全文获取类型
收费全文 | 4071篇 |
免费 | 140篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 46篇 |
综合类 | 1篇 |
化学工业 | 597篇 |
金属工艺 | 41篇 |
机械仪表 | 67篇 |
建筑科学 | 194篇 |
矿业工程 | 7篇 |
能源动力 | 92篇 |
轻工业 | 279篇 |
水利工程 | 29篇 |
石油天然气 | 28篇 |
无线电 | 299篇 |
一般工业技术 | 627篇 |
冶金工业 | 1399篇 |
原子能技术 | 68篇 |
自动化技术 | 440篇 |
出版年
2021年 | 41篇 |
2020年 | 39篇 |
2019年 | 52篇 |
2018年 | 70篇 |
2017年 | 60篇 |
2016年 | 70篇 |
2015年 | 55篇 |
2014年 | 72篇 |
2013年 | 182篇 |
2012年 | 145篇 |
2011年 | 196篇 |
2010年 | 134篇 |
2009年 | 137篇 |
2008年 | 172篇 |
2007年 | 166篇 |
2006年 | 143篇 |
2005年 | 140篇 |
2004年 | 115篇 |
2003年 | 101篇 |
2002年 | 104篇 |
2001年 | 71篇 |
2000年 | 69篇 |
1999年 | 79篇 |
1998年 | 262篇 |
1997年 | 170篇 |
1996年 | 130篇 |
1995年 | 88篇 |
1994年 | 92篇 |
1993年 | 67篇 |
1992年 | 45篇 |
1991年 | 44篇 |
1990年 | 51篇 |
1989年 | 52篇 |
1988年 | 46篇 |
1987年 | 63篇 |
1986年 | 47篇 |
1985年 | 44篇 |
1984年 | 39篇 |
1983年 | 42篇 |
1982年 | 29篇 |
1981年 | 33篇 |
1980年 | 32篇 |
1979年 | 28篇 |
1978年 | 29篇 |
1977年 | 45篇 |
1976年 | 85篇 |
1975年 | 27篇 |
1974年 | 23篇 |
1973年 | 19篇 |
1972年 | 23篇 |
排序方式: 共有4214条查询结果,搜索用时 428 毫秒
41.
The Interpersonal Orientation Scale was developed to focus on four dimensions assumed to underlie affiliation motivation: social comparison, emotional support, positive stimulation, and attention. Factor analyses basically supported the proposed multidimensional construct. Evidence for the validity of the four dimensions was provided by their correlations with measures of constructs conceptually related to affiliation motivation and their lack of correlation with measures conceptually unrelated to affiliation motivation. Moreover, in a laboratory study, each motivational subscale tended to correlate most highly with role-played responses in a situation affording the relevant incentive type. Future research on social motivation and interaction will profit from identifying the particular incentives that are salient in a given setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
The activation of propane using zeolite H-Y and Ga3+ exchanged zeolite Y indicates that in the presence of Ga3+ the mechanism of propane activation is changed from a cracking pathway to a dehydrogenation pathway. The presence of both Ga3+ and H+ are required to achieve this effect. 相似文献
43.
A perturbation expansion technique for approximating the three dimensional anisotropic elastic Green's function is presented. The method employs the usual series for the matrix (I–A)-1 to obtain an expansion in which the zeroth order term is an isotropic fundamental solution. The higher order contributions are expressed as contour integrals of matrix products, and can be directly evaluated with a symbolic manipulation program. A convergence condition is established for cubic crystals, and it is shown that convergence is enhanced by employing Voigt averaged isotropic constants to define the expansion point. Example calculations demonstrate that, for moderately anisotropic materials, employing the first few terms in the series provides an accurate solution and a fast computational algorithm. However, for strongly anisotropic solids, this approach will most likely not be competitive with the Wilson-Cruse interpolation algorithm.This research was sponsored by the Exploratory Studies Program of Oak Ridge National Laboratory and the Division of Materials Science, U. S. Department of Energy, under contract DE-AC05-84OR21400 with Lockheed Martin Energy Systems, Inc. 相似文献
44.
Intrinsic Motivation Systems for Autonomous Mental Development 总被引:1,自引:0,他引:1
Oudeyer P.-Y. Kaplan F. Hafner V.V. 《Evolutionary Computation, IEEE Transactions on》2007,11(2):265-286
Exploratory activities seem to be intrinsically rewarding for children and crucial for their cognitive development. Can a machine be endowed with such an intrinsic motivation system? This is the question we study in this paper, presenting a number of computational systems that try to capture this drive towards novel or curious situations. After discussing related research coming from developmental psychology, neuroscience, developmental robotics, and active learning, this paper presents the mechanism of Intelligent Adaptive Curiosity, an intrinsic motivation system which pushes a robot towards situations in which it maximizes its learning progress. This drive makes the robot focus on situations which are neither too predictable nor too unpredictable, thus permitting autonomous mental development. The complexity of the robot's activities autonomously increases and complex developmental sequences self-organize without being constructed in a supervised manner. Two experiments are presented illustrating the stage-like organization emerging with this mechanism. In one of them, a physical robot is placed on a baby play mat with objects that it can learn to manipulate. Experimental results show that the robot first spends time in situations which are easy to learn, then shifts its attention progressively to situations of increasing difficulty, avoiding situations in which nothing can be learned. Finally, these various results are discussed in relation to more complex forms of behavioral organization and data coming from developmental psychology 相似文献
45.
Considering the critical contribution of your rectifier to the safe, effective, and reliable operation of your electrocoating process, the selection and maintenance of the optimum unit for your operation is time well spent. 相似文献
46.
