全文获取类型
收费全文 | 17108篇 |
免费 | 610篇 |
国内免费 | 267篇 |
专业分类
化学 | 10107篇 |
晶体学 | 141篇 |
力学 | 648篇 |
综合类 | 31篇 |
数学 | 2661篇 |
物理学 | 4397篇 |
出版年
2022年 | 140篇 |
2021年 | 268篇 |
2020年 | 310篇 |
2019年 | 315篇 |
2018年 | 288篇 |
2017年 | 249篇 |
2016年 | 415篇 |
2015年 | 390篇 |
2014年 | 421篇 |
2013年 | 1049篇 |
2012年 | 805篇 |
2011年 | 960篇 |
2010年 | 642篇 |
2009年 | 567篇 |
2008年 | 782篇 |
2007年 | 690篇 |
2006年 | 682篇 |
2005年 | 597篇 |
2004年 | 557篇 |
2003年 | 489篇 |
2002年 | 479篇 |
2001年 | 359篇 |
2000年 | 324篇 |
1999年 | 259篇 |
1998年 | 153篇 |
1997年 | 172篇 |
1996年 | 205篇 |
1995年 | 173篇 |
1994年 | 211篇 |
1993年 | 213篇 |
1992年 | 226篇 |
1991年 | 213篇 |
1990年 | 166篇 |
1989年 | 161篇 |
1988年 | 179篇 |
1987年 | 219篇 |
1986年 | 186篇 |
1985年 | 261篇 |
1984年 | 249篇 |
1983年 | 182篇 |
1982年 | 222篇 |
1981年 | 229篇 |
1980年 | 226篇 |
1979年 | 221篇 |
1978年 | 221篇 |
1977年 | 215篇 |
1976年 | 189篇 |
1975年 | 194篇 |
1974年 | 160篇 |
1973年 | 165篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
Mari Grobbelaar‐Van Dalsen 《Mathematical Methods in the Applied Sciences》2004,27(11):1301-1315
This paper is concerned with well‐posedness results for a mathematical model for the transversal vibrations of a two‐dimensional hybrid elastic structure consisting of a rectangular Reissner–Mindlin plate with a Timoshenko beam attached to its free edge. The model incorporates linear dynamic feedback controls along the interface between the plate and the beam. Classical semigroup methods are employed to show the unique solvability of the coupled initial‐boundary‐value problem. We also show that the energy associated with the system exhibits the property of strong stability. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
34.
Jérôme Le NôtreAna Acosta Martinez Pierre H DixneufChristian Bruneau 《Tetrahedron》2003,59(47):9425-9432
Enyne rearrangement of silylated modified terpenoids has been used as the key step for the synthesis of new terpenes and terpenoids. The catalytic system generated in situ from [RuCl2(p-cymene]2, 1,3-bis(mesityl)imidazolinium chloride and cesium carbonate is able to perform the transformation of silylated 1,7-enynes into cyclic siloxanes. Selective cleavage of the silicon-carbon and silicon-oxygen bonds by simple reactions has been performed to afford new terpenes and terpenoids by formal addition of a C5 unit. 相似文献
35.
36.
P. González D. Fernández J. Pou E. García J. Serra B. León M. Pérez-Amor T. Szörényi 《Applied Physics A: Materials Science & Processing》1993,57(2):181-185
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO
x
films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase. 相似文献
37.
Flowing and static gas-phase samples of HNO3 in O2 and N2 were analyzed by long-path ultraviolet/visible (UV/VIS) spectroscopy to reveal the presence of both NO2 and NO3, the concentrations of which were calculated using differential absorption cross sections. NO2 is produced predominantly by the heterogeneous decomposition of HNO3, whereas NO3 is generated in the gas phase by the thermal decomposition of N2O5, a product of the self-disproportionation of liquid HNO3. © 1993 John Wiley & Sons, Inc. 相似文献
38.
We consider an optimal growth (multi-sector) model with nonconvex technology. Using the Clarke results on generalized gradients, we prove that the value function has left and right derivatives with respect to the initial capital stock, without requiring supermodularity assumptions. 相似文献
39.
R. Grac M. Pugnet J.H. Collet B. Lambert C. De Matos H. L'Haridon A. Le Corre J.O. White 《Superlattices and Microstructures》1997,22(4):505-509
We report new results on the diffraction properties of photoinduced gratings in InGaAs/InGaAsP MQW structures. The original feature of this device is that the QWs are enclosed in an asymmetric Fabry–Perot microcavity in order to increase the diffraction efficiency. We observe oscillations in the diffraction efficiency due to resonant effects in the microcavity. The experimental spectra are compared with theory. Diffraction efficiency at 1.55 μm attains a maximum value of 2.7% at a write beam fluence of 260 μ J cm−2, and then decreases at higher fluences. We explain this phenomenon by an absorption saturation at high excitation. 相似文献
40.