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951.
沉积物中石英ESR测年功率饱和效应的初步研究 总被引:2,自引:0,他引:2
介绍了几组沉积物中石英ESR功率饱和效应的基础实验情况,认为在用石英进行ESR测年时,微波功率的选择是一个重要参数,它直接影响累积剂量(AD)的求取,从而严重影响测年结果。在某些特定的地质环境下(如黄土,海洋沉积物),采用比较高的微波功率,可从沉积物石英的E'心得到较老沉积物(大于50万年)可信的ESR年代。 相似文献
952.
介绍一种新型大功率氧化物导电陶瓷.该陶瓷是以六角密堆(HCP)结构的ZnO为主要原料,添加少量杂质,采用电子陶瓷工艺研制而成.研究了陶瓷材料的差热分析(DTA)及扫描电子显微结构.测量了瓷体的电阻率. 相似文献
953.
采用有限元方法分析了激光清洗过程中基片表面的温度分布,研究了激光清洗过程中清洗阈值和损伤阈值存在的原因,推导出使用波长为308nm,脉宽为28ns的准分子激光清洗硅片表面油脂的清洗阈值和损伤阈值,并进行了实验验证,其理论清洗阈值与实验结果是符合的 相似文献
954.
955.
S. K. Andrukhovich A. V. Berestov B. A. Martsynkevich A. M. Khil'manovich N. Antovich 《Journal of Applied Spectroscopy》1998,65(2):290-296
In the paper we describe the capabilities of the multidimensional (multidetector) spectroscopy of photon cascades. Attention
is paid to a considerable increase in the resolution of multidetector spectrometers compared to one-detector spectrometers.
We give a derivation of the radiation intensity detection limit, which relates all the basic characteristics of a multidetector
spectrometer, and present examples of calculation of spectrometer characteristics.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 278–283, March–April, 1998. 相似文献
956.
Kwang-Ting Liu 《中国化学会会志》1995,42(4):607-615
New YBnX scales of solvent ionizing power are developed and considered superior to Yx scales for benzylic bromides, chlorides, p-nitrobenzoates and tosylates in Grunwald-Winstein type correlation analysis of solvolytic reactivities. The YBnX values, with addition and revision, are summarized. Evidence for nucleophilic solvent intervention in the solvolysis transition state for secondary and tertiary benzylic substrates is given. The advantages of employing this tool to understand solvolysis mechanisms are discussed. 相似文献
957.
R. Nieva G. S. Christensen M. E. El-Hawary 《Journal of Optimization Theory and Applications》1981,35(2):261-275
This paper considers the problem of short-term optimal operation of nuclear-hydro-thermal electric power systems. The solution is obtained by use of a functional analytic optimization technique that employs the minimum norm formulation.A power system with an arbitrary number of generating stations is considered. The limited flexibility exhibited by the thermal nuclear reactors, when operating in a load-following mode, is accounted for by means of a model of the xenon concentration in their cores. The nonlinear effects induced by trapezoidal water reservoirs and the time delay of the water flow between upstream and downstream hydroplants is taken into consideration as well.A two-level iterative scheme of the feasible type is proposed for implementing the optimal solution.This work was supported in part by the National Research Council of Canada, Grant No. A-4146. 相似文献
958.
The measurement in thermal equilibrium of the vacancy contribution to the residual resistivity of metals has posed certain
difficulties. The recent experiment of Celasco and co-workers represents a new, powerful approach to this problem, via the
measurement of the power spectrum of the voltage noise generated by resistivity fluctuations. The latter originate in vacancy
number fluctuations. We develop a theory for the power spectrum, incorporating three basic features. Vacancies can be annihilated
in the material and they diffuse. Grain boundaries act as sources and sinks for vacancies. Both annihilation (a form of reaction)
and diffusion are noisy processes. We therefore set up and solve a reactive-diffusive stochastic equation for the instantaneous
density, with appropriatefinite boundary conditions. Assuming for simplicity that the grains are spherical, the power spectrum is evaluated exactly, in closed
form. A detailed comparison with experiment is made. The physical origins of different time scales in the problem and the
consequent frequency regimes in the power spectrum are analysed. Recognising the very general applicability of our theory,
we also mention possible applications to other problems. 相似文献
959.
Michael D. Perlman 《Journal of multivariate analysis》1974,4(1):22-30
It is shown that for the MANOVA problem the power function of the test based on the trace of a multivariate beta matrix is monotonically increasing in each noncentrality parameter provided that the cutoff point is not too large. This result is also true for the problem of testing independence of two sets of variates. 相似文献
960.
用二次曲面方法求解多机系统故障临界清除时间 总被引:2,自引:0,他引:2
为提高多机系统故障临界切除时间的求解精度和保证确定的误差方向,该文在主导不稳定平衡点处利用空间二次曲面来近似局部稳定域边界,根据持续故障轨线与空间二次曲面的交点来确定系统的故障临界清除时间.仿真结果表明,该方法具有固定的误差方向和较高的计算精度,误差基本能控制在10%以内,能够对系统的故障严重程度进行排序.另外,在网络中发生故障时计算性能可能没有切平面方法好,这方面的理论根据还需进一步的研究和探索. 相似文献