Aragonite particles dispersed in a bioresorbable polymer matrix are considered to be a good candidate for bone prosthesis
materials. It is important to characterize the microstructure of synthetic aragonite used for biomedical applications, since
the microstructure may influence its integration, resorption and replacement by bone. We studied late stages of aragonite
growth, at an air–liquid interface, from a solution not doped with additives. Comparison was made between the types of synthetic
aragonite microstructure and that of aragonite which is found in nature (mollusc shells, gallstones, Earth's crust). The microstructure
of natural aragonite is unique to certain classes of living organisms and the understanding of its structure/function relationships
may help to select the types of synthetic aragonite for specific biomedical applications. Three types of synthetic aragonite
were observed based on grain size and grain morphology.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
47.
NC Day PJ Shaw AL McCormack PJ Craig W Smith R Beattie TL Williams SB Ellis PG Ince MM Harpold D Lodge SG Volsen 《Canadian Metallurgical Quarterly》1996,71(4):1013-1024
The distribution of voltage-dependent calcium channel subunits in the central nervous system may provide information about the function of these channels. The present study examined the distribution of three alpha-1 subunits, alpha 1A, alpha 1B and alpha 1E, in the normal human hippocampal formation and parahippocampal gyrus using the techniques of in situ hybridization and immunocytochemistry. All three subunit mRNAs appeared to be similarly localized, with high levels of expression in the dentate granule and CA pyramidal layer. At the protein level, alpha 1A, alpha 1B and alpha 1E subunits were differentially localized. In general, alpha 1A-immunoreactivity was most intense in cell bodies and dendritic processes, including dentate granule cells, CA3 pyramidal cells and entorhinal cortex pre-alpha and pri-alpha cells. The alpha 1B antibody exhibited relatively weak staining of cell bodies but stronger staining of neuropil, especially in certain regions of high synaptic density such as the polymorphic layer of the dentate gyrus and the stratum lucidum and radiatum of the CA regions. The alpha 1E staining pattern shared features in common with both alpha 1A and alpha 1B, with strong immunoreactivity in dentate granule, CA3 pyramidal and entorhinal cortex pri-alpha cells, as well as staining of the CA3 stratum lucidum. These findings suggest regions in which particular subunits may be involved in synaptic communication. For example, comparison of alpha 1B and alpha 1E staining in the CA3 stratum lucidum with calbindin-immuno-reactivity suggested that these two calcium channels subunits may be localized presynaptically in mossy fibre terminals and therefore may be involved in neurotransmitter release from these terminals. 相似文献
48.
IM McAleer GW Kaplan HC Scherz MG Packer FP Lynch 《Canadian Metallurgical Quarterly》1993,42(5):563-7; discussion 567-8
Trauma is the major source of mortality in the pediatric population. A retrospective review was performed on patients admitted to the Children's Hospital and Health Center Trauma Program, San Diego, California, from August 1984 to May 1990. The purpose of this review was to evaluate pediatric trauma and to determine the best treatment and evaluation for genitourinary injuries. Blunt trauma was responsible for 98 percent of the injuries, with renal injuries being the most common. Bladder (7) and male urethral (2) injuries, and vaginal lacerations (8) also occurred. The most severe renal injuries (70%) and all significant bladder and urethral injuries were associated with gross hematuria. Hypotension was present in 31 percent of patients but rarely required surgical exploration for correction. Eighty-six patients underwent radiographic imaging. Computerized tomography (CT) scans demonstrated the most information about intra-abdominal solid organ injuries but was inaccurate in detecting bladder or urethral injuries. Genitourinary injury is common in children but rarely requires surgical management. CT scan is the best study to determine extent of solid-organ injury but is inferior to cystourethrography to diagnose bladder or urethral injuries. 相似文献
49.
F. S. Kaplan I. G. Shulik L. S. Alekseenko G. P. Orekhova 《Refractories and Industrial Ceramics》1995,36(3):82-85
Casting properties of concentrated aqueous dispersions of zirconia stabilized by Y2O3, Si2O3, or a mixture of them are investigated. Optimum values of the pH, temperature, and slip concentration for the production
of thin-walled vacuum-tight articles are established.
Translated from Ogneupory, No. 3, pp. 12–15, March, 1995. 相似文献
50.
OBJECTIVE: To test the efficacy and safety of low-dose oral pulse methotrexate therapy in patients with idiopathic granulomatous hepatitis who had complications of, did not respond to, or refused glucocorticoid therapy. DESIGN: Prospective case study. SETTING: Academic medical center hospital. PATIENTS: Seven patients with biopsy-proven, idiopathic granulomatous hepatitis who could not tolerate or were unresponsive to glucocorticoid therapy. INTERVENTION: Low-dose oral pulse methotrexate, 15 mg/wk. MEASUREMENTS: Temperature, symptoms, dose of concurrent glucocorticoids, biochemical tests of liver function, side effects of methotrexate, and assessment of liver biopsy specimens. RESULTS: All six febrile patients became afebrile within 3 months of starting methotrexate. Fatigue and anorexia improved in all patients. Glucocorticoid therapy was successfully discontinued within 6 months of starting methotrexate in four patients receiving prednisone at entry. Liver biopsy specimens were obtained again after methotrexate therapy and showed absence of granulomas in four of four patients. The minimum effective dose of methotrexate was 0.20 mg/kg body weight per week. No serious adverse effects and no failures to respond to methotrexate therapy were noted in this group of patients. In three patients, methotrexate therapy has been successfully tapered without signs or symptoms of recurrent disease. CONCLUSIONS: Low-dose oral pulse methotrexate was effective in treating patients with granulomatous hepatitis. 相似文献