全文获取类型
收费全文 | 34178篇 |
免费 | 1844篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 252篇 |
综合类 | 17篇 |
化学工业 | 6797篇 |
金属工艺 | 631篇 |
机械仪表 | 729篇 |
建筑科学 | 945篇 |
矿业工程 | 73篇 |
能源动力 | 582篇 |
轻工业 | 5774篇 |
水利工程 | 319篇 |
石油天然气 | 129篇 |
武器工业 | 5篇 |
无线电 | 1275篇 |
一般工业技术 | 5781篇 |
冶金工业 | 8112篇 |
原子能技术 | 119篇 |
自动化技术 | 4515篇 |
出版年
2024年 | 82篇 |
2023年 | 304篇 |
2022年 | 334篇 |
2021年 | 808篇 |
2020年 | 689篇 |
2019年 | 797篇 |
2018年 | 1395篇 |
2017年 | 1372篇 |
2016年 | 1405篇 |
2015年 | 1080篇 |
2014年 | 1281篇 |
2013年 | 2641篇 |
2012年 | 1983篇 |
2011年 | 1805篇 |
2010年 | 1474篇 |
2009年 | 1320篇 |
2008年 | 1286篇 |
2007年 | 1218篇 |
2006年 | 805篇 |
2005年 | 701篇 |
2004年 | 655篇 |
2003年 | 580篇 |
2002年 | 566篇 |
2001年 | 415篇 |
2000年 | 395篇 |
1999年 | 445篇 |
1998年 | 2426篇 |
1997年 | 1655篇 |
1996年 | 1045篇 |
1995年 | 637篇 |
1994年 | 487篇 |
1993年 | 580篇 |
1992年 | 207篇 |
1991年 | 208篇 |
1990年 | 158篇 |
1989年 | 157篇 |
1988年 | 160篇 |
1987年 | 138篇 |
1986年 | 120篇 |
1985年 | 141篇 |
1984年 | 124篇 |
1983年 | 95篇 |
1982年 | 133篇 |
1981年 | 144篇 |
1980年 | 154篇 |
1979年 | 79篇 |
1978年 | 85篇 |
1977年 | 279篇 |
1976年 | 627篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
Talita Moreira de Oliveira Nilda de Fátima Ferreira Soares Rodrigo Magela Pereira Kátia de Freitas Fraga 《Packaging Technology and Science》2007,20(2):147-153
Conservation of food products depends on product quality and packaging suitability. The objective of this work was to develop and evaluate the antimicrobial efficiency of natamycin‐incorporated film in the production process of Gorgonzola cheese. It aims to optimize the production process and increase shelf‐life and food safety for the consumer. Films with different concentrations of natamycin were produced and tested in Gorgonzola cheeses to evaluate its efficiency against Penicillium roqueforti on the cheese surface. Films with 2 and 4% natamycin presented satisfactory results for fungus inhibition and the amount of natamycin released to the cheese was below that allowed by the legislation. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
73.
András Ványolos Balázs Dóra Attila Virosztek 《Journal of Superconductivity and Novel Magnetism》2007,20(7-8):643-645
We report of a theoretical study on quasi-one dimensional unconventional charge density wave (UCDW) driven by electron–phonon
interaction. Within mean field theory, we find that the wavevector dependence of the coupling leads to a momentum dependent
single particle gap on the Fermi surface. The presence of small energy single particle excitations around the gap nodes significantly
changes the optical conductivity compared to the conventional CDW result. In addition to that, the collective phase excitation
arising from fluctuation of the order parameter leads to further qualitative changes of the conductivity and results in an
effective mass that is nonmonotonic in temperature.
相似文献
74.
75.
The Role of Network Topologies in the Optical Core of IP-over-WDM Networks with Static Wavelength Routing 总被引:3,自引:0,他引:3
Freire Mário M. Rodrigues Joel J.P.C. Coelho Rui M.F. 《Telecommunication Systems》2003,24(2-4):111-122
In this paper, we present a performance analysis of network topologies for the optical core of IP-over-WDM networks with static wavelength routing. The performance analysis is focused on regular degree four topologies, and, for comparison purposes, degree three topologies are also considered. It is shown that the increase of the nodal degree from three (degree three topology with smallest diameter) to four (degree four topology with smallest diameter) improves the network performance if a larger number of wavelengths per link is available. However, the influence of wavelength interchange on the nodal degree gain is small. The performance of regular degree four topologies with smallest diameter is also compared with the performance of mesh–torus topologies (which are also degree four topologies), and it is shown that the blocking probability of degree four topologies with smallest diameter is about two orders of magnitude lower than the blocking probability of mesh–torus topologies. It is also presented a performance comparison of WDM-based networks with nodal degrees ranging from two to five and it is shown that the increase of the nodal degree from two to three leads to high nodal degree gains, while de increase of the nodal degree from four to five leads to low nodal degree gains. These results show that degree three and degree four topologies are very attractive for use in the optical core of IP-over-WDM networks. 相似文献
76.
