全文获取类型
收费全文 | 431710篇 |
免费 | 6061篇 |
国内免费 | 2333篇 |
专业分类
电工技术 | 8956篇 |
技术理论 | 5篇 |
综合类 | 1278篇 |
化学工业 | 64345篇 |
金属工艺 | 17246篇 |
机械仪表 | 12347篇 |
建筑科学 | 10028篇 |
矿业工程 | 2278篇 |
能源动力 | 9687篇 |
轻工业 | 37199篇 |
水利工程 | 4324篇 |
石油天然气 | 8225篇 |
武器工业 | 250篇 |
无线电 | 51473篇 |
一般工业技术 | 80976篇 |
冶金工业 | 88848篇 |
原子能技术 | 8557篇 |
自动化技术 | 34082篇 |
出版年
2021年 | 3497篇 |
2019年 | 3188篇 |
2018年 | 5138篇 |
2017年 | 5097篇 |
2016年 | 5466篇 |
2015年 | 4067篇 |
2014年 | 6698篇 |
2013年 | 18221篇 |
2012年 | 11330篇 |
2011年 | 15266篇 |
2010年 | 12219篇 |
2009年 | 13568篇 |
2008年 | 14592篇 |
2007年 | 14782篇 |
2006年 | 13244篇 |
2005年 | 11901篇 |
2004年 | 11116篇 |
2003年 | 10593篇 |
2002年 | 10409篇 |
2001年 | 10858篇 |
2000年 | 10102篇 |
1999年 | 10627篇 |
1998年 | 27180篇 |
1997年 | 18876篇 |
1996年 | 14465篇 |
1995年 | 10730篇 |
1994年 | 9575篇 |
1993年 | 9472篇 |
1992年 | 6872篇 |
1991年 | 6532篇 |
1990年 | 6543篇 |
1989年 | 6350篇 |
1988年 | 5929篇 |
1987年 | 4968篇 |
1986年 | 5069篇 |
1985年 | 5664篇 |
1984年 | 5304篇 |
1983年 | 4831篇 |
1982年 | 4348篇 |
1981年 | 4670篇 |
1980年 | 4170篇 |
1979年 | 4228篇 |
1978年 | 4125篇 |
1977年 | 4608篇 |
1976年 | 6075篇 |
1975年 | 3647篇 |
1974年 | 3464篇 |
1973年 | 3419篇 |
1972年 | 2937篇 |
1971年 | 2580篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
The performance of two distributed channel assignment algorithms which use coexistence etiquettes for point to point links are considered by the authors. It has been found that selecting channels prior to transmission at the transmitter as opposed to the receiver, supports greater offered traffic with the additional advantage of a less complex protocol 相似文献
952.
A. Benati M.A. Butturi C. Capperdoni M.C. Carotta G. Martinelli M. Merli L. Passari G. Sartori R. Van Steenwinkel G.M. Youssef 《Solar Energy Materials & Solar Cells》1996,43(2):183
The newly developed ingot growing techniques, as the three-grain and the columnar multigrain ingot processes, are now offering the possibility of slicing thinner wafers (≤ 100 μm). In this paper we present the results obtained on p type large area (≥ 100 cm2) and 100 μm thick wafers by using both conventional and reverse cell manufacturing technologies.The conventional cells are provided with aluminium or boron BSF plus screen-printed silver mirror or a silver-aluminium net; the reverse cells have a FSF and the deep back junction completely covered by a screen-printed or CVD silver layer.The constructing parameters have been chosen on the base of one and two dimensions modeling and both raw material and devices have been completely characterized.This work shows that very thin wafers do not introduce serious problems for the conventional manufacturing of solar cells. The efficiencies of the normal and of the reverse cells are found to be comparable and are of the same order than those of thicker cells, however at a significant lower cost. The main obtained result has to be related to the demonstration of a cell manufacturing feasibility starting from very thin wafers. 相似文献
953.
L. S. Lovinskii 《Measurement Techniques》1996,39(10):1025-1027
A method, apparatus and results of measurements of the degradation of semiconductor optoelectronic components (light-emitting
diodes and photodiodes) are described. The difficulties that occur in such investigations are pointed out.
Translated from Izmeritel'naya Tekhnika, No. 10, pp. 33–35, October, 1996. 相似文献
954.
