全文获取类型
收费全文 | 9141篇 |
免费 | 554篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 127篇 |
综合类 | 18篇 |
化学工业 | 2350篇 |
金属工艺 | 174篇 |
机械仪表 | 208篇 |
建筑科学 | 325篇 |
矿业工程 | 36篇 |
能源动力 | 225篇 |
轻工业 | 421篇 |
水利工程 | 68篇 |
石油天然气 | 28篇 |
无线电 | 761篇 |
一般工业技术 | 2302篇 |
冶金工业 | 992篇 |
原子能技术 | 86篇 |
自动化技术 | 1595篇 |
出版年
2023年 | 153篇 |
2022年 | 377篇 |
2021年 | 418篇 |
2020年 | 285篇 |
2019年 | 247篇 |
2018年 | 303篇 |
2017年 | 258篇 |
2016年 | 349篇 |
2015年 | 299篇 |
2014年 | 440篇 |
2013年 | 555篇 |
2012年 | 550篇 |
2011年 | 627篇 |
2010年 | 425篇 |
2009年 | 414篇 |
2008年 | 439篇 |
2007年 | 418篇 |
2006年 | 325篇 |
2005年 | 254篇 |
2004年 | 224篇 |
2003年 | 203篇 |
2002年 | 191篇 |
2001年 | 123篇 |
2000年 | 115篇 |
1999年 | 121篇 |
1998年 | 198篇 |
1997年 | 158篇 |
1996年 | 107篇 |
1995年 | 83篇 |
1994年 | 75篇 |
1993年 | 93篇 |
1992年 | 53篇 |
1991年 | 50篇 |
1990年 | 51篇 |
1989年 | 37篇 |
1988年 | 44篇 |
1987年 | 40篇 |
1986年 | 35篇 |
1985年 | 43篇 |
1984年 | 37篇 |
1983年 | 34篇 |
1982年 | 29篇 |
1981年 | 28篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 28篇 |
1977年 | 25篇 |
1976年 | 61篇 |
1975年 | 28篇 |
1971年 | 17篇 |
排序方式: 共有9716条查询结果,搜索用时 15 毫秒
71.
Achim Streit Piotr Bala Alexander Beck-Ratzka Krzysztof Benedyczak Sandra Bergmann Rebecca Breu Jason Milad Daivandy Bastian Demuth Anastasia Eifer André Giesler Björn Hagemeier Sonja Holl Valentina Huber Nadine Lamla Daniel Mallmann Ahmed Shiraz Memon Mohammad Shahbaz Memon Michael Rambadt Morris Riedel Mathilde Romberg Bernd Schuller Tobias Schlauch Andreas Schreiber Thomas Soddemann Wolfgang Ziegler 《电信纪事》2010,65(11-12):757-762
UNICORE is a European Grid Technology with more than 10 years of history. Originating from the Supercomputing domain, the latest version UNICORE 6 has turned into a general-purpose Grid technology that follows established standards and offers a rich set of features to its users. The paper starts with an architectural insight into UNICORE 6, highlighting the workflow features, standards and the different clients. Next, the current state of advancement is presented by describing recent developments. The paper closes with an outlook on future planned developments. 相似文献
72.
73.
Harvesting Lost Photons: Plasmon and Upconversion Enhanced Broadband Photocatalytic Activity in Core@Shell Microspheres Based on Lanthanide‐Doped NaYF4, TiO2, and Au 下载免费PDF全文
Zhenhe Xu Marta Quintanilla Fiorenzo Vetrone Alexander O. Govorov Mohamed Chaker Dongling Ma 《Advanced functional materials》2015,25(20):2950-2960
Efficiently harvesting solar energy for photocatalysis remains very challenging. Rational design of architectures by combining nanocomponents of radically different properties, for example, plasmonic, upconversion, and photocatalytic properties, offers a promising route to improve solar energy utilization. Herein, the synthesis of novel, plasmonic Au nanoparticle decorated NaYF4:Yb3+, Er3+, Tm3+‐core@porous‐TiO2‐shell microspheres is reported. They exhibit high surface area, good stability, broadband absorption from ultraviolet to near infrared, and excellent photocatalytic activity, significantly better than the benchmark P25 TiO2. The enhanced activity is attributed to synergistic effects from nanocomponents arranged into the nanostructured architecture in such a way that favors the efficient charge/energy transfer among nanocomponents and largely reduced charge recombination. Optical and energy‐transfer properties are modeled theoretically to support our interpretations of catalytic mechanisms. In addition to yielding novel materials and interesting properties, the current work provides physical insights that can contribute to the future development of plasmon‐enhanced broadband catalysts. 相似文献
74.
Alexander J.A.M. van Deursen Jan A.G.M. van Dijk Peter M. ten Klooster 《Telematics and Informatics》2015
We investigate types of Internet activities among a representative sample of the Dutch population from 2010 to 2013. We examined usage patterns of seven types of Internet activities (i.e., information, news, personal development, commercial transaction, social interaction, leisure, and gaming) and related these patterns with gender, age, education, and income. Activities related to news, personal development, commercial transaction, and social interaction increased in popularity. For most capital enhancing activities, men, younger people, higher educated people, and people with higher than average incomes were prominent. These observations, however, are subject to change. The Internet seems to provide increasingly more capital-enhancing opportunities for those with higher education and income, which would accordingly reinforce their already strong positions in society. 相似文献
75.
76.
