全文获取类型
收费全文 | 115113篇 |
免费 | 2911篇 |
国内免费 | 1418篇 |
专业分类
化学 | 50764篇 |
晶体学 | 1087篇 |
力学 | 7646篇 |
综合类 | 110篇 |
数学 | 36536篇 |
物理学 | 23299篇 |
出版年
2023年 | 417篇 |
2022年 | 409篇 |
2021年 | 619篇 |
2020年 | 841篇 |
2019年 | 795篇 |
2018年 | 11020篇 |
2017年 | 10845篇 |
2016年 | 7491篇 |
2015年 | 2165篇 |
2014年 | 1789篇 |
2013年 | 2991篇 |
2012年 | 6684篇 |
2011年 | 13273篇 |
2010年 | 7332篇 |
2009年 | 7403篇 |
2008年 | 8918篇 |
2007年 | 10930篇 |
2006年 | 2328篇 |
2005年 | 3121篇 |
2004年 | 3036篇 |
2003年 | 3178篇 |
2002年 | 2157篇 |
2001年 | 1145篇 |
2000年 | 1000篇 |
1999年 | 763篇 |
1998年 | 616篇 |
1997年 | 465篇 |
1996年 | 653篇 |
1995年 | 431篇 |
1994年 | 385篇 |
1993年 | 444篇 |
1992年 | 366篇 |
1991年 | 296篇 |
1990年 | 237篇 |
1989年 | 235篇 |
1988年 | 220篇 |
1987年 | 213篇 |
1986年 | 217篇 |
1985年 | 264篇 |
1984年 | 208篇 |
1983年 | 176篇 |
1982年 | 170篇 |
1981年 | 153篇 |
1980年 | 135篇 |
1979年 | 149篇 |
1978年 | 135篇 |
1977年 | 107篇 |
1976年 | 110篇 |
1973年 | 119篇 |
1968年 | 103篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
V. A. Petržílka 《Czechoslovak Journal of Physics》1989,39(12):1372-1377
The amplification of lower hybrid (LH) driven current of various profiles has been found. The results strongly depend on the plasma temperature profile, on the LH current profile, and on the magnitude of the particle diffusion flux.This work was started during the visit of the author in the I. V. Kurchatov Institute of Atomic Energy, Moscow. The author thanks IAE for hospitality, and V. Parail, G. V. Pereverzev, A. Smoljakov and R. Klíma for many useful and critical discussions. 相似文献
922.
We discuss productions of scalar gluonium candidates in the radiativeJ/ decays. The branching ratios of such productions are estimated on the basis of the Euler-Heisenberg effective Lagrangian for gluon-photon couplings. We mention that these estimates cannot be expected to be accurate to better than within a factor 2. We show that the radiativeJ/ decays probably invalidate gluoniumgg interpretation of the GAMS meson F0(1590) and a narrow 0++ stateS lying below 1 GeV. However, a possible wide scalar effective gluonium candidate(920) is shown not to be excluded by the data on the decayJ/. We also find that the experimental data about radiativeJ/ decays presumably agree with a recently suggested interpretation of F0(1590) as being approximately a half-and-half mixture of pure 0++ gluoniumgg andSU(3)f singlet quarkoniumq¯q states. 相似文献
923.
The tensor product of two supersingleton representations
n of the Lie superalgebraosp (1, 2n) is studied forn2. The main results are as follows: (a) anticommutators and commutators of the odd generators in
n
n form a skew-symmetric representation of the Lie algebrau(n, n); (b) simple explicit form of all irreducible components of
n
n, which are labelled by a single parameterJ=0, 1, ..., has been found. Each of them is a*-representation ofosp (1, 2n) for which assertion (a) is valid. The dimension of its vacuum subspace equals
, i.e., the nondegenerate vacuum occurs for J=0 only. Basic property of this family of irreducible*-representations of osp(1, 2n) are analogous to those of massless representations of osp(1, 4).Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday. 相似文献
924.
The generation of ozone under homogeneous conditions is described by a system of kinetic equations. We supposed a certain time dependence of electric field intensity inside a discharge gap. We computed the dependence of efficiency of the ozone generation on both the width and the maximum intensity of electric pulse. 相似文献
925.
