全文获取类型
收费全文 | 834190篇 |
免费 | 16396篇 |
国内免费 | 5976篇 |
专业分类
电工技术 | 19125篇 |
技术理论 | 2篇 |
综合类 | 6409篇 |
化学工业 | 129966篇 |
金属工艺 | 34242篇 |
机械仪表 | 28805篇 |
建筑科学 | 24172篇 |
矿业工程 | 6576篇 |
能源动力 | 22208篇 |
轻工业 | 70922篇 |
水利工程 | 10199篇 |
石油天然气 | 20412篇 |
武器工业 | 719篇 |
无线电 | 94781篇 |
一般工业技术 | 159291篇 |
冶金工业 | 135221篇 |
原子能技术 | 17864篇 |
自动化技术 | 75648篇 |
出版年
2022年 | 7040篇 |
2021年 | 10229篇 |
2020年 | 7484篇 |
2019年 | 8478篇 |
2018年 | 13260篇 |
2017年 | 13908篇 |
2016年 | 14255篇 |
2015年 | 10919篇 |
2014年 | 17130篇 |
2013年 | 40342篇 |
2012年 | 26163篇 |
2011年 | 34394篇 |
2010年 | 27836篇 |
2009年 | 30116篇 |
2008年 | 30679篇 |
2007年 | 30114篇 |
2006年 | 26949篇 |
2005年 | 24021篇 |
2004年 | 21777篇 |
2003年 | 20890篇 |
2002年 | 20104篇 |
2001年 | 19692篇 |
2000年 | 18600篇 |
1999年 | 18821篇 |
1998年 | 41031篇 |
1997年 | 29690篇 |
1996年 | 23171篇 |
1995年 | 17883篇 |
1994年 | 15897篇 |
1993年 | 15420篇 |
1992年 | 11793篇 |
1991年 | 11177篇 |
1990年 | 10918篇 |
1989年 | 10491篇 |
1988年 | 10091篇 |
1987年 | 8839篇 |
1986年 | 8529篇 |
1985年 | 9856篇 |
1984年 | 8923篇 |
1983年 | 8432篇 |
1982年 | 7625篇 |
1981年 | 7754篇 |
1980年 | 7317篇 |
1979年 | 7334篇 |
1978年 | 7126篇 |
1977年 | 7923篇 |
1976年 | 9925篇 |
1975年 | 6339篇 |
1974年 | 6065篇 |
1973年 | 6194篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Germanovix W. O'Neill G. Toumazou C. Drakakis F.M. Kitney R.I. Lande T.S. 《Electronics letters》1998,34(11):1051-1052
A micropower tone-control circuit comprising two first-order log-domain filters and a subtractor built with MOS transistors in weak inversion is described. The tone-controller is capable of providing bass cut/boost and treble cut operations. This circuit is being used in new designs of a conventional (acoustic) hearing-aid and cochlear implant 相似文献
992.
A Woodtli 《Canadian Metallurgical Quarterly》1995,6(4):135-142
Consistent efforts to identify and clinically validate new nursing diagnosis within recognized categories are essential to taxonomy development. Mixed incontinence is a clinical condition resulting in leakage of urine associated with increased intra-abdominal pressure (stress) and inability to delay voiding (urge). The presence of mixed incontinence was clinically validated in two populations (n = 9, n = 40) of community-dwelling women and initial defining characteristics were identified. Research findings from both studies support the addition of a proposed sixth nursing diagnosis, mixed incontinence, to the diagnostic category, alteration in urinary elimination. 相似文献
993.
V. S. -Kh. Kim V. A. Samoilov E. M. Sherysheva Chen Yun 《Chemical and Petroleum Engineering》1993,29(8):355-358
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 8, pp. 9–11, August, 1993. 相似文献
994.
This report demonstrates how to calculate distances between points described in terms of latitude and longitude, using the Postal Code Conversion File (PCCF) and other files available from the Geography Division of Statistics Canada. Examples based on hospital data show how the results can be summarized in the form of tables, figures, or maps. Aerial distance to the nearest hospital is a crude but objective indicator of geographic accessibility to hospital services. Distances were calculated between enumeration area centroids for the population and blockface or enumeration area centroids for the hospitals. The median aerial distance to the nearest hospital facility in Canada was less than 3 km, while the mean distance was about 6 km. For teaching hospitals, the median aerial distance was a little less than 30 km, while the mean distance was a little more than 90 km. As most health files for administrative and research purposes contain postal codes, these techniques have potentially wide application. 相似文献
995.
M Abele-Horn C Wolff P Dressel A Zimmermann W Vahlensieck F Pfaff G Ruckdeschel 《Canadian Metallurgical Quarterly》1996,15(7):595-598
The efficiency of the polymerase chain reaction (PCR) was compared with that of culture for detection of Ureaplasma urealyticum and Mycoplasma hominis in 726 clinical specimens comprising 189 gynecological samples, 362 urological samples, and 175 samples from newborn infants. The sensitivity of PCR versus culture was 95% for both organisms, while the sensitivity of culture versus PCR was 91% for Ureaplasma urealyticum and 84% for Mycoplasma hominis. Furthermore, PCR tests were faster than culture tests, allowing the time to diagnosis to be reduced from two to five days to 24 h. 相似文献
996.
997.
Two cases of congenital trabecular hypoplasia of the right ventricle are reported. In the first, the neonatal diagnosis was missed and the child did well until the 13th month of life when a modified Blalock-Taussig shunt was done because of increasing cyanosis. Outcome was good until the 4th year of life when symptomatic atrioventricular block was detected in an emergency situation. A bidirectional Glenn anastomosis and pacemaker implantation were successfully carried out after clinical establization and the child is doing well up to now. The second case presents the disease with its worst features: severe cyanosis and acidosis in the first day of life. A modified Blalock-Taussig shunt was performed and death occurred soon after the operation. 相似文献
998.
Importance of Solar Drying is increasing worldwide, especially in areas where the use of the abundant, renewable and clean solar energy is essentially advantageous. In the developing countries and in rural areas the traditional open-air drying methods should be substituted by the more effective and more economic solar drying technologies.
R&D needs should be considered in the basic research and experimental fields; in performance measurement; in the modelling-simulation-design and testing. The international co-operation of experts should be improved and more efforts would be needed in the policy and in the public information. 相似文献
R&D needs should be considered in the basic research and experimental fields; in performance measurement; in the modelling-simulation-design and testing. The international co-operation of experts should be improved and more efforts would be needed in the policy and in the public information. 相似文献
999.
C. C. Price
M. Salama
《Computers & Mathematics with Applications》1993,26(12):17-24Criteria are established to determine the optimal policy for allocating a set of uniform tasks onto a multiprocessor hypercube ensemble. It is shown that the optimal policy depends on the ratio of computation to intertask communication required by the distributed program, and that based on this ratio, tasks should be placed either all on one processor or uniformly distributed over the largest possible hypercube. 相似文献
1000.
Conclusions Experimental and calculated data have been given which support the mechanism for formation of secondary gel particles in viscose.According to this mechanism, the formation of gel particles takes place in the case where the time for diffusion exchange between the main stream and an immobile wall layer is greater than the time for coagulation.VNIIPV, Mytishchi. Translated from Khimicheskie Volokna, No. 2, pp. 22–24, March–April, 1992. 相似文献