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91.
T. N. Srivastava R. C. Srivastava Mala Singh 《Journal of organometallic chemistry》1978,160(2):449-454
Iodine monohalides (ICl, IBr), cyanogen halides (CNBr, CNI) and thiocyanogen (SCN)2 add oxidatively to diaryltellurium(II), R2Te (R = Ph, p-Ch3OC6H4) under mild conditions (
°C). The resulting organotellurium(IV) derivatives react metathetically with silver pseudohalides to yield several new diaryltellurium(IV) pseudohalide derivatives. 相似文献
92.
Signs of the dipole moment derivatives, ?px/?S4 and ?px/?S5 where px is the dipole moment vector along an axis perpendicular to the CO bond in the plane of the molecule and Sj are the symmetry coordinates for the B1 vibrations of Br2CO have been re-evaluated from the reported ?p/?Qi values (p being the dipole moment of the molecule and Qi the normal coordinates) and the L matrix elements. The new set of dipole moment derivatives fits well with similar parameters for Cl2CO and F2CO. 相似文献
93.
Summary The complexes Pd(PTH)2Cl2 · 3.5 H2O, Pd(PTH)3(PPh3), Ru(PTH)2(PPh3)Cl2, Ru(PTH)2(PPh3)Cl3, Rh(PTH)2(PPh3)Cl and Rh(PT)Cl2 · 0.5 H2O, where PTH isN-phenylcarbamoylpyrrole-2-thiocarboxamide, have been prepared and characterised by magnetic and spectral (i.r., u.v. and visible) studies. 相似文献
94.
Synthesis of a BQQ-neomycin conjugate is reported. The conjugate combines two ligands, one known to intercalate triplexes (BQQ) and another known to bind in the triplex groove (neomycin). The conjugate stabilizes T.A.T, as well as mixed base DNA triplex, better than neomycin, BQQ, or a combination of both. The conjugate selectively stabilizes the triplex (in the presence of physiological salt concentrations), with as little as 4 muM of the ligand leading to a DeltaTm of >60 degrees C. Competition dialysis studies show a clear preference for the drug binding to triplex DNA/RNA over the duplex/single strand structures. Modeling studies suggest a structure of neomycin bound to the larger W-H (Watson-Hoogsteen) groove with BQQ intercalated between the triplex bases. 相似文献
95.
The incorporation of (±)-norcoclaurine, (±)-coclaurine, (±)-N-methylcoclaurine and dehydro-N-methylcoclaurine into nortiliacorinine A in Tiliacora racemosa colebr has been studied and specific utilisation of the (±)-coclaurine demonstrated. The evidence supports oxidative dimerization of two coclaurine units to give nortiliacorinine A. Experiments with (±)-N-methylcoclaurine and (±)-[1-3H, N-14CH3]N-methylcoclaurine established that only one N-methylcoclaurine unit is specifically utilised to constitute that “half” of the base which had phenolic OH group in the benzylic portion and further demonstrated that the H atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion into nortiliacorinine A. Double labelling experiment with (±)-[1-3H, 6,0-14CH3]N-methylcoclaurine showed that O-Me function of the precursor is lost in the bioconversion into nortiliacorinine A. Parallel feedings of (+)-(S)- and (-)-(R)-N-methyl-coclaurines and (-)-(S)-, and ( + )-(R)-coclaurines revealed that the stereo-specificity is maintained in the biosynthesis of nortiliacorinine A from 1-benzylisoquinoline precursors and established ‘S,S’-configuration at the two asymmetric centres in nortiliacorinine A. 相似文献
96.
The specifically designed reagent, 4-tButyl iodoxybenzene (1)-soluble in hot, benzene, chlorobenzene and nitrobenzene- cleaves a range of π bonds to carbonyl compounds in 50–75% isolated yields. In every case, the reagent 1 is transformed to 4-tbutyl iodobenzene (2) in 90–97% yields, which can be recycled. 相似文献
97.
A single crystal X-ray analysis has confirmed the constitution and established the stereochemistry of the triterpene, malabaricol. 相似文献
98.
Human antibody 2G12 broadly neutralizes human immunodeficiency virus type 1 (HIV-1) isolates and shows protective activity against viral challenge in animal models. Previous mutational analysis suggested that 2G12 recognized a novel cluster of high-mannose type oligosaccharides on HIV-1 gp120. To explore the carbohydrate antigen for HIV-1 vaccine design, we have studied the binding of 2G12 to an array of HIV-1 high-mannose type oligosaccharides by competitive ELISAs and found that Man9GlcNAc is 210- and 74-fold more effective than Man5GlcNAc and Man6GlcNAc in binding to 2G12. The results establish that the larger high-mannose oligosaccharide on HIV-1 is the favorable subunit for 2G12 recognition. To mimic the putative epitope of 2G12, we have created scaffold-based multivalent Man9 clusters and found that the galactose-scaffolded bi-, tri-, and tetra-valent Man9 clusters are 7-, 22-, and 73-fold more effective in binding to 2G12 than the monomeric Man9GlcNAc2Asn. The experimental data shed light on further structural optimization of epitope mimics for developing a carbohydrate-based HIV-1 vaccine. 相似文献
99.
K. Lal 《Monatshefte für Chemie / Chemical Monthly》1983,114(1):33-36
Reactions of trimethylchlorosilane (Me 3SiCl) with some nitrogen donors viz. pyridine, 2-, 3- and 4-picolines, quinoline and isoquinoline in nitrobenzene have been studied conductometrically. The conductivities of the solutions during these reactions have been interpreted in terms of the formation of (Me 3Si.D)+, (Me 3SiCl2)? andMe 3SiCl.D (D=N-donor molecule) species. 相似文献
100.
Sayed Ali Naghi Taheri R. Alan Jones Santokh Singh Badesha Majed M. Hania 《Tetrahedron》1989,45(24):7717-7728
3,4-Diformyl-2,5-dimethylpyrrole (1) reacts with ,ω-diamino-alkanes, NH2(CH2)nNH2t' to form either the potentially tautomeric 2:2 macrocyclic adduct (7a) (8), when N = 2, or the potentially tautomeric 1:1 bicyclic adduct (18) (19), when N = 4, 5, 6, and 12. 1H and 13C N.m.r. spectral data indicate that the 2-azafulvene structures predominate for both types of cycloadducts. Only polymeric material was obtained when N = 3. 相似文献