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51.
Jens Hauslage Medea Abbrecht Lars Hanke Ruth Hemmersbach Claudia Koch Wolfgang Hanke Florian P. M. Kohn 《Microgravity science and technology》2016,28(6):633-638
All life on earth has been established under conditions of stable gravity of 1g. Nevertheless, in numerous experiments the direct gravity dependence of biological processes has been shown on all levels of organization, from single molecules to humans. To study the effects especially of microgravity on biological systems, a variety of platforms are available, from drop towers to the ISS. Due to the costs of these platforms and their limited availability, as an alternative, numerous simulators have been developed for so called “simulated” microgravity. A classical systems is a clinostat, basically rotating a sample around one axis, and by integration of the gravity vector for 360° arguing that thus the effects of gravity are depleted. Indeed, a variety of studies has shown that taking out the direction of gravity from a biological system often results in consequences similar to the exposure of the system to real microgravity. Nevertheless, the opposite has been shown, too, and as a consequence the relevance of clinostats in microgravity research is still under discussion. To get some more insight into this problem we have constructed a small fluorescence clinostat and have studied the effects of clinorotation on the cytosolic calcium concentration of neuroglioma cells. The results have been compared to experiments with identical cells in real microgravity, utilizing parabolic flight missions. Our results show that in case of a cell suspension used in a small florescence clinostat within a tube diameter of 2mm, the effects of clinorotation are comparable to those under real microgravity, both showing a significant increase in intracellular calcium concentration. 相似文献
52.
Dr. Wolfgang Jitschin 《真空研究与实践》2016,28(5):40-42
Testing refrigerant sniffers The technical generation of coldness is typically done by machines based on a closed thermodynamic process using a refrigerant. As refrigerants usually halogenated hydrocarbons are used since these have good thermodynamic properties. Unfortunately, the halogens are harmful to the environment: They destroy the ozone layer. Therefore, the machines must be tight and must not loose the refrigerant. To check a machine for leakage, mobile leak sniffers are available which can be reliably and quantitatively controlled by test leaks. 相似文献
53.
Olivier Guillon Wolfgang Rheinheimer Martin Bram 《Advanced Engineering Materials》2023,25(18):2201870
Novel sintering methods have emerged in the recent past years, which have raised great interest in the scientific community. Relying on electric field effects, high heating rates, the use of mechanical pressure, or hydrothermal conditions, they offer fundamental advantages compared to conventional sintering routes like minimizing the energy consumption and enhancing the process efficiency. This perspective aims at explaining these effects in a general way and presenting the status quo of using them for the processing of high-performing ceramic materials. In detail, this work focuses on flash sintering, ultrafast high-temperature sintering, spark plasma sintering, cold sintering, and photonic sintering methods based on different light sources. The specificities, potentials, and limitations of each method are compared, especially in the light of a possible industrialization. 相似文献
54.
Georg Birkenheuer Andr�� Brinkmann Mikael H?gqvist Alexander Papaspyrou Bernhard Schott Dietmar Sommerfeld Wolfgang Ziegler 《Journal of Grid Computing》2011,9(3):355-377
Infrastructure federation is becoming an increasingly important issue for modern Distributed Computing Infrastructures (DCIs):
Dynamic elasticity of quasi-static Grid environments, incorporation of special-purpose resources into commoditized Cloud infrastructures,
cross-community collaboration for increasingly diverging areas of modern e-Science, and Cloud Bursting pose major challenges
on the technical level for many resource and middleware providers. Especially with respect to increasing costs of operating
data centers, the intelligent yet automated and secure sharing of resources is a key factor for success. With the D-Grid Scheduler
Interoperability (DGSI) project within the German D-Grid Initiative, we provide a strategic technology for the automatically
negotiated, SLA-secured, dynamically provisioned federation of resources and services for Grid-and Cloud-type infrastructures.
This goal is achieved by complementing current DCI schedulers with the ability to federate infrastructure for the temporary
leasing of resources and rechanneling of workloads. In this work, we describe the overall architecture and SLA-secured negotiation
protocols within DGSI and depict an advanced mechanism for resource delegation through means of dynamically provisioned, virtualized
middleware. Through this methodology, we provide the technological foundation for intelligent capacity planning and workload
management in a cross-infrastructure fashion. 相似文献
55.
Mike Espig Wolfgang Hackbusch Stefan Handschuh Reinhold Schneider 《Computing and Visualization in Science》2011,14(6):271-285
We discuss the calculus of variations in tensor representations with a special focus on tensor networks and apply it to functionals of practical interest. The survey provides all necessary ingredients for applying minimization methods in a general setting. The important cases of target functionals which are linear and quadratic with respect to the tensor product are discussed, and combinations of these functionals are presented in detail. As an example, we consider the representation rank compression in tensor networks. For the numerical treatment, we use the nonlinear block Gauss?CSeidel method. We demonstrate the rate of convergence in numerical tests. 相似文献
56.
