全文获取类型
收费全文 | 1368篇 |
免费 | 55篇 |
国内免费 | 14篇 |
专业分类
化学 | 1091篇 |
晶体学 | 10篇 |
力学 | 11篇 |
数学 | 103篇 |
物理学 | 222篇 |
出版年
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 16篇 |
2020年 | 5篇 |
2019年 | 34篇 |
2018年 | 21篇 |
2017年 | 9篇 |
2016年 | 20篇 |
2015年 | 39篇 |
2014年 | 35篇 |
2013年 | 97篇 |
2012年 | 91篇 |
2011年 | 91篇 |
2010年 | 60篇 |
2009年 | 58篇 |
2008年 | 94篇 |
2007年 | 103篇 |
2006年 | 100篇 |
2005年 | 95篇 |
2004年 | 80篇 |
2003年 | 53篇 |
2002年 | 62篇 |
2001年 | 13篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 19篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 9篇 |
排序方式: 共有1437条查询结果,搜索用时 62 毫秒
71.
Solubility of several anthraquinone derivatives in supercritical carbon dioxide was readily available in the literature, but correcting ability of the existing models was poor. Therefore, in this work, two new models have been developed for better correlation based on solid–liquid phase equilibria. The new model has five adjustable parameters correlating the solubility isotherms as a function of temperature. The accuracy of the proposed models was evaluated by correlating 25 binary systems. The proposed models observed provide the best overall correlations. The overall deviation between the experimental and the correlated results was less than 11.46% in averaged absolute relative deviation (AARD). Moreover, exiting solubility models were also evaluated for all the compounds for the comparison purpose. 相似文献
72.
We study the effects of metal-coated fiber near-field probes on the performance of nanophotonic devices. Employing a heterodyne near-field scanning optical microscope and analyzing transmission characteristics, we find that a metal-coated probe can typically introduce a 3 dB intensity loss and a 0.2 rad phase shift during characterization of a straight waveguide made in a silicon-on-insulator system. In resonant nanophotonic structures such as a 5 mum radius microring resonator, we demonstrate that the probe induces a 1 nm shift in resonant wavelength and decreases the resonator quality factor, Q, from 1100 to 480. 相似文献
73.
Quantitative Detection for Porphyromonas gingivalis in Tooth Pocket and Saliva by Portable Electrochemical DNA Sensor Linked with PCR 下载免费PDF全文
Keiichiro Yamanaka Shinichi Sekine Takahiro Uenoyama Masahiro Wada Tomohiko Ikeuchi Masato Saito Yoshinori Yamaguchi Eiichi Tamiya 《Electroanalysis》2014,26(12):2686-2692
Here, a quantitative electrochemical analysis of periodontal bacteria in gingival crevicular fluid (GCF) and saliva by direct polymerase chain reaction (PCR) is presented. The electrochemical measurement was performed by mixing with PCR products and electrochemical indicator (bisbenzimidazole trihydrochloride). The peak current of indicator is reduced due to slower diffusion when the dye intercalates into the amplified DNA, and the degree of reduction in the peak current is correlates with the quantity of amplified DNA. Therefore, a quantitative analysis is possible by using our electrochemical method at the end point of PCR. In the GCF testing, The number of Porphyromonas gingivalis (Pg) detected by our electrochemical method at the end point of PCR were almost same compared with that were calculated by the conventional method of quantitative real? time PCR. In the saliva testing, the relationship between number of Pg in saliva and average pocket depth, and age‐dependence were also clearly observed. Since the saliva sample is obtained in a non‐invasive manner, this method is useful for the primary screening of periodontal disease. Moreover, our detection method is simple and uses a hand‐held potentiostat making it suitable for development of an on‐site periodontal diagnosis system. 相似文献
74.
Protein kinase C (PKC) isozymes play central roles in signal transduction on the cell surface and could serve as promising therapeutic targets of intractable diseases like cancer, Alzheimer's disease, and acquired immunodeficiency syndrome (AIDS). Although natural PKC ligands like phorbol esters, ingenol esters, and teleocidins have the potential to become therapeutic leads, most of them are potent tumor promoters in mouse skin. By contrast, bryostatin‐1 (bryo‐1) isolated from marine bryozoan is a potent PKC activator with little tumor‐promoting activity. Numerous investigations have suggested bryo‐1 to be a promising therapeutic candidate for the above intractable diseases. However, there is a supply problem of bryo‐1 both from natural sources and by organic synthesis. Recent approaches on the synthesis of bryo‐1 have focused on its simplification, without decreasing the ability to activate PKC isozymes, to develop new medicinal leads. Another approach is to use the skeleton of natural PKC ligands to develop bryo‐1 surrogates. We have recently identified 10‐methyl‐aplog‐1 ( 26 ), a simplified analog of tumor‐promoting aplysiatoxin (ATX), as a possible therapeutic lead for cancer. This review summarizes recent investigations on the simplification of natural PKC ligands, bryo‐1 and ATX, to develop potential medicinal leads. 相似文献
75.
Kazuhiro Ishida 《International journal of quantum chemistry》1996,59(3):209-218
A new series of general formulas to evaluate the electron-repulsion integral (ERI) can be derived from modifying the Gauss-Rys quadrature formula. These named as “accompanying coordinate expansion (ACE) formulas” are capable of evaluating very fast ERIs, especially for contracted Gaussian-type orbitals (GTOs). According to the degree of the contraction of GTOs, the optimum formula can be selected among these ACEs. Numerical examples are shown for (ps|ps) and (pp|pp) ERIs as typical examples. It is found that the present ACE algorithm is numerically stable and is most efficient among all algorithms in the literature in the floating-point-operation (FLOP) count for all varieties of the degree of contraction. © 1996 John Wiley & Sons, Inc. 相似文献
76.
77.
Synthesis of medium-sized carbocyclic ketones via the intramolecular B-alkyl Liebeskind-Srogl coupling reaction is described. The sequence of hydroboration of ω-alkenyl thiol ester with 9-BBN and the Liebeskind-Srogl reaction results in the formation of medium-sized carbocyclic ketones with good yield. 相似文献
78.
79.
Pd(II)-SPRIX catalyst coupled with an environmentally benign molecular oxygen as the sole oxidant successfully exploited the construction of pyrrolizines/pyrroloindoles, imperative scaffolds of bio-potent molecules through intramolecular C-N and C-C bond forming reactions in good yields with appreciable enantioselectivities. 相似文献