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911.
Plasmid DNA carrying either the nitrate reductase (NR) gene or the argininosuccinate lyase gene as selectable markers and the correspondingChlamydomonas reinhardtii mutants as recipient strains have been used to isolate regulatory mutants for nitrate assimilation by insertional mutagenesis. Identification of putative regulatory mutants was based on their chlorate sensitivity in the presence of ammonium. Among 8975 transformants, two mutants, N1 and T1, were obtained. Genetic characterization of these mutants indicated that they carry recessive mutations at two different loci, namedNrg1 andNrg2. The mutation in N1 was shown to be linked to the plasmid insertion. Two copies of the nitrate reductase plasmid, one of them truncated, were inserted in the N1 genome in inverse orientation. In addition to the chlorate sensitivity phenotype in the presence of ammonium, these mutants expressed NR, nitrite reductase and nitrate transport activities in ammonium-nitrate media. Kinetic constants for ammonium (14C-methylammonium) transport, as well as enzymatic activities related to the ammonium-regulated metabolic pathway for xanthine utilization, were not affected in these strains. The data strongly suggest thatNrg1 andNrg2 are regulatory genes which specifically mediate the negative control exerted by ammonium on the nitrate assimilation pathway inC. reinhardtii. 相似文献
912.
Claudia Gaspar Iscia Lopes-Cendes Anita L. DeStefano Patrícia Maciel Isabel Silveira Paula Coutinho Patrick MacLeod Jorge Sequeiros Lindsay A. Farrer G. A. Rouleau 《Human genetics》1996,98(5):620-624
Machado-Joseph disease (MJD) is an autosomal dominant spinocerebellar degeneration originally described in families of Portuguese-Azorean
ancestry. The hypothesis that its present world distribution could result from the spread of an original founder mutation
has been raised. To test this possibility we have conducted a linkage disequilibrium study of markers segregating with the
MJD1 locus in a total of 64 unrelated families of different geographical origins. Significant association was detected between
the MJD1 locus and marker alleles at loci D14S280, D14S1050 and D14S81. All affected individuals, except one Chinese family, had allele
3 (237 bp) at D14S280. This finding is consistent with a founder effect in our MJD population. However, distinct haplotypes
were observed in patients originating from the two Azorean islands showing the highest disease prevalence; therefore, the
possible existence of more than one founder mutation can not be excluded with the markers currently available.
Received: 27 February 1996 / Revised: 4 June 1996 相似文献
913.
Lymphocyte subpopulations of regional lymph nodes in human colon and gastric adenocarcinomas 总被引:3,自引:0,他引:3
Beatriz Lores-Vazquez Margarita Pacheco-Carracedo Josefina Oliver-Morales Purificación Parada-Gonzalez F. Gambón-Deza 《Cancer immunology, immunotherapy : CII》1996,42(6):339-342
In order to study the host immune response to tumours, previous knowledge of the cellular composition of regional draining
lymph nodes is necessary. Enlarged regional lymph nodes are a common finding in colon and gastric adenocarcinomas. We have
studied the cellular composition of normal non-reactive and of regional draining lymph nodes of colon and gastric adenocarcinomas.
In normal non-reactive lymph nodes, T lymphocytes (CD2+, CD7+) constituted the largest fraction of the lymphoreticular cells. These lymphocytes were mainly CD4+, and there were more cells expressing the CD45RA isoform of the CD45 antigen than CD45RO. Reactive lymph nodes presented
a decreased proportion of CD4+ CD45RA+ cells and an increased number of B cells. Although most of the T cells in the reactive nodes were CD4+ CD45RO+, their proportion was similar to that found in normal non-reactive nodes. We studied the presence of the molecules CD28 and
CD80 involved in the processes of interaction and activation of T and B lymphocytes. The CD28 molecule was found in all the
T lymphocytes, while the CD80 molecule was weakly expressed on the B lymphocyte membrane.
Received: 4 January 1996 / Accepted: 28 May 1996 相似文献
914.
Geographic differences in the allele frequencies of the human Y-linked tetranucleotide polymorphism DYS19 总被引:13,自引:0,他引:13
Fabrício R. Santos Tudevdagva Gerelsaikhan Bjamba Munkhtuja Tsendsuren Oyunsuren Jörg T. Epplen Sérgio D. J. Pena 《Human genetics》1996,97(3):309-313
We have studied the allele frequency distribution of the microsatellite locus DYS 19 in several populations with different geographical origins worldwide. Three new alleles were found. In addition, remarkable geographic and ethnic differences were observed in the allele frequency profiles and DNA marker (gene) diversity among populations and major ethnic groups. Amerindians showed an overwhelming predominance of the A allele, while in Caucasians the B allele was modal, and in Greater Asians and Africans allele C became predominant. Even within these geographic regions there were significant gradients, as exemplified by the decreasing frequency profile of the B allele from Great Britain over Germany to Slovakia. Thus, DYS 19 emerges as a useful tool for studying the structure and dynamics of human populations. 相似文献
915.
