全文获取类型
收费全文 | 106314篇 |
免费 | 12108篇 |
国内免费 | 8303篇 |
专业分类
化学 | 34591篇 |
晶体学 | 1288篇 |
力学 | 15838篇 |
综合类 | 1575篇 |
数学 | 37532篇 |
物理学 | 35901篇 |
出版年
2024年 | 133篇 |
2023年 | 916篇 |
2022年 | 1432篇 |
2021年 | 2940篇 |
2020年 | 2684篇 |
2019年 | 2623篇 |
2018年 | 2423篇 |
2017年 | 3049篇 |
2016年 | 3538篇 |
2015年 | 3060篇 |
2014年 | 4824篇 |
2013年 | 7926篇 |
2012年 | 5398篇 |
2011年 | 6443篇 |
2010年 | 5485篇 |
2009年 | 6622篇 |
2008年 | 6795篇 |
2007年 | 6868篇 |
2006年 | 5878篇 |
2005年 | 4844篇 |
2004年 | 4289篇 |
2003年 | 4054篇 |
2002年 | 6280篇 |
2001年 | 3509篇 |
2000年 | 2976篇 |
1999年 | 2596篇 |
1998年 | 2428篇 |
1997年 | 1901篇 |
1996年 | 1540篇 |
1995年 | 1345篇 |
1994年 | 1316篇 |
1993年 | 1177篇 |
1992年 | 1099篇 |
1991年 | 823篇 |
1990年 | 676篇 |
1989年 | 530篇 |
1988年 | 530篇 |
1987年 | 439篇 |
1986年 | 365篇 |
1985年 | 537篇 |
1984年 | 454篇 |
1983年 | 249篇 |
1982年 | 448篇 |
1981年 | 587篇 |
1980年 | 517篇 |
1979年 | 566篇 |
1978年 | 469篇 |
1977年 | 349篇 |
1976年 | 287篇 |
1973年 | 166篇 |
排序方式: 共有10000条查询结果,搜索用时 51 毫秒
1.
2.
Dan Chen Kaixin Du Xiaochen Niu Hongwei Zhang Xue Zhang Yu Tang Jianchun Zhao 《Biomedical chromatography : BMC》2022,36(3):e5288
Amlexanox, an anti-inflammatory and anti-allergic agent, has been widely used clinically for the treatment of canker sores, asthma, and allergic rhinitis. Recently, amlexanox has received considerable attention in curing nonalcoholic fatty liver diseases and hepatitis virus infection. Herein, we first established a sensitive high-performance liquid chromatography-tandem mass spectrum (LC–MS/MS) method for the determination of amlexanox in rat plasma. Propranolol was used as the internal standard (IS). Using a simple protein precipitation method, the amlexanox and IS were separated with Capcell Pak C18 column (2.0 × 50 mm, 5 μm) and eluted with water and acetonitrile each containing 0.1% formic acid using gradient elution condition at a flow rate of 0.4 mL·min−1. Amlexanox and IS were detected by a triple quadrupole mass in multiple reactive monitoring (MRM) under the transitions of m/z 299.2 → 281.2 and m/z 259.9 → 116.1 with positive electrospray ionization, respectively. The calibration curves of amlexanox were established with the range of 50 to 2000 ng·mL−1 (r2 > 0.99). The validation method consisted of selectivity, accuracy, precision, carryover effect, matrix effect, recovery, dilution effect, and stability. The fully validated method was successfully applied to the pharmacokinetic study of amlexanox in Wistar rats. 相似文献
3.
This paper is concerned with the Cauchy problem on the Boltzmann equation without angular cutoff assumption for hard potential in the whole space. When the initial data is a small perturbation of a global Maxwellian, the global existence of solution to this problem is proved in unweighted Sobolev spaces with . But if we want to obtain the optimal temporal decay estimates, we need to add the velocity weight function, in this case the global existence and the optimal temporal decay estimate of the Boltzmann equation are all established. Meanwhile, we further gain a more accurate energy estimate, which can guarantee the validity of the assumption in Chen et al. (0000). 相似文献
4.
5.
Aiming at training the feed-forward threshold neural network consisting of nondifferentiable activation functions, the approach of noise injection forms a stochastic resonance based threshold network that can be optimized by various gradient-based optimizers. The introduction of injected noise extends the noise level into the parameter space of the designed threshold network, but leads to a highly non-convex optimization landscape of the loss function. Thus, the hyperparameter on-line learning procedure with respective to network weights and noise levels becomes of challenge. It is shown that the Adam optimizer, as an adaptive variant of stochastic gradient descent, manifests its superior learning ability in training the stochastic resonance based threshold network effectively. Experimental results demonstrate the significant improvement of performance of the designed threshold network trained by the Adam optimizer for function approximation and image classification. 相似文献
6.
M. Amar D. Andreucci R. Gianni C. Timofte 《Journal of Mathematical Analysis and Applications》2021,493(2):124533
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation. 相似文献
7.
Bifurcation analysis of visual angle model with anticipated time and stabilizing driving behavior 下载免费PDF全文
Xueyi Guan 《中国物理 B》2022,31(7):70507-070507
In the light of the visual angle model (VAM), an improved car-following model considering driver's visual angle, anticipated time and stabilizing driving behavior is proposed so as to investigate how the driver's behavior factors affect the stability of the traffic flow. Based on the model, linear stability analysis is performed together with bifurcation analysis, whose corresponding stability condition is highly fit to the results of the linear analysis. Furthermore, the time-dependent Ginzburg-Landau (TDGL) equation and the modified Korteweg-de Vries (mKdV) equation are derived by nonlinear analysis, and we obtain the relationship of the two equations through the comparison. Finally, parameter calibration and numerical simulation are conducted to verify the validity of the theoretical analysis, whose results are highly consistent with the theoretical analysis. 相似文献
8.
9.
10.