全文获取类型
收费全文 | 177449篇 |
免费 | 2164篇 |
国内免费 | 704篇 |
专业分类
电工技术 | 3293篇 |
综合类 | 101篇 |
化学工业 | 27998篇 |
金属工艺 | 7776篇 |
机械仪表 | 5119篇 |
建筑科学 | 4437篇 |
矿业工程 | 881篇 |
能源动力 | 4682篇 |
轻工业 | 16446篇 |
水利工程 | 1708篇 |
石油天然气 | 3127篇 |
武器工业 | 2篇 |
无线电 | 19874篇 |
一般工业技术 | 33393篇 |
冶金工业 | 33305篇 |
原子能技术 | 4291篇 |
自动化技术 | 13884篇 |
出版年
2021年 | 1340篇 |
2019年 | 1275篇 |
2018年 | 2109篇 |
2017年 | 2093篇 |
2016年 | 2202篇 |
2015年 | 1583篇 |
2014年 | 2748篇 |
2013年 | 7809篇 |
2012年 | 4579篇 |
2011年 | 6412篇 |
2010年 | 5078篇 |
2009年 | 5908篇 |
2008年 | 5892篇 |
2007年 | 5868篇 |
2006年 | 5023篇 |
2005年 | 4697篇 |
2004年 | 4485篇 |
2003年 | 4152篇 |
2002年 | 4105篇 |
2001年 | 4135篇 |
2000年 | 3927篇 |
1999年 | 4061篇 |
1998年 | 10387篇 |
1997年 | 7396篇 |
1996年 | 5657篇 |
1995年 | 4284篇 |
1994年 | 3618篇 |
1993年 | 3569篇 |
1992年 | 2612篇 |
1991年 | 2538篇 |
1990年 | 2417篇 |
1989年 | 2440篇 |
1988年 | 2382篇 |
1987年 | 2131篇 |
1986年 | 2068篇 |
1985年 | 2371篇 |
1984年 | 2191篇 |
1983年 | 2014篇 |
1982年 | 1882篇 |
1981年 | 1945篇 |
1980年 | 1796篇 |
1979年 | 1818篇 |
1978年 | 1776篇 |
1977年 | 2109篇 |
1976年 | 2688篇 |
1975年 | 1558篇 |
1974年 | 1549篇 |
1973年 | 1608篇 |
1972年 | 1351篇 |
1971年 | 1262篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
I Quiquandon I Plantier PY Hatron O Chassaing F Bauters B Desablens B Devulder 《Canadian Metallurgical Quarterly》1995,37(2):149-152
Haemophagocytic syndrome is a heterogenous disease characterized by disordered macrophage activation associated with viral, bacterial or parasitic infection. The few reports of haemophagocytosis occurring in the presence of mycobacterial infection show a high mortality rate and we present two further cases notable for their favourable issue. Rapidity of diagnosis and immediate treatment could explain the avoidance of a fatal outcome. 相似文献
992.
The morbidity and mortality associated with major abdominal surgical interventions in 34 histologically proven cirrhotic patients are analyzed by the authors. The surgical interventions were carried out as urgent, absolute and elective indications. Thirty-seven general and surgical complications were observed following major abdominal surgery in 34 cirrhotics. Seven out of 34 patients died, giving a mortality rate of 21%. Suture-line insufficiency, peritonitis, sepsis and other inflammatory processes turned out to be the most common complications. Statistical analysis showed that the Child criteria, prothrombin level and white blood cell count were useful prognostic factors. 相似文献
993.
994.
Backscattered radiation (BSR) arising from field-defining collimators and entering the beam monitor chamber (BMC) may contribute to observed variations in medical linear accelerator photon beam output with collimator setting. Measuring the magnitude of such contributions for particular accelerators under specified operating conditions is therefore important when attempting to understand and model accelerator head scatter. The present work was conducted to confirm some backscatter measurements for collimating jaws reported previously and to extend these to include other accelerators and a multileaf collimator (MLC). BSR reaching the BMC from the jaws of Clinac 600C, 2100C and 2300CD accelerators and from an MLC on the 2300CD was investigated using both target-current-pulse-counting and telescope methods. Our measurements show that for the Clinac 600C BSR-dependent output variations are negligible. However, for the 2100C and 2300CD BSR-dependent relative output increased in an almost linear fashion, by up to 2.4% for 15 and 18 MV beams, and by up to 1.7% for 6 MV beams, as the field size varied from 5 x 5 cm2 to 40 x 40 cm2. The magnitude of BSR dependent upon collimator location in the head, as expected, thereby contributing to the collimator exchange effect. An earlier study at our centre using the telescope method had reported higher BSR levels. This discrepancy was resolved when corrections for telescope block and room scatter, previously assumed negligible, were made. 相似文献
995.
This paper highlights the role of the faculty member in recruiting students currently enrolled in B.S. programs in engineering and the sciences into full-time pursuit of a graduate-level engineering degree. The faculty member is demonstrated to be in a unique position to influence such students, providing strong counterforces to a confluence of attitudes and pressures experienced during the B.S. experience which effectively create a barrier to full-time engineering graduate study. We analyze this barrier via the method of force field analysis, and demonstrate that effective recruitment into full-time graduate study must be based on a four-fold strategy of education, expectations, improved B.S. experience and better control of the B.S. environment. Approaches to implement these strategies are discussed. 相似文献
996.
997.
F Tárkányi F Szelecsényi P Kopecky T Molnár L Andó P Mikecz GY Tóth A Rydl 《Canadian Metallurgical Quarterly》1994,45(2):239-249
Proton induced nuclear reactions on enriched 111Cd and 112Cd have been studied up to 30 MeV in the context of routine production of the medically used isotope 111In with low and medium energy cyclotrons. The excitation functions of 111Cd(p,n)111m,gIn and 112Cd(p,2n)111m,gIn as production reactions and 111Cd(p,2n)110mIn, 111Cd(p,2n)110In, 111Cd(p,3n)109ml,m2,In, 112Cd(p,3n)110mIn, 112Cd(p,3n)110gIn as competing processes have been measured using the activation method involving the stacked-foil technique. The deduced thick target yields are compared with those obtained experimentally. 相似文献
998.
999.
1000.
F Imai T Suzuki T Ishibashi M Tanaka Y Akiyama Y Dohi 《Canadian Metallurgical Quarterly》1994,21(4):612-615
OBJECTIVE: We investigated the in vitro immunomodulatory effects of sulfasalazine on B cells in rheumatoid arthritis (RA). METHODS: Reversed hemolytic plaque assay and 3H-thymidine incorporation were measured. RESULTS: B cells from patients with RA showed hyperactivity to stimulation by Staphylococcus aureus Cowan I. Sulfasalazine significantly inhibited this B cell hyperactivity in a dose dependent manner. The kinetic study and a decrease in 3H-thymidine incorporation on Day 3 indicate that sulfasalazine inhibited the early phase (0-48 h) of B cell proliferation in these patients. Sulfapyridine also inhibited B cell hyperactivity in these patients, but 5-aminosalicylic acid and N-acetylsulfapyridin had no significant effect. CONCLUSION: Sulfasalazine exhibited a direct immunosuppressive effect on B cell hyperactivity in patients with RA, which may be responsible for its therapeutic effectiveness in this disorder. 相似文献