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51.
Physiological and ultrastructural assessment of changes in the walls of venules in the rat cremaster muscle after administration of histamine indicates that pericytes have essential roles in the normal functioning of venules during inflammation. Fluorescein-labelled albumin was used to quantitate macromolecular leakage and to select suitable venules for ultrastructural analysis 4 and 7 minutes after addition of histamine. Pericytes were concentrated over endothelial cell junctions and gaps. At 4 minutes, when albumin leakage was becoming detectable, gaps between endothelial cells were observed in the venule wall. In 24 serially sectioned gaps, pericytes formed covers, with contact points to the endothelial cells along the sides of the gaps. At 7 minutes, when albumin leakage was maximal, gaps with pericyte covers were still evident, but more commonly observed were pericyte covers over closed endothelial cell junctions. Spaces between the innermost pericytes and endothelial cells were enlarged by an order of magnitude, from 95 nm in controls to 872 nm at 4 minutes and 958 nm at 7 minutes. Pericytes formed coverings or bridges over inclusions of extravasated cells, fluid, proteins, and the vascular label monastral blue. The data indicate that pericytes protect the endothelial lining of venules during histamine-induced inflammation by forming a cohesive covering across gaps. 相似文献
52.
Ted W. Simon Donald H. Edwards 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1990,166(6):745-755
The caudal photoreceptors (CPRs) of crayfish (Procambarus clarkii) can trigger walking and abdominal movements by their response to light.
相似文献
1. | In a restrained, inverted crayfish, illumination of A6 evoked a CPR discharge followed by leg movements and bursting from the abdominal tonic flexor (TF) motoneurons. Intracellular electrical stimulation of a single CPR at high frequency (80 Hz) evoked similar responses. |
2. | Responses only occurred when a single CPR axon was driven at 60 Hz or more and outlasted the stimulus. |
3. | CPR stimulation also excites the pattern-initiating network (Moore and Larimer 1987) in the abdomen. |
4. | The axon of the CPR projects from ganglion A6 to the brain. Terminal branches occur in the subesophageal ganglion and the brain. A small descending interneuron is dye-coupled to CPR in the subesophageal ganglion. |
5. | In animals with cut circumesophageal connectives, the CPRs can evoke walking and the abdominal motor pattern. |
6. | The relationship of the abdominal motor pattern to walking is altered by restraint and/or inversion. In freely moving crayfish, the cyclic abdominal motor pattern is only observed with backward walking. In restrained, inverted crayfish, the motor pattern occurs with both forward or backward walking. |
53.
Summary The actions of cyclic AMP are subject to several levels of post-receptor modulation in cardiac tissue. Isoproterenol and prostaglandin E1 both stimulate cAMP accumulation, but only isoproterenol causes activation of particulate cAMP-dependent protein kinase, leading to activation of phosphorylase kinase and glycogen phosphorylase, and inhibition of glycogen synthase. Through the use of isolated, adult ventricular myocytes, we have determined that the hormone-specific activation of glycogen phosphorylase is due to subcellular compartmentation of cAMP. There is some evidence that cyclic nucleotide phosphodiesterases, whose activity is stimulated by alpha1-adrenergic agonists in isolated myocytes, may have a role in compartmentation. Phosphoinositide hydrolysis is stimulated by alpha, and muscarinic agonists, presumably leading to activation of protein kinase C, which in turn has multiple effects on hormone-sensitive adenylate cyclase.Abbreviations cAMP
Adenosine-3,5-Cyclic Monophosphate
- cGMP
Guanosine-3,5-Cyclic Monophosphate
- Gi, GS
Guanine nucleotide-binding proteins linked to inhibition and stimulation, respectively, of adenylate cyclase
- GTP
Guanosine-5-triphosphate
- PDE
Cyclic Nucleotide Phosphodiesterase
- PGE1
Prostaglandin E1 相似文献
54.
