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101.
J C Lecron L Sutton M D Mossalayi J Tanzer P Goube de Laforest 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1987,305(18):639-642
Evidence is presented that B+ null lymphocyte supernatants, previously shown to promote the growth of CD4+ T lymphocyte colonies from human marrow precursors, can also selectively enhance CD4+ T cell proliferative response to PHA and IL2. 相似文献
102.
Complete sequences of the rRNA genes of Drosophila melanogaster 总被引:19,自引:0,他引:19
In this, the first of three papers, we present the sequence of the
ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of
D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S
(123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat
of D. melanogaster is AT rich (65.9% overall), with the spacers being
particularly AT rich. Analysis of DNA simplicity reveals that, in contrast
to the intergenic spacer (IGS) and the external transcribed spacer (ETS),
most of the rRNA gene regions have been refractory to the action of
slippage-like events, with the exception of the 28S rRNA gene expansion
segments. It would seem that the 28S rRNA can accommodate the products of
slippage-like events without loss of activity. In the following two papers
we analyze the effects of sequence divergence on the evolution of (1) the
28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary
structures among eukaryotic species, respectively. Our detailed analyses
reveal, in addition to unequal crossing-over, (1) the involvement of
slippage and biased mutation in the evolution of the rDNA multigene family
and (2) the molecular coevolution of both expansion segments and the
nucleotides involved with compensatory changes required to maintain
secondary structures of RNA.
相似文献
103.
A genomic DNA fragment (gCORE-1), encoding a portion of the cartilage proteoglycan core protein, has been isolated from a phage library using cDNA as a probe. The genomic insert is about 17 kilobase pairs; two BamHI fragments of the insert (1.3 and 4.8 kilobase pairs) contain most of the hybridizable sequences found in the cDNA. Sequence analysis of these fragments shows that they contain a total of five exons that encompass 216 amino acid residues, all of which are identical to those of the corresponding cDNA sequence. Three of the exons, which are adjacent to one another, are very similar to the corresponding exons in the gene of a rat hepatic lectin as well as to an exon in the gene of human pulmonary surfactant-associated protein. There is a strong degree of conservation of amino acid sequences encoded in the three genes, although there is no similarity between their introns. The sizes of the five exons in gCORE-1, except for one (which is indeterminate because only a partial cDNA sequence is available), are less than 184 base pairs, whereas the sizes of the introns range from 218 to greater than 2629 base pairs. Four of the introns interrupt an exon codon at either their donor or acceptor sites, between the first and second nucleotides. Only one intron does not split a codon. Intron and exon boundary sites are in agreement with known consensus sequences for introns. The dispersed distribution and relatively small size of the exons, if representative of the entire gene, suggest that the complete gene which codes for the core protein may be quite sizable. 相似文献
104.
105.
106.
Physiological functions of mineral macronutrients 总被引:6,自引:0,他引:6
Frans JM Maathuis 《Current opinion in plant biology》2009,12(3):250-258
107.
Carolyn J. M. Best Lee R. Tanzer Patricia C. Phelps Ronald L. Merriman George G. Boder Benjamin F. Trump Kathryn A. Elliget 《In vitro cellular & developmental biology. Animal》1999,35(4):205-214
Summary We studied the effect of the ras oncogene on the growth kinetics, morphology, cytoskeletal structure, and tumorigenicity of the widely used NRK-52E rat kidney
epithelial cell line and two H-ras oncogene-transformed cell lines, H/1.2-NRK-52E (H/1.2) and H/6.1-NRK-52E (H/6.1). Population doubling times of NRK-52E, H/1.2,
and H/6.1 cells were 28, 26, and 24 h, respectively, with the transformed cells reaching higher saturation densities than
the parent cells. NRK-52E cells had typical epithelial morphology with growth in colonies. H/1.2 and H/6.1 cell colonies were
more closely packed, highly condensed, and had increased plasma membrane ruffling compared to parent cell colonies. NRK-52E
cells showed microfilament, microtubule, and intermediate filament networks typical of epithelial cells, while H/1.2 and H/6.1
cells showed altered cytoskeleton architecture, with decreased stress fibers and increased microtubule and intermediate filament
staining at the microtubule organizing center. H/1.2 and H/6.1 cells proliferated in an in vitro soft agar transformation
assay, indicating anchorage-independence, and rapidly formed tumors in vivo with characteristics of renal cell carcinoma,
including mixed populations of sarcomatoid, granular, and clear cells, H/6.1 cells consistently showed more extensive alterations
of growth kinetics, morphology, and cytoskeleton than H/1.2 cells, and formed tumors of a more aggressive phenotype. These
data suggest that analysis of renal cell characteristics in vitro may have potential in predicting tumor behavior in vivo,
and significantly contribute to the utility of these cell lines as in vitro models for examining renal epithelial cell biology
and the role of the ras proto-oncogene in signal transduction involving the cytoskeleton. 相似文献
108.
Andrew RJ Mitchell Philip Roberts Jonas Eichhöfer Jonathan Timperley Oliver JM Ormerod 《Cardiovascular ultrasound》2004,2(1):1-4
Percutaneous coronary intervention can be associated with distal embolization of thrombotic material causing myocardial necrosis and infarction. We discuss the role of intravascular imaging to guide the use of a distal protection device by describing the outcome of a young woman presenting with non-ST elevation myocardial infarction. Coronary angiography demonstrated an isolated minor stenosis in the proximal left anterior descending coronary artery with slight haziness beyond the lesion. Intravascular ultrasound confirmed an extensive thrombus overlying a bulky atherosclerotic plaque. A distal filter wire was therefore successfully used to reduce the risk of distal embolization. The use of intravascular ultrasound in patients presenting with acute coronary syndrome may reveal large thrombi that are difficult to image using conventional angiographic techniques. Intravascular ultrasound can therefore be used as a tool to select lesions requiring distal protection. 相似文献
109.
Collagens and elastin: structure and interactions 总被引:1,自引:0,他引:1
M L Tanzer 《Current opinion in cell biology》1989,1(5):968-973
110.