全文获取类型
收费全文 | 9109篇 |
免费 | 138篇 |
国内免费 | 37篇 |
专业分类
化学 | 5609篇 |
晶体学 | 124篇 |
力学 | 283篇 |
数学 | 1028篇 |
物理学 | 2240篇 |
出版年
2021年 | 50篇 |
2020年 | 79篇 |
2019年 | 84篇 |
2017年 | 50篇 |
2016年 | 98篇 |
2015年 | 97篇 |
2014年 | 130篇 |
2013年 | 407篇 |
2012年 | 323篇 |
2011年 | 385篇 |
2010年 | 204篇 |
2009年 | 222篇 |
2008年 | 383篇 |
2007年 | 398篇 |
2006年 | 403篇 |
2005年 | 364篇 |
2004年 | 325篇 |
2003年 | 292篇 |
2002年 | 283篇 |
2001年 | 193篇 |
2000年 | 208篇 |
1999年 | 106篇 |
1998年 | 98篇 |
1997年 | 102篇 |
1996年 | 140篇 |
1995年 | 116篇 |
1994年 | 167篇 |
1993年 | 179篇 |
1992年 | 166篇 |
1991年 | 120篇 |
1990年 | 119篇 |
1989年 | 129篇 |
1988年 | 99篇 |
1987年 | 121篇 |
1986年 | 111篇 |
1985年 | 189篇 |
1984年 | 155篇 |
1983年 | 101篇 |
1982年 | 127篇 |
1981年 | 121篇 |
1980年 | 137篇 |
1979年 | 133篇 |
1978年 | 131篇 |
1977年 | 115篇 |
1976年 | 130篇 |
1975年 | 115篇 |
1974年 | 132篇 |
1973年 | 128篇 |
1972年 | 55篇 |
1971年 | 64篇 |
排序方式: 共有9284条查询结果,搜索用时 31 毫秒
11.
12.
This paper examines the effect of infinitesimal functional variations in a rigid rotor He-HF potential surface on several different types of observables: inelastic cross sections, rate constants, and rotational energy level populations. The dynamics and kinetic observables studied were found to be sensitive to a large number of Legendre components of the potential with the region of highest sensitivity dependent upon the energy or temperature as well as the states related by the individual observable. Sensitivity to the entire surface tends to show a large degree of structure due to competition among sensitivities to the individual potential components. Significant information loss has been observed in the transition from microscopic to macroscopic observables. 相似文献
13.
Due to the hot, arid nature of its bordering lands, seawater in the Arabian Gulf can have significant evaporation rates leading to hypersaline conditions. If additional desalination plants were to operate along its coast, then the extraction of desalinated water and returned brine waste stream into the Gulf would increase the salinity. This paper uses a tidally and cross-sectionally averaged mathematical model that reveals multiplicative dependence of the salinity on factors associated with river flow, evaporation rates and each of the desalination plants. Present-day desalinated water production rates are in the linear regime, but hypersalinity has exponential sensitivity to the position and volumetric rate of desalinated water extraction. 相似文献
14.
The anti-Parkinson’s agent SIB-1508Y was prepared in six steps from (S)-nicotine in 20% overall yield. The strategy involves a regioselective formylation at C-5 of a 1,4-dihydronicotine intermediate. 相似文献
15.
In previous work, we considered the representation of human decision-making processes in closed-form simulation models of conflict. An important element of this representation is the rapid planning process that embodies the processing of information for situation assessment to support a course of action decision (eg in a military headquarters). The application of this work is in support of operational analysis models for defence procurement and balance of investment. This paper describes the application of non-linear multi-attribute utility theory in conflict scenarios in order to extend the representation of the rapid planning process to account for a wider set of subjective attributes of the decision-maker. The results show, through examination of experimental data, that decision-making can be modelled through a particular class of utility functions. These utilities embody a geometry which allows us to classify the types of decision being made when there are conflicting objectives and when decision-makers adopt very different and subjective appraisals of constraints and beliefs in outcome. The experimental results help to demonstrate that the subjective nature of the situation assessment, and the personality, training, experience and history of the decision-maker are central to the functional representations. This paper presents a way to capture this deeper representation of human decision-making in a way that is potentially useful for quantitative modelling using the rapid planning process as a basis. 相似文献
16.
R. Pinna F.J.M. Rutten E.F. Smith M.R. Willis M.R.S. McCoustra 《Applied Surface Science》2006,252(19):6672-6675
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and polarisation-modulation reflection-absorption infrared spectroscopy (PM-RAIRS) have been used to monitor the surface synthesis of self-assembled aromatic π-conjugated molecular wires on gold substrates as a step towards a novel structure for organic electroluminescent devices (OLEDs). The wires have been synthesised using a series of Schiff's base coupling reactions in solution on a self-assembled monolayer of an aromatic thiolate anchor. ToF-SIMS and PM-RAIRS measurements have demonstrated that: (i) the anchor molecules self-assemble at the gold surface, (ii) the anchor molecules selectively react through imino coupling reactions with additional wire units with high efficiency and (iii) the wire-like structure is predominantly orientated normal to the surface. 相似文献
17.
18.
19.
Michael Smith 《Angewandte Chemie (International ed. in English)》1994,33(12):1214-1221
Most of the significant work has been summarized in a number of reviews and articles. In these there was, of necessity, a good deal of simplification and omission of detail…. With the passage of time, even I find myself accepting such simplified accounts. F Sanger[1] 相似文献
20.
Pure adaptive search in global optimization 总被引:10,自引:0,他引:10
Pure adaptive seach iteratively constructs a sequence of interior points uniformly distributed within the corresponding sequence of nested improving regions of the feasible space. That is, at any iteration, the next point in the sequence is uniformly distributed over the region of feasible space containing all points that are strictly superior in value to the previous points in the sequence. The complexity of this algorithm is measured by the expected number of iterations required to achieve a given accuracy of solution. We show that for global mathematical programs satisfying the Lipschitz condition, its complexity increases at mostlinearly in the dimension of the problem.This work was supported in part by NATO grant 0119/89. 相似文献