全文获取类型
收费全文 | 7508篇 |
免费 | 345篇 |
国内免费 | 19篇 |
专业分类
化学 | 3828篇 |
晶体学 | 73篇 |
力学 | 204篇 |
数学 | 571篇 |
物理学 | 1183篇 |
无线电 | 2013篇 |
出版年
2024年 | 11篇 |
2023年 | 98篇 |
2022年 | 133篇 |
2021年 | 203篇 |
2020年 | 182篇 |
2019年 | 163篇 |
2018年 | 160篇 |
2017年 | 149篇 |
2016年 | 253篇 |
2015年 | 210篇 |
2014年 | 289篇 |
2013年 | 460篇 |
2012年 | 524篇 |
2011年 | 526篇 |
2010年 | 353篇 |
2009年 | 373篇 |
2008年 | 502篇 |
2007年 | 467篇 |
2006年 | 427篇 |
2005年 | 373篇 |
2004年 | 347篇 |
2003年 | 249篇 |
2002年 | 269篇 |
2001年 | 165篇 |
2000年 | 161篇 |
1999年 | 95篇 |
1998年 | 83篇 |
1997年 | 61篇 |
1996年 | 61篇 |
1995年 | 54篇 |
1994年 | 49篇 |
1993年 | 55篇 |
1992年 | 30篇 |
1991年 | 31篇 |
1990年 | 32篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 19篇 |
1983年 | 17篇 |
1981年 | 10篇 |
1980年 | 22篇 |
1979年 | 16篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1972年 | 9篇 |
排序方式: 共有7872条查询结果,搜索用时 0 毫秒
71.
We consider an integrated problem of plant location and capacity planning for components procurement in knockdown production systems. The problem is that of determining the schedule of opening components manufacturing plants, plans for acquisition of capacities in opened components manufacturing plants, and plans for components procurement in final assembly plants with the objective of minimizing the sum of fixed costs for opening plants, acquisition and operation costs of facilities, and delivery and subcontracting costs of components. The problem is formulated as a mixed integer linear program and solved by a two-stage solution procedure. In the solution procedure, the problem is decomposed into two tractable subproblems and these subproblems are solved sequentially. In the first stage, a dynamic plant location problem is solved using a cut and branch algorithm based on Gomory cuts, while a multiperiod capacity planning problem is solved in the second stage by a heuristic algorithm that uses a cut and branch algorithm and a variable reduction scheme. The solution procedure is tested on problems of a practical size and results show that the procedure gives reasonably good solutions. 相似文献
72.
Chang Sung Lim 《Journal of luminescence》2012,132(7):1774-1780
MMoO4 (M=Ca, Ba) particles were synthesized by a metathetic reaction in ethylene glycol assisted by cyclic microwave irradiation followed by further heat-treatment. The MMoO4 (M=Ca, Ba) particles were well crystallized after heat-treatment at 400–600 °C for 3 h. The microstructures exhibited fine morphologies with sizes of 0.5–1 μm and 1.5–2 μm for the CaMoO4 and BaMoO4 particles, respectively. The synthesized MMoO4 (M=Ca, Ba) particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The optical properties were examined by photoluminescence emission and Raman spectroscopy. 相似文献
73.
The carbamoylphosphosphonate silane (CMPO analogue; 2-(diphenylphosphoryl)-N-(3-(triethoxysilyl)propyl) acetamide) modified mesoporous silica was prepared via a post-synthesis grafting method for the effective purification of rare earth elements. The guest CMPO analogue was synthesized by direct coupling reaction of 2-(diphenylphosphoryl) acetic acid and 3-(triethoxysilyl)propan-1-amine. Various mesoporous silicates such as MCM-41, SBA-15, or amorphous silica nanoparticles were adopted as host materials. The resulting surface-modified mesoporous materials were characterized with respect to their structural integrity, surface area, and pore size and the concentration of the CMPO silane species. These CMPO functionalized periodic mesostructured silicates offer the potential of applications as catalysts, sensors, or environmental sorbents. 相似文献
74.
Wireless Personal Communications - This paper presents an error detection algorithm for Lempel-Ziv-78 (LZ78) compressed data. LZ78 data compression involves dictionary coding and aims to compress... 相似文献
75.
Hahn Changhee Shin Hyung June Kwon Hyunsoo Hur Junbeom 《Wireless Personal Communications》2019,107(3):1337-1353
Wireless Personal Communications - In cloud-assisted data outsourcing systems, the privacy of sensitive data is a major concern. Thus, data are uploaded in encrypted form in many cloud applications... 相似文献
76.
