全文获取类型
收费全文 | 6720篇 |
免费 | 73篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 39篇 |
综合类 | 3篇 |
化学工业 | 398篇 |
金属工艺 | 53篇 |
机械仪表 | 47篇 |
建筑科学 | 89篇 |
矿业工程 | 7篇 |
能源动力 | 39篇 |
轻工业 | 326篇 |
水利工程 | 16篇 |
石油天然气 | 6篇 |
无线电 | 201篇 |
一般工业技术 | 367篇 |
冶金工业 | 4784篇 |
原子能技术 | 17篇 |
自动化技术 | 404篇 |
出版年
2022年 | 18篇 |
2021年 | 32篇 |
2020年 | 32篇 |
2019年 | 36篇 |
2018年 | 37篇 |
2017年 | 38篇 |
2016年 | 34篇 |
2015年 | 32篇 |
2014年 | 48篇 |
2013年 | 122篇 |
2012年 | 79篇 |
2011年 | 111篇 |
2010年 | 89篇 |
2009年 | 77篇 |
2008年 | 102篇 |
2007年 | 112篇 |
2006年 | 98篇 |
2005年 | 66篇 |
2004年 | 68篇 |
2003年 | 72篇 |
2002年 | 68篇 |
2001年 | 46篇 |
2000年 | 55篇 |
1999年 | 204篇 |
1998年 | 1442篇 |
1997年 | 812篇 |
1996年 | 520篇 |
1995年 | 285篇 |
1994年 | 246篇 |
1993年 | 316篇 |
1992年 | 61篇 |
1991年 | 76篇 |
1990年 | 75篇 |
1989年 | 97篇 |
1988年 | 89篇 |
1987年 | 77篇 |
1986年 | 62篇 |
1985年 | 74篇 |
1984年 | 26篇 |
1983年 | 38篇 |
1982年 | 56篇 |
1981年 | 51篇 |
1980年 | 56篇 |
1979年 | 27篇 |
1978年 | 30篇 |
1977年 | 120篇 |
1976年 | 241篇 |
1975年 | 32篇 |
1972年 | 12篇 |
1963年 | 13篇 |
排序方式: 共有6796条查询结果,搜索用时 0 毫秒
41.
42.
We have investigated the effects of the neutral endopeptidase inhibitor, SCH 42354, on the vasoreactivity of atrial natriuretic peptide (ANP) in rat isolated pulmonary resistance vessels (PRV) and isolated perfused lungs (IPL). PRV (n = 37) were mounted onto the jaws of a myograph and precontracted with PGF2alpha (100 mu M). Concentration-responses to ANP (0.17 to 340 nM) were determined before and after the addition of SCH 42354 (10, 30 and 100 nM). Each concentration of SCH 42354 caused a significant increase in potency (- log EC50) of ANP in isolated PRV. Lungs from normoxic rats (n = 13) were isolated and perfused with whole blood. An increase in pulmonary artery pressure was achieved by ventilating with an hypoxic gas mixture and concentration-responses obtained by incremental additions of ANP (40 nM to 12 mu M), before and after the addition of SCH 42354 (100 nM). SCH 42354 significantly increased the potency (- log EC50) of ANP in the rat IPL. ANP is partly metabolized by NEP. That an inhibitor of NEP increased the potency of ANP in isolated pulmonary vessels, and in isolated perfused whole lungs, suggested that SCH 42354 may be having a local action within the pulmonary vasculature. 相似文献
43.
44.
45.
46.
