全文获取类型
收费全文 | 616篇 |
免费 | 0篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 11篇 |
金属工艺 | 1篇 |
建筑科学 | 3篇 |
矿业工程 | 1篇 |
轻工业 | 5篇 |
无线电 | 6篇 |
一般工业技术 | 6篇 |
冶金工业 | 572篇 |
自动化技术 | 3篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 1篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2000年 | 1篇 |
1999年 | 26篇 |
1998年 | 157篇 |
1997年 | 102篇 |
1996年 | 69篇 |
1995年 | 36篇 |
1994年 | 28篇 |
1993年 | 50篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 24篇 |
1976年 | 38篇 |
1975年 | 2篇 |
排序方式: 共有616条查询结果,搜索用时 15 毫秒
51.
52.
Son and daughter preferences in Benighat, Nepal: implications for fertility transition 总被引:1,自引:0,他引:1
Married women in Benighat, Nepal stressed old age security and continuity of lineage as prominent reasons for wanting sons. In addition, women clearly desired daughters too--an important finding that is less often stressed. Religious reasons and help with household chores were the most common reasons reported for wanting a daughter. Strong desires for sons could increase fertility in settings where fertility is controlled. Additional desires for daughters could have an additional pronatalist influence. For Benighat we document a pervasive desire for at least two sons and at least one daughter. If realized, these sex composition preferences would increase fertility by 50 per cent. Actual effects are no doubt smaller, but the effects of sex preference on the desire for more children and on contraceptive use are clearly visible. 相似文献
53.
54.
Enteropathogenic Escherichia coli (EPEC) secretes at least five proteins. Two of these proteins, EspA and EspB (previously called EaeB), activate signal transduction pathways in host epithelial cells. While the role of the other three proteins (39, 40, and 110 kDa) remains undetermined, secretion of all five proteins is under the control of perA, a known positive regulator of several EPEC virulence factors. On the basis of amino-terminal protein sequence data, we cloned and sequenced the gene which encodes the 110-kDa secreted protein and examined its possible role in EPEC signaling and interaction with epithelial cells. In accordance with the terminology used for espA and espB, we called this gene espC, for EPEC-secreted protein C. We found significant homology between the predicted EspC protein sequence and a family of immunoglobulin A (IgA) protease-like proteins which are widespread among pathogenic bacteria. Members of this protein family are found in avian pathogenic Escherichia coli (Tsh), Haemophilus influenzae (Hap), and Shigella flexneri (SepA). Although these proteins and EspC do not encode IgA protease activity, they have considerable homology with IgA protease from Neisseria gonorrhoeae and H. influenzae and appear to use a export system for secretion. We found that genes homologous to espC also exist in other pathogenic bacteria which cause attaching and effacing lesions, including Hafnia alvei biotype 19982, Citrobacter freundii biotype 4280, and rabbit diarrheagenic E. coli (RDEC-1). Although these strains secrete various proteins similar in molecular size to the proteins secreted by EPEC, we did not detect secretion of a 110-kDa protein by these strains. To examine the possible role of EspC in EPEC interactions with epithelial cells, we constructed a deletion mutant in espC by allelic exchange and characterized the mutant by standard tissue culture assays. We found that EspC is not necessary for mediating EPEC-induced signal transduction in HeLa epithelial cells and does not play a role in adherence or invasion of tissue culture cells. 相似文献
55.
56.
57.
A case-mix classification system for medical rehabilitation 总被引:2,自引:0,他引:2
MG Stineman JJ Escarce JE Goin BB Hamilton CV Granger SV Williams 《Canadian Metallurgical Quarterly》1994,32(4):366-379
Dissatisfaction with Medicare's current system of paying for rehabilitation care has led to proposals for a rehabilitation prospective payment system, but first a classification system for rehabilitation patients must be created. Data for 36,980 patients admitted to and discharged from 125 rehabilitation facilities between January 1, 1990, and April 19, 1991, were provided by the Uniform Data System for Medical Rehabilitation. Classification rules were formed using clinical judgment and a recursive partitioning algorithm. The Functional Independence Measure version of the Function Related Groups (FIM-FRGs) uses four predictor variables: diagnosis leading to disability, admission scores for motor and cognitive functional status subscales as measured by the Functional Independence Measure, and patient age. The system contains 53 FRGs and explains 31.3% of the variance in the natural logarithm length of stay for patients in a validation sample. The FIM-FRG classification system is conceptually simple and stable when tested on a validation sample. The classification system contains a manageable number of groups, and may represent a solution to the problem of classifying medical rehabilitation patients for payment, facility planning, and research on the outcomes, quality, and cost of rehabilitation. 相似文献
58.
