全文获取类型
收费全文 | 4916篇 |
免费 | 169篇 |
国内免费 | 6篇 |
专业分类
化学 | 3498篇 |
晶体学 | 24篇 |
力学 | 84篇 |
数学 | 582篇 |
物理学 | 903篇 |
出版年
2023年 | 27篇 |
2022年 | 27篇 |
2021年 | 36篇 |
2020年 | 64篇 |
2019年 | 63篇 |
2018年 | 37篇 |
2017年 | 35篇 |
2016年 | 105篇 |
2015年 | 117篇 |
2014年 | 131篇 |
2013年 | 207篇 |
2012年 | 220篇 |
2011年 | 273篇 |
2010年 | 153篇 |
2009年 | 122篇 |
2008年 | 222篇 |
2007年 | 238篇 |
2006年 | 195篇 |
2005年 | 217篇 |
2004年 | 197篇 |
2003年 | 145篇 |
2002年 | 138篇 |
2001年 | 100篇 |
2000年 | 103篇 |
1999年 | 86篇 |
1998年 | 86篇 |
1997年 | 90篇 |
1996年 | 93篇 |
1995年 | 65篇 |
1994年 | 84篇 |
1993年 | 83篇 |
1992年 | 57篇 |
1991年 | 53篇 |
1990年 | 55篇 |
1989年 | 51篇 |
1988年 | 49篇 |
1987年 | 52篇 |
1986年 | 61篇 |
1985年 | 75篇 |
1984年 | 83篇 |
1983年 | 57篇 |
1982年 | 70篇 |
1981年 | 42篇 |
1980年 | 66篇 |
1979年 | 57篇 |
1978年 | 51篇 |
1977年 | 69篇 |
1976年 | 39篇 |
1974年 | 37篇 |
1973年 | 26篇 |
排序方式: 共有5091条查询结果,搜索用时 15 毫秒
1.
2.
Dr. Jun Zeng Dr. Zhichao Wang Dr. Xin Huang Dr. Sabine S. Eckstein Prof. Dr. Xiaohui Lin Prof. Dr. Hailong Piao Prof. Dr. Cora Weigert Dr. Peiyuan Yin Prof. Dr. Rainer Lehmann Prof. Dr. Guowang Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(21):5427-5432
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism. 相似文献
3.
Rainer Löwen 《Journal of Geometry》1989,36(1-2):110-116
We prove that a spread S over a locally compact nondlscrete field F defines a topological translation plane if and only if the spread is compact. For F=R, this is implicit in Breuning's thesis [Bre], cf. [B 2]. For the proof, we describe the point set of the projective translation plane as a quotient space of some projective space, with identifications taking place in one hyperplane. This is new even for F=R. 相似文献
4.
Johannes Elschner Rainer Hinder Gunther Schmidt 《Advances in Computational Mathematics》2002,16(2-3):139-156
This paper is devoted to the numerical study of diffraction by periodic structures of plane waves under oblique incidence. For this situation Maxwell's equations can be reduced to a system of two Helmholtz equations in R
2 coupled via quasiperiodic transmission conditions on the piecewise smooth interfaces between different materials. The numerical analysis is based on a strongly elliptic variational formulation of the differential problem in a bounded periodic cell involving nonlocal boundary operators. We obtain existence and uniqueness results for discrete solutions and provide the corresponding error analysis. 相似文献
5.
H. G. Bohlen W. von Oertzen R. Kalpakchieva B. Gebauer S. M. Grimes A. Lenz T. N. Massey M. Milin Ch. Schulz Tz. Kokalova S. Torilov S. Thummerer 《Physics of Atomic Nuclei》2003,66(8):1494-1500
The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion-induced transfer reactions. In neutron transfer reactions, the population of final states shows a strong sensitivity to the chosen core nucleus, i.e., the target nuclei 9Be or 10Be, respectively. Molecular rotational bands up to high excitation energies are observed with 9Be as the core due to its pronounced 2α-cluster structure, whereas only a few states at low excitation energies are populated with 10Be as the core. For 11Be, a detailed investigation has been performed for the three states at 3.41, 3.89, and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2+, 5/2?, and 3/2?, respectively. Furthermore, we have studied particle-hole states of 16C using the 13C(12C, 9C)16C reaction and found 14 previously unknown states. Using the 12C(12C, 9C)15C reaction, five new states were observed for 15C. 相似文献
6.
7.
8.
[3,3]-Sigmatropic rearrangements of allyl tetronates and allyl tetramates to give 3-allyltetronic or -tetramic acids, respectively, proceed within 20-60 min under microwave irradiation (300 W, 130-190 °C). Consecutive (homo)sigmatropic [1,5] H-shifts such as oxa-ene reactions are promoted less effectively, which allows the isolation of Claisen intermediates of sigmatropic domino sequences, in contrast to conventional heating. 相似文献
9.
We introduce a new technique for imaging oxygen concentrations in fuel/air mixtures that takes advantage of the different
responses of toluene and 3-pentanone to collisional quenching by molecular oxygen. Since laser-induced fluorescence signals
from both tracers upon excitation at 248 nm are spectrally well separated, simultaneous detection is possible. The technique
is first applied to instantaneous imaging in turbulent mixing processes of interacting seeded air and nitrogen flows.
Received: 1 August 2001 / Revised version: 29 October 2001 / Published online: 29 November 2001 相似文献
10.
Summary The solubility parameters of cationic surfactants were obtained using the inverse gas chromatographic technique. The surfactants
didodecyl dimethyl ammonium bromide, dioctadecyl dimethyl ammonium bromide and dodecyl pyridinium chloride were used as stationary
phase and retention data of different probe solutes were measured at different temperatures. The results were analysed by
the combination of Flory-Huggins and Hildebrand theories, and the solubility parameters of the surfactants were obtained in
a range of temperatures between 80–120°C. 相似文献