全文获取类型
收费全文 | 2941篇 |
免费 | 88篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 24篇 |
化学工业 | 327篇 |
金属工艺 | 57篇 |
机械仪表 | 45篇 |
建筑科学 | 136篇 |
矿业工程 | 7篇 |
能源动力 | 113篇 |
轻工业 | 244篇 |
水利工程 | 24篇 |
石油天然气 | 11篇 |
无线电 | 245篇 |
一般工业技术 | 501篇 |
冶金工业 | 950篇 |
原子能技术 | 15篇 |
自动化技术 | 331篇 |
出版年
2021年 | 35篇 |
2020年 | 26篇 |
2019年 | 30篇 |
2018年 | 44篇 |
2017年 | 38篇 |
2016年 | 36篇 |
2015年 | 32篇 |
2014年 | 42篇 |
2013年 | 149篇 |
2012年 | 93篇 |
2011年 | 128篇 |
2010年 | 91篇 |
2009年 | 93篇 |
2008年 | 110篇 |
2007年 | 116篇 |
2006年 | 91篇 |
2005年 | 93篇 |
2004年 | 91篇 |
2003年 | 75篇 |
2002年 | 57篇 |
2001年 | 62篇 |
2000年 | 58篇 |
1999年 | 59篇 |
1998年 | 244篇 |
1997年 | 133篇 |
1996年 | 89篇 |
1995年 | 85篇 |
1994年 | 86篇 |
1993年 | 79篇 |
1992年 | 44篇 |
1991年 | 22篇 |
1990年 | 22篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 27篇 |
1986年 | 24篇 |
1985年 | 29篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1980年 | 23篇 |
1979年 | 27篇 |
1978年 | 26篇 |
1977年 | 40篇 |
1976年 | 65篇 |
1975年 | 17篇 |
1974年 | 14篇 |
1973年 | 24篇 |
1972年 | 14篇 |
排序方式: 共有3030条查询结果,搜索用时 353 毫秒
1.
Daniela Frasca Maria Romero Alain Diaz Denisse Garcia Seth Thaller Bonnie B. Blomberg 《International journal of molecular sciences》2021,22(4)
Senescent cells accumulate in the adipose tissue (AT) of individuals with obesity and secrete multiple factors that constitute the senescence-associated secretory phenotype (SASP). This paper aimed at the identification of B cells with a SASP phenotype in the AT, as compared to the peripheral blood, of individuals with obesity. Our results show increased expression of SASP markers in AT versus blood B cells, a phenotype associated with a hyper-metabolic profile necessary to support the increased immune activation of AT-derived B cells as compared to blood-derived B cells. This hyper-metabolic profile is needed for the secretion of the pro-inflammatory mediators (cytokines, chemokines, micro-RNAs) that fuel local and systemic inflammation. 相似文献
2.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
3.
Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented 相似文献
4.
S. F. Edwards 《Polymer International》1985,17(2):122-125
Elasticity is discussed as an aspect of viscoelasticity, which is described by the tube model. The effects of both crosslinks and entanglements contribute to this model and a discussion of how these effects can be quantified is given. At high enough concentration, entanglements ensure the existence of elastic effects even without crosslinks, and a theory is presented on how this dynamical phase change comes about. 相似文献
5.
Takeshi Kondo Sang Min Lee Michal Malicki Benoit Domercq Seth R. Marder Bernard Kippelen 《Advanced functional materials》2008,18(7):1112-1118
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs. 相似文献
6.
Seth Green George Turkiyyah 《International journal for numerical methods in engineering》2004,61(3):380-405
We present a new method for enforcing boundary conditions within subdivision finite element simulations of thin shells. The proposed framework is demonstrated to be second-order accurate with respect to increasing refinement in the displacement and energy norm for simply supported, clamped, free and symmetric boundary conditions. Second-order accuracy on the boundary is consistent with the accuracy of subdivision-based approaches for the interior of a body. Our proposed framework is applicable to both triangular and quadrilateral refinement schemes, and does not impose any topological requirements upon the underlying subdivision control mesh. Several examples from an obstacle course of benchmark problems are used to demonstrate the convergence of the scheme. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
7.
Lee C. Chang Ph.D. Associate Professor Director Jeri L. Edwards Senior Manager 《Computers & Industrial Engineering》1991,21(1-4):147-151
Image processing allows the automation of the business transaction, turning “paper factories” into “image factories.” This burgeoning new area of computerization needs new paradigms, theories, and methods to maximize its effectiveness at cutting time and costs. This paper investigates what this new area of computerization can gain from CIM technology. It examines the similarities between the processing of computer images in a paperless business environment and the processing of materials into products in the manufacturing plant. These similarities will allow us to apply mature, well-tested CIM techniques to emerging image factories. 相似文献
8.
Kelly Jeffrey A.; Murphy Debra A.; Sikkema Kathleen J.; Kalichman Seth C. 《Canadian Metallurgical Quarterly》1993,48(10):1023
Behavior change remains the only means for primary prevention of HIV disease. Psychology should take a leading role in efforts to curtail the epidemic, but has not contributed to HIV prevention at a level proportionate to the urgency of the crisis. The authors propose an updated agenda for behavioral research on AIDS-HIV prevention implementing accelerated community trials of promising behavior change models, conducting trials of community-level interventions on a large scale and focused on populations most vulnerable to HIV infections, establishing partnerships between HIV research and community service organizations, integrating efforts from across psychology disciplines to advance and refine HIV prevention interventions, and mobilizing interdisciplinary HIV prevention resources and communication mechanisms to rapidly translate research findings to community and public policy arenas. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
The authors highlight several possible ways in which the construction industry could lower present emissions of the greenhouse gas, carbon dioxide. It is an excellent discussion document and is recommended reading. 相似文献
10.
The optical method of caustics has been utilised to measure both the stress intensity factor for a crack lying along the interface of an aluminium/epoxy bimaterial specimen, and the mode mixity arising from the difference in the elastic properties across the interface. Measurements were carried out by using a novel modification to the method whereby caustics are produced and measured from both sides of the specimen, so compensating automatically for the distortion induced in the specimen due to misaligned loading fixtures. A flat reflective surface across the interface was obtained by adhering a reflective coating to the specimen. Verification that this coating does not affect measurement accuracy was obtained by comparing stress intensity factors measured from coated and uncoated monolithic aluminium specimens where good agreement was found to exist between both measurements. 相似文献