全文获取类型
收费全文 | 13180篇 |
免费 | 237篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 148篇 |
综合类 | 9篇 |
化学工业 | 2106篇 |
金属工艺 | 185篇 |
机械仪表 | 395篇 |
建筑科学 | 545篇 |
矿业工程 | 34篇 |
能源动力 | 239篇 |
轻工业 | 1360篇 |
水利工程 | 133篇 |
石油天然气 | 37篇 |
无线电 | 1124篇 |
一般工业技术 | 1733篇 |
冶金工业 | 3961篇 |
原子能技术 | 165篇 |
自动化技术 | 1263篇 |
出版年
2022年 | 91篇 |
2021年 | 129篇 |
2020年 | 108篇 |
2019年 | 124篇 |
2018年 | 117篇 |
2017年 | 165篇 |
2016年 | 151篇 |
2015年 | 110篇 |
2014年 | 218篇 |
2013年 | 623篇 |
2012年 | 312篇 |
2011年 | 462篇 |
2010年 | 410篇 |
2009年 | 406篇 |
2008年 | 455篇 |
2007年 | 442篇 |
2006年 | 435篇 |
2005年 | 369篇 |
2004年 | 319篇 |
2003年 | 329篇 |
2002年 | 308篇 |
2001年 | 252篇 |
2000年 | 229篇 |
1999年 | 267篇 |
1998年 | 852篇 |
1997年 | 561篇 |
1996年 | 477篇 |
1995年 | 361篇 |
1994年 | 323篇 |
1993年 | 310篇 |
1992年 | 166篇 |
1991年 | 179篇 |
1990年 | 195篇 |
1989年 | 200篇 |
1988年 | 193篇 |
1987年 | 175篇 |
1986年 | 168篇 |
1985年 | 184篇 |
1984年 | 158篇 |
1983年 | 151篇 |
1982年 | 119篇 |
1981年 | 142篇 |
1980年 | 117篇 |
1979年 | 138篇 |
1978年 | 128篇 |
1977年 | 155篇 |
1976年 | 241篇 |
1975年 | 108篇 |
1974年 | 103篇 |
1973年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Hook T.B. Brown J. Cottrell P. Adler E. Hoyniak D. Johnson J. Mann R. 《Electron Devices, IEEE Transactions on》2003,50(9):1946-1951
Lateral scattering of retrograde well implants is shown to have an effect on the threshold voltage of nearby devices. The threshold voltage of both NMOSFETs and PMOSFETs increases in magnitude for conventional retrograde wells, but for triple-well isolated NMOSFETs the threshold voltage decreases for narrow devices near the edge of the well. Electrical data, SIMS, and SUPREM4 simulations are shown that elucidate the phenomenon. 相似文献
2.
Barch Deanna M.; Mitropoulou Vivian; Harvey Philip D.; New Antonia S.; Silverman Jeremy M.; Siever Larry J. 《Canadian Metallurgical Quarterly》2004,113(4):556
Research suggests that schizotypal personality disorder (SPD) is a part of the spectrum of schizophrenia-related illnesses. This article hypothesizes that a deficit in the representation and maintenance of context is a core cognitive disturbance in schizophrenia and that SPD individuals should demonstrate context-processing deficits. To test this hypothesis, the authors administered 3 versions of their AX-CPT task, designed to assess context processing, to 35 healthy controls and 26 individuals with DSM-IV SPD. They also administered working memory and selective attention tasks. SPD individuals displayed context representation deficits similar to those found in schizophrenia but did not show the same additional deficits in context maintenance. Context processing was strongly associated with working memory and selective attention performance in the SPD individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
Examination of the wreckage of a light aircraft revealed that approximately 20 cm was missing from one tip of the aluminum
alloy propeller. Fractographic and metallographic examination of the remaining portion of the propeller revealed extensive
grain-boundary separation in the vicinity of the fracture, and grain edges and corners rounded by corrosion on the fracture
surface. Energy dispersive X-ray analysis (EDXA) revealed fluorine on, and in the vicinity of, the fracture surface. In the
ensuing litigation, it was asserted that the crash occurred because the propeller fractured in flight as the result of intergranular
attack caused by the use of a fluorine-bearing cleaner. 相似文献
4.
To meet the criteria of role accountability, nursing competence and ongoing staff development, an improved peer-evaluation system was designed to continuously monitor these new roles. This peer-evaluation process converts evaluation input into data, giving staff a visual picture of how their performance compares within their peer group. This peer-evaluation process was designed as a tool to assist in staff growth and development, not as a punitive system. 相似文献
5.
6.
Marginal costs of electricity vary by time and location. In the past, researchers attributed the variations to factors related to electricity generation and transmission. These authors, however, have not analyzed possible variations in marginal distribution capacity costs (MDCC). The objectives of this paper are:
- 1. (i) to show that large MDCC variations are due to the dispersion in distribution capital expenditures by time and space,
- 2. (ii) to propose a method for quantifying the area- and time-specific MDCC in the presence of lumpy investments, and
- 3. (iii) to compare our MDCC estimates to those commonly used in the electric utility industry.
7.
Serum total cholesterol, high density lipoprotein (HDL) cholesterol, and triglyceride levels were studied in healthy male
and female subjects consuming for one-week periods a diet of conventional food (CF) providing 42% of energy as fat, principally
butter fat, and then in random order nutritionally complete, defined formula diets of moderate (32%) to very low (1%) fat
content. Compared to CF, the formula with 32% of energy as corn oil lowered serum cholesterol by 25% and the ratio of total
to HDL-cholesterol by 13%. Low (9%) and very low (1–3%) fat formulas reduced HDL-cholesterol by as much as 40%, raised the
total: HDL-cholesterol ratio by about 20% and raised serum triglyceride levels by as much as 100%. When low and very low fat
formulas were ingested for three weeks, these effects persisted although maximal responses occurred during the first week.
These results demonstrated that a moderate fat formula diet with a high P/S ratio had a more favorable effect on serum lipid
levels than various low fat formulas. Low fat conventional food diets should be studied in long-term controlled metabolic
experiments before such diets are recommended to the general population for coronary heart disease or cancer prevention. 相似文献
8.
K.L. Johnson J.A. Greenwood J.G. Higginson 《International Journal of Mechanical Sciences》1985,27(6):383-396
A complete solution in closed form to the elastic contact of a one-dimensional sinusoidal surface with a flat surface was presented by Westergaard in 1939. This paper is concerned with the elastic contact of a two-dimensional sinusoidal surface with a flat. In this case the stress distribution within the elastic solids is three-dimensional. As the load is increased the contact areas change in shape from being circular to square and finally leave a circular region of no contact when the waves are almost squashed flat. The problem is solved in general using a numerical method due to Kalker, but asymptotic solutions in closed form have been found for light loads and also for heavy loads at which contact is almost complete. The variation of the mean separation with load, which determines the volume of the space trapped between the two surfaces, is also found. 相似文献
9.
10.