoma cells and plasma cells, we performed morphological, cytogenetic and molecular studies on PB mononuclear cells (PBMNC) without plasma cells and BMMNC containing 10% plasma cells from this patient. Immunofluorescence showed that lymphoma cells and plasma cells were positive for cytoplasmic gamma heavy and kappa light chains. Well-developed endoplasmic reticulum was observed in the cytoplasmic organelles of PBMNC using an electron microscope. The mean IgG concentration in the 3 d supernatant cultures of PBMNC was 374 +/- 24 microg/l. More than 50% PBMNC differentiated into plasmacytoid cells in 6 d of liquid culture with IL-3 and IL-6. Analysis by two-colour FISH revealed that karyotypic abnormalities of monosomy X and trisomy 17 existed simultaneously in both lymphoma cells and plasma cells. JH gene rearranged bands from PBMNC and BMMNC by Southern blot hybridization were identical, whereas DNAs from PBMNC failed to hybridize with the Cmu probe. These observations strongly suggest that lymphoma cells and plasma cells originate from the same clone, and that plasma cells, as well as lymphoma cells, which have undergone class switch recombination, could produce IgG type M-protein in this case. 相似文献
58.
59.
CG Milross KA Mason NR Hunter NH Terry N Patel S Harada T Jibu J Seong L Milas 《Canadian Metallurgical Quarterly》1997,33(8):1299-1308
Functional assembly of the plasminogen-dependent proteolytic system on the cell surface requires multiple interactions involving urokinase (uPA), urokinase receptor (uPAR), plasminogen activator inhibitors, and other molecules that mediate cell migration and adhesion. We analyzed the in vitro interaction of uPAR-containing particulate cell fractions with the amino-terminal fragment (ATF) of human urokinase and the matrix-like form of vitronectin. Binding and cross-linking of 125I-labeled ATF to crude membrane extracts from LB6-19 mouse cells overexpressing human uPARs in the presence of 25 nM urea-denatured vitronectin led to the formation of Mr 137,000, 92, 000, and 82,000 covalent complexes. Immunoprecipitation of the preformed cross-linked 125I-labeled complexes with anti-vitronectin, anti-uPA, or anti-uPAR antibodies revealed that the Mr 82,000 and 92, 000 species do contain ATF and vitronectin and identified the Mr 137, 000 species as a ternary complex formed by ATF, uPAR, and vitronectin. A similar electrophoretic pattern was displayed by acid-pretreated membranes extracted from MCF-7 breast carcinoma or HT1080 fibrosarcoma cell lines, as well as a ductal breast carcinoma specimen; the latter exhibited complex formation at concentrations of vitronectin lower than 10 nM. Finally, uPAR-vitronectin interaction was further documented by the decreased reactivity of an anti-uPAR polyclonal antibody to acid-pretreated sections of 10 breast carcinomas that had been preincubated with vitronectin. Our findings highlight the ability of uPAR to interact simultaneously with vitronectin and uPA in breast cancer, supporting a dynamic coupling of the molecular mechanisms underlying plasminogen-dependent matrix degradation and cell adhesion. 相似文献
60.
AJ Comerota V Chouhan RN Harada L Sun J Hosking R Veermansunemi AJ Comerota D Schlappy AK Rao 《Canadian Metallurgical Quarterly》1997,226(3):306-13; discussion 313-4
BACKGROUND AND OBJECTIVES: Intermittent pneumatic compression (IPC) is an effective form of deep vein thrombosis prophylaxis for general surgery patients. The antithrombotic effect of IPC is thought to be the result of increased venous velocity and stimulation of endogenous fibrinolysis. However, the mechanism of enhanced fibrinolytic activity and the relative effects on normal and postthrombotic veins have not been defined. The purposes of this study are 1) to quantify changes in fibrinolytic activity with IPC; 2) to study the mechanism of fibrinolytic enhancement with IPC; and 3) to evaluate whether postthrombotic patients have the same capacity for fibrinolytic enhancement with IPC as do normal subjects. METHODS: Twelve volunteers (6 normal and 6 postthrombotic) had 5 IPC devices applied for 120 minutes in random fashion, 1 per week x 5 weeks. The devices included single-chamber, sequential, foot, calf, and long-leg compression. Subjects had an indwelling antecubital venous cannula placed for blood drawn at baseline, 60, 120, and 180 minutes after IPC devices were applied. Global fibrinolytic activity (euglobulin fraction, fibrin plate assay), tissue plasminogen activator (tPA) antigen (Ag) and activity (Act), plasminogen activator inhibitor-1 (PAI-1) Ag and Act, alpha-2-antiplasmin-plasmin complexes, and von Willebrand factor (vWF) antigen were assayed. RESULTS: A striking elevation in fibrinolytic activity was noted at 180 minutes with all devices in normal subjects and postthrombotic patients (p = 0.01-0.0001); however, baseline and stimulated fibrinolytic activity was attenuated in postthrombotic patients (<0.03). The tPA-Act increased only in normal subjects (3.8 +/- 1.9%) (p = 0.057), despite a decrease in plasma tPA-Ag, which was observed in both normal subjects (-12.4 +/- 3.8%) (p = 0.009) and patients (-17.2 +/- 3.1%) (p = 0.001). PAI-1-Ag decreased in both normal subjects (-13.4 +/- 3.8%) (p = 0.007) and patients (-12.0 +/- 3.1%) (p = 0.013) with a marked reduction in PAI-1-Act in both normal subjects (p = 0.003) and patients (p = 0.004). There were no changes in vWF, and alpha-2-antiplasmin-plasmin complexes increased only in postthrombotic patients (p = 0.021). CONCLUSIONS: Stimulation of endogenous fibrinolytic activity occurs after IPC, both in normal subjects and postthrombotic patients; however, baseline and overall fibrinolytic response in postthrombotic patients is reduced. The mechanism of increased fibrinolytic activity is likely because of a reduction in PAI-1, with a resulting increase of tPA activity. 相似文献