全文获取类型
收费全文 | 69739篇 |
免费 | 2533篇 |
国内免费 | 1686篇 |
专业分类
化学 | 35023篇 |
晶体学 | 1094篇 |
力学 | 4023篇 |
综合类 | 103篇 |
数学 | 6065篇 |
物理学 | 27650篇 |
出版年
2022年 | 613篇 |
2021年 | 755篇 |
2020年 | 831篇 |
2019年 | 765篇 |
2018年 | 872篇 |
2017年 | 784篇 |
2016年 | 1334篇 |
2015年 | 1047篇 |
2014年 | 1541篇 |
2013年 | 3263篇 |
2012年 | 3178篇 |
2011年 | 3937篇 |
2010年 | 2743篇 |
2009年 | 2851篇 |
2008年 | 3466篇 |
2007年 | 3259篇 |
2006年 | 3095篇 |
2005年 | 2762篇 |
2004年 | 2448篇 |
2003年 | 2120篇 |
2002年 | 1972篇 |
2001年 | 3300篇 |
2000年 | 2411篇 |
1999年 | 1848篇 |
1998年 | 1383篇 |
1997年 | 1299篇 |
1996年 | 1140篇 |
1995年 | 999篇 |
1994年 | 940篇 |
1993年 | 778篇 |
1992年 | 1085篇 |
1991年 | 1052篇 |
1990年 | 965篇 |
1989年 | 816篇 |
1988年 | 802篇 |
1987年 | 870篇 |
1986年 | 728篇 |
1985年 | 937篇 |
1984年 | 865篇 |
1983年 | 592篇 |
1982年 | 585篇 |
1981年 | 554篇 |
1980年 | 513篇 |
1979年 | 631篇 |
1978年 | 651篇 |
1977年 | 664篇 |
1976年 | 575篇 |
1975年 | 485篇 |
1974年 | 522篇 |
1973年 | 452篇 |
排序方式: 共有10000条查询结果,搜索用时 338 毫秒
31.
32.
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices.... 相似文献
33.
34.
35.
Development of an LC‐MS/MS method for determining the pharmacokinetics of clonidine following oral administration of Zhenju antihypertensive compound 下载免费PDF全文
Jing Qin Limin Wang Lihong Wu Jun Chen Teng Shen Yongji Li Limei Han Jianxin Wang 《Biomedical chromatography : BMC》2015,29(7):1068-1075
Zhenju antihypertensive compound (ZJAHC) is a combined Chinese–Western medicine formula including clonidine (CLO), hydrochlorothiazide (HCT), rutin, Chrysanthemum indicum extract and pearl powder. Compared with CLO preparations, ZJAHC shows improved activities and decreased adverse effects. It is believed that the side effects of CLO are caused by its high peak plasma concentration. Hence, study of the influence of ZJAHC on the pharmacokinetic behaviors of clonidine seems essential. In present study, the plasma concentrations of CLO were determined with a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method. The MS/MS transitions monitored for clonidine and internal standard were 230.2 → 213.1 and 152.2 → 110.2, respectively. The analyte was quantified in a single run within 3 min. The pharmacokinetic study showed that the area under the plasma concentration–time curve of CLO in ZJAHC (60 µg/kg CLO) was similar to that of CLO‐HCT‐high (120 µg/kg CLO) but the peak concentration was much lower than that in CLO‐HCT‐high. ZJAHC could enhance the bioavailability without greatly increasing peak concentration of clonidine. This comprehensive effect of enhancing the bioavailability and avoiding the high peak plasma concentration for CLO might mainly result from the co‐contribution of Western medicine and traditional Chinese medicine (TCM), while the effect of TCM was stronger than that of Western medicine. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
36.
37.
Journal of Global Optimization - In this paper, we propose a novel algorithm that is based on quadratic-piecewise-linear approximations of DC functions to solve nonnegative sparsity-constrained... 相似文献
38.
Uhm H.S. Lee P.H. Kim Y.I. Kim J.H. Chang H.Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(4):628-635
A theory is developed for the density profile of low temperature plasmas confined by applied magnetic field and an experiment of the electron-cyclotron-resonance (ECR) plasma is conducted to compare the theoretical prediction and experimental measurements. Due to a large electron mobility along the magnetic field, electrons move quickly out of the system, leaving ions behind and building a space charge potential, which leads to the ambipolar diffusion of ions. In a steady-state condition, the plasma generation by ionization of neutral molecules is in balance with plasma loss due to the diffusion, leading to the electron temperature equation, which is expressed in terms of the plasma size, chamber pressure, and the ionization energy and cross section of neutrals. The power balance condition leads to the plasma density equation, which is also expressed in terms of the electron temperature, the input microwave power and the chamber pressure. It is shown that the plasma density increases, reaches its peak and decreases, as the chamber pressure increases from a small value (0.1 mTorr). These simple expressions of electron temperature and density provide a scaling law of ECR plasma in terms of system parameters. After carrying out an experimental observation, it is concluded that the theoretical predictions of the electron temperature and plasma density agree remarkably well with experimental data 相似文献
39.
超临界流体色谱流程设计及其应用 总被引:1,自引:1,他引:0
本文设计了多功能超临界流体色谱流程,流程中包括毛细管/微填充柱SFC,GC,计算机控制温度、压力、密度及信号采集、处理,配置有超临界流体萃取池,解决了超临界流体色谱分流口易堵问题。利用该流程,将石腊、DC-200气相色谱固定相、黄油、蜂蜡、救心油、红花油等样品进行超临界流体色谱分离。 相似文献
40.
In a previous paper (Ref. 1), an exact solution of the optimal planar interception with fixed end conditions was derived in closed form. The optimal control was expressed as an explicit function of the state variables and two fixed parameters, obtained by solving a set of nonlinear algebraic equations involving elliptic integrals. In order to facilitate the optimal control implementation, the present paper derives a highly accurate simplified solution assuming that the ratio of the pursuer turning radius to the initial range is small. An asymptotic expansion further reduces the computational workload. Construction of a near-optimal open-loop control, based on the approximations, completes the present paper. 相似文献