全文获取类型
收费全文 | 7241篇 |
免费 | 390篇 |
国内免费 | 60篇 |
专业分类
化学 | 5427篇 |
晶体学 | 63篇 |
力学 | 132篇 |
数学 | 678篇 |
物理学 | 1391篇 |
出版年
2023年 | 34篇 |
2022年 | 46篇 |
2021年 | 143篇 |
2020年 | 118篇 |
2019年 | 138篇 |
2018年 | 112篇 |
2017年 | 108篇 |
2016年 | 238篇 |
2015年 | 226篇 |
2014年 | 271篇 |
2013年 | 473篇 |
2012年 | 531篇 |
2011年 | 610篇 |
2010年 | 381篇 |
2009年 | 292篇 |
2008年 | 488篇 |
2007年 | 421篇 |
2006年 | 427篇 |
2005年 | 374篇 |
2004年 | 333篇 |
2003年 | 284篇 |
2002年 | 263篇 |
2001年 | 138篇 |
2000年 | 125篇 |
1999年 | 91篇 |
1998年 | 65篇 |
1997年 | 57篇 |
1996年 | 68篇 |
1995年 | 58篇 |
1994年 | 52篇 |
1993年 | 36篇 |
1992年 | 39篇 |
1991年 | 28篇 |
1990年 | 38篇 |
1989年 | 41篇 |
1988年 | 30篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 42篇 |
1984年 | 29篇 |
1983年 | 22篇 |
1982年 | 26篇 |
1981年 | 27篇 |
1980年 | 19篇 |
1979年 | 30篇 |
1978年 | 18篇 |
1977年 | 24篇 |
1976年 | 22篇 |
1975年 | 18篇 |
1973年 | 27篇 |
排序方式: 共有7691条查询结果,搜索用时 15 毫秒
991.
Silicon slab photonic crystal micro cavities designed for of-resonant coupling to nitrogen vacancy (NV) centers were simulated
and fabricated. FDTD-simulations show the partial density of states spectrally near the NV-center electric dipole transition
can be tuned to reduce decoherence of an excited NV-center despite this transition being above the silicon electronic band
gap. The partial density of states at the NV-center transition can be made to dip below half of the free-space partial density
of states without significantly affecting the cavity mode quality factor. These promising results sustain the merits of using
silicon as a base photonic crystal material for quantum information processing even when integrated emitters radiate above
the electronic band gap of silicon. 相似文献
992.
Young Yi Kim 《Applied Surface Science》2010,256(14):4438-4088
Phosphorus (P)-doped ZnO thin films with amphoteric doping behavior were grown on c-sapphire substrates by radio frequency magnetron sputtering with various argon/oxygen gas ratios. Control of the electrical types in the P-doped ZnO films was achieved by varying the gas ratio without post-annealing. The P-doped ZnO films grown at a argon/oxygen ratio of 3/1 showed p-type conductivity with a hole concentration and hole mobility of 1.5 × 1017 cm−3 and 2.5 cm2/V s, respectively. X-ray diffraction showed that the ZnO (0 0 0 2) peak shifted to lower angle due to the positioning of P3− ions with a larger ionic radius in the O2− sites. This indicates that a p-type mechanism was due to the substitutional PO. The low-temperature photoluminescence of the p-type ZnO films showed p-type related neutral acceptor-bound exciton emission. The p-ZnO/n-Si heterojunction light emitting diode showed typical rectification behavior, which confirmed the p-type characteristics of the ZnO films in the as-deposited status, despite the deep-level related electroluminescence emission. 相似文献
993.
We grew heterojunction light emitting diode (LED) structures with various n-type semiconducting layers by magnetron sputtering on p-type GaN at high temperature. Because the undoped ZnO used as an active layer was grown under oxygen rich atmosphere, all LED devices showed the EL characteristics corresponding to orange-red wavelength due to high density of oxygen interstitial, which was coincident with the deep level photoluminescence emission of undoped ZnO. The use of the Ga doped layers as a top layer provided the sufficient electron carriers to active region and resulted in the intense EL emission. The LED sample with small quantity of Mg incorporated in MgZnO as an n-type top layer showed more intense emission than the LED with ZnO, in spite of the deteriorated electrical and structural properties of the MgZnO film. This might be due to the improvement of output extraction efficiency induced by rough surface. 相似文献
994.
