全文获取类型
收费全文 | 6428篇 |
免费 | 250篇 |
国内免费 | 60篇 |
专业分类
化学 | 4560篇 |
晶体学 | 22篇 |
力学 | 152篇 |
数学 | 1067篇 |
物理学 | 937篇 |
出版年
2024年 | 7篇 |
2023年 | 44篇 |
2022年 | 147篇 |
2021年 | 201篇 |
2020年 | 130篇 |
2019年 | 136篇 |
2018年 | 132篇 |
2017年 | 108篇 |
2016年 | 252篇 |
2015年 | 241篇 |
2014年 | 251篇 |
2013年 | 413篇 |
2012年 | 438篇 |
2011年 | 525篇 |
2010年 | 320篇 |
2009年 | 252篇 |
2008年 | 451篇 |
2007年 | 411篇 |
2006年 | 413篇 |
2005年 | 343篇 |
2004年 | 296篇 |
2003年 | 221篇 |
2002年 | 201篇 |
2001年 | 61篇 |
2000年 | 69篇 |
1999年 | 42篇 |
1998年 | 65篇 |
1997年 | 56篇 |
1996年 | 60篇 |
1995年 | 36篇 |
1994年 | 32篇 |
1993年 | 34篇 |
1992年 | 38篇 |
1991年 | 32篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 24篇 |
1984年 | 31篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 5篇 |
1973年 | 9篇 |
排序方式: 共有6738条查询结果,搜索用时 0 毫秒
61.
Diogo de Andrade Nuno Fachada Carlos M. Fernandes Agostinho C. Rosa 《Entropy (Basel, Switzerland)》2020,22(11)
We present a generative swarm art project that creates 3D animations by running a Particle Swarm Optimization algorithm over synthetic landscapes produced by an objective function. Different kinds of functions are explored, including mathematical expressions, Perlin noise-based terrain, and several image-based procedures. A method for displaying the particle swarm exploring the search space in aesthetically pleasing ways is described. Several experiments are detailed and analyzed and a number of interesting visual artifacts are highlighted. 相似文献
62.
63.
FRANCK-CONDON FACTORS AND R-CENTROIDS FOR THE GREEN-YELLOW SYSTEM OF LA16O AND LA18O ARE REPORTED. CALCULATION INCLUDES ROTATION-VIBRATION INTERACTION, AND A SIGNIFICANT VARIATION WHEN THE ROTATIONAL QUANTUM NUMBER CHANGES HAS BEEN FOUND. 相似文献
64.
Gouy wave modes are linear waves with finite energy that propagate without distortion at any phase and group velocity through a focal region in a dispersive medium. These features make them potentially useful for the onset and control of nonlinear interactions. 相似文献
65.
Carlos Guerrero-Sanchez 《Applied Surface Science》2006,252(7):2555-2561
The application of combinatorial and high-throughput approaches in polymer research is described. An overview of the utilized synthesis robots is given, including different parallel synthesizers and a process development robot. In addition, the application of the parallel synthesis robots to reversible addition fragmentation termination (RAFT) radical polymerizations and ionic copolymerizations is overviewed. Moreover, first results concerning the process development of semi-batch free radical polymerizations are described. 相似文献
66.
Ultrasound treatment favors enzymatic attack on vegetal materials and influences biological activity. The objective of this study was to develop substrates for Saccharomyces cerevisiae based on the hydrothermal treatment and ultrasound treatment of pine needle biomass. The samples subjected to ultrasound treatment at 550?°C and 650?°C showed higher reflectance bands at around 200?nm after 80?min of ultrasound treatment and lower band gap energies associated with lower IC30 values. The hydrothermal treatment with 100?min of ultrasound treatment generated more promising materials for the use of the substrates with the eukaryotic model S. cerevisiae. 相似文献
67.
The general features of two series of sol-gel derived materials, designatedurethanesils (Ut), have been investigated by infrared and Raman spectroscopies with the goal of elucidating the chemical environment of
the Eu3+ cations.
The host frameworks of the two families of ormolytes studied have been represented by m-Ut(350) and d-Ut(300), where m stands
for mono, d stands for di, 350 and 300 are the average molecular weights of the organic precursors (poly(ethylene glycol)
methyl ether, PEGME, and poly(ethylene glycol), PEG, respectively).
The hybrid matrix of the mono-xerogels is composed by a siliceous backbone bonded by means of urethane linkages (-NHC (=O)O-)
to pendant methyl end capped oligopolymer chains with approximately 7 oxyethylene units, whereas that of the di-xerogels is
based on a siliceous network grafted through urethane groups to both ends of poly(oxyethylene) segments containing about 6
(OCH2CH2) repeat units.
Both classes of materials have been doped with europium triflate (Eu(CF3SO3)3). The doped samples have been identified by m-Ut(350)nEu(CF3SO3)3 and d-Ut(300)nEu(CF3SO3), where n is the molar ratio of (OCH2CH2) repeat units per Eu3+ ion. Materials with n ranging from ∞ to 5 have been analyzed. The spectral data obtained provide evidence that the cations
begin to coordinate to the ether oxygen atoms of the oligopolymer chains at n=40 in the mono-urethanesils and at n=10 in the
di-urethanesils. In mono-urethanesils samples with n>40 and in di-urethanesils materials with n>10, the Eu3+ coordinate exclusively to the carbonyl oxygen atoms of the urethane linkages.
Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001. 相似文献
68.
AbstractThis article presents an overview of optical methodologies to aid the diagnosis and differentiation of thyroid and parathyroid tissues. In particular, we review the several techniques and associated methodologies that allow in vivo and ex vivo optical characterization of thyroid and parathyroid tissues. Emphasis is placed on the research potential of these techniques and whether intrinsic characteristics can provide useful contrast for the diagnosis of human thyroid and parathyroid malignant lesions. 相似文献
69.
70.