全文获取类型
收费全文 | 279989篇 |
免费 | 4422篇 |
国内免费 | 2245篇 |
专业分类
电工技术 | 5378篇 |
技术理论 | 2篇 |
综合类 | 3319篇 |
化学工业 | 36186篇 |
金属工艺 | 16684篇 |
机械仪表 | 13062篇 |
建筑科学 | 7450篇 |
矿业工程 | 2038篇 |
能源动力 | 5605篇 |
轻工业 | 12501篇 |
水利工程 | 3131篇 |
石油天然气 | 3738篇 |
武器工业 | 117篇 |
无线电 | 33380篇 |
一般工业技术 | 59162篇 |
冶金工业 | 37970篇 |
原子能技术 | 3010篇 |
自动化技术 | 43923篇 |
出版年
2023年 | 736篇 |
2022年 | 1272篇 |
2021年 | 1896篇 |
2020年 | 1369篇 |
2019年 | 1539篇 |
2018年 | 22188篇 |
2017年 | 21844篇 |
2016年 | 14874篇 |
2015年 | 3081篇 |
2014年 | 3248篇 |
2013年 | 7083篇 |
2012年 | 9592篇 |
2011年 | 21808篇 |
2010年 | 19261篇 |
2009年 | 16676篇 |
2008年 | 17470篇 |
2007年 | 20171篇 |
2006年 | 5542篇 |
2005年 | 9299篇 |
2004年 | 7181篇 |
2003年 | 6553篇 |
2002年 | 4668篇 |
2001年 | 3888篇 |
2000年 | 3656篇 |
1999年 | 3922篇 |
1998年 | 10501篇 |
1997年 | 6984篇 |
1996年 | 5464篇 |
1995年 | 3789篇 |
1994年 | 3359篇 |
1993年 | 3233篇 |
1992年 | 2019篇 |
1991年 | 1892篇 |
1990年 | 1841篇 |
1989年 | 1621篇 |
1988年 | 1420篇 |
1987年 | 1107篇 |
1986年 | 1127篇 |
1985年 | 1191篇 |
1984年 | 1038篇 |
1983年 | 921篇 |
1982年 | 911篇 |
1981年 | 879篇 |
1980年 | 736篇 |
1979年 | 671篇 |
1978年 | 577篇 |
1977年 | 716篇 |
1976年 | 1186篇 |
1975年 | 455篇 |
1974年 | 399篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Recent studies have suggested that cytokines play a critical role in the pathophysiology of alopecia areata; however, no information is available regarding the difference in cytokine profiles in these patients. Serum levels of cytokines, including interferon gamma (IFN-gamma), tumor necrosis factor alpha, interleukin 1 alpha (IL-1 alpha), IL-2, IL-4, and IL-6, were measured using radioimmunoassay or enzyme-linked immunosorbent assay techniques in patients with the localized form and the extensive form (alopecia universalis). The serum levels of IL-1 alpha and IL-4 were significantly elevated in patients with the localized form. In contrast, the serum levels of IFN-gamma and IL-2 were significantly elevated in patients with the extensive form. These results indicate that immune responses in the localized form and the extensive form of alopecia areata are regulated by Th2 cytokines and Th1 cytokines, respectively. 相似文献
993.
994.
C. Y. Wang 《Acta Mechanica》1996,119(1-4):229-234
Summary The nonlinear buckling of an elastic bar with softening characteristic is studied. It is found that, under large disturbances, the bar may buckle under loads well below the linear buckling load. 相似文献
995.
Y. Ohshima H.S. Ahn M. Aoki S. Awa M. Fukushima H. Hayashii X.Q. Hu T.W. Hur S. Igarashi H. Ikeda H.C. Jeong K. Kaneyuki D.Y. Kim S.K. Kim A. Kuzmin M.H. Lee S. Noguchi A. Ochi H. Sagawa N. Sato N. Sugiyama K. Tamai T. Tanimori N. Toomi T.J. Wang K. Watanabe Y. Watanabe X.C. Zhong Y.C. Zhu 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,380(3):517-523
We studied the performance of a prototype electromagnetic calorimeter for the BELLE detector at the KEK proton synchrotron for an energy range of 0.25–3.5 GeV. The prototype consisted of an array of 6 × 5 CsI(Tl) crystals with 30 cm length (16.2 radiation lengths) and about 6 cm × 6 cm cross section. The scintillation light of each CsI(Tl) crystal was read out by two large-area PIN photodiodes and charge-sensitive preamplifiers attached at the rear face of the crystal. We measured the energy and position resolution for electrons and the e/π separation for two sets of matrix configurations: one corresponded to the center and the other to the edge of the barrel calorimeter. The overall performance measured by the test proves that the prototype calorimeter is satisfactory for the use in the BELLE detector. 相似文献
996.
997.
The authors present a low-voltage BiCMOS dynamic minimum circuit using a parallel comparison algorithm for VLSI implementation of fuzzy controllers. Using low-voltage BiCMOS dynamic circuits and a parallel comparison algorithm, a four-4-bit-input minimum circuit designed, based on a 1μm BiCMOS technology, shows a 9.5ns comparison time, which is a ×2.5 improvement in speed as compared to that based on CMOS technology 相似文献
998.
999.
The influence of socioeconomic and nutritional status on menarche in Nigerian school girls 总被引:1,自引:0,他引:1
EA Abioye-Kuteyi EO Ojofeitimi OI Aina F Kio Y Aluko O Mosuro 《Canadian Metallurgical Quarterly》1997,11(3):185-195
Two once-daily electroconvulsive shocks (ECS) produced retrograde amnesia in rats trained on a Hebb-Williams maze; Verapamil (12.5 mg/kg, i.p.) or felodipine (10 mg/kg, p.o.) administered half an hour before each ECS attenuated this ECS-induced amnesia. Hence, these drugs may hold promise for the containment of amnesia induced by electroconvulsive therapy (ECT). Speculatively, one or more of several mechanisms may be involved: cerebral vasodilatation, enhancement of cholinergic tone, and inhibition of calcium-mediated impairment of neuronal function. These drugs may also act by attenuating the systolic surge in blood pressure during ECT, thereby decreasing edema due to cerebral hyperperfusion, as well as decreasing the possible transfer of potentially neurotoxic macromolecules through a putative breach in the blood-brain barrier. 相似文献
1000.
M Tanaka T Hakuto M Akatsuka E Morimoto T Hama M Morimoto Y Hiraga M Hyodo 《Canadian Metallurgical Quarterly》1993,42(6):883-887
We injected botulinum toxin to treat hemifacial spasm, and investigated the effects and the patient's impression of this treatment. Average duration of improvement lasted about 3.5 months in both the initial treatment group and the recurrent group. However the patients in the recurrent group received fewer units of botulinum toxin than those in the initial treatment group. Except for local paralysis that disappeared within a month, there were very few complications. Most patient were satisfied with this treatment. We conclude that the treatment of hemifacial spasm with botulinum toxin is both simple and useful. 相似文献