全文获取类型
收费全文 | 6002篇 |
免费 | 742篇 |
国内免费 | 620篇 |
专业分类
化学 | 2614篇 |
晶体学 | 66篇 |
力学 | 267篇 |
综合类 | 23篇 |
数学 | 585篇 |
物理学 | 1519篇 |
综合类 | 2290篇 |
出版年
2024年 | 20篇 |
2023年 | 109篇 |
2022年 | 140篇 |
2021年 | 183篇 |
2020年 | 204篇 |
2019年 | 156篇 |
2018年 | 177篇 |
2017年 | 203篇 |
2016年 | 216篇 |
2015年 | 217篇 |
2014年 | 294篇 |
2013年 | 369篇 |
2012年 | 419篇 |
2011年 | 452篇 |
2010年 | 307篇 |
2009年 | 393篇 |
2008年 | 369篇 |
2007年 | 356篇 |
2006年 | 365篇 |
2005年 | 292篇 |
2004年 | 228篇 |
2003年 | 191篇 |
2002年 | 187篇 |
2001年 | 160篇 |
2000年 | 138篇 |
1999年 | 170篇 |
1998年 | 154篇 |
1997年 | 126篇 |
1996年 | 134篇 |
1995年 | 107篇 |
1994年 | 84篇 |
1993年 | 73篇 |
1992年 | 67篇 |
1991年 | 70篇 |
1990年 | 64篇 |
1989年 | 36篇 |
1988年 | 30篇 |
1987年 | 25篇 |
1986年 | 29篇 |
1985年 | 8篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1957年 | 2篇 |
1955年 | 2篇 |
1929年 | 2篇 |
1926年 | 2篇 |
排序方式: 共有7364条查询结果,搜索用时 0 毫秒
11.
WANG Xibo ZHOU Benhai YU Gei LI Qian 《武汉大学学报:自然科学英文版》2007,12(5):946-950
μC/OS-Ⅱ is an open source real-time kernel adopting priority preemptive schedule strategy. Aiming at the problem of μC/OS-Ⅱ failing to support homology priority tasks scheduling, an approach for solution is proposed. The basic idea is adding round-robin scheduling strategy in its original scheduler in order to schedule homology priority tasks through time slice roundrobin. Implementation approach is given in detail. Firstly, the Task Control Block (TCB) is extended. And then, a new priority index table is created, in which each index pointer points to a set of homology priority tasks. Eventually, on the basis of reconstructing μC/OS-Ⅱ real-time kernel, task scheduling module is rewritten. Otherwise, schedulability of homology task supported by modified kernel had been analyzed, and deadline formula of created homology tasks is given. By theoretical analysis and experiment verification, the modified kernel can support homology priority tasks scheduling, meanwhile, it also remains preemptive property of original μC/OS-Ⅱ. 相似文献
12.
We derive the Friedmann-like equations in braneworld cosmology by imposing the first law of thermodynamics and Bekenstein's area-entropy formula on the apparent horizon of a Friedmann–Robertson–Walker universe in both Randall–Sundrum II gravity and Dvali–Gabadadze–Porrati gravity models. Israel's boundary condition plays an important role in our calculations in both cases, besides the first law of thermodynamics and Bekenstein's area-entropy formula. The results indicate that thermodynamics on the brane world knows the behaviors of gravity. 相似文献
13.
Duan Jinqing Liu Hongbin Zhang Xinian Lu Hongmin Gou Ai Liu Zheng Wang Tao Ge Rili 《中国工程科学》2006,4(2):183-186
Study Objective: To compare and analyze the changes of the pulmonary-artery pressure of the migrants coming from different elevation in the hypoxic environment of 4636 - 4907 m extreme altitude. To explore the susceptibility to hypoxic pulmonary-artery hypertension (PH) in the subjects from different altitude and profession. Methods: By using Color Doppler Ultmsonography (CDU), measuring the pulmonary-artery pressure of 207 healthy men, who had continuously being lived and worked at the extreme altitude for more than six months, and then were divided into three groups according to their profession and the altitude of original living place. Results: There was a significant difference in the outcomes of pulmonary-artery pressure from the 3 groups. Conclusions: Altitude of original living place, labor intensity are some of factors that impact the pulmonary-artery pressure of the people who exposure to a hypoxic environment. The pulmonary- artery pressure of person without strenuously physical work experience was more sensitive to hypoxic surroundings than that of labor workers. It was not always the fact at an extreme altitude that the moderate altitude mountaineers were superior to other migrants from a lower altitude or plain. The higher PH was found in the groups of the moderate altitude mountaineers and labor workers. It is unlikely certain that one with PH would surfer from HAPE. 相似文献
14.
15.
The Existence of Solutions to Sturm-Liouville Boundary Value Problems with Laplacian-like Operator 总被引:2,自引:0,他引:2
Wei-ping Sun Wei-gao GeDepartment of Applied Mathematics Beijing Institute of Technology Beijing China 《应用数学学报(英文版)》2002,18(2):341-348
Abstract The existence of infinitely many solutions to Sturm-Liouville boundary value problem with aLaplacian-like operator is studied by applying generalized polar coordinates. 相似文献
16.
The classical (first integral) methods of studying restrictions on the possible motion of gravitationally interacting bodies are reviewed. The simple and flexible inequality method is extended to a similar approach to the relationship between possible forbidden motion and (asymptotic) symmetries in the relativistic few-body problem. This extended method is used to reproduce the standard results of bounded motion for a test particle in a Schwarzschild geometry. The existence of bounded motion is shown for the general relativistic few-body problem and the difficulties in determining such bounded motion is analysed. The use of this approach to obtaining a relativistic alternative to the classical Roche lobe analysis in contact binaries is discussed. 相似文献
17.
Dirichlet boundary value problems for perturbed second-order differential equations on a half line are investigated in this paper. The methods mainly depend on the calculus of variations to the classical functionals. Sufficient conditions are obtained for the existence of the solutions. 相似文献
18.
19.
根据运动员的成才特点,阐述了科学选材、运动训练及教练员执教能力对形成运动员技术风格个性化过程中所起的作用。 相似文献
20.
Recently, molecular imaging has been rapidly developed to studyphysiological and pathological processes in vivo at the cellularand molecular levels. Among molecular imaging modalities, opticalimaging has attracted a major attention for its unique advantages.In this paper, we establish a mathematical framework for multispectralbioluminescence tomography (BLT) that allows simultaneous studiesof multiple optical reporters. We show solution existence, uniquenessand continuous dependence on data as well as the limiting behaviourswhen the regularization parameter approaches zero or when thepenalty parameter approaches infinity. Then, we propose twonumerical schemes for multispectral BLT and derive error estimatesfor the corresponding solutions. 相似文献