全文获取类型
收费全文 | 131981篇 |
免费 | 11477篇 |
国内免费 | 12602篇 |
专业分类
系统科学 | 4775篇 |
丛书文集 | 3673篇 |
教育与普及 | 2974篇 |
理论与方法论 | 447篇 |
现状及发展 | 911篇 |
研究方法 | 312篇 |
综合类 | 142947篇 |
自然研究 | 21篇 |
出版年
2024年 | 536篇 |
2023年 | 1220篇 |
2022年 | 1901篇 |
2021年 | 2236篇 |
2020年 | 2244篇 |
2019年 | 3913篇 |
2018年 | 4263篇 |
2017年 | 4580篇 |
2016年 | 4888篇 |
2015年 | 5925篇 |
2014年 | 6985篇 |
2013年 | 6330篇 |
2012年 | 6254篇 |
2011年 | 6801篇 |
2010年 | 6730篇 |
2009年 | 6585篇 |
2008年 | 6735篇 |
2007年 | 6675篇 |
2006年 | 5316篇 |
2005年 | 5260篇 |
2004年 | 4554篇 |
2003年 | 4161篇 |
2002年 | 4527篇 |
2001年 | 4187篇 |
2000年 | 3649篇 |
1999年 | 5210篇 |
1998年 | 4332篇 |
1997年 | 4366篇 |
1996年 | 3928篇 |
1995年 | 3413篇 |
1994年 | 3234篇 |
1993年 | 2864篇 |
1992年 | 2499篇 |
1991年 | 2353篇 |
1990年 | 1975篇 |
1989年 | 1748篇 |
1988年 | 1472篇 |
1987年 | 932篇 |
1986年 | 634篇 |
1985年 | 228篇 |
1984年 | 67篇 |
1983年 | 24篇 |
1982年 | 29篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1977年 | 29篇 |
1972年 | 77篇 |
1969年 | 15篇 |
1968年 | 16篇 |
1967年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
631.
邢莉 《科技情报开发与经济》2007,17(14):170-172
介绍了注册会计师供给关系的形成原因,分析了影响注册会计师的供需因素,探讨了注册会计师行业发展中存在的问题及对策。 相似文献
632.
Yu.Shchipunov 《复旦学报(自然科学版)》2007,(5)
1 Results The entrapment of biopolymers into silica by the sol-gel technique meets with incompatibility of inorganic and bioorganic components. The aim was to develop a compatible procedure biomimicking the biomineralization processes in the living nature. A suggested solution in Ref.[1-2] for the biopolymer entrapment into silica matrix is based on a novel silica precursor. The developed approach is distinguished from the common technique for fabrication of hybrid biopolymer-silica nanocomposite materi... 相似文献
633.
Different from traditional tax audit, supervision with self-audit is a combination of audit by the taxpayer himself and audit
by the tax authority. This paper mainly studies a taxpayer’s optimal policy of tax evasion under supervision with self-audit
and its related properties, in order to deduce some effective suggestions and theoretical bases to restrain tax evasion. Assuming
that only a certain proportion of evaded tax can be discovered when the audit is executed, the authors first formulate a static
model with self-audit. This model is divided into two stages. At the first stage, taxpayers declare their taxes, then the
tax authority chooses audit objects, based on a known probability, and announces the result; if the taxpayer is chosen, he
will enter the second stage, during which he has a chance to pay the evaded tax and the corresponding late fees and then is
audited by the tax authority. The authors show the existence and uniqueness of the optimal amount of tax evasion at the first
stage and the optimal proportion to self-expose at the second stage. The authors also discuss the related properties of the
interior solution, and do elasticity analyses on some parameters. Besides, the authors extend the static model into the corresponding
two-period model, and study the existence and uniqueness of the solution of the extended model. Finally, under the assumption
that tax evasion can only be discovered with a certain probability when the audit is executed, the authors formulate another
static model with self-audit and investigate its properties.