Jefferson Fabrício Cardoso Lins Hugo Ricardo Z. Sandim Hans-Jürgen Kestenbach 《Journal of Materials Science》2007,42(16):6572-6577
The present paper reports the experimental results on the microstructural and textural characterization of a hot-rolled IF
steel. The IF steel was hot-rolled in multiple passes in the austenitic field (1,070 °C) followed by air-cooling. SEM, TEM,
and LOM were used to image the microstructure of the material. The global texture was determined by X-ray diffraction (XRD)
technique. The mesotexture of selected regions was investigated by electron backscatter diffraction (EBSD). Results show the
presence of a diffuse (nearly random) and weak texture in the hot-band that consists of recrystallized polygonal grains and
subgrains. The fraction of boundaries with misorientations comprised in the interval 2° ≤ ψ < 15° was found to be lower than
5%. It can be concluded that these low angle boundaries and the presence of subgrains can be associated to the existence of
a few areas softened by recovery during or after hot rolling in austenitic field. 相似文献
77.
78.
The authors suggest that academic institutions build business-oriented policies and practices into the development of any nurse-run clinic to set the stage for financial independence when special or development funding ends. One university-affiliated program that provides 4,000 to 5,000 annual visits drastically changed its strategies when threatened with closure after free rent and other subsidies were withdrawn. The growing emphasis on ambulatory care roles for nurses at all levels makes such clinics critical to the success of the broad-based curricula of nursing education programs, as well as the clinic's value to communities they serve. Funding difficulties frequently threaten the existence of such nurse-run clinics once the initial grant funding is no longer available. This has caused a new emphasis on running such clinics in a business-wise manner. Among the strategies initiated were: direct full-pay at the time of service; a realistic business management plan; aggressive planned marketing; contracts and agreements with other agencies; obtaining provider status with selected HMOs. 相似文献
79.
A Lubics D Regl?di S Slezák M Szelier I Lengvári 《Canadian Metallurgical Quarterly》1997,99(4):459-467
In addition to receptor-type pinealocytes, the mammalian pineal organ contains small and large neurons and ependymal/glial cells as well. Axons of pinealocytes form synaptic ribbon-containing axo-dendritic synapses on large secondary pineal neurons and/or terminate as neurohormonal endings on the basal lamina of the vascular surface of the organ. The small pineal neurons were found to be gamma-aminobutyric acid (GABA)-immunoreactive, while large secondary neurons and pinealocytes contained immunoreactive amino acids (glutamate and aspartate). Glutamate accumulated presynaptically in pinealocytic axon terminals on large secondary neurons and in the axons of these neurons. Glutamate immunoreactive axons of pineal neurons were traced via the pineal tract to the habenular nucleus. Axons containing granular vesicles and coming from extrapineal perikarya are glutamate immunoreactive as well. Aspartate and GABA are also present in some of the myelinated axons, supposedly pinealopetal in the pineal tract. 相似文献
80.
J Sánchez A Torres J Serrano J Román C Martín L Pérula F Martínez P Gómez 《Canadian Metallurgical Quarterly》1997,20(5):403-408
BACKGROUND: Locally advanced thyroid cancer invading the tracheal cartilage represents a difficult treatment dilemma during thyroidectomy. METHODS: A retrospective chart review was performed to determine the results of laryngotracheal resection or tracheal cartilage shave with adjuvant radiotherapy in patients with locally advanced thyroid cancer invading the upper airway. RESULTS: Of 597 patients undergoing thyroidectomy for thyroid cancer, 40 were found to have laryngotracheal invasion. Thirty-five patients with superficial invasion underwent cartilage shave procedures with adjuvant radiotherapy; five with full-thickness invasion underwent radical resection, including tracheal sleeve resection (n = 3) or total laryngectomy (n = 2). Histologic subtypes included papillary (n = 32), follicular (n = 2), Hurthle cell (n = 1), medullary (n = 3), and anaplastic (n = 2). Of the cartilage shave group, 25 are currently alive with no evidence of disease at a mean follow-up of 81 months (range 1-290). Six developed isolated local/regional recurrence and were managed with total laryngectomy (n = 1), tracheal resection (n = 1), cervical lymphadenectomy (n = 1), or repeat radiotherapy (n = 3). All six patients remain free of disease at a mean follow-up of 5 years. Of those who underwent initial laryngotracheal resection, four remain free of disease at a mean follow-up of 5 years. The rates of 10-year disease-free survival and overall survival for all patients were 47.9% (95% confidence interval [CI] 24.8, 71.0) and 83.9% (95% CI 70.3, 97.5), respectively. CONCLUSIONS: These data suggest that adequate management of thyroid cancer with laryngotracheal invasion can be achieved with a more conservative surgical approach and adjuvant radiotherapy, reserving more radical resections for extensive primary lesions or locally recurrent disease. 相似文献