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31.
On the Structure of Amorphous Mesoporous Silica Nanoparticles by Aberration‐Corrected STEM 下载免费PDF全文
Sebastian Calderon V Tânia Ribeiro José Paulo S. Farinha Carlos Baleizão Paulo J. Ferreira 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(40)
Mesoporous silica materials have demonstrated a vast spectrum of applications, stimulating an intensive field of study due to their potential use as nanocarriers. Nonetheless, when produced at the nanoscale, their structural characterization is hindered due to the re‐arrangement of the pores. To address this issue, this work combines molecular dynamics simulations with electron microscopy computer simulations and experimental results to provide an insight into the structure of amorphous mesoporous silica nanoparticles. The amorphous silica model is prepared using a simple melt‐quench molecular dynamics method, while the reconstruction of the mesoporous nanoparticles is carried out using a methodology to avoid false symmetry in the final model. Simulated scanning transmission electron microscopy images are compared with experimental images, revealing the existence of structural domains, created by the misalignment of the pores to compensate the surface tension of these spherical nanoparticles. 相似文献
32.
The objective of the present study was to determine the duration of elevated concentrations of progesterone necessary to induce atresia of persistent ovarian follicles. Heifers were administered 25 mg of PGF2alpha on d 6 and 7 (d 0 = d of synchronized estrus) and a norgestomet implant from d 6 to 14. Ovaries were monitored by ultrasonography, and blood samples were collected on d 3, 5, 7, 9, 11, and 12 and daily from d 14 until ovulation. On d 12, heifers received either two progesterone-releasing intravaginal devices (PRID) for 6 h (6-h; n = 5), two PRID for 24 h (24-h; n = 5), or no treatment (CON; n = 5). Blood samples were collected at 15-min intervals from h -6 to 30 (PRID insertion = h 0) and analyzed for concentrations of LH. Characteristics of LH secretion were determined for consecutive 6-h periods (Period 0 to 5). Hourly blood samples, collected from h 0 to 29, were analyzed for concentrations of 17beta-estradiol (estradiol) and progesterone. The dominant ovarian follicles present on d 7 increased in size to 15.4+/-.3 mm on d 12 ("persistent follicle"). Following removal of the PRID and norgestomet implants, atresia of persistent follicles and ovulation of new follicles were induced in one of five and in four of five heifers in the 6-h and 24-h treatments, respectively. Persistent follicles ovulated after withdrawal of norgestomet in all other heifers. Concentrations of progesterone were increased from h 1 to 7 in the 6-h and h 1 to 26 in the 24-h treatment. Frequency of LH pulses was reduced (P < .05) during Periods 1 to 2 in the 6-h and Periods 1 to 5 in the 24-h treatment relative to the CON treatment. By h 10, concentrations of estradiol in the 6-h and 24-h treatments were lower (P < . 05) than in the CON treatment. This suppression continued through h 29 in the 24-h treatment (P < .05), whereas concentrations in the 6-h treatment were intermediate to those of the CON and 24-h treatments after h 14. Suppression of pulsatile LH release and estradiol secretion was evident with 6 and 24 h of treatment with progesterone, but only the 24-h treatment induced atresia of persistent follicles in a majority of the heifers. 相似文献
33.
Horst Kesselmeier Inga Tschiersch Klaus Henning Beate Stoffels Sebastian Kutscha 《AI & Society》1998,12(1-2):55-63
Today technology design can no longer be understood as a design process on a green site. Design and implementation of new technology are always dependent on existing technology and the way it is used by people. In this respect Software-Engineering has also changed to the characteristics of normal technology design taking into account existing computer systems. Experiences show that the conditions and needs of such Software-Reengineering projects are highly complex and differ in their special characteristics ranging from aspects of quality of existing system documentation to organizational structures of the computer departments concerned. The Task-Artifact Cycle presented here gives a suitable reengineering approach emphasizing both analysis and design in Software-Reengineering. 相似文献
34.
Anselm Grundhöfer Daniel Kurz Sebastian Thiele Oliver Bimber 《The Visual computer》2010,26(9):1167-1176
In this article we show how temporal backdrops that alternately change their color rapidly at recording rate can aid chroma
keying by transforming color spill into a neutral background illumination. Since the chosen colors sum up to white, the chromatic
(color) spill component is neutralized when integrating over both backdrop states. The ability to separate both states additionally
allows to compute high-quality alpha mattes. Besides the neutralization of color spill, our method is invariant to foreground
colors and supports applications with real-time demands. In this article, we explain different realizations of temporal backdrops
and describe how keying and color spill neutralization are carried out, how artifacts resulting from rapid motion can be reduced,
and how our approach can be implemented to be compatible with common real-time post-production pipelines. 相似文献
35.
