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排序方式: 共有339条查询结果,搜索用时 15 毫秒
31.
A three-part series presents the development of models for predicting the local thermal sensation (Part I) and local thermal comfort (Part II) of different parts of the human body, and also the whole-body sensation and comfort (Part III) that result from combinations of local sensation and comfort. The models apply to sedentary activities in a range of environments: uniform and non-uniform, stable and transient. They are based on diverse findings from the literature and from body-part-specific human subject tests in a climate chamber. They were validated against a test of automobile passengers. The series is intended to present the models’ rationale, structure, and coefficients, so that others can test them and develop them further as additional empirical data becomes available.A) The whole-body (overall) sensation model has two forms, depending on whether all of the body's segments have sensations effectively in the same direction (e.g warm or cool), or whether some segments have sensations opposite to those of the rest of the body. For each, individual body parts have different weights for warm versus cool sensations, and strong local sensations dominate the overall sensation. If all sensations are near neutral, the overall sensation is close to the average of all body sensations.B) The overall comfort model also has two forms. Under stable conditions, people evaluate their overall comfort by a complaint-driven process, meaning that when two body parts are strongly uncomfortable, no matter how comfortable the other body parts might be, the overall comfort will be near the discomfort level of the two most uncomfortable parts. When the environmental conditions are transient, or people have control over their environments, overall comfort is better than that of the two most uncomfortable body parts. This can be accounted for by adding the most comfortable vote to the two most uncomfortable ones. 相似文献
32.
Over the past 30 years borage (Borago officinalis) has become established as a speciality oilseed crop grown exclusively for its oil, a rich source of gamma linolenic acid (GLA), C18 : 3n – 6. GLA is metabolised in the human body from linoleic acid and is itself a precursor in the formation of dihomo‐gammalinolenic acid, arachidonic acid and metabolites of these, prostaglandins, leukotrienes and thromboxanes. The oil is used extensively in the nutritional supplements, cosmetics and pet care industries primarily for its anti‐inflammatory and skin health properties. Global usage is estimated to be approximately 1000 tonnes per year and oil is usually traded on the basis of its GLA content with higher contents attracting a premium commercially. In recent years the development of competitively priced high GLA sources, particularly oils from genetically modified safflower have resulted in an increase in the aduleration of borage oil to raise GLA levels. Analytical and statistical techniques have now been developed to assist authenticating borage oil samples. 相似文献
33.
Charlie A. Ernesto Rida T. Farouki 《The International Journal of Advanced Manufacturing Technology》2010,49(5-8):589-604
For CNC machines governed by typical feedback controllers, the problem of compensating for inertia and damping of the machine axes is solved by a priori modifications to the commanded path geometry. Standard second-order models of axis dynamics are expressed in terms of the path parameter ξ rather than the time t as independent variable, incurring ordinary differential equations with polynomial coefficients. For a commanded path specified as a Pythagorean-hodograph curve R(ξ) and a P controller, a modified path $\hat{\bf R}(\xi)$ can be determined as a rational Bézier curve, that precisely compensates for the axis inertia and damping, and thus (theoretically) achieves zero contour error. For PI, PID, or P–PI controllers, exact closed-form solutions for $\hat{\bf R}(\xi)$ are no longer possible, but polynomial approximations may be computed in the numerically stable Bernstein basis on ξ?∈?[ 0,1 ]. The inverse-dynamics path modification procedure is applicable to both constant feedrates and variable feedrates defined by polynomial functions V(ξ) of the curve parameter. The method is described in the general context of PID controllers, and its implementation is then demonstrated for both P and PI controllers, governing motion along paths with extreme variations of curvature and/or parametric speed. 相似文献
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Charlie A. Ernesto Rida T. Farouki 《The International Journal of Advanced Manufacturing Technology》2012,58(1-4):327-338
To exactly execute a sharp corner in the toolpath, the feedrate of a CNC machine must instantaneously drop to zero at that point. This constraint is problematic in the context of high-speed machining, since it incurs very high deceleration/acceleration rates near sharp corners, which increase the total machining time, and may incur significant path deviations (contour errors) at these points. A strategy for negotiating sharp corners in high-speed machining is proposed herein, based upon a priori toolpath/feedrate modifications in their vicinity. Each corner is smoothed by replacing a subset of the path that contains it with a conic “splice” segment, deviating from the exact corner by no more than a prescribed tolerance ?, along which the square of the feedrate is specified as a Bernstein-form polynomial. The problem of determining the fastest traversal of the conic segments under known axis acceleration bounds can then be formulated as a constrained optimization problem, and by exploiting some well-known properties of Bernstein-form polynomials this can be approximated by a simple linear programming task. Some computed examples are presented to illustrate the implementation and performance of the high-speed cornering strategy. 相似文献
36.
