全文获取类型
收费全文 | 56438篇 |
免费 | 6011篇 |
国内免费 | 6776篇 |
专业分类
化学 | 23324篇 |
晶体学 | 554篇 |
力学 | 1570篇 |
综合类 | 459篇 |
数学 | 3360篇 |
物理学 | 11590篇 |
综合类 | 28368篇 |
出版年
2024年 | 203篇 |
2023年 | 756篇 |
2022年 | 1476篇 |
2021年 | 1647篇 |
2020年 | 1590篇 |
2019年 | 1542篇 |
2018年 | 1366篇 |
2017年 | 1526篇 |
2016年 | 1845篇 |
2015年 | 2309篇 |
2014年 | 3114篇 |
2013年 | 3576篇 |
2012年 | 4131篇 |
2011年 | 4391篇 |
2010年 | 3804篇 |
2009年 | 3930篇 |
2008年 | 4247篇 |
2007年 | 4034篇 |
2006年 | 3666篇 |
2005年 | 3121篇 |
2004年 | 2369篇 |
2003年 | 1945篇 |
2002年 | 2084篇 |
2001年 | 1809篇 |
2000年 | 1576篇 |
1999年 | 1290篇 |
1998年 | 844篇 |
1997年 | 774篇 |
1996年 | 651篇 |
1995年 | 631篇 |
1994年 | 533篇 |
1993年 | 417篇 |
1992年 | 357篇 |
1991年 | 347篇 |
1990年 | 310篇 |
1989年 | 247篇 |
1988年 | 225篇 |
1987年 | 158篇 |
1986年 | 126篇 |
1985年 | 71篇 |
1984年 | 39篇 |
1983年 | 28篇 |
1982年 | 34篇 |
1981年 | 11篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 6篇 |
1957年 | 4篇 |
1955年 | 4篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 60 毫秒
1.
在修正Yukawa相互作用的基础上,采用常温分子动力学方法数值研究了带电胶体系统的大离子屏蔽效应和多分散性效应对其固液边界的影响.研究结果发现,在屏蔽长度较大时,固液相变曲线出现了明显偏差.初步定性认为这种相边界偏差现象来自于系统多体效应的增强.另外,数值研究了固液相变时键接取向序参数的变化. 相似文献
2.
3.
4.
5.
不同维生素组合对南美白对虾生长性能的影响 总被引:1,自引:0,他引:1
选取我国海水养殖种类中的南美白对虾为研究对象,采用均匀设计法,在相同基础日粮中,分别添加不同配比的维生素组合,其中有VE(X1)、烟酸(X2)、肌醇(X3)、泛酸钙(X4)、VB6(X5),经过45 d的试验,以相对体重和相对体长为指标,建立了多元二次多项式回归模型,并利用SAS软件在计算机上拟合,用求极值的方法给出南美白对虾不同维生素组合的最佳配方. 相似文献
6.
Chun‐Yan Hong Ye‐Zi You Cai‐Yuan Pan 《Journal of polymer science. Part A, Polymer chemistry》2004,42(19):4873-4881
Well‐defined diblock and triblock copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (PEO) were successfully synthesized through the reversible addition–fragmentation chain transfer polymerization of N‐isopropylacrylamide (NIPAM) with PEO capped with one or two dithiobenzoyl groups as a macrotransfer agent. 1H NMR, Fourier transform infrared, and gel permeation chromatography instruments were used to characterize the block copolymers obtained. The results showed that the diblock and triblock copolymers had well‐defined structures and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.2), and the molecular weight of the PNIPAM block in the diblock and triblock copolymers could be controlled by the initial molar ratio of NIPAM to dithiobenzoate‐terminated PEO and the NIPAM conversion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4873–4881, 2004 相似文献
7.
Chunxia Zhao Guowang Xu Xianzhe Shi Jianmei Ma Yan Zhang Shen Lv Qianfeng Weng Qing Yang 《Analytical sciences》2004,20(7):1001-1005
Fluorescent-based single-strand conformation polymorphism (F-SSCP) analysis with capillary electrophoresis (CE) is the most common method for the detection of mutation because of its high sensitivity and resolution. In this study, we prepared an inexpensive linear polyacrylamide (LPA), and successfully applied it to CE-SSCP analysis and tandem CE-SSCP/heteroduplex analysis (HA) of the P53 gene on an ABI capillary genetic analyzer. A comparison of the sieving capabilities of a homemade LPA and commercial polydimethylacrylamide (PDMA) demonstrates that the homemade LPA has a higher resolution, a shorter analysis time, and is more suitable for tandem SSCP/HA than commercial PDMA. To show the usefulness, mutations of P53 gene exon 7 - 8 in 37 tumor samples were investigated by using homemade LPA. The results indicate that 10 mutations were found in 9 of 37 cases; the majority of P53 mutations were missense mutations, and 70% were located in exon 7, which plays an important role in neoplastic progression in human tumorigenesis. 相似文献
8.
Yan Youping 《东华大学学报(英文版)》1995,(2)
A special tip of vortex twisting nozzle is designed and fastened at the exit out of the drafted reed space or shed. Compressed air is supplied by the tube near the last subnozzle, weft yarn is retwisted and twistloss can be totally compensated with slight excess of 0.74%. 相似文献
9.
Jie Xue Liang Chen Li Zhou Zhifeng Jia Yanping Wang Xinyuan Zhu Deyue Yan 《Journal of Polymer Science.Polymer Physics》2006,44(15):2050-2057
α‐Cyclodextrin (α‐CD) has been complexed with various poly(ethylene glycol) (PEG) derivatives in aqueous solution. It has been found that the end groups of PEG derivatives affect the complexation kinetics greatly, but have only a little influence on the thermodynamic behavior. By increasing the hydrophobicity of end groups, the complexation speeds up rapidly. On the other hand, the bulky end groups slow down the threading of polymeric guests into the cavity of CD. By changing the hydrophobicity and the size of end groups, the complexation rate can be adjusted in the range of several orders of magnitudes, which should be quite useful in the design of new supramolecular systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2050–2057, 2006 相似文献
10.
本文叙述了倍半萜类化合物——β-桉烯、衍生物Neointermedeol以及1,2,3,4,7,8-六氢-5,8-二甲基-3-异丙烯基萘的合成。初步药理筛选结果表明,这三个化合物均具有一定的抗生育活性。化合物还未见报道,它的化学结构在本文得到证实。 相似文献