María E. Jiménez-Capdeville Tomás A. Reader Eduardo Molina-Holgado Robert W. Dykes 《Neurochemical research》1996,21(1):1-6
This study examined the effects of a nerve transection on monoamine release from primary somatosensory cortex. The technique
of microdialysis was employed to sample extracellular levels of norepinephrine (NE), 3,4-dihydroxyphenylacetic acid (DOPAC),
5-hydroxyindole-3-acetic acid (5-HIAA) and homovanillic acid (HVA) in the barrel field of freely moving rats following the
surgical transection of the contralateral infraorbital nerve. Microdialysates obtained 3, 4, and 5 days after deafferentation
were analyzed using high-performance liquid chromatography with electrochemical detection. We found a significant increase
in the release of the dopamine metabolites, DOPAC and HVA from the deafferented cortex. Three days after deafferentation the
release of DOPAC was three-fold higher in the deafferented than in the control animals, and remained about 100% higher in
the next two days in this group of animals. The release of HVA showed a gradual increase following the deafferentation procedure,
since a 92% larger value on day 3 increased to a 338% difference on day 5. On the other hand, the release rate of NE and the
levels of the serotonin metabolite 5-HIAA were not significantly affected by the deafferentation procedure. These results
are discussed in the context of the possible participation of dopamine in the reorganization of the deafferented somatosensory
cortex. 相似文献
916.
Carlos Hermenegildo Goizane Marcaida Carmina Montoliu Santiago Grisolía María-Dolores Miñana Vicente Felipo 《Neurochemical research》1996,21(10):1237-1244
We proposed that acute ammonia toxicity is mediated by activation of NMDA receptors. To confirm this hypothesis we have tested
whether different NMDA receptor antagonists, acting on different sites of NMDA receptors, prevent death of mice induced by
injection of 14 mmol/Kg of ammonium acetate, a dose that induces death of 95% of mice. MK-801, phencyclidine and ketamine,
which block the ion channel of NMDA receptors, prevent death of at least 75% of mice. CPP, AP-5, CGS 19755, and CGP 40116,
competitive antagonists acting on the binding site for NMDA, also prevent death of at least 75% of mice. Butanol, ethanol
and methanol which block NMDA receptors, also prevent death of mice. There is an excellent correlation between the EC50 for preventing ammonia-induced death and the IC50 for inhibiting NMDA-induced currents. Acute ammonia toxicity is not prevented by antagonists of kainate/AMPA receptors, of
muscarinic or nicotinic acetylcholine receptors or of GABA receptors. Inhibitors of nitric oxide synthase afford partial protection
against ammonia toxicity while inhibitors of calcineurin, of glutamine synthetase or antioxidants did not prevent ammonia-induced
death of mice. These results strongly support the idea that acute ammonia toxicity is mediated by activation of NMDA receptors. 相似文献
917.
Ma Rosario de la Torre Angela Casado Ma Encarnación López-Fernández Diana Carrascosa Ma Concepción Casado Domenico Venarucci Vincenzo Venarucci 《Neurochemical research》1996,21(8):885-888
In order to investigate the role of two free radical detoxificant enzymes in patients with aging brain disorders, superoxide
dismutase (SOD) and catalase (CAT) activities have been measured in blood from male and female human patients of different
ages with several types of aging brain disorders. When compared with activities in the normal population, we have detected:
1) SOD and CAT activities are decreased in patients with Parkinson disease. 2) SOD activity seems to be normal and CAT activity
is decreased in patients with dementia. 3) In the patients with stroke, SOD activity is normal, while CAT activity is decreased.
SOD activity was measured in red blood cells using the Minami and Yoshikawa method. CAT activity was measured in hemolysates
by the method of Aebi. We can conclude that SOD and CAT activities in patients with Parkinson disease are decreased. 相似文献
918.
J. F. Romero Collazos M. D. Marrodán E. Gutierrez Redomero 《International Journal of Anthropology》1996,11(1):11-19
Anthropometric characteristics of proportionality, body composition and somatotype have been determined in a group of 72 Spanish
judoists. The sample includes the junior male and female National Team, and seniors competitors in the last Olimpic Games
held in 1992, and participants in the National Championship of 1993. The methodology has been used according to Weiner and
Lourie(1981)and MOGAP procedures described by Borms et al. (1979). The obtained results show a similar proportionality profile
and mesoendomorphic mean somatotype in both male and female series. However, were found significant differences between sexes
as well as depending of weight categories. 相似文献
919.
Mikael Hedrén 《Plant Systematics and Evolution》1996,201(1-4):31-55
Taxa endemic to North-western Europe are rare, but the orchid genusDactylorhiza contains several species restricted to this area. Evidence from morphological and cytological studies have indicated that some species may have arisen recently and may be of hybrid origin. In the present report, I use allozymes to characterize the genomes in various species ofDactylorhiza and evaluate the possibilities for rapid evolutionary change in the genus. Allotetraploid species have evolved repeatedly from two principal diploid ancestral lineages. These lineages include extant diploid and autotetraploid species, from which allotetraploid derivatives may still arise. It is suggested that allotetraploidization dominates over introgression as speciation mechanism in the genus. The more common and widespread allotetraploid species could be characterized by their allozyme characters over considerable distances, indicating that each of them may have a unique origin and that they have spread from their ancestral populations to the present distribution areas. However, it is also possible that some allotetraploid species contain local populations that have been independently derived from the ancestral lineages. 相似文献
920.
Abstract The global regulators agr and sar control expression of cell wall and extracellular proteins. Inactivation of either sar and/or agr in a typical heterogeneously methicillin-resistant Staphylococcus aureus resulted in a small but reproducible decrease in the number of cells in the subpopulation expressing high methicillin resistance. The amount of low affinity penicillin-binding protein PBP2', the prerequisite for methicillin resistance, was apparently not affected, however, a reduction in PBP1 and PBP3 production was observed, suggesting that these resident PBPs of the cells might be involved somehow together with PBP2' in high level methicillin resistance. 相似文献