Minc N Fütterer C Dorfman KD Bancaud A Gosse C Goubault C Viovy JL 《Analytical chemistry》2004,76(13):3770-3776
We present an experimental study of the microfluidic electrophoresis of long DNA in self-assembling matrixes of magnetic bead columns. Results are presented for the rapid separation of lambda-phage, 2lambda-DNA, and bacteriophage T4 DNA, where separation resolutions greater than 2 between lambda and T4 are achieved in times as short as 150 s. The use of a computer-piloted flow control system and injection results in high reproducibility between separations. We compare the experimentally measured mobility and dispersion with an exactly solvable lattice Monte Carlo model. The theory predicts that the mean velocity scales linearly with the field, the band broadening scales with the inverse of the field, and the resolution is independent of the field for intermediate fields-all of which are in accord with the experimental results. Moreover, reasonable quantitative agreement is achieved for band broadening for longer DNA (2lambda and T4) when the average postengagement time is measured experimentally. This work demonstrates the possibility of achieving fast microfluidic separation of large DNA on a routine basis. 相似文献
37.
台湾建筑奖创立于1979年,是台湾岛内最具信誉的建筑奖.34年来共评选出百余奖项,成为见证台湾建筑发展的重要里程碑台湾建筑不懈的追求,使其在亚洲和大中华地区独树帜.笔者参与了2012年台湾建筑奖的评选活动,在此分享所见所感,希望加强两岸三地的交流和整合. 相似文献
38.
This paper addresses the problem of computing planar patterns for compression garments. In the garment industry, the compression garment has been increasingly widely used to retain the shape of a human body, where certain strain (or normal pressure) is designed at some places on the compression garment. Variant values and distribution of strain can only be generated by sewing different two-dimensional (2D) patterns and warping them onto the body. We present a physical/geometric approach for computing 2D meshes that, when folded onto the three-dimensional (3D) body, can generate a user-defined strain distribution through proper distortion. This is opposite to the widely studied mesh parameterization problem, whose objective is to minimize the distortion between the 2D and 3D meshes in angle, area or length. 相似文献
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Julie Yu-Chih Liu Hun-Gee Chen Charlie C. Chen Tsong Shin Sheu 《International Journal of Project Management》2011,29(5):547-556
Interpersonal conflict and user requirements uncertainty are pervasive phenomena that plague information systems projects. Relevant literature indicates that interpersonal conflicts can negatively affect information system (IS) projects, even after controlling for the effects of conflict management and resolution. However, the negative emotional characteristics of conflict alone have limited explanatory power with regard to IS project success. The purpose of this study is to provide additional insights into this phenomenon by examining the impact on IS project performance made by the interaction between interpersonal conflict and requirement uncertainty (which comprises both diversity and instability). The authors surveyed the top 1600 companies in Taiwan and the results revealed that requirements instability would lead to potential interpersonal conflict and interpersonal conflict was directly associated with requirements diversity which, in turn, was negatively associated with final project performance. 相似文献