全文获取类型
收费全文 | 2388篇 |
免费 | 75篇 |
国内免费 | 24篇 |
专业分类
化学 | 1610篇 |
晶体学 | 9篇 |
力学 | 53篇 |
数学 | 464篇 |
物理学 | 351篇 |
出版年
2023年 | 20篇 |
2022年 | 67篇 |
2021年 | 61篇 |
2020年 | 57篇 |
2019年 | 51篇 |
2018年 | 57篇 |
2017年 | 52篇 |
2016年 | 92篇 |
2015年 | 58篇 |
2014年 | 89篇 |
2013年 | 178篇 |
2012年 | 161篇 |
2011年 | 189篇 |
2010年 | 135篇 |
2009年 | 102篇 |
2008年 | 141篇 |
2007年 | 146篇 |
2006年 | 134篇 |
2005年 | 116篇 |
2004年 | 85篇 |
2003年 | 68篇 |
2002年 | 63篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 12篇 |
1998年 | 20篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有2487条查询结果,搜索用时 0 毫秒
41.
da Silva Pedro Rafael Sena Laís Cristina Santana Silva Rubens Pedro Lorena de Santana Danielle Cristine Almeida Silva de Santana Fernando José Malagueño 《Analytical and bioanalytical chemistry》2019,411(16):3447-3461
Analytical and Bioanalytical Chemistry - This study aimed to determine simultaneously five major street cocaine adulterants (caffeine, lidocaine, phenacetin, diltiazem, and hydroxyzine) in human... 相似文献
42.
Nonlinear Dynamics - Introduction of stiffness nonlinearities to broaden the frequency bandwidth of vibratory energy harvesters has the adverse influence of complicating the response behavior of... 相似文献
43.
Guimaraes Giulia A. A. Lacerda Janiny N. Xing Yutao Ponzio Eduardo A. Pacheco Wagner F. Semaan Felipe S. Dornellas Rafael M. 《Journal of Solid State Electrochemistry》2020,24(8):1769-1779
Journal of Solid State Electrochemistry - This work presents the development and characterization of an electrochemical sensor of tin hexacyanoferrate (SnHCF), produced from the modification by... 相似文献
44.
Background
Marlin-1 is a microtubule binding protein that associates specifically with the GABAB1 subunit in neurons and with members of the Janus kinase family in lymphoid cells. In addition, it binds the molecular motor kinesin-I and nucleic acids, preferentially single stranded RNA. Marlin-1 is expressed mainly in the central nervous system but little is known regarding its cellular and subcellular distribution in the brain. 相似文献45.
Lucas C. Céleri Rafael M. Gomes Radu Ionicioiu Thomas Jennewein Robert B. Mann Daniel R. Terno 《Foundations of Physics》2014,44(5):576-587
We describe a new class of experiments designed to probe the foundations of quantum mechanics. Using quantum controlling devices, we show how to attain a freedom in temporal ordering of the control and detection of various phenomena. We consider wave–particle duality in the context of quantum-controlled and the entanglement-assisted delayed-choice experiments. Then we discuss a quantum-controlled CHSH experiment and measurement of photon’s transversal position and momentum in a single set-up. 相似文献
46.
Rafael Espínola Adrian Petru?el 《Journal of Mathematical Analysis and Applications》2005,309(2):420-432
The purpose of this note is to present some fixed point and data dependence theorems in complete gauge spaces and in hyperconvex metric spaces for the so-called Meir-Keeler multivalued operators and admissible multivalued aα-contractions. Our results extend and generalize several theorems of Espínola and Kirk [R. Espínola, W.A. Kirk, Set-valued contractions and fixed points, Nonlinear Anal. 54 (2003) 485-494] and Rus, Petru?el, and Sînt?m?rian [I.A. Rus, A. Petru?el, A. Sînt?m?rian, Data dependence of the fixed point set of some multivalued weakly Picard operators, Nonlinear Anal. 52 (2003) 1947-1959]. 相似文献
47.
