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991.
Acetylcholinesterase from Drosophila melanogaster. Identification of two subunits encoded by the same gene 总被引:3,自引:0,他引:3
Purified acetylcholinesterase from Drosophila melanogaster is composed of a 55 kDa and a 16 kDa noncovalently associated subunit. Cleavage of disulfide bonds reveals that two 55 kDa polypeptides are linked together in native dimeric AChE. Western blots with two antibodies directed against the N- and C-termini of the predicted AChE primary sequence show that the 55 and 16 kDa polypeptides originate from proteolysis of the same precursor encoded by the Ace locus. 相似文献
992.
Chinese hamster cells (Don line) were treated in vivo with 5-BrdU and 33258-Hoechst fluorochrome for obtaining the partial inhibition of condensation that causes the R-banding pattern. Untreated chromosomes were stained by a standard G-banding method. Statistical measurements show significant differences in the band numbers between the two treatments. The Don cell line in the authors' laboratory presents some karyotypical differences from Don cell lines studied by other authors. 相似文献
993.
A quantitative method for investigation of relationship between polygenic and monogenic traits has been proposed. It is based on examination of relationship between frequencies of distribution classes of an adaptive quantitative trait and frequencies of certain genetic character in the same classes. The method permits to locate a gene marker within a space of quantitative trait values. Using adaptively significant morpho-anatomic traits, it is possible to estimate indirectly adaptive values of gene markers under consideration, since, in accordance with the concept of adaptive norm, "average" phenotypes have maximal fitness, whereas deviative phenotypes transgress the bounds of the optimum. As a genetical character, genotype of certain biochemical locus, individual heterozygosity range or interlocus combinations of alleles could be used. The method has been applied to newborn Astrakhan lambs. Principal component analysis has been used to obtain complex characterization for six constitutional characters. Some regularities in location of homo- and heterozygous genotypes of the transferrin locus within a space of morphological characters' values have been revealed. 相似文献
994.
The influence of animals on phosphorus cycling in lake ecosystems 总被引:14,自引:6,他引:8
Aquatic animals directly influence the cycling of phosphorus in lakes through feeding and excretion. Traditionally, animals (zooplankton, benthic invertebrates and fish) have been assigned only minor roles in the process of freshwater phosphorus cycling. They were regarded as consumers without much regulating influence. Today there is growing evidence that animals, predators and herbivores, directly or indirectly can control biomass of primary producers and internal cycling of phosphorus.This paper summarizes different mechanisms of transformation and translocation of phosphorus via different groups of organisms. 相似文献
995.
Phosphorus in sediments — speciation and analysis 总被引:3,自引:0,他引:3
Characterization of sediment phosphorus is commonly based on sequential chemical extractions, in which phosphorus is supposed to be selectively removed from different compounds in the sediments. The first extraction schemes were designed to quantify discrete chemical or mineralogical compounds. As extraction schemes have been tested on different sediments, several systematic errors have been detected and the schemes have been modified and simplified accordingly. Other chemical extractions or treatments have attempted to determine phosphorus bound to particles with a certain strength or binding energy, the purpose being to determine the labile, loosely bound, exchangeable, mobile or algal-available fraction of sediment phosphorus. All extraction procedures yield operationally defined fractions and cannot be used for identification of discrete phosphorus compounds. The many methodological modifications make it necessary to be cautious when comparing results from the literature in this field. 相似文献
996.
