全文获取类型
收费全文 | 2585篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 4篇 |
化学工业 | 52篇 |
金属工艺 | 6篇 |
机械仪表 | 5篇 |
建筑科学 | 6篇 |
能源动力 | 6篇 |
轻工业 | 36篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 51篇 |
一般工业技术 | 48篇 |
冶金工业 | 2317篇 |
原子能技术 | 2篇 |
自动化技术 | 53篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 14篇 |
2010年 | 4篇 |
2009年 | 14篇 |
2008年 | 4篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 13篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 81篇 |
1998年 | 772篇 |
1997年 | 442篇 |
1996年 | 253篇 |
1995年 | 151篇 |
1994年 | 126篇 |
1993年 | 150篇 |
1992年 | 26篇 |
1991年 | 25篇 |
1990年 | 29篇 |
1989年 | 28篇 |
1988年 | 38篇 |
1987年 | 37篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 18篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 45篇 |
1976年 | 97篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有2591条查询结果,搜索用时 46 毫秒
151.
G He J Hart OS Kim GL Szot CT Siegel JR Thistlethwaite KA Newell 《Canadian Metallurgical Quarterly》1999,67(1):131-137
Studies were performed to determine the effects of PTH and related compounds on phosphatidylcholine (PC) hydrolysis in UMR-106 cells and the pathway by which the PTH effects occurred. The responses were compared with those of phorbol 12,13-dibutyrate (PDBu). Both bovine PTH-(1-34) [bPTH-(1-34)] and PDBu stimulated PC hydrolysis within 10 min. Significant effects were elicited by concentrations of 0.3-1 nM bPTH-(1-34) and 5 nM PDBu. Dose-dependent increases were seen at higher concentrations of both compounds, however, the response to bPTH-(1-34) was reduced at 30 nM. Bovine or human PTH-(1-34) and human PTH-related peptide-(1-34) [hPTHrP-(1-34)] were equipotent in their effects, whereas bovine [Nle(8,18)Tyr34]PTH-(3-34) amide [bPTH-(3-34)] and hPTH-(1-31) amide [hPTH-(1-31)] were less potent than bPTH-(1-34). bPTH-(3-34) did not antagonize the effects of bPTH-(1-34). Down-regulation of protein kinase C isozymes by 24-h treatment with PDBu completely prevented the stimulatory effect of PDBu on PC hydrolysis, but did not significantly affect the stimulatory effect of bPTH-(1-34). Both bPTH-(1-34) and PDBu stimulated transphosphatidylation of PC, indicating a phospholipase D-stimulated mechanism. The results suggest that in the UMR-106 cell line PTH can stimulate activation of PLD by a mechanism other than through protein kinase C. 相似文献
152.
Else Breval Maria Klimkiewicz Chiping Wang Joseph P. Dougherty Ann Crespi 《Journal of the American Ceramic Society》2007,90(8):2664-2666
Annealing of a sintered pellet of Pb0.9175 La0.055 Zr0.975 Ti0.025 O3 in air without any precautions against PbO evaporation results in a core–shell microstructure with a solid PLZT core and a porous ZrO2 -rich shell. 相似文献
153.
SJ Lee KM Kuntz MM Horowitz PB McGlave JM Goldman KA Sobocinski J Hegland C Kollman SK Parsons MC Weinstein JC Weeks JH Antin 《Canadian Metallurgical Quarterly》1997,127(12):1080-1088
BACKGROUND: Chronic myelogenous leukemia (CML) is an indolent but ultimately fatal disease. Because the natural history of CML varies and quality of life with CML may be excellent until shortly before death, deciding whether and when to pursue unrelated donor bone marrow transplantation is often difficult. OBJECTIVE: To compare early transplantation, delayed transplantation, and no transplantation for patients with chronic-phase CML on the basis of discounted, quality-adjusted life expectancy. DESIGN: A markov model comparing different strategies was constructed. This model considers patient age, quality of life, risk aversion, and the competing risks for CML progression and transplant toxicity. SETTING: Therapeutic decision at the time of diagnosis of CML. PATIENTS: The base case is a 35-year-old patient with intermediate-prognosis CML. Younger and older patients with better and worse prognoses are also evaluated. INTERVENTION: Early transplantation, delayed transplantation, and no transplantation. MEASUREMENTS: Quality-adjusted, discounted life expectancy. RESULTS: For patients with newly diagnosed CML, transplantation within the first year provides the greatest quality-adjusted expected survival, although this benefit decreases with increasing patient age. For a 35-year-old patient with intermediate-prognosis CML, transplantation within the first year results in 53 more discounted, quality-adjusted years of life expectancy than does no transplantation. This finding is robust even with varying baseline assumptions. CONCLUSIONS: These results support the use of early unrelated donor bone marrow transplantation for most patients with CML. 相似文献
154.
155.