Rafael Ferragut 《Physica B: Condensed Matter》2012,407(14):2676-2683
A positron annihilation spectroscopy analysis method to obtain a quantitative determination of the chemical composition around defects inside nanoparticles is presented here. This methodology is applied to AlCuMg alloys to study the rapid hardening phenomena associated with solute-vacancy aggregation. Coincidence Doppler Broadening (CDB) and lifetime spectroscopy measurements of reference samples of pure elements with and without defects were analyzed to give quantitative information of the average chemical environment around vacancies, i.e. the atomic fraction of the first neighbors of these defects, in the alloys studied. The accuracy and reproducibility of the methodology is confirmed not only by good fits to the experimental data but, in most cases, by the consistency between the mean lifetime values predicted, using the CDB estimation, and the mean lifetime values independently measured. Discrepancies in the methodology are expected when there is poor CDB contrast between elements, i.e. having similar electronic structure (for example, Al and Mg). The criterion for establishing the statistical accuracy of the separation of elements in these special cases is discussed. The methodology can be applied not only to study homogeneous materials as metallic alloys, but also to study the depth profile in thin films. 相似文献
48.
Anna Martínez-Gavara Vicente Campos Manuel Laguna Rafael Martí 《Journal of Global Optimization》2017,67(3):671-686
The Maximum Minsum Dispersion Problem (Max-Minsum DP) is a strongly NP-Hard problem that belongs to the family of equitable dispersion problems. When dealing with dispersion, the operations research literature has focused on optimizing efficiency-based objectives while neglecting, for the most part, measures of equity. The most common efficiency-based functions are the sum of the inter-element distances or the minimum inter-element distance. Equitable dispersion problems, on the other hand, attempt to address the balance between efficiency and equity when selecting a subset of elements from a larger set. The objective of the Max-Minsum DP is to maximize the minimum aggregate dispersion among the chosen elements. We develop tabu search and GRASP solution procedures for this problem and compare them against the best in the literature. We also apply LocalSolver, a commercially available black-box optimizer, to compare our results. Our computational experiments show that we are able to establish new benchmarks in the solution of the Max-Minsum DP. 相似文献
49.
50.
Laís Peres Silva Ivanilson Pimenta Santos Dahara Keyse Carvalho Silva Bruna Padilha Zurita Claro dos Reis Cssio Santana Meira Marcos Venícius Batista de Souza Castro Jos Maurício dos Santos Filho Joo Honorato de Araujo-Neto Javier Alcides Ellena Rafael Gomes da Silveira Milena Botelho Pereira Soares 《Molecules (Basel, Switzerland)》2022,27(23)
Immunomodulatory agents are widely used for the treatment of immune-mediated diseases, but the range of side effects of the available drugs makes necessary the search for new immunomodulatory drugs. Here, we investigated the immunomodulatory activity of new ferrocenyl-N-acyl hydrazones derivatives (SintMed(141–156). The evaluated N-acyl hydrazones did not show cytotoxicity at the tested concentrations, presenting CC50 values greater than 50 µM. In addition, all ferrocenyl-N-acyl hydrazones modulated nitrite production in immortalized macrophages, showing inhibition values between 14.4% and 74.2%. By presenting a better activity profile, the ferrocenyl-N-acyl hydrazones SintMed149 and SintMed150 also had their cytotoxicity and anti-inflammatory effect evaluated in cultures of peritoneal macrophages. The molecules were not cytotoxic at any of the concentrations tested in peritoneal macrophages and were able to significantly reduce (p < 0.05) the production of nitrite, TNF-α, and IL-1β. Interestingly, both molecules significantly reduced the production of IL-2 and IFN-γ in cultured splenocytes activated with concanavalin A. Moreover, SintMed150 did not show signs of acute toxicity in animals treated with 50 or 100 mg/kg. Finally, we observed that ferrocenyl-N-acyl hydrazone SintMed150 at 100 mg/kg reduced the migration of neutrophils (44.6%) in an acute peritonitis model and increased animal survival by 20% in an LPS-induced endotoxic shock model. These findings suggest that such compounds have therapeutic potential to be used to treat diseases of inflammatory origin. 相似文献