全文获取类型
收费全文 | 1614篇 |
免费 | 52篇 |
国内免费 | 13篇 |
专业分类
化学 | 1135篇 |
晶体学 | 14篇 |
力学 | 28篇 |
数学 | 92篇 |
物理学 | 291篇 |
无线电 | 119篇 |
出版年
2022年 | 9篇 |
2021年 | 19篇 |
2020年 | 12篇 |
2019年 | 28篇 |
2018年 | 22篇 |
2017年 | 8篇 |
2016年 | 27篇 |
2015年 | 29篇 |
2014年 | 37篇 |
2013年 | 68篇 |
2012年 | 71篇 |
2011年 | 78篇 |
2010年 | 50篇 |
2009年 | 46篇 |
2008年 | 77篇 |
2007年 | 85篇 |
2006年 | 78篇 |
2005年 | 90篇 |
2004年 | 86篇 |
2003年 | 66篇 |
2002年 | 72篇 |
2001年 | 42篇 |
2000年 | 34篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 27篇 |
1996年 | 34篇 |
1995年 | 17篇 |
1994年 | 24篇 |
1993年 | 22篇 |
1992年 | 29篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 23篇 |
1987年 | 14篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 22篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1976年 | 13篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1965年 | 8篇 |
排序方式: 共有1679条查询结果,搜索用时 744 毫秒
161.
162.
John A. Ford Yasushi Narushima Hiroshi Yabe 《Computational Optimization and Applications》2008,40(2):191-216
Conjugate gradient methods are appealing for large scale nonlinear optimization problems, because they avoid the storage of
matrices. Recently, seeking fast convergence of these methods, Dai and Liao (Appl. Math. Optim. 43:87–101, 2001) proposed a conjugate gradient method based on the secant condition of quasi-Newton methods, and later Yabe and Takano (Comput.
Optim. Appl. 28:203–225, 2004) proposed another conjugate gradient method based on the modified secant condition. In this paper, we make use of a multi-step
secant condition given by Ford and Moghrabi (Optim. Methods Softw. 2:357–370, 1993; J. Comput. Appl. Math. 50:305–323, 1994) and propose two new conjugate gradient methods based on this condition. The methods are shown to be globally convergent
under certain assumptions. Numerical results are reported. 相似文献
163.
Low-velocity pneumatic conveying in horizontal pipe for coarse particles and fine powders 总被引:3,自引:0,他引:3
First,the characteristics of low-velocity conveying of particles having different hardness are experimentally investigated in a horizontal pipeline in terms of flow pattern and pressure drop to show that the slug flow can be classified into two types depending on the settling of particles along the pipeline,and the period is small for slug flow without the settled layer,which is called solitary slug flow.The pressure drop for soft particles is shown to be larger than that for hard particles.Then,experimental results are presented on horizontal fluidized-bed conveying of fine powders to show that air release from the top surface of the conveying channel is an important factor for high mass flow rate of particles. 相似文献
164.
165.
This paper describes an efficient contention resolution algorithm and its distributed implementation for large capacity input queuing cross-connect switches, which will establish virtual paths in future broadband ATM networks. The algorithm dynamically allocates sending time to cells held in input queues when no contention is indicated in the designated output ports. An expression for the mean delay and the cell loss probability for random traffic are derived through an approximate analysis. Input cells are served on a first-come, first-served basis as conventional contention resolution algorithms whose throughput saturates at 58 per cent because of head of line blocking in input queues. The proposed algorithm achieves a maximum throughput of 76 per cent. 相似文献
166.
