全文获取类型
收费全文 | 6262篇 |
免费 | 66篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 54篇 |
综合类 | 2篇 |
化学工业 | 499篇 |
金属工艺 | 37篇 |
机械仪表 | 59篇 |
建筑科学 | 103篇 |
矿业工程 | 2篇 |
能源动力 | 48篇 |
轻工业 | 309篇 |
水利工程 | 19篇 |
石油天然气 | 12篇 |
无线电 | 408篇 |
一般工业技术 | 570篇 |
冶金工业 | 3939篇 |
原子能技术 | 20篇 |
自动化技术 | 248篇 |
出版年
2021年 | 36篇 |
2019年 | 22篇 |
2018年 | 30篇 |
2017年 | 36篇 |
2016年 | 28篇 |
2015年 | 29篇 |
2014年 | 42篇 |
2013年 | 144篇 |
2012年 | 76篇 |
2011年 | 114篇 |
2010年 | 82篇 |
2009年 | 74篇 |
2008年 | 89篇 |
2007年 | 100篇 |
2006年 | 96篇 |
2005年 | 89篇 |
2004年 | 82篇 |
2003年 | 92篇 |
2002年 | 82篇 |
2001年 | 77篇 |
2000年 | 88篇 |
1999年 | 174篇 |
1998年 | 1174篇 |
1997年 | 705篇 |
1996年 | 461篇 |
1995年 | 284篇 |
1994年 | 231篇 |
1993年 | 269篇 |
1992年 | 62篇 |
1991年 | 81篇 |
1990年 | 83篇 |
1989年 | 105篇 |
1988年 | 118篇 |
1987年 | 89篇 |
1986年 | 72篇 |
1985年 | 68篇 |
1984年 | 29篇 |
1983年 | 41篇 |
1982年 | 50篇 |
1981年 | 57篇 |
1980年 | 60篇 |
1979年 | 32篇 |
1978年 | 37篇 |
1977年 | 127篇 |
1976年 | 216篇 |
1975年 | 27篇 |
1974年 | 20篇 |
1973年 | 17篇 |
1972年 | 18篇 |
1971年 | 13篇 |
排序方式: 共有6329条查询结果,搜索用时 15 毫秒
1.
2.
3.
Crosstalk between microstrip transmission lines 总被引:1,自引:0,他引:1
Hill D.A. Cavcey K.H. Johnk R.T. 《Electromagnetic Compatibility, IEEE Transactions on》1994,36(4):314-321
Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk 相似文献
4.
Math1 is essential for genesis of cerebellar granule neurons 总被引:1,自引:0,他引:1
N Ben-Arie HJ Bellen DL Armstrong AE McCall PR Gordadze Q Guo MM Matzuk HY Zoghbi 《Canadian Metallurgical Quarterly》1997,390(6656):169-172
5.
JM Piepmeier DL Keefe MA Weinstein D Yoshida J Zielinski TT Lin Z Chen F Naftolin 《Canadian Metallurgical Quarterly》1993,32(3):422-30; discussion 430-1
Estramustine is an estradiol-based agent that has been shown to accumulate in human glioma cells, resulting in a concentration-dependent alteration in cell size and shape within minutes and an inhibition of proliferation over 3 to 6 days. We evaluated human glioblastoma cultures with [3H]thymidine incorporation assays to determine estramustine's early effects on deoxyribonucleic acid synthesis in these tumors. Because estramustine shares a common structural motif with other antimicrotubule drugs, we synthesized four A-ring conjugates of estrone that contained a carbamate moiety but lacked nitrogen mustard. These analogs were examined by [3H]thymidine incorporation and compared with vinblastine. Greater than 70% inhibition of [3H]thymidine incorporation occurred within 1 hour of treatment with estramustine at 10(-5) mol/L, which increased to 80% inhibition at 4 hours. Ethyl carbamate JE208 was nearly as effective as estramustine in inhibiting deoxyribonucleic acid synthesis, and both were more effective than vinblastine. The inhibitory effects of estramustine and estrone analogs were reversible; vinblastine was not reversible. Although estramustine and JE208 induced similar antiproliferative and morphological changes in glioblastoma cells that persisted for at least 4 days, there was a modest recovery of morphology and thymidine incorporation with JE208 after prolonged treatment. The common findings with estramustine and JE208 suggest that these agents may have a similar mechanism of action and form the basis for the investigation of new agents that may rapidly and reversibly inhibit glioblastoma. 相似文献
6.
D Galasko T Saitoh Y Xia LJ Thal R Katzman LR Hill L Hansen 《Canadian Metallurgical Quarterly》1994,44(10):1950-1951
We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap. 相似文献
7.
8.
9.
S Hakki SJ Harwood MA Morrissey JG Camblin DL Laven WB Webster 《Canadian Metallurgical Quarterly》1997,(335):275-285
When clinical data are insufficient to diagnose infection of bone or joints, nuclear scanning becomes crucial in making an accurate diagnosis. The efficacy of (99m)technetium antigranulocyte monoclonal antibody Fab' fragment (LeukoScan) is prospectively compared with (111)indium white blood cell and (99m)technetium methylene diphosphonate bone scans in 74 patients with suspected musculoskeletal infections. They were grouped according to site of suspected infection: 33 long bones, 23 prosthetic joints, and 18 diabetic feet. Sixty-two of these 74 patients had surgical verification with histopathology or culture. The remaining 12 patients had clinical followup as proof of absence of infection. The overall sensitivity of LeukoScan, (111)indium white blood cell, and (99m)technetium methylene diphosphonate bone scans was 93%, 85% and 92%, respectively. Specificity was 89%, 75% and 52%, and accuracy was 90%, 79% and 74%, respectively. The conclusion from this study is that LeukoScan is more accurate in detecting osteomyelitis, with better sensitivity and specificity in prosthetic joints. Compared with (111)indium white blood cell scans, LeukoScan++ gives superior images, and results are obtained in 1 to 6 hours without biohazard risk from handling blood products. 相似文献
10.
A device that harnesses the mechanical energy of skeletal muscle contracting in a linear configuration has been implanted in goats. This energy convertor transforms muscle work to hydraulic energy that could drive a variety of cardiac assist devices. The device is mounted with a rib clamp and plate affixed to the sternum by cortical bone screws. A transcutaneous hydraulic line carries a silicon based working fluid to an external system that controls the muscle load. In 60 to 70 kg goats, the latissimus dorsi insertion was reattached to the energy convertor. A Telectronics myostimulator with intramuscular electrodes stimulated the latissimus dorsi. In acute implants, hydraulic pressures in excess of 150 psi were obtained. Chronic implantation of the device allowed system evaluation in the conscious unanesthetized animal. Two weeks after implant, hydraulic pressures in excess of 200 psi were obtained and energy transferred to the external loading system exceeded 1 J per contraction. Six weeks after implant, the device continued to cycle freely. These initial results are very promising and suggest an implantable energy convertor is feasible. Development of an energy convertor is an important step toward tether-free skeletal muscle powered cardiac assist devices. 相似文献