全文获取类型
收费全文 | 2752篇 |
免费 | 41篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 253篇 |
金属工艺 | 28篇 |
机械仪表 | 24篇 |
建筑科学 | 80篇 |
矿业工程 | 14篇 |
能源动力 | 59篇 |
轻工业 | 138篇 |
水利工程 | 16篇 |
石油天然气 | 16篇 |
武器工业 | 3篇 |
无线电 | 253篇 |
一般工业技术 | 274篇 |
冶金工业 | 1314篇 |
原子能技术 | 26篇 |
自动化技术 | 284篇 |
出版年
2021年 | 18篇 |
2019年 | 14篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 26篇 |
2015年 | 21篇 |
2014年 | 26篇 |
2013年 | 105篇 |
2012年 | 43篇 |
2011年 | 74篇 |
2010年 | 39篇 |
2009年 | 43篇 |
2008年 | 68篇 |
2007年 | 57篇 |
2006年 | 60篇 |
2005年 | 50篇 |
2004年 | 36篇 |
2003年 | 46篇 |
2002年 | 44篇 |
2001年 | 31篇 |
2000年 | 39篇 |
1999年 | 75篇 |
1998年 | 372篇 |
1997年 | 224篇 |
1996年 | 162篇 |
1995年 | 86篇 |
1994年 | 108篇 |
1993年 | 94篇 |
1992年 | 42篇 |
1991年 | 35篇 |
1990年 | 49篇 |
1989年 | 51篇 |
1988年 | 41篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 32篇 |
1984年 | 33篇 |
1983年 | 30篇 |
1982年 | 19篇 |
1981年 | 23篇 |
1980年 | 38篇 |
1979年 | 19篇 |
1978年 | 24篇 |
1977年 | 56篇 |
1976年 | 109篇 |
1975年 | 18篇 |
1974年 | 11篇 |
1973年 | 21篇 |
1971年 | 14篇 |
1970年 | 10篇 |
排序方式: 共有2795条查询结果,搜索用时 15 毫秒
31.
A variant of the boundary element method, called the boundary contour method (BCM), offers a further reduction in dimensionality.
Consequently, boundary contour analysis of two-dimensional (2-D) problems does not require any numerical integration at all.
While the method has enjoyed many successful applications in linear elasticity, the above advantage has not been exploited
for Stokes flow problems and incompressible media. In order to extend the BCM to these materials, this paper presents a development
of the method based on the equations of Stokes flow and its 2-D kernel tensors. Potential functions are derived for quadratic
boundary elements. Numerical solutions for some well-known examples are compared with the analytical ones to validate the
development.
Received 28 August 2001 / Accepted 15 January 2002 相似文献
32.
H Langen C Gray D R?der JF Juranville B Takacs M Fountoulakis 《Canadian Metallurgical Quarterly》1997,18(7):1184-1192
High-resolution two-dimensional (2-D) polyacrylamide gel electrophoresis allows the separation of complex biological mixtures (i.e., several hundred proteins from a bacterial cell lysate) in a single experiment. In this report proteins from Haemophilus influenzae were separated by 2-D gels and analyzed by peptide mass fingerprinting and/or amino acid analysis. By comparing the peptide mass profiles and the amino acid composition with the Haemophilus influenzae database, 119 protein spots were identified. The combination of amino acid analysis and peptide mass fingerprinting is a powerful tool for a rapid and economical identification of a large number of proteins resolved by 2-D gels. Studies on gene regulation and changes of protein expression upon drug treatment require quick and serial analysis techniques to efficiently identify potential new drug targets. 相似文献
33.