Yong Hwan Lim Bum Ho Choi Young Baek Kim Dong Chan Shin 《Applied Surface Science》2010,256(23):6997-7000
We investigated the effects of in situ plasma-treatment on optical and electrical properties of index-matched indium tin oxide (IMITO) thin film. To render the IMITO-coated surface hydrophilic and study the optical and electrical characteristics, we performed in situ oxygen plasma post-treatment without breaking vacuum. The 94.6% transmittance in the visible wavelength range (400-700 nm) increased on average to 96.4% and the maximum transmittance reached 98% over a broad wavelength range. The surface roughness and sheet resistance improved from 0.9 nm and 200 Ω/sq to 0.0905 nm and 100 Ω/sq, respectively, by in situ plasma post-treatment. We confirmed by contact angle measurement that the hydrophobic IMITO surface was altered to hydrophilic. The improved optical and electrical characteristics of in situ plasma-treated IMITO makes it adequate for high-resolution liquid crystal on silicon displays. 相似文献
995.
LeRoy B. Beasley Young Bae Jun Seok-Zun Song 《Czechoslovak Mathematical Journal》2018,68(4):1055-1066
Let ?+ be the semiring of all nonnegative integers and A an m × n matrix over ?+. The rank of A is the smallest k such that A can be factored as an m × k matrix times a k×n matrix. The isolation number of A is the maximum number of nonzero entries in A such that no two are in any row or any column, and no two are in a 2 × 2 submatrix of all nonzero entries. We have that the isolation number of A is a lower bound of the rank of A. For A with isolation number k, we investigate the possible values of the rank of A and the Boolean rank of the support of A. So we obtain that the isolation number and the Boolean rank of the support of a given matrix are the same if and only if the isolation number is 1 or 2 only. We also determine a special type of m×n matrices whose isolation number is m. That is, those matrices are permutationally equivalent to a matrix A whose support contains a submatrix of a sum of the identity matrix and a tournament matrix. 相似文献
996.
Byungchan Kim Ji Young Kim Chong Gyu Lee Poo-Sung Park 《Comptes Rendus Mathematique》2018,356(2):125-128
We prove that the set GP of all nonzero generalized pentagonal numbers is an additive uniqueness set; if a multiplicative function f satisfies the equation for all , then f is the identity function. 相似文献
997.
Strong convergence analysis of a hybrid algorithm for nonlinear operators in a Banach space 下载免费PDF全文
Sun Young Cho 《Journal of Applied Analysis & Computation》2018,8(1):19-31
In this paper, a hybrid algorithm is investigated for an asymptotically quasi-$\phi$-nonexpansive mapping in the intermediate sense and a bifunction. Strong convergence of the algorithm is obtained in a strictly convex, smooth and reflexive Banach space. 相似文献
998.
It is proved that, in Minkowski 3-space, a CSM-helicoidal surface, i.e., a helicoidal surface under cubic screw motion is isometric to a rotation surface so that helices on the helicoidal surface correspond to parallel circles on the rotation surface. By distinguishing a CSM-helicoidal surface as three cases, that is, the case of type I, the case of type II with negative and positive pitch, the relations are discussed between the mean curvatures or Gauss maps of a pair of isometric helicoidal and rotation surface. A CSM-helicoidal surface of Case 1 or 2 and its isometric rotation surface with null axis have same mean curvatures (resp. Gauss maps) if and only if they are minimal. But each pair of isometric CSM-helicoidal surface of Case 3 and rotation surface with spacelike axis have different Gauss maps. 相似文献
999.
Mohsen Jahangirian Tillal Eldabi Aisha Naseer Lampros K. Stergioulas Terry Young 《European Journal of Operational Research》2010
This paper reports the results of a review of simulation applications published within peer-reviewed literature between 1997 and 2006 to provide an up-to-date picture of the role of simulation techniques within manufacturing and business. The review is characterised by three factors: wide coverage, broad scope of the simulation techniques, and a focus on real-world applications. A structured methodology was followed to narrow down the search from around 20,000 papers to 281. Results include interesting trends and patterns. For instance, although discrete event simulation is the most popular technique, it has lower stakeholder engagement than other techniques, such as system dynamics or gaming. This is highly correlated with modelling lead time and purpose. Considering application areas, modelling is mostly used in scheduling. Finally, this review shows an increasing interest in hybrid modelling as an approach to cope with complex enterprise-wide systems. 相似文献
1000.
An adjustable approach to fuzzy soft set based decision making 总被引:2,自引:0,他引:2
Molodtsov’s soft set theory was originally proposed as a general mathematical tool for dealing with uncertainty. Recently, decision making based on (fuzzy) soft sets has found paramount importance. This paper aims to give deeper insights into decision making based on fuzzy soft sets. We discuss the validity of the Roy-Maji method and show its true limitations. We point out that the choice value designed for the crisp case is no longer fit to solve decision making problems involving fuzzy soft sets. By means of level soft sets, we present an adjustable approach to fuzzy soft set based decision making and give some illustrative examples. Moreover, the weighted fuzzy soft set is introduced and its application to decision making is also investigated. 相似文献