全文获取类型
收费全文 | 1359篇 |
免费 | 4篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 4篇 |
综合类 | 10篇 |
化学工业 | 40篇 |
金属工艺 | 19篇 |
机械仪表 | 7篇 |
建筑科学 | 8篇 |
矿业工程 | 2篇 |
能源动力 | 3篇 |
轻工业 | 18篇 |
水利工程 | 5篇 |
石油天然气 | 2篇 |
无线电 | 26篇 |
一般工业技术 | 30篇 |
冶金工业 | 1162篇 |
原子能技术 | 3篇 |
自动化技术 | 30篇 |
出版年
2021年 | 3篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 4篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 22篇 |
2008年 | 22篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 10篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 37篇 |
1998年 | 267篇 |
1997年 | 171篇 |
1996年 | 117篇 |
1995年 | 73篇 |
1994年 | 65篇 |
1993年 | 81篇 |
1992年 | 16篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 29篇 |
1988年 | 26篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 2篇 |
1978年 | 9篇 |
1977年 | 42篇 |
1976年 | 95篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 8篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1966年 | 3篇 |
1964年 | 2篇 |
1955年 | 2篇 |
1932年 | 1篇 |
排序方式: 共有1369条查询结果,搜索用时 15 毫秒
31.
GR Bayyari WE Huff RA Norton JK Skeeles JN Beasley NC Rath JM Balog 《Canadian Metallurgical Quarterly》1994,38(4):744-754
Two flocks of Nicholas tom turkeys from separate farms with histories of above-average condemnations for turkey green-liver osteomyelitis complex (TOC) were studied throughout a 16-week growout. Fifty birds from each farm were necropsied each week for 15 weeks, and birds that had green livers, osteomyelitis in the proximal tibia, or swollen joints were cultured for aerobic bacteria along with an equal number of control birds. At processing, TOC lesions and green livers were obtained for bacterial culture and histopathology. Green-liver-associated TOC was not observed until the turkeys were 9 or 10 weeks of age. The incidence of TOC was higher on one farm, which also had a higher incidence of airsacculitis, higher early and weekly mortality, seroconversion to Newcastle disease virus and Mycoplasma meleagridis, and significantly higher average body weights, relative spleen weights, and relative liver weights. Both farms had a high incidence of intestinal lesions and infestation with Ascaridia dissimilis. Histological evaluation of green livers revealed hyperplasia of bile ducts, dilation of sinusoids, and pigment-containing Kupffer's cells, some of which stained positive for iron. The bacterial isolates most frequently cultured from bones and livers were pleomorphic gram-variable coccobacilli, which grew visible colonies only after a series of subcultures and extended incubation. 相似文献
32.
33.
Recent procedures for autologous repair of cartilage defects may be difficult in elderly patients because of the loss of stem cells and chondrocytes that occurs with age and the slow in vitro proliferation of chondrocytes from aged cartilage. In this study secondary chondroprogenitor cells were obtained by modulating the phenotype of articular chondrocytes with growth factors and stimulating the proliferation of these cells in culture. Chondrocytes isolated from the articular cartilage of mature New Zealand White rabbits were exposed to a combination of transforming growth factor beta and basic fibroblast growth factor treatment. These cells ceased the production of Collagen II (a marker for the chondrocyte phenotype) and underwent a 136-fold increase in cell number. Next, the cells were placed in high density culture and reexpressed the chondrocyte phenotype in vitro and formed hyaline cartilage in an in vivo assay. Primary chondrocytes obtained from articular cartilage of elderly humans could be manipulated in a similar fashion in vitro. These human secondary chondroprogenitor cells formed only cartilage tissue when assayed in vivo and in tissue bioreactors. This approach may be essential for autologous repair of degenerated articular cartilage in elderly patients with osteoarthritis. 相似文献
34.
35.
