全文获取类型
收费全文 | 10168篇 |
免费 | 154篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 89篇 |
综合类 | 6篇 |
化学工业 | 1223篇 |
金属工艺 | 163篇 |
机械仪表 | 230篇 |
建筑科学 | 283篇 |
矿业工程 | 55篇 |
能源动力 | 164篇 |
轻工业 | 696篇 |
水利工程 | 69篇 |
石油天然气 | 23篇 |
武器工业 | 1篇 |
无线电 | 748篇 |
一般工业技术 | 1340篇 |
冶金工业 | 4392篇 |
原子能技术 | 81篇 |
自动化技术 | 771篇 |
出版年
2022年 | 49篇 |
2021年 | 56篇 |
2020年 | 40篇 |
2019年 | 55篇 |
2018年 | 78篇 |
2017年 | 72篇 |
2016年 | 84篇 |
2015年 | 78篇 |
2014年 | 101篇 |
2013年 | 354篇 |
2012年 | 193篇 |
2011年 | 252篇 |
2010年 | 254篇 |
2009年 | 238篇 |
2008年 | 256篇 |
2007年 | 254篇 |
2006年 | 214篇 |
2005年 | 238篇 |
2004年 | 176篇 |
2003年 | 196篇 |
2002年 | 189篇 |
2001年 | 158篇 |
2000年 | 175篇 |
1999年 | 205篇 |
1998年 | 1267篇 |
1997年 | 832篇 |
1996年 | 554篇 |
1995年 | 402篇 |
1994年 | 329篇 |
1993年 | 346篇 |
1992年 | 136篇 |
1991年 | 128篇 |
1990年 | 140篇 |
1989年 | 135篇 |
1988年 | 134篇 |
1987年 | 109篇 |
1986年 | 102篇 |
1985年 | 120篇 |
1984年 | 113篇 |
1983年 | 88篇 |
1982年 | 81篇 |
1981年 | 84篇 |
1980年 | 95篇 |
1979年 | 81篇 |
1978年 | 93篇 |
1977年 | 174篇 |
1976年 | 310篇 |
1975年 | 60篇 |
1974年 | 63篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
CE Korcarz PA Padrid SG Shroff L Weinert RM Lang 《Canadian Metallurgical Quarterly》1997,26(6):287-298
Cardiac ultrasound is a noninvasive technique that is commonly used to serially evaluate cardiac structure and function. Recent advances in Doppler-Echocardiography enable the ultrasonographer to perform a sophisticated noninvasive assessment of cardiovascular physiology. The Rhesus monkey is a frequently used non-human primate animal model of human cardiovascular disease because this species closely models human anatomy and physiology. However, while this species is frequently used in cardiovascular research, standardized echocardiographic values generated from large numbers of normal Rhesus are not available. In the present study, we performed cardiac ultrasound imaging on 28 healthy Rhesus monkeys to obtain normal reference values of cardiovascular structure and function in this species. Nomograms were generated from these data by plotting parameters of cardiovascular geometry and function with body weight. These normal reference data were compared to previously reported values obtained from prior studies that used noninvasive, invasive, and morphometric techniques. 相似文献
942.
HE Jones CL Eaton D Barrow CM Dutkowski JM Gee K Griffiths 《Canadian Metallurgical Quarterly》1997,30(4):219-231
Murine acute myeloid leukemia is characterized by chromosome 2 aberrations, and genesis of the marker chromosome 2 by radiation is suspected to be an initiating event of radiation leukemogenesis. A detailed analysis of the type and frequency of chromosome 2 aberrations in murine bone marrow cells at an early stage after irradiation is provided here. A total of 40 male C3H/He mice was exposed to 137Cs gamma-ray at a dose of 1, 2 or 3 Gy, and sacrificed 24 hours after irradiation. Metaphase samples prepared from bone marrow cells were Q-banded for karyotyping or painted with DNA probes specific to chromosome 2. In 5 mice analyzed by karyotyping, one mouse showed high frequency of the marker aberrations as well as other chromosome 2 aberrations. Chromosome painting analysis for the rest of the mice also detected 3 animals showing significantly high frequencies of chromosome 2 aberrations. Dose-dependence of the frequencies was observed even among those mice that tended to be sensitive. The results indicated that there was a subgroup of mice carrying hypersensitive chromosome 2. The subgroup could be leukemia-sensitive if radiation-induced chromosome aberrations are responsible for an early change in myeloid leukemogenesis. 相似文献
943.
944.
S Fong S Jones ME Renz HH Chiu AM Ryan LG Presta D Jackson 《Canadian Metallurgical Quarterly》1997,16(3):299-311
The integrin alpha 4 beta 7 and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) are molecules involved in the normal recirculation of lymphocytes between the blood and the gastrointestinal tract. These molecules may play a complementary and significant role in animal models of colitis. We have investigated the structural interaction between alpha 4 beta 7 and MAdCAM-1. Site-directed mutagenesis studies of the MAdCAM-1 molecule has led to the identification of the amino acid residue (LDT) in the loop between beta strands C and D of the Ig-superfamily-like folds being involved in the adhesive and cell activation functions of MAdCAM-1 with alpha 4 beta 7. 相似文献
945.
946.
