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991.
Point D Davis WC Christopher SJ Ellisor MB Pugh RS Becker PR Donard OF Porter BJ Wise SA 《Analytical and bioanalytical chemistry》2007,387(7):2343-2355
An accurate, ultra-sensitive and robust method for speciation of mono, di, and tributyltin (MBT, DBT, and TBT) by speciated isotope-dilution gas chromatography-inductively coupled plasma-mass spectrometry (SID-GC-ICPMS) has been developed for quantification of butyltin concentrations in cryogenic biological materials maintained in an uninterrupted cryo-chain from storage conditions through homogenization and bottling. The method significantly reduces the detection limits, to the low pg g(-1) level (as Sn), and was validated by using the European reference material (ERM) CE477, mussel tissue, produced by the Institute for Reference Materials and Measurements. It was applied to three different cryogenic biological materials-a fresh-frozen mussel tissue (SRM 1974b) together with complex materials, a protein-rich material (whale liver control material, QC03LH03), and a lipid-rich material (whale blubber, SRM 1945) containing up to 72% lipids. The commutability between frozen and freeze-dried materials with regard to spike equilibration/interaction, extraction efficiency, and the absence of detectable transformations was carefully investigated by applying complementary methods and by varying extraction conditions and spiking strategies. The inter-method results enabled assignment of reference concentrations of butyltins in cryogenic SRMs and control materials for the first time. The reference concentrations of MBT, DBT, and TBT in SRM 1974b were 0.92 +/- 0.06, 2.7 +/- 0.4, and 6.58 +/- 0.19 ng g(-1) as Sn (wet-mass), respectively; in SRM 1945 they were 0.38 +/- 0.06, 1.19 +/- 0.26, and 3.55 +/- 0.44 ng g(-1), respectively, as Sn (wet-mass). In QC03LH03, DBT and TBT concentrations were 30.0 +/- 2.7 and 2.26 +/- 0.38 ng g(-1) as Sn (wet-mass). The concentration range of butyltins in these materials is one to three orders of magnitude lower than in ERM CE477. This study demonstrated that cryogenically processed and stored biological materials are a promising alternative to conventional freeze-dried materials for organotin speciation analysis, because these are, at present, the best conditions for minimizing degradation of thermolabile species and for long-term archival. Finally, the potential of the analytical method was illustrated by analysis of polar bear (Ursus maritimus) and beluga whale (Delphinapterus leuca) liver samples that had been collected in the Arctic and archived at the Marine Environmental Specimen Bank. Significant concentrations of butyltin compounds were found in the samples and provide the first evidence of the presence of this class of contaminant in the Arctic marine ecosystem. Figure Eye catch image. 相似文献
992.
Standard reference materials for foods and dietary supplements 总被引:1,自引:0,他引:1
Sharpless KE Thomas JB Christopher SJ Greenberg RR Sander LC Schantz MM Welch MJ Wise SA 《Analytical and bioanalytical chemistry》2007,389(1):171-178
Well-characterized certified reference materials are needed by laboratories in the food testing, dietary supplement, and nutrition
communities to facilitate compliance with labeling laws and improve the accuracy of information provided on product labels,
so that consumers can make good choices. As a result of the enactment of the Nutrition Labeling and Education Act of 1990
and the Infant Formula Act of 1980, the National Institute of Standards and Technology (NIST) worked to develop a series of
food-matrix standard reference materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids
and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM
1846 Infant Formula, SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue, SRM 2383 Baby Food Composite,
SRM 2384 Baking Chocolate, SRM 2385 Slurried Spinach, and SRM 2387 Peanut Butter. With the enactment of the Dietary Supplement
Health and Education Act of 1994, NIST has been working to develop suites of dietary supplement SRMs characterized for active
and marker compounds and for toxic elements and pesticides, where appropriate. An updated SRM 1588b Organics in Cod Liver
Oil, a suite of ephedra-containing materials (SRMs 3240–3245), a carrot extract in oil (SRM 3276), and a suite of ginkgo-containing
materials (SRMs 3246–3248) are available. Several other materials are currently in preparation. Dietary supplements are sometimes
provided in forms that are food-like; for these, values may also be assigned for nutrients, for example SRM 3244 Ephedra-Containing
Protein Powder. Both the food-matrix and dietary supplement reference materials are intended primarily for validation of analytical
methods. They may also be used as “primary control materials” in assignment of values to in-house (secondary) control materials
to confirm accuracy and to establish measurement traceability to NIST. 相似文献
993.
