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991.
Summary SummaryYeast cultures progressing from the exponential to the stationary phase of growth showed changes in cell sensitivity to physical agents such as UV light, heat shock at 52° C and the chemical mutagens ethyl methane sulphonate, nitrous acid and mitomycin C.Exponential phase cells showed maximum resistance to UV light and minimum resistance to heat shock and the three chemicals. The increased resistance of exponential phase cells to UV light was shown to be dependent upon the functional integrity of the RAD
50 gene.Treatment of growing yeast cultures with radioactively labelled ethyl methane sulphonate indicated the preferential uptake of radioactivity during the sensitive exponential stage of growth. The results indicated that the differential uptake of the chemical mutagens was responsible for at least a fraction of the variations in cell sensitivity observed in yeast cultures at different phases of growth. 相似文献
992.
993.
994.
RNA metabolism was studied in apices of Pharbitis nil duringand after floral induction. In continuous light 3H-uridine accumulatedin RNA at a constant rate over an 18 hr period. In darkness,however, the rate of accumulation of label into RNA was constantuntil the 10th hour at which time a rapid burst of accumulationoccurred, peaking at the 14th hour of darkness and followedby a net loss of label. The RNA involved in this burst is probablymRNA due to its size and poly(A) content. This phenomenon doesnot seem to be associated with floral induction, since the siteof perception is the apex, and it also occurs under conditionswhere floral initiation is inhibited by a brief light interruptionof the dark period. Immediately after floral induction by a16-hr dark period the rate of RNA synthesis was suppressed about14%. This suppression lasts for about 12 hr and was followedby a twofold increase in the rate of RNA synthesis, comparedto non-induced apices, at 64 hr after the beginning of the inductivedark period. These post-induction changes were found to occurin all RNA fractions.
1Present address: Department of Radiation Biology and Biophysics,University of Rochester School of Medicine and Dentistry, Rochester,N.Y. 14642, U.S.A. (Received March 15, 1976; ) 相似文献
995.
The protein content of apices and cotyledons in Morally inducedor vegetative plants of Pharbitis nilwas examined using isoelectricfocusing. No differences were found in the protein patternsproduced by apical tissue with and without floral induction.Cotyledons, however, repeatedly showed the distinct loss ofa single protein band on floral induction.
1Current address: Department of Radiation Biology and Biophysics,The University of Rochester School of Medicine and Dentristry,Rochester, N.Y. 14642, U.S.A. (Received March 29, 1976; ) 相似文献
996.
Summary Isoelectric focusing (IEF) of peroxidases of different organs and tissues of Nicotiana tabacum L. was performed on thin-layers of Sephadex and polyacrylamide. Isoelectric points (pI's) of peroxidase bands were measured by special electrodes. — The two types of layers showed very similar results. Reproductibility of pI's was better on polyacrylamide. This method is also easier to practise and requires less time than IEF on Sephadex (3 h versus 18). Thus for analytical purposes the acrylamide-technique is preferable, but if it is necessary to regain the separated enzymes it is better to perform IEF on Sephadex. — When IEF-patterns of peroxidase are compared with the disk electrophoresis (DE) patterns of the same tissue, important differences are observed. The 6 bands of GI (fast migrating, anodic group of DE) are reduced to 2 on the strongly acidic side of IEF (independent of the tissue studied). That means only 2 proteins in GI can be separated by pI's of the molecules. Maybe the heterogeneity of GI bands after DE indicates the presence of conformational isomers (conformers). — Because of the reduced number of bands in GI after IEF there is no difference in the patterns of many tissues (flowers, leaves, shoots, pith) as there is after disk electrophoresis. In the case of GII (slow migrating, anodic group of DE) on the other hand, there are always 4 different bands after isoelectric focusing in the lower acid region instead of 3 after disk electrophoresis. Disk electrophoresis of peroxidase-groups separated by isoelectric focusing shows the same patterns as direct disk electrophoresis of the extract. The methods produce no artifacts. —Comparison of these results with the peroxidase-patterns of tobacco found by other workers and by other techniques leads to the conclusion that there exist at least 4 isoenzymes of peroxidase corresponding to the 4 groups GI, GII, GIII, and GIV.
