全文获取类型
收费全文 | 10979篇 |
免费 | 151篇 |
国内免费 | 281篇 |
专业分类
系统科学 | 787篇 |
丛书文集 | 237篇 |
教育与普及 | 259篇 |
理论与方法论 | 31篇 |
现状及发展 | 91篇 |
研究方法 | 31篇 |
综合类 | 9974篇 |
自然研究 | 1篇 |
出版年
2024年 | 25篇 |
2023年 | 45篇 |
2022年 | 83篇 |
2021年 | 85篇 |
2020年 | 57篇 |
2019年 | 32篇 |
2018年 | 28篇 |
2017年 | 116篇 |
2016年 | 103篇 |
2015年 | 183篇 |
2014年 | 170篇 |
2013年 | 149篇 |
2012年 | 164篇 |
2011年 | 745篇 |
2010年 | 334篇 |
2009年 | 543篇 |
2008年 | 340篇 |
2007年 | 357篇 |
2006年 | 235篇 |
2005年 | 352篇 |
2004年 | 1250篇 |
2003年 | 830篇 |
2002年 | 503篇 |
2001年 | 459篇 |
2000年 | 385篇 |
1999年 | 566篇 |
1998年 | 557篇 |
1997年 | 596篇 |
1996年 | 239篇 |
1995年 | 250篇 |
1994年 | 224篇 |
1993年 | 374篇 |
1992年 | 264篇 |
1991年 | 234篇 |
1990年 | 178篇 |
1989年 | 147篇 |
1988年 | 104篇 |
1987年 | 49篇 |
1986年 | 36篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1974年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The influences of carboxymethyl starch used as stabilizer upon the stability of native cornstarch-polyvinyl alcohol blend pastes for warp sizing have been investigated. The effect of the modified starch on the paste stability was evaluated in terms of the initial demixing time and the volume percentage of separated starch. The carboxymethyl starch with a series of different degrees of substitution was prepared in ethanol dispersion by varying the amount of monochloroacetic acid reacted with refined native cornstarch. The paste stability strongly depends on the modification extent and amount of carboxymethyl starch used, and on native starch content in the paste. Increase in the modification extent and/or the amount of the modified starch effectively retards the phase separation and reduces the separation extent of native cornstarch-polyvinyl alcohol blend pastes. Moreover, the mechanism and favorable modification extent of carboxymethyl starch for enhancing paste stability are also investigated and disc 相似文献
102.
A group of grafted PET fibers with different graft yield are formed by grafting acrylamide onto the PET main chains. The structure of grafted fibers are studied by scanning electronic microscope ( SEM ), infra-red spectrophotometer ( IR ), and differential scanning calorimetry(DSC). At the same time, the moisture regain, dyeability, strength, and elongation at break of the samples are measured and their relations with structural changes are discussed. Compared with ungrafted fiber, shape of the fiber cross-section, IR characteristic absorption peaks, and melting behavior of the grafted fibers have been changed, causing the fiber dyeability and moisture regain to be increased, and mechanical properties to be changed. 相似文献
103.
Service and information resources are two kinds of major shared resources in virtual enterprises, where, service resources include third party‘s service resources and enterprise‘s legacy service resources, and information resources include database resources and file resources. Since service and information resources have distributed, autonomic, remotely bound as well as some other similar characteristics, an implementation mechanism on managing shared resources based on UDDI are presented. XML instances are used to describe resources authorization information, WSDLbased special XML instance represents information resource metadata, and these XML instancesare referenced by tModel for realizing the purpose of managing shared resources metadata based on UDDI. 相似文献
104.
ZENGHuarong YINQingrui LIGuorong LUOHaosu XUZhenkui 《科学通报(英文版)》2003,48(13):1386-1389
The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTi03 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezoresponse behavior related to the screening charges compensation mechanism is observed on the (111) crystal face. The significant piezoresponse degradation behavior with low piezoresponse signal under high vacuum is attributed to the instability of the polarization state due to the insufficient compensation of the intrinsic screening charges for the polarization charges in PMN-30%PT single crystal. In contrast, the remarkable domain contrast of the sample at ambient pressure is owing to the dominant surface screening charges deriving from surface adsorption, which plays an important role in determining the stability of the domain behavior and in achieving the optimal properties. 相似文献
105.
106.
介绍了演绎数据库的系统结构,并着重介绍了基于SQL Serverr之上的递归查询算法和将以规则形式存放于外存的虚关系转化为内部表示的过程。 相似文献
107.
谷峰 《西南师范大学学报(自然科学版)》2003,28(5):741-745
在一般的Banach空间中证明了非线性方程x tx=f的解的具误差的Ishikawa迭代过程的新的稳定性定理,推广和改进了近期的一系列相关结果. 相似文献
108.
C9φE10S-C16NMe3混合液的表面活性比C9φE10和C16NMe3的高得多,对辛醇的增溶曲线呈“V”字形,混合比接近l:l时,增溶量最小;对苯、邻二甲苯的增溶曲线呈“M”字形,在混合比接近l:5和5:l时出现两个极大值,l:l时出现一个极小值.在C9φE10-C16NMe3的溶液中,辛烷的加入对辛醇的增溶几乎无影响;邻二甲苯的加入使辛醇的增溶量明显下降. 相似文献
109.
植物学实验教学改革及其对学生创新能力的培养 总被引:21,自引:0,他引:21
对植物学实验体系进行了改革.压缩验证性实验,加强综合性、设计性和研究性实验,旨在培养学生的实践能力和创新精神. 相似文献
110.
对目前主要的数据存储方式进行了介绍,针对网络中单个应用系统存储需求紧张而同时网络中存在存储资源浪费、闲置等情况,提出了用软件实现基于B/S模式的网络存储系统BSMSM(B/S Model based Shared Memory),从而实现了跨平台的网络存储. 相似文献