M. Okumura L. Tong Kaoru Fujinaga Yasushi Seike 《Analytical and bioanalytical chemistry》2001,370(1):104-107
A simple and rapid in situ preconcentration method for the determination of phosphate in environmental waters has been developed for field analysis. This method is based on solid-phase extraction on a zirconium-loaded Sep-Pack Accell CM cartridge (Zr-SP) and is applicable to studies in which sampling is performed by use of a graduated syringe to prevent contamination and to ensure easy operation at sampling sites. The Zr-SP cartridge was prepared by passing 0.1 mol L–1 zirconium solution through a Sep-Pak Accell CM cartridge, packed with cation exchange sorbent based on a silica matrix. The adsorption of phosphate and its desorption depend only on the pH of the solution. A water sample containing phosphate was adjusted to pH 2 and passed through the Zr-SP cartridge to collect it. The retained phosphate was quantitatively eluted with 0.5 mol L–1 sodium hydroxide solution. The phosphate retained in the Zr-SP cartridge was stable for at least one month. The established preconcentration method was successfully applied to brackish lake waters to investigate seasonal changes in the distribution and behavior of phosphate in a brackish lake. 相似文献
167.
168.
Atsushi Taguchi Shintaro Fujii Taro Ichimura Prabhat Verma Yasushi Inouye Satoshi Kawata 《Chemical physics letters》2008,462(1-3):92-95
We have found that the shape of silver nanocrystals is conveniently controlled by injection of oxygen gas during the polyol reduction of silver ions. The presence of oxygen effectively promotes the oxidative etching of multiple twined particles. Adjusting the flow rate of the oxygen gas yields uniformly-sized silver nanocubes, right bipyramids, nanowires, and spherical nanoparticles depending on the injection rate of the oxygen gas. Electron diffraction and high resolution TEM observations of the synthesized nanocrystals show our nanocrystals do consist of silver, not of silver oxide. SERS activities of the synthesized nanocrystals were also examined. 相似文献
169.
Takashi Fukasawa Takao Orii Masayo Tanaka Noriko Suzuki Yasushi Kanzaki 《Chemical & pharmaceutical bulletin》2008,56(8):1177-1180
There are many reports that the drug-induced taste disorder is ascribable to the chelate reaction of a drug with zinc ion and the following zinc deficiency. As a quantitative measure of the chelating ability of drugs with zinc ions, the chelating ability was estimated from the electrode potential change of the Zn2+/Zn(Hg) system during the addition of a drug. The electrode potential was measured in a water-N,N-dimethylformamide mixed solution and in an aqueous solution depending on the solubility of the drugs. The observed electrode potential change showed a positive correlation to the frequency of the drug-induced taste disorder that was supplied from the manufacturer of the original drug. The regression analysis was carried out assuming that the frequency of the taste disorder and the electrode potential change was linear. The F-values, p-values, and R2-values were 4.29, 0.13, 0.589, and 4.15, 0.13, 0.580, respectively. The positive correlation between the drug-induced taste disorder and the electrode potential change appeared evident if the uncertainty in the frequency of the taste disorder was taken into consideration. Thus the assumption of the zinc ion chelating mechanism on the drug-induced disorder was also evident except for cisplatin. The frequency of the drug-induced taste disorder of bezafibrate was estimated to be 0.4--0.5 from the regression analysis. 相似文献
170.
Koshi Imami Naoyuki Sugiyama Yutaka Kyono Masaru Tomita Yasushi Ishihama 《Analytical sciences》2008,24(1):161-166
We have developed an on-line automated system for phosphoproteome analysis using titania-based phosphopeptide enrichment followed by nanoLC-MS/MS. Titania beads were prepared by calcination of commercial chromatographic titania beads at 800 degrees C to convert the crystalline structure. The obtained rutile-form titania exhibited higher selectivity in phosphopeptide enrichment than commercial titania, even in the absence of a competitive chelating reagent for non-phosphopeptides. For phosphoproteome analysis of human cervical cancer HeLa cells, tryptic digests of the cell extracts were directly injected into this on-line system, and 696 non-redundant phosphopeptides with 671 unambiguously determined phosphorylation sites, derived from 512 phosphoproteins, were successfully identified. This is the first successful application of an on-line automated phosphoproteome analysis system to complex biological samples. 相似文献