全文获取类型
收费全文 | 1216篇 |
免费 | 36篇 |
国内免费 | 2篇 |
专业分类
化学 | 866篇 |
晶体学 | 16篇 |
力学 | 32篇 |
数学 | 55篇 |
物理学 | 285篇 |
出版年
2024年 | 7篇 |
2023年 | 9篇 |
2022年 | 29篇 |
2021年 | 22篇 |
2020年 | 22篇 |
2019年 | 35篇 |
2018年 | 28篇 |
2017年 | 39篇 |
2016年 | 52篇 |
2015年 | 28篇 |
2014年 | 45篇 |
2013年 | 109篇 |
2012年 | 63篇 |
2011年 | 71篇 |
2010年 | 48篇 |
2009年 | 51篇 |
2008年 | 58篇 |
2007年 | 48篇 |
2006年 | 47篇 |
2005年 | 45篇 |
2004年 | 37篇 |
2003年 | 20篇 |
2002年 | 30篇 |
2001年 | 19篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1991年 | 6篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 9篇 |
排序方式: 共有1254条查询结果,搜索用时 0 毫秒
21.
Experiments with heavy ions at moderate energies show the importance of deformation in heavy ion collisions. A deformation
model which takes deformation dynamically into account is developed. Having described fusion and deep inelastic collision
for a very heavy system (Xe + Bi) and a medium heavy system (Ar + Th) at various energies successfully, we turn to some comparatively
lighter heavy ions where fusion is the most dominant feature. Fusion cross-sections for six pairs of lighter systems (35Cl +116Sn,58Ni+62Ni,35Cl+62Ni,32S+24Mg,24Mg+24Mg and12C+27Al) have been obtained using our deformation model which agree well with experiment. The two-slope-behaviour of fusion excitation
function which is an important feature of light ion fusion systematics is also obtained, in our model calculations for all
the systems studied. 相似文献
22.
Satish Shirali 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1977,28(1):141-149
Summary We consider the equation u+ expu=0, >0,u(boundary)0 in the formv= exp (K,v), whereK
–1=–. We give bounds on for the latter equation to be solvable by the contraction mapping principle, and estimate theL
2 norm of the solution so obtained. We also give a bound on for the topological index of the solution to be non-zero and apply Krasnoselskii's results to the least squares method of approximating the solution.
Sommario Consideriamo l'equazione u+ expu=0, >0,u(frontiera)=0 nella formav= exp (Kv), doveK –1=–. In questo lavoro diamo limitazioni per per cui la seconda equazione e risolubile col metodo delle contrazioni, e diamo una stima della norma inL 2 della soluzione cosi ottenuta. Diamo anche una limitazione per per cui l'indice topologico della soluzione diventa non zero, e applichiamo i risultati di Krasnoselskii al metodo dei minimi quadrati per approssimare la soluzione.相似文献
23.
Ketones are converted smoothly into the corresponding acyloin with a high degree of selectivity upon treatment with iodosobenzene or phenyliodosodiacetate in methanolic sodium hydroxide. 相似文献
24.
A novel fluoranthene based fluorescent chemosensor for the detection of picric acid (PA) at the parts per billion (ppb) level was evaluated. Static fluorescence quenching was the dominant process by intercalative π-π interaction between fluoranthene (S(1)) and nitroaromatics. 相似文献
25.
Guy Mann Gandhesiri Satish Roman Meledin Ganga B. Vamisetti Ashraf Brik 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(38):13674-13683
Chemical protein synthesis and biorthogonal modification chemistries allow production of unique proteins for a range of biological studies. Bond‐forming reactions for site‐selective protein labeling are commonly used in these endeavors. Selective bond‐cleavage reactions, however, are much less explored and still pose a great challenge. In addition, most of studies with modified proteins prepared by either total synthesis or semisynthesis have been applied mainly for in vitro experiments with very limited extension to live cells. Reported here is an approach for studying uniquely modified proteins containing a traceless cell delivery unit and palladium‐based cleavable element for chemical activation, and monitoring the effect of these proteins in live cells. This approach is demonstrated for the synthesis of a caged ubiquitin‐aldehyde, which was decaged for the inhibition of deubiquitinases in live cells. 相似文献
26.
Incoherent scattering functions S(x, Z) for six rare earth elements were evaluated from accurately measured whole atom differential incoherent scattering cross sections for 59.54 keV γ-rays scattered at 30°, 45°, 60° and 90° scattering angles corresponding to 1.24, 1.84, 2.40 and 3.39 Å−1 photon momentum transfers. Our results for S(x, Z) are the first for these rare earth elements. 相似文献
27.
Satish N. DigheHemant R. Jadhav 《Tetrahedron letters》2012,53(43):5803-5806
Microwave assisted simple, rapid, solventless, and catalyst-free chemoselective method for the protection of amino group in aromatic, aliphatic, heterocyclic, aralkyl amines, phenyl hydrazine, and amino acid esters in good to excellent isolated yield (83-98%) in short reaction time (2-12 min) has been reported. 相似文献
28.
The inclusion complexes of a series of 4-arylidenamino-5-phenyl-4H-1, 2, 4-triazole-3-thiols have been prepared with β-cyclodextrin. The compounds and their inclusion complexes have been characterized by studying their physical and spectral properties. The thermodynamic stability constant and free energy of activation have been determined to know the stability of inclusion complexes and type of host-guest relation. Finally, absorption, excitation and emission spectra of the compounds (4-arylidenamino-5-phenyl-4H-1, 2, 4-triazole-3-thiols) and their inclusion complexes have been taken. It is found that inclusion complex formation brings about a drastic change in absorption and fluorescence characteristic (both excitation and emission spectra) of newly synthesized compounds. 相似文献
29.
Gouranga C. Nayak 《Annals of Physics》2010,325(2):514-3898
Factorization theorem plays the central role at high energy colliders to study standard model and beyond standard model physics. The proof of factorization theorem is given by Collins, Soper and Sterman to all orders in perturbation theory by using diagrammatic approach. One might wonder if one can obtain the proof of factorization theorem through symmetry considerations at the lagrangian level. In this paper we provide such a proof. 相似文献
30.
Vikas Jain A.K. Nayak P.K. Vijayan D. Saha R.K. Sinha 《Experimental Thermal and Fluid Science》2010,34(6):776-787
Natural circulation as a mode of heat removal is being considered as a prominent passive feature in the innovative nuclear reactor designs, particularly in boiling-water-reactors, due to its simplicity and economy. However, boiling natural circulation system poses many challenges to designer due to occurrence of various kinds of instabilities such as excursive instability, density wave oscillations, flow pattern transition instability, geysering and metastable states in parallel channels. This problem assumes greater significance particularly at low-pressures i.e. during startup, where there is great difference in the properties of two phases. In light of this, a parallel channel loop has been designed and installed that has a geometrical resemblance to the pressure-tube-type boiling-water-reactor, to investigate into the behavior of boiling natural circulation. The loop comprises of four identical parallel channels connected between two common plenums i.e. steam drum and header. The recirculation path is provided by a single downcomer connected between steam drum and header. Experiments have been conducted over a wide range of power and pressures (1–10 bar). Two distinct unstable zones are observed with respect to power i.e. corresponding to low power (Type-I) and high power (Type-II) with a stable zone at intermediate powers. The nature of oscillations in terms of their amplitude and frequency and their evolution for Type-I and Type-II instabilities are studied with respect to the effect of heater power and pressure. This paper discusses the evolution of unstable and stable behavior along with the nature of flow oscillation in the channels and the effect of pressure on it. 相似文献