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921.
Pribil PA Patton E Black G Doroshenko V Fenselau C 《Journal of mass spectrometry : JMS》2005,40(4):464-474
New and improved strategies are eagerly sought for the rapid identification of microorganisms, particularly in mixtures. Mass spectrometry remains a powerful tool for this purpose. Small acid-soluble proteins (SASPs), which are relatively abundant in Bacillus spores, represent potential biomarkers for species characterization. Despite sharing extensive sequence homology, these proteins differ sufficiently in sequence for discrimination between species. This work focuses on the differences in sequence between SASPs from various Bacillus species. Compilation of SASP sequences from protein database searches, followed by in silico trypsin digestion and analysis of the resulting fragments, identified several species-specific peptides that could be targeted for analysis using mass spectrometry. This strategy was tested and found to be successful in the characterization of Bacillus spores both from individual species and in mixtures. Analysis was performed using an ion trap mass spectrometer with an atmospheric pressure MALDI source. This instrumentation offers the advantage of increased speed of analysis and accurate precursor ion selection for tandem mass spectrometric analysis compared with vacuum matrix-assisted laser desorption/ionization and time-of-flight instruments. The identification and targeting of species-specific peptides using this type of instrumentation offers a rapid, efficient strategy for the identification of Bacillus spores and can potentially be applied to different microorganisms. 相似文献
922.
Antonopoulos A Favetta P Jacquinet JC Lafosse M 《Journal of mass spectrometry : JMS》2005,40(12):1628-1636
Carbohydrate-protein linkage region of proteoglycans is a key oligosaccharide structure because their sulphated and/or phosphorylated analogues control the biosynthesis of glucosaminoglycans or galactosaminoglycans. Therefore, synthesised sulphated and/or phosphorylated analogues were characterised by tandem mass spectrometry in the negative-ion mode. Results demonstrated that the product ion profile was characterised by glycosidic and cross-ring cleavages depending on the position and the type of the charged group (sulphate, phosphate or carboxylate). When the above compounds were sulphated and phosphorylated, the ion found at m/z 79 was the only one that demonstrated a phosphate group on the structure. The data also suggested that when a sodium cation was present in a sulphated and phosphorylated structure, the phosphate group in most cases was neutralised by the sodium cation, and therefore cleaved off the molecule, while the sulphate group was carrying the negative charge. 相似文献
923.
Wilson SM Wiberg KB Cheeseman JR Frisch MJ Vaccaro PH 《The journal of physical chemistry. A》2005,109(51):11752-11764
Cavity ring-down polarimetry (CRDP) has been exploited to interrogate the nonresonant optical activity (or circular birefringence) of prototypical organic compounds in the vapor phase, thereby revealing the intrinsic chiro-optical response evoked from isolated (solvent-free) molecules. Specific polarization rotation parameters have been measured at two distinct excitation wavelengths (355 nm and 633 nm) for a variety of gas-phase species drawn from the terpene, epoxide, and alkane/alkene families, with complementary solution-phase polarimetric studies serving to highlight the pronounced influence of solute-solvent interactions. Time-dependent linear response calculations performed at high levels of density functional theory have been enlisted to unravel the structural and electronic origins for observed behavior. Aside from elucidating the complex solvation processes that mediate chiro-optical phenomena taking place in condensed media, this study affords a critical assessment for emerging ab initio predictions of nonresonant optical activity and for their promising ability to assist in the determination of absolute molecular stereochemistry. 相似文献
924.
An intermolecular ring expansion reaction of an aryl epoxide with several dienes, acrylates, enynes or styrenes under iron catalysis, generated tetrahydrofuran derivatives in a highly chemo- and regioselective fashion. The process could be used in an unprecedented way for the one step synthesis of racemic calyxolane A and calyxolane B with acceptable diastereoselectivity. 相似文献
925.
Langley SJ Helliwell M Sessoli R Rosa P Wernsdorfer W Winpenny RE 《Chemical communications (Cambridge, England)》2005,(40):5029-5031
The synthesis, structural and magnetic characterisation of a new polymetallic cobalt complex are reported; the magnetic behaviour is unusual. 相似文献
926.
927.
Riemann Existence Theorems for Galois covers of Mumford curves by Mumford curves are stated and proven. As an application, all finite groups are realised as full automorphism groups of Mumford curves in characteristic zero. 相似文献
928.
We discuss the existence and uniqueness in H1(N) and the H2(N) regularity of the solutions of Au=f when f L2(N) and A is a second-order linear elliptic operator whose first and zeroth order coefficients may be unbounded at infinity. We also investigate whether –A generates a C0 or analytic semigroup on L2. The approach in this nonweighted setting is based on a new and general method. The idea consists in embedding A into a suitable one-parameter family of operators (As)s with A0=A. The properties of As when s0 make it possible to prove that the boundary integrals arising from simple integration by parts over balls with increasing radius tend to 0 at infinity. This provides the needed estimates for uniqueness and regularity.Mathematics Subject Classification (1991): 35D05, 35D10, 35J15 相似文献
929.
Patrick X. Gallagher 《Mathematische Zeitschrift》1967,102(3):236-237
930.
Patrick Coffey 《International journal of quantum chemistry》1974,8(2):263-266
The two-center core-electron attraction integral VAB in zero-differential overlap semiempirical MO methods is examined. It is concluded that core-valence orthogonality and valence symmetrical orthogonalization effects must be considered, and that these effects provide justification for the CNDO /2 approximation VAB = ZBγAB. 相似文献