全文获取类型
收费全文 | 794511篇 |
免费 | 7636篇 |
国内免费 | 2235篇 |
专业分类
化学 | 411695篇 |
晶体学 | 11300篇 |
力学 | 38371篇 |
综合类 | 26篇 |
数学 | 105216篇 |
物理学 | 237774篇 |
出版年
2021年 | 7052篇 |
2020年 | 7666篇 |
2019年 | 8575篇 |
2018年 | 11193篇 |
2017年 | 11161篇 |
2016年 | 16317篇 |
2015年 | 9583篇 |
2014年 | 15297篇 |
2013年 | 35808篇 |
2012年 | 27619篇 |
2011年 | 33345篇 |
2010年 | 24297篇 |
2009年 | 24062篇 |
2008年 | 31260篇 |
2007年 | 30995篇 |
2006年 | 28638篇 |
2005年 | 25610篇 |
2004年 | 23740篇 |
2003年 | 21151篇 |
2002年 | 20935篇 |
2001年 | 22660篇 |
2000年 | 17507篇 |
1999年 | 13675篇 |
1998年 | 11574篇 |
1997年 | 11280篇 |
1996年 | 10802篇 |
1995年 | 9775篇 |
1994年 | 9692篇 |
1993年 | 9361篇 |
1992年 | 10126篇 |
1991年 | 10484篇 |
1990年 | 10149篇 |
1989年 | 9815篇 |
1988年 | 9678篇 |
1987年 | 9517篇 |
1986年 | 9042篇 |
1985年 | 11691篇 |
1984年 | 12087篇 |
1983年 | 9923篇 |
1982年 | 10302篇 |
1981年 | 9897篇 |
1980年 | 9298篇 |
1979年 | 9996篇 |
1978年 | 10300篇 |
1977年 | 10177篇 |
1976年 | 10066篇 |
1975年 | 9547篇 |
1974年 | 9417篇 |
1973年 | 9590篇 |
1972年 | 6914篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
181.
A. I. Bril' V. P. Kabashnikov N. V. Kuz'mina Yu. V. Khodyko 《Journal of Applied Spectroscopy》1991,55(3):934-939
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 478–484, September, 1991. 相似文献
182.
A. P. Prudnikov Yu. A. Brychkov O. I. Marichev 《Journal of Mathematical Sciences》1991,54(6):1239-1341
Translated from Itogi Nauki i Tekhniki, Seriya Matematicheskii Analiz, Vol. 27, pp. 3–146, 1989. 相似文献
183.
V. K. Malyutenko A. I. Liptuga V. A. Botte V. I. Chernyakhovskii 《Journal of Applied Spectroscopy》1991,55(4):1024-1028
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 624–629, October, 1991. 相似文献
184.
The stressed state of a thick three-layer plate with two circular holes is studied. Resolving functions are expressed in terms of Kolosov-Muskhelishvili integral potentials and modified Bessel functions. The problem is reduced to solving an infinite set of linear algebraic equations.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 25–28, 1987. 相似文献
185.
Robert M. O'Keefe 《The Journal of the Operational Research Society》1989,40(5):415-422
Cognitive style refers to differences that can be perceived in individuals due to differing cognitive structures. There has been a large amount of research on how cognitive style affects managerial decision-making, particularly in the context of management information systems, but little or no attempt to relate these findings to operational research. This paper reviews the findings of cognitive-style research from the perspective of operational research, and draws a number of useful inferences concerning the matching of OR aids to managers, the presentation of information and recommendations, the use and acceptance of OR, and the structure of OR groups. Further, it is argued that cognitive-style findings help to give a justification to the move towards ‘soft’ approaches to analysis. 相似文献
186.
A. Hertz 《Graphs and Combinatorics》1989,5(1):149-157
We consider the graphs that can be obtained by deleting in a Meyniel graphG all the edges induced by an arbitrary set of nodes. These graphs will be called Slim and we prove that they are perfect. We study relations between Slim graphs and other well known classes of perfect graphs; particularly we show that the perfection of Slim graphs gives a proof to the conjecture of M. Preissmann that Meyniel graphs are locally perfect. 相似文献
187.
188.
C. Ghezzi E. Gombia R. Mosca M. Pillan 《Applied Physics A: Materials Science & Processing》1989,48(5):457-463
Capacitance DLTS measurements have been performed in VPE GaAs MESFETs prepared on Bridgman Cr-doped and LEC undoped semi-insulating substrates. A band of electron traps not intrinsically related to the VPE growth process and accumulating near the metal (gate) — semiconductor interface was detected in all the samples. Deeper regions into the channel were free from any detectable trap. Near pinch-off conditions, a positive capacitance signal was found to dominate the DLTS spectra only in the case of samples prepared on Cr-doped substrates. The hypothesis of this positive transient being related to changes in the occupation of surface states in the ungated surface access regions has been checked by comparing experimental and calculated dependencies of the signal amplitude on reverse gate voltage. Unexplained discrepancies, together with the absence of positive signal in MESFETs prepared on LEC undoped substrates, suggest the possibility of hole emission from hole traps within the bulk of the device. 相似文献
189.
P. M. Gandini A. Zucco 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》1989,59(1):15-21
Some well-known theorems on typical properties of real-valued continuous functions defined on [0, 1] are improved using the
notion of porosity. 相似文献
190.
Periodic sound-pressure time functions with frequency components below 50 Hz were used to measure within their period (a) the temporal course of masking, called a masking-period pattern (MPP), and (b) the temporal course of suppression of delayed evoked otoacoustic emissions, called a suppression-period pattern (SPP). Three different time functions were used: an alternating Gaussian impulse, its first integral, and its second integral. In each case, the course of the SPP is a mirror image of that of the MPP: Small masking corresponds to small suppression, while strong masking coincides with almost total suppression. Since otoacoustic emissions are assumed to have their origin in the inner ear, it can be argued that simultaneous masking, an effect including central processing, is very strongly based on peripheral processes located in the cochlea. Both MPP and SPP are closely related to the second derivative of the sound-pressure time function. 相似文献