全文获取类型
收费全文 | 1191篇 |
免费 | 11篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 7篇 |
综合类 | 3篇 |
化学工业 | 104篇 |
金属工艺 | 7篇 |
机械仪表 | 19篇 |
建筑科学 | 32篇 |
能源动力 | 10篇 |
轻工业 | 20篇 |
水利工程 | 2篇 |
石油天然气 | 5篇 |
无线电 | 83篇 |
一般工业技术 | 71篇 |
冶金工业 | 778篇 |
原子能技术 | 2篇 |
自动化技术 | 62篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 26篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 24篇 |
2009年 | 25篇 |
2008年 | 29篇 |
2007年 | 31篇 |
2006年 | 23篇 |
2005年 | 18篇 |
2004年 | 21篇 |
2003年 | 19篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 16篇 |
1999年 | 39篇 |
1998年 | 244篇 |
1997年 | 149篇 |
1996年 | 104篇 |
1995年 | 35篇 |
1994年 | 53篇 |
1993年 | 34篇 |
1992年 | 5篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 15篇 |
1977年 | 17篇 |
1976年 | 36篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1205条查询结果,搜索用时 15 毫秒
31.
FC Sparks AG Wile KP Ramming HK Silver RW Wolk DL Morton 《Canadian Metallurgical Quarterly》1976,111(10):1057-1062
Antibody against a breast carcinoma antigen was present in patients with breast carcinoma and other cancer more often (P less than .05) than in normal women. The incidence of antibody in women with breast carcinoma correlated with the presence or absence of gross tumor, and the titer of antibody paralleled the clinical course. These results suggest importance of a host-immune response to breast carcinoma. Fifty-seven patients with stage II carcinoma of the breast were entered into a prospective randomized adjuvant chemoimmunotherapy program of cyclophosphamide, methotrexate, and fluorouracil, and BCG vaccine +/- an irradiated allogeneic tumor cell vaccine. After 24 months of study, metastases occurred in two patients (3.5%) and a new primary carcinoma developed in the contralateral breast in two others, for an overall treatment failure rate of 7%. Adjuvant chemoimmunotherapy can delay early recurrence. Long-term follow-up is needed to assess the significance of these results. 相似文献
32.
Edita Zubrytė Danutė Kaušpėdienė Romas Ragauskas Rima Binkienė Aušra Selskienė 《分离科学与技术》2020,55(16):2855-2868
ABSTRACT A non-hazardous groundwater treatment waste (GWTW) was examined as a low-cost sorbent for Pb(II) and Cu(II) ions. The content of the dominant elements in GWTW was as follows: 78% Fe2O3, 7.4% P2O5, 7.4% CaO and 5.2% SiO2. The removal of Pb(II) and Cu(II) was fast, and more than 67–95% of ions were accumulated by GWTW during the first 3 min. The sorption capacity of GWTW depends on solution pH, concentration and temperature. Equilibrium data fitted well with Langmuir–Freundlich and Langmuir-partition models. The inherently formed nano-adsorbent could be utilized for the treatment of water contaminated with Pb(II) and Cu(II) ions. 相似文献
33.
双向无粘结预应力混凝土井字梁结构施工中,采取在端头承压垫板上钻小孔定位无粘结筋、与群锚配套使用,省去铸铁喇叭管,简化了施工方法。 相似文献
34.