Chromatographia - Optimal derivatization conditions were established for the simultaneous determination of 12 aliphatic saturated aldehydes, 8 aliphatic saturated ketones, 4 cyclic ketones, 3... 相似文献
77.
Kyeongnan Kwon 《Journal of Dispersion Science and Technology》2016,37(10):1518-1525
Glucose-responsive monoolein (MO) cubic phase was prepared by immobilizing proteinoid composed of Asp and Leu (PAL) and hydrophobically modified glucose oxidase (HmGOD) onto the MO bilayers. The hydrodynamic mean diameter of PAL aggregate in aqueous solution decreased with increasing the pH value. The number of pamitic acid residue per one molecule of HmGOD was determined to be 6.3 by a calorimetric method. HmGOD could acidify glucose solution in a few hours, possibly because it converted glucose to gluconic acid. PAL- and HmGOD-immobilized MO cubic phase was prepared by hydrating MO melt with the mixture aqueous solution of PAL and HmGOD. The cubic phase exhibited its phase transition around 62.5°C, determined by polarizing microscopy. The release of carboxylic fluorescein (CF) from the cubic phase was suppressed when the pH value of release medium decreased, possibly because PAL can aggregate more at a lower pH value. The release was suppressed when glucose concentration increased, possibly because the release medium can be more acidified and PAL will be more aggregated at a higher glucose concentration. The cubic phase could be used as a drug carrier which releases its content in a sustained manner when the glucose concentration is abnormally high. 相似文献
78.
Many different types of urine proteome studies have been done, but urine glycoprotein studies are insufficient. Therefore, we studied the glycoproteins from rat urine, which could be used to identify biomarkers in an animal model. First, urinary proteins were prepared by using the dialysis and lyophilizing methods from rat urine. Glycoproteins enriched with lectin affinity purification, concanavalin A, jacalin and wheat germ agglutinin from the urinary proteins were separated by means of reverse-phase fast protein LC (FPLC) or 1-D PAGE. Each FPLC fraction and 1-D PAGE gel band were trypsin-digested and analyzed by means of nanoLC-MS/MS. LC-MS/MS analyses were carried out by using linear ion trap MS. A total of 318 rat urinary glycoproteins were identified from the FPLC fractions and gel bands; approximately 90% of identified proteins were confirmed as glycoproteins in Swiss-Prot. Many glycoproteins, known as biomarkers, including C-reactive protein, uromodulin, amyloid beta A4 protein, alpha-1-inhibitor 3, vitamin D-binding protein, kallikrein 3 and fetuin-A were identified in this study. By studying urinary glycoproteins collected from rat, these results may help to assist in identifying urinary biomarkers regarding various types of disease models. 相似文献
79.
Yong‐beom Lim Dr. Myongsoo Lee Prof. 《Angewandte Chemie (International ed. in English)》2009,48(19):3394-3396
Available in small print : Block copolymer lithography has great potential for reducing the size and fabrication time of integrated circuits. Hydrogen‐bonding‐mediated molecular recognition in self‐assembly processes can be used to produce highly ordered square arrays of block copolymers on the surface of a silicon substrate (see picture).
80.
A. V. M. Chandramalar Y. Y. Lim Y. K. Leong 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,160(3):49-205
The effects of cis- and trans-1,2-, trans-1,4-cyclohexanedicarboxylic acid, 95% cis-1,3,5-cyclohexane tricarboxylic acid and cis-1,2,3,4,5,6-cyclohexanehexacarboxylic acid on the yield stress–pH behaviour of concentrated ZrO2 dispersions are reported. Adsorbed cis-1,2,3,4,5,6-cyclohexanehexacarboxylic acid imparts predominantly steric interactions. It forms a steric barrier keeping the interacting particles apart. Adsorbed cis- and trans-1,2 increase the maximum yield stress and this was attributed to a hydrophobic force resulting from the part of the cyclohexane ring sticking out into the solution which is devoid of charged or hydrophilic group. Adsorbed trans-1,4 increases the maximum yield stress by at least threefold and its configuration favours strong bridging interaction with an adjacent particle. Predominantly, cis-1,3,5 also increases the maximum yield stress but only by 60% at the same additive concentration. This was attributed to a smaller degree of bridging. 相似文献