Griseofulvin solid dispersions were prepared using polyethylene glycol 6000 (PEG), talc, and their combination as carriers by the solvent method. The dissolution of griseofulvin from these dispersions was studied. It was found that in these carriers the drug dissolution rate was a function of drug loading. The dissolution rate from dispersions prepared using PEG was similar to that from PEG/talc dispersions, especially at a low percentage of drug loading. Dispersions of PEG and PEG/talc provided dissolution rates faster than those from dispersions of talc. The incorporation of talc in PEG yielded dispersions with properties of less tackiness and ease for handling. Dissolution kinetics, based on the Hixson-Crowell equation, was used to determine the characteristics of griseofulvin particles in dispersions. Linear relationships were obtained for PEG and PEG/talc dispersions that indicated the presence of a uniformly sized monoparticulate system, whereas deviation from linearity was observed for talc dispersions. This appeared to be a multiparticulate system in which particles were present as free form and adsorbed form on the surface of talc. 相似文献
955.
Network management in large heterogeneous communication environments requires the incorporation of more advanced tools than are currently available, especially in the area of fault management. By providing an informational infrastructure for documenting network behavior and maintenance activities, TTSs (trouble ticket systems) have provided some relief for the fault management problem. Researchers have recognized TTSs as a means for realizing more advanced functions in network management platforms to effect automatic trouble ticket generation, fault diagnostics, and the correlation of multiple views network problems and behavior. The authors describe current research trends towards understanding and implementing these advanced functions in a TTS framework 相似文献
956.
A simple and accurate measurement of intraabdominal pressure is essential to predict a successful closure of defects in omphalocele and gastroschisis. Intravesical pressure (IVP) is a close estimation of intraabdominal pressure and can be measured safely by placing a catheter in the urinary bladder during surgery. Three neonates with gastroschisis and four with omphalocele were studied. Pressure-related complications such as ascites leakage, ventral hernia, impaired venous return of the lower extremities, and oliguria developed only in the patients with IVP > 20 mmHg after fascial closure. Prolonged hospitalization, ventilation support and intensive care were required for these patients. 相似文献
957.
S Saito M Izumitani R Shiroki K Ishiguro T Fujioka I Nagakubo 《Canadian Metallurgical Quarterly》1994,85(12):1777-1780
A 31-year-old man came to our hospital complaining of severe voiding pain. He had inserted a fishing line made of nylon into his urethra at the age of eighteen, which was unable to be taken out and had been left there for 13 years. Preoperative ultrasonogram showed severe bilateral hydronephrosis and the serum BUN and creatinine level were as high as 45.2 mg/dl and 4.8 mg/dl, respectively. A huge bladder stone was demonstrated in X-ray film, the patient was admitted and vesicolithotomy was performed. The size of the stone was 10.5 x 7.5 x 7.5 cm and the weight was 360 grams. The fishing line was found inside the stone and the length was over 3 meters. The serum BUN and creatinine level after the operation were still high as 28.4 mg/dl and 4.1 mg/dl, respectively, and they did not improve even after six months following. 相似文献
958.
959.
S Murakami T Igarashi T Yuhiki T Tobe K Mikami S Akimoto J Shimazaki O Matsuzaki 《Canadian Metallurgical Quarterly》1994,85(8):1213-1217
In order to evaluate the significance of repeat transurethral resection (TUR) in differentiating stage A1 prostatic adenocarcinoma from those with stage A2, we performed repeat TUR in 34 patients with an initial diagnosis of stage A1 prostatic adenocarcinoma. It was found that residual adenocarcinoma was present in five cases (14.7%), but the diagnosis was changed from stage A1 to stage A2 in only one case (2.9%). In one patient with final diagnosis of stage A1 carcinoma, bone metastases were detected seven months after the repeat TUR. It was concluded that repeat TUR for stage A1 prostatic adenocarcinoma did not yield clinically significant information. 相似文献
960.
Mita T. Hirata M. Murata K. Zhang H. 《Industrial Electronics, IEEE Transactions on》1998,45(3):488-495
In the motion control field, a disturbance observer-based disturbance canceling control is often used as a robust control methodology. However, this method is nothing more than an alternative design of an integral controller, and the robust stability issue cannot be directly accounted for. In this paper, an extended H∞ control scheme is proposed as a new robust motion control method which achieves the disturbance cancellation ability and guarantees robust stability automatically 相似文献