全文获取类型
收费全文 | 8955篇 |
免费 | 208篇 |
国内免费 | 64篇 |
专业分类
化学 | 6063篇 |
晶体学 | 85篇 |
力学 | 253篇 |
综合类 | 2篇 |
数学 | 1336篇 |
物理学 | 1488篇 |
出版年
2022年 | 115篇 |
2021年 | 110篇 |
2020年 | 166篇 |
2019年 | 126篇 |
2018年 | 99篇 |
2017年 | 105篇 |
2016年 | 206篇 |
2015年 | 156篇 |
2014年 | 204篇 |
2013年 | 416篇 |
2012年 | 480篇 |
2011年 | 587篇 |
2010年 | 300篇 |
2009年 | 232篇 |
2008年 | 500篇 |
2007年 | 460篇 |
2006年 | 451篇 |
2005年 | 455篇 |
2004年 | 437篇 |
2003年 | 297篇 |
2002年 | 317篇 |
2001年 | 95篇 |
2000年 | 92篇 |
1999年 | 72篇 |
1998年 | 84篇 |
1997年 | 101篇 |
1996年 | 140篇 |
1995年 | 88篇 |
1994年 | 73篇 |
1993年 | 103篇 |
1992年 | 73篇 |
1991年 | 82篇 |
1990年 | 77篇 |
1989年 | 58篇 |
1988年 | 75篇 |
1987年 | 61篇 |
1986年 | 55篇 |
1985年 | 113篇 |
1984年 | 132篇 |
1983年 | 91篇 |
1982年 | 114篇 |
1981年 | 111篇 |
1980年 | 93篇 |
1979年 | 84篇 |
1978年 | 110篇 |
1977年 | 95篇 |
1976年 | 82篇 |
1975年 | 67篇 |
1974年 | 68篇 |
1973年 | 59篇 |
排序方式: 共有9227条查询结果,搜索用时 78 毫秒
91.
Joseph R. Lakowicz Zakir Murtaza Wayne E. Jones Jr. Kihan Kim Henryk Szmacinski 《Journal of fluorescence》1996,6(4):245-249
We report the first observation of polarized emission from a rhenium-phenanthroline complex, Re(CO)3(phen)Cl. Highly luminescent rhenium complexes are known, with quantum yields near 0.5 and lifetimes in excess of 10 s. The detection of polarized emission suggests the use of rhenium complexes as probes of the hydrodynamics of large macromolecular complexes and for use in fluorescence polarization immunoassays with gated detection. 相似文献
92.
The purpose of this paper is to establish a conjecture of B. Grünbaum, which states that in every n-polygon P in the plane, n 5, some diagonals intersect in a pattern that defines a new n-polygon (P), such that the product of the cross-rations on the diagonals of P is equal to the product of the corresponding cross-ratios on the diagonals of (P). 相似文献
93.
Darensbourg DJ Maynard EL Holtcamp MW Klausmeyer KK Reibenspies JH 《Inorganic chemistry》1996,35(9):2682-2684
94.
95.
96.
97.
Peggy S. Eis Józef Kuśba Michael L. Johnson Joseph R. Lakowicz 《Journal of fluorescence》1993,3(1):23-31
Time-resolved fluorescence resonance energy transfer (FRET) measurements were used to measure distance distributions and intramolecular dynamics (site-to-site diffusion) of a 28-residue single-domain zinc finger peptide in the absence and presence of zinc ion. Energy transfer was measured between TRP14 and a N-terminal DNS group. As expected, the TRP-to-DNS distance distribution for zinc-bound peptide is shorter and narrower (R
av=11.2 Å,hw=2.8 Å) than the metal-free peptide (R
av=20.1 Å,hw=14.5 Å). The degree of mutual donor-to-acceptor diffusion (D) was also determined for these distributions. For zinc-bound peptide there is no detectible diffusion (D0.2 Å2/ns), whereas for metal-free peptide a considerable amount of motion is occurring between the donor and the acceptor (D=12 Å2/ns). These results indicate that the zinc-bound peptide folds into a unique, well-defined conformation, whereas the metal-free conformation is flexible and rapidly changing. The absence of detectible mutual site-to-site diffusion between the donor and the acceptor in the metal-bound zinc finger peptide indicates that intramolecular motion is essentially frozen out, on the FRET time scale, as a consequence of zinc coordination.Dedicated to the memory of Barbara D. Wells. 相似文献
98.
Bogumil Zelent Józef Kuśba Ignacy Gryczynski Michael L. Johnson Joseph R. Lakowicz 《Journal of fluorescence》1993,3(3):199-207
We examined the time-dependent intensity decays ofN-acetyl-l-tryptophanamide (NATA) when collisionally quenched by acrylamide in propylene glycol over a range of temperatures. The intensity decays of NATA became increasingly heterogeneous in the presence of acrylamide. The NATA intensity decays were not consistent with the Collins-Kimball radiation boundary condition (RBC) model for quenching. The steady-state Stern-Volmer plots show significant upward curvature, and quenching of NATA by acrylamide was observed even in vitrified propylene glycol, where translational diffusion cannot occur during the lifetime of the excited state. These frequencydomain and steady-state data indicate a through-space quenching interaction between NATA and acrylamide, and the results are consistent with a rate constant for quenching that depends exponentially on the fluorophore-quencher separation distance. The exponential distance-dependent rate of quenching also explains the upward curvature of the Stern-Volmer plot, and the steady-state data aid in determining the interaction distance between NATA and acrylamide. These results suggest that the distance-dependent quenching rates need to be considered in the interpretation of acrylamide quenching of proteins. 相似文献
99.
Summary In earlier works, the gauge theorem was proved for additive functionals of Brownian motion of the form
0
t
q(B
s
)ds, whereq is a function in the Kato class. Subsequently, the theorem was extended to additive functionals with Revuz measures in the Kato class. We prove that the gauge theorem holds for a large class of additive functionals of zero energy which are, in general, of unbounded variation. These additive functionals may not be semi-martingales, but correspond to a collection of distributions that belong to the Kato class in a suitable sense. Our gauge theorem generalizes the earlier versions of the gauge theorem.Research supported in part by NSA grant MDA-92-H-30324 相似文献
100.
Ingo Althöfer Gautam Das David Dobkin Deborah Joseph José Soares 《Discrete and Computational Geometry》1993,9(1):81-100
Given a graphG, a subgraphG' is at-spanner ofG if, for everyu,v V, the distance fromu tov inG' is at mostt times longer than the distance inG. In this paper we give a simple algorithm for constructing sparse spanners for arbitrary weighted graphs. We then apply this algorithm to obtain specific results for planar graphs and Euclidean graphs. We discuss the optimality of our results and present several nearly matching lower bounds.The work of G. Das and D. Joseph was supported by NSF PYI Grant DCR-8402375. The work of D. Dobkin was supported by NSF Grant CCR-8700917. The work of J. Soares was supported by CNPq proc 203039/87.4 (Brazil) and NSF Grant CCR-9014562. This research was accomplished while G. Das was a student at the University of Wisconsin-Madison. A preliminary version was presented at the Second Scandinavian Workshop on Algorithm Theory, Bergen, Norway, 1990, under the title Generating Sparse Spanners for Weighted Graphs, and proceedings appear in the series Lecture Notes in Computer Science, Springer-Verlag. The preliminary version also appears as Princeton University Technical Report CS-TR-261-90, and as University of Wisconsin-Madison Computer Sciences Technical Report 882. 相似文献