全文获取类型
收费全文 | 710篇 |
免费 | 40篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 270篇 |
金属工艺 | 6篇 |
机械仪表 | 14篇 |
建筑科学 | 11篇 |
矿业工程 | 2篇 |
能源动力 | 24篇 |
轻工业 | 77篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 41篇 |
一般工业技术 | 170篇 |
冶金工业 | 5篇 |
原子能技术 | 13篇 |
自动化技术 | 95篇 |
出版年
2023年 | 13篇 |
2022年 | 30篇 |
2021年 | 23篇 |
2020年 | 11篇 |
2019年 | 17篇 |
2018年 | 22篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 32篇 |
2012年 | 62篇 |
2011年 | 49篇 |
2010年 | 36篇 |
2009年 | 45篇 |
2008年 | 45篇 |
2007年 | 40篇 |
2006年 | 33篇 |
2005年 | 20篇 |
2004年 | 17篇 |
2003年 | 18篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 3篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1964年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有750条查询结果,搜索用时 9 毫秒
31.
Ranjana Rai Marwa TallawiAlexandra Grigore Aldo R. Boccaccini 《Progress in Polymer Science》2012,37(8):1051-1078
Poly(glycerol sebacate) (PGS) is a biodegradable polymer increasingly used in a variety of biomedical applications. This polyester is prepared by polycondensation of glycerol and sebacic acid. PGS exhibits biocompatibility and biodegradability, both highly relevant properties in biomedical applications. PGS also involves cost effective production with the possibility of up scaling to industrial production. In addition, the mechanical properties and degradation kinetics of PGS can be tailored to match the requirements of intended applications by controlling curing time, curing temperature, reactants concentration and the degree of acrylation in acrylated PGS. Because of the flexible and elastomeric nature of PGS, its biomedical applications have mainly targeted soft tissue replacement and the engineering of soft tissues, such as cardiac muscle, blood, nerve, cartilage and retina. However, applications of PGS are being expanded to include drug delivery, tissue adhesive and hard tissue (i.e., bone) regeneration. The design and fabrication of PGS based devices for applications that mimic native physiological conditions are also being pursued. Novel designs range from accordion-like honeycomb structures for cardiac patches, gecko-like surfaces for tissue adhesives to PGS (nano) fibers for extra cellular matrix (ECM) like constructs; new design avenues are being investigated to meet the ever growing demand for replacement tissues and organs. In less than a decade PGS has become a material of great scrutiny and interest by the biomedical research community. In this review we consolidate the valuable existing knowledge in the fields of synthesis, properties and biomedical applications of PGS and PGS-related biomaterials and devices. 相似文献
32.
33.
Aldo R. Boccaccini Melek Erol Wendelin J. Stark Dirk Mohn Zhongkui Hong João F. Mano 《Composites Science and Technology》2010
Nanoscale bioactive glasses have been gaining attention due to their reported superior osteoconductivity when compared to conventional (micron-sized) bioactive glass materials. The combination of bioactive glass nanoparticles or nanofibers with polymeric systems enables the production of nanocomposites with potential to be used in a series of orthopedic applications, including scaffolds for tissue engineering and regenerative medicine. This review presents the state of art of the preparation of nanoscale bioactive glasses and corresponding composites with biocompatible polymers. The recent developments in the preparation methods of nano-sized bioactive glasses are reviewed, covering sol–gel routes, microemulsion techniques, gas phase synthesis method (flame spray synthesis), laser spinning, and electro-spinning. Then, examples of the preparation and properties of nanocomposites based on such inorganic bionanomaterials are presented, obtained using various polymer matrices, including polyesters such as poly(hydroxybutyrate), poly(lactic acid) and poly(caprolactone), and natural-based polymers such as polysaccharides (starch, chitin, chitosan) or proteins (silk fibroin, collagen). The physico-chemical, mechanical, and biological advantages of incorporating nanoscale bioactive glasses in such biodegradable nanocomposites are discussed and the possibilities to expand the use of these materials in other nanotechnology concepts aimed to be used in different biomedical applications are also highlighted. 相似文献
34.
