全文获取类型
收费全文 | 290606篇 |
免费 | 3211篇 |
国内免费 | 829篇 |
专业分类
电工技术 | 5073篇 |
综合类 | 173篇 |
化学工业 | 46370篇 |
金属工艺 | 11948篇 |
机械仪表 | 8666篇 |
建筑科学 | 6894篇 |
矿业工程 | 1845篇 |
能源动力 | 6873篇 |
轻工业 | 26057篇 |
水利工程 | 3207篇 |
石油天然气 | 7100篇 |
武器工业 | 17篇 |
无线电 | 31738篇 |
一般工业技术 | 57683篇 |
冶金工业 | 51491篇 |
原子能技术 | 7584篇 |
自动化技术 | 21927篇 |
出版年
2021年 | 2253篇 |
2018年 | 3762篇 |
2017年 | 3711篇 |
2016年 | 4018篇 |
2015年 | 2548篇 |
2014年 | 4386篇 |
2013年 | 12253篇 |
2012年 | 6991篇 |
2011年 | 9421篇 |
2010年 | 7716篇 |
2009年 | 8792篇 |
2008年 | 9090篇 |
2007年 | 8939篇 |
2006年 | 7919篇 |
2005年 | 7405篇 |
2004年 | 6883篇 |
2003年 | 6634篇 |
2002年 | 6718篇 |
2001年 | 6553篇 |
2000年 | 6217篇 |
1999年 | 6267篇 |
1998年 | 14772篇 |
1997年 | 11062篇 |
1996年 | 8598篇 |
1995年 | 6544篇 |
1994年 | 5941篇 |
1993年 | 5805篇 |
1992年 | 4499篇 |
1991年 | 4449篇 |
1990年 | 4304篇 |
1989年 | 4311篇 |
1988年 | 4258篇 |
1987年 | 3608篇 |
1986年 | 3600篇 |
1985年 | 4166篇 |
1984年 | 3979篇 |
1983年 | 3628篇 |
1982年 | 3429篇 |
1981年 | 3565篇 |
1980年 | 3430篇 |
1979年 | 3369篇 |
1978年 | 3449篇 |
1977年 | 3925篇 |
1976年 | 5041篇 |
1975年 | 3161篇 |
1974年 | 3010篇 |
1973年 | 3028篇 |
1972年 | 2655篇 |
1971年 | 2477篇 |
1970年 | 2107篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
K Lenz S N Mahnik N Weissenbacher R M Mader P Krenn S Hann G Koellensperger M Uhl S Knasmüller F Ferk W Bursch M Fuerhacker 《Water science and technology》2007,56(12):141-149
Cytostatic agents are applied in cancer therapy and subsequently excreted into hospital wastewater. As these substances are known to be carcinogenic, mutagenic and toxic for reproduction, they should be removed from wastewater at their source of origin.In this study the fate and effects of the cancerostatic platinum compounds (CPC) cisplatin, carboplatin, oxaliplatin, 5-fluorouracil (5-FU) and the anthracyclines doxorubicin, daunorubicin and epirubicin were investigated in hospital wastewater. Wastewater from the in-patient treatment ward of a hospital in Vienna was collected and monitored for the occurrence of the selected drugs. A calculation model was established to spot the correlation between administered dosage and measured concentrations. To investigate the fate of the selected substances during wastewater treatment, the oncologic wastewater was treated in a pilot membrane bioreactor system (MBR) and in downstream advanced wastewater treatment processes (adsorption to activated carbon and UV-treatment). Genotoxic effects of the oncologic wastewater were assessed before and after wastewater treatment followed by a risk assessment.Monitoring concentrations of the selected cytostatics in the oncologic wastewater were in line with calculated concentrations. Due to different mechanisms (adsorption, biodegradation) in the MBR-system 5 - FU and the anthracyclines were removed < LOD, whereas CPC were removed by 60%. In parallel, genotoxic effects could be reduced significantly by the MBR-system. The risk for humans, the aquatic and terrestrial environment by hospital wastewater containing cytostatic drugs was classified as small in a preliminary risk assessment. 相似文献
992.
993.
Frozen (–18°C) de-seeded kiwifruit pulp (Actinidia deliciosa) was irradiated at a dose of 100 krad and stored at -18°C. Irradiation resulted in a 2.11 log10 reduction in aerobic plate count (APC) with bacteria being most susceptible. Molds were less susceptible than yeasts. Assessments carried out over 6 months storage showed no significant differences in physical, chemical and sensory properties between irradiated and nonirradiated pulps. The microbial populations of the pulps decreased in parallel throughout the storage period. Frozen storage without irradiation resulted in a 3 log10 reduction in APC over the 6 months period, a 38% reduction in ascorbic acid, and a slight loss of color. Three days frozen storage (– 18°C) following irradiation resulted in an APC only 0.89 log10 higher than 6 months frozen storage (- 18°C) without irradiation with potential savings in energy and holding times which could have economic benefits. 相似文献
994.
