全文获取类型
收费全文 | 492篇 |
免费 | 5篇 |
专业分类
化学工业 | 57篇 |
建筑科学 | 1篇 |
能源动力 | 1篇 |
轻工业 | 10篇 |
石油天然气 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 11篇 |
冶金工业 | 412篇 |
自动化技术 | 2篇 |
出版年
2024年 | 1篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2011年 | 1篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 14篇 |
1998年 | 134篇 |
1997年 | 65篇 |
1996年 | 52篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 23篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1977年 | 11篇 |
1976年 | 27篇 |
1975年 | 3篇 |
排序方式: 共有497条查询结果,搜索用时 0 毫秒
71.
72.
73.
The authors tried to save the hip joint by implanting a vascularized fibular graft, augmented with cancellous bone, into the curetted core of the femoral head that was affected by aseptic necrosis. Forty of 66 hips were observed for a minimum of 20 months and for as long as 66 months (average, 32 months). Clinical assessment according to the cause and severity of the disease was done using the Harris Hip Score. Twenty-eight hips (70%) were rated excellent, 7 (17.5%) were good, 2 (5%) were fair, and 3 (7.5%) failed and were replaced with an artificial joint. Clinically satisfactory results, including good and excellent, were obtained in 35 hips (87.5%). Radiographic evaluation showed improved appearance of the femoral head core in all 15 patients (37.5%) operated on at a precollapse stage of the disease. In 20 hips, the deformity of the femoral head was unchanged (50%), 2 (5%) became worse, and 3 (7.5%) failed. The number of hips with improved appearance as shown on radiographs and those in which the process was unchanged equaled the number of hips with satisfactory clinical results. These data show that the procedure can induce new bone formation that fuses with the affected subchondral bone, thus preventing the articular surface from collapse. This suggests that vascularized fibular grafting is an excellent alternative for hip salvaging when treating femoral head osteonecrosis. 相似文献
74.
K. N. Ninan V. P. Balagangadharan K. Ambikadevi K. B. Catherine 《Polymer International》1993,31(3):255-260
A novel approach is proposed for estimating the average molecular weight between crosslinks (M?c) from the functionality distribution of hydroxyl-terminated polybutadiene ( HTPB ). The functionality distribution of four free-radically polymerised HTPB prepolymers of varying hydroxyl content and molecular weight was determined by a combination of preparative and analytical gel permeation chromatography. The gumstock properties of the samples cured with stoichiometric amounts of toluene diisocyanate were not correlatable with the relative amounts of difunctional chain extender and multifunctional crosslinker present, unlike the case of HTPB with similar hydroxyl content and molecular weight. However, the mechanical properties and sol content could be correlated with the average molecular weight between crosslink sites, M?c, of the cured polymer. The M?c values derived by our method compare well with those of classical methods, and the observed differences are attributed to segmental entanglement. These M?c values give consistently good correlation with all the gumstock properties, confirming the validity of our approach and the soundness of the techniques developed for the determination of the functionality distribution of HTPB . 相似文献
75.
KN Kondrakhina 《Canadian Metallurgical Quarterly》1977,15(1):84-87
This report includes data on insertions of Lippes Loop D, Copper-7, and Copper-T intrauterine devices (IUDs) performed by certified nurse-midwives and physicians with comparable levels of training and experience in inserting IUDs. Net 1-year pregnancy, expulsion, and removal rates were used to compare the experiences of the 2 groups. There were no significant differences between the groups in most of the event rates or in the overall method discontinuation rates. The authors conclude that, with adequate training and experience, nurse-midwives can provide this family planning service with no additional risk to patients. 相似文献
76.
77.
Leukaemic B cells from patients with chronic lymphocytic leukaemia (B-CLL) are known to express the pan T-cell marker CD5 and a restricted set of immunoglobulin (Ig) variable region heavy (VH) and light (VL) chains encoded by germline or minimally mutated germline genes. We have studied surface expression of certain VH and VK gene products on peripheral blood B lymphocytes from 23 patients with B-CLL, using a panel of monoclonal antibodies (MoAbs) recognizing germline encoded cross-reactive idiotypes (CRI) associated with VHI (G6, G8), VHIII (B6, D12), VKIIIb (17-109) and an epitope linked to the VKIII light chain subgroup (C7). While only 1.7-3.2% of peripheral blood B lymphocytes from normal individuals expressed the VHI-associated CRI (VHI-CRI), these CRI were expressed on virtually all the leukaemic B cells from 17-22% of the CLL patients. The VHIII-associated CRI (VHIII-CRI), however, were found in 8.5-13% of the CLL B cells. Fifty per cent of the IgMK-expressing CLL cells (7/14) expressed the VKIII light chain subgroup of which only one expressed the VKIIIb-associated CRI (VKIIIb-CRI), 17-109. The anti-VHI-associated CRI antibodies were used to study their regulatory effect on in vitro Ig synthesis by the leukaemic cells. A significant suppression of spontaneous and mitogen-driven Ig production was observed in all cases studied. These results demonstrate an over-expression of VHI and VKIII gene products in B-CLL and suggest that B cells expressing these CRI are particularly susceptible to lymphoproliferative stimuli. The anti-CRI antibodies can be used to modulate Ig production by the leukaemic cells and may be of potential value for selective immunotherapy. 相似文献
78.
Many antitumor agents and antibiotics affect cells by interacting with type II topoisomerases, stabilizing a covalent enzyme-DNA complex. A pathway of recombination can apparently repair this DNA damage. In this study, transposon mutagenesis was used to identify possible components of the repair pathway in bacteriophage T4. Substantial increases in sensitivity to the antitumor agent m-AMSA [4'-(9-acridinylamino)methanesulfon-m-anisidide] were found with transposon insertion mutations that inactivate any of six T4-encoded proteins: UvsY (DNA synaptase accessory protein), UvsW (unknown function), Rnh (RNase H and 5' to 3' DNA exonuclease), alpha-gt (alpha-glucosyl transferase), gp47.1 (uncharacterized), and NrdB (beta subunit of ribonucleotide reductase). The role of the rnh gene in drug sensitivity was further characterized. First, an in-frame rnh deletion mutation was constructed and analyzed, providing evidence that the absence of Rnh protein causes hypersensitivity to m-AMSA. Second, the m-AMSA sensitivity of the rnh-deletion mutant was shown to require a drug-sensitive T4 topoisomerase. Third, analysis of double mutants suggested that uvsW and rnh mutations impair a common step in the recombinational repair pathway for m-AMSA-induced damage. Finally, the rnh-deletion mutant was found to be hypersensitive to UV, implicating Rnh in recombinational repair of UV-induced damage. 相似文献
79.
80.
The human placental alkaline phosphatase (PLAP) gene was analysed for its utility as a histochemically detectable reporter gene in transgenic mice. A reporter gene was made by linking the PLAP structural gene to an enhancer-promoter element from the human beta-actin gene. This gene was inserted into the mouse genome by transfection of embryonic stem cells, and by microinjection of fertilized eggs. Histochemical staining showed that the transgene was uniformly expressed in four of four stable ES cell lines, and in all ten tissues examined from adult animals from five lines of transgenic mice. Non-transgenic cells did not stain. These results suggest that the human PLAP gene will be of utility in studies requiring phenotypic marking of cells in tissues of mice. 相似文献