全文获取类型
收费全文 | 104173篇 |
免费 | 16642篇 |
国内免费 | 11835篇 |
专业分类
化学 | 72670篇 |
晶体学 | 1135篇 |
力学 | 5895篇 |
综合类 | 666篇 |
数学 | 12640篇 |
物理学 | 39644篇 |
出版年
2024年 | 351篇 |
2023年 | 2068篇 |
2022年 | 3672篇 |
2021年 | 3956篇 |
2020年 | 4178篇 |
2019年 | 3968篇 |
2018年 | 3725篇 |
2017年 | 3334篇 |
2016年 | 5023篇 |
2015年 | 4934篇 |
2014年 | 6059篇 |
2013年 | 7788篇 |
2012年 | 9293篇 |
2011年 | 9480篇 |
2010年 | 6628篇 |
2009年 | 6362篇 |
2008年 | 6685篇 |
2007年 | 5970篇 |
2006年 | 5586篇 |
2005年 | 4663篇 |
2004年 | 3653篇 |
2003年 | 2934篇 |
2002年 | 2664篇 |
2001年 | 2231篇 |
2000年 | 1947篇 |
1999年 | 2050篇 |
1998年 | 1735篇 |
1997年 | 1561篇 |
1996年 | 1556篇 |
1995年 | 1366篇 |
1994年 | 1239篇 |
1993年 | 1004篇 |
1992年 | 902篇 |
1991年 | 776篇 |
1990年 | 653篇 |
1989年 | 503篇 |
1988年 | 378篇 |
1987年 | 338篇 |
1986年 | 335篇 |
1985年 | 264篇 |
1984年 | 191篇 |
1983年 | 153篇 |
1982年 | 129篇 |
1981年 | 81篇 |
1980年 | 60篇 |
1979年 | 27篇 |
1978年 | 22篇 |
1976年 | 23篇 |
1975年 | 22篇 |
1957年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
在很高的温度和适宜的生长条件下,分别采用熔盐籽晶法和高温引上法生长了高质量的YAP、NAB、KTP、LN、BBO、SBN等多元氧化物单晶,它们具有优良的物理化学性能,严格的化学比,固定的组成与结构以及较好的化学均匀性和电子束轰击下的稳定性。广泛地用于激光和非线性光学领域。我们选用这些晶体为原材料研制电子探针定量分析的标准样品。经过测量和标定,这些单晶标样符合中华人民共和国国家标准GB 4930-85(电子探针显微分析标准样品通用技术条件)的规定。含有稀土元素的标样如NAB和YAP能发出绿色荧光,是电子显微术中理想的阴极发光材料。 相似文献
84.
A novel photothermal phase-shift spectroscopy configuration based on the retro-reflected beam interference has been developed and its operational principle is described. The weak absorption measurement ability of this technique is experimentally proven with a water/ethanol solution of standard Pyronine G dye and the limit of detection is found to be 1.8 x 10(-6) absorbance. Potential applications of the technique are discussed. 相似文献
85.
Li HZ 《Physical review letters》1987,58(6):539-542
86.
We establish some inequalities connecting natural parameters of a partial order P. For example, if every interval [a,b] contains at most maximal chains, if some antichain has cardinality v, and if there are 1 chains whose union is cofinal and coinitial in P, then the chain decomposition number for P is 1v (Theorem 2.2), and the inequality is sharp in a certain sense (Section 3).This paper was written while the authors were visitors at the Laboratoire d'algèbre ordinale, Département de Mathématiques, Université Claude Bernard, Lyon 1, France.Research supported by NSERC grant # A5198. 相似文献
87.
It is proved for an arbitrary commutative ring A with identity and any integer n3 that if H is a subgroup of GLn(A) normalized by E
n(A,q), then there is an ideal of A such that E
n(A,) H GL
n
(A, (:q40).Furthermore, is uniquely determined up to a certain equivalence relation on the set of ideals of A. The result extends a theorem of Bak, by removing a stability condition he uses on A. 相似文献
88.
89.
A low density, low temperature plasma formed by two merged beams of electrons and ions at near zero relative velocity is studied by solving a set of time-dependent rate equations. In particular, we investigate the role played by the radiative recombination (RR) and three-body recombination (TBR) on the population of excited states during the initial stage of plasma rearrangement and relaxation. It is found in the case of hydrogenic plasmas that low-lying states are filled predominantly by RR, while high Rydberg states are populated mainly by TBR. As the plasma further relaxes, the collisional excitation and de-excitation, and radiative decays become important, filling the median excited states. The dependence of the TBR and RR rates on ionic chargeZ is discussed to extend the result to plasmas of highZ ions. 相似文献
90.
Odd/even effect in the chain length on the enthalpy of micellization of gemini surfactants in aqueous solution 总被引:1,自引:0,他引:1
Li Y Li P Wang J Wang Y Yan H Thomas RK 《Langmuir : the ACS journal of surfaces and colloids》2005,21(15):6703-6706
The micellization properties of cationic symmetric gemini surfactants, [CmH(2m+1)(CH3)2N(CH2)6N(CH3)2CmH(2m+1)]Br2 (designated as CmC6CmBr2, with m = 7, 8, 9, 10, 11, 12, and 16), has been investigated by isothermal titration microcalorimetry. The critical micelle concentration (CMC) and enthalpy of micellization (DeltaHmic) were determined from calorimetric titration curves. The linear decreasing of log CMC with increasing the length of the hydrophobic chain is consistent with an increase in the hydrophobicity of the alkyl chain. Interestingly, with increasing the length of the alkyl chain, the DeltaHmic values of the surfactants with even numbered alkyl chains vary from endothermic to exothermic, whereas the DeltaHmic values of the surfactants with odd numbered alkyl chains are all endothermic and tend to become more endothermic. The pronounced even/odd effect in DeltaHmic is discussed with respect to the "donor-acceptor" interaction. 相似文献