全文获取类型
收费全文 | 824篇 |
免费 | 3篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 29篇 |
金属工艺 | 2篇 |
机械仪表 | 3篇 |
建筑科学 | 10篇 |
能源动力 | 1篇 |
轻工业 | 26篇 |
石油天然气 | 1篇 |
无线电 | 7篇 |
一般工业技术 | 25篇 |
冶金工业 | 707篇 |
原子能技术 | 2篇 |
自动化技术 | 13篇 |
出版年
2019年 | 2篇 |
2016年 | 4篇 |
2014年 | 2篇 |
2013年 | 18篇 |
2012年 | 3篇 |
2011年 | 9篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 9篇 |
1999年 | 21篇 |
1998年 | 206篇 |
1997年 | 120篇 |
1996年 | 85篇 |
1995年 | 36篇 |
1994年 | 44篇 |
1993年 | 42篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 20篇 |
1976年 | 30篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1969年 | 2篇 |
1967年 | 2篇 |
1965年 | 2篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有827条查询结果,搜索用时 15 毫秒
11.
12.
13.
Thompson Robert J.; Gil Karen M.; Keith Barbara R.; Gustafson Kathryn E.; George Linda K.; Kinney Thomas R. 《Canadian Metallurgical Quarterly》1994,62(4):856
Rates of poor psychological adjustment of children with sickle cell disease remained relatively constant over initial and follow-up assessment points. 50 children (aged 7–12 yrs) and their mothers completed the initial protocol. 30 children completed the follow-up plus 5 additional children and their mothers. These Ss were aged 7–24 yrs at follow-up. With initial levels of adjustment controlled, children's strategies for coping with pain accounted for a significant increment in child-reported symptoms and mother-reported internalizing behavior problems at follow-up beyond the contribution of illness and demographic parameters and follow-up interval. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
14.
Analysis of simian hemorrhagic fever virus (SHFV) subgenomic RNAs, junction sequences, and 5' leader
Full-length simian hemorrhagic fever virus (SHFV) genome RNA (about 15 kb in length) and six subgenomic RNAs, ranging in size from 0.65 to 4.7 kb, were detected by Northern blot hybridization in MA104 cytoplasmic extracts with a 3' genomic antisense probe. The 5' regions of the two smallest subgenomic RNAs (RNAs 6 and 7) were cloned and sequenced. Sequence analysis indicated that these two RNAs contained a common 5' leader sequence joined to the subgenomic RNA bodies via a highly conserved junction sequence; the junction sequence of RNA 7 was 5'-TTAACC-3', while that of RNA 6 was 5'-TCAACC-3'. The complete 5' leader sequence (208 nt) was obtained from genomic RNA. The genomic 5' junction sequence is identical to that of RNA 7. Northern blot hybridization with an antisense 5' leader probe confirmed the presence of the complete leader sequence in all six species of subgenomic RNA. In its virion morphology, genome size, gene order, and replication strategy, SHFV is most similar to viruses such as equine arteritis virus, lactate dehydrogenase-elevating virus, and Lelystad virus/porcine respiratory and reproductive syndrome virus. 相似文献
15.
This study tried to show the contributory role of ions (cations and anions) to great contrast in the goitre prevalence between Bassa and Jos Local Government Areas, both of Plateau State, Nigeria. In pursuance of this, the concentration of cations (Ca++, Fe++, K+, Mg++, Na+, & Zn++) and anions (C1-, F, I-, & NO-3) in soil and drinking water in the two LGAs were determined and their results compared and correlated with the goitre prevalence of these areas. It was observed that both Bassa and Jos LGAs have very low but similar amounts of iodide ions in their soils. Besides, Bassa LGA contained more ions in both soil and drinking water than Jos LGA. In conclusion, the results appear to suggest that the higher ion contents of both soil and drinking water in Bassa LGA exacerbated the coexisting low iodide condition of the LGA, thus resulting in the higher goitre prevalence found in the LGA. 相似文献
16.
