全文获取类型
收费全文 | 1873篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 101篇 |
金属工艺 | 28篇 |
机械仪表 | 40篇 |
建筑科学 | 5篇 |
能源动力 | 28篇 |
轻工业 | 29篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 45篇 |
一般工业技术 | 175篇 |
冶金工业 | 1325篇 |
原子能技术 | 25篇 |
自动化技术 | 83篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 18篇 |
2014年 | 15篇 |
2013年 | 58篇 |
2012年 | 24篇 |
2011年 | 22篇 |
2010年 | 37篇 |
2009年 | 34篇 |
2008年 | 30篇 |
2007年 | 23篇 |
2006年 | 25篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 50篇 |
1998年 | 390篇 |
1997年 | 251篇 |
1996年 | 149篇 |
1995年 | 105篇 |
1994年 | 64篇 |
1993年 | 82篇 |
1992年 | 13篇 |
1991年 | 31篇 |
1990年 | 18篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 29篇 |
1986年 | 25篇 |
1985年 | 32篇 |
1984年 | 12篇 |
1983年 | 17篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1978年 | 9篇 |
1977年 | 35篇 |
1976年 | 55篇 |
1975年 | 10篇 |
1973年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有1895条查询结果,搜索用时 919 毫秒
81.
82.
Transition Metal Oxides: Electron‐Beam‐Induced Perovskite–Brownmillerite–Perovskite Structural Phase Transitions in Epitaxial La2/3Sr1/3MnO3 Films (Adv. Mater. 18/2014)
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
83.
The prediction model has been developed for steel weld metal microstructural constituents as a function of flux ingredients such as CaO, MgO, CaF2 and Al2O3 in submerged arc welding carried out at fixed welding parameters. The results of quantitative measurements of micro‐structural constituents on eighteen weld metal samples were utilised for developing the prediction equations of microstructural constituents applying statistical design of experiment for mixtures. Among the flux ingredients, CaO appears to be most important as an individual as well as interaction with other ingredients viz. CaF2 and Al2O3 in influencing the amount of microstructural constituents in weld metal. The prediction equations have been checked for adequacy by performing tests on welding using randomly designed flux and found satisfactory. The iso‐response curves were developed for selected microstructural constituents to show their output levels at different percentage of flux ingredients. 相似文献
84.
DK Jones D Lythgoe MA Horsfield A Simmons SC Williams HS Markus 《Canadian Metallurgical Quarterly》1999,30(2):393-397
BACKGROUND AND PURPOSE: Information on the neuropathological changes underlying ischemic leukoaraiosis is only available postmortem, and there are limited data on histological appearances early in the disease. Diffusion tensor imaging allows determination of the directionality of diffusion, which is greater in the direction of white matter bundles. Therefore, the technique might be expected to show loss of anisotropy (directional diffusion) in leukoaraiosis. METHODS: Nine patients with ischemic leukoaraiosis (radiological leukoaraiosis and clinical lacunar stroke) and 10 age-matched controls were studied. Diffusion tensor imaging was performed, and maps of diffusion trace and fractional anisotropy were constructed. Mean values of trace and fractional anisotropy were determined in standard regions of the anterior and posterior white matter in both hemispheres. RESULTS: In all patients with ischemic leukoaraiosis, a characteristic abnormal pattern was found, with loss of anisotropy and increased trace in the white matter. For example, in the right anterior white matter mean (SD) trace/3 was 1.12 (0.33) x10(-3) mm2 s-1 in patients and 0.75 (0.11) in controls (P=0.001). In the same region, fractional anisotropy was 0.53 (0.11) in patients and 0.78 (0.09) in controls (P<0.001). Within the white matter regions, there was a strong negative correlation between mean diffusivity and anisotropy (r=-0.92, P<0.0001). CONCLUSIONS: The characteristic pattern found on diffusion tensor imaging in this patient group is consistent with axonal loss and gliosis leading to impairment to and loss of directional diffusion. The "in vivo histological" information obtained may be useful in monitoring disease progression and in investigating the pathogenesis of the cognitive impairment that may be present. 相似文献
85.
