全文获取类型
收费全文 | 165046篇 |
免费 | 7577篇 |
国内免费 | 10079篇 |
专业分类
化学 | 27879篇 |
晶体学 | 368篇 |
力学 | 7215篇 |
综合类 | 1308篇 |
数学 | 26022篇 |
物理学 | 23633篇 |
综合类 | 96277篇 |
出版年
2024年 | 260篇 |
2023年 | 1024篇 |
2022年 | 1808篇 |
2021年 | 2056篇 |
2020年 | 2188篇 |
2019年 | 2391篇 |
2018年 | 2055篇 |
2017年 | 2505篇 |
2016年 | 2817篇 |
2015年 | 3420篇 |
2014年 | 6109篇 |
2013年 | 7410篇 |
2012年 | 7565篇 |
2011年 | 8607篇 |
2010年 | 7259篇 |
2009年 | 8799篇 |
2008年 | 9501篇 |
2007年 | 11384篇 |
2006年 | 10839篇 |
2005年 | 10172篇 |
2004年 | 8696篇 |
2003年 | 8309篇 |
2002年 | 7237篇 |
2001年 | 6182篇 |
2000年 | 5589篇 |
1999年 | 4730篇 |
1998年 | 4067篇 |
1997年 | 3579篇 |
1996年 | 3289篇 |
1995年 | 2988篇 |
1994年 | 2849篇 |
1993年 | 2484篇 |
1992年 | 2322篇 |
1991年 | 2054篇 |
1990年 | 1797篇 |
1989年 | 1720篇 |
1988年 | 1449篇 |
1987年 | 921篇 |
1986年 | 654篇 |
1985年 | 526篇 |
1984年 | 458篇 |
1983年 | 215篇 |
1982年 | 365篇 |
1981年 | 410篇 |
1980年 | 314篇 |
1979年 | 296篇 |
1978年 | 224篇 |
1977年 | 208篇 |
1976年 | 164篇 |
1974年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as
far as the calibration of a satellite altimeter is concerned. 相似文献
192.
Kayll Lake 《General Relativity and Gravitation》2004,36(5):1159-1169
The norms associated with the gradients of the two non-differential invariants of the Kerr vacuum are examined. Whereas both locally single out the horizons, their global behavior is more interesting. Both reflect the background angular momentum as the volume of space allowing a timelike gradient decreases with increasing angular momentum becoming zero in the degenerate and naked cases. These results extend directly to the Kerr-Newman geometry. 相似文献
193.
Semra Harmandar 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(4):395-407
A radiation code based on method of lines solution of discrete ordinates method for radiative heat transfer in axisymmetric cylindrical enclosures containing absorbing-emitting medium was developed and tested for predictive accuracy by applying it to (i) test problems with black and grey walls (ii) a gas turbine combustor simulator enclosing a non-homogeneous absorbing-emitting medium and benchmarking its steady-state predictions against exact solutions and measurements. Comparisons show that it provides accurate solutions for radiative heat fluxes and can be used with confidence in conjunction with CFD codes based on the same approach. 相似文献
194.
195.
通过用毛细管测量纯水表面张力系数实验,得到管内径d与接触角θ的相对误差之间的关系曲线,由此说明实验测得的表面张力系数α和理论公式相比呈现一定的偏差,并简单地讨论了实验的理想状态与实际情况的差别. 相似文献
196.
从现有的PCDFs分子的正辛醇 /水分配系数 (logKow)实验数据出发 ,建立定量结构 性质关系方程(QSPR) .采用G98W程序包中的PM3方法对 13 5个多氯代二苯并呋喃 (PCDFs)分子和二苯并呋喃进行了优化计算 ,作业命令为 #pPM3optfreqscf(conver =9) ,以计算所得的分子轨道能量、碳原子电荷作为PCDFs分子结构描述符 ,运用多元线性回归技术建立了PCDFs的logKow与分子结构描述符的四元方程 ,最优相关系数为 0 .95 0 7,标准偏差为 0 .173 7,经检验该模型的稳健性好 ,并对未有实验数据的 85个PCDFs的logKow进行预测 相似文献
197.
198.
S. Mancini D. Vitali V. Giovannetti P. Tombesi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):417-422
We show that the optomechanical coupling between an optical cavity mode and two movable cavity mirrors is able to entangle
two different macroscopic oscillation modes of the mirrors. This continuous variable entanglement is maintained by the light
bouncing between the mirrors and is robust against thermal noise. In fact, it could be experimentally demonstrated using present
technology.
Received 2 September 2002 / Received in final form 10 October 2002 Published online 7 January 2003 相似文献
199.
Ab initio calculations showed that the tetrachlorodibenzo-para-dioxin radical cations (TCDD RCs) with a planar structure have two steady states with asymmetric dioxin cycles. The activation barriers between these states are up to 2 kcal/mole, so that the RCs may be regarded as being structurally nonrigid within the dioxin cycle. The 2,3,7,8-TCDD RC is more stable than the 1,4,6,9-TCDD RC, the energy difference being 5.2 kcal/mole. The adiabatic ionization potential of 2,3,7,8-TCDD (7.54 eV) is 0.1 eV smaller than the corresponding potential of 1,4,6,9-TCDD. These factors account for the increased hemoproteide affinity and hence increased biological activity of 2,3,7,8-TCDD. 相似文献
200.
Grishin D. F. Semyonycheva L. L. Telegina E. V. Smirnov A. S. Nevodchikov V. I. 《Russian Chemical Bulletin》2003,52(2):505-507
Organometallic compounds Cp2TiCl2, (EtC5H4)2NbCl2, and (PriC5H4)2WCl2 were assessed as additives that control polymer chain growth in the polymerization of methyl methacrylate. In the presence of compounds mentioned in amounts comparable with that of the initiator, a uniform process with no gel-effect occured and respective linear increase in the molecular weight of the polymer up to high degrees of the monomer conversion was observed. 相似文献