全文获取类型
收费全文 | 224篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 108篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 28篇 |
物理学 | 87篇 |
出版年
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 18篇 |
2012年 | 3篇 |
2011年 | 8篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 11篇 |
2001年 | 2篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1957年 | 1篇 |
1939年 | 2篇 |
1938年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有230条查询结果,搜索用时 15 毫秒
101.
We considered the following natural conjecture: For every sorting algorithm every key will be involved in(logn) comparisons for some input. We show that this is true for most of the keys and prove matching upper and lower bounds. Every sorting algorithm for some input will involven–n
/2+1 keys in at leastlog2
n comparisons,>0. Further, there exists a sorting algorithm that will for every input involve at mostn–n
/c
keys in greater thanlog2
n comparisons, wherec is a constant and>0. The conjecture is shown to hold for natural algorithms from the literature. 相似文献
102.
Tushar Ranjan Panda Manikandan M Shreyas P. Vaidya Sushanta Chhatar Suman Sinha Megha Mehrotra Sourav Chakraborty Shubhankar Gadre Prakash Duari Pritha Ray Malay Patra 《Angewandte Chemie (International ed. in English)》2023,62(38):e202303958
Even in the modern era of precision medicine and immunotherapy, chemotherapy with platinum (Pt) drugs remains among the most commonly prescribed medications against a variety of cancers. Unfortunately, the broad applicability of these blockbuster Pt drugs is severely limited by intrinsic and/or acquired resistance, and high systemic toxicity. Considering the strong interconnection between kinetic lability and undesired shortcomings of clinical Pt drugs, we rationally designed kinetically inert organometallic Pt based anticancer agents with a novel mechanism of action. Using a combination of in vitro and in vivo assays, we demonstrated that the development of a remarkably efficacious but kinetically inert Pt anticancer agent is feasible. Along with exerting promising antitumor efficacy in Pt-sensitive as well as Pt-resistant tumors in vivo, our best candidate has the ability to mitigate the nephrotoxicity issue associated with cisplatin. In addition to demonstrating, for the first time, the power of kinetic inertness in improving the therapeutic benefits of Pt based anticancer therapy, we describe the detailed mechanism of action of our best kinetically inert antitumor agent. This study will certainly pave the way for designing the next generation of anticancer drugs for effective treatment of various cancers. 相似文献
103.
104.
Let a bounded full dimensional polytope be defined by the systemAx b whereA is anm × n matrix. Leta
i
denote theith row of the matrixA, and define theweighted analytic center of the polytope to be the point that minimizes the strictly convex barrier function –
i=1
m
w
i
ln(a
i
T
x –b
i
). The proper selection of weightsw
i
can make any desired point in the interior of the polytope become the weighted analytic center. As a result, the weighted analytic center has applications in both linear and general convex programming. For simplicity we assume that the weights are positive integers.If some of thew
i
's are much larger than others, then Newton's method for minimizing the resulting barrier function is very unstable and can be very slow. Previous methods for finding the weighted analytic center relied upon a rather direct application of Newton's method potentially resulting in very slow global convergence. We present a method for finding the weighted analytic center that is based on the scaling technique of Edmonds and Karp and is an enhancement of Newton's method. The scaling algorithm runs in
iterations, wherem is the number of constraints defining the polytope andW is the largest weight given on any constraint. Each iteration involves taking a step in the Newton direction and its complexity is dominated by the time needed to solve a system of linear equations.Supported by the Campus Research Board, University of Illinois at Urbana-Champaign.Supported by the National Science Foundation under Grants CCR-9057481 and CCR-9007195. 相似文献
105.
Pravin M. Vaidya 《Discrete and Computational Geometry》1989,4(1):101-115
Given a setV ofn points ink-dimensional space, and anL
q
-metric (Minkowski metric), the all-nearest-neighbors problem is defined as follows: for each pointp inV, find all those points inV–{p} that are closest top under the distance metricL
q
. We give anO(n logn) algorithm for the all-nearest-neighbors problem, for fixed dimensionk and fixed metricL
q
. Since there is an (n logn) lower bound, in the algebraic decision-tree model of computation, on the time complexity of any algorithm that solves the all-nearest-neighbors problem (fork=1), the running time of our algorithm is optimal up to a constant factor.This research was supported by a fellowship from the Shell Foundation. The author is currently at AT&T Bell Laboratories, Murray Hill, New Jersey, USA. 相似文献
106.
