全文获取类型
收费全文 | 877篇 |
免费 | 42篇 |
国内免费 | 3篇 |
专业分类
化学 | 611篇 |
晶体学 | 12篇 |
力学 | 35篇 |
数学 | 86篇 |
物理学 | 178篇 |
出版年
2024年 | 4篇 |
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 21篇 |
2020年 | 18篇 |
2019年 | 27篇 |
2018年 | 21篇 |
2017年 | 36篇 |
2016年 | 44篇 |
2015年 | 33篇 |
2014年 | 37篇 |
2013年 | 86篇 |
2012年 | 76篇 |
2011年 | 73篇 |
2010年 | 61篇 |
2009年 | 43篇 |
2008年 | 43篇 |
2007年 | 50篇 |
2006年 | 42篇 |
2005年 | 34篇 |
2004年 | 24篇 |
2003年 | 25篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1984年 | 2篇 |
排序方式: 共有922条查询结果,搜索用时 31 毫秒
91.
A novel piezoelectric (PZ) immunosensor for the direct detection of malarial Plasmodium falciparum histidine rich protein-2 (PfHRP-2) antigen was developed. The mixed self-assembled monolayers (SAMs) of thioctic acid and 1-dodecanethiol were formed on gold surface of quartz crystal. Cyclic voltammetry, electrochemical impedance spectroscopy and surface Raman spectroscopy techniques were used to characterize the mixed SAMs. The rabbit anti-PfHRP-2 antibodies were coupled on mixed SAM modified gold surface of quartz crystal via NHS/EDC activation method. The PZ immunosensor was applied to detect PfHRP-2 in the linear range of 15-60 ng/ml with a detection limit of 12 ng/ml. It was also found that even after 14 days of storage, 50% of the activity still remained. Clinical human serum samples were tested with this method, and the results were in agreement with those obtained from commercially available ICT kit (NOW® Malaria). 相似文献
92.
Sanjay Kumar Venkata Dasu Veeranki Kannan Pakshirajan 《Applied biochemistry and biotechnology》2011,163(3):327-337
Statistically based experimental design was applied to maximize the production of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428. The effect of physical process parameters (initial pH of the medium, temperature, rpm of the shaking incubator,
and inoculum size) on the production of L-asparaginase from P. carotovorum MTCC 1428 was studied using central composite design technique. The individual optimum levels of initial pH of the medium,
temperature, rpm of shaking incubator, and inoculum size were found to be 6.90, 29.8 °C, 157 rpm, and 2.61% (v/v), respectively, for the production of L-asparaginase. After physical process parameters optimization, the production and
productivity of L-asparaginase was enhanced by 26.39% (specific activity) and 10.19%, respectively. Maximization of L-asparaginase
production was achieved at 12 h under optimal levels of physical process parameters in shake flask level. 相似文献
93.
Singh A Mukherjee A Vermeulen HM Barkema GT Puri S 《The Journal of chemical physics》2011,134(4):044910
In this paper, we study the evolution of phase-separating binary mixtures which are subjected to alternate cooling and heating cycles. An initially homogeneous mixture is rapidly quenched to a temperature T(1)T(c). These cycles are repeated to create a domain morphology with multiple length scales, i.e., the structure factor is characterized by multiple peaks. For phase separation in d = 2 systems, we present numerical and analytical results for the emergence and growth of this multiple-scale morphology. 相似文献
94.
Kasture S Pawar A Kasture A Foddis C Frau MA Maxia A 《Natural product research》2011,25(20):1950-1954
In the traditional system of medicine in Sardinia, Rubia peregrina (RP) is reported as an aphrodisiac herb. Since aphrodisiacs may also have dopaminergic activity, and there can be a reciprocal relationship between dopaminergic and serotonergic functions in the central nervous system, the aim here was to study the effect of the ethanolic extract of the aerial parts of R. peregrina on monoamine-mediated behaviour. The RP (100 and 200?mg?kg(-1) intraperitoneally) significantly inhibited haloperidol (1?mg?kg(-1) i.p.) induced catalepsy in mice (p?0.01, dopamine-mediated response) lithium sulphate induced head twitches in rats (serotonin-mediated response) and was without effect on clonidine-induced hypothermia in rats (noradrenaline-mediated response). The study concludes that R. peregrina improves the dopaminergic function, diminishes the serotonin-mediated function and is devoid of any effect on the noradrenergic function. The study suggests that we should carry out further experiments to investigate the psychopharmacological profile of R. peregrina. 相似文献
95.
