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淡水瓣鳃类鳃的扫描电镜观察 总被引:7,自引:0,他引:7
运用扫描电镜观察了圆顶珠蚌,褶纹冠蚌,背角无齿蚌,卵形尖嵴蚌及河蚬的鳃表面纤毛的分布,排列方式及细微形态结构,结果表明:这5种蚌的鳃表面都有前纤毛,侧纤毛和前侧纤毛。此餐,仅在河蚬鳃表面前纤毛和前侧纤毛之间,观察到一种新的纤毛结构-前触毛。这一结构可能在河蚬取食时起作用。 相似文献
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利用微宏观耦合方法模拟了棒状分子聚合物溶液在平板Couette流动中的复杂流变行为,其中微宏观模型通过非均匀Doi理论来描述.数值模拟中,应用有限体积方法耦合求解了介观尺度上的Smoluchowski方程和宏观尺度上的流场守恒方程.数值结果不仅得到了若干种典型的流动类型,而且还预测了另外两种新的复合瑕疵结构.数值试验表明:棒状分子聚合物的流变结构主要依赖于De数、分子相对尺度以及溶液浓度常数的取值;并且De数对分子指向矢的翻滚周期、随流取向角等微观特性也均有明显影响.
关键词:
棒状分子
聚合物溶液
微宏观模拟 相似文献
36.
It is a very complex and time-consuming process to simulate the nuclear reactor neutron spectrum from the reactor core to the export channel by applying a Monte Carlo program. This paper presents a new method to calculate the neutron spectrum by using the convolution technique which considers the channel transportation as a linear system and the transportation scattering as the response function. It also applies Monte Carlo Neutron and Photon Transport Code (MCNP) to simulate the response function numerically. With the application of convolution technique to calculate the spectrum distribution from the core to the channel, the process is then much more convenient only with the simple numerical integral numeration. This saves computer time and reduces some trouble in re-writing of the MCNP program. 相似文献
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Recently, a polynomial-based (k, n) steganography and authenticated image sharing (SAIS) scheme was proposed to share a secret image into n stego-images. At the same time, one can reconstruct a secret image with any k or more than k stego-images, but one cannot obtain any information about the secret from fewer than k stego-images. The beauty of a (k, n)-SAIS scheme is that it provides the threshold property (i.e., k is the threshold value), the steganography (i.e., stego-images look like cover images), and authentication (i.e., detection of manipulated stego-images). All existing SAIS schemes require parity bits for authentication. In this paper, we present a novel approach without needing parity bits. In addition, our (k, n)-SAIS scheme provides better visual quality and has higher detection ratio with respect to all previous (k, n)-SAIS schemes. 相似文献
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Formation and dissociation of protonated cytosine–cytosine base pairs in i-motifs by ab initio quantum chemical calculations 下载免费PDF全文
Formation and dissociation mechanisms of C-C+ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environment, a cytosine monomer is first protonated and then dimerized with an unprotonated cytosine monomer to form a C-C+ base pair; in an alkaline environment, a protonated cytosine dimer is first unprotonated and then dissociated into two cytosine monomers. In addition, the force for detaching a C-C+ base pair was found to be inversely proportional to the distance between the two cytosine monomers. These results provide a microscopic mechanism to qualitatively explain the experimentally observed reversible formation and dissociation of i-motifs. 相似文献
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Sandilya Garimella Xiaoyu Zhou Zheng Ouyang 《Journal of the American Society for Mass Spectrometry》2013,24(12):1890-1899
The understanding of the gas dynamics of the atmospheric pressure interface is very important for the development of mass spectrometry systems with high sensitivity. While the gas flows at high pressure (>1 Torr) and low pressure (<10–3 Torr) stages are relatively well understood and could be modeled using continuum and molecular flows, respectively, the theoretical modeling or numeric simulation of gas flow through the transition pressure stage (1 to 10–3 Torr) remains challenging. In this study, we used the direct simulation Monte Carlo (DMSC) method to develop the gas dynamic simulations for the continuous and discontinuous atmospheric pressure interfaces (API), with different focuses on the ion transfer by gas flows through a skimmer or directly from the atmospheric pressure to a vacuum stage, respectively. The impacts by the skimmer location in the continuous API and the temporal evolvement of the gas flow with a discontinuous API were characterized, which provide a solid base for the instrument design and performance improvement. Figure
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