全文获取类型
收费全文 | 27431篇 |
免费 | 1022篇 |
国内免费 | 170篇 |
专业分类
化学 | 18264篇 |
晶体学 | 279篇 |
力学 | 808篇 |
数学 | 2705篇 |
物理学 | 6567篇 |
出版年
2023年 | 165篇 |
2022年 | 448篇 |
2021年 | 615篇 |
2020年 | 480篇 |
2019年 | 483篇 |
2018年 | 433篇 |
2017年 | 417篇 |
2016年 | 790篇 |
2015年 | 694篇 |
2014年 | 926篇 |
2013年 | 1650篇 |
2012年 | 1929篇 |
2011年 | 2204篇 |
2010年 | 1389篇 |
2009年 | 1189篇 |
2008年 | 1844篇 |
2007年 | 1610篇 |
2006年 | 1635篇 |
2005年 | 1385篇 |
2004年 | 1239篇 |
2003年 | 1055篇 |
2002年 | 976篇 |
2001年 | 608篇 |
2000年 | 551篇 |
1999年 | 385篇 |
1998年 | 248篇 |
1997年 | 246篇 |
1996年 | 318篇 |
1995年 | 227篇 |
1994年 | 235篇 |
1993年 | 230篇 |
1992年 | 181篇 |
1991年 | 142篇 |
1990年 | 158篇 |
1989年 | 131篇 |
1988年 | 93篇 |
1987年 | 92篇 |
1986年 | 68篇 |
1985年 | 115篇 |
1984年 | 77篇 |
1983年 | 62篇 |
1982年 | 89篇 |
1981年 | 87篇 |
1980年 | 52篇 |
1979年 | 76篇 |
1978年 | 62篇 |
1977年 | 58篇 |
1976年 | 63篇 |
1975年 | 55篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
22.
Jong Uhn Kim 《Transactions of the American Mathematical Society》2002,354(3):1117-1135
In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.
23.
Gauss periods give an exponentiation algorithm that is fast for many finite fields but slow for many other fields. The current paper presents a different method for construction of elements that yield a fast exponentiation algorithm for finite fields where the Gauss period method is slow or does not work. The basic idea is to use elements of low multiplicative order and search for primitive elements that are binomial or trinomial of these elements. Computational experiments indicate that such primitive elements exist, and it is shown that they can be exponentiated fast. 相似文献
24.
Neodymium-substituted Bi4Ti3O12 (BNdT) thin films were prepared by a chemical solution deposition technique on platinum- coated silicon substrates. All of
the samples were annealed at the relatively low temperature of 600 °C by a rapid thermal annealing process in different atmospheres,
such as O2, air, and nitrogen, and vacuum. Irrespective of different annealing atmospheres, all of the BNdT thin films exhibit good
ferroelectric properties, such as a saturated hysteresis loop, good fatigue endurance, and low leakage current density. A
large remanent polarization (Pr) of ∼48 μC/cm2 with an electric field of 240 kV/cm was observed from the BNdT thin film annealed in O2 atmosphere. The BNdT thin films annealed in nitrogen and vacuum, at reduced oxygen partial pressures, exhibit smaller Pr than that annealed in oxygen. The difference of Pr of the BNdT thin films annealed in different atmospheres may originate from differences in the grain sizes and the number
of oxygen vacancies.
PACS 77.55.+f; 77.80.-e; 77.80.Fm; 81.15.-z 相似文献
25.
26.
Taekyun Kim 《Journal of Mathematical Analysis and Applications》2002,273(1):236-242
The purpose of this paper is to give a proof of Kummer type congruence for the q-Bernoulli numbers of higher order, which is an answer to a part of the problem in a previous publication (see Indian J. Pure Appl. Math. 32 (2001) 1565-1570). 相似文献
27.
Homo-apioneplanocin A was efficiently synthesized via stereoselective hydroxymethylation, regio- and chemoselective hydroboration, and chemoselective oxidation as key steps from d-ribose. 相似文献
28.
Vinyl and diene derivatives of thiolactomycin have been prepared via Horner-Wadsworth-Emmons olefination from protected 5-formyl-3,5-dimethylthiotetronic acid. Several 4-position protecting groups and a variety of phosphonates were evaluated, with MOM protection and β-ketophosphonates yielding the highest ratio of the desired product to deformylated product. 相似文献
29.
The fuzzification of convex sets in median algebras is considered, and some of their properties are investigated. A characterization of finite valued fuzzy convex set is given. 相似文献
30.
Yu-Soo Lee Hyun-Ju Chung Jong-Han Joung Eung-Jo Kim Hee-Je Kim 《Optics & Laser Technology》2004,36(1):461-61
We describe the pulse forming of pulsed CO2 laser using multi-pulse superposition technique. Various pulse shapes, high duty cycle pulse forming network (PFN) are constructed by time sequence. This study shows a technology that makes it possible to make various long pulse shapes by activating SCRs of three PFN modules consecutively at a desirable delay time with the aid of a PIC one-chip microprocessor. The power supply for this experiment consists of three PFN modules. Each PFN module uses a capacitor, a pulse forming inductor, a SCR, a high voltage pulse transformer, and a bridge rectifier on each transformer secondary. The PFN modules operate at low voltage by driving the primary of HV pulse transformer. The secondary of the transformer has a full-wave rectifier, which passes the pulse energy to the load in a continuous sequence.We investigated various long pulse shapes as different trigger time intervals of SCRs among three PFN modules. As a result, we could obtain laser beam with various pulse shapes and durations from about 250 to 1000 μs. 相似文献