全文获取类型
收费全文 | 1355篇 |
免费 | 26篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 22篇 |
综合类 | 3篇 |
化学工业 | 139篇 |
金属工艺 | 14篇 |
机械仪表 | 16篇 |
建筑科学 | 10篇 |
矿业工程 | 4篇 |
能源动力 | 47篇 |
轻工业 | 23篇 |
水利工程 | 4篇 |
无线电 | 76篇 |
一般工业技术 | 158篇 |
冶金工业 | 805篇 |
原子能技术 | 7篇 |
自动化技术 | 59篇 |
出版年
2024年 | 6篇 |
2023年 | 6篇 |
2022年 | 17篇 |
2021年 | 42篇 |
2020年 | 34篇 |
2019年 | 36篇 |
2018年 | 30篇 |
2017年 | 31篇 |
2016年 | 29篇 |
2015年 | 27篇 |
2014年 | 21篇 |
2013年 | 44篇 |
2012年 | 28篇 |
2011年 | 41篇 |
2010年 | 32篇 |
2009年 | 33篇 |
2008年 | 27篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 10篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 16篇 |
1998年 | 242篇 |
1997年 | 148篇 |
1996年 | 103篇 |
1995年 | 48篇 |
1994年 | 32篇 |
1993年 | 47篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1978年 | 2篇 |
1977年 | 26篇 |
1976年 | 39篇 |
1975年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有1387条查询结果,搜索用时 0 毫秒
961.
JM de Klerk AD van het Schip BA Zonnenberg A van Dijk JM Quirijnen GH Blijham PP van Rijk 《Canadian Metallurgical Quarterly》1996,37(2):244-249
A new species and additional host records for 4 other species of quiescent deutonymphs (hypopi) of mites of the family Hypoderatidae are described from the subcutaneous adipose tissues of a roseate spoonbill, Ajaia ajaja L., in Florida. The hypopus of Phalacrodectes parvus n. sp. most closely resembles that of P. platalea Pence & Duncan from the African spoonbill, Platalea alba Scopali, in idiosomatic chaetotaxy and structure of the genital apparatus. It differs from this and other species of the genus in the shape of the idiosoma, pattern and density of idiosomatic sclerotization, the unique posterior extension of secondary sclerotization from the perigenital area, large size and more posterior location of genital seta gm, and small size and sharp-tipped spinelike structure of seta hT on tibia II. In addition to the new species, this roseate spoonbill also was infected with P. whartoni Fain and 3 other less common species of hypoderatid deutonymphs. A key to the deutonymphs of species in the genus Phalacrodectes is presented. 相似文献
962.
A lightweight, robust P2P system to handle flash crowds 总被引:4,自引:0,他引:4
An Internet flash crowd (also known as hot spots) is a phenomenon that results from a sudden, unpredicted increase in an on-line object's popularity. Currently, there is no efficient means within the Internet to deliver Web objects scalably under hot spot conditions to all clients that desire the object. We present peer-to-peer (P2P) randomized overlays to obviate flash-crowd symptoms (PROOFS), a simple, lightweight, P2P approach that uses randomized overlay construction and randomized, scoped searches to locate and deliver objects efficiently under heavy demand to all users that desire them. We evaluate PROOFS' robustness in environments in which clients join and leave the P2P network, as well as in environments in which clients are not always fully cooperative. Through a mix of simulation and prototype experimentation in the Internet, we show that randomized approaches like PROOFS should effectively relieve flash crowd symptoms in dynamic, limited-participation environments. 相似文献
963.
The mineralogical (phase) composition of sulphoaluminate belite cement clinkers was calculated using phase compatibility data of the relevant portion of the five component oxide system CaO---SiO2---Al2O3---Fe2O3---SO3 and was plotted in the plane of three component raw mix. In result a phase fields map (PFM) was obtained showing equilibrium changes in phase composition of clinkers on changes in the raw mixture composition. 相似文献
964.
