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991.
To explore the anion recognition ability of silanol derivatives, ESI-MS and 1H NMR titrations of a 1,3-disiloxanediol 1 with anions were studied in CDCl3 and MeCN-d3. The results indicate that 1 showed strong binding to anions such as AcO− and halides. 相似文献
992.
Zengwei Luo 《Tetrahedron letters》2007,48(10):1753-1756
Two benzo[de]isoquinoline 1,3-dione amino acids 1 and 2 were readily prepared, and their enantiodiscriminating ability were investigated by 1H NMR spectroscopy. It was found that 1 exhibited an excellent chiral recognition ability toward chiral α-phenylethylamine and some of its derivatives, leading to clear baseline separation of the multiplet of the probe groups in two enantiomers. The stoichiometric ratio and association constants of some host-guest complexes were determined. The interactions between the hosts and guest 3 were further studied by intermolecular NOE experiment and ESI-MS. 相似文献
993.
A novel photochromic Schiff base derivative, 5,17-N,N′-(5,5′-di-methoxyl-benzlaldehyde)diimine-25,27-dipropoxy-calix[4]arene has been synthesized through incorporation of two imine groups into the upper rims of calix[4]arene. The experiments showed that the addition of Dy3+ or Er3+ ions to compound 4 results in the solution color change, but other metal ions caused less change. It indicated that the synthetic receptor can selectively recognize Dy3+ and Er3+ ion by naked eye over other lanthanide cations. Thus, these systems can be applied as chemosensor for Dy3+ and Er3+ ion in analytical chemistry. 相似文献
994.
Surface plasmon resonance sensor for lysozyme based on molecularly imprinted thin films 总被引:1,自引:0,他引:1
Molecularly imprinted polymers (MIPs) selective for lysozyme were prepared on SPR sensor chips by radical co-polymerization with acrylic acid and N,N′-methylenebisacrylamide. Gold-coated SPR sensor chips were modified with N,N′-bis(acryloyl)cystamine, on which MIP thin films were covalently conjugated. The presence of NaCl during the polymerization and the re-binding tests affected the selectivity and the optimization of NaCl concentration in the pre-polymerization mixture and the re-binding buffer could enhance the selectivity in the target protein sensing. When the lysozyme-imprinted polymer thin films were prepared in the presence of 40 mM NaCl, the selectivity factor (target protein bound/reference protein bound) of MIP in the re-binding buffer containing 20 mM NaCl was 9.8, meanwhile, that of MIP in the re-binding buffer without NaCl was 1.2. A combination of SPR sensing technology with protein-imprinted thin films is a promising tool for the construction of selective protein sensors. 相似文献
995.
Kondepati VR Oszinda T Heise HM Luig K Mueller R Schroeder O Keese M Backhaus J 《Analytical and bioanalytical chemistry》2007,387(5):1633-1641
We have investigated the application of near-infrared spectroscopy for detection of human primary pancreatic and colorectal
cancers. Spectra from cancerous and normal tissue were collected from a total of 37 surgically resected pancreatic and colorectal
patient tissue specimens using a fibre-optic probe. Major spectral differences were observed in the CH-stretching first (6,000–5,400 cm−1) and second overtone (9,000–7,900 cm−1) regions. By use of artificial neural networks, linear discriminant analysis, and cluster analysis as pattern-recognition
methods the spectra were classified into cancerous and normal tissue groups with accuracy up to 89%. We also explored differences
between the spectra obtained from colorectal and pancreatic tissue. Spectral data from cancerous and normal tissue were classified
organ-specifically into four groups with accuracy between 80 and 83%. Our results indicate that CH-overtone regions, besides
serving as diagnostic markers for NIR spectroscopic diagnosis of primary human pancreas and colorectal cancers, are also useful
for elucidating differences between the spectra obtained from colorectal and pancreatic cancerous tissue. 相似文献
996.
Chiral discrimination of alpha-amino acids by the DNA triplet GCA using amino acids as a co-selector
Kumar MR Prabhakar S Sivaleela T Vairamani M 《Journal of mass spectrometry : JMS》2007,42(9):1218-1224
The DNA triplet GCA is successfully used as a chiral selector for the chiral discrimination of amino acids using amino acids themselves as a co-selector. Chiral discrimination was achieved by investigating the collision-induced dissociation spectra of the [X(A) + X(R) + 2Y - 2H](2-) ion generated by electrospraying a mixture of analyte amino acid (X(A)), reference amino acid (X(R)) and GCA (Y). The relative abundances of fragment ions resulting from the competitive loss of reference and X(A)'s are considered for measuring the degree of chiral discrimination. GCA successfully shows D-selectivity for all the amino acids, except Tyr and Lys. The success of the method lies in the selection of a suitable 10(R) that has closer GCA binding affinity to that of analyte. The degree of discrimination by GCA is improved in the presence of the reference, and the chirality of the reference does not change the selectivity of GCA. The suitability of the method for the measurement of optical purity is also demonstrated. 相似文献
997.
