全文获取类型
收费全文 | 168553篇 |
免费 | 1177篇 |
国内免费 | 193篇 |
专业分类
电工技术 | 2553篇 |
综合类 | 119篇 |
化学工业 | 26628篇 |
金属工艺 | 9472篇 |
机械仪表 | 5715篇 |
建筑科学 | 3008篇 |
矿业工程 | 1887篇 |
能源动力 | 2705篇 |
轻工业 | 8823篇 |
水利工程 | 2729篇 |
石油天然气 | 8692篇 |
武器工业 | 12篇 |
无线电 | 14494篇 |
一般工业技术 | 38258篇 |
冶金工业 | 27799篇 |
原子能技术 | 6933篇 |
自动化技术 | 10096篇 |
出版年
2018年 | 2978篇 |
2017年 | 3091篇 |
2016年 | 3344篇 |
2015年 | 1672篇 |
2014年 | 2954篇 |
2013年 | 6345篇 |
2012年 | 4311篇 |
2011年 | 5397篇 |
2010年 | 4421篇 |
2009年 | 4894篇 |
2008年 | 4944篇 |
2007年 | 4869篇 |
2006年 | 4143篇 |
2005年 | 3820篇 |
2004年 | 3634篇 |
2003年 | 3521篇 |
2002年 | 3451篇 |
2001年 | 3464篇 |
2000年 | 3363篇 |
1999年 | 3213篇 |
1998年 | 7022篇 |
1997年 | 5149篇 |
1996年 | 3824篇 |
1995年 | 2916篇 |
1994年 | 2596篇 |
1993年 | 2721篇 |
1992年 | 2254篇 |
1991年 | 2307篇 |
1990年 | 2410篇 |
1989年 | 2315篇 |
1988年 | 2313篇 |
1987年 | 2190篇 |
1986年 | 2246篇 |
1985年 | 2292篇 |
1984年 | 2206篇 |
1983年 | 2135篇 |
1982年 | 1981篇 |
1981年 | 2194篇 |
1980年 | 2054篇 |
1979年 | 2269篇 |
1978年 | 2431篇 |
1977年 | 2430篇 |
1976年 | 3095篇 |
1975年 | 2244篇 |
1974年 | 2307篇 |
1973年 | 2342篇 |
1972年 | 2155篇 |
1971年 | 1911篇 |
1970年 | 1701篇 |
1969年 | 1632篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The erucic acid content of broccoli florets, sprouts, and seeds was found to be about 0.8, 320, and 12100 mg/100 g, respectively. Using the erucic acid limit established for canola oil in the U.S.A. and Canada as a guideline, the estimated dietary intake of erucic acid from florets and sprouts was considered of little consequence, whereas in seeds a relatively small amount (about 35 g/wk) equaled our calculated exposure limit for erucic acid. Additionally, the most complete fatty acid distribution yet published for the various forms of broccoli are presented. 相似文献
993.
994.
Scherbatko I.V. Nerukh A.G. Iezekiel S. 《Antennas and Propagation, IEEE Transactions on》2002,50(4):492-499
An enhanced numerical method for solving a one-dimensional (1-D) integro-differential Volterra equation for time- and spatially varying dispersive dielectric media is proposed. The scheme is based on spatial-time discretization (marching scheme) with an enhanced Courant stability condition. The algorithm performs refinement of the results by a prediction-correction scheme and imposes restrictions on neither the signal shape and duration nor on the temporal behavior of the medium and is therefore generic. Results show good correlation with existing theoretical solutions and considerable improvement in precision over previous techniques. The influence of electromagnetic transients in the lossless dielectric layer on reflection and transmission coefficients is investigated 相似文献
995.
C. A. Duarte I. Babuka 《International journal for numerical methods in engineering》2002,55(12):1477-1492
This paper is aimed at presenting a simple yet effective procedure to implement a mesh‐independent p‐orthotropic enrichment in the generalized finite element method. The procedure is based on the observation that shape functions used in the GFEM can be constructed from polynomials defined in any co‐ordinate system regardless of the underlying mesh or type of element used. Numerical examples where the solution possesses boundary or internal layers are solved on coarse tetrahedral meshes with isotropic and the proposed p‐orthotropic enrichment. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
996.
E. V. Grabovski M. K. Krylov V. V. Kuznetsov A. P. Lototsky E. V. Khaustov Yu. A. Khalimullin N. Yu. Kas'yanov A. I. Kormilitsyn V. A. Filatov E. Ya. Shkol'nikov 《Instruments and Experimental Techniques》2002,45(1):67-70
An inductive power-amplifier stage based on a two-coil assembly and two electrically exploded conductors used as circuit breakers is described. Owing to the magnetic flux conservation, the interruption of the current in the first of the storage coils causes an increase of the current in the second coil, which results in a rapid thermal burst of the second electrically exploded conductor. As a result, the load-current rise-time is 20 times less than the charging-current rise time and the amplitude of the current increases. 相似文献
997.
998.
999.
Administering the Neuropsychiatric Inventory (NPI), we examined the behavioral symptoms of 22 patients with progressive supranuclear palsy (PSP), 50 patients with Alzheimer's disease, and 40 controls. PSP patients exhibited apathy (91%), disinhibition (36%), dysphoria (18%) and anxiety (18%), but rarely (< 9%) irritability, abnormal motor behaviors, or agitation. Apathy in PSP was significantly associated with executive dysfunction. The presence of high apathy and low agitation and anxiety scale scores correctly identified the PSP patients 85% of the time. Evaluating the behavioral abnormalities of patients with neurodegenerative disorders will aid diagnosis and facilitate management. 相似文献
1000.