全文获取类型
收费全文 | 15091篇 |
免费 | 2633篇 |
国内免费 | 1859篇 |
专业分类
化学 | 11314篇 |
晶体学 | 216篇 |
力学 | 785篇 |
综合类 | 117篇 |
数学 | 1422篇 |
物理学 | 5729篇 |
出版年
2024年 | 12篇 |
2023年 | 270篇 |
2022年 | 336篇 |
2021年 | 467篇 |
2020年 | 639篇 |
2019年 | 649篇 |
2018年 | 566篇 |
2017年 | 494篇 |
2016年 | 765篇 |
2015年 | 734篇 |
2014年 | 853篇 |
2013年 | 1206篇 |
2012年 | 1390篇 |
2011年 | 1383篇 |
2010年 | 965篇 |
2009年 | 959篇 |
2008年 | 1079篇 |
2007年 | 967篇 |
2006年 | 869篇 |
2005年 | 762篇 |
2004年 | 616篇 |
2003年 | 518篇 |
2002年 | 523篇 |
2001年 | 379篇 |
2000年 | 270篇 |
1999年 | 283篇 |
1998年 | 230篇 |
1997年 | 212篇 |
1996年 | 194篇 |
1995年 | 163篇 |
1994年 | 135篇 |
1993年 | 108篇 |
1992年 | 106篇 |
1991年 | 102篇 |
1990年 | 68篇 |
1989年 | 54篇 |
1988年 | 39篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 36篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
991.
Chao Fang Jian‐Ping Ma Sui Wei Yu‐Bin Dong 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(2):m35-m38
1,1′‐[(Ethane‐1,2‐diyldioxy)di‐o‐phenylene]bis(indoline‐2,3‐dione), C32H24N2O6, L or (I), adopts a trans conformation with the two terminal indoline‐2,3‐dione groups located on opposite sides of the central ether bridge, as required by a centre of inversion located at the mid‐point of the ethane C—C bond. However, in the discrete binuclear AgI metallocycle complex salt bis{μ‐1,1′‐[(ethane‐1,2‐diyldioxy)di‐o‐phenylene]bis(indoline‐2,3‐dione)}disilver(I) bis(hexafluoridoantimonate), [Ag2(C32H24N2O6)2][SbF6]2, (II), synthesized by combination of L with AgSbF6, L adopts a gauche conformation to bind AgIvia the two indolinedione O atoms and two C atoms from the phenoxy ring. One dione O atom from the opposite side of the ether bridge completes the irregular coordination environment of each AgI atom. The complex is on a centre of inversion located between the AgI atoms. In the solid state, these binuclear [Ag2L2]2+ metallocycles stack together via intermolecular π–π interactions to generate a one‐dimensional chain motif, with the [SbF6]− counter‐ions, which are disordered, located between the chains. 相似文献
992.
We present an eigen-based high-order expansion basis for the spectral element approach with structured elements. The new basis exhibits a numerical efficiency significantly superior, in terms of the conditioning of coefficient matrices and the number of iterations to convergence for the conjugate gradient solver, to the commonly-used Jacobi polynomial-based expansion basis. This basis results in extremely sparse mass matrices, and it is very amenable to the diagonal preconditioning. Ample numerical experiments demonstrate that with the new basis and a simple diagonal preconditioner the number of conjugate gradient iterations to convergence has essentially no dependence or only a very weak dependence on the element order. The expansion bases are constructed by a tensor product of a set of special one-dimensional (1D) basis functions. The 1D interior modes are constructed such that the interior mass and stiffness matrices are simultaneously diagonal and have identical condition numbers. The 1D vertex modes are constructed to be orthogonal to all the interior modes. The performance of the new basis has been investigated and compared with other expansion bases. 相似文献
993.
We have developed a novel alkaline anion exchange membrane derived from poly(ether‐imide) for improved ionic conductivity. The effects of several important parameters on the chloromethylation of the membrane were investigated. These parameters included reaction temperature, reaction time, concentration of chloromethylation agent, concentration of polymer, and the amount of catalyst. The quaternization of the synthesized chloromethylated polymer was studied as well. The results show that all the studied parameters exhibited significant impacts on chloromethylation. Among them, the concentration of the chloromethylation agent played a key role in increasing the chloromethyl functional group attachment onto the polymer. It was found that the gelation could be avoided if these reaction parameters were controlled. It was also found that using an appropriate quaternization approach could significantly improve the ionic conductivity and optimize the conductivity of the membrane even though the functional chloromethyl groups attached to the polymer are limited. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
994.
995.
996.
997.
Dr. Qicai Xiao Dr. Wei Du Dr. Xiao Dong Dr. Shubo Du Sing Yee Ong Dr. Guanghui Tang Dr. Changyu Zhang Dr. Fen Yang Prof. Dr. Lin Li Prof. Dr. Liqian Gao Prof. Dr. Shao Q. Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(47):12207-12214
Mitochondria are key organelles that perform vital cellular functions such as those related to cell survival and death. The targeted delivery of different types of cargos to mitochondria is a well-established strategy to study mitochondrial biology and diseases. Of the various existing mitochondrion-transporting vehicles, most suffer from poor cytosolic entry, low delivery efficiency, limited cargo types, and cumbersome preparation protocols, and none was known to be universally applicable for mitochondrial delivery of different types of cargos (small molecules, proteins, and nanomaterials). Herein, two new cell-penetrating, mitochondrion-targeting ligands (named MitoLigand) that are capable of effectively “tagging” small-molecule drugs, native proteins and nanomaterials are disclosed, as well as their corresponding chemoselective conjugation chemistry. Upon successful cellular delivery and rapid endosome escape, the released native cargos were found to be predominantly localized inside mitochondria. Finally, by successfully delivering doxorubicin, a well-known anticancer drug, to the mitochondria of HeLa cells, we showed that the released drug possessed potent cell cytotoxicity, disrupted the mitochondrial membrane potential and finally led to apoptosis. Our strategy thus paves the way for future mitochondrion-targeted therapy with a variety of biologically active agents. 相似文献
998.
The exact solutions of the isotropic harmonic oscillator are reviewed in Cartesian, cylindrical polar and spherical coordinates. The problem of interbasis expansions of the eigenfunctions is solved completely. The explicit expansion coefficients of the basis for given coordinates in terms of other two coordinates are presented for lower excited states. Such a property is occurred only for those degenerated states for given principal quantum number n. 相似文献
999.
1000.
The surface and cross-sectional morphologies of powder metallurgy (PM) Rene95 nickel-based superalloy after 100 h oxidation in the temperature range of 700-1100 °C were investigated. It is shown that oxides nucleate first on the surface of the alloy and form an oxides scale. Afterwards, oxides scale endures decohesion, rumpling, cracking and finally spalling owing to the weak cohesive strength of the scale/alloy interface. The XRD and EDS analyses confirmed that the oxides scale of PM Rene95 superalloy is mainly composed by Cr2O3 at 800 °C and NiCr2O4 is the main spinel at 1100 °C. The subsequent analysis of internal stress verified that cracking and spalling are caused by growth stress and promoted by thermal stress. On these bases, improvement of the cohesive strength of the scale/alloy interface is considered to be the main way to increase the oxidation resistance of PM Rene95 superalloy. 相似文献