全文获取类型
收费全文 | 501篇 |
免费 | 4篇 |
专业分类
综合类 | 2篇 |
化学工业 | 24篇 |
金属工艺 | 2篇 |
机械仪表 | 1篇 |
建筑科学 | 5篇 |
轻工业 | 9篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 9篇 |
一般工业技术 | 5篇 |
冶金工业 | 438篇 |
自动化技术 | 7篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 4篇 |
2011年 | 2篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
1999年 | 18篇 |
1998年 | 129篇 |
1997年 | 87篇 |
1996年 | 56篇 |
1995年 | 30篇 |
1994年 | 24篇 |
1993年 | 26篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 12篇 |
1976年 | 27篇 |
1975年 | 3篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有505条查询结果,搜索用时 15 毫秒
41.
LT Goodnough 《Canadian Metallurgical Quarterly》1996,7(2):212-220
The appropriate use of blood transfusions remains variable among health-care institutions and patient populations. Transfusion practices are discussed in this article in relation to medical practice guidelines and utilization review. Specific transfusion practices in the settings of intensive care, orthopedic surgery, and open heart surgery are reviewed. A new, promising approach to improving transfusion outcomes is the use of transfusion algorithms. Transfusion algorithms may prove especially useful if they incorporate point-of-care testing that is both physiologic and patient-specific for transfusion decisions. Transfusion algorithms are discussed and data presented for cardiac surgical adults. 相似文献
42.
KH Yeh MT Lin DT Lin JL Tang LT Lui JF Lin YS Chang AL Cheng SC Yu KJ Chang YC Chen 《Canadian Metallurgical Quarterly》1998,49(3):237-244
BACKGROUND: Epidemiologic studies are necessary to determine the prevalence of allergic diseases. This varies widely depending on allergen preparations and patients studied. OBJECTIVE: To investigate the prevalence of atopic disease, skin test reactivity, total and specific IgE to common allergens, and other variables in a sample of students from Málaga, southern Spain. METHODS: Three hundred sixty-five students (age 17.9 +/- 1.18) were interviewed by an allergist. Skin prick tests were performed with Dermatophagoides pteronyssinus, Artemisia vulgaris, Plantago lanceolata, Chenopodium album, Olea europaea, Phleum pratense, Parietaria judaica, Cynodon dactylon, Alternaria tenuis, and cat dander. Total and specific IgE to D. pteronyssinus, Olea, and Parietaria were determined. RESULTS: Of all subjects studied, 19.9% suffered from rhinoconjunctivitis, 4.1% rhinoconjunctivitis plus asthma, 3.1% asthma alone, and 0.8% atopic dermatitis; 46.4% had a positive skin test to at least one allergen (28.2% to D. pteronyssinus, 20.4% to Olea, 13.8% to Phleum); and 43% had total IgE > 100 kU/L and 44.7% a family history of atopy. Allergic symptoms were strongly associated with skin test positivities and family allergic history. Patients with asthma or skin prick test positive had higher total IgE values than others (P < .01). There was a significant correlation between specific IgE values and wheal size in skin test. CONCLUSIONS: Our findings confirm the high prevalence of atopic diseases, and the close relationship of skin tests reactivity (or presence of specific IgE) to allergens with symptoms of asthma and rhinitis. The presence of a family history of allergic diseases influences the development of positive skin tests and atopic illness. Dermatophagoides pteronyssinus and pollen of Olea europaea were found to be the most common allergens. 相似文献
43.
AJ Bailer LT Stayner NA Stout LD Reed SJ Gilbert 《Canadian Metallurgical Quarterly》1998,55(7):485-489
Recent advancements in laparoscopic surgery have made laparoscopic splenectomy possible. We retrospectively compared the outcomes of laparoscopic versus open splenectomy in patients with idiopathic thrombocytopenic purpura (ITP) or beta-thalassemia. From July 1993 to July 1997, 52 patients (ITP, 43 cases; beta-thalassemia, 9 cases) underwent either laparoscopic (30 patients, 9 men, 21 women; average age, 36.9 years) or conventional open splenectomy (22 patients, 5 men, 17 women; average age, 34.3 years). The two groups were similar in terms of sex, age, diagnosis, duration of disease, preoperative platelet count, and spleen size. The mean surgical time, estimated amount of blood loss, duration of postoperative recovery, analgesic usage, and complications were compared between the two groups. Laparoscopic splenectomy was successful in 29 (97%) of the 30 patients. The mean surgical time in the laparoscopy group was longer than in the open splenectomy group (190.6 vs 113.9 minutes, p < 0.01). The laparoscopy group had earlier postoperative oral intake (15.2 vs 52.6 hours, p < 0.01), less usage of analgesics (meperidine 50 mg/unit, 1.1 vs 2.8 units, p < 0.01) and a shorter postoperative hospital stay (4.1 vs 6.8 days, p < 0.01). The estimated blood loss, incidence of accessory spleen, surgical complication rate, and recurrence rate of thrombocytopenia were similar in the two groups. Our findings show that laparoscopic splenectomy in patients with ITP or beta-thalassemia is as safe as the open approach. While laparoscopy required a longer surgical time, the recovery period was shorter, analgesic use was less, and physical discomfort was less severe. 相似文献
44.