Comments on an article by T. R. Elliott and E. K. Byrd (see record 1987-23075-001), in which the authors conducted a citation analysis of articles in Rehabilitation Psychology, Volumes 27-29. They claimed to identify influential authors and publications useful for training and research in rehabilitation psychology. Their method of citation analysis, however, appears to have distorted their results. Crisp discusses the problems with their methodology, and makes suggestions for using a different citation method, using more than three volumes of the journal, and including other journals in the analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
RP Whitehead J Jacobson TD Brown SA Taylor GR Weiss JS Macdonald 《Canadian Metallurgical Quarterly》1997,15(6):2414-2419
PURPOSE: Pancreatic cancer is difficult to treat, with most patients surgically unresectable at the time of diagnosis. Radiotherapy and chemotherapy can offer palliation, but more effective therapy is needed. This trial evaluated the effects of an aggressive schedule of paclitaxel given with granulocyte colony-stimulating factor (G-CSF) to patients with advanced pancreatic cancer. PATIENTS AND METHODS: All patients were required to have a histologic diagnosis of pancreatic adenocarcinoma with measurable disease and no prior chemotherapy or radiation therapy. Patients had to have performance status of 0 to 2, pretreatment absolute granulocyte count > or = 1,500/microL, and platelet count greater than or equal to the institutional lower limit of normal. Following pretreatment with dexamethasone, diphenhydramine, and cimetidine, patients received paclitaxel at a dose of 250 mg/m2 by 24-hour infusion on day 1, repeated every 21 days. G-CSF was given at a dose of 5 microg/kg/d on days 3 to 18 or until two consecutive absolute neutrophil counts (ANCs) > or = 10,000/microL were obtained. Doses of paclitaxel were modified depending on nadir counts. RESULTS: Forty-five patients were entered onto this study, with six ineligible. For the 39 eligible patients, there was one complete response (CR) and two partial responses (PRs), five stable/no responses, 23 increasing disease, two early deaths, and six patients whose assessment was inadequate to determine response. The response rate was therefore three of 39 or 8% (95% confidence interval [CI], 2% to 21%). The median survival time for the 39 eligible patients was 5 months. The most common toxicities were anemia, leukopenia/granulocytopenia, malaise/fatigue, nausea/vomiting, alopecia, thrombocytopenia, paresthesias, and liver function abnormalities. There was one death due to sepsis. CONCLUSION: Single-agent paclitaxel in this dose and schedule has minimal activity in pancreatic adenocarcinoma patients. 相似文献
48.
SF Ding JD Delhanty JS Dooley L Bowles CB Wood NA Habib 《Canadian Metallurgical Quarterly》1993,17(3):405-409
We have previously shown that the tumor suppressor gene for hepatocellular carcinoma (HCC) without cirrhosis may be located on chromosome 5q35-qter. In this study, we analyzed nine cases of primary HCC without cirrhosis using probes from the MCC and APC genes, which are in the region 5q21-22. None of the informative cases had allele loss detected by these probes, whereas the probe lambda MS8 for the region 5q35-qter showed allele loss in six out of six informative cases. The results confirm that the putative tumor suppressor gene for HCC without cirrhosis on chromosome 5q is distinct from the MCC and APC genes. 相似文献
49.
KA McGovern JS Schoeniger JP Wehrle CE Ng JD Glickson 《Canadian Metallurgical Quarterly》1993,29(2):196-204
Oxygenation is a major determinant of the physiological state of cultured cells. 19F NMR can be used to determine the oxygen concentration available to cells immobilized in a gel matrix by measuring the relaxation rate (1/T1) of perfluorocarbons (PFC) incorporated into the gel matrix. In calcium alginate gel beads without cells the relaxation rate (1/T1) of the trifluoromethyl group of perfluorotripropylamine (FTPA) varies linearly with oxygen concentration, with a slope of 1.26 +/- 0.15 x 10(-3) s-1 microM-1 and an intercept of 0.50 +/- 0.04 s-1. During perfusion with medium equilibrated with 95%/5% O2/CO2, changes in PFC T1s indicate that the average oxygen concentration was reduced from 894 +/- 102 microM in the absence of cells to 476 +/- 65 microM and 475 +/- 50 microM in the presence of 0.7 x 10(8) EMT6/Ro and RIF-1 murine tumor cells per milliliter of gel, respectively. The presence of 0.2 microliters of FTPA/ml of gel had no effect on the energy status of the cells as indicated by 31P NMR spectra. To calculate oxygen gradients within the beads from the average PFC T1 of the sample, a mathematical model was used assuming that oxygen is the limiting nutrient for cell metabolism and that the cellular oxygen consumption rate is independent of oxygen concentration. Data for EMT6/Ro cells were fit using experimentally determined perfusion parameters together with literature values for cell volume and oxygen consumption rate.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
50.
Each of twelve volunteers, at 2 week intervals, received 1 g of antipyrine, a test drug, and were exposed for 4 h either to toluene (375 mg/m3) or xylene (435 mg/m3) singly or in combination with ethanol (0.45 g/kg body wt. before the onset of exposure and 0.15 g/kg thrice every 1 h during exposure to maintain a steady level of ethanol in blood approximately 11 mmol/dm3). No significant differences were found in salivary antipyrine half-life (T1/2 approximately 12 h); and clearance (ClAP approximately 0.83 cm3/s) between control and groups exposed to solvents and/or ethanol. Nevertheless, a tendency to increase the metabolic rate of antipyrine in xylene-exposed group (T1/2 approximately 6.8 h; ClAP approximately 1.40 cm3/s) and counteraction of ethanol (T1/2 approximately 15 h; ClAP approximately 0.63 cm3/s) should be noted. The stimulation of lipid peroxidation in the serum as a biological effect of combined exposure to ethanol and toluene/xylene was observed. 相似文献