Metabolism and biochemical effects of 3,3',4,4'-tetrachlorobiphenyl in pregnant and fetal rats 总被引:1,自引:0,他引:1
DC Morse EK Wehler M van de Pas AT de Bie PJ van Bladeren A Brouwer 《Canadian Metallurgical Quarterly》1995,95(1-2):41-56
The metabolism and distribution of a single oral dose of 25 mumol 14C-labelled 3,3',4,4'-tetrachlorobiphenyl (14C-TCB) were investigated in pregnant female Wistar rats and their fetuses. TCB was administered on day 13 of gestation and the elimination was followed for 7 days. Non-pregnant rats were treated similarly for comparison. Fecal elimination of 14C-TCB derived radioactivity was significantly lower in pregnant rats than in non-pregnant rats. The major metabolite found in adult liver and plasma, placental tissue, whole fetuses and fetal plasma was 3,3',4',5-tetrachloro-4-biphenylol (4-OH-TCB). Tissue levels (liver, abdominal fat, skin, skeletal muscle, kidney and plasma) of 14C-TCB-derived radioactivity declined by 65-85% over a 7-day period following administration in the adult animals. However, 14C-TCB-derived radioactivity accumulated more than 100-fold in the fetuses over the same time period, and GC/MS analysis revealed that the fetal accumulation in radioactivity was due primarily to 4-OH-TCB, and not the parent compound. On day 20 of gestation, concentrations of 4-OH-TCB were 14 times greater in fetal plasma than maternal plasma. Treatment with 14C-TCB significantly reduced plasma thyroxine levels by at least 28% up to 7 days after administration in non-pregnant animals and up to 4 days after administration in pregnant rats (31% decrease). By 7 days after administration plasma thyroxine levels had returned to control levels in the TCB-treated pregnant rats. However, fetal plasma thyroxine levels were significantly decreased by 35% in fetuses from 14C-TCB-treated dams 7 days after TCB administration. Hepatic microsomal ethoxyresorufin-O-deethylase (EROD) activity was significantly induced in TCB-treated dams relative to controls at 4 and 7 days after administration, while no EROD activity was detected in hepatic microsomes from control or TCB treated fetal rats at day 20 of gestation. These data suggest that hydroxylated metabolites of polychlorinated biphenyls may play a role in the development toxicity of these compounds. 相似文献
17.
EK Khusnutdinova TV Viktorova IM Khidiiatova RI Fatkhlislamova TE Ivashchenko 《Canadian Metallurgical Quarterly》1997,33(9):1291-1296
Data on allelic polymorphism of MET and D7S23 DNA loci linked to the human cystic fibrosis gene studied in three Bashkir ethnic groups and some Volga-Ural populations (Tartars, Maris, Mordovians, Udmurts, Chuvashs, and Komis) are presented. Udmurts were found to be substantially different from Bashkirs, Tartars, Mordovians, and Chuvashs by the allele frequency distribution observed for MET, while Komis and Bashkirs differed by this parameter from Mordovians and Maris. Comparative analysis of restriction fragment length polymorphism (RFLP) at the D7S23 locus revealed statistically significant differences in genotype frequencies between Bashkirs of the Arkhangel' skii region and populations of Mordva and Udmurtia. In this respect, the Mordovian population appeared to be notably different from the populations of Bashkortostan, Tatarstan, Marii-El, Udmurtiya, Chuvashiya, and Komis. Genetic distances were calculated and corresponding dendrograms were constructed on the basis of data on Met-H, CS.7, and the ApoB locus hypervariable region allelic frequencies. Three ethnogeographic Bashkir groups belonging to one tree branch were found to be closely related to the populations of Tartars, Maris, Udmurts, and Chuvashs and substantially different from Komis and Mordovians. Thus, the position of Volga-Ural populations on the dendrogram corresponds to the degree of relationship between the Finno-Ugric and Turkic populations, confirming the usefulness of DNA polymorphism analysis for the study of the genetic structure of populations. 相似文献
18.
