全文获取类型
收费全文 | 663篇 |
免费 | 36篇 |
学科分类
工业技术 | 699篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 18篇 |
2017年 | 17篇 |
2016年 | 12篇 |
2015年 | 16篇 |
2014年 | 23篇 |
2013年 | 46篇 |
2012年 | 30篇 |
2011年 | 57篇 |
2010年 | 56篇 |
2009年 | 36篇 |
2008年 | 44篇 |
2007年 | 42篇 |
2006年 | 48篇 |
2005年 | 24篇 |
2004年 | 25篇 |
2003年 | 12篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有699条查询结果,搜索用时 312 毫秒
41.
42.
Presents an obituary for Raymond J. Corsini, one of psychology’s most prolific authors and editors. Ray’s most important contributions include editing an award-winning four-volume encyclopedia of psychology (1994, Wiley), a dictionary of psychology (1999, Brunner/ Mazel), and one of the leading graduate texts on psychotherapy (Corsini & Wedding, 8th ed., 2008, Cengage), which was translated into more than a dozen languages. However, Ray took the greatest pride in the development of the Corsini 4-R system (also known as Individual Education), an innovative approach to school system reform reform based on democratic principles and Adlerian psychology. (The four Rs were responsibility, respect, resourcefulness, and responsiveness.) Corsini died in Honolulu on November 8, 2008. He is survived by his physician wife, Kleona Rigney, and his social worker daughter, Evelyn Anne Corsini. Both share Ray’s passionate commitment to Adlerian social interest. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
Ran Yan Danny Lynch Thibault Cayron Dimitri Lederer Aryan Afzalian Chi-Woo Lee Nima Dehdashti J.P. Colinge 《Solid-state electronics》2008,52(12):1872-1876
In this paper, we investigate random doping fluctuation effects in trigate SOI MOSFETs by solving the three-dimensional (3D) Poisson, drift-diffusion and continuity equations numerically. A single doping impurity atom is introduced in the undoped channel region of the device and the resulting shift of threshold voltage is measured from the simulated I–V characteristics. This enables the derivation of the threshold voltage shift (ΔVTH) for any arbitrary location of the doping atom in the transistor. Based on an analysis of a sub-20 nm trigate MOSFET device, we find that the typical variation of VTH per doping atom is a few tens of mV. Inversion-mode (IM) trigate devices are more sensitive to the doping fluctuation effects than accumulation-mode (AM) devices. The threshold voltage shift arising from doping fluctuations is maximum when the doping atom is near the center of the channel region, which means the original SOI film doping, the random contamination effects or any other impurity doping in the channel region is more important than atoms introduced in the channel by the S/D implantation process for sub-20 nm transistors. 相似文献
44.
Atomic stick–slip friction has been predicted by molecular dynamics simulation and observed in experiments. However, direct
quantitative comparison of the two has thus far not been possible because of the large difference between scanning velocities
accessible to simulations and experiments. In general, the slowest sliding speeds in MD simulations are at least five orders
of magnitude larger than the upper limit available to experimentalists. To take a step toward bridging this gap, we have applied
parallel replica dynamics, an accelerated molecular dynamics method, to the simulation of atomic stick–slip. The method allows
molecular simulations to run parallel in time in order to extend their duration, thereby enabling lower scanning velocities.
We show here that this method is able to predict atomic stick–slip friction accurately and efficiently at scanning speeds
several orders of magnitude slower than standard molecular dynamics simulations. The accuracy and usefulness of this method
is illustrated by correct prediction of the logarithmic dependence of friction on velocity. 相似文献
45.
We report here our preliminary investigations on the mechanism of α-TTP-mediated ligand transfer as assessed using fluorescence
resonance energy transfer (FRET) assays. These assays monitor the movement of the model α-tocopherol fluorescent derivative
((R)-2,5,7,8-tetramethyl-chroman-2-[9-(7-nitro-benzo[1,2,5]oxadiazol-4-yl amino)-nonyl]-chroman-6-ol; NBD-Toc) from protein to
acceptor vesicles containing the fluorescence quencher TRITC-PE. We have found that α-TTP utilizes a collisional mechanism
of ligand transfer requiring direct protein–membrane contact, that rates of ligand transfer are greater to more highly curved
lipid vesicles, and that such rates are insensitive to the presence of anionic phospholipids in the acceptor membrane. These
results point to hydrophobic features of α-TTP dominating the binding energy between protein and membrane.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
An erratum to this article can be found at 相似文献
46.
The Choice Coordination Problem requiresn asynchronous processes to reach a common choice of one out ofk possible alternatives. Processes communicate viak shared variables. Up tot, t, of the processes may fail to operate by suddenly quitting the protocol. Rabin (1982) presented lower and upper bounds for the extreme caset=n–1. We present deterministic and randomized algorithms for arbitraryt using an alphabet of sizeO(t
2). A semi-synchronous model is also studied. A reduction to a consensus problem proves the necessity to assume some powerful atomic shared-memory operations. 相似文献
47.