A new series of 6,8-dibromo-2-(4-chlorophenyl)quinazolin-4(3H)-one derivatives VI–XIII were synthesized. Their chemical structures were confirmed by spectral and elemental analysis. The cytotoxic effect of the newly synthesized compounds was tested in vitro against human breast cancer cell line (MCF-7). Most of the tested compounds have shown promising cytotoxic activity. Compounds X and XIIIb exerted a powerful cytotoxic effect against MCF-7 with a very low IC50 (0.0015 and 0.0047 µmol/ml), while compounds VI, VII, VIII, XIIb, XI, XIIIc and IX exerted a moderate cytotoxic effect (IC50 0.01523, 0.0213, 0.031, 0.0478, 0.049, 0.068 and 0.079 µmol/ml respectively), compared to doxorubicin (0.0025 µmol/ml). Exploring their apoptotic effect; interestingly,all compounds activated apoptotic cascade in MCF-7. Compounds VI, XIIIb, XIIb, XI, XIIa, VII, V and VIII showed potent effect even much more than doxorubicin by 12.87–5.91 folds, while compounds XIIIc, IX, XIIIa, XIIc and X showed moderate increase in CASP3 activity by 4.96–3.22 folds relative to untreated cells more or less similar to doxorubicin (5.57 folds). 相似文献
107.
A facile route for the synthesis of novel 3,5,6-trisubstituted-2-pyridones from the acetylated Baylis-Hillman esters with β-enamino esters or β-enamino nitriles in one pot with good yields is described. 相似文献
108.
V. N. Vaidya 《Journal of Sol-Gel Science and Technology》2008,46(3):369-381
Sol–gel process provides an alternate route for fabrication of ceramic nuclear fuel. The sol–gel process provides several
advantages over the conventional powder pellet fabrication process by eliminating handling of radioactive powders. The sol–gel
process uses only fluids or fluid like materials, thus become amenable to remote handling. The sol–gel process has been developed
for the production of coated particle fuels for High Temperature Gas Cooled Reactors (HTGRs), as sphere-pac fuel for Fast
Breeder Reactors (FBRs) and as SGMP fuel for Thermal Reactors. Internal Gelation Process is one of the most important routes
of the sol–gel process and has been accepted as the most promising process route globally. Several countries having plutonium
or 233U based fuel program have developed sol–gel process for nuclear fuels. In India there is special interest for the development
of the sol–gel process for the thorium–uranium fuels keeping in view the large resources of thorium in India. Sol–gel process
for fuel fabrication is also very attractive route for closing the nuclear fuel cycle efficiently.
Author is BRNS Raja Ramanna Fellow. 相似文献
109.
Obliquely propagating altra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized, two fluid dusty
plasma system have been investigated. Two special cases, namely, dust-Alfvén mode propagating parallel to the external magnetic
field and dustmagnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has
been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion
properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that in parallel propagating dust-Alfvén
mode these effects play no role, but in obliquely propagating dust-Alfvén mode or perpendicular propagating dust-magnetosonic
mode the effect of self-gravitational field plays destabilizing role whereas the effect of dust/ion fluid temperature plays
stabilizing role. 相似文献
110.
V. R. Ganatra N. Kumar S. Suryanarayana Y. R. Bamankar N. Reghu V. N. Vaidya S. K. Mukerjee 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(3):515-522
This paper describes Jet Entrainment Technique (JET) developed at Bhabha Atomic Research Centre (BARC) for the preparation
of small microspheres of UO2 in the size range of 100±20 μm diameter. The UO2 microspheres were prepared by Internal Gelation Process (IGP) using selected feed solution compositions. Equipment development
and the optimized process operations for obtaining more than 90% of high density UO2 microspheres in the desired size range are described. 相似文献