全文获取类型
收费全文 | 107764篇 |
免费 | 17545篇 |
国内免费 | 10111篇 |
专业分类
化学 | 72626篇 |
晶体学 | 1226篇 |
力学 | 6961篇 |
综合类 | 534篇 |
数学 | 12056篇 |
物理学 | 42017篇 |
出版年
2024年 | 371篇 |
2023年 | 2138篇 |
2022年 | 3663篇 |
2021年 | 4071篇 |
2020年 | 4279篇 |
2019年 | 4160篇 |
2018年 | 3576篇 |
2017年 | 3309篇 |
2016年 | 5237篇 |
2015年 | 4992篇 |
2014年 | 6063篇 |
2013年 | 7857篇 |
2012年 | 9525篇 |
2011年 | 9838篇 |
2010年 | 6507篇 |
2009年 | 6208篇 |
2008年 | 6639篇 |
2007年 | 6104篇 |
2006年 | 5579篇 |
2005年 | 4705篇 |
2004年 | 3484篇 |
2003年 | 2735篇 |
2002年 | 2477篇 |
2001年 | 2000篇 |
2000年 | 1784篇 |
1999年 | 2093篇 |
1998年 | 1867篇 |
1997年 | 1731篇 |
1996年 | 1908篇 |
1995年 | 1520篇 |
1994年 | 1464篇 |
1993年 | 1175篇 |
1992年 | 1074篇 |
1991年 | 994篇 |
1990年 | 792篇 |
1989年 | 568篇 |
1988年 | 475篇 |
1987年 | 387篇 |
1986年 | 378篇 |
1985年 | 336篇 |
1984年 | 259篇 |
1983年 | 155篇 |
1982年 | 163篇 |
1981年 | 121篇 |
1980年 | 87篇 |
1979年 | 68篇 |
1978年 | 47篇 |
1977年 | 46篇 |
1976年 | 51篇 |
1974年 | 52篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
HL-1装置中LHCD和等离子体参数的关系 总被引:1,自引:1,他引:0
本文研究了在HL-1托卡马克的不同放电阶段的低混杂波驱动特性。给出了驱动电流及驱动效率和等离子体参数,如电子平均密度ne、等离子体电流Ip及纵向磁场的关系。也给出和分析了波驱动和入射波功率的关系。在放电平段,对正反向驱动效率进行了研究和比较。 相似文献
192.
The reduction of chromate by glutathione, its mono- and diethyl esters,
-cysteine, 2-mercapto-propionic acid and mercapto-succinic acid has been studied. The empirical rate law kobs = ab[Thiol]2/(1 + b[Thiol]) is obeyed by all of these thiols, at neutral pH. No evidence could be obtained for a first-order pathway in glutathione under these conditions. These observations are used to comment on the stability of intermediates potentially important in explaining chromate toxicity. 相似文献
193.
Main chain liquid crystal polymers are modelled as either worms or jointed rods. In reality they are composed of mesogenic units (rods) linked by spacers with varying degrees of flexibility. We present a molecular model to describe non-homogeneous nematic polymers. The model takes account of molecular parameters, such as the lengths of the mesogenic group and the spacer units, and the interactions between them. The spacers are found to have an order differing from the mesogenic units. If the spacer is not very long and thus in effect is inflexible, one end of the spacer can retain to some extent the orientation of the other end, allowing orientational correlation between spacers mediated by the intermediate mesogenic unit. This is important in giving the chain a global rod-like behaviour as the nematic field becomes strong or the temperature low. The nematic order of the two components (mesogens and spacers), the nematic-isotropic transition as well as the latent entropy are examined. Furthermore, the anisotropic conformations of the polymers are investigated, which show either rod-like or random walk behaviour. Comparison of our results with experiment is found to be satisfactory. 相似文献
194.
In this paper,based on the results presented in part Ⅰ of this paper[18],we present a numerical embedding algorithm for solving the nonlinear complementarityproblem, and prove its convergence carefully. Numerical experiments show that thealgorithm is successful. 相似文献
195.
本改进了二阶线性微分方程的朗期基解法,只要求出转化以后的一阶微分方程或二阶齐次线性微分方程的一个特解,即可求出二阶线性微分方程的通解。 相似文献
196.
应用导数的定义,为分段函数的分界点提供了一种行之有效的求导方法,利用微分的定义判断函数在分界点及其他特殊点的可微性,运用定和分的定义求一类特殊类型的极限. 相似文献
197.
素质教育的主阵地是课堂教学.如何切实做到物理教学素质化呢?下面结合“全反射”的教学,谈几点看法和做法.1 课堂教学目标构建的多元性 课堂教学强调目标构建的多元性,以完成教学多方位的艰巨任务,这是素质教育的重要教学特征之一.因而在制定具体的物理教学目标时,既要有知识、技能方面的要求, 相似文献
198.
Effect of track stiffness on vibration levels in railway tunnels 总被引:1,自引:0,他引:1
The paper discusses the difficulties in comparing and drawing conclusions from vibration measurements made in different railway tunnels. A number of new measurements are presented, which have been made and analyzed on a consistent basis. The track stiffness has been determined for each of the measurements. Graphs are presented which indicate the level of rail and tunnel floor vibration likely to occur for different track stiffnesses. The variance in the measurement results also indicates the potential error in using the data to predict vibration levels in new situations. 相似文献
199.
A new synthetic method for the manufacture of glutaric dialdehyde is investigated. Glutaric dialdehyde was prepared by the
addition-hydrolysis reaction of benzimidazolium salt with saturated dihalide as the di-Grignard reagent. The yield of glutaric
dialdehyde by this method can reach 73%. Both infrared spectra and melting point of the compound were consistent with those
reported earlier.
Translated from Journal of Northwest University (Natural Science Edition), 2005, 35(2) (in Chinese) 相似文献
200.
在本文中,我们讨论了带作用群的群系的临界结构,给出了处理允许某些作用群的群的问题的一般方法,作为应用,我们特别给出了关于幂零群及p-幂零群的一些结果。 相似文献