全文获取类型
收费全文 | 9801篇 |
免费 | 537篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 128篇 |
综合类 | 8篇 |
化学工业 | 2096篇 |
金属工艺 | 201篇 |
机械仪表 | 175篇 |
建筑科学 | 458篇 |
矿业工程 | 10篇 |
能源动力 | 360篇 |
轻工业 | 828篇 |
水利工程 | 69篇 |
石油天然气 | 25篇 |
无线电 | 822篇 |
一般工业技术 | 1991篇 |
冶金工业 | 1458篇 |
原子能技术 | 75篇 |
自动化技术 | 1653篇 |
出版年
2023年 | 120篇 |
2022年 | 174篇 |
2021年 | 314篇 |
2020年 | 214篇 |
2019年 | 232篇 |
2018年 | 274篇 |
2017年 | 243篇 |
2016年 | 294篇 |
2015年 | 264篇 |
2014年 | 374篇 |
2013年 | 596篇 |
2012年 | 576篇 |
2011年 | 716篇 |
2010年 | 539篇 |
2009年 | 512篇 |
2008年 | 509篇 |
2007年 | 456篇 |
2006年 | 406篇 |
2005年 | 326篇 |
2004年 | 305篇 |
2003年 | 236篇 |
2002年 | 230篇 |
2001年 | 114篇 |
2000年 | 139篇 |
1999年 | 140篇 |
1998年 | 259篇 |
1997年 | 166篇 |
1996年 | 139篇 |
1995年 | 108篇 |
1994年 | 105篇 |
1993年 | 90篇 |
1992年 | 62篇 |
1991年 | 55篇 |
1990年 | 66篇 |
1989年 | 71篇 |
1988年 | 51篇 |
1987年 | 65篇 |
1986年 | 43篇 |
1985年 | 56篇 |
1984年 | 58篇 |
1983年 | 47篇 |
1982年 | 48篇 |
1981年 | 51篇 |
1980年 | 33篇 |
1979年 | 52篇 |
1978年 | 38篇 |
1977年 | 46篇 |
1976年 | 58篇 |
1974年 | 32篇 |
1973年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
91.
Benjamin F. Myers 《Journal of the American Ceramic Society》1992,75(3):686-693
The hydrolysis of uranium oxycarbide (UCO) was studied by injecting water vapor into a fuel element containing a known number of high-temperature, gas-cooled reactor (HTGR) coated particles with exposed fuel kernels. The experiments were conducted in the High Flux Isotope Reactor (HFIR) at temperatures between 700° and 1000°C, a system pressure of 200 kPa, and partial pressures of water vapor between 21 and 199 Pa. The general sequential response of the exposed fuel kernels to water vapor addition consisted of (1) a rapid release of stored fission gas with a concomitant increase in the steady-state release and (2) a period of constant steady-state release. Upon cessation of the addition of water vapor, a decline in the release to prehydrolysis values generally occurred. The release of stored fission gas was dependent on the square of the partial pressure of water vapor. The ratio of the constant steady-state release to the prehydrolysis value was independent of the partial pressure of water vapor. The time constant for the decline in the release was the same in all of the hydrolysis tests. 相似文献
92.
The application of conventional observer designs for high-dimensional systems may not always be practical due to high computational requirements or the resulting observers being too sensitive to measurement noise. In order to address these issues, this paper presents two observer design techniques for state estimation of high-dimensional chemical processes. One technique is used for systems with inputs, whereas the other one is specifically geared towards systems that are not excited from the outside. Both of these observers are applicable to linear and with a modification to non-linear systems.The main idea behind the presented observer designs is that a reduced-order observer is implemented instead of a conventional state estimator. The motivation is that subspaces, which are close to being unobservable, cannot be correctly reconstructed in a realistic setting due to measurement noise and inaccuracies in the model. The presented approaches make use of this observation and only reconstruct the parts of the system where accurate state estimation is possible. The observer designs are illustrated on a 30-tray distillation column model. Additionally, it has been shown that the location of process measurements has a major effect on the performance of the presented reduced-order observers. 相似文献
93.
We analyze the classic board game of Mastermind with n holes and a constant number of colors. The classic result of Chvátal (Combinatorica 3:325–329, 1983) states that the codebreaker can find the secret code with Θ(n/logn) questions. We show that this bound remains valid if the codebreaker may only store a constant number of guesses and answers. In addition to an intrinsic interest in this question, our result also disproves a conjecture of Droste, Jansen, and Wegener (Theory Comput. Syst. 39:525–544, 2006) on the memory-restricted black-box complexity of the OneMax function class. 相似文献
94.
Benjamin Zeiss Andras Kovacs Nikolay Pakulin Bogdan Stanca-Kaposta 《International Journal on Software Tools for Technology Transfer (STTT)》2014,16(3):285-294
With more than 10 years of maturing through industrial use and standardization, the Testing and Test Control Notation (TTCN-3) has become a widely used technology that many businesses depend upon for ensuring their product quality. With the rising number of supporters and tools, the demand for a means to assess the standards compliance of TTCN-3 tools has increased. In this article, we describe the motivation, approach, methodology, and results of the still ongoing project to develop a standardized conformance test suite for TTCN-3 tools. We discuss the challenges involved in creating such a test suite, the way to deal with imposed resource limitations of the project, and where we think the effort is heading. 相似文献
95.
