全文获取类型
收费全文 | 1325篇 |
免费 | 51篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 269篇 |
金属工艺 | 55篇 |
机械仪表 | 35篇 |
建筑科学 | 108篇 |
矿业工程 | 2篇 |
能源动力 | 66篇 |
轻工业 | 193篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 61篇 |
一般工业技术 | 272篇 |
冶金工业 | 67篇 |
原子能技术 | 20篇 |
自动化技术 | 207篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 17篇 |
2017年 | 32篇 |
2016年 | 28篇 |
2015年 | 27篇 |
2014年 | 38篇 |
2013年 | 79篇 |
2012年 | 58篇 |
2011年 | 99篇 |
2010年 | 61篇 |
2009年 | 76篇 |
2008年 | 88篇 |
2007年 | 83篇 |
2006年 | 55篇 |
2005年 | 54篇 |
2004年 | 51篇 |
2003年 | 43篇 |
2002年 | 45篇 |
2001年 | 26篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 32篇 |
1997年 | 25篇 |
1996年 | 21篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1973年 | 3篇 |
1972年 | 4篇 |
排序方式: 共有1378条查询结果,搜索用时 15 毫秒
1.
Dr. Li Di Prof. Per Artursson Dr. Alex Avdeef Prof. Leslie Z. Benet Prof. J. Brian Houston Dr. Manfred Kansy Edward H. Kerns Prof. Hans Lennernäs Dr. Dennis A. Smith Prof. Kiyohiko Sugano 《ChemMedChem》2020,15(20):1862-1874
Passive permeability is a key property in drug disposition and delivery. It is critical for gastrointestinal absorption, brain penetration, renal reabsorption, defining clearance mechanisms and drug-drug interactions. Passive diffusion rate is translatable across tissues and animal species, while the extent of absorption is dependent on drug properties, as well as in vivo physiology/pathophysiology. Design principles have been developed to guide medicinal chemistry to enhance absorption, which combine the balance of aqueous solubility, permeability and the sometimes unfavorable compound characteristic demanded by the target. Permeability assays have been implemented that enable rapid development of structure-permeability relationships for absorption improvement. Future advances in assay development to reduce nonspecific binding and improve mass balance will enable more accurately measurement of passive permeability. Design principles that integrate potency, selectivity, passive permeability and other ADMET properties facilitate rapid advancement of successful drug candidates to patients. 相似文献
2.
Per Johan Råsmark Čestmír Koňák Petr Štěpánek Christer Elvingson 《Polymer Bulletin》2005,54(4-5):335-342
Summary Dynamic light scattering was used to investigate the dynamics of sodium poly(styrene sulfonate) and fully neutralized poly(acrylic acid) gels as a function of the degree of swelling and weight ratio of cross-linking agent. It was shown that the collective diffusion coefficient increases with increasing degree of swelling and that the diffusion coefficient shows stronger concentration dependence than predicted by scaling arguments. For gel samples measured at the swelling equilibrium, the diffusion coefficient increases with increasing gel concentration for both gel systems. 相似文献
3.
Henrik Pettersson Tadeusz Gruszecki Lars-Henrik Johansson Per Johander 《Solar Energy Materials & Solar Cells》2003,77(4):6595
A manufacturing technique for monolithic dye-sensitised solar cells is presented. Encapsulated modules designed for indoor low-power applications have been prepared using industrial methods and equipment. Under certain conditions (light intensity <5000 lx, temperature between –10°C and 50°C, and relative humidity of appr. 50%), the modules have performed well and shown excellent long-term stability. Moreover, modules withstand illumination in combination with storage at 100% relative humidity. However, a certain degradation of the module performance takes place at illuminations exceeding 5000 lx and temperatures exceeding 50°C. 相似文献
4.
Per Hovstad Liching Sung 《International Journal of Satellite Communications and Networking》2005,23(2):91-110
The 1977 Broadcasting‐Satellite Service (BSS) Plan for Region 1 & 3 had been widely acknowledged to be out‐of‐date by the late 1980s. Development of digital modulation in the early 1990s provided an opportunity to update the technical provisions of the Plan to make it more economically viable. After a decade of work and three World Radiocommunication Conferences (WRCs), the revision of Region 1 & 3 BSS Plan was finally completed in 2003. The new Plan increased channel assignments from 5 to 10 analog‐equivalent channels for each country in Region 1, and from 4 to 12 channels for each country in Region 3. Yet, despite the increase in capacity, the new Plan is surprisingly similar to the original one in terms of the technical parameters. It is still based on national coverage, and the channel plan, orbital location, orbital spacing, and polarization are also the same. As a result, the new Plan is no more economically viable to implement than the old. To create economically viable BSS systems would most likely require modifications to the assignment in the Plan. Yet, modification procedures were made more difficult to apply after replanning. Less future implementation of BSS networks than would otherwise have occurred can be expected, and an inefficient usage of these frequency bands will likely result. On the other hand, less implemented systems will mean more capacity set aside for future use. This is important for countries that currently do not have satellite operations. In the end, BSS replanning reflects the eternal conflict between efficient usage and guaranteed future access. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
5.
