全文获取类型
收费全文 | 7352篇 |
免费 | 390篇 |
国内免费 | 55篇 |
专业分类
化学 | 5483篇 |
晶体学 | 51篇 |
力学 | 163篇 |
数学 | 679篇 |
物理学 | 1421篇 |
出版年
2023年 | 31篇 |
2022年 | 80篇 |
2021年 | 156篇 |
2020年 | 123篇 |
2019年 | 135篇 |
2018年 | 115篇 |
2017年 | 102篇 |
2016年 | 236篇 |
2015年 | 223篇 |
2014年 | 266篇 |
2013年 | 464篇 |
2012年 | 525篇 |
2011年 | 620篇 |
2010年 | 376篇 |
2009年 | 295篇 |
2008年 | 483篇 |
2007年 | 428篇 |
2006年 | 437篇 |
2005年 | 378篇 |
2004年 | 342篇 |
2003年 | 281篇 |
2002年 | 260篇 |
2001年 | 143篇 |
2000年 | 125篇 |
1999年 | 90篇 |
1998年 | 60篇 |
1997年 | 57篇 |
1996年 | 72篇 |
1995年 | 65篇 |
1994年 | 56篇 |
1993年 | 41篇 |
1992年 | 39篇 |
1991年 | 29篇 |
1990年 | 42篇 |
1989年 | 40篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 21篇 |
1985年 | 48篇 |
1984年 | 32篇 |
1983年 | 24篇 |
1982年 | 27篇 |
1981年 | 27篇 |
1980年 | 22篇 |
1979年 | 33篇 |
1978年 | 20篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1975年 | 20篇 |
1973年 | 28篇 |
排序方式: 共有7797条查询结果,搜索用时 46 毫秒
991.
992.
993.
Experimentally and theoretically derived formation constants of mixed lead halide complexes are compared at 25.0°C and one molar ionic strength. The formation constant of PbBrCl, 11=79±10, is somewhat larger than the theoretical results, 11=55, predicted using the formation constants of PbBr2 and PbCl2. The molar absorptivity of PbBrCl was observed to be intermediate in character between the molar absorptivities of PbBr2 and PbCl2. Determinations of the formation constants of PbBr2Cl– and PbBrCl2
– are in reasonable agreement with the predictions based on the formation constants of PbBr3
– and PbCl3
–. Mixed ligand species dominated the complexation scheme of Pb(II) in our test media. 相似文献
994.
Polyelectrolyte multilayer capsule reactors (PEMCRs) for the synthesis of two types of nanoparticles were prepared. The tunable PEMCRs containing two different functional groups that can be used to synthesize two types of nanoparticles simultaneously and to control the composition of two types of nanoparticles within the shell of PEMCs. These PEMCRs enabled the composition as well as the amount of the loaded two types of nanoparticles within the shell of PEMCs to be controlled by the copolymer ratio and the number of reaction cycles. Another interesting finding is that, as a result of the synthesis of two types of nanoparticles, these specially designed PEMCs containing both silver and goethite nanocrystals can be used as antimicrobial capsules, which can move by an external magnetic field. Such a technology has the potential for use in sterilization at the desirable sites. 相似文献
995.
Phytochemical investigation of Ginkgo biloba (Ginkgoaceae) has resulted in the isolation of two new biflavone glucosides, ginkgetin 7'-O-beta-D-glucopyranoside (1) and isoginkgetin 7-O-beta-D-glucopyranoside (2). The structures were determined on the basis of chemical and spectroscopic evidences. 相似文献
996.
Two new neolignans (1, 2) were isolated from the aerial parts of Rodgersia podophylla, along with four known neolignans, and their structures were elucidated using spectral experiments and comparison with literature data. 相似文献
997.
We have performed an unbiased search for the global minimum geometries of small-to-medium sized germanium clusters Gen(12< or =n< or =18) as well as a biased search (using seeding method) for Gen(17< or =n< or =20). We employed the basin-hopping algorithm coupled with the plane-wave pseudopotential density functional calculations. For each size, we started the unbiased search with using several structurally very different initial clusters, or we started the biased search with three different seeds. Irrespective of the initial structures of clusters we found that the obtained lowest-energy clusters of the size n=12-16 and 18 are the same. Among them, the predicted global minima of Gen(12< or =n< or =16) are identical to those reported previously [Shvartsburg et al., Phys. Rev. Lett. 83, 167 (1999)]. For n=17-20, we have identified two or three nearly isoenergetic low-lying isomers (for each size) that compete for the global minimum. Nearly all the low-lying clusters in the size range of 12< or =n< or =20 contain the tri-caped trigonal prism motif and are all prolate in geometry, in agreement with the experiment. 相似文献
998.
Kim K Byun Y Kim C Kim TC Noh DY Shin K 《Journal of colloid and interface science》2005,284(1):107-113
We investigated the detailed structure of a surface-grafted phospholipid monolayer, which was polymerized in situ onto a methacryloyl-silanized solid surface. By the combined study of X-ray reflectivity and atomic force microscopy, the in situ polymerization step of the lipid molecules are sufficiently detailed to reveal the molecular structure of lipid molecules before and after in situ polymerization. From the data of the X-ray reflectivity, we confirmed that the in situ polymerization process produces a flat lipid monolayer structure and that the lipid monolayer is substantially grafted on a silanized surface by chemical bonding. After the polymerization and washing processes, the thickness of the head group was 9 angstroms and the thickness of the tail group was 21 angstroms. The surface morphology of the polymerized phospholipid monolayer obtained by the measurements of atomic force microscopy was consistent with the results of the X-ray reflectivity. The cross-sectional analysis shows that the surface coverage of lipid molecules, which are chemically grafted onto a silanized surface, is approximately 89%. 相似文献
999.
Karr AF Feng J Lin X Sanil AP Young SS Reiter JP 《Journal of computer-aided molecular design》2005,19(9-10):739-747
We present a method for performing statistically valid linear regressions on the union of distributed chemical databases that preserves confidentiality of those databases. The method employs secure multi-party computation to share local sufficient statistics necessary to compute least squares estimators of regression coefficients, error variances and other quantities of interest. We illustrate our method with an example containing four companies' rather different databases. 相似文献
1000.
Moss JA Lillo A Kim YS Gao C Ditzel H Janda KD 《Journal of the American Chemical Society》2005,127(2):538-539
The internalization mechanism of a cell-penetrating peptide has been explored through combinatorial selection of a phage-displayed peptide dimer library, chemical synthesis, and biophysical characterization. Both energy-dependent and energy-independent modes for peptide uptake by the target mammalian cells were observed, suggesting a role for higher-order structure in modulating the action of this novel cell-penetrating peptide. 相似文献