SS Martin DW Rose AR Saltiel A Klippel LT Williams JM Olefsky 《Canadian Metallurgical Quarterly》1996,137(11):5045-5054
Rat-1 fibroblasts overexpressing the human insulin receptor undergo rapid actin rearrangement in response to insulin. Breakdown of stress fibers present in quiescent cells is followed by transient membrane ruffling and a return of stress fibers. We investigated the signaling pathways that mediate this insulin-stimulated reorganization of the actin cytoskeleton, which was visualized with rhodamine-phalloidin. Treatment of cells with the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor wortmannin prevented insulin action at the preliminary step of stress fiber breakdown. Cellular microinjection of a polyclonal antibody directed against the p85 subunit of PI3-kinase as well as a purified recombinant p85-SH2 domain protein also inhibited actin reorganization. Transient expression of a constitutively active form of PI3-kinase (p110*) was sufficient to cause both stress fiber breakdown and membrane ruffling in the absence of insulin. Microinjection of a polyclonal anti-Shc antibody or dominant negative N17-Ras protein did not affect actin dynamics, and although constitutively active V12-Ras caused modest cytoskeletal reorganization, this effect was blocked by pretreatment with wortmannin. In summary, activation of PI3-kinase is necessary and sufficient to stimulate actin rearrangement, indicating that PI3-kinase may initiate the only signaling cascade required for insulin to induce cytoskeletal restructuring. 相似文献
45.
MJ Marino ST Rouse AI Levey LT Potter PJ Conn 《Canadian Metallurgical Quarterly》1998,95(19):11465-11470
Evidence suggests that cholinergic input to the hippocampus plays an important role in learning and memory and that degeneration of cholinergic terminals in the hippocampus may contribute to the memory loss associated with Alzheimer's disease. One of the more prominent effects of cholinergic agonists on hippocampal physiology is the potentiation of N-methyl-D-aspartate (NMDA)-receptor currents by muscarinic agonists. Here, we employ traditional pharmacological reagents as well as m1-toxin, an m1 antagonist with unprecedented selectivity, to demonstrate that this potentiation of NMDA-receptor currents in hippocampal CA1 pyramidal cells is mediated by the genetically defined m1 muscarinic receptor. Furthermore, we demonstrate the colocalization of the m1 muscarinic receptor and the NR1a NMDA receptor subunit at the electron microscopic level, indicating a spatial relationship that would allow for physiological interactions between these two receptors. This work demonstrates that the m1-muscarinic receptor gene product modulates excitatory synaptic transmission, and it has important implications in the study of learning and memory as well as the design of drugs to treat neurodegenerative diseases such as Alzheimer's. 相似文献
46.
We investigated interrelationships among stimulus classes established in matching-to-sample and sequence-production tasks. The analysis focused on the matching and sequencing of quantities, numerals, and arbitrary forms in two individuals with mental retardation. The basic protocol involved: (a) establishing both matching and sequencing performances with some stimuli, (b) training sequencing with a new set of stimuli and assessing whether new matching performances emerged, and (c) training matching with a new set of stimuli and assessing whether new sequencing emerged. The results showed that sequence training did not readily lead to new matching performances, unlike prior research with college students. In contrast, training in matching to sample yielded emergent sequence production; these data support prior studies involving children and adults without developmental disabilities. The results extend prior stimulus class research and suggest an important role for stimulus control processes in the production of generative numeric performances. 相似文献
47.
AM M?ller LT Dalgaard F Pociot J Nerup T Hansen O Pedersen 《Canadian Metallurgical Quarterly》1998,41(12):1528-1531
Mutations in the hepatocyte nuclear factor-1alpha (HNF-1alpha) gene are the cause of maturity-onset diabetes of the young type 3 (MODY3), which is characterised by a severe impairment of insulin secretion and an early onset of the disease. Also at onset of diabetes some MODY patients show similar clinical symptoms and signs as patients with Type I (insulin-dependent) diabetes mellitus. The objective of this study was to estimate the prevalence of MODY3 patients misclassified as Type I diabetic patients. From a large population-based sample of unrelated Danish Caucasian Type I diabetic patients with an affected first degree relative, 39 patients (6.7%) who did not carry any high-risk HLA-haplotypes, i.e. DR3 or DR4 or both were examined by single-strand conformational polymorphism scanning and direct sequencing of the coding region and the minimal promoter of the HNF-1alpha gene. Four of the 39 Type I diabetic patients (10%) were identified as carrying mutations in the HNF-1alpha gene. One patient carried a missense mutation (Glu48Lys) in exon 1, two patients carried a missense mutation (Cys241Gly) in exon 4 and one patient carried a frameshift mutation (Pro291fsdelA) in exon 4. The mutations were all identified in heterozygous form, segregated with diabetes, and were not identified in 84 unrelated, healthy subjects. Furthermore, family history in three of the four families showed diabetes in four consecutive generations, suggestive of an autosomal dominant inheritance. In conclusion, about 10% of Danish diabetic patients without a high-risk HLA-haplotype, originally classified as having Type I diabetes could have diabetes caused by mutations in the HNF-1alpha gene. Clinical awareness of family history of diabetes and mode of inheritance might help to identify and reclassify these diabetic subjects as MODY3 patients. 相似文献
48.