WE Farrell DJ Simpson JE Bicknell AJ Talbot AS Bates RN Clayton 《Canadian Metallurgical Quarterly》1997,57(13):2703-2709
We have screened 57 cases of primary, nonfunctional, pituitary adenomas for loss of heterozygosity of markers on chromosome 9p. Using a panel of 11 microsatellite markers, we found hemizygous deletion with at least one of the markers in 18 tumors (31.5%). The frequency of loss was similar in both noninvasive (8 of 26; 31%) and invasive tumors (10 of 31; 32%), suggesting that loss on this chromosome might be an early event in pituitary tumorigenesis. Two discrete areas of loss were punctuated by a region of retention of heterozygosity between the markers D9S171 and IFNA, indicative of homozygous deletion. However, multiplex PCR analysis (MTS1 and MTS2) and the presence of a 3' untranslated region polymorphism in MTS1 suggested that neither of these tumor suppressor genes was homozygously deleted. In 6 of the 18 tumors showing LOH, sufficient DNA was also available for Southern blot analysis and, in all cases, showed retention of MTS1. Cell mixing experiments of tumor cell DNA homozygously deleted for MTS1 with DNA in which neither copy of the gene was deleted only gave rise to a signal at contamination levels greater than 30% and could discriminate homozygous and hemizygous loss. These studies support the recent findings that mechanisms other than hemi- and homozygous deletion are most likely responsible for the loss of MTS1 gene product in pituitary tumors (M. Woloschak et al., Cancer Res., 56: 2493-2486, 1996.). These data show that losses on either side of 9p21-22, both or either of which may be deleted, are involved in pituitary tumorigenesis and provide evidence for distinct suppressor gene loci, in addition to MTS1, on chromosome 9p. 相似文献
36.
37.
38.
CR Marmar DS Weiss WE Schlenger JA Fairbank BK Jordan RA Kulka RL Hough 《Canadian Metallurgical Quarterly》1994,151(6):902-907
OBJECTIVE: The aim of this study was to determine the reliability and validity of a proposed measure of peritraumatic dissociation and, as part of that effort, to determine the relationship between dissociative experiences during disturbing combat trauma and the subsequent development of posttraumatic stress disorder (PTSD). METHOD: A total of 251 male Vietnam theater veterans from the Clinical Examination Component of the National Vietnam Veterans Readjustment Study were examined to determine the relationship of war zone stress exposure, retrospective reports of dissociation during the most disturbing combat trauma events, and general dissociative tendencies with PTSD case determination. RESULTS: The total score on the Peritraumatic Dissociation Experiences Questionnaire--Rater Version was strongly associated with level of posttraumatic stress symptoms, level of stress exposure, and general dissociative tendencies and weakly associated with general psychopathology scales from the MMPI-2. Logistic regression analyses supported the incremental value of dissociation during trauma, over and above the contributions of level of war zone stress exposure and general dissociative tendencies, in accounting for PTSD case determination. CONCLUSIONS: These results provide support for the reliability and validity of the Peritraumatic Dissociation Experiences Questionnaire--Rater Version and for a trauma-dissociation linkage hypothesis: the greater the dissociation during traumatic stress exposure, the greater the likelihood of meeting criteria for current PTSD. 相似文献
39.
JD Belcher RC Ellison WE Shepard C Bigelow LS Webber JH Wilmore GS Parcel DM Zucker RV Luepker 《Canadian Metallurgical Quarterly》1993,22(2):143-153
Male and female isometric strength curves for elbow fixation, shoulder flexion, and wrist supination-pronation are obtained during systematic variation in arm configuration. The shape of a given moment-angle curve is found to be a function of the orientations of joints kinematically coupled to the primary joint. It is also found that female elbow strength curves are shifted toward flexion with respect to male elbow-strength curves, suggesting that the in situ rest length of upper-limb muscles relative to joint angle may be longer for males than for females. Experimental results were contrasted with simulation results obtained using a three-dimensional musculoskeletal model which estimates the relationships between initial joint orientations, muscle tension-length behavior, and joint moments. In most of the cases, simulation results complimented experimental data and provided insights into likely in situ muscle rest lengths and moments arms, especially for the multiarticular biceps brachii muscle. Where inconsistencies exist between simulated and experimental data, subtle biomechanical complexities within the forearm and the shoulder girdle complex are identified that require future investigation. 相似文献
40.
DF Zatzick DS Weiss CR Marmar TJ Metzler K Wells JM Golding A Stewart WE Schlenger WS Browner 《Canadian Metallurgical Quarterly》1997,162(10):661-665
OBJECTIVE: This investigation assessed whether current post-traumatic stress disorder (PTSD) was associated with impaired functioning in a nationally representative sample of female Vietnam veterans. METHODS: Logistic models were used to determine the association between PTSD and outcome while adjusting for demographic characteristics and medical and psychiatric co-morbidities. RESULTS: PTSD was associated with significantly elevated odds of poorer functioning in five of the six outcome domains; only the association between perpetration of violence in the past year and PTSD did not achieve statistical significance. After adjusting for demographics and medical and psychiatric co-morbidities, PTSD remained associated with significantly elevated odds of bed days, poorer physical health, and currently not working. CONCLUSIONS: Among female Vietnam veterans PTSD is associated with a broad profile of functional impairment. The significantly increased odds of impaired functioning and diminished quality of life suggest that PTSD may be the core problem of the set of problems afflicting female Vietnam veterans. 相似文献