The analysis of the infinite homogeneous reactor can be useful to have a quick understanding of nuclear reactor phenomena. Thanks to the fact that the neutron emission spectrum from fission is modeled in order to depend neither on the energy of the incident neutron nor on the fissioning nuclide, the critical neutron balance equation can be transformed from an eigenvalue problem to a simple inhomogeneous system. Similar considerations can be addressed to the adjoint problem and to the generalized importance, which can be computed with direct expressions. After having derived the equations relative to the above quantities, we apply them to the investigation of some features of the neutron spectrum in UO2 and MOX fuel. We deduce some relationships between the properties of the medium and the neutron spectrum, such as the independence of the neutron spectrum from the fission cross section and the neutron multiplicity. We show also in which extent these conclusions can be applied to real reactors. 相似文献
35.
36.
Infinite medium flux weighted cross-sections used in nodal calculations enable equivalence with the corresponding fine configuration if the following condition is satisfied: the flux shape inside the assembly in the core is close to the infinite medium flux shape (computed in lattice calculations). In presence of big flux gradients this condition is not satisfied and the absence of information about cross-sections distributions inside a node does not permit to predict the reaction rates with the same accuracy attained in ordinary situations. This tendency is amplified in case of high heterogeneous regions where tilting the flux causes big changes in reaction rates. The method presented here uses information coming from the lattice calculations that produced the homogenized cross-sections, in order to predict the right reaction rate even in presence of high tilted flux shapes. This is done in evaluating a variation of the cross-sections equivalent to the variation in reaction rate, but no variation is applied to the discontinuity factors. The accuracy of the method and its limitations are shown in several significant configurations. Its implementation in the Areva NP reactor core simulation system SCIENCE has shown better evaluation of control rod worth in comparisons with experimental results. 相似文献
37.
38.
Three strains of rats were fed a fish oil diet to verify their ability to incorporate and convert dietary eicosapentaenoic
acid (20∶5ω3) into trienoic prostaglandins. Our results show that such conversion indeed occurs in kidney medullae homogenates.
Specifically, the presence of prostaglandin E3 (PGE3) was established by gas chromatographic-mass spectrometric (GC-MS) analysis. That compound was conclusively identified by
comparison of fragment ions and their relative intensities with those obtained from authentic PGE3. Further evidence was provided by studying the recovery of exogenously added PGE3. The crude ethyl acetate extracts of the medullary homogenates were methylated and cleaned up by liquid-gel chromatography
with Lipidex-5000 prior to conversion to PGB3 for GC-MS analysis. The PGE3 was quantified by selected ion monitoring (SIM) with [3,3,4,4-2H4PGE2 as internal standard. The levels of PGE3 were similar, about 3 ng/mg of wet tissue, in the 3 strains of rats. Identical in vivo conversion of the 20∶5ω3 fatty acid
to PGE3 could not be positively established by analysis of pooled urine specimens. 相似文献
39.
A room temperature conductivity maximum was recognized in the system AgI:Ag2O.B2O3 at 78.8 mole% AgI, the mobile species being silver ions.X-rays diffraction and DTA showed the glass-like nature of this material which maintains its good electrochemical performances in the temperature range 25–230°. The discharge behaviour of solid state galvanic cells containing this material is close to that obtained from 4AgI:Ag2WO4. 相似文献
40.
Levi F Lorini L Calonico D Godone A 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2004,51(10):1216-1224
In this paper we report the accuracy evaluation of the Italian primary frequency standard IEN-CsF1. We discuss the shifts the frequency standard is corrected for and the procedure used for the accuracy evaluation. In the last section we report frequency comparisons of our fountain with those of remote laboratories and with International Atomic Time. 相似文献