CH Jones CG Newstead EJ Will SW Smye AM Davison 《Canadian Metallurgical Quarterly》1997,12(7):1406-1413
INTRODUCTION: In CAPD patients serum albumin is frequently used as an index of nutritional status, although it is recognized that hypoalbuminaemia may be caused by many factors. We have further examined the relationship between serum albumin and nutrition. METHODS: Nutritional status was assessed by biochemistry, anthropometry, mid-arm muscle circumference, muscle strength (hand grip and back), and lean body mass (from anthropometry, creatinine kinetics and bioimpedance) in a group of 76 stable CAPD patients. Correlations between biochemical and nutritional parameters were sought and data were compared between patient groups defined by serum albumin (> or = 37 vs < 37 g/l on two occasions 2 months apart) and separately according to subjective global assessment score (normal nutrition, A vs mild to moderate, B, and severe, C, malnutrition). RESULTS: In patients with a low SGA score, actual body weight, body mass index, mid-arm muscle circumference, lean body mass, subscapular skinfold thickness, hand grip strength (males and females) and iliac and triceps skinfold thicknesses and back strength (females only) were all significantly less than in patients with a normal SGA score. In contrast, none of these variables differed in either gender when patients were compared according to serum albumin. Serum albumin was correlated with serum creatinine (r = 0.45, P = 0.01), daily urine protein excretion (r = -0.42, P = 0.02) and uncorrected weekly creatinine clearance (r = -0.39) in females, but not with any index of body composition in either gender. CONCLUSION: Whilst SGA identified a patient group with significantly abnormal body mass, muscle mass and muscle strength, serum albumin did not. Serum albumin is not a useful marker of malnutrition in stable patients on CAPD. 相似文献
947.
Robert Jones 《Granular Matter》2003,4(4):191-204
The atomic force microscope (AFM) has been used to study inter-particle contacts in air for a range of model particles and cohesive granular materials of commercial importance. Adhesion (or pull-off force), friction and its load dependence, and particle size, morphology and roughness were measured for glass ballotini, fumed silica, alumina, limestone, titania and zeolite. Particle-wall contacts and effects of relative humidity were also studied. Most of the results, after allowing for roughness, are consistent with JKR contact mechanics and capillary bridge theory; however, the main object of the present work is to demonstrate semi-quantitative links between the AFM measurements and related bulk flow and cohesion measurements performed in parallel on the same materials. A simple model of a particle assembly will be used to compare average contact forces in typical single-particle AFM experiments and typical bulk experiments, and thus identify those regimes of powder flow where the two approaches overlap, and AFM measurements may be used with some confidence in more sophisticated modeling based on distinct element analysis (DEA). Four areas will be discussed briefly: (1) The apparent analogy between bulk yield loci and single-particle friction-load data; (2) Cohesion data and particle size effects; (3) Bulk tensile strength and single particle pull-off force; (4) Bulk wall friction and single-particle-wall friction. It is found that typical single-particle AFM experiments and bulk shear experiments converge for small particles (~ 4 μm) and low consolidation stress, when the average inter-particle contact forces are of the order 20–100nN, involve single or few asperities, and are not much larger than pull-off forces. For large particles and high consolidation loads the data do not overlap and AFM measurements may be less useful as input to simulations where sliding friction is less important, and where large normal contact forces dominate over tangential forces and are responsible for the shear strength. 相似文献
948.
P. E. Krajewski J. W. Jones J. E. Allison 《Metallurgical and Materials Transactions A》1995,26(12):3107-3118
The effect of TiC particle reinforcement on the creep behavior of Al (99.8) and Al-1.5Mg is investigated in the temperature
range of 150 °C to 250 °C. The dislocation structure developed during creep is characterized in these materials. The addition
of TiC increases creep resistance in both alloys. In pure aluminum, the presence of 15 vol pct TiC leads to a factor of 400
to 40,000 increase in creep resistance. The creep strengthening observed in Al/TiC/15p is substantially greater than the direct strengthening predicted by continuum models. Traditional methods for explaining
creep strengthening in particle-reinforced materials(e.g., threshold stress, constant structure, and dislocation density) are unable to account for the increase in creep resistance.
The creep hardening rate(h) is found to be 100 times higher in Al/TiC/15p, than in unreinforced Al. When incorporated into a recovery creep model, this increase inh can explain the reduction in creep rate in Al/TiC/15p. Particle reinforcement affects creep hardening, and thus creep rate, by altering the equilibrium dislocation substructure
that forms during steady-state creep. The nonequilibrium structure generates internal stresses which lower the rate of dislocation
glide. The strengthening observed by adding TiC to Al-1.5Mg is much smaller than that found in the pure aluminum materials
and is consistent with the amount of strengthening predicted by continuum models. These results show that while both direct
(continuum) and indirect strengthening occur in particle-reinforced aluminum alloys, the ratio of indirect to direct strengthening
is strongly influenced by the operative matrix strengthening mechanisms.
This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the
1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint
TMS-SMD/ASM-MSD Composite Materials Committee. 相似文献
949.
950.
A new shape representation-the radial intersection set (RIS)-is presented. The RIS is an object-centred model in which 2-D and 3-D boundaries are represented via their intersection with radial lines from some specific origin. The RIS representation allows efficient 3-D reconstruction using silhouette intersection from an arbitrary number of 2-D perspective views. The relationship between the visual hull (Laurentini, 1994) of the 3-D object and the silhouettes it may generate is defined as a set intersection operator. This operator allows the direct generation of 3-D RIS models from silhouettes. The RIS method is shown to compare favourably, in terms of both speed and storage, with existing octree techniques. Examples of images rendered from RIS models are presented. These show high visual fidelity 相似文献