全文获取类型
收费全文 | 1878篇 |
免费 | 39篇 |
国内免费 | 8篇 |
专业分类
化学 | 1363篇 |
晶体学 | 13篇 |
力学 | 38篇 |
数学 | 202篇 |
物理学 | 309篇 |
出版年
2022年 | 10篇 |
2021年 | 31篇 |
2020年 | 28篇 |
2019年 | 28篇 |
2018年 | 24篇 |
2017年 | 15篇 |
2016年 | 44篇 |
2015年 | 35篇 |
2014年 | 26篇 |
2013年 | 79篇 |
2012年 | 86篇 |
2011年 | 125篇 |
2010年 | 61篇 |
2009年 | 56篇 |
2008年 | 106篇 |
2007年 | 91篇 |
2006年 | 99篇 |
2005年 | 87篇 |
2004年 | 90篇 |
2003年 | 75篇 |
2002年 | 57篇 |
2001年 | 39篇 |
2000年 | 29篇 |
1999年 | 13篇 |
1998年 | 19篇 |
1997年 | 14篇 |
1996年 | 28篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 23篇 |
1992年 | 18篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 15篇 |
1987年 | 17篇 |
1985年 | 50篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 33篇 |
1981年 | 26篇 |
1980年 | 24篇 |
1979年 | 29篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 18篇 |
1974年 | 18篇 |
1972年 | 13篇 |
1968年 | 9篇 |
排序方式: 共有1925条查询结果,搜索用时 15 毫秒
1.
Given a1,a2,...,an ∈ ℤ^d$, we examine the set, G, of all non-negative integer combinations of these ai. In particular, we examine the generating function f(z) = ∑b ∈ Gzb. We prove that one can write this generating function as a rational function using the neighborhood complex (sometimes called
the complex of maximal lattice-free bodies or the Scarf complex) on a particular lattice in ℤn. In the generic case, this follows from algebraic results of Bayer and Sturmfels. Here we prove it geometrically in all
cases, and we examine a generalization involving the neighborhood complex on an arbitrary lattice. 相似文献
2.
Small‐Angle Neutron Scattering has been performed from poly(ethylene oxide) in deuterated water at temperature ranging from 10 to 80 °C. A simple fitting model was used to obtain a correlation length and a Porod exponent. The correlation length L characterizes the average distance between entanglements in the semidilute region and is proportional to the individual coil sizes in the dilute region. L was found to increase with temperature in the semidilute region but it decreases with temperature in the dilute region. This decrease is the precursor to the single‐chain collapse which applies to very dilute polymer solutions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2196–2200, 2007 相似文献
3.
4.
We prove lower bounds of the form exp(nε d), εd > 0, on the length of proofs of an explicit sequence of tautologies, based on the Pigeonhole Principle, in proof systems using formulas of depth d, for any constant d. This is the largest lower bound for the strongest proof system, for which any superpolynomial lower bounds are known. 相似文献
5.
6.
D. Seweryniak P. J. Woods B. Blank M. P. Carpenter T. Davinson S. J. Freeman J. Grres A. Heinz R. V. F. Janssens H. Mahmud T. L. Khoo Z. Liu G. Mukherjee E. Rehm F. Sarazin J. Shergur M. Shawcross S. Sinha A. Woehr 《Physics letters. [Part B]》2004,590(3-4):170-175
The fusion–evaporation reaction 10B(12C, 2n) was used to make the first observation of in-beam γ decays from the astrophysically important nucleus 20Na, lying adjacent to the proton drip-line. All states below the proton threshold in 20Na were populated and identified in the experiment. These include new levels, previously unresolved levels, and states located with improved energy precision. The level structure of 20Na, and its γ transitions, are compared to the mirror partner 20F measured simultaneously in this experiment. In particular, a high degree of energy stability is found for all negative parity states. These results are discussed in the context of the nuclear shell model. 相似文献
7.
Patterson JR Barker A Briere RA Gibbons LK Makoff G Papadimitriou V Somalwar S Wah YW Winstein B Winston R Woods M Yamamoto H Swallow E Bock GJ Coleman R Enagonio J Hsiung YB Stanfield K Stefanski R Yamanaka T Blair G Gollin GD Karlsson M Okamitsu JK Tschirhart R Brisson JC Debu P Peyaud B Turlay R Vallage B 《Physical review letters》1990,64(13):1491-1494
8.
9.
10.
Since the early reports of MOFs and their interesting properties, research involving these materials has grown wide in scope and applications. Various synthetic approaches have ensued in view of obtaining materials with optimised properties, the extensive scope of application spanning from energy, gas sorption, catalysis biological applications has meant exponentially evolved over the years. The far‐reaching synthetic and PSM approaches and porosity control possibilities have continued to serve as a motivation for research on these materials. With respect to the biological applications, MOFs have shown promise as good candidates in applications involving drug delivery, BioMOFs, sensing, imaging amongst others. Despite being a while away from successful entry into the market, observed results in sensing, drug delivery, and imaging put these materials on the spot light as candidates poised to usher in a revolution in biology. In this regard, this review article focuses current approaches in synthesis, post functionalization and biological applications of these materials with particular attention on drug delivery, imaging, sensing and BioMOFs. 相似文献