全文获取类型
收费全文 | 2488篇 |
免费 | 89篇 |
国内免费 | 9篇 |
专业分类
化学 | 1889篇 |
晶体学 | 25篇 |
力学 | 39篇 |
数学 | 307篇 |
物理学 | 326篇 |
出版年
2023年 | 12篇 |
2022年 | 31篇 |
2021年 | 56篇 |
2020年 | 48篇 |
2019年 | 50篇 |
2018年 | 36篇 |
2017年 | 27篇 |
2016年 | 78篇 |
2015年 | 60篇 |
2014年 | 60篇 |
2013年 | 114篇 |
2012年 | 178篇 |
2011年 | 213篇 |
2010年 | 107篇 |
2009年 | 72篇 |
2008年 | 179篇 |
2007年 | 165篇 |
2006年 | 168篇 |
2005年 | 130篇 |
2004年 | 115篇 |
2003年 | 91篇 |
2002年 | 97篇 |
2001年 | 28篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 22篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 26篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1976年 | 14篇 |
1974年 | 12篇 |
1973年 | 8篇 |
1969年 | 9篇 |
排序方式: 共有2586条查询结果,搜索用时 0 毫秒
1.
Monomeric sarcosine oxidase (mSOx) fusion with the silaffin peptide, R5, designed previously for easy protein production in low resource areas, was used in a biosilification process to form an enzyme layer electrode biosensor. mSOx is a low activity enzyme (10–20 U/mg) requiring high amounts of enzyme to obtain an amperometric biosensor signal, in the clinically useful range <1 mM sarcosine, especially since the Km is >10 mM. An amperometric biosensor model was fitted to experimental data to investigate dynamic range. mSOx constructs were designed with 6H (6×histidine) and R5 (silaffin) peptide tags and compared with native mSOx. Glutaraldehyde (GA) cross‐linked proteins retained ~5 % activity for mSOx and mSOx‐6H and only 0.5 % for mSOx‐R5. In contrast R5 catalysed biosilification on (3‐mercaptopropyl) trimethoxysilane (MPTMS) and tetramethyl orthosilicate (TMOS) particles created a ‘self‐immobilisation’ matrix retaining 40 % and 76 % activity respectively. The TMOS matrix produced a thick layer (>500 μm) on a glassy carbon electrode with a mediated current due to sarcosine in the clinical range for sarcosinemia (0–1 mM). The mSOx‐R5 fusion protein was also used to catalyse biosilification in the presence of creatinase and creatininase, entrapping all three enzymes. A mediated GC enzyme linked current was obtained with dynamic range available for creatinine determination of 0.1–2 mM for an enzyme layer ~800 nm. 相似文献
2.
Elizabeth S. Senger 《School science and mathematics》1997,97(3):139-149
Thirteen fifth graders were given an assignment to invent their own numeration systems, following a unit on bases and a look at early events in the history of numbers. The task presented options that required the students to make decisions (such as whether to use a base, which base to use, design of symbols, etc.), and build a rationale for the elements of their system. Analyses of patterns embedded in their invented systems provided an assessment of student understanding of numeration. The progression of more and less complex thinking related to the student's choice of a base other than 10, consistency of logic throughout the system in words and symbols, rationale for change, and perception of real life examples that would change if the system was adopted. The invention task is presented as another way to make connections. 相似文献
3.
We consider a randomized version of the greedy algorithm for finding a large matching in a graph. We assume that the next edge is always randomly chosen from those remaining. We analyze the performance of this algorithm when the input graph is fixed. We show that there are graphs for which this Randomized Greedy Algorithm (RGA) usually only obtains a matching close in size to that guaranteed by worst-case analysis (i.e., half the size of the maximum). For some classes of sparse graphs (e.g., planar graphs and forests) we show that the RGA performs significantly better than the worst-case. Our main theorem concerns forests. We prove that the ratio to maximum here is at least 0.7690…, and that this bound is tight. 相似文献
4.
We investigate the conjecture that every circulant graph X admits a k‐isofactorization for every k dividing |E(X)|. We obtain partial results with an emphasis on small values of k. © 2006 Wiley Periodicals, Inc. J Combin Designs 14: 406–414, 2006 相似文献
5.
Accreditation and Quality Assurance - 相似文献
6.
Elizabeth Wulcan 《Arkiv f?r Matematik》2007,45(1):157-178
With a given holomorphic section of a Hermitian vector bundle, one can associate a residue current by means of Cauchy–Fantappiè–Leray
type formulas. In this paper we define products of such residue currents. We prove that, in the case of a complete intersection,
the product of the residue currents of a tuple of sections coincides with the residue current of the direct sum of the sections. 相似文献
7.
8.
We close a gap in the proof of Theorem 4.1 in our paper “The complexity of counting graph homomorphisms” [Random Structures Algorithms 17 (2000), 260–289]. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004 相似文献
9.
Motivated by the central limit problem for convex bodies, we study normal approximation of linear functionals of high-dimensional
random vectors with various types of symmetries. In particular, we obtain results for distributions which are coordinatewise
symmetric, uniform in a regular simplex, or spherically symmetric. Our proofs are based on Stein’s method of exchangeable
pairs; as far as we know, this approach has not previously been used in convex geometry. The spherically symmetric case is
treated by a variation of Stein’s method which is adapted for continuous symmetries.
This work was done while at Stanford University. 相似文献
10.
Elizabeth A. Lewis 《Tetrahedron letters》2004,45(15):3059-3062
An efficient synthesis of C-functionalised cyclam macrocycles that employs bisaminal intermediates and allows N-substitution to be controlled is reported. 相似文献