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111.
The object of this study was to determine the kinetics of chromosome decondensation during the G1 period of the HeLa cell cycle. HeLa cells synchronized in the G1 period following the reversal of mitotic block were fused with Colcemid-arrested mitotic HeLa cells at 1.5, 3, 5, and 7 h
after the reversal of N2O block. The resulting prematurely condensed chromosomes (PCC) were classified into six categories depending on the degree
of their condensation. The frequency of occurrence of each category was plotted as a function of time after mitosis. The results
of this study indicate that the process of chromosome decondensation, initiated during the telophase of mitosis continues
throughout the G1 period without any interruption, thus the chromatin reaches an ultimate state of decondensation by the end of G1 period, when DNA synthesis is initiated. 相似文献
112.
J. J. Schneller 《Plant Systematics and Evolution》1979,132(4):255-277
In EuropeAthyrium filix-femina has a constant chromosome number (2n = 80) and is sexual. The normal type of reproduction is intergametophytic crossing. In the gametophyte phase there is a hormone system which induces dark germination of spores and antheridium formation. Sporophytes originating from single prothalli show that a genetic load is present in all population examined. It appears not to be a simple allelic load but a complicated balanced system. Morphological variability can be interpreted as the expression of the genetic heterogeneity of populations. There are no crossing barriers, not even between insular populations hundreds of kilometers apart. 相似文献
113.
An electrophoretic variant of the X-linked enzyme phosphoglycerate kinase (PGK-1) has been used to study regulation of X chromosome expression in the diploid derivatives of the trophectoderm at 8–8.5 days post coitum in the mouse. These derivatives included the chorionic ectoderm and the polar trophoblast. The biochemical analysis suggests that only the maternally derived X chromosome (Xm) is expressed in the diploid trophectoderm derivatives. Cell selection and maternal tissue contamination were ruled out as possible causes of the observed Xm expression. From these and other results, we conclude that all derivatives of the trophectoderm, along with the primitive endoderm, express only Xm, whereas derivatives of the primitive ectoderm show random X chromosome expression. 相似文献
114.
Assignment of the gene for dipeptidase 2 to Mus musculus chromosome 18 by somatic cell hybridization
Evidence is presented for the assignment of the gene for dipeptidase 2 to Mus musculus chromosome 18 by synteny testing and karyotypic analysis of Chinese hamster × mouse somatic cell hybrid clones. DIP-2 and chromosome 18 were expressed concordantly in 24/24 clones examined (ten primary clones and 14 secondary clones). Synteny testing indicated that DIP-2 was not expressed concordantly with the expression of any marker enzymes.This work was supported by NIH grant USPHS GM 09966. 相似文献
115.
Evidence is presented for the assignment of the gene for glyoxylase I to mouse chromosome 17 using mouse × Chinese hamster somatic cell hybrids. GLO I was not expressed concordantly with any known marker enzymes which represented 11 linkage groups. The presence of chromosome 17 and expression of GLO I were concordant in 31/31 clones. GLO I is thus linked to the H-2 histocompatibility locus in the mouse. 相似文献
116.
A mutant form of erythrocyte hypoxanthine-guanine phosphoribosyltransferase with an abnormal isoenzyme pattern was found in a patient with a partial enzyme deficiency and X-linked gout. This abnormal pattern was a marker for the mutant enzyme in hemolysate from the heterozygote for the enzyme deficiency.These studies were generously supported by the Medical Research Council of Canada (MRC # MA4758) and the Canadian Arthritis and Rheumatism Society. 相似文献
117.
Rick G. Kelsey Jerry W. Thomas Thomas J. Watson Fred Shafizadeh 《Biochemical Systematics and Ecology》1975,3(4):209-213
The sesquiterpene lactones and chromosome numbers for three chemical races of Artemisia tridentata ssp. vaseyana have been examined from four populations in western Montana. TLC analysis of the sesquiterpene lactones in the seeds and seed producing parents demonstrated that genetic exchange does occur between sympatric sesquiterpene lactone chemical races. However, other evidence suggests that introgression between these races is restricted to zones of sympatry. There appears to be no correlation between chromosome numbers and sesquiterpene lactone races. 相似文献
118.
A hypothesis has been proposed that the regions of DNA loop anchorage to the nuclear matrix are the preferential sites (hot spots) of illegitimate recombination mediated or triggered by topoisomerase II of the nuclear matrix. Recombination between the regions of DNA loop anchorage to the nuclear matrix may result in deletion or repositioning of DNA loops or their groups. The proposed hypothesis is confirmed by the results of original experiments and published data obtained by other researchers.__________Translated from Molekulyarnaya Biologiya, Vol. 39, No. 4, 2005, pp. 633–638.Original Russian Text Copyright © 2005 by Razin, Iarovaia. 相似文献
119.
Brian Rosen Editor‐in‐Chief 《分类学与生物多样性》2013,11(1):1-2
The Y human chromosome has many ancient genes whose fidelity seems to have been preserved by tandem sequences and palindromic ‘hairpins’, compared/repaired by ‘gene conversion’. That a primary function of recombination machinery is DNA repair has been suggested, and rejected, several times; this new evidence is very persuasive. The process, better called gene conservation than gene conversion, could operate in all diploid organisms, accounting for the retention of long gene sequences without ‘informational meltdown’ ('concerted evolution'). It resembles rocket‐science computer‐redundancy error‐checking, comparison of three or four sequences, not just two. If recognition of errors in ‘converted’ sequences can be followed by either repair or rejection, the rejection option can account for the vast wastage of meiotic products. The repair option might be used in Drosophila oocytes and even zygotic nuclei, possibly other oocytes, ancient asexual lineages such as mycorrhizal fungi, perhaps the Y itself. Both evolutionary stasis (conservatism) and development and deployment of complex developmental modules can be understood in these terms so both the evolution of biodiversity and the practice of systematics may have these mechanisms as their bases. The main individual‐fitness and evolutionary advantages of diploidy were not primarily cloaking of recessive al‐leles, or allelic recombination and Mendelism, but conserving long DNA sequences. 相似文献
120.
Sang-Im Yun Byung-Hak Song Jin-Kyoung Kim Young-Min Lee 《Journal of visualized experiments : JoVE》2015,(106)
Reverse genetics, an approach to rescue infectious virus entirely from a cloned cDNA, has revolutionized the field of positive-strand RNA viruses, whose genomes have the same polarity as cellular mRNA. The cDNA-based reverse genetics system is a seminal method that enables direct manipulation of the viral genomic RNA, thereby generating recombinant viruses for molecular and genetic studies of both viral RNA elements and gene products in viral replication and pathogenesis. It also provides a valuable platform that allows the development of genetically defined vaccines and viral vectors for the delivery of foreign genes. For many positive-strand RNA viruses such as Japanese encephalitis virus (JEV), however, the cloned cDNAs are unstable, posing a major obstacle to the construction and propagation of the functional cDNA. Here, the present report describes the strategic considerations in creating and amplifying a genetically stable full-length infectious JEV cDNA as a bacterial artificial chromosome (BAC) using the following general experimental procedures: viral RNA isolation, cDNA synthesis, cDNA subcloning and modification, assembly of a full-length cDNA, cDNA linearization, in vitro RNA synthesis, and virus recovery. This protocol provides a general methodology applicable to cloning full-length cDNA for a range of positive-strand RNA viruses, particularly those with a genome of >10 kb in length, into a BAC vector, from which infectious RNAs can be transcribed in vitro with a bacteriophage RNA polymerase. 相似文献