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排序方式: 共有319条查询结果,搜索用时 15 毫秒
1.
In this paper we design a dynamic dictionary for
the priced information model initiated by Charikar et al. Assume that a set S consisting of n elements is given such that
each element has an associated price, a positive real number. The cost of performing an operation on elements of S is a function
of their prices. The cost of an algorithm is the sum of the costs of
all operations it performs. The objective is to design algorithms
which incur low cost. In this model we propose a dynamic dictionary, supporting
search, insert and delete, for keys drawn from a linearly ordered set.
As an application we show that the dictionary can be used in
computing the trapezoidal map of a set of line segments, a fundamental problem in
computational geometry. 相似文献
2.
3.
Topics in Catalysis - An NO2-assisted soot oxidation based filter candidate consists of Pt-coated ceramic foam in combination with a wall-flow monolith is proposed to acquire for an optimal usage... 相似文献
4.
Effects of differences in office chair controls, seat and backrest angle design in relation to tasks
Liesbeth Groenesteijn Peter Vink Michiel de Looze Frank Krause 《Applied ergonomics》2009,40(3):362-370
In this study the influence of chair characteristics on comfort, discomfort, adjustment time and seat interface pressure is investigated during VDU and non-VDU tasks: The two investigated office chairs, both designed according to European and Dutch standards are different regarding: 1) seat cushioning and shape, 2) backrest angle and 3) controls. Thirty subjects in total, both male and female, participated in two experiments: twenty in the first and ten in the second.Significant differences are found for ease of adjustment and adjustment time of controls, independent of the tasks. Related to tasks, a significant difference was found for the backrest range of motion. For non-VDU tasks a larger range of backrest motion was preferred by 70% of the subjects. The chair design differences were most clear for comfort and adjustment time of controls, followed by comfort of backrest angle. No differences are found between seat pan comfort and discomfort, first impressions and peak interface pressure. 相似文献
5.
Groenesteijn L Ellegast RP Keller K Krause F Berger H de Looze MP 《Applied ergonomics》2012,43(2):320-328
In the present study, we investigated the effect of office tasks on posture and movements in field settings, and the comfort rating for chair characteristics and correlation with type of task. The tasks studied were: computer work, telephoning, desk work and conversation. Postures, movements, chair part inclinations and comfort rating data were collected from 12 subjects. Computer work showed the lowest physical activity, together with upright trunk and head position and low backrest inclination. Conversation shows the highest activity of head legs and low back together with the highest cervical spine extension. In contrast, desk work provoked the most cervical spine flexion and showed the second lowest activity. The telephoning tasks showed medium activity and the highest kyphosis. Conversation showed the highest backrest inclination. Positive comfort relations were found for computer work and a "swing system" chair, for telephoning and an active longitudinal seat rotation, and for desk work and a chair with a three-dimensionally moveable seat. 相似文献
6.
Michiel Hazewinkel 《Theory of Computing Systems》1976,10(1):363-385
In this paper we study real linear dynamical systems \(\dot x = Fx + Gu,y = Hx,x \in R^n \) = state space,u ∈ R m = input space,y ∈ R p = output space, under the equivalence relation induced by base change in state space; or in other words we study triples of matrices with real coefficients (F, G, H) of sizesn × n, n × m, p × n respectively, under the action(F, G, H.) →(TFT ?1,TG, HT ?1) ofGL n (R), the group of invertible realn × n matrices. One of the central questions studied is: “do there exist continuous canonical forms for this equivalence relation?”. After various trivial obstructions to the existence of such forms have been removed the answer is very roughly: no ifm ≥ 2, p ≥ 2, yes ifm = 1, orp = 1. For a precise statement cf. theorem 1.7. Existence or nonexistence of continuous canonical forms is related to the existence of a universal family of real linear dynamical systems. More precisely continuous canonical forms exist if such a universal family exists and if the underlying vector bundle of this family is the trivial vector bundle. In the case studied we show that a universal family in the appropriate sense does exist. The methods used are purely (differential) topological and in particular do not involve any algebraic geometry. There is a corresponding algebraic theory over any fieldk instead ofR which is the subject of part III of this series of papers. 相似文献
7.
In this paper we discuss the problem of randomly sampling classes of fixed-interval railway timetables from a so-called timetable structure. Using a standard model for the timetable structure, we introduce a natural partitioning of the set of feasible timetables into classes. We then define a new probability distribution where the probability of each class depends on the robustness of the timetables in that class. Due to the difficulty of sampling directly from this distribution, we propose a heuristic sampling method and illustrate using practical data that our method indeed favors classes containing robust timetables over others. 相似文献
8.
Tom Eeckelaert Raf Schoofs Michiel Steyaert Georges Gielen Willy Sansen 《Analog Integrated Circuits and Signal Processing》2008,55(1):37-45
This paper presents a 3rd-order continuous-time Delta-Sigma modulator with a resolution of 10 bits for a 10 MHz signal bandwidth.
It is designed in a standard 0.18 μm CMOS technology and consumes only 6 mW. After the design/selection of the topologies
for the integrators, comparator and D/A converters, optimal sizing of the complete modulator was ensured by using a hierarchical
bottom-up, multi-objective evolutionary design methodology. With this methodology, a set of Pareto-optimal modulator designs
is generated by using Pareto-optimal performance solutions of the hierarchically decomposed lower-level subblocks. From the
generated Pareto-optimal design set, a final optimal design is chosen that complies with the specifications for the 802.11a/b/g
WLAN standard and has minimal power consumption. 相似文献
9.
10.
Romina Fernández Varela Dr. Ana Laura Valino Dr. Eman Abdelraheem Dr. Rosario Médici Dr. Melisa Sayé Dr. Claudio A. Pereira Dr. Peter-Leon Hagedoorn Prof. Ulf Hanefeld Prof. Adolfo Iribarren Prof. Elizabeth Lewkowicz 《Chembiochem : a European journal of chemical biology》2022,23(13):e202200147
In nature 2-deoxy-D-ribose-5-phosphate aldolase (DERA) catalyses the reversible formation of 2-deoxyribose 5-phosphate from D-glyceraldehyde 3-phosphate and acetaldehyde. In addition, this enzyme can use acetaldehyde as the sole substrate, resulting in a tandem aldol reaction, yielding 2,4,6-trideoxy-D-erythro-hexapyranose, which spontaneously cyclizes. This reaction is very useful for the synthesis of the side chain of statin-type drugs used to decrease cholesterol levels in blood. One of the main challenges in the use of DERA in industrial processes, where high substrate loads are needed to achieve the desired productivity, is its inactivation by high acetaldehyde concentration. In this work, the utility of different variants of Pectobacterium atrosepticum DERA (PaDERA) as whole cell biocatalysts to synthesize 2-deoxyribose 5-phosphate and 2,4,6-trideoxy-D-erythro-hexapyranose was analysed. Under optimized conditions, E. coli BL21 (PaDERA C-His AA C49M) whole cells yields 99 % of both products. Furthermore, this enzyme is able to tolerate 500 mM acetaldehyde in a whole-cell experiment which makes it suitable for industrial applications. 相似文献