全文获取类型
收费全文 | 3168篇 |
免费 | 105篇 |
国内免费 | 18篇 |
专业分类
化学 | 2077篇 |
晶体学 | 19篇 |
力学 | 81篇 |
数学 | 483篇 |
物理学 | 631篇 |
出版年
2023年 | 20篇 |
2022年 | 58篇 |
2021年 | 73篇 |
2020年 | 53篇 |
2019年 | 49篇 |
2018年 | 43篇 |
2017年 | 42篇 |
2016年 | 103篇 |
2015年 | 91篇 |
2014年 | 79篇 |
2013年 | 175篇 |
2012年 | 192篇 |
2011年 | 214篇 |
2010年 | 113篇 |
2009年 | 129篇 |
2008年 | 182篇 |
2007年 | 195篇 |
2006年 | 188篇 |
2005年 | 175篇 |
2004年 | 170篇 |
2003年 | 133篇 |
2002年 | 123篇 |
2001年 | 46篇 |
2000年 | 38篇 |
1999年 | 33篇 |
1998年 | 28篇 |
1997年 | 23篇 |
1996年 | 46篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 26篇 |
1989年 | 16篇 |
1988年 | 19篇 |
1987年 | 8篇 |
1986年 | 17篇 |
1985年 | 35篇 |
1984年 | 22篇 |
1983年 | 21篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 28篇 |
1979年 | 27篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1975年 | 7篇 |
1974年 | 11篇 |
1973年 | 7篇 |
排序方式: 共有3291条查询结果,搜索用时 15 毫秒
1.
2.
3.
de Santana Felipe Silva Gracioso Louise Hase Karolski Bruno dos Passos Galluzzi Baltazar Marcela Mendes Maria Anita do Nascimento Claudio Augusto Oller Perpetuo Elen Aquino 《Applied biochemistry and biotechnology》2019,189(1):103-115
Applied Biochemistry and Biotechnology - The human exposure to bisphenol A (BPA) occurs frequently. Once, this compound was one of the highest volume chemicals produced worldwide and used as a... 相似文献
4.
Claudio Simeone 《General Relativity and Gravitation》2002,34(11):1887-1893
A consistent quantization with a clear notion of time and evolution is given for the anisotropic Kantowski–Sachs cosmological model. It is shown that a suitable coordinate choice allows to obtain a solution of the Wheeler–DeWitt equation in the form of definite energy states, and that the results can be associated to two disjoint equivalent theories, one for each sheet of the constraint surface. 相似文献
5.
NMR screening techniques in drug discovery and drug design 总被引:7,自引:0,他引:7
Brian J. Stockman Claudio Dalvit 《Progress in Nuclear Magnetic Resonance Spectroscopy》2002,41(3-4):187-231
6.
A time discrete scheme is used to approximate the solution toa phase field system of PenroseFife type with a non-conservedorder parameter. An a posteriori error estimate is presentedthat allows the estimation of the difference between continuousand semidiscrete solutions by quantities that can be calculatedfrom the approximation and given data. 相似文献
7.
R. Pizzoferrato L. Lagonigro T. Ziller A. Di Carlo R. Paolesse F. Mandoj A. Ricci C. Lo Sterzo 《Chemical physics》2004,300(1-3):217-225
We study the infrared emission at 1.54 μm of an organolanthanide complex, Er(III)-tetraphenylporphyrin [Er(TPP)acac], both as a result of direct optical excitation and via energy transfer from host π-conjugate polymers of type poly(arylene–ethynylene) [PAE]. In the first case, the emission of the neat complex is characterized in inert transparent materials and a value of the quantum yield at 1.54 μm φIR=4×10−4 is measured. Then, fluorescence resonance transfer is investigated in blends of Er(TPP)acac with PAEs by monitoring the quenching of the polymer fluorescence along with the enhancement of both the visible emission of the ligand and the near-infrared band of Er3+. These different procedures allow a detailed analysis of the transfer efficiency within a specific implementation of the Förster model for polymeric donors. The experimental values of the critical radius R0, ranging from 1.3 to 2.5 nm for the different blends, are in good agreement with theory for a wide interval of the physical and spectroscopic parameters. This suggests that other mechanisms for excitation transfer do not play a significant role in these materials. 相似文献
8.
The effect of bacterial and fungal activities on organic matter degradation in Brazilian soils was studied by a microcalorimetric method. Bacteria and fungi isolated from tropical soils and added to: Rhodic eutrudox (R), Typic eutrudox (V) and Quartzipsamment (Q) soils amended separately with moisture (control) (A) and 25% of cattle manure (E), municipal refuse compost (L), earthworm casts (H) or 23 μg of trifluralin (T) were investigated. The number of colony forming units in soil suspension was quantified by microscopy and inoculated in respective soil. All processes were measured at intervals of 7 days over a period of 35 days. The exothermic thermal effect (μJ) per cm3 of bacteria or fungi per gram of dry soil, respectively, for each substrate was: [(9±1), (4±1)] RA; [(478±24), (105±5)] RE; [(121±6), (71±4)] RL; [(121±6), (71±4)] RH; [(8±1); (3±1)] RT; [(10±1), (9±1] VA; [(347±17), (261±13)] VE; [(71±4), (28±1)] VL; [(22±1), (33±2)] VH; [(7±1), (10±1)] VT; [(19±1), (12±1)] QA; [(1301±65), (46±2)] QE; [(89±4), (9±1)] QL; [(130±7), (11±1)] QH; [(32±2), (8±1)] QT. The calorimetric values are higher for bacteria than for fungi. In general, the results showed higher activities in the soil amended with cattle manure than with other additives. 相似文献
9.
10.
We present a new approach to the a posteriori error analysis of stable Galerkin approximations of reaction–convection–diffusion problems. It relies upon a non-standard variational formulation of the exact problem, based on the anisotropic wavelet decomposition of the equation residual into convection-dominated scales and diffusion-dominated scales. The associated norm, which is stronger than the standard energy norm, provides a robust (i.e., uniform in the convection limit) control over the streamline derivative of the solution. We propose an upper estimator and a lower estimator of the error, in this norm, between the exact solution and any finite dimensional approximation of it. We investigate the behaviour of such estimators, both theoretically and through numerical experiments. As an output of our analysis, we find that the lower estimator is quantitatively accurate and robust. 相似文献