全文获取类型
收费全文 | 2029篇 |
免费 | 155篇 |
国内免费 | 108篇 |
专业分类
化学 | 1158篇 |
晶体学 | 26篇 |
力学 | 79篇 |
综合类 | 8篇 |
数学 | 567篇 |
物理学 | 454篇 |
出版年
2023年 | 28篇 |
2022年 | 58篇 |
2021年 | 69篇 |
2020年 | 75篇 |
2019年 | 74篇 |
2018年 | 80篇 |
2017年 | 75篇 |
2016年 | 104篇 |
2015年 | 84篇 |
2014年 | 98篇 |
2013年 | 132篇 |
2012年 | 118篇 |
2011年 | 150篇 |
2010年 | 102篇 |
2009年 | 85篇 |
2008年 | 98篇 |
2007年 | 86篇 |
2006年 | 81篇 |
2005年 | 81篇 |
2004年 | 53篇 |
2003年 | 40篇 |
2002年 | 43篇 |
2001年 | 26篇 |
2000年 | 33篇 |
1999年 | 24篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 37篇 |
1995年 | 34篇 |
1994年 | 22篇 |
1993年 | 20篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 16篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 6篇 |
排序方式: 共有2292条查询结果,搜索用时 31 毫秒
71.
72.
Truemper configurations (thetas, pyramids, prisms, and wheels) have played an important role in the study of complex hereditary graph classes (eg, the class of perfect graphs and the class of even-hole-free graphs), appearing both as excluded configurations, and as configurations around which graphs can be decomposed. In this paper, we study the structure of graphs that contain (as induced subgraphs) no Truemper configurations other than (possibly) universal wheels and twin wheels. We also study several subclasses of this class. We use our structural results to analyze the complexity of the recognition, maximum weight clique, maximum weight stable set, and optimal vertex coloring problems for these classes. Furthermore, we obtain polynomial -bounding functions for these classes. 相似文献
73.
A milestone in probability theory is the law of the iterated logarithm (LIL), proved by Khinchin and independently by Kolmogorov in the 1920s, which asserts that for iid random variables with mean 0 and variance 1 In this paper we prove that LIL holds for various functionals of random graphs and hypergraphs models. We first prove LIL for the number of copies of a fixed subgraph H. Two harder results concern the number of global objects: perfect matchings and Hamiltonian cycles. The main new ingredient in these results is a large deviation bound, which may be of independent interest. For random k‐uniform hypergraphs, we obtain the Central Limit Theorem and LIL for the number of Hamilton cycles. 相似文献
74.
Tang Guangxian Shafee Ahmad Nam Nguyen Dang Tlili Iskander 《Journal of Thermal Analysis and Calorimetry》2021,143(6):4249-4260
Journal of Thermal Analysis and Calorimetry - Electrical sensor has been considered in the current attempt. Combination of buoyancy, electric and radiative forces has been included in the governing... 相似文献
75.
This paper is devoted to the quasilinear equation ■where p 2,Ω is a(bounded or unbounded) domain of R~N,w_1,w_2 are nonnegative continuous functions and f is an increasing function. We establish a Liouville type theorem for nontrivial stable solutions of the equation under some mild assumptions on Ω,w_1, w_2 and f, which extends and unifies several results on this topic. 相似文献
76.
Pham Duy Khanh Tran Hong Mo Trinh T. T. Tran 《Numerical Functional Analysis & Optimization》2019,40(8):924-943
Necessary and sufficient conditions for qualitative properties of infinite dimensional linear programing problems such as solvability, duality, and complementary slackness conditions are studied in this article. As illustrations for the results, we investigate the parametric version of Gale’s example. 相似文献
77.
78.
Bui Dac Dung Trinh Van Giap Tibor Kovacs Tran Ngoc Toan Le Dinh Cuong Tran Khanh Minh Nguyen Huu Quyet Nguyen Van Khanh 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1943-1948
Mineral sands are mined in several countries to supply to the titanium and zircon producing industries. Coastal black mineral sands usually contain, besides ilmenite (FeTiO3) and rutile (TiO2), radioactive minerals such as zircon (ZrSiO4) and monazite (RePO4). Radon and thoron activity concentration originated from natural radioactive contents of the black mineral sand was monitored at the extraction and processing for black minerals in the coastal areas of Ha Tinh Province, one of the around 40 coastal mineral sand deposits in Vietnam. The survey was carried out with the Raduet chambers made by Radosys Ltd—Hungary. The obtained results for 25 investigated points show that the measured values are not high in the residential houses and in case of the sand extraction site as well. At the titanium processing plant the measured values were higher than outside the facility (Radon: 18–55 Bq/m3 with average of 34 Bq/3 and Thoron 33–118 Bq/m3 with average of 58 Bq/m3) but still comparable to the average concentration of the world published by UNSCEAR. The typical outdoor levels of radon and thoron gas are each of the order of 10 Bq/m3. Although the radon concentrations were low in the zircon and titanium processing plants, the thoron concentrations in the houses for separating rutile and zircon were very high. At zircon processing factory, the thoron concentration could reach 2,931 Bq/m3 and the estimated annual effective dose would be 21.4 mSv/a. Intervention has to be taken in order to reduce the thoron level in this factory since the level of thoron and its progenies corresponding to an annual occupational effective dose is beyond the action level of 6 mSv/a. 相似文献
79.
Data on the methods of stabilization and modification of nanosize particles used in the technology of development of new polymer-inorganic nanocomposites were analyzed and generalized. Advantages of the chemical method using silane-based surface-binding modifiers were discussed. The use of surface-initiated graft polymerization was shown to be promising for the solution of problems of deagglomeration, stabilization, and efficient homogenization of nanosize particles. 相似文献
80.
Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating. 相似文献