This study demonstrates how the common pharmaceutical wetting agent sodium dodecyl sulfate (SDS) increases the absorption of drugs and peptides across the human intestinal epithelium. First, an assay that could follow the reversible and irreversible time-dependent effects of SDS on the permeability of Caco-2 cell monolayers with high reproducibility was developed. SDS (0.40 mM) exposure for 20 min resulted in reversible absorption enhancement of mannitol (M(r), 182 g/mol), 1-deamino-8-D-arginine-vasopressin (M(r), 1071 g/mol), and polyethylene glycol (M(r), 4000 g/mol). A longer (2 h) exposure to SDS resulted in irreversible absorption enhancement. Second, transepithelial electrical resistance measurements (TEER) together with fluorescence and transmission electron microscopy were used to study the effects of SDS on epithelial integrity, cell membranes, intracellular calcium concentration, cytoskeleton, and tight junctions. The effect of SDS (0.40 mM) on epithelial integrity was immediate. A significant decrease in transepithelial electrical resistance measurements was obtained with 1 min after exposure to SDS that was concomitant with increases in the permeability of the apical cell membranes and intracellular calcium concentration. SDS shortened the microvilli of the cells and produced apical (but not basolateral) membrane wounds, actin disbandment, disorganization of the terminal web, and structural separation of the tight junctions. The absorption enhancement was not reduced after repair of the apical cell membranes, indicating that SDS enhances drug and peptide absorption across the intestinal epithelium by the paracellular pathway. 相似文献
19.
WJ Cho EK Kim MJ Park SU Choi CO Lee SH Cheon BG Choi BH Chung 《Canadian Metallurgical Quarterly》1998,6(12):2449-2458
In this study a series of 3-arylisoquinoline derivatives were synthesized and cytotoxicity against human melanoma tumor cell evaluated, and a three dimensional quantitative structure-activity relationship was investigated using the comparative molecular field analysis (CoMFA). The results suggested that the electrostatic, steric and hydrophobic factors of 3-arylisoquinolines were strongly correlated with the antitumor activity. Considerable predictive ability (cross-validated r2 as high as 0.721) was obtained through CoMFA. 相似文献
20.
BACKGROUND: Patients with cerebellar hematomas may appear stable but may worsen suddenly. Whether certain clinical or CT scan findings predict worsening is not known. METHODS: We reviewed clinical and neuroimaging data in 72 patients with cerebellar hematomas at the Mayo Clinic from 1973 through 1993 to identify predictive features for neurologic deterioration. Patients presenting in coma and patients with vascular malformations or malignancies were excluded. Data were analyzed using chi-square or Fisher's exact test, with calculation of odds ratios with 95% confidence intervals. Multivariate logistic regression analysis was performed on appropriate variables. RESULTS: Thirty-three patients (46%) deteriorated, with a decrease in level of consciousness, new brainstem signs, or worsened motor response on the Glasgow Coma Scale. Clinical and neuroradiologic predictors for neurologic deterioration at p < 0.05 were admission systolic blood pressure greater than 200 mm Hg, pinpoint pupils and abnormal corneal or oculocephalic reflexes, hemorrhage extending into the vermis, hematoma size more than 3 cm in diameter, brainstem distortion, intraventricular hemorrhage, upward herniation, and acute hydrocephalus. Multivariate analysis demonstrated that hemorrhage located in the vermis (p = 0.03) and acute hydrocephalus (p = 0.0006) on admission CT scanning independently predicted deterioration. CONCLUSION: Patients with a cerebellar vermian hematoma or acute hydrocephalus are at high risk for neurologic deterioration. These patients should be carefully monitored and are more likely to require consideration for neurosurgical intervention. 相似文献