We give a very general completion theorem for pro-spectra. We show that, if G is a compact Lie group, M[∗] is a pro-G-spectrum, and F is a family of (closed) subgroups of G, then the mapping pro-spectrum F(EF+,M[∗]) is the F-adic completion of M[∗], in the sense that the map M[∗]→F(EF+,M[∗]) is the universal map into an algebraically F-adically complete pro-spectrum. Here, F(EF+,M[∗]) denotes the pro-G-spectrum , where runs over the finite subcomplexes of EF+. 相似文献
994.
The feasibility of developing a multi-component bioanalytical method using high-field asymmetric waveform ion mobility spectrometry coupled with liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-FAIMS-MS/MS) is demonstrated using nefazodone and its two metabolites as model compounds. The performance of the bioanalytical method for the three analytes, with three different compensation voltage (CV) values, is assessed using standard curves and quality control samples, which exhibited good accuracy, precision and ruggedness. The number of analytes with different CV values that can be quantitated simultaneously depends on the acquisition cycle time, which is a function of the FAIMS residence time (fixed), chromatographic peak width and selected reaction monitoring (SRM) dwell time. It is established that CV, the FAIMS selectivity parameter, is reproducible for at least 16 h, thus ensuring the constancy of the CV during a large-batch sample analysis. It is also established that change in mobile phase composition or of flow rate does not cause a shift in CV. Thus, CV values determined from a CV scan via infusion of a sample can be used for an LC/ESI-FAIMS-M/MS method based on isocratic or gradient elution. 相似文献
995.
The ability of Listeria monocytogenes to attach to various food contact surfaces, such as stainless steel, polypropylene, and rubber compounds, is well documented. The retention of these or other pathogenic bacteria on food contact surfaces increases the risk of transmission to food products. The objective of this study was to compare several methods for quantitative recovery of Listeria monocytogenes from stainless steel surfaces. A cocktail of 4 serotypes of Listeria monocytogenes mixed in equivalent concentrations was inoculated onto type 304 stainless steel coupons in a 2 x 2 cm area. After 1 h exposure, coupons were sampled by one of the following methods: (1) swabbing with a premoistened Dacron swab; (2) rinsing with phosphate-buffered saline; (3) direct contact onto tryptic soy agar containing 0.6% yeast extract (TSA + YE) plates for 10 s; (4) sonication in an ultrasonic water bath (40 kHz); (5) contact with the bristles of a sonicating brush head for 1 min; and (6) indirect contact (2-4 mm distance) with a sonicating brush head for 1 min. The 3 sonication methods yielded higher recovery than the other 3 methods (P < 0.05). Brushing the coupons with the sonicating brush head (contact or noncontact) yielded a recovery level of about 60%. The lowest cell recovery (about 20%) was observed with the swab and direct agar contact methods. After a 12 h exposure, recoveries ranged from 17.4 (brush contact method) to 2% (swab method). 相似文献
996.
Fungal cells treated with various inhibitors to the ergosterol pathway were analyzed using an Orbitrap mass spectrometer equipped with an atmospheric solids analysis probe (ASAP). The technique is a rapid means for determining which of the multiple steps in the ergosterol pathway were interrupted by an inhibitor. Furthermore, in an inhibitor concentration study, the ASAP method was able to rapidly provide an estimate of the effectiveness of inhibition. In this method the cells are inserted directly into a hot nitrogen stream, thus eliminating extensive sample workup before analysis. Data indicating the point of pathway interruption are obtained in seconds. 相似文献
997.
Donald SM Macgregor SA Settels V Cole-Hamilton DJ Eastham GR 《Chemical communications (Cambridge, England)》2007,(6):562-564
Density functional calculations suggest that intermolecular attack of methanol may be important in the methanolysis of simple Pd-acyl systems and that the energetics of this process are strongly dependent on the metal coordination environment. 相似文献
998.
A novel "high throughput" technique for LCST measurement was developed which is able to identify the effect of subtle changes in end group composition on the aqueous phase behaviour of water-soluble poly(2-(dimethylamino)ethyl methacrylate). 相似文献
999.
Stevenson S Mackey MA Thompson MC Coumbe HL Madasu PK Coumbe CE Phillips JP 《Chemical communications (Cambridge, England)》2007,(41):4263-4265
The yield of Sc3N@C80 metallofullerene and fullerene extract is dramatically increased via filling cored graphite rods with copper and Sc2O3 only; when compared to 100% Sc2O3 packed rods, improvements of factors of approximately 3 and approximately 5 have been achieved for Sc3N@C80 and fullerene extract produced, respectively, with the weight percent of Cu added to the rod affecting the type and amount of fullerene produced. 相似文献
1000.