H Tsukamoto T Kurokawa K Hirata S Ishibashi HK Mishima 《Canadian Metallurgical Quarterly》1998,46(5):987-991
We investigated the effect of two isomers of retinoic acid (RA), all-trans RA and 9-cis RA, on the proliferation of Y79 human retinoblastoma cells. The two isomers inhibited the cell proliferation in a concentration-dependent manner. The IC50 for this inhibition by all-trans RA and 9-cis RA was 1.50 and 0.15 microM, respectively. The inhibitory effect of 9-cis RA on Y79 cell growth was observed within 24 hr, thereafter the cell number was gradually decreased. In contrast, no inhibition by all-trans RA of Y79 cell growth was observed within 24 hr, thereafter the cell number was slightly increased. In these cases, the cell viability at 4 days after the addition of 9-cis RA and all-trans RA was more than 90% and 95%, respectively. These results indicate that the two RA inhibit the proliferation of Y79 human retinoblastoma cells without inducing the cell death and that the effect of 9-cis RA on the inhibition of Y79 cell growth is much greater than that of all-trans RA. 相似文献
35.
36.
HK Biesalski C Hemmes M El Hanafy H Weiser H Zschaebitz E Stofft 《Canadian Metallurgical Quarterly》1996,126(4):973-983
A rat model was used to investigate whether high oral doses of vitamin A lead to fetal malformations and to what extent retinyl esters (RES) are transferred from the mother to the fetuses. Retinol and RES concentrations in plasma behave similarly in rats and humans. When high concentrations of vitamin A are administered, plasma retinol concentrations remain relatively constant, whereas plasma RES increased in parallel with the dose. To achieve an elevation from approximately 150 to > 1525 nmol x L(-1) in the experimental group before mating, female Ibm: RORO (spf) rats were fed a maintenance diet enriched with 15.2 x 10(3) retinol equivalents (RE) x kg(-1) at the start and increased stepwise to 52.5 x 10(3) for a total of 8 mo. A parallel subgroup was maintained to measure progress in experimental rats without interference by blood taking. Rats of the control group received the basal diet analyzed to contain 4.5 x 10(3) RE x kg(-1). Before mating the mean body weights of experimental and control rats were not significantly different. All-trans, 13-cis, 4-oxo-all-trans and 5,6-epoxy-all-trans retinoic acid (RA) concentrations were determined in maternal and fetal plasma. With high vitamin A intake, 4-oxo- and 5,6-epoxy RA concentrations were significantly higher in the fetuses than in their mothers. Although these high intakes of vitamin A by the rat dams resulted in high maternal and fetal plasma concentrations of vitamin A and its metabolites, fetal malformations were not observed. This may be due to the fact that circulating RES are not teratogenic and that after crossing the placental barrier, they are stored mainly in fetal liver. 相似文献
37.
HK Najm GS Van Arsdell S Watzka L Hornberger JG Coles WG Williams 《Canadian Metallurgical Quarterly》1998,116(6):905-913
OBJECTIVE:The objective was to explore the best management algorithm for atrioventricular septal defect in conjunction with tetralogy of Fallot. METHODS: We reviewed the cases of 38 children referred to our division (March 1981-August 1997) who had atrioventricular septal defect associated with tetralogy of Fallot; 32 (84%) had Down syndrome. Twenty-one received initial palliation with a systemic-to-pulmonary artery shunt; of these, 2 (9.5%) died before complete repair. Thirty-one children underwent complete repair; 14 of these (45%) had undergone initial palliation (mean age at shunt 20 +/- 24 months). Right ventricular outflow obstruction was relieved by a transannular patch in 22 (71%); 14 (64% of 22) had a monocuspid valve inserted. Four required an infundibular patch. RESULTS: Two children (6.4%) died early after repair; 1 had undergone previous palliation. Patients with palliation underwent repair at an older age (78 vs 36 months), required longer ventilatory support (8 vs 4 days) and inotropic support (8 vs 4 days), and had longer intensive care stays (11 vs 6 days) and hospital stays (24 vs 15 days). Eleven children (35%) underwent reoperation, 7 (58%) for right ventricular outflow reconstruction and pulmonary arterioplasty. Reoperation was more frequent in the palliation group than in the primary operation group (64% vs 12%). The single late death was related to a reoperation in the palliation group. CONCLUSIONS: Atrioventricular septal defect with tetralogy of Fallot can be repaired with a low mortality rate. Initial palliation with a shunt resulted in a more complex postoperative course and a higher reoperative rate. Primary repair is superior to initial palliation with later repair. 相似文献
38.
Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, Ontario. The combination of logging, smelting, fires and erosion resulted in an unusual anthropogenic ecosystem of denuded barren land with lifeless lakes, or a micro-desert. Since the 1970s, however, the concerted efforts made to reduce the emissions and rehabilitate parts of the degraded ecosystem have resulted in improvements in water quality, and recoveries in phytoplankton, zooplankton, zoobenthos and fish communities but have had little impact on toxic metal concentrations in many lakes. We show that most of the catchments in the Sudbury basin have become saturated with Cu and Ni, and some with Zn and Pb. It is estimated that mobilization of metals stored in soils and glacial overburden by surface runoff, groundwater drainage and wind re-working of tailings can sustain the high concentrations of Cu and Ni in many lakes for well over 1000 years. Strategies to immobilize the pollutant metals in the watershed rather than further emission controls may be required for dealing with high levels of toxic metals in surface waters of the saturated ecosystems. 相似文献
39.
Treatment with beta-blockers has been reported to be associated with the development of hypertriglyceridemia. The etiology, even the existence, of this phenomenon is controversial. The purpose of our study was to examine whether the nonselective beta-blocker propranolol causes hypertriglyceridemia in the rat and whether its action is mediated by the modulation of lipoprotein lipase (LPL) messenger RNA (mRNA) accumulation or activity. LPL activity was assayed in fresh tissue by incubation with tritiated triglycerides. LPL mRNA was quantified in total RNA by slot-blot analysis using a mouse LPL complementary DNA probe. We have conducted three series of experiments in unanaesthetized rats in order to study the effects of different single doses of propranolol (1.5 to 6 mg i.p.) and different durations of treatment (15 min to 4 wk). We measured triglyceride and cholesterol levels in plasma as well as the LPL activity and mRNA levels in the heart and adipose tissue before and after propranolol administration. In these experiments we did not find any significant decrease in either the activity or the amount of mRNA of lipoprotein lipase nor was there any change in plasma lipids following treatment. Our results lead us to the conclusion that the nonselective beta-blocker propranolol affects neither the activity nor the mRNA level of LPL in the rat. 相似文献
40.
HK Atrash LT Strauss JS Kendrick FE Skjeldestad YW Ahn 《Canadian Metallurgical Quarterly》1997,89(4):512-518
The present study was conducted to elucidate the effects of tirilazad mesylate (U-74006F), a potent inhibitor of lipid peroxidation, on vessel diameter, capillary perfusion, and contractile function of rat cremaster muscle during a 90-minute reperfusion period that followed 4 hours of warm ischemia. Two groups of 32 animals were treated with either 3 mg/kg U-74006F or the vehicle (citrate buffer) alone 30 minutes before ischemia, 90 minutes after ischemia, and immediately before reperfusion. With use of intravital videomicroscopy, the internal luminal diameters of preselected vessels were measured prior to ischemia and during reperfusion. The area that filled with fluorescein was determined at 15-minute intervals for as long as 90 minutes of reperfusion, and contractile function was examined in vitro in an organ bath at that point. In the U-74006F group, after 90 minutes of reperfusion the vessel diameters returned completely to baseline and the diameters of all three categories of vessels at every time point from 10 to 90 minutes of reperfusion had significantly more rapid recovery than the controls. Although some evidence of more rapid fluorescence was noted in the U-74006F group, the two groups did not differ significantly at any time period of reperfusion. In response to tetanic stimulation, the muscles treated with U-74006F had a significantly greater contractile force at all stimulation frequencies than the control muscles. Our findings indicate that pretreatment with U-74006F can effectively decrease the rise of vascular resistance and preserve the contractile function of skeletal muscle during early reperfusion, thereby attenuating ischemia-reperfusion injury. 相似文献