High power cladding-pumped tunable Er, Yb-doped fibre laser 总被引:2,自引:0,他引:2
Laroche M. Jander P. Clarkson W.A. Sahu J.K. Nilsson J. Jeong Y. 《Electronics letters》2004,40(14):855-856
Efficient high-power operation of a tunable erbium-ytterbium codoped fibre laser end-pumped by two beam-shaped diode-stacks at 940 nm is reported. A maximum output power of 30 W at 1570 nm for 83 W of absorbed pump power with operating wavelength tunable from 1562 to 1627 nm was demonstrated. 相似文献
965.
966.
967.
Quantitative bacillary response to treatment in HIV-associated pulmonary tuberculosis 总被引:1,自引:0,他引:1
RJ Brindle PP Nunn W Githui BW Allen S Gathua P Waiyaki 《Canadian Metallurgical Quarterly》1993,147(4):958-961
A group of 122 patients with culture-proven pulmonary tuberculosis were recruited to examine the concentrations of Mycobacterium tuberculosis in sputum and the relationship to HIV-1 antibody status. They were followed for up to 28 days from the start of antituberculous chemotherapy to assess the early bacillary response to two chemotherapeutic regimens. Of 67 treated with streptomycin, thiacetazone, and isoniazid 17 were HIV positive, and subsequently 55, of whom 20 were HIV positive, were treated with streptomycin, rifampin, isoniazid, and pyrazinamide. The mean initial concentration of M. tuberculosis in the sputum of the HIV-negative patients was significantly higher than in HIV-positive patients (6.95 and 6.34 log colony-forming units respectively; p = 0.019). The HIV-positive patients had less radiologic evidence of disease and significantly fewer zones of lung affected with cavities. The response to treatment was similar, but with HIV-positive patients more likely to become culture negative by 28 days. The differences that exist between HIV-positive and HIV-negative patients are minor, and standard regimens are at least as effective in HIV-positive patients in the first month of treatment. 相似文献
968.
P Haentjens H de Boeck F Handelberg PP Casteleyn P Opdecam 《Canadian Metallurgical Quarterly》1993,(290):225-235
In a previous study, the results of cemented acetabular reconstruction with a Müller support ring were reported after a mean follow-up period of 40 months. The current report concerns a minimum five-year follow-up study of the same 43 patients. Two early failures at four months and at 17 months were related to poor surgical technique. The latest overall functional results, according to the Merle d'Aubigné rating scale, were excellent, very good, or good in 81.82% of the hips: a drop from 86.67% since the previous report. Sequential roentgenographic analysis demonstrated a high incidence of nonprogressive radiolucencies at the cement-bone interface. These nonprogressive radiolucencies did not correlate with the overall functional results. The progression of a radiolucency at the cement-bone interface, however, or the appearance of radiolucencies around the screw threads, always resulted in clinical failure. 相似文献
969.
970.
Mesoderm formation in the mouse embryo begins at 6.5-6.75 days p.c. (postcoitum) when a primitive streak is formed along the posterior side of the egg cylinder. Epiblast cells in a localized region separate from one another and spread laterally between the primitive endoderm and the rest of the epiblast. The newly formed mesoderm contributes to both embryonic and extraembryonic regions. When the endoderm is removed, a definitive somitomeric pattern is first observed in the lateral sings of mesoderm of the mid-primitive-streak-stage embryo. The sequential appearance and the placement of somitomeres in the gastrulating mouse embryo are closely related to the general changes in physical dimensions and to the pattern of tissue growth which occur during the maturation of the egg cylinder. By the late-primitive-streak stage, about four somitomeres are present in the paraxial mesoderm on either side of the embryonic axis. These somitomeres will undergo morphogenesis and give rise to the cranial segments and head mesenchyme of neurulating embryos (Meier and Tam, 1982). The midline or axial mesoderm, consisting of prechordal plate and notochord, is derived from the head process mesoderm originating from the anterior end of the primitive streak. Cells of the head process are compact and adherent to the endoderm. The early presence of a somitomeric pattern which persists and is added to throughout subsequent phases of mesoderm formation suggests that spreading mesodermal cells have relatively stable neighbor relationships. This morphological evidence supports the idea that the expansion of the mesoderm during gastrulation results from tissue growth and progressive deposition of cells from the primitive streak. Cell migration may be limited principally to nonsomitomeric mesodermal cells found in the leading edge of the spreading lateral wings. 相似文献