全文获取类型
收费全文 | 10956篇 |
免费 | 357篇 |
国内免费 | 85篇 |
专业分类
化学 | 7432篇 |
晶体学 | 99篇 |
力学 | 315篇 |
综合类 | 1篇 |
数学 | 1662篇 |
物理学 | 1889篇 |
出版年
2023年 | 67篇 |
2022年 | 131篇 |
2021年 | 135篇 |
2020年 | 218篇 |
2019年 | 188篇 |
2018年 | 136篇 |
2017年 | 149篇 |
2016年 | 282篇 |
2015年 | 205篇 |
2014年 | 260篇 |
2013年 | 526篇 |
2012年 | 615篇 |
2011年 | 743篇 |
2010年 | 387篇 |
2009年 | 290篇 |
2008年 | 625篇 |
2007年 | 631篇 |
2006年 | 596篇 |
2005年 | 567篇 |
2004年 | 532篇 |
2003年 | 363篇 |
2002年 | 361篇 |
2001年 | 118篇 |
2000年 | 112篇 |
1999年 | 103篇 |
1998年 | 99篇 |
1997年 | 126篇 |
1996年 | 163篇 |
1995年 | 99篇 |
1994年 | 79篇 |
1993年 | 112篇 |
1992年 | 87篇 |
1991年 | 91篇 |
1990年 | 83篇 |
1989年 | 73篇 |
1988年 | 89篇 |
1987年 | 68篇 |
1985年 | 131篇 |
1984年 | 145篇 |
1983年 | 97篇 |
1982年 | 122篇 |
1981年 | 125篇 |
1980年 | 105篇 |
1979年 | 92篇 |
1978年 | 123篇 |
1977年 | 102篇 |
1976年 | 90篇 |
1975年 | 72篇 |
1974年 | 73篇 |
1973年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Alex M. Green David G. Gevaux Christine Roberts Chris C. Phillips 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):531
In this paper we outline the use of resonant-cavity enhancement for increasing the exterior coupling efficiency of photodetectors and light-emitting diodes (LEDs) in the mid-infrared (MIR) spectral region. This method is potentially very important in the MIR because encapsulation is not presently feasible due to the lack of suitable materials. Among other potential applications, resonant-cavity-enhanced (RCE) photodetectors and LEDs could be particularly suitable for greenhouse gas detection because of their ‘pre-tunable’ spectrally narrowed resonantly enhanced peaks. We also present the optical characterization of an InAs RCE photodetector aimed at the detection of methane gas (λ≈3.3 μm), and an InAs/InAs0.91Sb0.09 resonant-cavity LED (RCLED) aimed at carbon dioxide gas (λ≈4.2 μm). The high peak responsivity of the RCE photodetector was 34.7 A/W at λ=3.14 μm, and the RCLED peaked at λ=3.96 μm. These are among the longest operating wavelengths for III–V RCE photodetectors and RCLEDs reported in the literature. 相似文献
52.
53.
Alex Charles Cumming 《Fresenius' Journal of Analytical Chemistry》1911,50(2):111-112
Ohne Zusammenfassung 相似文献
54.
Let G = (V,E) be a graph or digraph and r : V → Z+. An r‐detachment of G is a graph H obtained by ‘splitting’ each vertex ν ∈ V into r(ν) vertices. The vertices ν1,…,νr(ν) obtained by splitting ν are called the pieces of ν in H. Every edge uν ∈ E corresponds to an edge of H connecting some piece of u to some piece of ν. Crispin Nash‐Williams 9 gave necessary and sufficient conditions for a graph to have a k‐edge‐connected r‐detachment. He also solved the version where the degrees of all the pieces are specified. In this paper, we solve the same problems for directed graphs. We also give a simple and self‐contained new proof for the undirected result. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 67–77, 2003 相似文献
55.
Francis J. Narcowich Joseph D. Ward Holger Wendland. 《Mathematics of Computation》2005,74(250):743-763
In this paper we discuss Sobolev bounds on functions that vanish at scattered points in a bounded, Lipschitz domain that satisfies a uniform interior cone condition. The Sobolev spaces involved may have fractional as well as integer order. We then apply these results to obtain estimates for continuous and discrete least squares surface fits via radial basis functions (RBFs). These estimates include situations in which the target function does not belong to the native space of the RBF.
56.
In this paper a new proof of an identity of Giacomin, Olla, and Spohn is given. The identity relates the 2 point correlation function of a Euclidean field theory to the expectation of the Green's function for a pde with random coefficients. The Euclidean field theory is assumed to have convex potential. An inequality of Brascamp and Lieb therefore implies Gaussian bounds on the Fourier transform of the 2 point correlation function. By an application of results from random pde, the previously mentioned identity implies pointwise Gaussian bounds on the 2 point correlation function. 相似文献
57.
We solve a bitangential interpolation problem for contractive multipliers
on the Arveson space with an arbitrary interpolating set in the closed
unit ball . The solvability criterion is established in terms of positive
kernels. The set of all solutions is parametrized by a Redheffer transform.
Submitted: February 2, 2002. 相似文献
58.
Soluble catalysts for the Juliá-Colonna asymmetric epoxidation reaction have been constructed in three different ways, using NH2-PEG-OMe as the support system: suitable solvents have been identified and it is shown that the degree of helicity of the conjugates correlates with the extent of conversion and (to a lesser extent) the enantioselectivity of epoxidation. 相似文献
59.
60.
Anita M. R. Fisher Kathleen Danenberg Debabrata Banerjee Joseph R. Bertino Peter Danenberg Charles J. Gomer 《Photochemistry and photobiology》1997,66(2):265-270
Loss of p53 function has been correlated with decreased sensitivity to chemotherapy and radiation therapy in a variety of human tumors. Comparable analysis of p53 status with sensitivity to oxidative stress induced by pho-todynamic therapy has not been reported. In the current study we examined photosensitivity in human promye-locytic leukemia HL60 cells exhibiting either wild-type p53, mutated p53 or deleted p53 expression. Experiments were performed using a purpurin, tin ethyl etiopurpurin (SnET2)-, or a porphyrin, Photofrin (PH)-based photo-sensitizer. Total SnET2 accumulation was comparable in all three cell lines. Uptake of PH was highest in cells expressing wild-type p53 but incubation conditions could be adjusted to achieve equivalent cellular PH levels during experiments that analyzed photosensitivity. Survival measurements demonstrated that HL60 cells expressing wild-type p53 were more sensitive to PH- and SnET2-mediated photosensitization, as well as to UVC irradiation, when compared to HL60 cells exhibiting deleted or mutated p53 phenotypes. A rapid apoptotic response was observed following purpurin- and porphyrin-induced photosensitization in all cell lines. Results of this study indicate that photosensitivity is increased in HL60 cells expressing wild-type p53 and that photosensitizer-medi-ated oxidative stress can induce apoptosis through a p53-independent mechanism in HL60 cells . 相似文献