全文获取类型
收费全文 | 492篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 76篇 |
金属工艺 | 2篇 |
机械仪表 | 2篇 |
建筑科学 | 25篇 |
轻工业 | 40篇 |
水利工程 | 3篇 |
无线电 | 13篇 |
一般工业技术 | 54篇 |
冶金工业 | 246篇 |
自动化技术 | 38篇 |
出版年
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2018年 | 4篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 11篇 |
2012年 | 9篇 |
2011年 | 25篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 23篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 21篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 12篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1958年 | 3篇 |
排序方式: 共有500条查询结果,搜索用时 15 毫秒
11.
The cooling power of aqueous solutions of ethylene oxide-propylene oxide copolymers are studied with a silver standard sample by using two apparatuses quench with injection and quench with agitation. For temperature T>400°C, the viscosity plays the predominant role; for T<400°C, the cooling is controlled by the polymer precipitation and the cooling rate decreases by lowering the cloud point of the polymer solution. This work demonstrates the possibility of adjusting the cooling curves by taking into account the thermodynamical properties of the polymer. 相似文献
12.
Hypothesized that college women's locus of control orientations would be related to their role expectations, with women with an external locus of control having lower aspirations, more conservative sex-role ideologies, and less involvement in career planning than women with an internal locus of control. 116 female college juniors and seniors completed a career expectation scale, the Adult Nowicki-Strickland Internal-External Control Scale (ANSIE), and an index of sympathy for women's liberation ideology. Regression analyses using ANSIE scores as the predictor variable supported the hypotheses. Compared to Ss with internal orientations, Ss with external orientations expected to have less commitment to their careers, to work for a smaller portion of their lives, and to feel more discomfort due to violating sex-role stereotypes. In addition, Ss with a more external orientation reported less career planning activity, less positive feelings about their future careers, and more conservative views on women's liberation ideology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
Previous research examined sanitation treatments on cut cantaloupe tissue to deliver germicidal and food safety effects. However, an apparent compromise between volatile loss and treatment/sampling efficacy appeared. Subsequently, a physiological and volatile reassessment of thinly sliced tissue against cubes was performed in cantaloupe tissue. Thin sliced cantaloupe L* decreased 27.5%, 40.5%, and 52.9% in 3, 2, and 1 mm thickness, respectively, compared with cut cubes after 3 d. Overall color (C) decreased in freshly prepared cubes (2.4%) and slices (14.4%) that were washed in cold water. Surface area per unit volume (SA: vol) in slices was 4.1 times greater than typical cubes, as reflected by substantial water loss (20.4%, 9.5%, and 6.7% in 1, 2 and 3-mm slices, respectively) after 1 d at 5 °C. Rinsing cubes and thin-slices with 5 °C deionized water resulted in roughly 15% soluble solids loss. SEM indicated 65.4% reduced cell size in 1-d old thin slices, evidenced by excessive cell damage and desiccation compared with stored fresh-cut cubes. In thin-sliced tissue exposed 15 min to an open atmosphere (mimic sanitation treatments), total esters decreased 92.8% and 95.8%, respectively, after 1 and 3 d storage at 5 °C. Washing tissue provided a boundary layer that reduced short-term ester losses in slices and cubes. Excessive cutting, sanitation treatment regimes, and storage can radically alter the desirable volatile profile of cut cantaloupe. Reduction of tissue size to maximize food-safety sanitation efficacy or delivering items to a niche market will need substantial work to engineer equipment and develop protocols to insure that product quality and volatiles are not compromised. PRACTICAL APPLICATION: We have demonstrated that cutting method and sampling protocol are critically important when using volatiles as a means by which to assess or interpret stress response and ascribe fresh-cut quality. Reduction of tissue size to maximize food-safety sanitation efficacy (for example, thin slices) will need substantial work to engineer equipment and design protocols to insure product quality and volatile profiles are not compromised. 相似文献
14.
G. Stanley Hall influenced several social movements that had great implications for child wellbeing: the Child Study, Parent Education, and Child Welfare Movements. However, while Hall laid much of the foundation for the field of scientific child study and policy-relevant research, his legacy is virtually nonexistent. The current article reviews the life and contributions of G. Stanley Hall, and the dual role Hall played in history as a revered leader of the Child Study Movement and a controversial figure in the landscape of early child psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
Ahmed K. Noor Jeanne M. Peters 《Computer Methods in Applied Mechanics and Engineering》1981,28(2):217-240
A reduced basis technique and a problem-adaptive computational algorithm are presented for predicting the post-limit-point paths of structures. In the proposed approach the structure is discretized by using displacement finite element models. The nodal displacement vector is expressed as a linear combination of a small number of vectors and a Rayleigh-Ritz technique is used to approximate the finite element equations by a small system of nonlinear algebraic equations.To circumvent the difficulties associated with the singularity of the stiffness matrix at limit points, a constraint equation, defining a generalized arc-length in the solution space, is added to the system of nonlinear algebraic equations and the Rayleigh-Ritz approximation functions (or basis vectors) are chosen to consist of a nonlinear solution of the discretized structure and its various order derivatives with respect to the generalized arc-length. The potential of the proposed approach and its advantages over the reduced basis-load control technique are outlined. The effectiveness of the proposed approach is demonstrated by means of numerical examples of structural problems with snap-through and snap-back phenomena. 相似文献
16.
17.
Frieman Jeanne P.; Rohrbaugh Michael; Riccio David C. 《Canadian Metallurgical Quarterly》1969,23(4):237
Administered 10 inescapable shocks to 38 male Holtzman infant and adult albino rats in the presence of a 450-cps tone (CS) while Ss were confined in 1 compartment of a double-compartment shuttle box. Each S subsequently received 20 4-min trials (without shocks) in which a 230-, 450-, or 1000-cps tone, or no-tone, was made contingent upon S's presence in the former shock (fear) compartment. 8 Ss served as controls. Time spent avoiding the fear compartment during the various tone conditions revealed a steeper group gradient for pups than for adults, although mean avoidance of the CS condition was comparable for both groups. Individual stimulus generalization gradients were observed in 8 of 10 infants and 2 of 10 adults. Data are discussed in relation to the nature of maturational experience. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
In this paper we propose an effective watermark scheme for embedding and extracting based on the JPEG2000 Codec process. Our embedding algorithm applies the torus automorphisms (TA) technique to break up and scramble a watermark. The scrambled watermark was embedded into the quantized bitstreams of JPEG2000 before the entropy coding stage. Distortion reduction (DR) was applied to the compressed image to lessen image degradation caused by the embedding process. Our watermark scheme is simple and easy to implement. Furthermore, it is robust to attacks like blurring, edge enhancement, and other image processing manipulations.Corespondence to: J. Chen (P.O. Box 63-146, Taichung, Taiwan 406, R.O.C.) 相似文献
19.
20.
Caspar Franz; Silberschatz George; Goldfried Marvin; Watson Jeanne C. 《Canadian Metallurgical Quarterly》2010,20(1):101
In this article, each author gives a brief comment on similarities he or she sees throughout the case formulations captured in the articles by Watson (2010a), Silberschatz (2010), Goldfried (2010), and Caspar (2010). A systematic comparison is added. Overall, the impression is confirmed and maintained that if authors are ready to renounce the use of the jargon of their specific approach, many similarities can be found. There are nevertheless differences that would lead us to expect a different course of therapy and different effects beyond the main effect of recovery in the case of David, pursuing the conceptualization and interventions proposed by Watson (2010b). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献