Abkürzungen IEF Isoelektrische Fokussierung - DE Disk-Elektrophorese - pI Isoelektrischer Punkt 相似文献
Abkürzungen IEF Isoelektrische Fokussierung - DE Disk-Elektrophorese - pI Isoelektrischer Punkt 相似文献
997.
George S. Hill Jr. Joseph Tabrisky Michael E. Peter 《The Western journal of medicine》1976,124(6):440-445
Tuberculous enteritis occurs in about 2 percent of patients with pulmonary tuberculosis. Although it is uncommon in the United States, tuberculous enteritis should be considered in any patient with active pulmonary tuberculosis and abdominal complaints.Eight cases of T. enteritis have been treated at Harbor General Hospital in the last 25 years. Associated pulmonary disease was shown radiologically to be present in seven of eight patients. Findings on contrast studies of the gastrointestinal tract showed disease in six of six patients examined.In five patients, surgical operation was required for diagnosis or complications. Resection of diseased bowel with primary anastomosis was done in five patients. Although medical therapy is the mainstay in the treatment of both pulmonary and intestinal tuberculosis, one staged resection of diseased bowel with primary anastomosis is the procedure of choice for complications such as obstruction, hemorrhage or perforation. 相似文献
998.
A radioimmunoassay for the human allotype Gm(b0) which provides a sensitive and quantitative measurement of the level of this IgG3 genetic marker has been developed. The assay system can detect 15 nanograms of Gm(b0) IgG3 protein and is not inhibited by immunoglobulins of other allotypes and isotypes. Using this assay, good correlation was found between IgG3 and Gm(b0) levels in homozygous Gm(f, b0) sera and gene dosage effects could be confirmed. The correlation between Gm(b0) levels and IgG3 in Negroid Gm(a, b0) sera was not as good. This reduced correlation has been attributed to antigen differences in the IgG3 Gm markers characteristic of some Negroid Gm(a, b0) sera. 相似文献
999.
The strength of the H-Y antigen on thymus cells and on skin was compared in differentH-2-congenic mouse strains using a host-versus-graft reaction popliteal lymph node assay, and skin grafts from males of parental strains grafted to F1 hybrid females. The results revealed considerable differences in the strength of the H-Y antigen among different congenic strains; these differences demonstrate the effect of theH-2-linked gene on the expression of the H-Y antigen. The linkage withH-2 was also confirmed in tests with segregating F2 generations. In the strains bearing recombinantH-2 haplotypes, the strength of the H-Y antigen is similar to that of parental strain from which the recombinant received itsK end, and the responsible gene (or genes) map to the left ofI-C. The effect of theH-2-linked gene(s) on thymus cells and skin is different. The gene linked to theK end ofH- 2b determines a strong H-Y antigen on thymus cells, but a relatively weak H-Y antigen on skin. The gene linked to theK end ofH- 2k determines a weak H-Y antigen on thymus cells, but a strong H-Y antigen on skin. The gene linked to theK end ofH- 2d determines a weak H-Y antigen on both thymus cells and skin. Our observations raise the possibility that the structural gene for the H-Y antigen is linked toH-2. Alternative (but not exclusive) explanations invoke regulatory effects ofH-2 on the expression of the H-Y antigen, possibly by means of the control of the cellular andogen receptors. 相似文献
1000.
Grafting an allogeneic neonatal thymus to a congenitally athymic adult nude mouse allows a sufficient generation of φ-positive lymphocytes to bring their relative and absolute numbers close to the values found in normal mice. However, the T-cell characteristic reactivities of thymus-grafted nudes persistently remain low, especially the responsiveness of lymphoid cell suspensions to T-cell mitogens. In a series of thymus-grafted nudes, significant numbers of thymus donor type lymphocytes were found to persist for long periods of time within the grafted thymus, but their persistence could not be directly correlated with the acceptance of skin of same strain origin as the thymus or with responsiveness to mitogens. 相似文献