CuO—ZnO/Al2O3—TiO2催化剂中TiO2的结构和电子效应 总被引:6,自引:0,他引:6
采用XPS,XRD,TPR,TPD和指标反应等方法研究了TiO_2在负载型CuO-ZnO/Al_2O_3-TiO_2催化剂中所起的作用.发现TiO_2起双重作用,即结构效应和电子效应,TiO_2的结构效应主要表现为它改善了CuO在载体上的分布.TiO_2的电子效应表现为它对Cu~0具有吸电子的作用,从而削弱了Cu和S之间的吸附力,使S容易脱除.另外,部分还原形成的Ti~(3+)具有促进CuS中的Cu~(2+)还原为Cu~0的能力,TiO_2的上述效应的综合结果使催化剂的抗硫中毒性能大大增强. 相似文献
926.
食物中游离态二价铁及游离态三价铁的测定 总被引:4,自引:0,他引:4
人体必需的微量元素铁的生物有效性与铁的离子价态有关。为了解食物中游离态二价铁与游离态三价铁的含量,及其在总铁中的比例,用去离子水提取食物中的游离态铁,分别用邻菲啉-氟化铵体系和硫氰酸钾体系分光光度法测定游离态二价铁与三价铁离子,结果发现动物性食物中游离态二价铁离子明显高于游离态三价铁离子,而植物性食物却相反。紫菜中游离态二价铁离子的含量是传统观念中补铁食物菠菜的25倍、猪肝的14倍,是较为理想的补铁食物。各种食物的游离态Fe2+与Fe3+之和,约占总铁的7%~93%,说明除了游离态的Fe2+和Fe3+外,尚有其他形态的铁存在,并且动物性食物较多。 相似文献
927.
XinMeiZHENG YanXingQI XiaoMingZHANG JiShuanSUO 《中国化学快报》2004,15(6):655-658
Jacobsen‘s catalyst was immobilized onto SBA-15 by multi-step grafting, and this heterogenized catalyst exhibited comparable catalytic performance with the corresponding homogeneous counterpart for the epoxidation of alkenes, and the catalyst could be recycled effectively several times. 相似文献
928.
M. Solache-Ríos I. García-Sosa S. Sosa-Reyes 《Journal of Radioanalytical and Nuclear Chemistry》1998,237(1-2):151-153
The sorption of cesium was studied on zeolites ZSM-5 and Y. It was found that the sorption is much higher on zeolite Y than
in ZSM-5 and it depends on the crystalline network of the zeolite. It was found as well that the main uptake mechanism involved
in both zeolites for cesium was ion exchange. 相似文献
929.
G. Ferro-Flores F. De M. Ramírez M.G. Martínez-mendoza C. Arteaga de Murphy M. Pedraza-lópez L. García-salinas 《Journal of Radioanalytical and Nuclear Chemistry》2002,251(1):7-13
Lanreotide peptide was labeled with 153Sm-H1ETA and 188Re-MAG3 in order to evaluate whether or not their conjugation to the peptide produce significant differences of the in vitro lipophilicity with respect to the 188Re-lanreotide prepared by the direct labeling method (highly lipophilic). The differences of lipophilicity between the complexes, were evaluated using a reverse phase HPLC system. The measured lipophilicity of 153Sm-H1ETA-lanreotide, 188Re-MAG3-lanreotide and 188Re-lanreotide was taken to be the capacity factor [k" = (t
R-t
0)/t
0 where t
R is the retention time and t
0 is the dead time] for each of the complexes under identical chromatography conditions. Results showed that the in vitro lipophilicity decreased in the order 188Re-lanreotide (direct labeling), 188Re-MAG3-lanreotide and 153Sm-H1ETA-lanreotide. Since the last one has a capacity factor (k") similar to that of 188Re-MAG3, some renal elimination for 153Sm-H1ETA-lanreotide could be expected, which probably would reduce the unnecessary radiation dose to normal tissues. 相似文献
930.
遗传算法是一种模仿自然进化进程的新颖的启发式优化方法。通过它,人们可以在计算机上对所需的各种问题实施进化操作,最终产生理想的结果。遗传算法现已被广泛于计算机辅助设计、工程设计、系统模拟等领域并取得了极大的成功。本文拟对遗传算法在对大、中、小分子的构象搜寻中的应用作一较全面的综述。 相似文献