全文获取类型
收费全文 | 3601篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
综合类 | 4篇 |
化学工业 | 85篇 |
金属工艺 | 19篇 |
机械仪表 | 5篇 |
建筑科学 | 47篇 |
矿业工程 | 1篇 |
能源动力 | 7篇 |
轻工业 | 46篇 |
水利工程 | 1篇 |
无线电 | 23篇 |
一般工业技术 | 57篇 |
冶金工业 | 3297篇 |
原子能技术 | 1篇 |
自动化技术 | 20篇 |
出版年
2023年 | 3篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 14篇 |
2012年 | 14篇 |
2011年 | 23篇 |
2010年 | 25篇 |
2009年 | 13篇 |
2008年 | 13篇 |
2007年 | 18篇 |
2006年 | 17篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 15篇 |
2002年 | 9篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 124篇 |
1998年 | 1068篇 |
1997年 | 662篇 |
1996年 | 386篇 |
1995年 | 226篇 |
1994年 | 165篇 |
1993年 | 211篇 |
1992年 | 23篇 |
1991年 | 41篇 |
1990年 | 28篇 |
1989年 | 35篇 |
1988年 | 26篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 23篇 |
1979年 | 4篇 |
1978年 | 11篇 |
1977年 | 73篇 |
1976年 | 136篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1955年 | 6篇 |
排序方式: 共有3615条查询结果,搜索用时 0 毫秒
991.
A randomized controlled trial in women with neuropathic faecal incontinence compared total pelvic floor repair (n = 12) with anterior levatorplasty and sphincter plication alone (n = 12) and postanal repair alone (n = 12). Review at 6 and 24 months indicated that results were significantly better for total pelvic floor repair than either of the other procedures. Complete continence was achieved in eight of the 12 patients 2 years after total pelvic floor repair. Only total repair significantly elongated the anal canal. Both total pelvic floor repair and anterior levatorplasty improved sensation in the upper anal canal. 相似文献
992.
993.
W Rahman MR Dashwood M Fitzgerald A Aynsley-Green AH Dickenson 《Canadian Metallurgical Quarterly》1998,108(1-2):239-254
The postnatal ontogeny of mu, delta and kappa opioid receptor binding sites in the spinal cord of rat pups at various postnatal days was determined using in vitro autoradiographical methods. The functional effect of spinal morphine was also assessed using in vivo electrophysiological methods in rats at P14, P21 and adults (P56). Both mu and kappa opioid receptor binding-sites are present from P0 and spread relatively diffusely throughout the spinal cord. Overall binding peaks at P7 and subsequently decreases to adult levels with the mu opioid receptor binding sites regressing to become denser in the superficial dorsal horn. delta Opioid receptor binding was first seen at P7, and no distinction between superficial and deeper laminae was seen. In the adult, the relative proportions of the opiate receptors in the superficial dorsal horn are 63%, 22% and 15%, for mu, delta and kappa receptor binding sites, respectively. C-fibre evoked dorsal horn neuronal responses recorded from anaesthetized rat pups were highly sensitive to spinal morphine at P21, (EC50 0.005 microgram), compared to the adult (EC50 0.9 microgram). However, the EC50 (0.2 microgram) at P14 was greater than at P21 despite the fact that mu receptor binding was greater at P14. Opioid receptor binding is developmentally regulated and undergoes substantial postnatal reorganization. However, the number of mu receptor binding sites appears not to be the only determinant of functional sensitivity to spinal morphine. Other factors, such as coupling of the receptors are likely to be important. 相似文献
994.
995.
The annexins are a family of calcium-dependent phospholipid-binding proteins which share a high degree of primary sequence similarity. Using a model of the crystal structure of annexin V as a template, 3-dimensional models of human annexins I, II, III and VII were constructed by homology modeling (J. Greer, J. Mol. Biol. 153, 1027-1042, 1981; J.M. Chen, G. Lee, R.B. Murphy, R.P. Carty, P.W. Brant-Rauf, E. Friedman and M.R. Pincus, J. Biomolec. Str. Dyn. 6, 859-87, 1989) for the 316 amino acid portions corresponding to the annexin V structure published by Huber et al. (J. Mol. Biol. 223, 683-704, 1992). These methods were used to study structure-function correlations for calcium ion binding and calcium channel activity. Published experimental data are specifically shown to be consistent with the annexin models. Possible intramolecular disulfide bridges were identified in annexin I (between Cys297 and Cys316) and in annexins II and VII (between Cys115 and Cys243). Each of the annexin models have 3 postulated calcium binding sites, usually via a Gly-Xxx-Gly-Thr loop with an acidic Glu or Asp residue 42 positions C-terminal to the first Gly. Despite a nonconserved binding site sequence, annexins I and II are able to coordinate calcium in domain 3 since the residue in the second loop position is directed toward the solvent away from the binding pocket. This finding also suggests a mechanism for a conformational change upon binding calcium. Highly conserved Arg and acidic sidechains stabilize the channel pore structure; annexin channels probably exist in a closed state normally. Arg271 may be involved in channel opening upon activation: basic residue 254 can stabilize Glu112, which allows Arg271 to interact with residue 95 instead of Glu112. Residue 267, found on the convex surface at the pore opening, may also be important in modifying channel activity. 相似文献
996.