Do‐Yeon Kim Suman Sinha‐Ray Jung‐Jae Park Jong‐Gun Lee You‐Hong Cha Sang‐Hoon Bae Jong‐Hyun Ahn Yong Chae Jung Soo Min Kim Alexander L. Yarin Sam S. Yoon 《Advanced functional materials》2014,24(31):4986-4995
The industrial scale application of graphene and other functional materials in the field of electronics has been limited by inherent defects, and the lack of simple deposition methods. A simple spray deposition method is developed that uses a supersonic air jet for a commercially available reduced graphene oxide (r‐GO) suspension. The r‐GO flakes are used as received, which are pre‐annealed and pre‐hydrazine‐treated, and do not undergo any post‐treatment. A part of the considerable kinetic energy of the r‐GO flakes entrained by the supersonic jet is used in stretching the flakes upon impact with the substrate. The resulting “frozen elastic strains” heal the defects (topological defects, namely Stone‐Wales defect and C2 vacancies) in the r‐GO flakes, which is reflected in the reduced ratio of the intensities of the D and G bands in the deposited film. The defects can also be regenerated by annealing. 相似文献
77.
78.
Alexander Aleksandrov Elena Aleksandrova Alexey Zhabko 《Circuits, Systems, and Signal Processing》2016,35(10):3531-3554
This paper examines certain classes of multiconnected (complex) systems with time-varying delay. Delay-independent stability conditions and estimates of the convergence rate of solutions to the origin for those systems are derived. It is shown that the exponents in the obtained estimates depend on the parameters of Lyapunov functions constructed for the corresponding isolated subsystems. The problem of computing parameter values that provide the most precise estimates is investigated. Some examples are presented to demonstrate the effectiveness of the proposed approaches. 相似文献
79.
Valery D. Rumyantsev Alexander V. Chekalin Nikolay Yu. Davidyuk Nikolay A. Sadchikov Antonio Luque 《Progress in Photovoltaics: Research and Applications》2016,24(2):211-218
A method for the evaluation of p–n junction cell temperature in PV modules operating in the maximum power point (MPP) mode has been proposed. The method does not require specialized equipment and (for the concentrator modules) the data on the open circuit (OC) voltage temperature coefficients measured under pulse illumination. It consists of measuring several open circuit voltage magnitudes together with temperature measurements on the external module surface near one of the cells. In this procedure, a fast transition from MPP to OC operational mode is carried out, during which a time‐dependent voltage measurement is carried out with the help of a memory oscilloscope. A “reference” OC voltage magnitude in a “cold” module (a condition, as if the cells are kept at ambient temperature) is obtained by calculations, so that there is no necessity in a fast mechanical shuttering of the module aperture area. In the case of the concentrator modules, the module OC voltage temperature coefficient can be measured, if heat sinking process is artificially modified during outdoor measurements. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
80.
Veress AI Segars WP Weiss JA Tsui BM Gullberg GT 《IEEE transactions on medical imaging》2006,25(12):1604-1616
The four-dimensional (4-D) NURBS-based cardiac-torso (NCAT) phantom, which provides a realistic model of the normal human anatomy and cardiac and respiratory motions, is used in medical imaging research to evaluate and improve imaging devices and techniques, especially dynamic cardiac applications. One limitation of the phantom is that it lacks the ability to accurately simulate altered functions of the heart that result from cardiac pathologies such as coronary artery disease (CAD). The goal of this work was to enhance the 4-D NCAT phantom by incorporating a physiologically based, finite-element (FE) mechanical model of the left ventricle (LV) to simulate both normal and abnormal cardiac motions. The geometry of the FE mechanical model was based on gated high-resolution X-ray multislice computed tomography (MSCT) data of a healthy male subject. The myocardial wall was represented as a transversely isotropic hyperelastic material, with the fiber angle varying from -90 degrees at the epicardial surface, through 0 degrees at the midwall, to 90 degrees at the endocardial surface. A time-varying elastance model was used to simulate fiber contraction, and physiological intraventricular systolic pressure-time curves were applied to simulate the cardiac motion over the entire cardiac cycle. To demonstrate the ability of the FE mechanical model to accurately simulate the normal cardiac motion as well as the abnormal motions indicative of CAD, a normal case and two pathologic cases were simulated and analyzed. In the first pathologic model, a subendocardial anterior ischemic region was defined. A second model was created with a transmural ischemic region defined in the same location. The FE-based deformations were incorporated into the 4-D NCAT cardiac model through the control points that define the cardiac structures in the phantom which were set to move according to the predictions of the mechanical model. A simulation study was performed using the FE-NCAT combination to investigate how the differences in contractile function between the subendocardial and transmural infarcts manifest themselves in myocardial Single photon emission computed tomography (SPECT) images. The normal FE model produced strain distributions that were consistent with those reported in the literature and a motion consistent with that defined in the normal 4-D NCAT beating heart model based on tagged magnetic resonance imaging (MRI) data. The addition of a subendocardial ischemic region changed the average transmural circumferential strain from a contractile value of -0.09 to a tensile value of 0.02. The addition of a transmural ischemic region changed average circumferential strain to a value of 0.13, which is consistent with data reported in the literature. Model results demonstrated differences in contractile function between subendocardial and transmural infarcts and how these differences in function are documented in simulated myocardial SPECT images produced using the 4-D NCAT phantom. Compared with the original NCAT beating heart model, the FE mechanical model produced a more accurate simulation for the cardiac motion abnormalities. Such a model, when incorporated into the 4-D NCAT phantom, has great potential for use in cardiac imaging research. With its enhanced physiologically based cardiac model, the 4-D NCAT phantom can be used to simulate realistic, predictive imaging data of a patient population with varying whole-body anatomy and with varying healthy and diseased states of the heart that will provide a known truth from which to evaluate and improve existing and emerging 4-D imaging techniques used in the diagnosis of cardiac disease. 相似文献