全文获取类型
收费全文 | 2626篇 |
免费 | 53篇 |
国内免费 | 9篇 |
专业分类
化学 | 1921篇 |
晶体学 | 39篇 |
力学 | 35篇 |
数学 | 190篇 |
物理学 | 503篇 |
出版年
2020年 | 18篇 |
2019年 | 23篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 36篇 |
2015年 | 37篇 |
2014年 | 45篇 |
2013年 | 130篇 |
2012年 | 103篇 |
2011年 | 144篇 |
2010年 | 82篇 |
2009年 | 87篇 |
2008年 | 136篇 |
2007年 | 146篇 |
2006年 | 145篇 |
2005年 | 133篇 |
2004年 | 126篇 |
2003年 | 117篇 |
2002年 | 111篇 |
2001年 | 52篇 |
2000年 | 52篇 |
1999年 | 39篇 |
1998年 | 23篇 |
1997年 | 42篇 |
1996年 | 37篇 |
1995年 | 20篇 |
1994年 | 39篇 |
1993年 | 36篇 |
1992年 | 33篇 |
1991年 | 23篇 |
1990年 | 30篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 30篇 |
1986年 | 22篇 |
1985年 | 58篇 |
1984年 | 40篇 |
1983年 | 26篇 |
1982年 | 43篇 |
1981年 | 38篇 |
1980年 | 44篇 |
1979年 | 43篇 |
1978年 | 29篇 |
1977年 | 22篇 |
1976年 | 30篇 |
1975年 | 18篇 |
1974年 | 18篇 |
1973年 | 25篇 |
1972年 | 14篇 |
1968年 | 11篇 |
排序方式: 共有2688条查询结果,搜索用时 453 毫秒
991.
Surface structures of rutile TiO(2) (011) are determined by a combination of noncontact atomic force microscopy (NC-AFM), scanning tunneling microscopy (STM), and density functional calculations. The surface exhibits rowlike (n x 1) structures running along the [01] direction. Microfaceting missing-row structural models can explain the experimental results very well. Calculated images for NC-AFM and STM are in good agreement with the experimental results. A decrease of the density of dangling bonds stabilizes the surface energy, which results in the microfaceting missing-row reconstructions. 相似文献
992.
993.
An on-chip cardiomyocyte cell network assay for stable drug screening regarding community effect of cell network size 总被引:1,自引:0,他引:1
We investigate the effect of haloperidol on a four-cell and nine-cell cardiomyocyte network on an agarose microchamber array chip to evaluate a cell-based model for drug screening. Using a network of cardiomyocytes whose beating intervals were stable and relatively uniform (they only fluctuated 10% from the mean beating interval), we easily observed the effect of haloperidol on the cell network beating interval 5 min after administering it. We also observed the beating interval returned to its original state 10 min after the haloperidol was washed out of the chip. Although the four-cell network showed the unstable recovery of its beating rhythm after washout of haloperidol, the nine-cell network recovered completely to the stable original beating rhythm even after a second administration of haloperidol. The results indicate the importance of the community size in cell networks used in the stable cell-based screening model. Moreover, they indicate the advantage of using direct cell-based measurements in which the amount of drug administered and the time course over which it is administered are strictly controlled for evaluating the quantitative chemical effects of drugs on cells. 相似文献
994.
Redox reactions involving the [Cu(dmp)2]2+/+ couple (dmp = 2,9-dimethyl-1,10-phenanthroline) in acetonitrile were examined at elevated pressures up to 200 MPa. Activation volumes were determined as -8.8 and -6.3 cm3 mol-1 for the reduction cross-reaction by [Co(bipy)3]2+ (bipy = 2,2'-bipyridine) and for the oxidation cross-reaction by [Ni(tacn)2]3+ (tacn = 1,4,7-triazacyclononane), respectively. The activation volume for the hypothetical gated mode of the self-exchange reaction estimated from the reduction cross-reaction was -13.9 cm3 mol-1, indicating extensive electrostrictive rearrangement of solvent molecules around the CuII complex during the change in the coordination geometry before the electron-transfer step. On the other hand, the activation volume for the self-exchange reaction estimated from the oxidation cross-reaction was -2.7 +/- 1.5 cm3 mol-1. Although this value was within the range that can be interpreted by the concept of the ordinary concerted process, from theoretical considerations it was concluded that the reverse (oxidation) cross-reaction of the gated reduction reaction of the [Cu(dmp)2(CH3CN)]2+/[Cu(dmp)2]+ couple proceeds through the product excited state while the direct self-exchange reaction between [Cu(dmp)2(CH3CN)]2+ and [Cu(dmp)2]+ proceeds through an ordinary concerted process. 相似文献
995.
996.
Optical imaging including fluorescence and luminescence is the most popular method for the in vivo imaging in mice. Luminescence imaging is considered to be superior to fluorescence imaging due to the lack of both autofluorescence and the scattering of excitation light. To date, various luciferin analogs and bioluminescence probes have been developed for deep tissue and molecular imaging. Recently, chemiluminescence probes have been developed based on a 1,2-dioxetane scaffold. In this review, the accumulated findings of numerous studies and the design strategies of bioluminescence and chemiluminescence imaging reagents are summarized. 相似文献
997.
Suzuki Jun-ichi Takegahara Yutaro Oikawa Yuri Chiba Masaya Yamada Satoshi Sugiya Masashi Sawada Hideo 《Journal of Sol-Gel Science and Technology》2017,81(2):611-622
Journal of Sol-Gel Science and Technology - Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R F-(CH2CHSi(OMe)3) n -R F; R F?=?CF(CF3)OC3F7, n?=?2, 3: R F-(VM) n -R F... 相似文献
998.
Naohiko Arima Sunyoung Kim Masakazu Kojima Kim-Chuan Toh 《Computational Optimization and Applications》2017,66(3):453-479
The Lagrangian-doubly nonnegative (DNN) relaxation has recently been shown to provide effective lower bounds for a large class of nonconvex quadratic optimization problems (QAPs) using the bisection method combined with first-order methods by Kim et al. (Math Program 156:161–187, 2016). While the bisection method has demonstrated the computational efficiency, determining the validity of a computed lower bound for the QOP depends on a prescribed parameter \(\epsilon > 0\). To improve the performance of the bisection method for the Lagrangian-DNN relaxation, we propose a new technique that guarantees the validity of the computed lower bound at each iteration of the bisection method for any choice of \(\epsilon > 0\). It also accelerates the bisection method. Moreover, we present a method to retrieve a primal-dual pair of optimal solutions of the Lagrangian-DNN relaxation using the primal-dual interior-point method. As a result, the method provides a better lower bound and substantially increases the robustness as well as the effectiveness of the bisection method. Computational results on binary QOPs, multiple knapsack problems, maximal stable set problems, and quadratic assignment problems illustrate the robustness of the proposed method. In particular, a tight bound for QAPs with size \(n=50\) could be obtained. 相似文献
999.
1000.
Kojima T Nishida J Tokito S Tada H Yamashita Y 《Chemical communications (Cambridge, England)》2007,(14):1430-1432
New oligomers containing a pyrazine unit have been prepared: the bithienyl derivatives afforded p-type FET devices whereas the trifluoromethylphenyl derivatives showed n-type FET behavior. 相似文献