Gerhard Ruhenstroth-Bauer Olga Rösing Hans Baumer Walter Sönning Walter Lehmacher 《International journal of biometeorology》1988,32(3):201-204
Between the mean daily density of 28 kHz atmospherics and the onset of epileptic fits there is a highly significant correlation coefficient (r) of 0.30; there is a negative coefficient of –0.20 between the fits and the mean daily density of 10 kHz atmospherics. The onset of heart infarction is correlated with 28 kHz atmospherics (r=0.15). Furthermore, we have discovered that sudden deafness is also correlated with certain configurations of atmospherics. In this paper we report the following correlation coefficients between the inflammatory reaction of rats to a carrageenan injection (rci) into a hind paw and the mean daily pulse rate of atmospherics of the same day:r=0.49 for the 8 kHz atmospherics (P<0.02) andr=0.44 for the 10 kHz atmospherics (P<0.04). The correlations between rci reaction and other atmospherics (12 and 28 kHz) are smaller and not significant. By the method of multiple linear regression we found a multipleR=0.54 between rci reaction and the 8 and 10 kHz atmospherics (the regression function for the rci reaction is 0.15+0.004×8 kHz+0.002×10 kHz,P<0.05). 相似文献
997.
Frequencies of chromosomal aberrations induced in human blood lymphocytes by low doses of X-rays 总被引:2,自引:0,他引:2
D C Lloyd A A Edwards A Léonard G Deknudt A Natarajan G Obe F Palitti C Tanzarella E J Tawn 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1988,53(1):49-55
The dose-response for radiation-induced chromosome aberrations in human lymphocytes is usually fitted to the quadratic model. This assumes that the slope is essentially linear at low doses. Empirical observations of linearity at less than 200 mGy are, however, sparse. Some data have been published indicating a non-linear (threshold) response and these are reviewed. In particular one study with X-rays showed a plateau in response up to 50 mGy and with a significant dip below the control level at 4 mGy. The mechanism proposed to explain non-linearity is that low doses stimulate the enzymic repair capability of lymphocytes. Preliminary data are presented from a large experiment by six laboratories in which the low dose-response for X-rays has been re-examined. The plateau in the dose-response relationship, if it exists, does not extend to doses above approximately 10 mGy. No irradiated cells yielded aberration levels significantly below the control. Over the range 0-300 mGy the response can be fitted to a linear regression. There are, however, variations in sensitivity between cells from different donors. An unexpected finding was that some lymphocytes contained greater than 1 exchange aberrations. This may indicate a small subset of cells that are especially susceptible to the induction of aberrations by low doses. 相似文献
998.
A lot of traps and difficulties complicate the estimation of a genetic risk in the autosomal dominant diseases. The authors recapitulate the notions of mutation, penetrance and variability and illustrate by some examples the part of each of them, isolated or associated together. The increasing of molecular biology allows to resolve some of these problems, but generate new dangers which are analysed and illustrated. 相似文献
999.
Aside from the digestive enzymes the submandibular salivary glands (SSG) synthetize other polypeptides, detected also in saliva, with varied biological activity; NGF and EGF are the knowest. However, over the last decade, steroids hormones have been also found out in the saliva at the same concentrations that the free plasma fraction. The origin of these hormones is largely discussed and certain authors have even proposed a local synthesis for them. This matter, is of clinical interest because gingiva and buccal tissues are knowingly sensitive to steroids. Besides, woman ovulation appears to be monitored through progesterone fluctuations in saliva. Another kind of salivary substances is formed by the neuropeptides of the gut-brain axis, mainly VIP and SRIF. The former likely of nervous origin seems to be involved in the atropine-resistant salivary secretion, whereas the latter-likely of SSG origin--appears as a factor associated with glycemia control. 相似文献
1000.
J Lejeune M Peeters M C de Blois M Bergère A Grillot M O Rethoré G Vallée M Izembart J P Devaux 《Annales de génétique》1988,31(3):137-143
An excess of thyrotropin (TSH) with normal levels of tetraiodothyronine (T4) and of 3,5,3'-triiodothyronine (T3) was confirmed in the serum of 78 trisomy 21 children. A severe deficiency of 3,3',5'-triiodo-thyronine (rT3 or reverse T3) was observed and the decrease of the rT3/TSH ratio was highly significant. These new facts suggest that the rT3 deficiency plays a peculiar role in trisomy 21 (maybe through the regulation of one or few steps of monocarbons' metabolism). A systematic control of thyroid function (including the patient's rT3 level) is mandatory for the follow-up of every trisomy 21 patient. 相似文献