全文获取类型
收费全文 | 102552篇 |
免费 | 17676篇 |
国内免费 | 10038篇 |
专业分类
化学 | 69648篇 |
晶体学 | 1177篇 |
力学 | 6843篇 |
综合类 | 542篇 |
数学 | 12007篇 |
物理学 | 40049篇 |
出版年
2024年 | 107篇 |
2023年 | 2073篇 |
2022年 | 2217篇 |
2021年 | 3495篇 |
2020年 | 4216篇 |
2019年 | 4065篇 |
2018年 | 3443篇 |
2017年 | 3176篇 |
2016年 | 5028篇 |
2015年 | 4736篇 |
2014年 | 5803篇 |
2013年 | 7582篇 |
2012年 | 9285篇 |
2011年 | 9787篇 |
2010年 | 6466篇 |
2009年 | 6186篇 |
2008年 | 6554篇 |
2007年 | 6014篇 |
2006年 | 5498篇 |
2005年 | 4606篇 |
2004年 | 3414篇 |
2003年 | 2680篇 |
2002年 | 2428篇 |
2001年 | 1992篇 |
2000年 | 1771篇 |
1999年 | 2089篇 |
1998年 | 1856篇 |
1997年 | 1709篇 |
1996年 | 1813篇 |
1995年 | 1493篇 |
1994年 | 1452篇 |
1993年 | 1160篇 |
1992年 | 1059篇 |
1991年 | 984篇 |
1990年 | 788篇 |
1989年 | 564篇 |
1988年 | 461篇 |
1987年 | 379篇 |
1986年 | 371篇 |
1985年 | 318篇 |
1984年 | 240篇 |
1983年 | 154篇 |
1982年 | 139篇 |
1981年 | 106篇 |
1980年 | 76篇 |
1979年 | 43篇 |
1978年 | 34篇 |
1976年 | 36篇 |
1975年 | 33篇 |
1974年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
991.
Yan Yao Ruiling Wang Xucun Ma Pengsheng Song 《Journal of Thermal Analysis and Calorimetry》1995,45(1-2):117-130
Emf measurements were made on the cell without liquid junction: Li?ISE LiCl(m1), Li2SO4(m2) Ag/AgCl. The performances of the electrode pairs constructed in our laboratory were tested and exhibited near-Nernstian behavior. The mean activity coefficients of LiCl for the system Li+?Cl??SO 4 2? ?H2O have been investigated by the emf values at temperatures of 0, 15, 35°C and constant total ionic strengths of 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 and 5.0 mol·kg?1. The activity coefficients decrease with increasing temperature and the ionic strength fraction of Li2SO4 in the mixtures. The thermodynamic properties are interpreted by use of Harned's empirical equations and Pitzer's ion interaction approach including the contribution of higher order electrostatic terms. The experimental results obey Harned's rule and are described by using Pitzer equations satisfactorily. The activity coefficients of Li2SO4, the osmotic coefficients and the excess free energies of mixing for the system in the experimental temperature range were reported. 相似文献
992.
Wei-Ping Wang 《纯数学与应用数学通讯》1988,41(1):71-103
McKean's caricature of the nerve equation: is considered. The H in (1) is the Heaviside function. We prove the existence of multiple impulse solutions consisting of any finite number of pulses. These solutions are referred to as n-ple impulse solutions, where n is an arbitrary positive integer. 相似文献
993.
994.
Superstring theories provide an appropriate framework for studying the time variation of fundamental coupling constants. The present time variation of coupling constants in Superstring theories with currently favorable internal backgrounds critically depends on the shape of the potential for the size of internal space. If the potential is almost flat, as in perturbation theory to all orders, the present value of ¦/G¦ for Newton's gravitational constant is calculable and estimated to be 1×10–11±1yr–1, which is just at the edge of the present observational bound for/G. If the potential has a minimum with finite curvature due to unknown nonperturbative effects,/G will become unobservably small. The improvement of the measurement of/G of 1 or 2 orders of magnitude would discriminate between the two situations. Problems with the time variation of other coupling constants are also discussed.This essay received the fourth award from the Gravity Research Foundation for the year 1987-Ed. 相似文献
995.
996.
997.
998.
The bioaccumulation of gold at antheral cells from flower Datura innoxia is investigated by incorporating these plant cells into a carbon paste matrix. The resulting plant-modified electrode offers a preferential uptake of gold from dilute solutions. The voltammetric behavior of the surface-bound gold is examined under different preconcentration conditions. Scanning electron microscopy offers useful insights into the gold collection process. Convenient measurements of micromolar gold concentrations are possible, with effective self cleaning allowing the use of a single electrode in multiple determinations (R.S.D. of 4.8% for 50 repetitions). The sensitivity and selectivity enhancements associated with the preferential bioaccumulation process, and the convenient surface regeneration, offer the prospect of using the flower-biomass containing electrodes as sensors for gold. 相似文献
999.
Chemically modified electrodes prepared by treating the cobalt tetraphenylporphyrin modified glassy-carbon electrode at 750 degrees (HCME) are shown to catalyze the electrooxidation of hydrazine. The oxidation occurred at +0.63 V vs. Ag/AgCl (saturated potassium chloride) in pH 2.5 media. The catalytic response is evaluated with respect to solution pH, potential scan-rate, concentration dependence and flow-rate. The catalytic stability of the HCME is compared with that of the cobalt tetraphenylporphyrin adsorbed glassy-carbon electrode. The stability of the HCME was excellent in acidic solution and even in solutions containing organic solvent (50% CH(3)OH). When used as the sensing electrode in amperometric detection in flow-injection analysis, the HCME permitted sensitive detection of hydrazine at 0.5 V. The limit of detection was 0.1 ng. The linear range was from 50 ng to 2.4 mug. The method is very sensitive and selective. 相似文献
1000.