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901.
A S Ratnayake W Y Yoshida S L Mooberry T K Hemscheidt 《The Journal of organic chemistry》2001,66(26):8717-8721
A new alkaloid, nomofungin, has been isolated from the fermentation broth of an unidentified endophytic fungus obtained from the bark of Ficus microcarpa L. The structure of nomofungin was determined by application of spectroscopic methods. The absolute stereochemistry of nomofungin was assigned by using the exciton chirality method. Nomofungin disrupts microfilaments in cultured mammalian cells and is moderately cytotoxic with minimum inhibitory concentrations (MICs) of 2 and 4.5 microg/mL against LoVo and KB cells, respectively. The ring system of nomofungin is unprecedented. 相似文献
902.
Treatment of optically active 1-chlorovinyl p-tolyl sulfoxides having two different substituents at the 2-position, which were synthesized from unsymmetrical ketones and (R)-(−)-chloromethyl p-tolyl sulfoxide in three steps, with cyanomethyllithium gave optically active 2-amino-1-cyano-5,5-disubstituted-1,3-cyclopentadienes with very high asymmetric induction from the sulfoxide chiral center. The products were converted to the enantiomerically pure 4,4-disubstituted 2-cyclopentenones by heating with phosphoric acid in acetic acid. 相似文献
903.
Tadashi Kawai Keiichiro Shiga Takehiko Suzuki Tomokazu Iyoda 《Journal of molecular catalysis. A, Chemical》1999,140(3):15-292
Tetravinylsilane and divinylsilanes have been successfully metathesized for the first time over Re2O7/Al2O3 catalyst promoted with tetrabutyltin under mild reaction conditions. All of the products were acyclic oligomers via intermolecular metathesis; the cyclic products via intramolecular metathesis were not formed. 相似文献
904.
Phase transitions of hexatriacontane (C36) and octacosane (C28), both as the solution grown single crystal (SGC) and polycrystalline aggregates (MCC) prepared by cooling at 1 K min–1 from the isotropic liquid state, were measured by the simultaneous DSC-FTIR method. MCC of C36 showed the freezing of the high temperature stable phase, which had a slight lower order of the lattice vibration mode comparing with the room temperature stable phase. MCC of C28 demonstrated thermo-reversible phase transition, however, had a binomial distribution of crystal stability of the monoclinic phase.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
905.
Yoshida H. Masuzaki M. Ooyama S. Ando R. Kamada K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(3):682-687
High-power broad-band millimeter-wave radiation is emitted from a plasma in a strong Langmuir turbulence state driven by an intense relativistic electron beam. We measured directivity and spectrum of this radiation with a filter-bank spectrometer, a heterodyne spectrometer, and a filter-waveguide-combination spectrometer covering 18-140 GHz. The directivity measurement indicated that the radiation was relativistically beamed. The observed spectra were nearly flat up to about 40 GHz and declined steeply above 40 GHz. Discussion is given on the experimental results in connection with the collective Compton boosting model proposed by Benford and Weatherall (1992) 相似文献
906.
907.
Luís A. S. De A. Prado Eduardo Radovanovic Heloise O. Pastore Inez V. P. Yoshida Iris L. Torriani 《Journal of polymer science. Part A, Polymer chemistry》2000,38(9):1580-1589
Poly(phenylsilsesquioxane) (PPSQ) polymers that were obtained from different synthetic routes were comparatively studied. The polymers were characterized by infrared and solid‐state 29Si NMR spectroscopies. According to the results of X‐ray diffraction and thermogravimetric analyses, the materials richest in silanol showed a less organized network and lower weight loss temperature. The morphology of the products was influenced by the preparation conditions. PPSQ, with a morphology rich in spherical particles, was achieved with an n‐hexadecyltrimethylammonium bromide template in the reaction medium, whereas the morphology of this polymer obtained in the absence of the template was featureless. Small‐angle X‐ray scattering analyses revealed that the PPSQ samples showed a predominance of surface‐fractal behavior. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1580–1589, 2000 相似文献
908.
Masanori Taguchi Ikuyoshi Tomita Yasuhiko Yoshida Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2001,39(4):495-499
An end‐π‐allylnickel macroinitiator ( 3 ) was prepared by the reaction of poly(ethylene glycol) allenyl methyl ether with an excess amount (5 equiv) of [(π‐allyl)NiOCOCF3]2 ( 1 ) in the presence of PPh3 ([PPh3]/[ 1 ] = 1). The resulting macroinitiator was used as an initiator for the polymerization of 1‐phenylethyl isonitrile ( 4a ) to give a block copolymer [poly(ethylene glycol)‐block‐poly( 4a )]. The molecular weight and composition of the block copolymers were controlled by the molecular weight of 3 and the ratio of 4a to 3 . © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 495–499, 2001 相似文献
909.
John Hendri Akihiro Hiroki Hiroyuki Oku Masaru Yoshida Ryoichi Katakai 《Journal of polymer science. Part A, Polymer chemistry》2001,39(1):56-62
The volume phase transition of nonionic hydrogels was controlled with a very small amount of variation (pinpoint variation) of the side chains far from the main chain. The copolymer hydrogels poly(methacryloyl‐alanine methyl ester‐co‐methacryloyl‐alanine ethyl ester) [poly(MA‐Ala‐OMe‐co‐MA‐Ala‐OEt)] and poly(methacryloyl‐alanine alkylamide‐co‐methacryloyl‐alanine ethyl ester) [poly(MA‐Ala‐NR2‐co‐MA‐Ala‐OEt)] were studied to investigate how pinpoint variation controls the volume phase transition. All copolymer hydrogels showed a volume phase transition from a swollen phase to a collapsed phase at a definite MA‐Ala‐OEt content at a specific temperature. The MA‐Ala‐OEt content at the midpoint of the transition linearly decreased with elevation of the temperature, and the decrease was larger for poly(MA‐Ala‐OMe‐co‐MA‐Ala‐OEt) than for poly(MA‐Ala‐NR2‐co‐MA‐Ala‐OEt). These results suggest that the association of the side chains controlling the swelling character of the hydrogels depends on the interacting ester–ester or ester–amide groups, and the former is larger than the latter. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 56–62, 2001 相似文献
910.
Here, we report the kinetic energy distributions (KEDs) of the fragment ions produced from multiply ionized ethane (C2H6) molecules in single electron capture collisions with 1.2 MeV C2+. To systematically investigate the fragmentation dynamics, the KEDs were obtained as functions of the charge state of the intermediate C2H6r+* ions r transiently generated prior to fragmentation. r was determined from coincidence measurement of the fragment ions and the number of emitted electrons. The KEDs are drastically different depending on the number of broken C–H bonds. The underlying causes are explained by the variation of the relative contributions of the multiply ionized states and preferential fragmentation pathways. For instance, CHn+ fragment ions with smaller n exhibit lower KEs because they are likely to be correlated with H+ emission, which carries away a large portion of the KE release. In addition, we report the KEDs of H3+ produced from doubly and triply charged states. 相似文献