全文获取类型
收费全文 | 600485篇 |
免费 | 22173篇 |
国内免费 | 10553篇 |
专业分类
化学 | 321838篇 |
晶体学 | 7996篇 |
力学 | 29571篇 |
综合类 | 525篇 |
数学 | 80980篇 |
物理学 | 192301篇 |
出版年
2022年 | 5078篇 |
2021年 | 5869篇 |
2020年 | 6721篇 |
2019年 | 6368篇 |
2018年 | 14600篇 |
2017年 | 15057篇 |
2016年 | 14039篇 |
2015年 | 9562篇 |
2014年 | 11599篇 |
2013年 | 25543篇 |
2012年 | 26012篇 |
2011年 | 36829篇 |
2010年 | 23278篇 |
2009年 | 23055篇 |
2008年 | 31343篇 |
2007年 | 33943篇 |
2006年 | 20672篇 |
2005年 | 24703篇 |
2004年 | 19060篇 |
2003年 | 16804篇 |
2002年 | 14674篇 |
2001年 | 14628篇 |
2000年 | 11606篇 |
1999年 | 9598篇 |
1998年 | 8016篇 |
1997年 | 7823篇 |
1996年 | 7831篇 |
1995年 | 7088篇 |
1994年 | 6616篇 |
1993年 | 6195篇 |
1992年 | 6713篇 |
1991年 | 6563篇 |
1990年 | 6107篇 |
1989年 | 5783篇 |
1988年 | 5907篇 |
1987年 | 5433篇 |
1986年 | 5286篇 |
1985年 | 7213篇 |
1984年 | 7280篇 |
1983年 | 5955篇 |
1982年 | 6387篇 |
1981年 | 6334篇 |
1980年 | 6052篇 |
1979年 | 6308篇 |
1978年 | 6406篇 |
1977年 | 6247篇 |
1976年 | 6235篇 |
1975年 | 6080篇 |
1974年 | 5988篇 |
1973年 | 6176篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
2.
In this article, we construct and analyze a residual-based a posteriori error estimator for a quadratic finite volume method (FVM) for solving nonlinear elliptic partial differential equations with homogeneous Dirichlet boundary conditions. We shall prove that the a posteriori error estimator yields the global upper and local lower bounds for the norm error of the FVM. So that the a posteriori error estimator is equivalent to the true error in a certain sense. Numerical experiments are performed to illustrate the theoretical results. 相似文献
3.
Kai Cheng Xiao-Shuai Zhang Jie An Cheng Li Ruo-Yun Zhang Run Ye Prof. Dr. Bang-Jiao Ye Prof. Dr. Bo Liu Prof. Dr. Yuan-Di Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(31):7553-7560
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA. 相似文献
4.
5.
Paired single residue‐transposed Lys‐N and Lys‐C digestions for label‐free identification of N‐terminal and C‐terminal MS/MS peptide product ions: ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry for peptide de novo sequencing 下载免费PDF全文
6.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry 下载免费PDF全文
7.
ABSTRACTThe Coupled-Cluster (CC) theory is one of the most successful high precision methods used to solve the stationary Schrödinger equation. In this article, we address the mathematical foundation of this theory with focus on the advances made in the past decade. Rather than solely relying on spectral gap assumptions (non-degeneracy of the ground state), we highlight the importance of coercivity assumptions – Gårding type inequalities – for the local uniqueness of the CC solution. Based on local strong monotonicity, different sufficient conditions for a local unique solution are suggested. One of the criteria assumes the relative smallness of the total cluster amplitudes (after possibly removing the single amplitudes) compared to the Gårding constants. In the extended CC theory the Lagrange multipliers are wave function parameters and, by means of the bivariational principle, we here derive a connection between the exact cluster amplitudes and the Lagrange multipliers. This relation might prove useful when determining the quality of a CC solution. Furthermore, the use of an Aubin–Nitsche duality type method in different CC approaches is discussed and contrasted with the bivariational principle. 相似文献
8.
9.
A Savitzky–Golay filtering for smoothing and peak search written in Python is presented in this paper alongside its applications in the list-mode digital data acquisition dual gamma–gamma coincidence bismuth germanate (BGO) detector. The study has demonstrated that the software provides a reliable and effective way to quantify trace amounts of 22Na and 7Be in aerosol samples collected at Resolute Bay, Canada with a critical limit of 3 mBq and 5 Bq respectively for a 20 h counting interval, which are believed to be the inherent limitations of the dual-BGO system.
相似文献10.