Glaucoma reportedly affects motion perception. As an initial step in characterizing glaucoma-induced changes in the motion system, we determined the range of temporal frequencies that the motion system could process. A noise-masking paradigm was used to measure contrast energy thresholds of 26 glaucoma patients at various stages of the disease and 16 age-similar subjects with normal vision. Using a sinusoidal stimulus, thresholds were measured for the discrimination of motion direction and for the stimulus embedded within a pattern of dynamic spatial noise. The noise was filtered to contain only low spatial frequencies, and the temporal-frequency spectrum of the noise was manipulated across conditions to derive the temporal filter shape of the most efficient motion sensor. The results show that the range of temporal frequencies processed by the motion system is diminished in the glaucoma group. The filters of the glaucoma subjects have reduced bandwidths compared with the normal-vision group. In addition, the upper cut-off frequency of the filters of the glaucoma subjects is correlated with stage of disease as indexed by the mean deviation of the Humphrey Visual Field Analyzer program 24-2, as well as the cup-to-disk ratio. 相似文献
156.
157.
158.
159.
KA Keay LJ Crowfoot NS Floyd LA Henderson MJ Christie R Bandler 《Canadian Metallurgical Quarterly》1997,762(1-2):61-71
Differentiating the binding properties of applied lectins should facilitate the selection of lectins for characterization of glycoreceptors on the cell surface. Based on the binding specificities studied by inhibition assays of lectin-glycan interactions, over twenty Gal and/or GalNAc specific lectins have been divided into eight groups according to their specificity for structural units (lectin determinants), which are the disaccharide as all or part of the determinants and of GalNAc alpha 1-->Ser (Thr) of the peptide chain. A scheme of codes for lectin determinants is illustrated as follows: (1) F (GalNAc alpha 1-->3GalNAc), Forssman specific disaccharide--Dolichos biflorus (DBL), Helix pomatia (HPL) and Wistaria floribunda (WFL) lectins. (2) A (GalNAc alpha 1-->3 Gal), blood group A specific disaccharide--Codium fragile subspecies tomentosoides (CFT), Soy bean (SBL), Vicia villosa-A4 (VVL-A4), and Wistaria floribunda (WFL) lectins. (3) Tn (GalNAc alpha 1-->Ser (Thr) of the protein core)--Vicia villosa B4 (VVL-B4), Salvia sclarea (SSL), Maclura pomifera (MPL), Bauhinia purpurea alba (BPL) and Artocarpus integrifolia (Jacalin, AIL). (4) T (Gal beta 1-->3GalNAc), the mucin type sugar sequences on the human erythrocyte membrane(T alpha), T antigen or the disaccharides at the terminal nonreducing end of gangliosides (T beta)--Peanut (PNA), Bauhinia purpurea alba (BPL), Maclura pomifera (MPL), Sophora japonica (SJL), Artocarpus lakoocha (Artocarpin) lectins and Abrus precatorius agglutinin (APA).(5) I and II (Gal beta 1-->3(4)GlcNAc)--the disaccharide residue at the nonreducing end of the carbohydrate chains derived from either N- or O-glycosidic linkage--Ricinus communis agglutinin (RCA1), Datura stramonium (TAL, Thorn apple), Erythrina cristagalli (ECL, Coral tree), and Geodia cydonium (GCL). (6) B (Gal alpha 1-->3Gal), human blood group B specific disaccharide--Griffonia(Banderiaea) simplicifolia B4 (GSI-B4). (7) E (Gal alpha 1-->4Gal), receptors for pathogenic E. coli agglutinin, Shiga toxin and Mistletoe toxic lectin-I (ML-I) and abrin-a. 相似文献
160.
SB Mannheimer KA Sepkowitz M Stoeckle CR Friedman A Hafner LW Riley 《Canadian Metallurgical Quarterly》1997,1(4):319-325
The discovery of neuroendocrine differentiation in hormone-refractory prostatic adenocarcinoma has opened a potentially new therapeutic approach in this group of patients with a poor prognosis and few effective therapy modalities. Based on previous findings of increased uptake of 11C-5-hydroxytryptophan (11C-5-HTP) in neuroendocrine tumours using the PET technique, this tracer was applied in the study of 10 patients with metastatic hormone-refractory prostatic adenocarcinoma. In three patients, the study was repeated after treatment. An increased uptake of 11C-5-HTP was observed in all investigated skeletal lesions, although the magnitude of the uptake was moderate. The difference between the standard uptake values (SUV) in normal bone and metastatic lesions was significant (p < 0.001). A kinetic analysis of the uptake of 11C-5-HTP demonstrates an increase during the first minutes followed by a wash-out and a stabilization of the tissue/blood ratio at about 2. The Patlak plots demonstrated a gradual increase in the transport rate during the first 20 to 30 min, after which a constant level was observed. The SUV varied between patients and between lesions over time and treatment. The uptake of 11C-5-HTP discriminates metastatic lesions from normal bone and may thus aid in the diagnosis and, potentially, in treatment monitoring of metastatic hormone-refractory prostatic adenocarcinoma. Uptake kinetics are characterized by a wash-out and cannot alone be used as proof of neuroendocrine differentiation in hormone-refractory prostatic adenocarcinoma. 相似文献