RG Roberts MR Passos-Bueno M Bobrow M Vainzof M Zatz 《Canadian Metallurgical Quarterly》1993,2(1):75-77
Occupational therapy intervention in the area of seating and positioning may play a vital role in improving the quality of life for nursing home residents. This case report indicates that appropriately positioning a client may increase comfort, decrease agitation, and decrease the administration of mood-altering drugs. Research would help to delineate the effects of appropriate seating systems, both to ensure reimbursement and to ensure that all who might benefit from positioning intervention receive the appropriate services. OBRA 1987 regulations are forcing nursing homes to assess residents for the least restrictive restraints. These assessments offer a golden opportunity for occupational therapists to become involved in determining the most appropriate seating systems and to conduct research on their benefits. 相似文献
997.
M Bernués C Casadevall R Miró MR Caballín A Gelabert J Egozcue 《Canadian Metallurgical Quarterly》1993,69(1):76-77
Monosomy for chromosome 9, as well as loss of heterozygosity for markers on this chromosome, has been detected in a high percentage of transitional cell carcinomas (TCC) of the bladder. We report a case of a TCC of the bladder with an interstitial del(9)(q11q21.2) that could be indicative of the presence of a putative tumor-suppressor gene related to bladder tumor progression. To elucidate the role of chromosome 9 in bladder tumors, it would be interesting to study a possible loss of heterozygosity in this chromosome region. 相似文献
998.
This study investigated the relationship between health care use and (a) stressful work events; (b) strain; (c) social support; (d) type of job and industry; and (e) the individual characteristics of control, commitment, and length of time in position. A sample of 260 individuals (95 men, 165 women) from two different industries was used. Correlational analyses suggested that health care claims and costs were positively related to stressful work events and strain and negatively related to employees' length of time in position. Industry type also played a role in predicting the health care variables. Multivariate analyses suggested that environmental, stressor, and strain variables accounted for up to 16% of the variance in health care costs and 21.5% of the variance in number of health care claims. 相似文献
999.
MF Fojtasek MR Sherman T Garringer R Blair LJ Wheat CT Schnizlein-Bick 《Canadian Metallurgical Quarterly》1993,61(11):4607-4614
Local immunity against acute pulmonary histoplasmosis was studied in the lung-associated lymph nodes of normal nonimmune mice infected intratracheally with live Histoplasma capsulatum yeasts. The phenotypes and distribution of cells in lung-associated lymph nodes and spleens were determined by flow cytometry. In addition, the immune responsiveness of these cells was evaluated by in vitro blastogenesis. Anti-H. capsulatum antibodies in serum and H. capsulatum antigen in tissue were measured by immunoassays. Cellular immune responses were greater in the lymph nodes than in the spleens. In lymph nodes 7 days after infection, a marked increase in the number of B lymphocytes caused the percentage to rise to 43%, compared with 26% in controls, and it remained elevated throughout the course of infection. A CD3+ cell that did not express CD4 or CD8 increased in number until it constituted 21% of lymph node cells, compared with 5% in controls, by day 14. The numbers of CD4+ and CD8+ T lymphocytes were modestly increased from days 7 to 35, but their percentages dropped because of the greater numbers of B lymphocytes and CD3+4-8- cells. Macrophages consistently constituted 2 to 3% of lymph node cells during the study. In spleens 7 days after infection, the percentage of macrophages in infected mice rose to 21%, compared with 9% in controls, but the total spleen cell number did not increase until day 14, when all cell subsets were nearly double in number. The in vitro blastogenic response of lymph node cells to H. capsulatum peaked at day 7, but spleen cell response was minimal during the course of infection. Histoplasma-specific serum immunoglobulin G antibodies reached peak levels by day 21 and remained high to the end of the study. In contrast, levels of antigen-specific immunoglobulin M antibodies were very low. These data suggest that antigen-specific immune responses occur in lung-associated lymph nodes and that this draining lymph node response may be an important component in host defense against Histoplasma lung infection. 相似文献
1000.