全文获取类型
收费全文 | 12930篇 |
免费 | 831篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 70篇 |
综合类 | 7篇 |
化学工业 | 2400篇 |
金属工艺 | 101篇 |
机械仪表 | 284篇 |
建筑科学 | 431篇 |
矿业工程 | 20篇 |
能源动力 | 215篇 |
轻工业 | 1981篇 |
水利工程 | 68篇 |
石油天然气 | 18篇 |
无线电 | 682篇 |
一般工业技术 | 1742篇 |
冶金工业 | 4166篇 |
原子能技术 | 23篇 |
自动化技术 | 1563篇 |
出版年
2024年 | 35篇 |
2023年 | 140篇 |
2022年 | 113篇 |
2021年 | 326篇 |
2020年 | 270篇 |
2019年 | 271篇 |
2018年 | 346篇 |
2017年 | 356篇 |
2016年 | 465篇 |
2015年 | 419篇 |
2014年 | 545篇 |
2013年 | 988篇 |
2012年 | 857篇 |
2011年 | 644篇 |
2010年 | 468篇 |
2009年 | 465篇 |
2008年 | 489篇 |
2007年 | 424篇 |
2006年 | 395篇 |
2005年 | 244篇 |
2004年 | 226篇 |
2003年 | 199篇 |
2002年 | 191篇 |
2001年 | 122篇 |
2000年 | 120篇 |
1999年 | 219篇 |
1998年 | 1276篇 |
1997年 | 735篇 |
1996年 | 476篇 |
1995年 | 275篇 |
1994年 | 238篇 |
1993年 | 292篇 |
1992年 | 57篇 |
1991年 | 75篇 |
1990年 | 64篇 |
1989年 | 79篇 |
1988年 | 83篇 |
1987年 | 62篇 |
1986年 | 50篇 |
1985年 | 57篇 |
1984年 | 22篇 |
1983年 | 22篇 |
1982年 | 34篇 |
1981年 | 37篇 |
1980年 | 36篇 |
1979年 | 25篇 |
1978年 | 18篇 |
1977年 | 105篇 |
1976年 | 202篇 |
1975年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Astrid Labidi Marie-Christine Salon Alessandro Gandini Hervé Cheradame 《Polymer Bulletin》1985,14(3-4):271-278
Summary 2-Furyl vinyl ketone was polymerised using anionic, cationic and free-radical initiators. Yields and molecular weights varied with the type of activation. Whereas radical polymerisation gave a product possessing a regular vinylic structure, other kinds of units were detected in the polymers prepared with anionic and cationic catalysts. 相似文献
3.
We compare two link analysis ranking methods of web pages in a site. The first, called Site Rank, is an adaptation of PageRank to the granularity of a web site and the second, called Popularity Rank, is based on the frequencies of user clicks on the outlinks in a page that are captured by navigation sessions of users through
the web site. We ran experiments on artificially created web sites of different sizes and on two real data sets, employing
the relative entropy to compare the distributions of the two ranking methods. For the real data sets we also employ a nonparametric
measure, called Spearman's footrule, which we use to compare the top-ten web pages ranked by the two methods. Our main result
is that the distributions of the Popularity Rank and Site Rank are surprisingly close to each other, implying that the topology
of a web site is very instrumental in guiding users through the site. Thus, in practice, the Site Rank provides a reasonable
first order approximation of the aggregate behaviour of users within a web site given by the Popularity Rank. 相似文献
4.
Sebastián López Gustavo M. Callicó Félix Tobajas Valentín de Armas José F. López Roberto Sarmiento 《ETRI Journal》2008,30(6):862-864
This letter presents a novel approach for organizing computational resources into groups within H.264/AVC motion estimation architectures, leading to reductions of up to 75% in the equivalent gate count with respect to state‐of‐the‐art designs. 相似文献
5.
6.
7.
BACKGROUND: In the Minnesota Colon Cancer Control Study, annual fecal occult blood testing reduced mortality from colorectal cancer by at least 33.4%. Some attribute a large part of this reduction to chance detection of cancers by colonoscopies; rehydration of guaiac test slides greatly increased positivity and consequently the number of colonoscopies performed. This study was conducted to determine how much of the reduction resulted from chance detection. METHODS: We used a mathematical model developed by Lang and Ransohoff to estimate the proportion of the 33.4% mortality attainable by chance alone. Applying the model requires the specification of five parameters: duration of follow-up, rate of compliance with fecal occult blood testing, rate of compliance with colonoscopy, positivity rate, and efficacy of colonoscopy in reducing colorectal cancer mortality. We took values for four of the five parameters directly from the Minnesota study. For the fifth parameter, efficacy of colonoscopy, we selected a value of 60%, based on the conclusions of another study. Whereas the Lang-Ransohoff model selects persons for colonoscopy by chance alone, those with bleeding cancers would also be selected by sensitive fecal occult blood testing. We therefore adjusted the result of the Lang-Ransohoff model for this dual detectability. RESULTS: We found that 16%-25% of the reduction in colorectal cancer deaths effected by fecal occult blood testing in the Minnesota study was due to chance detection; the remainder was due to sensitive detection. CONCLUSION: Chance played a minor role in the detection of colorectal cancers by fecal occult blood testing in the Minnesota study. 相似文献
8.
9.
HJ Lee HK Ha MH Kim YK Jeong PN Kim MG Lee JS Kim DJ Suh SG Lee YI Min YH Auh 《Canadian Metallurgical Quarterly》1997,169(2):517-520
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers. 相似文献
10.
M Al-Sarraf TF Pajak RW Byhardt JJ Beitler MM Salter JS Cooper 《Canadian Metallurgical Quarterly》1997,37(4):777-782
PURPOSE: Despite aggressive surgery and postoperative radiation therapy, only 30% of patients who have advanced, potentially resectable carcinomas of the head and neck survive for 5 years. In the hope of improving this situation we studied the effect of postoperative radiotherapy delivered concurrently with cisplatin. METHODS AND MATERIALS: Patients who had Stage IV tumors and/or involved surgical margins received 60 Gy in 30 fractions over 6 weeks plus 100 mg/m2 of cisplatin on radiotherapy days 1, 23 and 43. Fifty-two patients participated in this trial and 51 were evaluated. Forty-three (84%) patients had pathologic T3 or T4 disease, 43 (84%) had Stage IV disease, and 27 (53%) had histologically involved surgical margins. RESULTS: Severe and life-threatening toxicities occurred in 20% and 12% of patients, respectively; the most common drug-related toxicities were leukopenia, anemia, nausea, and vomiting. Seventeen patients (43%) remain alive with no evidence of disease. Four patients (8%) died with no evidence of neoplastic disease, and one patient has died of a second independent malignancy. By actuarial analysis at 3 years, 48% of patients are alive, 81% have locoregional control of disease, and 57% are free of distant metastases. CONCLUSIONS: Based on comparison with similar patients treated in a prior Radiation Therapy Oncology Group/Intergroup trial (RTOG), we conclude that postoperative radiotherapy with concurrent cisplatin may improve locoregional control rates and should be prospectively tested. 相似文献