This research is partially supported by the National Natural Science Foundation of China under Grant Nos. 60674082, 70221001,
and 70731003. 相似文献
634.
635.
葡萄酒月度价格指标的季节ARIMA时间序列分析 总被引:1,自引:0,他引:1
以时间序列分析为工具,研究了法国葡萄酒价格月度指标,使用基于周期图的Fisher检验证实该数据指标具有潜在周期,最后发现(1,0,0)×(1,0,0)12模型能较好地拟合数据.在此基础上给出相应的预测. 相似文献
636.
Streaming teaching is adopted gradually for non-English majors in some vocational & technological colleges,and in this thesis the advantages and problems of the method are discussed according to the teaching practice.Furthermore,as a consideration of the streaming teaching,much more progress is expected to be made in the future English teaching with the help of the thesis. 相似文献
637.
A theoretical model for mid-and low-latitude ionospheric electric fields in realistic geomagnetic fields 总被引:1,自引:1,他引:0
The geomagnetic fields, which play important roles in the ionospheric dynamo, can greatly affect the global distribution of ionospheric electric fields, currents and other ionospheric electrodynamics phenomena. In the study of ionospheric electrodynamics phenomena, such as the longitudinal variations of ionospheric electric fields, the non-dipolar component of the geomagnetic fields must be taken into account. In this paper, we deduce a theoretical electric field model for ionospheric dynamo at mid- and low-latitude which adopt a modified magnetic apex coordinates system. In the new electric field model, the geomagnetic fields can be calculated from either the IGRF model or the dipole field model, and the neutral winds and conductivities are calculated based on empirical models. Then the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method, and the ionospheric electric fields and currents are derived from the calculated potential. Our model can reproduce the main features of the ionospheric electrodynamics processes, so it will be a useful tool for the investigation of the upper atmosphere and ionosphere. 相似文献
638.
倍受关注的河北省邯郸市农业银行支行金库被盗案近期有了一审结果,任晓峰、马向景二人以贪污罪被判处死刑。任、马二人非法获取四千多万元巨款用于购买彩票,案件受害方邯郸农业银行能否向当地体彩中心索回任晓峰等人用于买彩票而支付的巨款?善意取得能否适用于该案?本文通过分析善意取得制度基本理论,结合新出台的物权法规定,指出此案不适用善意取得,巨款应予追缴返还给邯郸农业银行。 相似文献
639.
将HACCP这一世界公认的食品安全控制系统引入野外施工食堂卫生管理当中.方法采用文献检索,事故分析、现场调查和Delphi等研究方法,通过对野外施工食源性疾病危害分析、建立关键控制点,形成野外施工食堂管理HACCP管理规范,并组织实施.结果实施HACCP体系后,从业人员手、餐具、菜墩、抹布的抽查合格率有显著提高,食堂从业人员以及参加施工人员对饮食卫生以及食堂卫生管理知识的掌握显著提高.结论在野外施工食品卫生管理中引入HACCP管理体系,控制食源性疾病取得了良好的绩效. 相似文献
640.
Dot pattern is a type of pattern defined by specific spatial relationship among some dots. As a compensation for concrete and meaningful visual stimuli, meaningless dot pattern can be used as stimuli in learning tasks. We performed an experiment for exploring the perceptual learning process of dot pattern against random-dot background. Participants were required to learn two types of dot patterns (9-dot and 11-dot). They were assigned to two groups: participants in Group 1 learned 9-dot pattern first and 11-dot pattern later, while those in Group 2 learned 11-dot pattern first and 9-dot pattern later. The results showed that participants could acquire the spatial relationship of dot pattern through perceptual learning in relatively short learning time. In comparison with 9-dot pattern, learning time of 11-dot pattern was slightly longer and its accuracy rate lower, but there was significant positive transfer effect from 11-dot pattern learning to 9-dot learning. 相似文献