Taleb RI Jaramillo D Wheate NJ Aldrich-Wright JR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(11):3177-3186
Two DNA-sequence-selective hairpin polyamide platinum(II) complexes, containing pyrrole and imidazole heterocyclic rings, have been synthesised by different methods. A six-ring complex, selective for (A/T)GGG(A/T) DNA sequences, was made by using solid-phase synthesis, whilst an eight-ring complex, selective for (A/T)CCTG(A/T) DNA sequences, was made by utilising standard wet chemistry. Solid-phase synthesis resulted in a significantly higher yield, required less purification and is more efficient than the wet synthesis; as such, it is the preferred method for further work. The metal complexes were characterised by (1)H and (195)Pt NMR spectroscopy and ESI mass spectrometry. The two compounds provide a foundation for the synthesis of more complex molecules containing multiple hairpins and/or platinum groups. 相似文献
998.
Amendola V Colasson B Fabbrizzi L Rodriguez Douton MJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(17):4988-4997
Dicationic ligands incorporating two 2,2'-bipyridine units and two imidazolium moieties, [1](2+) and [2](2+), form stable chelate complexes with Cu(II) and Cu(I) in acetonitrile solution. Each Cu(II) complex binds two X(-) ions according to two stepwise equilibria, the first involving the Cu(II) centre and the second involving the bis-imidazolium compartment. Cu(I) complexes are able to host only one NO(3)(-) ion in the bis-imidazolium cavity, while other anions induce demetallation. Thus, in the presence of one equivalent of NO(3)(-), the Cu(II)/Cu(I) redox change makes the anion translocate quickly and reversibly from one binding site to the other within the [Cu(II,I)(1)](4+/3+) system, as demonstrated by cyclic voltammetry and controlled-potential electrolysis experiments. 相似文献
999.
Berni E Kauffmann B Bao C Lefeuvre J Bassani DM Huc I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(30):8463-8469
We report on the dramatic effect of increasing helix diameter on the hybridization of oligopyridine-dicarboxamide strands into double helices. Upon replacing a single pyridine by a 1,8-diazaanthracene unit within an oligomeric strand, a 4.7 A enlargement of the helix diameter occurs parallel to the long anthracene axis. This structure change results in a spectacular stabilization of the double helical hybrids derived from these strands (factors of over 10(7)). Detailed investigations of the hybridization process using X-ray crystallography, NMR, fluorescence measurements and molecular mechanics calculations allowed us to assign the duplex stabilization to two enthalpic effects. First, the increase in diameter results in an augmented surface, involved in intermolecular pi-pi stacking. Second, the enlarged diameter leads to a lower tilt angle of the helical strand, with respect to the helix axis, which in turn results in smaller dihedral angles at the aryl-amide linkages and thus a considerably lowered enthalpic cost of the spring-like extension of the strands during the hybridization process. These results provide novel insights into how subtle tuning of molecular components may result in considerable and rationalizable changes in double helical supramolecular architectures. 相似文献
1000.
Fürstenberg A Deligeorgiev TG Gadjev NI Vasilev AA Vauthey E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(30):8600-8609
The fluorescence enhancement mechanisms of a series of DNA stains of the oxazole yellow (YO) family have been investigated in detail using steady-state and ultrafast time-resolved fluorescence spectroscopy. The strong increase in the fluorescence quantum yield of these dyes upon DNA binding is shown to originate from the inhibition of two distinct processes: 1) isomerisation through large-amplitude motion that non-radiatively deactivates the excited state within a few picoseconds and 2) formation of weakly emitting H-dimers. As the H-dimers are not totally non-fluorescent, their formation is less efficient than isomerisation as a fluorescent contrast mechanism. The propensity of the dyes to form H-dimers and thus to reduce their fluorescence contrast upon DNA binding is shown to depend on several of their structural parameters, such as their monomeric (YO) or homodimeric (YOYO) nature, their substitution and their electric charge. Moreover, these parameters also have a substantial influence on the affinity of the dyes for DNA and on the ensuing sensitivity for DNA detection. The results give new insight into the development and optimisation of fluorescent DNA probes with the highest contrast. 相似文献