全文获取类型
收费全文 | 1775篇 |
免费 | 85篇 |
国内免费 | 8篇 |
专业分类
化学 | 1342篇 |
晶体学 | 7篇 |
力学 | 31篇 |
数学 | 225篇 |
物理学 | 263篇 |
出版年
2023年 | 21篇 |
2022年 | 26篇 |
2021年 | 44篇 |
2020年 | 38篇 |
2019年 | 44篇 |
2018年 | 19篇 |
2017年 | 24篇 |
2016年 | 54篇 |
2015年 | 64篇 |
2014年 | 59篇 |
2013年 | 83篇 |
2012年 | 101篇 |
2011年 | 137篇 |
2010年 | 69篇 |
2009年 | 52篇 |
2008年 | 91篇 |
2007年 | 80篇 |
2006年 | 93篇 |
2005年 | 82篇 |
2004年 | 89篇 |
2003年 | 76篇 |
2002年 | 65篇 |
2001年 | 16篇 |
2000年 | 26篇 |
1999年 | 24篇 |
1998年 | 26篇 |
1997年 | 13篇 |
1996年 | 28篇 |
1995年 | 25篇 |
1994年 | 17篇 |
1993年 | 10篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 20篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1972年 | 6篇 |
1943年 | 6篇 |
排序方式: 共有1868条查询结果,搜索用时 15 毫秒
1.
2.
We discuss when a generic subspace of some fixed proportional dimension of a finite-dimensional normed space can be isomorphic to a generic quotient of some proportional dimension of another space. We show (in Theorem 4.1) that if this happens (for some natural random structures) then for any proportion arbitrarily close to 1, the first space has a lot of Euclidean subspaces and the second space has a lot of Euclidean quotients. 相似文献
3.
A self-consistent model of the development of dendrites and partial discharges in a dielectric solid under a variable voltage
is suggested. Dendrites originate at sites with the enhanced local field strength and also where the dielectric is broken
down under the action of partial discharges. The numerical simulation is used to quantitatively describe the space-time dynamics
of the dendrites and partial discharges in epoxy resin for the tip-plane electrode configuration. The simulated data are compared
with electrical measurements of partial discharges and with optical images of dendrite growth under the same conditions. 相似文献
4.
Nicole Mestrano 《Inventiones Mathematicae》1987,87(2):365-376
Sans résumé 相似文献
5.
P. Schwab A. Kochemasov R. Kullmer D. Bäuerle 《Applied Physics A: Materials Science & Processing》1992,54(2):166-169
Pulsed-laser deposition of YBa2Cu3O7 in N2O permits lowering of the substrate temperature with respect to deposition in O2 atmosphere. Additional photodissociation of N2O near the substrate surface deteriorates the superconducting properties of deposited films.On leave from: Institute of Applied Physics of the Academy of Sciences of the USSR, SU-603600 Nishni Nowgorod, USSR 相似文献
6.
C. Donzaud S. Czajkowski P. Armbruster M. Bernas C. Böckstiegel P. Dessagne H. Geissel E. Hanelt A. Heinz C. Kozhuharov C. Miehé G. Münzenberg M. Pfützner W. Schwab C. Stéphan K. Sümmerer L. Tassan-Got B. Voss 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):407-426
Projectile fission of 750 AMeV 238U-ions interacting with a Pb target was studied by means of the spectrometer FRS, GSI-Darmstadt. One of the two fission fragments
was detected with a transmission of few percent and identified in mass and charge. Low-energy fission (E* < 25 MeV) events were selected by their magnetic rigidity. Whereas the production of asymmetric fission events is dominated
by the GDR excitation, very asymmetric fission and symmetric fission take place after a GQR or DGDR excitation or after a
nuclear interaction. Cross sections of more than 250 isotopes were measured. Isotopic distributions of low-energy fission
were reconstructed for elements from Se to Te. The fission modes SI, SII and SL were clearly shown in these distributions
and in the mass and TKE distributions. Charge polarization and mass dispersion were deduced for each fission mode. Finally,
the characteristics of the low-energy fission process explain the production rates of neutron-rich species.
Received: 14 July 1997 / Revised version: 6 October 1997 相似文献
7.
BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES-X. SYNTHESES AND ANALYSES OF SULFONATED PHTHALOCYANINES 总被引:5,自引:0,他引:5
Hasrat Ali Réjean Langlois J. Richard Wagner Nicole Brasseur Benoit Paquette Johan E. VAN Lier 《Photochemistry and photobiology》1988,47(5):713-717
Abstract— Synthetic methods to obtain selectively sulfonated metallo phthalocyanines are compared. Both condensation and direct sulfonation procedures lead to mixtures of mono- to tetrasulfonated products which are resolved by reverse phase liquid chromatography in buffered aqueous-methanol. The proportion of sulfonated derivatives is examined as a function of the starting reagents in the case of the condensation method, and as a function of the temperature and reaction time in the case of the direct sulfonation procedure. The number of sulfonate groups per phthalocyanine molecule is determined by oxidative degradation of the phthalocyanine ring followed by quantitative chromatographic analysis of the sulfophthalamide and phthalamide fragments. 相似文献
8.
A comprehensive two-dimensional gas chromatography (GC x GC) instrument has been created by coupling a flow-switching modulator and a standard gas chromatograph. The instrument was used to characterize the aromatic composition of gasoline. The high-resolution separation produced by flow-switching GC x GC allowed gasoline aromatics to be fully resolved from saturated components. The aromatic compounds were further separated into groups having the same carbon number. A standard gasoline sample was analyzed to evaluate the quantitative accuracy and precision of this technique. The data show that flow-switching GC x GC produces results that are comparable to gas chromatography-mass spectrometry (GC-MS) and thermal modulation GC x GC. The simple, low-cost, and robust nature of flow-switching GC x GC makes it an ideal technique for the routine analysis of aromatic compounds in gasoline. 相似文献
9.
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
10.
JPC – Journal of Planar Chromatography – Modern TLC - The flavonoid and triterpenoid soyasaponin content of the aerial parts of Desmodium adscendens from four geographical origins of... 相似文献