F Narducci I Switala R Rajabally J Decocq G Delahousse 《Canadian Metallurgical Quarterly》1998,27(2):150-160
Testing for syphilis during pregnancy reveals a positive serologic status in 0.02% of cases. However, a 66% rate of stillbirths is noted in women who are infected and who have not benefited from any treatment. Routine screening is at present performed during the early stages of pregnancy but a second serologic test during the third trimester is useful in the diagnosis of a late infection especially in drug users or HIV (human immunodeficiency virus) positive patients. Congenital syphilis is diagnosed in utero when a positive maternal serologic status is associated with ultrasound images showing fetal abnormalities; these include hepatosplenomegaly, hyperechogenic bowel, signs of bowel obstruction or fetal hydrops. Maternal syphilis is treated by delayed action penicillin and is indicated even for patients allergic to the antibiotic which in this particular case is delivered after desensitization. First line therapy by intravenous penicillin is indicated when confronted with the following high risk factors of congenital syphilis: an elevated titre of VDRL (venereal disease research laboratory) at the time of diagnosis or delivery, unknown date of the precise onset of the infection, the appearance of a rash or of a chancre during pregnancy, ultrasound fetal abnormalities or late therapy during the third trimester. Treatment of the new-born child will depend on the results of clinical, serologic and X-ray evaluation. Long term follow-up for at least a year is mandatory. 相似文献
995.
996.
F. S. Kaplan I. G. Shulik L. S. Alekseenko G. P. Orekhova 《Refractories and Industrial Ceramics》1995,36(3):82-85
Casting properties of concentrated aqueous dispersions of zirconia stabilized by Y2O3, Si2O3, or a mixture of them are investigated. Optimum values of the pH, temperature, and slip concentration for the production
of thin-walled vacuum-tight articles are established.
Translated from Ogneupory, No. 3, pp. 12–15, March, 1995. 相似文献
997.
P Dobkowski K Mlosek P Zydlewski G Aderek L Królicki 《Canadian Metallurgical Quarterly》1998,4(19):10-11
The aim of our study was to show the results of the Magnetic Resonance Angiography of pelvis and lower extremities. 21 patients with clinical signs of venous thrombosis were examined. The obtained results show the MRA is very useful in evaluation of venous flow. 相似文献
998.
Maurice E. Monnom G. Ostrowsky D.B. Baxter G.W. 《Lightwave Technology, Journal of》1995,13(7):1349-1353
We propose a sensor based on the temperature dependant behavior of the two lines of green emission of the erbium ion. The ratio of the intensities of these two lines presents a very low dependance on pump wavelength and pump power fluctuations. The sensitivity of the ratio is 0.013/°C between room temperature and 600°C. In addition, the measurement is self-calibrated 相似文献
999.
Demartini G. Granelli G.P. Marannino P. Montagna M. Ricci M. 《Power Systems, IEEE Transactions on》1996,11(4):1785-1791
The paper deals with the problem of improving co-ordination between the online economic dispatch (ED) function and the very short-term advance dispatch (AD). Both procedures are formulated as optimal dispatching problems, but while a static model is used for the ED function, a dynamic model is employed in AD. The need to account for ramp-rate limits of thermal power generation even in the ED phase is satisfied by adding suitable penalty terms to the objective function of the classical ED problem. These penalties are proportional to the Lagrange multipliers associated with ramp-rate limits that are active at the AD solution. An efficient updating procedure is used to correct the penalization by taking the load forecast errors into account. The proposed co-ordination procedure can provide the snapshot ED with the long range perspective of AD without resorting to heuristic approaches. The procedure is validated by extensive testing carried out both on a small CIGRE test case and on a medium-large scale network representative of the Italian EHV system. Moreover, test results show that the CPU time requirements of the modified ED procedure are still suited to online applications 相似文献
1000.
Wang K. Bryant C. Carlson M. Elmer T. Harris A. Garcia M. Hui C.S. Leong C.K. Reynolds B. Tang R. Weber L. Wenzel J. Wilson G. Becker M. 《Micro, IEEE》1995,15(2):44-49
The MPC105 peripheral component interconnection bridge/memory controller provides a platform-specification-compliant bridge between Power PC microprocessors and the PCI bus. With it, designers can create systems using peripherals already designed for a variety of standard PC interfaces. This bridge chip also integrates a secondary cache controller and high-performance memory controller that supports DRAM or synchronous DRAM and ROM or flash ROM 相似文献