全文获取类型
收费全文 | 142564篇 |
免费 | 9011篇 |
国内免费 | 6583篇 |
专业分类
化学 | 52376篇 |
晶体学 | 1331篇 |
力学 | 8998篇 |
综合类 | 284篇 |
数学 | 35608篇 |
物理学 | 31611篇 |
综合类 | 27950篇 |
出版年
2024年 | 322篇 |
2023年 | 1153篇 |
2022年 | 1965篇 |
2021年 | 2275篇 |
2020年 | 2106篇 |
2019年 | 1955篇 |
2018年 | 12049篇 |
2017年 | 11876篇 |
2016年 | 8536篇 |
2015年 | 3507篇 |
2014年 | 3803篇 |
2013年 | 4438篇 |
2012年 | 8742篇 |
2011年 | 15781篇 |
2010年 | 9728篇 |
2009年 | 9988篇 |
2008年 | 10808篇 |
2007年 | 12823篇 |
2006年 | 3593篇 |
2005年 | 4127篇 |
2004年 | 3770篇 |
2003年 | 3776篇 |
2002年 | 2831篇 |
2001年 | 1816篇 |
2000年 | 1676篇 |
1999年 | 1877篇 |
1998年 | 1613篇 |
1997年 | 1546篇 |
1996年 | 1439篇 |
1995年 | 1234篇 |
1994年 | 1073篇 |
1993年 | 893篇 |
1992年 | 806篇 |
1991年 | 694篇 |
1990年 | 635篇 |
1989年 | 503篇 |
1988年 | 387篇 |
1987年 | 260篇 |
1986年 | 237篇 |
1985年 | 155篇 |
1984年 | 92篇 |
1983年 | 85篇 |
1982年 | 74篇 |
1981年 | 65篇 |
1980年 | 61篇 |
1979年 | 52篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
11.
本文讨论了每个元都有幂等元作为右单位元的左消半群与幂单半群N的Schuzenberger积M◇N的ρ类,证明了这种半群M与N的Schuzenberger积M◇N的ρ类是右E一半适合半群和弱E-headged半群. 相似文献
12.
Static extracting method of software intended behavior based on API functions invoking 总被引:1,自引:0,他引:1
The method of extracting and describing the intended behavior of software precisely has become one of the key points in the fields of software behavior's dynamic and trusted authentication. In this paper, the author proposes a specified measure of extracting SIBDS (software intended behaviors describing sets) statically from the binary executable using the software's API functions invoking, and also introduces the definition of the structure used to store the SIBDS in detail. Experimental results demonstrate that the extracting method and the storage structure definition offers three strong properties: (i) it can describe the software's intended behavior accurately; (ii) it demands a small storage expense; (iii) it provides strong capability to defend against mimicry attack. 相似文献
13.
针对C++语言中继承方式及访问权限的理解极易混淆的问题,详细讨论了对C++语言中的继承方式及成员访问权限的教学,并给出具体的继承访问控制的例子。 相似文献
14.
15.
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
16.
王滨 《科技情报开发与经济》2007,17(21):101-102
简述了素质教育的含义,分析了图书馆在素质教育中所处的地位和具备的优势,探讨了图书馆开展素质教育的有效途径。 相似文献
17.
Christiane Albrecht 《Analytical and bioanalytical chemistry》2008,390(5):1223-1224
18.
19.
Chengzhi Qi Mingyang Wang Qihu Qian Jianjie Chen 《Moscow University Mechanics Bulletin》2008,63(5):113-121
The formation mechanisms for the structural hierarchy in geological media are discussed. It is shown that the formation of such a hierarchy is caused by certain external and internal circumstances. The first ones consist in the fact that, because of external actions, the Earth’s poles continuously execute the translational and rotational motions responsible for a regular structure of rock fracture and for the appearance of the scale factor √2. The second ones consist in the fact that, under the action of many random factors and because of external actions, during the formation of geological media there appear dissipative structures and, hence, some self-similar fractal structures are formed. 相似文献
20.
You‐Liang Zhao Chuan‐Fu Chen Fu Xi 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2156-2165
The atom transfer radical copolymerization of N‐substituted maleimides such as N‐phenylmaleimide (PhMI), N‐cyclohexylmaleimide (ChMI), and N‐butylmaleimide (NBMI) with styrene initiated with dendritic polyarylether 2‐bromoisobutyrates in an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF6]), at room temperature and anisole at 110 °C was investigated. The dendritic‐linear block copolymers obtained in ionic liquid possessed well‐defined molecular weight and low polydispersity (1.05 < Mw/Mn < 1.32) and could be used as a macroinitiator for chain‐extension polymerization, suggesting the living nature of the reaction system. The ionic liquids containing catalyst could be recycled in the atom transfer radical polymerization systems without further treatment. Compared with polymerization conducted in anisole, the polymerization in ionic liquid had a stronger tendency for alternation. The tendency for alternation decreased in the order PhMI > NBMI > ChMI in [bmim][PF6] and PhMI > ChMI > NBMI in anisole. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2156–2165, 2003 相似文献