N‐Substituted pyrrole derivatives with chiral side groups have been synthesized and electrochemically polymerized in acetonitrile containing tetrabutylammonium perchlorate (TBAClO4) and (S)‐(+)‐camphor‐10‐sulfonic acid ((S)‐(+)‐CSA) or (R)‐(?)‐camphor‐10‐sulfonic acid ((R)‐(?)‐CSA). The resulting N‐substituted polypyrrole films were characterized by cyclic voltammetry, infrared, Raman and X‐ray photoelectron (XPS) spectroscopies. XPS results demonstrated that the as‐grown polymer films are preferably doped by CSA anions when the monomer and the CSA anion have the same optical rotation dispersion (ORD). Furthermore, the conductivities of the polymers synthesized in the media containing CSA with the same ORD of the corresponding monomers were measured to be about 2–10 times higher than those of polymers obtained from electrolytes without CSA. Copyright © 2004 Society of Chemical Industry 相似文献
49.
M Sarr EJ Simoes T Murayi LT Figgs RC Brownson 《Canadian Metallurgical Quarterly》1998,95(12):663-669
BACKGROUND: Breast cancer is a major cause of morbidity and mortality in the United States (U.S.) and Missouri. In 1992, 3,915 new breast cancer cases were diagnosed and in 1995, 1,006 deaths from breast cancer were reported in Missouri. Although breast cancer incidence has increased in Missouri in the past 20 years, there are indications that early detection has also increased during the same period. Knowledge about which segments of the population have experienced the greatest increase in mammography screening rates helps in planning and implementation of breast cancer control programs at the state level. OBJECTIVES: Examine the prevalence and trends of lifetime mammography and 2-year mammography compliance in Missouri by age, race, and education from 1987 to 1995 and make predictions for the years 2000 and 2010. METHODS: We used data from the Missouri Behavioral Risk Factor Surveillance System (BRFSS), 1987 to 1995, to estimate the prevalence of ever having had a mammogram and compliance with mammography screening guidelines within two years by race, age, and education status among Missouri women over age 18. Using linear models, we regressed breast cancer screening prevalence estimates on time to obtain trends and predictions. RESULTS: Overall, African-American women were more likely to have had a lifetime mammogram than white women. However, we found a steady increase in the prevalence of ever having had a mammogram for all groups of women defined by age and education status, except among African Americans. Increase in the prevalence of ever having had a mammogram was much higher in women age 50 and older and slightly higher among women with a high school education or less. The average prevalence of 2-year mammography screening compliance was about 60% for all groups, a rate which did not significantly change between 1987 and 1995. By the year 2000, white women will have mammography rates equal to or higher than African-American women, and the majority of all women age 50 and older (98.3% to 100%) will have had a lifetime mammogram. CONCLUSION: Missouri target populations are predicted to attain Year 2000 National Health Objectives concerning lifetime mammography. Current efforts should be continued in order to maintain levels of mammography, particularly among African-American women. 相似文献
50.
I Fermo C Arcelloni G Mazzola A D'Angelo R Paroni 《Canadian Metallurgical Quarterly》1998,719(1-2):31-36
We have modified a high-performance liquid chromatographic (HPLC) procedure based on SBD-F (ammonium-7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate) pre-column derivatization to obtain an assay that is useful for routine clinical total plasma homocysteine (tHcy) analysis. The introduction of easily handled sodium borohydride instead of the traditional tri-n-butylphosphine in dimethylformamide as a reductant and a 14-min run-time using basic isocratic HPLC equipment are the more notable advantages. The addition of mercaptopropionylglycine as an internal standard contributed to improvements in the reproducibility of the assay, yielding within- and between-run precisions of 1.9 and 4% (C.V.), respectively. Reference values for fasting tHcy were 7.65+/-2.3 and 8.9+/-2.4 micromol/l, while post-methionine load gave tHcy levels of 19.9+/-5.5 and 26.8+/-5.5 micromol/l, for women and men, respectively (n=40). 相似文献