Adam Bates Benjamin Mood Joe Pletcher Hannah Pruse Masoud Valafar Kevin Butler 《International Journal of Information Security》2014,13(2):171-189
Virtualization is the cornerstone of the developing third-party compute industry, allowing cloud providers to instantiate multiple virtual machines (VMs) on a single set of physical resources. Customers utilize cloud resources alongside unknown and untrusted parties, creating the co-resident threat—unless perfect isolation is provided by the virtual hypervisor, there exists the possibility for unauthorized access to sensitive customer information through the exploitation of covert side channels. This paper presents co-resident watermarking, a traffic analysis attack that allows a malicious co-resident VM to inject a watermark signature into the network flow of a target instance. This watermark can be used to exfiltrate and broadcast co-residency data from the physical machine, compromising isolation without reliance on internal side channels. As a result, our approach is difficult to defend against without costly underutilization of the physical machine. We evaluate co-resident watermarkingunder a large variety of conditions, system loads and hardware configurations, from a local laboratory environment to production cloud environments (Futuregrid and the University of Oregon’s ACISS). We demonstrate the ability to initiate a covert channel of 4 bits per second, and we can confirm co-residency with a target VM instance in $<$ 10 s. We also show that passive load measurement of the target and subsequent behavior profiling is possible with this attack. We go on to consider the detectability of co-resident watermarking, extending our scheme to create a subtler watermarking attack by imitating legitimate cloud customer behavior. Our investigation demonstrates the need for the careful design of hardware to be used in the cloud. 相似文献
96.
Vapor-liquid equilibrium compositions have been measured for the argon-methane system at 115.2°, 123.4° and 137.1°K, by means of a forced-recirculation apparatus. A modified Redlich-Kwong equation of state with the incorporation of a binary interaction constant has been successfully employed to represent the data. Liquid activity coefficients have been evaluated and correlated. 相似文献
97.
Benjamin S. Sparrow 《Desalination》2003,159(2):161-170
Equations for the thermodynamic properties of aqueous sodium chloride near its vapour pressure are presented. The equations are functions of temperature and concentration, and may be used to estimate aqueous sodium chloride's solubility, density, vapour pressure, specific enthalpy and entropy. They are valid for temperatures from 0 to 300°C, and concentrations extending to saturation with suitable accuracy. The thermodynamic equations are represented graphically and compared with published experimental data. These equations should prove to be a useful tool for modeling desalination equipment, particularly distillation processes. 相似文献
98.
The acoustic emission behavior during tensile loading of two common epoxy systems of different ductility was investigated at different loading rates. At low threshold voltage, it was possible to register acoustic emissions before the final failure. Only very few emissions were recorded compared with the amount commonly recorded for metals and composite materials. The acoustic emissions detected were of burst-type, revealing a brittle damage accumulation process. They originated from the initiation and incremental growth of microcracks of stochastic nature. The events occurred before gross yielding and during the final “brittle” failure process. Basically no events were detected between gross yielding and the final failure during which large scale yielding, necking, and stable crack growth took place. The occurrence of events at the different loading rates was strongly influenced by the yielding behavior and fracture toughness, characterized by the yield stress σy and the plane-strain fracture toughness KIc respectively. KIc was inversely dependent on the total number of events up to gross yielding. The event distribution normalized with respect to the conditions at gross yielding was hardly affected by the loading rate. 相似文献
99.
Laurence J. Hardwick Matthias Hahn Michael Holzapfel Hilmi Buqa Petr Novák 《Electrochimica acta》2006,52(2):675-680
An initial Raman study on the effects of intercalation for aprotic electrolyte-based electrochemical double-layer capacitors (EDLCs) is reported. In situ Raman microscopy is employed in the study of the electrochemical intercalation of tetraethylammonium (Et4N+) and tetrafluoroborate (BF4−) into and out of microcrystalline graphite. During cyclic voltammetry experiments, the insertion of Et4N+ into graphite for the negative electrode occurs at an onset potential of +1.0 V versus Li/Li+. For the positive electrode, BF4− was shown to intercalate above +4.3 V versus Li/Li+. The characteristic G-band doublet peak (E2g2(i) (1578 cm−1) and E2g2(b) (1600 cm−1)) showed that various staged compounds were formed in both cases and the return of the single G-band (1578 cm−1) demonstrates that intercalation was fully reversible. The disappearance of the D-band (1329 cm−1) in intercalated graphite is also noted and when the intercalant is removed a more intense D-band reappears, indicating possible lattice damage. For cation intercalation, such irreversible changes of the graphite structure are confirmed by scanning electron microscopy (SEM). 相似文献
100.
Using atomic force spectroscopy, we investigated the adhesion-promoting ability of chromium. An intermediate layer of chromium can overcome the low adhesion between metal films and silicon dioxide. For the first time, we quantitatively studied this experimentally well known fact. We compared the adhesion between chromium and different substrates such as gold, silver, mica, and silicon dioxide and, beyond that, the adhesion between silicon dioxide and the same substrates. To avoid additional effects due to water, we chose ethanol as a nonpolar solvent. Taking the interfacial energies of the surfaces with the liquid into account eliminates the direct influence of the fluid medium on the adhesion of the solid material. The results we obtained corroborate the experimental fact of higher adhesion of chromium with the chosen substrates, as well as substantiate the value of chromium as an adhesion promoter. The adhesion of chromium-coated probes on gold, silicon dioxide, and mica is higher than the adhesion of silicon dioxide probes on the same substrates. 相似文献