全文获取类型
收费全文 | 30843篇 |
免费 | 148篇 |
国内免费 | 276篇 |
专业分类
化学 | 11776篇 |
晶体学 | 319篇 |
力学 | 1445篇 |
综合类 | 12篇 |
数学 | 9355篇 |
物理学 | 8360篇 |
出版年
2022年 | 126篇 |
2021年 | 128篇 |
2020年 | 64篇 |
2019年 | 62篇 |
2018年 | 1250篇 |
2017年 | 1502篇 |
2016年 | 798篇 |
2015年 | 627篇 |
2014年 | 572篇 |
2013年 | 823篇 |
2012年 | 3209篇 |
2011年 | 2386篇 |
2010年 | 1879篇 |
2009年 | 1603篇 |
2008年 | 661篇 |
2007年 | 676篇 |
2006年 | 669篇 |
2005年 | 4489篇 |
2004年 | 3962篇 |
2003年 | 2334篇 |
2002年 | 511篇 |
2001年 | 304篇 |
2000年 | 118篇 |
1999年 | 189篇 |
1998年 | 131篇 |
1997年 | 85篇 |
1996年 | 62篇 |
1995年 | 55篇 |
1994年 | 54篇 |
1992年 | 188篇 |
1991年 | 175篇 |
1990年 | 151篇 |
1989年 | 127篇 |
1988年 | 111篇 |
1987年 | 70篇 |
1986年 | 54篇 |
1985年 | 69篇 |
1984年 | 62篇 |
1983年 | 45篇 |
1981年 | 37篇 |
1979年 | 51篇 |
1976年 | 82篇 |
1975年 | 41篇 |
1974年 | 45篇 |
1973年 | 51篇 |
1972年 | 43篇 |
1970年 | 37篇 |
1969年 | 42篇 |
1968年 | 36篇 |
1966年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
971.
Stanislaw Barder Jüri Lember Heinrich Matzinger M?rt Toots 《Methodology and Computing in Applied Probability》2012,14(2):357-382
Let X = X
1 ... X
n
and Y = Y
1 ... Y
n
be two binary sequences with length n. A common subsequence of X and Y is any subsequence of X that at the same time is a subsequence of Y; The common subsequence with maximal length is called the longest common subsequence (LCS) of X and Y. LCS is a common tool for measuring the closeness of X and Y. In this note, we consider the case when X and Y are both i.i.d. Bernoulli sequences with the parameters ϵ and 1 − ϵ, respectively. Hence, typically the sequences consist of large and short blocks of different colors. This gives an idea to
the so-called block-by-block alignment, where the short blocks in one sequence are matched to the long blocks of the same
color in another sequence. Such and alignment is not necessarily a LCS, but it is computationally easy to obtain and, therefore,
of practical interest. We investigate the asymptotical properties of several block-by-block type of alignments. The paper
ends with the simulation study, where the of block-by-block type of alignments are compared with the LCS. 相似文献
972.
973.
Three new chiral urea-type anion receptors were synthesized from aromatic diamines and 1-amino-1-deoxyglucose. The anion binding properties of these receptors were studied using chiral carboxylates derived from mandelic acid and three α-amino acids. We found that the size of the anion binding pocket played an important role in chiral recognition processes. The best results were obtained for 1,8-diaminoanthracene and α-amino acid anions. 相似文献
974.
Filip Ciesielczyk Przemysław Bartczak Karolina Wieszczycka Katarzyna Siwińska-Stefańska Magdalena Nowacka Teofil Jesionowski 《Adsorption》2013,19(2-4):423-434
The aim of this work was to obtain an inorganic oxide system containing silica and magnesium oxide, and characterized by specific physicochemical properties, in particular well-defined adsorption parameters. The preparation process was carried out according to a co-precipitation method using solutions of sodium silicate and selected inorganic magnesium salt. The oxide system obtained (MgO·SiO2) was used as a support (adsorbent) of nickel(II) ions, whose precursors were model solutions of nitrates. The effectiveness of the adsorption process was evaluated using many different analytical techniques, including atomic absorption spectroscopy, energy dispersive X-ray spectroscopy and equivalent point titration. Moreover the stability of adsorbent/adsorbate bonding was estimated. The oxide systems—adsorbents—used in the process were also analyzed according to their physicochemical properties, especially changes in adsorption parameters. The last part of the study involved evaluation of the kinetics of the adsorption process depending on time and the pH of the reaction system. 相似文献
975.
976.
The paper presents a survey of the main results of I.M. Vinogradov. 相似文献
977.
Mirosław Jabłoński 《Structural chemistry》2017,28(6):1697-1706
It is shown that the H ? B contacts in 1-silacyclohex-2-enes are clearly stabilizing and strong, whereas those in 1-silacyclopent-2-enes are much weaker. This result is supported by analysis of QTAIM-based parameters and appropriate structural changes taking place upon the open form → closed form transformation and is in full agreement with previous NMR spectroscopic data [Wrackmeyer et al. (2006) Appl Organometal Chem 20:99–105]. Also, the influence of electronic and steric effects originating from the presence of specific substituents on the strength of the H ? B contacts is discussed in detail. Some problems and ideas associated with the use of the so-called open-closed method utilized in assessing values of interaction energies are discussed in detail. Particular attention is paid to the correct choice of reference open systems. It is shown that their partial geometry optimization leads to reliable values of interaction energies. 相似文献
978.
979.
980.
Miroslav Veverka Peter ?imon Ján Lokaj Eva Veverková 《Monatshefte für Chemie / Chemical Monthly》2012,10(4):65-71