全文获取类型
收费全文 | 287585篇 |
免费 | 3065篇 |
国内免费 | 817篇 |
专业分类
电工技术 | 5030篇 |
综合类 | 162篇 |
化学工业 | 45403篇 |
金属工艺 | 11895篇 |
机械仪表 | 8606篇 |
建筑科学 | 6846篇 |
矿业工程 | 1835篇 |
能源动力 | 6734篇 |
轻工业 | 25911篇 |
水利工程 | 3190篇 |
石油天然气 | 7087篇 |
武器工业 | 16篇 |
无线电 | 31448篇 |
一般工业技术 | 56928篇 |
冶金工业 | 51361篇 |
原子能技术 | 7532篇 |
自动化技术 | 21483篇 |
出版年
2021年 | 2098篇 |
2018年 | 3672篇 |
2017年 | 3622篇 |
2016年 | 3904篇 |
2015年 | 2465篇 |
2014年 | 4231篇 |
2013年 | 12019篇 |
2012年 | 6829篇 |
2011年 | 9212篇 |
2010年 | 7565篇 |
2009年 | 8642篇 |
2008年 | 8929篇 |
2007年 | 8813篇 |
2006年 | 7826篇 |
2005年 | 7309篇 |
2004年 | 6800篇 |
2003年 | 6556篇 |
2002年 | 6627篇 |
2001年 | 6497篇 |
2000年 | 6176篇 |
1999年 | 6229篇 |
1998年 | 14749篇 |
1997年 | 11029篇 |
1996年 | 8566篇 |
1995年 | 6523篇 |
1994年 | 5914篇 |
1993年 | 5787篇 |
1992年 | 4479篇 |
1991年 | 4440篇 |
1990年 | 4284篇 |
1989年 | 4301篇 |
1988年 | 4255篇 |
1987年 | 3598篇 |
1986年 | 3595篇 |
1985年 | 4161篇 |
1984年 | 3965篇 |
1983年 | 3620篇 |
1982年 | 3422篇 |
1981年 | 3558篇 |
1980年 | 3422篇 |
1979年 | 3365篇 |
1978年 | 3445篇 |
1977年 | 3923篇 |
1976年 | 5037篇 |
1975年 | 3158篇 |
1974年 | 3007篇 |
1973年 | 3024篇 |
1972年 | 2651篇 |
1971年 | 2473篇 |
1970年 | 2104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
A method is given for calculating the monitoring reliability parameters (MRP) for an engineering system with allowance for the drift in the measurement error of the means of measurement (MM). The approach is based on introducing a biased MM error distribution into the traditional formulas for the conditional probabilities of spurious and unobserved failure. The bias at the center of the distribution is determined by the systematic error at the given instant. An example is given to illustrate the performance in MRP calculation.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–13, January, 1994. 相似文献
54.
Biryukov S.V. Polevoi V.G. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(6):1160-1170
For pt.I see ibid., vol.43, no.6, pp.1150-9 (1996). An exact solution of the electrostatic problem for calculating the surface charge and electric field distributions in an arbitrary periodic interdigital transducer (IDT) is given using the results of our companion paper. An arbitrary external electric field may be specified along the electrode structure with the unit cell containing one electrode, or several electrodes, of different widths. The potentials of the electrodes that may be specified are also arbitrary. It is shown that in the case without an external field, the solution includes all the known results as special cases. The case of shorted electrodes in the external electric field is investigated in detail. The surface charge and electric field distributions are calculated for a spatially harmonic external field with an arbitrary wavenumber. The results of the calculations are represented graphically for various ratios between the period of the electrode structure and the wavelength of the external field for the case of a unit cell containing one or two electrodes of different widths 相似文献
55.
56.
This article presents the results of a pilot-study conducted on a small sample of women with breast cancer and the members of their social support system. The purpose was to determine the potential link between the mental health of the breast cancer patient and their support system. Mental health was assessed with the SCL-90-R (Derogatis, 1977), a self-report scale composed of 90 items divided into nine categories, offering three global indicators of distress: the Global Severity Index (GSI); the Positive Symptom Distress Index (PSDI), and the Positive Symptom Total (PST). The SCL-90-R was distributed to a sample of 14 subjects: seven women treated for breast cancer and seven significant others (social support). The results led to the definition of symptoms such as hostility, phobic anxiety and psychosis specific to either the woman or the support system. 相似文献
57.
O. A. Ustrekhova T. G. Ezhikova-Babakhanova G. B. Basov 《Chemistry and Technology of Fuels and Oils》1993,29(11):544-548
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 11, pp. 17–18, 23, November, 1993. 相似文献
58.
B Antonsson DB Kassel G Di Paolo R Lutjens BM Riederer G Grenningloh 《Canadian Metallurgical Quarterly》1998,273(14):8439-8446
SCG10 is a neuron-specific, membrane-associated protein that is highly concentrated in growth cones of developing neurons. Previous studies have suggested that it is a regulator of microtubule dynamics and that it may influence microtubule polymerization in growth cones. Here, we demonstrate that in vivo, SCG10 exists in both phosphorylated and unphosphorylated forms. By two-dimensional gel electrophoresis, two phosphoisoforms were detected in neonatal rat brain. Using in vitro phosphorylated recombinant protein, four phosphorylation sites were identified in the SCG10 sequence. Ser-50 and Ser-97 were the target sites for protein kinase A, Ser-62 and Ser-73 for mitogen-activated protein kinase and Ser-73 for cyclin-dependent kinase. We also show that overexpression of SCG10 induces a disruption of the microtubule network in COS-7 cells. By expressing different phosphorylation site mutants, we have dissected the roles of the individual phosphorylation sites in regulating its microtubule-destabilizing activity. We show that nonphosphorylatable mutants have increased activity, whereas mutants in which phosphorylation is mimicked by serine-to-aspartate substitutions have decreased activity. These data suggest that the microtubule-destabilizing activity of SCG10 is regulated by phosphorylation, and that SCG10 may link signal transduction of growth or guidance cues involving serine/threonine protein kinases to alterations of microtubule dynamics in the growth cone. 相似文献
59.
M.E.W. Eggenkamp V. A. Shvarts R. Blaauwgeers A. Storm R. Jochemsen G. Frossati 《Journal of Low Temperature Physics》1998,110(1-2):299-304
This paper focuses on the hydrodynamics of third sound on a superfluid
3
He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range. 相似文献
60.