In interactive theorem proving practice a significant amount of time is spent on unsuccessful proof attempts of wrong conjectures.
An automatic method that reveals them by generating finite counter examples would offer an extremely valuable support for
a proof engineer by saving his time and effort. In practice, such counter examples tend to be small, so usually there is no
need to search for big instances. Most definitions of functions or predicates on infinite structures do not preserve the semantics
if a transition to arbitrary finite substructures is made. We propose constraints which guarantee a correct axiomatization
on finite structures and present an approach which uses the Alloy Analyzer to generate finite instances of theories in the
theorem prover KIV. It is evaluated on the library of basic data types as well as on some challenging case studies in KIV.
The technique is implemented using the Kodkod constraint solver which is a successor of Alloy. 相似文献
57.
Epoxy resin based negative photo resists are showing interesting properties which are useful for a series of applications in electronic industries (Mark et al. in Encyclopedia of polymer science and engineering, Wiley, New York, 1986; Potter in Epoxide resins, Springer, New York, 1970; May and Tanka in Epoxy resin chemistry and technology, Marcel Dekker, New York, 1973; Bauer in Epoxy resin chemistry, vol 114, American Chemical Society, Washington, 1979; Hood in RAPRA Rev Rep 38:4, 1990). Especially in micro system technologies they promise a high potential. To adjust the properties for the particular application modification of the chemical composition and crosslinker system must be performed. An actual problem is the constancy in behaviour during the LIGA-process of the resist mixture. In this work analytical techniques are used to get a detailed insight into the chemical composition of a commercial available epoxy novolac resin. Methods like size exclusion chromatography (SEC), matrix assisted laser desorption-time of flight (MALDI-ToF) and fourier transform infrared spectroscopy (FTIR) offer information about the molecular weight and functionality. The results reveal a distribution in molecular weight and functionality. Due this the resin was chemically modified. After processing a dependency of molecular weight and therefore the amount of epoxy groups existent was obtained. 相似文献
58.
Wolfgang Däubler 《Datenschutz und Datensicherheit - DuD》2010,34(1):20-24
Der betriebliche Datenschutzbeauftragte dient der Selbstkontrolle der verantwortlichen Stelle. Wirksam ist solch eine Selbstkontrolle
aber nur dann, wenn der Datenschutzbeauftragte auch Unabh?gigkeit genie?t. Welche Voraussetzungen hierfür erfüllt sein müssen,
erl?utert der folgende Beitrag. 相似文献
59.
A two-layer architecture for dynamic real-time optimization (or nonlinear modelpredictive control (NMPC) with an economic objective) is presented, where the solution of the dynamic optimization problem is computed on two time-scales. On the upper layer, a rigorous optimization problem is solved with an economic objective function at a slow time-scale, which captures slow trends in process uncertainties. On the lower layer, a fast neighboring-extremal controller is tracking the trajectory in order to deal with fast disturbances acting on the process. Compared to a single-layer architecture, the two-layer architecture is able to address control systems with complex models leading to high computational load, since the rigorous optimization problem can be solved at a slower rate than the process sampling time. Furthermore, solving a new rigorous optimization problem is not necessary at each sampling time if the process has rather slow dynamics compared to the disturbance dynamics. The two-layer control strategy is illustrated with a simulated case study of an industrial polymerization process. 相似文献
60.
Kirsten Berthold Heidi RöderDaniel Knörzer Wolfgang KesslerAlexander Renkl 《Computers in human behavior》2011,27(1):69-75
Explanation prompts usually foster conceptual understanding. However, it has been claimed within cognitive load theory that prompts can take cognitive load to the upper limit when learning complex contents. Under such circumstances, prompts focusing the learners’ attention on specific aspects (e.g., conceptual aspects such as elaborations on domain principles) might have some costs: Other important aspects (e.g., procedural aspects such as how to calculate) cannot be processed deeply. Thus, we expected that conceptually-oriented explanation prompts would foster the detailedness of explanations, the number of elaborations on domain principles, and conceptual knowledge. In addition, we tested the influence of such prompts on the number of calculations performed during learning and procedural knowledge. We conducted an experiment in which we employed conceptually-oriented explanation prompts in a complex e-learning module on tax law. Tax law university students (N = 40) worked on this e-learning module under two conditions: (a) conceptually-oriented explanation prompts, (b) no prompts. The prompts led to double-edged effects: positive effects on the detailedness of explanations and on the number of elaborations on domain principles, as well as on conceptual knowledge and simultaneously negative effects on the number of calculations performed during learning as well as on procedural knowledge. 相似文献