全文获取类型
收费全文 | 13255篇 |
免费 | 425篇 |
国内免费 | 71篇 |
专业分类
化学 | 9256篇 |
晶体学 | 147篇 |
力学 | 422篇 |
综合类 | 1篇 |
数学 | 1451篇 |
物理学 | 2474篇 |
出版年
2022年 | 89篇 |
2021年 | 184篇 |
2020年 | 185篇 |
2019年 | 171篇 |
2018年 | 148篇 |
2017年 | 113篇 |
2016年 | 296篇 |
2015年 | 281篇 |
2014年 | 299篇 |
2013年 | 655篇 |
2012年 | 753篇 |
2011年 | 840篇 |
2010年 | 475篇 |
2009年 | 363篇 |
2008年 | 707篇 |
2007年 | 739篇 |
2006年 | 765篇 |
2005年 | 727篇 |
2004年 | 612篇 |
2003年 | 516篇 |
2002年 | 463篇 |
2001年 | 230篇 |
2000年 | 203篇 |
1999年 | 160篇 |
1998年 | 152篇 |
1997年 | 201篇 |
1996年 | 241篇 |
1995年 | 156篇 |
1994年 | 176篇 |
1993年 | 198篇 |
1992年 | 165篇 |
1991年 | 99篇 |
1990年 | 92篇 |
1989年 | 122篇 |
1988年 | 125篇 |
1987年 | 104篇 |
1986年 | 110篇 |
1985年 | 157篇 |
1984年 | 141篇 |
1983年 | 103篇 |
1982年 | 127篇 |
1981年 | 106篇 |
1980年 | 91篇 |
1979年 | 98篇 |
1978年 | 101篇 |
1977年 | 97篇 |
1976年 | 79篇 |
1975年 | 98篇 |
1974年 | 94篇 |
1973年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
81.
82.
Eric Cancès Renaud Keriven François Lodier Andreas Savin 《Theoretical chemistry accounts》2004,111(2-6):373-380
Efficient formulas for computing the probabilities of finding exactly electrons in an arbitrarily chosen volume 3 for Hartree–Fock wavefunctions are presented. These formulas allow the use of shape optimization techniques, such as level set methods, for optimizing with respect to various criteria involving such probabilities. The criterion defined as the difference between the Hartree–Fock and the independent-particle model probabilities of finding electrons in stresses the quantum effects due to the Pauli principle. We have implemented a 2D level set method for optimizing this criterion in order to study spatial separation of electron pairs in linear molecules. The method is described and the illustrative example of the BH molecule is reported.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
83.
84.
Doshi DA Shah PB Singh S Branson ED Malanoski AP Watkins EB Majewski J van Swol F Brinker CJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):7805-7811
Neutron reflectivity (NR) is used to probe the solid, liquid, vapor interface of a porous superhydrophobic (SH) surface submerged in water. A low-temperature, low-pressure technique was used to prepare a rough, highly porous organosilica aerogel-like film. UV/ozone treatments were used to control the surface coverage of hydrophobic organic ligands on the silica framework, allowing the contact angle with water to be continuously varied over the range of 160 degrees (superhydrophobic) to <10 degrees (hydrophilic). NR shows that the superhydrophobic nature of the surface prevents infiltration of water into the porous film. Atomic force microscopy and density functional theory simulations are used in combination to interpret the NR results and help establish the location, width, and nature of the SH film-water interface. 相似文献
85.
Dunahay Terri G. Jarvis Eric E. Dais Sonja S. Roessler Paul G. 《Applied biochemistry and biotechnology》1996,57(1):223-231
Applied Biochemistry and Biotechnology - Genetic transformation of two species of diatoms has been accomplished by introducing chimeric plasmid vectors containing a bacterial antibiotic resistance... 相似文献
86.
87.
Nicole Fietkau Fran?ois G Chevallier Li Jiang Timothy G J Jones Richard G Compton 《Chemphyschem》2006,7(10):2162-2167
The size of a glass sphere positioned in the center of a microdisk electrode is determined by using a simple electrochemical procedure and is confirmed, additionally, by a microscopical measurement of the sphere at the time of the electrochemical measurement. The cyclic voltammetric response of the naked electrode and of the electrode with the sphere positioned in its center is recorded over a wide range of scan rates (0.002-1.5 V s(-1)). The size of the sphere is then determined by comparison of the experimental voltammogram with simulations for each individual scan rate. 相似文献
88.
89.
90.
Shi Nian-Qing Prahl Kristine Hendrick Jim Cruz Jose Lu Ping Cho Jae-Yong Jones Sharon Jeffries Thomas 《Applied biochemistry and biotechnology》2000,84(1-9):201-216
Pichia stipitis CBS 6054 will grow on d-xylose, d-arabinose, and l-arabinose. d-Xylose and l-arabinose are abundant in seed hulls of maize, and their utilization is important in processing grain residues. To elucidate
the degradation pathway for l-arabinose, we obtained a mutant, FPL-MY30, that was unable to grow on d-xylose and l-arabinose but that could grow on d-arabinitol. Activity assays of oxidoreductase and pentulokinase enzymes involved in d-xylose, d-arabinose, and l-arabinose pathways indicated that FPL-MY30 is deficient in d-xylitol dehydrogenase (D-XDH), d- and l-arabinitol dehydrogenases, and d-ribitol dehydrogenase. Transforming FPL-MY30 with a gene for xylitol dehydrogenase (PsXYL2), which was cloned from CBS 6054 (Gen Bank AF127801), restored the D-XDH activity and the capacity for FPL-MY30 to grow on
l-arabinose. This suggested that FPL-MY30 is critically deficient in XYL2 and that the d-xylose and l-arabinose metabolic pathways have xylitolas a common intermediate. The capacity for FPL-MY30 to grow on d-arabinitol could proceed through d-ribulose. 相似文献