全文获取类型
收费全文 | 8204篇 |
免费 | 170篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 85篇 |
综合类 | 3篇 |
化学工业 | 1264篇 |
金属工艺 | 168篇 |
机械仪表 | 158篇 |
建筑科学 | 267篇 |
矿业工程 | 16篇 |
能源动力 | 145篇 |
轻工业 | 728篇 |
水利工程 | 49篇 |
石油天然气 | 48篇 |
无线电 | 763篇 |
一般工业技术 | 1132篇 |
冶金工业 | 2633篇 |
原子能技术 | 95篇 |
自动化技术 | 826篇 |
出版年
2021年 | 57篇 |
2020年 | 61篇 |
2019年 | 66篇 |
2018年 | 77篇 |
2017年 | 84篇 |
2016年 | 108篇 |
2015年 | 63篇 |
2014年 | 87篇 |
2013年 | 412篇 |
2012年 | 155篇 |
2011年 | 242篇 |
2010年 | 186篇 |
2009年 | 203篇 |
2008年 | 222篇 |
2007年 | 224篇 |
2006年 | 212篇 |
2005年 | 194篇 |
2004年 | 215篇 |
2003年 | 197篇 |
2002年 | 187篇 |
2001年 | 185篇 |
2000年 | 163篇 |
1999年 | 191篇 |
1998年 | 595篇 |
1997年 | 388篇 |
1996年 | 280篇 |
1995年 | 205篇 |
1994年 | 206篇 |
1993年 | 222篇 |
1992年 | 142篇 |
1991年 | 122篇 |
1990年 | 141篇 |
1989年 | 120篇 |
1988年 | 107篇 |
1987年 | 116篇 |
1986年 | 125篇 |
1985年 | 129篇 |
1984年 | 99篇 |
1983年 | 119篇 |
1982年 | 120篇 |
1981年 | 96篇 |
1980年 | 77篇 |
1979年 | 105篇 |
1978年 | 99篇 |
1977年 | 118篇 |
1976年 | 193篇 |
1975年 | 65篇 |
1974年 | 72篇 |
1973年 | 73篇 |
1972年 | 53篇 |
排序方式: 共有8380条查询结果,搜索用时 32 毫秒
51.
52.
Study of fluorescence emission from flexible PVC‐based formulations, colored by exposure to road asphalt or degraded thermally or by UV aging, shows that fluorescent species are formed during the interaction of PVC with road asphalt. For the conditions found in exterior automotive applications, no other known degradation causes development of fluorescence. Flexible PVC‐based formulations discolored by asphalt staining or degraded thermally at moderate temperatures bleach completely under conditions of natural or artificial weathering. A simple technique, using visually observed photoluminescence and photobleaching, can thus identify photoactive groups formed during the interaction of PVC with road asphalt. Application of this test method will allow selective improvement of failed asphalt resistance without treating the “overall” stability of a compound. 相似文献
53.
Burns John W.; Kubilus Amanda; Bruehl Stephen; Harden R. Norman; Lofland Kenneth 《Canadian Metallurgical Quarterly》2003,71(1):81
Changes in maladaptive cognitions may constitute therapeutic processes of multidisciplinary pain programs. A cross-lagged panel design was used to determine whether (a) early-treatment cognitive change predicted late-treatment outcome index change, but not vice versa; and (b) these effects remained significant with depression change controlled. Ninety chronic pain patients, in a 4-week multidisciplinary program, completed measures of catastrophizing, pain helplessness, depression, pain, interference, and activity level at pre-, mid-, and posttreatment. With depression changes controlled, early-treatment catastrophizing and pain helplessness changes predicted late-treatment outcome index changes, but not vice versa; early-treatment depression changes predicted late-treatment activity changes, but not vice versa. Findings advance understanding of pain treatment process and suggest that negative cognition changes may indeed affect improvements in treatment outcome. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
Operation of a 16-tap fiber-optic delay line configured as a bandpass filter with a fundamental frequency of 2.0 GHz over the frequency range from 0 to 12.5 GHz is discussed. Equal tap weights and spacings were used to facilitate comparison of experimental and predicted results. More than 1011 analog multiplications per second are performed in this relatively simple signal processing system. Other processors for performing functions such as matched filtering and correlation can be implemented by appropriate choice of the mirror reflectances and fiber lengths 相似文献
55.
Investigated the relationship between Type A (coronary prone) behavior, aerobic fitness, and cardiovascular recovery from stress in 56 male undergraduates. Ss were tested for actual aerobic power and Type A behavior on the Jenkins Activity Survey—Form T before performing the Stroop Color–Word Interference Test. Type A behavior was related to speed of recovery following the test, with Type As being slower to return to baseline heart rate levels than Type B (noncoronary prone) Ss. Physiological and cognitive variables affecting speed of recovery from stress are examined, and the lack of effect of fitness on recovery is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
57.
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
58.
King Abby C.; Taylor C. Barr; Haskell William L.; DeBusk Robert F. 《Canadian Metallurgical Quarterly》1989,8(3):305
Evaluated 120 healthy, sedentary, middle-aged adults randomly assigned to either a 6-mo home-based aerobic exercise training program or to an assessment-only control condition. Adherence across the 6-mo period by the exercise group was demonstrated by self-report and heart rate microprocessor methods to exceed 75%. A 14-item Likert rating scale was used to measure a variety of psychological variables. Significant between-groups differences favoring the exercise group were found on scale items closely associated with actual physical changes that occurred with exercise (satisfaction with shape/appearance, perceived fitness). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
60.
Conlon P.J. Tong Y.P. French P.M.W. Taylor J.R. Shestakov A.V. 《Electronics letters》1994,30(9):709-710
Sub-100 fs pulse generation from a Kerr lens modelocked Cr4+ :YAG laser has been demonstrated for the first time, yielding femtosecond pulses tunable from 1.49 to 1.56 μm with pulses as short as 90 fs obtained at 1.53 μm 相似文献