New CAMAC based data acquisition and beam control system for Lund nuclear microprobe 总被引:1,自引:0,他引:1
Mikael Elfman Per Kristiansson Klas Malmqvist Jan Pallon Anders Sjland Rogerio Utui Changyi Yang 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1997,130(1-4):123-126
A new CAMAC based data acquisition system has been installed at the Lund Nuclear Microprobe facility. This paper reports on the development and present status of the data acquisition system. The system is a true multiparameter CAMAC based system with fast Fera bus readout and in crate memory buffer. The user interface is based on Sparrow Kmax software for a Power Macintosh platform. The system read out and tag the event data with position on-line, which make fast on-line monitoring of spectra or element maps possible.Simultaneously, all data can be saved event by event for off-line analysis. The beam scanning part is software controlled through a timed D/A converter, this allows fast scanning of the beam. With a CCD-camera and video card the area to be analysed could be defined directly from the image, and the sample position can be moved. Any kind of irregular scan patterns could be defined. 相似文献
6.
T. Jing M. Sc. Ir. P. H. F. Moshuis Prof. Dr. Ir. F. H. Kreuger 《Electrical Engineering (Archiv fur Elektrotechnik)》1991,74(4):315-319
Contents Surface charge accumulation and its decay at a GIS spacer are studied at atmospheric conditions employing a two step-calibration method. The results show that the accumulation saturates within 30 minutes; the dominant mechanism of surface charge accumulation is the drift of charged particles via air, while that of the decay is surface conduction. The characteristics are similar at both polarities.
Sättigungskonzentration und Abklingverhalten der Oberflächenladung an einem mit Gleichspannung beanspruchten Abstandshalter unter atmosphärischen Bedingungen
Übersicht Die Konzentration und das Abklingen von Oberflächenladungen an einem GIS Abstandshalter wurden unter atmosphärischen Bedingungen mit Hilfe eines zweistufigen Kalibrierungsverfahrens untersucht. Die Ergebnisse zeigen eine Sättigung der Ladungskonzentration innerhalb von 30 Minuten. Als Hauptursache der Ladungskonzentration ist die Drift geladener Teilchen in Luft anzusehen, während das Abklingen auf die Oberflächenleitung zurückzuführen ist. Ähnliche Charakteristiken ergeben sich mit beiden Polaritäten.相似文献
7.
Per Gustafson 《Metallurgical and Materials Transactions A》1988,19(10):2547-2554
A thermodynamic evaluation of the C-Cr-Fe-W system has been made using a multi-sublattice model. A set of parameter values
describing the Gibbs energy of each individual phase is given and a number of calculated sections of the C-Cr-Fe-W phase diagram
are presented and compared with experimental data.
Formerly with the Division of Physical Metallurgy, Royal Institute of Technology, Stockholm, Sweden 相似文献
8.
Per Munk Nielsen Jesper Brask Lene Fjerbaek 《European Journal of Lipid Science and Technology》2008,110(8):692-700
It is well documented in the literature that enzymatic processing of oils and fats for biodiesel is technically feasible. However, with very few exceptions, enzyme technology is not currently used in commercial‐scale biodiesel production. This is mainly due to non‐optimized process design and a lack of available cost‐effective enzymes. The technology to re‐use enzymes has typically proven insufficient for the processes to be competitive. However, literature data documenting the productivity of enzymatic biodiesel together with the development of new immobilization technology indicates that enzyme catalysts can become cost effective compared to chemical processing. This work reviews the enzymatic processing of oils and fats into biodiesel with focus on process design and economy. 相似文献
9.
Per Axel Clausen 《Indoor air》1993,3(4):269-275
A waterborne paint was applied to tin plated steel sheets with three different film thicknesses. The emission of volatile and semivolaile organic compounds ((S) VOCs) from the samples was measured in small climatic chambers under standard conditions over a two-week period. The purpose of the study was to evaluate the effect of the film thickness on the emission rate decay. First order decay models, including sink effects for the high boiling (S) VOCs, were fitted to the concentration versus time data. The results showed that the first order rate constants decrease with increasing film thickness. In uddition, the results indicated that the emissions of the (S)VOCs in the waterborne paint film seemed to be controlled by evaporation. The thicknesses of paint films used in climatic chamber tests to estimate emission rates for product compurison or emission prediction must be known in order to prevent erroneous conclusions 相似文献
10.
An overall model for maintenance optimization 总被引:1,自引:0,他引:1
This paper presents an approach for identifying the optimal maintenance schedule for the components of a production system. Safety, health and environment objectives, maintenance costs and costs of lost production are all taken into consideration, and maintenance is thus optimized with respect to multiple objectives. Such a global approach to maintenance optimization requires expertise from various fields, e.g., decision theory, risk analysis and reliability and maintenance modelling. Further, a close co-operation between management, maintenance personnel and analysts is required to achieve a successful result. In the past this has been a major obstacle to the extensive use of proper maintenance optimization methods in practice, and techniques to promote the communication between the involved parties of the optimization process is an essential element in the suggested approach. A simple step by step presentation of the required modelling is provided. Contrary to most current methods of RCM (Reliability Centered Maintenance), the approach is based on an analytic model, and therefore gives a sound framework for carrying out a proper maintenance optimization. The approach is also flexible as it can be carried out at various levels of detail, e.g., adopted to available resources and to the managements willingness to give detailed priorities with respect to objectives on safety vs production loss. 相似文献