全文获取类型
收费全文 | 336723篇 |
免费 | 4993篇 |
国内免费 | 842篇 |
专业分类
电工技术 | 6658篇 |
综合类 | 785篇 |
化学工业 | 51527篇 |
金属工艺 | 11103篇 |
机械仪表 | 9426篇 |
建筑科学 | 8712篇 |
矿业工程 | 1003篇 |
能源动力 | 9056篇 |
轻工业 | 34628篇 |
水利工程 | 2740篇 |
石油天然气 | 3802篇 |
武器工业 | 18篇 |
无线电 | 41232篇 |
一般工业技术 | 63342篇 |
冶金工业 | 62829篇 |
原子能技术 | 5610篇 |
自动化技术 | 30087篇 |
出版年
2021年 | 2892篇 |
2020年 | 2146篇 |
2019年 | 2551篇 |
2018年 | 4474篇 |
2017年 | 4226篇 |
2016年 | 4398篇 |
2015年 | 3308篇 |
2014年 | 5351篇 |
2013年 | 15978篇 |
2012年 | 8665篇 |
2011年 | 11434篇 |
2010年 | 9022篇 |
2009年 | 10183篇 |
2008年 | 10773篇 |
2007年 | 10652篇 |
2006年 | 9285篇 |
2005年 | 8546篇 |
2004年 | 8239篇 |
2003年 | 7955篇 |
2002年 | 7748篇 |
2001年 | 7866篇 |
2000年 | 7505篇 |
1999年 | 7949篇 |
1998年 | 19538篇 |
1997年 | 13977篇 |
1996年 | 10908篇 |
1995年 | 8377篇 |
1994年 | 7593篇 |
1993年 | 7289篇 |
1992年 | 5450篇 |
1991年 | 5225篇 |
1990年 | 5066篇 |
1989年 | 4917篇 |
1988年 | 4802篇 |
1987年 | 4032篇 |
1986年 | 4130篇 |
1985年 | 4895篇 |
1984年 | 4451篇 |
1983年 | 4169篇 |
1982年 | 3719篇 |
1981年 | 3913篇 |
1980年 | 3606篇 |
1979年 | 3520篇 |
1978年 | 3314篇 |
1977年 | 3998篇 |
1976年 | 5273篇 |
1975年 | 2869篇 |
1974年 | 2732篇 |
1973年 | 2774篇 |
1972年 | 2249篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The author discusses the objectives of a computer-telephony integration (CTI) bus for the PC, TDM, network synchronization, digital switching, multichassis connections, MVIP bus technologies, SCbus technology, and CTI client server architectures 相似文献
993.
994.
995.
996.
OBJECTIVES: The aim of this investigation was to study the glomerular and tubular effects of low doses (15 mg) of methotrexate in patients with rheumatoid arthritis with and without combined treatment with aspirin (2 g single dose). METHODS: Renal function was measured by the plasma clearance of EDTA labelled with chromium-51 (51Cr-EDTA) and mercaptoacetyltriglycine labelled with technetium-99m (99mTc-MAG-3). RESULTS: Clearance of 51Cr-EDTA was reduced from 98 (6) to 87 (5) ml/min (mean (SEM)) for patients receiving methotrexate only and further reduced to 76 (5) ml/min for patients receiving methotrexate and aspirin. This effect was reversible as 51Cr-EDTA increased to 85 (6) ml/min during continued treatment with methotrexate alone. Clearance of 99mTc-MAG-3 also decreased from 366 (18) to 315 (17) ml/min in patients receiving methotrexate alone and further to 295 (17) ml/min during treatment with aspirin and methotrexate. Continued treatment with methotrexate alone resulted in a further decrease in the 99mTc-MAG-3 clearance to 253 (17) ml/min. CONCLUSIONS: The study shows that treatment with low doses of methotrexate particularly when combined with aspirin affects glomerular and tubular function. These effects may be of clinical importance and renal function should therefore be monitored with more sensitive methods than serum creatinine as this may not reflect these changes. 相似文献
997.
998.
M Luppi R Marasca P Barozzi T Artusi G Torelli 《Canadian Metallurgical Quarterly》1993,17(11):1003-1011
In search of a possible involvement of viral agents in angioimmunoblastic lymphadenopathy with dysproteinaemia (AILD) and AILD-like lymphoma (AILD-L), we studied the presence of human herpesvirus-6 (HHV-6) in the lymph node biopsies of 12 cases by polymerase chain reaction (PCR). Given the rarity of this lymphoproliferative disorder, we investigated archival specimens, consisting of formalin-fixed and paraffin-embedded tissues, obtained from patients with a clinical and histologic diagnosis of AILD and AILD-L. HHV-6 sequences were detected in the lymph node biopsies of 7 out of the 12 AILD and AILD-L cases examined. HHV-6 sequences were identified also in the involved liver and spleen tissues of one patient and in the PBMCs of two patients, all carrying viral sequences in the affected lymph nodes. We also used PCR to characterize the HHV-6 genomes, showing that two different viral strains are represented in the pathologic tissues. This study provides evidence of the presence of HHV-6 specific sequences in an unexpectedly high proportion of our series of AILD and AILD-L cases, suggesting a possible involvement of this lymphotropic virus in the pathogenesis of at least some cases of the disease. 相似文献
999.
MRI techniques were developed and employed for non-destructive and noninvasive study of seedcoat cracking in low moisture soybean kernels during heated air drying. Proton density image and transient moisture distribution profile of a single soybean kernel can be obtained using MRI. These MRI techniques proved to be particularly useful for the continuous observation of initiation and propagation of seedcoat cracking during the entire period of drying process without interruption.
The proton density images of soybean kernels showed that seedcoat cracking was initiated perpendicular to the long axis of the kernel near the hilum. The transient moisture distribution profiles in soybean kernels during drying indicate that moisture gradient developed during drying was higher in the seedcoat than in the cotyledon. Drying temperature and initial average moisture content were positively correlated with the soyhean seedcoat crackig. The location of the 相似文献
The proton density images of soybean kernels showed that seedcoat cracking was initiated perpendicular to the long axis of the kernel near the hilum. The transient moisture distribution profiles in soybean kernels during drying indicate that moisture gradient developed during drying was higher in the seedcoat than in the cotyledon. Drying temperature and initial average moisture content were positively correlated with the soyhean seedcoat crackig. The location of the 相似文献
1000.
J. R. Prez-Correa F. R. Sepúlveda M. A. Duarte 《International Journal of Adaptive Control and Signal Processing》1995,9(2):183-197
This paper presents experimental results obtained in temperature adaptive control of a heating vessel. A non-linear model of the process showed that the feed flow rate causes severe variations in time constant and process gain. An extended horizon self-tuning controller and two different model reference adaptive controllers were tested. The influence of design parameters on control performance for each algorithm was assessed. The control system was disturbed with load and setpoint changes. 相似文献