Administration (p.o.) of SKP-450, 2-[2"-(1",3"-dioxolane)]-2-methyl-4-(2'-oxo-1'-pyrrolidinyl)-6-nitro-2H- 1-benzopyran, a novel antihypertensive agent, to hypercholesterolemic Syrian hamsters led to a significant reduction in plasma lipids in a dose-dependent manner, i.e., a 10.8% to 29% reduction in low-density lipoprotein cholesterol at doses of 0.3 to 10 mg/kg of SKP-450. SKP-450 was found to specifically inhibit the hepatic microsomal lanosterol 14alpha-methyl demethylase (14alpha-DM) in a competitive manner (Ki:2.65 microM). Furthermore, a dose-dependent decrease in the 14alpha-DM activity by SKP-450 parallelled the cholesterol synthetic rate in vitro in both the rat hepatic S10 fractions (supernatants at 10,000 g; IC50:20 microM) and Chinese hamster ovary cells (IC50:23 microM). However, this phenomenon was not seen in AR45 cells, which are deficient in 14alpha-DM, suggesting that 14alpha-DM is the major target for the inhibitory action of SKP-450 in regard to cholesterol biosynthesis. 相似文献
86.
Electroless nickel plating process has been studied considering pure copper (99.99%) as a substrate material. Deposition per unit area has been considered as a response variable and individual as well as combined effects of process parameters on deposited mass have been studied. Regression analysis and Student’s t test have been used to identify the significant influencing process parameters. It has been observed that reducing agent (NaBH4), source of metal (NiCl2 · 6H2O) and temperature significantly affect the deposition. The interactions among various process parameters have also been observed to be significant. Mathematical modeling has been carried out by a second-order response surface model with central composite design (CCD) to take into account the effect of curvature in the predicted response. Equations for response surfaces have been determined for various deposition times using MATLAB software package. Most of the response surfaces show that deposition thickness increases with increased values of process parameters within the adopted range but with different rates. The test for reliability for predicting response surface equations shows that these equations give an excellent fitting to the observed values. 相似文献
87.
The effects of methylprednisolone therapy on the susceptibility of dystrophin-deficient myofibers to contraction-induced injury were evaluated in the mdx mouse diaphragm model of Duchenne dystrophy. Mdx myofibers were abnormally vulnerable to injury induced by high-stress eccentric contractions. However, methylprednisolone therapy did not significantly alter the degree of contraction-induced injury. These data suggest that beneficial effects of corticosteroid therapy in Duchenne dystrophy are unlikely to be related to a change in the threshold for contraction-induced myofiber damage. 相似文献
88.
BACKGROUND: The sensitivity of diagnostic imaging of processes in the parotid gland has been increased by improved spatial resolution, yet specificity remains unchanged. The purpose of this study was to determine whether the low-flow color duplex technique alters the specificity of B-mode ultrasonography. PATIENTS AND METHODS: Forty-one patients with tumors of the parotid gland were examined by color duplex echography as well as histologically. Twenty-eight of the 41 patients had benign tumors and 13 had malignant disease. In 17 of 41 patients, color duplex ultrasonography failed to detect any vascularization within the tumor. Histopathological examination showed that 3 of these 17 tumors were malignant and 14 of 17 were benign. Intranodal vascularization was detected in 24 cases. Ten of these patients were found to have malignant tumors of the parotid gland; 14 had benign parotid tumors. RESULTS: Our present findings show that marked intratumoral vascularization especially appears in malignant tumors. In contrast to lymph nodes, the location and texture of intranodal blood vessels do not provide information about the nature of the neoplasm. CONCLUSIONS: Low flow duplex ultrasonography does not increase the specificity of preoperative examination in tumors of the parotid gland. 相似文献
89.
90.
A Rijhsinghani J Yankowitz AB Kanis GM Mueller DK Yankowitz RA Williamson 《Canadian Metallurgical Quarterly》1998,12(2):103-106
OBJECTIVE: This study assessed the clinical performance of dentin-bonded crowns, in which ceramic crowns are bonded to underlying dentin with a resin composite-based luting material and a dentin bonding agent. METHOD AND MATERIALS: Twenty-five patients who had received such restorations more than 1 year previously were recalled for evaluation of their crowns. RESULTS: Sixty dentin-bonded complete-coverage restorations were assessed. Forty-one of the crowns had been placed on incisor teeth. The mean time since placement of the restorations was 2.43 years. Fifty-seven of the 60 restorations were intact. The three failures had resulted from cracks in the restorations, which had not clinically debonded. No secondary caries was detected at the crown margins, and anatomic form was assessed as excellent for 56 crowns. Root canal treatment had been required in one case. Color match was rated very good for 47 crowns. All 25 patients were satisfied with their restorations. CONCLUSION: Dentin-bonded crowns may be found to have a low rate of failure and to provide a high level of patient satisfaction. 相似文献