全文获取类型
收费全文 | 3773篇 |
免费 | 113篇 |
国内免费 | 21篇 |
专业分类
化学 | 2785篇 |
晶体学 | 31篇 |
力学 | 47篇 |
数学 | 245篇 |
物理学 | 799篇 |
出版年
2022年 | 20篇 |
2021年 | 27篇 |
2020年 | 45篇 |
2019年 | 40篇 |
2018年 | 36篇 |
2017年 | 36篇 |
2016年 | 68篇 |
2015年 | 57篇 |
2014年 | 80篇 |
2013年 | 172篇 |
2012年 | 172篇 |
2011年 | 209篇 |
2010年 | 94篇 |
2009年 | 111篇 |
2008年 | 211篇 |
2007年 | 230篇 |
2006年 | 221篇 |
2005年 | 219篇 |
2004年 | 158篇 |
2003年 | 159篇 |
2002年 | 143篇 |
2001年 | 90篇 |
2000年 | 79篇 |
1999年 | 67篇 |
1998年 | 45篇 |
1997年 | 33篇 |
1996年 | 42篇 |
1995年 | 35篇 |
1994年 | 36篇 |
1993年 | 43篇 |
1992年 | 58篇 |
1991年 | 56篇 |
1990年 | 38篇 |
1989年 | 41篇 |
1988年 | 45篇 |
1987年 | 43篇 |
1986年 | 41篇 |
1985年 | 67篇 |
1984年 | 52篇 |
1983年 | 51篇 |
1982年 | 47篇 |
1981年 | 39篇 |
1980年 | 40篇 |
1979年 | 47篇 |
1978年 | 28篇 |
1977年 | 28篇 |
1976年 | 29篇 |
1975年 | 25篇 |
1974年 | 20篇 |
1973年 | 24篇 |
排序方式: 共有3907条查询结果,搜索用时 15 毫秒
991.
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to investigate the distribution of elements, Na, Mg, Al, K, and Ca, and lignin, in the contiguous growth rings including the sapwood/heartwood boundary in Hinoki cypress (Chamaecyparis obtusa). Lignin was distributed almost uniformly from sapwood to heartwood. The concentrations of most of the elements showed a drastic increase or decrease in the transition zone between sapwood and heartwood. The ToF-SIMS mapping analysis showed that most of the elements predominantly localized in the ray parenchyma cells in the inner transition zone and heartwood, while the elements showed no localization and distributed almost uniformly in the outer transition zone near sapwood. The result suggests that the ray parenchyma cells play a role in behaviors of elements during the transition from sapwood to heartwood. 相似文献
992.
G. Saito 《Monatshefte für Chemie / Chemical Monthly》1936,67(1):141-158
Ohne Zusammenfassung 相似文献
993.
994.
The 1 H NMR assignment of oligomeric grafts of maleic anhydride (MA)‐grafted polyolefin (PO), MA‐g‐PO hereafter, was experimentally demonstrated for the first time using NMR spectroscopy. 13 C DEPT, 1 H‐1 H DQF‐COSY, and 1 H T2‐edited spectroscopy of MA‐g‐PO proved that peaks of the intermediate methine protons of succinic anhydride oligomeric grafts, which are nearly tetrameric, are observed at 2.5–3.5 ppm and show broadening. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
995.
Heat capacity measurements have been made on ANBC(18) at temperatures from 8 to 490 K by adiabatic calorimetry. All known phases were detected. The temperatures, enthalpies and entropies of transition were determined for the phase transitions observed. On the basis of the entropy of transition to the SmC phase from the D or cubic phases, it is pointed out that the D phase of ANBC and the cubic phase of BABH might be identical in nature. It is shown that the arrangement of 'molecular' cores has a higher degree of order in the isotropic (D and cubic) phases than in the SmC phase, whereas the terminal alkoxy chains are more disordered in the isotropic phases than in the SmC phase. The degrees of disorder in the D and cubic phases relative to the SmC phase are very similar in terms of the entropy of transition per methylene group. The inverted phase sequence in ANBC (SmC D on heating) and BABH (cubic SmC) can be accounted for in terms of the competing roles in the entropy between the molecular core and the chains. 相似文献
996.
A novel guanosine derivative with a photoswitching property, 8-styryl-2′-deoxyguanosine was synthesized, and showed very rapid and efficient reversible E-Z photoisomerization upon illumination at specific wavelength. In addition, E-Z photoisomerization can be iteratively performed by alternate illumination with monochroic 254 nm and 370 nm light without any side reactions. 相似文献
997.
Shuji Morikawa Katsunori Saito Taihei Takeuchi Hiroshi Umemura 《Mathematics in Computer Science》2010,4(2-3):151-167
In discrete Burgers’ equation, time is discretized but space remains continuous. Reduction modulo 2 of discrete Burgers’ equation discretizes also space. This dynamical system generates an elegant pattern known since long time ago. We also propose to show that the Galois groups of particular solutions of Burgers’ equation are abelian. It would imply that the dynamical systems are integrable. 相似文献
998.
999.
Matsuoka H Sotoyama H Saito M Oh KB Horikiri S 《Bioelectrochemistry and bioenergetics (Lausanne, Switzerland)》1999,49(1):65-72
A pulsing electric signal (pulse width 10 s) was applied to a single cell of cultured tobacco, line BY-2, by inserting a multifunctional microelectrode (MME) into the cell. The electric voltage (V(ET)) was loaded between the electrode terminals of the MME and the reference electrode situated in the extracellular medium. Since the electrical impedance of the MME was as large as that of the cell membrane, the effective potential acting across the cell membrane (V(CMP)) should be only some portion of V(ET). The MME enabled simultaneous measurement of V(ET) and V(CMP). When V(ET) was varied from 0 to -1 V, V(CMP) changed linearly in proportion to V(ET). When V(ET) variation range was enlarged (from 0 to -2 V), V(CMP) changing pattern became a declined curve. When V(ET) variation range was further enlarged (from 0 to -5 V), the V(CMP) changing pattern showed a saturation curve. Under this condition, the cell division potentiality decreased accordingly. Based on these results, the feasibility of V(CMP) as an indicator of the effective intensity of an electric stress signal is discussed. In the present case of a BY-2 cell, a proper intensity of V(CMP) that could cause an appreciable stress and not a lethal signal was estimated as -250 mV. 相似文献
1000.
We investigate the dynamics of probability distributions of an initially one-mode coherent field interacting with a four-state molecular system, which is a single magnet with a tunneling across an anisotropic barrier, using a numerically exact approach. The population for each state, the phase properties of and
, and
), the entropy are calculated for a model system. The model predicts that the molecule and field become asymptotically disentangled at half of the revival time, and that optical Schrödinger-cat and magnetic Schrödinger-cat states are generated.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Areas “Near-field Nano-optics” Project, sponsored by Japan Society for the Promotion of Science. 相似文献