BB Lahey B Applegate RA Barkley B Garfinkel K McBurnett L Kerdyk L Greenhill GW Hynd PJ Frick J Newcorn 《Canadian Metallurgical Quarterly》1994,151(8):1163-1171
OBJECTIVE: The purpose of the field trials for oppositional defiant disorder and conduct disorder was to select valid diagnostic thresholds for these disorders and to compare the psychometric properties of DSM-IV criteria for oppositional defiant disorder and conduct disorder with previous DSM diagnostic formulations. METHOD: Structured diagnostic interviews, standardized clinician's validation diagnoses, and multiple measures of impairment were obtained for 440 clinic-referred children and adolescents aged 4-17 years. RESULTS: A diagnostic threshold of four symptoms of oppositional defiant disorder optimized identification of impaired children, improved agreement somewhat with the clinician's validation diagnosis, and had somewhat better test-retest agreement than DSM-III-R. In the case of conduct disorder, the optimal time window for ascertainment of symptoms was clarified. A diagnostic threshold of three symptoms of conduct disorder maximized accurate identification of impaired children and agreement with the clinician's validation diagnosis and resulted in slightly better test-retest agreement than DSM-III-R. Compared with the DSM-III-R definition, the DSM-IV definition of oppositional defiant disorder was somewhat more prevalent, but the prevalence of conduct disorder was essentially unchanged. CONCLUSIONS: DSM-IV definitions of oppositional defiant disorder and conduct disorder are somewhat better than DSM-III-R definitions in terms of internal consistency and test-retest agreement, and the validity of the DSM-IV definition of oppositional defiant disorder is slightly better than that of DSM-III-R. 相似文献
59.
KA Miles DA Leggett BB Kelley MP Hayball R Sinnatamby I Bunce 《Canadian Metallurgical Quarterly》1998,71(843):276-281
Neovascularization of tumours produces a high microvessel density. Although diagnostic imaging is unable to visualize microvessels directly, it is possible to demonstrate associated changes in tissue perfusion. The aim of this study was to use the quantitative functional information and high spatial resolution of perfusion computed tomography to study neovascularization of hepatic metastases. Perfusion CT was performed in 13 patients with hepatic metastases from various primary tumours. Arterial perfusion was measured in the metastasis; both arterial and portal perfusion were measured in a small rim of liver tissue immediately adjacent to the metastasis. Perfusion measurements were correlated against survival of the patient in nine cases. Arterial perfusion was increased above normal values, both in the metastasis (median: 0.62 ml min-1 ml-1; range: 0.26-3.05 ml min-1 ml-1) and in the adjacent liver (median: 0.51 ml min-1 ml-1; range: 0.14-1.60 ml min-1 ml-1). Portal perfusion of adjacent liver was highly variable (median: 0.30 ml min-1 ml-1; range: 0.05-1.85 ml min-1 ml-1). Arterial perfusion was positively correlated with portal perfusion within liver tissue adjacent to metastases (p < 0.05, r = 0.58), a reversal of the normal situation. Survival of the patient correlated with arterial perfusion within the metastasis (p < 0.05, r = 0.69) but more closely with arterial perfusion in the adjacent liver (p < 0.02, r = 0.78). In conclusion, alterations in perfusion within metastases and adjacent liver are in accordance with the histological features of neovascularization. Perfusion CT offers a method for studying neovascularization in the living patient and offers prognostic information. 相似文献
60.