MJ Prado AL Nicastri PL Costa T Rockman IL Tersariol HB Nader RT Barros EB Prado 《Canadian Metallurgical Quarterly》1997,30(7):865-872
The aim of the present study was to evaluate renal and liver distribution of two monoclonal immunoglobulin light chains. The chains were purified individually from the urine of patients with multiple myeloma and characterized as lambda light chains with a molecular mass of 28 kDa. They were named BJg (high amount of galactose residues exposed) and BJs (sialic acid residues exposed) on the basis of carbohydrate content. A scintigraphic study was performed on male Wistar rats weighing 250 g for 60 min after i.v. administration of 1 mg of each protein (7.4 MBq), as the intact proteins and also after carbohydrate oxidation. Images were obtained with a Siemens gamma camera with a high-resolution collimator and processed with a MicroDelta system. Hepatic and renal distribution were established and are reported as percent of injected dose. Liver uptake of BJg was significantly higher than liver uptake of BJs (94.3 vs 81.4%) (P < 0.05). This contributed to its greater removal from the intravascular compartment, and consequently lower kidney accumulation of BJg in comparison to BJs (5.7 vs 18.6%) (P < 0.05). After carbohydrate oxidation, there was a decrease in hepatic accumulation of both proteins and consequently a higher renal overload. The tissue distribution of periodate-treated BJg was similar to that of native BJs: 82.7 vs 81.4% in the liver and 17.3 vs 18.6% in the kidneys. These observations indicate the important role of sugar residues of Bence Jones proteins for their recognition by specific membrane receptors, which leads to differential tissue accumulation and possible toxicity. 相似文献
34.
We study non-linear behaviour in a model chemical reaction scheme (proposed by Sal?nikov), in which a single chemical species undergoes a two-stage, first-order decay process. The second stage is exothermic and has a temperature-dependent rate, and as a result, spontaneous oscillations in the temperature and the concentration of an intermediate chemical are known to be possible. An additional oscillation is imposed on the system by varying the ambient temperature in a sinusoidal manner. Primary resonance occurs when the forcing frequency coincides with the frequency of the natural oscillations in this scheme and an infinite sequence of super-and subharmonic resonances is also present. Chaos is possible for appropriate parameter values and may result either from the Feigenbaum period-doubling cascade, or else as a result of the Ruelle-Takens approach through quasi-periodicity. 相似文献
35.
36.
37.
Su Vida, Su Salud/Your Life, Your Health is a community program to increase participation in breast and cervical cancer screening. This program illustrates the diffusion of an innovative outreach strategy from a research environment to two local health departments. The program uses A Su Salud, the communication model in which positive role models are featured in the media, and community volunteers who give positive social reinforcement. Local health departments in Galveston and Corpus Christi, TX, were selected to implement the model because of excessive mortality rates in the region and the departments' adequate level of resources and commitment. Over an 18-month period, 54 stories of role models appeared in the media in Corpus Christi, and 60 appeared in Galveston. There were 490 volunteers active in Corpus Christi and 279 in Galveston. Of 365 inquiries to the Corpus Christi program, 35 percent were from the Mexican American target group of women ages 40-70. Of 1,457 women who contacted the Galveston program, 9 percent were from the African American target group ages 40-70. Local health departments are well-suited to participation in cancer control research applications because they have direct access to high-risk populations and have the authority to institutionalize effective interventions. 相似文献
38.
39.
HB Joshi 《Canadian Metallurgical Quarterly》1997,88(9):197-198
40.
Kovera Margaret Bull; Gresham April W; Borgida Eugene; Gray Ellen; Regan Pamela C 《Canadian Metallurgical Quarterly》1997,82(1):178
The authors examined whether expert testimony serves an educational or a persuasive function. Participants watched a simulated sexual abuse trial in which the child witness had been prepared for her testimony (i.e., she was calm, composed, and confident) or unprepared (i.e., emotional, confused, and uncertain). The trial contained different levels of expert testimony: none, standard (i.e., a summary of the research), repetitive (i.e., standard testimony plus a 2nd summary of the research), or concrete (i.e., standard testimony plus a hypothetical scenario linking the research to the case facts) testimony. Repetitive testimony bolstered the child's testimony, whereas concrete and standard testimony did not. Concrete testimony sensitized jurors to behavioral correlates of sexual victimization; standard and repetitive testimony desensitized jurors to these correlates. Implications for the use of procedural innovations in sexual abuse trials are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献