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61.
62.
Matrix element of the Gallilean invariant nonrelativistic reduction of the pseudoscalar-pseudovector interaction has been
calculated for free pion absorption by a single nucleon inside the nucleus of16O. The Hartree-Fock wavefunctions obtained with the unitary-model-operator approach starting with the hard-core nucleon-nucleon
interaction have been used for the π-capturing nucleon in the initial state. The initial pion distortion in the presence of
nuclear field of the absorbing nucleus prior to its absorption together with the Coulomb interaction with the finite nuclear
size has been taken into account. The distortion of the emitted proton in the field of the residual nucleus has also been
considered. The differential cross-sections have been obtained and calculated results are compared with the previous experimental
and theoretical work. 相似文献
63.
报道了3-苯基-1-丁炔-3-醇的常规电子轰击质谱(EIMS)。利用碰撞诱导解离(CID)技术研究了质谱碎裂过程中产生的[C8H7]^+的气相离子结构。同时, 氘代同位素交换、亚稳(MI)和CID实验进一步证实了m/z 103离子的形成并不是分子离子的质谱碎裂中顺次失去甲基自由基和中性CO分子的直接氢迁移的协同反应, 而是在失去CO分子前后发生了二次质子迁移反应的逐步过程。在此基础上提出了一种独特的双分子质子键合复合物中间体的碎裂机理。 相似文献
64.
An investigation of heparinase immobilization 总被引:1,自引:0,他引:1
Bernstein Howard Yang Victor C. Langer Robert 《Applied biochemistry and biotechnology》1987,16(1):129-143
A systematic investigation of the parameters that affect the efficiency of immobilizing heparinase onto cyanogen bromide activated
crosslinked 8% agarose beads was conducted. Two experimental measures, the “fraction bound” and the “fraction retained,” were
used to monitor the coupling efficiency. The fraction bound is the portion of the total initial enzyme that is bound to the
agarose gel. The fraction retained is the fraction of bound enzyme that is active. The product of the two measures indicates
the coupling efficiency. The activity of the immobilized heparinase was measured under conditions free of both internal and
external mass transfer limitations, and thus, the fraction retained represents the true immobilized enzyme activity.
Increasing the degree of activation of the beads results in an increase in the fraction bound, the fraction retained, and
consequently, the coupling efficiency. As the ratio of enzyme solution to gel volume increases from 1.5 to 2.2, the fraction
bound remains constant but the fraction retained decreases (heparinase concentration; 0.15 mg/mL and degree of activation;
9.5 μmol of cyanate esters/g of gel). At volume ratios greater than 2.2, both the fraction bound and the fraction retained
decline continuously. Changing the heparinase concentration in the coupling solution changes the coupling efficiency in a
manner similar to that of the volume ratio change.
When heparin is added during the coupling process, the fraction bound declines as the heparin concentration increases, whereas
the fraction retained increases up to a heparin concentration of 12 mg/mL and decreases thereafter. When arginine, lysine,
and glycine are used to block the unreacted cyanate ester groups after the coupling process, the immobilized heparinase shows
different pH optima of 6.5, 6.9, and 7.2, respectively. Based upon these findings, a protocol to optimize heparinase immobilization
is developed. 相似文献
65.
The possibility of simultaneous application of an electron capture (ECD) and a flame ionization detector (FID) connected to a glass capillary column for analyzing polynuclear aromatic hydrocarbons (PNA) has been investigated. The ECD/FID ratio is determined for 46 PNA compounds. The ratios vary from 0.02 to 117 with relative standard deviations better than 20 percent determined from 10 replicate analyses. The results suggest that the method may be used for obtaining additional evidence in identifying PNA in environmental samples. Impurities and transformation products in the standard were identified by computerized glass capillary gas chromatography/mass spectrometry. Quinones and diones are responsible for the high EC-response determined in some trace components in the standard. An application of the method is shown for PNA from particulates in urban atmospheres. 相似文献
66.
Hirofumi Ono Hiroyuki Yamada Shigenobu Matsuda Kunihiko Okajima Takeshi Kawamoto Hideki Iijima 《Cellulose (London, England)》1998,5(4):231-247
An intensive study for aqueous microcrystalline cellulose (MCC) suspensions was carried out in view of the relationship between a viscosity and a 1H spin-spin relaxation time (T2) of water. An investigation was carried out for four suspension systems with the different particle size distributions. The proton mole ratio () of bound water against MCC particles and T2 of bound water (T2,b) were evaluated from the T2 values obtained by Carr-Purcell- Meiboom-Gill (C.P.M.G) method and those by solid echo method, respectively. As a result of these analyses, the T2,b value for the aqueous MCC suspension was evaluated as 5 × 10–3 s and it was found that the system having a larger tended to show a higher viscosity. By relating the above results to the observation of the suspensions by an optical microscope, it was concluded that a network formed by MCC particles plays an important role in generating a high viscosity of MCC suspension, and that an averaged mobility of water molecules is sensitively affected by the network structure. 相似文献
67.
N. T. Ul'chenko N. P. Bekker T. V. Chernenko N. K. Yuldasheva A. I. Glushenkova 《Chemistry of Natural Compounds》2003,39(3):249-252
Seed characteristics and the lipid and fatty-acid compositions were determined for the new cotton varieties ASh-25, Omad, 9771-I, Termez-43, and Bukhara-6. 相似文献
68.
69.
Weakly bound linear and bent dimers, FH—X (where X = CO, OC, CNH, NCH, N2O and ON2), are investigated using the DFT B3LYP and ab initio MP2 methods with the same basis sets (6–311++G(3df,2pd)). The strengths of the H—C or H—N H‐bonds in dimers FH—CO, FH—CNH, and FH—N2O are compared with those of the H—O or H—N H‐bonds in dimers FH—OC, FH—NCH, and FH—ON2. The results obtained for the H‐bond distances, the elongation effect of the HF bond, the red shift of the HF stretching frequency, and the energy difference between the dimer and the charge transfer reveal that the H‐bonds of the first group of dimers are stronger than those of the second. The Gibbs energies calculated for the six dimer formations indicate that the weakly bound dimers are unstable at room temperature (T = 298 K) (FH—X's → FH + X's, ΔG < 0). 相似文献
70.
We are dealing with a numerical method for solving the problem of minimizing a difference of two convex functions (a d.c. function) over a closed convex set in
n
. This algorithm combines a new prismatic branch and bound technique with polyhedral outer approximation in such a way that only linear programming problems have to be solved.Parts of this research were accomplished while the third author was visiting the University of Trier, Germany, as a fellow of the Alexander von Humboldt foundation. 相似文献