Synchronized External Pulsation for Improved Tolerance to Acceleration Stress: Model Studies and Preliminary Experiments 总被引:1,自引:0,他引:1
Moore Thomas W. Jaron Dov Chu Chia-Lin Dinnar Uri Hrebien Leonid White Michael J. Hendler Edwin Dubin Stephen 《IEEE transactions on bio-medical engineering》1985,(2):158-165
Synchronized external pulsation is proposed as a method to improve tolerance to acceleration stress. This technique uses a modified anti-G suit which is pressurized and depressurized synchronously with the heart cycle. The feasibility of the procedure has been studied using a computer model of the cardiovascular system which includes the effects of Gz stress, and contains simulations of baroreceptor control of heart rate and venous tone. Model predictions indicate that for unprotected subjects, carotid pressure at eye level (ophthalmic artery pressure) decreases to 20 mmHg (beginning of central light loss) at approximately +3.6 Gz. Applying standard anti-G suit pressure to the model increases this level to 5.3 Gz. When synchronized external pulsation of 2 psi is superimposed on the standard anti-G suit pressure, the tolerance to acceleration stress is further augmented by at least 0.9 G above the protection afforded by the standard anti-G suit alone. A set of preliminary experiments on human subjects to test the feasibility of using the technique in the high-G environment has also been carried out. The results under various protection modes compare favorably to the model predictions. Our results suggest that the computer model presented here is a useful tool for studying cardiovascular responses under +GZ stress. It also indicates that using synchronized external pulsation pressure superimposed on the standard anti-G suit pressure may offer extra protection to acceleration stress. 相似文献
48.
We study the problem of parallel computation of a schedule for a system of n unit-length tasks on m identical machines, when the tasks are related by a set of precedence constraints. We present NC algorithms for computing an optimal schedule in the case where m, the number of available machines, does not vary with time and the precedence constraints are represented by a collection of outtrees. The algorithms run on an exclusive read, exclusive write (EREW) PRAM. Their complexities are O(log n) and O((log n)2) parallel time using O(n2) and O(n) processors, respectively. The schedule computed by our algorithms is a height-priority schedule. As a complementary result we show that it is very unlikely that computing such a schedule is in NC when any of the above conditions is significantly relaxed. We prove that the problem is P-complete under logspace reductions when the precedence constraints are a collection of intrees and outtrees, or for a collection of outtrees when the number of available machines is allowed to increase with time. The time span of a height-priority schedule for an arbitrary precedence constraints graph is at most 2 − 1/(m − 1) times longer than the optimal (N. E Chen and C. L. Liu, Proc. 1974 Sagamore Computer Conference on Parallel Processing, T. Fend (Ed.), Springer-Verlag, Berlin, 1975, pp. 1–16). Whereas it is P-complete to produce the classical height-priority schedules even for very restricted precedence constraints graphs, we present a simple NC parallel algorithm which produces a different schedule that is only 2 − 1/m times the optimal. 相似文献
49.
This paper presents the development of an optimal interval Newton method for systems of nonlinear equations. The context of solving such systems of equations is that of optimization of nonlinear mathematical programs. The modifications of the interval Newton method presented in this paper provide computationally effective enhancements to the general interval Newton method. The paper demonstrates the need to compute an optimal step length in the interval Newton method in order to guarantee the generation of a sequence of improving solutions. This method is referred to as the optimal Newton method and is implemented in multiple dimensions. Secondly, the paper demonstrates the use of the optimal interval Newton method as a feasible direction method to deal with non-negativity constraints. Also, included in this implementation is the use of a matrix decomposition technique to reduce the computational effort required to compute the Hessian inverse in the interval Newton method. The methods are demonstrated on several problems. Included in these problems are mathematical programs with perturbations in the problem coefficients. The numerical results clearly demonstrate the effectiveness and efficiency of these approaches. 相似文献
50.
Processing of Boron Carbide-Aluminum Composites 总被引:4,自引:0,他引:4
Danny C. Halverson ; Aleksander J. Pyzik IIhan A. Aksay William E. Snowden 《Journal of the American Ceramic Society》1989,72(5):775-780
The processing problems associated with boron carbide and the limitations of its mechanical properties can be significantly reduced when a metal phase (e.g., aluminum) is added. Lower densification temperatures and higher fracture toughness will result. Based on fundamental capillarity ther modynamics, reaction thermodynamics, and densification kinetics, we have established reliable criteria for fabricating B4 C–Al particulate composites. Because chemical reactions cannot be eliminated, it is necessary to process B4 C–AI by rapidly heating to near 1200°C (to ensure wetting) and subsequently heat-treating below 1200°C (for microstructural development). 相似文献