Christian Liebchen Michael Schachtebeck Anita Schöbel Sebastian Stiller André Prigge 《Computers & Operations Research》2010,37(5):857-868
In the past, much research has been dedicated to compute optimum railway timetables. A typical objective has been the minimization of passenger waiting times. But only the planned nominal waiting times have been addressed, whereas delays as they occur in daily operations have been neglected. Delays have been rather treated mainly in an online context and solved as a separate optimization problem, called delay management.We provide the first computational study which aims at computing delay resistant periodic timetables. In particular we assess the delay resistance of a timetable by evaluating it subject to several delay scenarios to which optimum delay management will be applied.We arrive at computing delay resistant timetables by selecting a new objective function which we design to be somehow in the middle of the traditional simple timetabling objective and the sophisticated delay management objective. This is a slight extension of the concept of “light robustness” (LR) as it has been proposed by Fischetti and Monaci [2006. Robust optimization through branch-and-price. In: Proceedings of AIRO]. Moreover, in our application we are able to provide accurate interpretations for the ingredients of LR. We apply this new technique to real-world data of a part of the German railway network of Deutsche Bahn AG. Our computational results suggest that a significant decrease of passenger delays can be obtained at a relatively small price of robustness, i.e. by increasing the nominal travel times of the passengers. 相似文献
36.
Making it easier for older people to talk to smart homes: the effect of early help prompts 总被引:1,自引:0,他引:1
K. Maria Wolters Klaus-Peter Engelbrecht Florian Gödde Sebastian Möller Anja Naumann Robert Schleicher 《Universal Access in the Information Society》2010,9(4):311-325
It is well known that help prompts shape how users talk to spoken dialogue systems. This study investigated the effect of
help prompt placement on older users’ interaction with a smart home interface. In the dynamic help condition, help was only
given in response to system errors; in the inherent help condition, it was also given at the start of each task. Fifteen older
and sixteen younger users interacted with a smart home system using two different scenarios. Each scenario consisted of several
tasks. The linguistic style users employed to communicate with the system (interaction style) was measured using the ratio of commands to the overall utterance length (keyword ratio) and the percentage of content
words in the user’s utterance that could be understood by the system (shared vocabulary). While the timing of help prompts
did not affect the interaction style of younger users, it was early task-specific help supported older users in adapting their
interaction style to the system’s capabilities. Well-placed help prompts can significantly increase the usability of spoken
dialogue systems for older people. 相似文献
37.
IntroductionAn important quality of association rules is novelty. However, evaluating rule novelty is AI-hard and has been a serious challenge for most data mining systems.ObjectiveIn this paper, we introduce functional novelty, a new non-pairwise approach to evaluating rule novelty. A functionally novel rule is interesting as it suggests previously unknown relations between user hypotheses.MethodsWe developed a novel domain-driven KDD framework for discovering functionally novel association rules. Association rules were mined from cardiovascular data sets. At post-processing, domain knowledge-compliant rules were discovered by applying semantic-based filtering based on UMLS ontology. Their knowledge compliance scores were computed against medical knowledge in Pubmed literature. A cardiologist explored possible relationships between several pairs of unknown hypotheses. The functional novelty of each rule was computed based on its likelihood to mediate these relationships.ResultsHighly interesting rules were successfully discovered. For instance, common rules such as diabetes mellitus?coronary arteriosclerosis was functionally novel as it mediated a rare association between von Willebrand factor and intracardiac thrombus.ConclusionThe proposed post-mining domain-driven rule evaluation technique and measures proved to be useful for estimating candidate functionally novel rules with the results validated by a cardiologist. 相似文献
38.
Carlos A. Jara Francisco A. Candelas Fernando Torres Sebastian Dormido Francisco Esquembre Oscar Reinoso 《Computers & Education》2009
Web-based learning environments are becoming increasingly popular in higher education. One of the most important web-learning resources is the virtual laboratory (VL), which gives students an easy way for training and learning through the Internet. Moreover, on-line collaborative communication represents a practical method to transmit the knowledge and experience from the teacher to students overcoming physical distance and isolation. Considering these facts, the authors of this document have developed a new dynamic collaborative e-learning system which combines the main advantages of virtual laboratories and collaborative learning practices. In this system, the virtual laboratories are based on Java applets which have embedded simulations developed in Easy Java Simulations (EJS), an open-source tool for teachers who do not need complex programming skills. The collaborative e-learning is based on a real-time synchronized communication among these Java applets. Therefore, this original approach provides a new tool which integrates virtual laboratories inside a synchronous collaborative e-learning framework. This paper describes the main features of this system and its successful application in a distance education environment among different universities from Spain. 相似文献
39.
Sebastian Dörn 《Information Processing Letters》2009,109(6):325-328
In this paper we give tight quantum query complexity bounds of some important linear algebra problems. We prove Θ(n2) quantum query bounds for verify the determinant, rank, matrix inverse and the matrix power problem. 相似文献
40.