We present branching-on-hyperplane methods for solving mixed integer linear and mixed integer convex programs. In particular,
we formulate the problem of finding a good branching hyperplane using a novel concept of adjoint lattice. We also reformulate
the problem of rounding a continuous solution to a mixed integer solution. A worst case complexity of a Lenstra-type algorithm
is established using an approximate log-barrier center to obtain an ellipsoidal rounding of the feasible set. The results
for the mixed integer convex programming also establish a complexity result for the mixed integer second order cone programming
and mixed integer semidefinite programming feasibility problems as a special case. Our results motivate an alternative reformulation
technique and a branching heuristic using a generalized (e.g., ellipsoidal) norm reduced basis available at the root node. 相似文献
96.
Hay and, then, Johnson extended the classic Rice and Rice‐Shapiro Theorems for computably enumerable sets, to analogs for all the higher levels in the finite Ershov Hierarchy. The present paper extends their work (with some motivations presented) to analogs in the transfinite Ershov Hierarchy. Some of the transfinite cases are done for all transfinite notations in Kleene's important system of notations, $\mathcal {O}$. Other cases are done for all transfinite notations in a very natural, proper subsystem $\mathcal {O}_{\mathrm{Cantor}}$ of $\mathcal {O}$, where $\mathcal {O}_{\mathrm{Cantor}}$ has at least one notation for each constructive ordinal. In these latter cases it is open as to what happens for the entire set of transfinite notations in $(\mathcal {O} -\mathcal {O}_{\mathrm{Cantor}})$. 相似文献
97.
Dasgupta S Banerjee K Utture S Kusari P Wagh S Dhumal K Kolekar S Adsule PG 《Journal of chromatography. A》2011,1218(38):6780-6791
98.
Pandey R Kumar P Singh AK Shahid M Li PZ Singh SK Xu Q Misra A Pandey DS 《Inorganic chemistry》2011,50(8):3189-3197
Binuclear zinc(II) and copper(II) complexes based on a new Schiff base ligand N,N'-bis(2-hydroxybenzilidene)-2,4,6-trimethylbenzene-1,3-diamine (H(2)L) have been synthesized. The ligand H(2)L and complexes under investigation have been characterized by elemental analyses, spectral (FT-IR, (1)H, (13)C NMR, ESI-MS, electronic absorption, emission), and electrochemical studies. The structures of H(2)L and complexes [{Zn(C(23)H(18)N(2)O(2))}(2)] (1) and [{Cu(C(23)H(18)N(2)O(2))}(2)]·H(2)O (2) have been determined crystallographically. Selective "On-Off-On" switching behavior of the fluorescent complex 1 has been studied. The fluorescence intensity of 1 quenches (turns-off) upon addition of Cu(2+), while enhances (turns-on) in the presence of Ag(+) ions. The mechanisms of "On-Off-On" signaling have been supported by (1)H NMR, ESI-MS, electronic absorption, and emission spectral studies. Job's plot analysis supported 1:1 and 1:2 stoichiometries for Cu(2+) and Ag(+) ions, respectively. Association and quenching constants have been estimated by the Benesi-Hildebrand method and Stern-Volmer plot. Moreover, 1 mimics a molecular keypad lock that follows correct chemical input order to give maximum output signal. 相似文献
99.
Monocyclic as well as fused bicyclic systems with a nitrogen 10 atom at the bridgehead, including indolizidines and quinolizidines, can be prepared in four steps from N-Boc β-lactams. These easily prepared, highly robust, and flexible building blocks allow the incorporation of chirality and structural diversity, rendering the method feasible for diversity- as well as target-oriented synthesis. 相似文献
100.