The D region of the H-2
d
haplotype contains five class I genes: H-2D
d
, D2
d
, D3
d
, D4
d
and H-2L
d
. Although previous studies have suggested the presence of D-end encoded class I molecules in addition to H-2Dd and H-2Ld, segregation of genes encoding such molecules has not been demonstrated. In this report we have used cãtotoxic T lymphocytes (CTL) to examine the D region of the H-2
d
haplotype for the presence of additional class I molecules. CTL generated in (C3H × B6.K1)F1 (K
k
D
k
, K
b
D
b
) mice against the hybrid class I gene product Q10d/Ld expressed on L cells cross-react with H-2Ld but not H-2Dd molecules, as determined by lysis of transfected cells expressing H-2Ld but not H-2Dd. Although H-2Ld-specific monoclonal antibodies (mAb) completely inhibit H-2Ld-specific CTL from killing B10.A(3R) (K
b
D
d
L
d
) target cells, only partial inhibition of anti-Q10 CTL-mediated lysis was observed, suggesting the presence of an additional D-end molecule as a target for these latter CTL. To identify the region containing the gene encoding the Q10 cross-reactive molecule, we show that anti-Q10 CTL lyse target cells from a D-region recombinant strain B10.RQDB, which has H-2D
d
, D2
d
, D3
d
, D4
d
, and H-2D
b
but not the H-2L
d
H-2
d
, and H-2L
d
(including D2
d
, D3
d
, and D4
d
, lacks this anti-Q10 CTL target molecule. Together, these data demonstrate that a class I gene mapping between H-2D
d
and H-2L
d
encodes an antigen recognozed by anti-Q10 CTL. A likely candidate for this gene is D2
d
, D3
d
or D4
d
. 相似文献
55.
56.
57.
58.
Kelly K. Hunt Masahiko Shibata Rishab K. Gupta Donald L. Morton 《Cancer immunology, immunotherapy : CII》1992,34(6):377-382
Summary We developed a high-titer polyclonal antiserum to a glycoprotein tumor-associated antigen (TAA) by immunization of a baboon with the purified glycoprotein antigen. The baboon serum was fractionated into IgG and IgM components by DEAE Affi-Gel blue chromatography. The ability of the baboon IgM anti-TAA antibody to effect tumor cell lysis in the presence of complement was tested using a chromium-release assay. The baboon antibody was able to lyse melanoma target cells (20.8%–71.4% cytolysis), breast carcinoma cells (36.5%–38.9% cytolysis), and a neuroblastoma cell line (35.5% cytolysis) in the presence of complement but did not effect significant lysis of autologous lymphoblastoid cell lines (4.9% cytolysis) or peripheral blood lymphocytes from healthy volunteers (12.6% cytolysis). Cytolysis of melanoma target cells was completely inhibited by preabsorption of the IgM anti-TAA antibody with UCLA-SO-M14 (M14) cells and partially inhibited by preabsorption with several other melanoma cell lines. There was no significant inhibition of tumor cell lysis after preabsorption of the antibody with lymphoblastoid cell lines. Complement-dependent lysis of M14 targets could be blocked by addition of the purified antigen to the antibody prior to incubation with the tumor cells. Our results suggest that the glycoprotein TAA resides on the tumor cell surface and that the baboon IgM anti-TAA antibody recognizes the antigen on the cell surface and is able to fix complement and effect the lysis of the tumor cells. 相似文献
59.
Sarah Jane Gurr Michael J. McPherson Claire Scollan Howard J. Atkinson Dianna J. Bowles 《Molecular & general genetics : MGG》1991,226(3):361-366
Summary A major pathogen of potato plants (Solanum tuberosum) is the potato cyst nematode (Globodera spp.), which induces localized redifferentiation of a limited number of host cells to form a specialized feeding-site termed the syncytium. A novel strategy utilizing the polymerase chain reaction (PCR) was employed to construct a cDNA library from dissected potato roots highly enriched in syncytial material. The library was differentially screened with cDNA probes derived from the infected root tissue from a compatible interaction and from healthy root tissue. Characterization of one gene identified by the library screen indicated an expression pattern that correlated with events in the immediate vicinity of the pathogen after syncytial establishment. The strategy for library construction and screening could be applicable to the study of gene expression in any plant-pathogen interaction in which the limited supply of cells at the interface of the two organisms precludes a more traditional approach. 相似文献
60.
Alternatively spliced RNAs encode several isoforms of CD46 (MCP), a regulator of complement activation 总被引:2,自引:0,他引:2
Damian F. J. Purcell Sarah M. Russell Nicholas J. Deacon Melissa A. Brown David J. Hooker Ian F. C. McKenzie 《Immunogenetics》1991,33(5-6):335-344
Five alternative cDNA clones were isolated for CD46, also known as the membrane cofactor protein (MCP) for the factor I-mediated cleavage of the complement convertases. One of these cDNA clones (a) was identical to an earlier MCP clone. The other four CD46 clones 3ontained the four NH2-terminanl short consensus repeat (SCR) units of MCP, but differed at the region encoding the carboxyl-terminal of the protein which includes an extracellular segment rich in Ser, Thr, and Pro residues, a hydrophobic membrane-spanning domain, and a 33 amino acid cytoplasmic tail. The different CD46 cDNAs have variously: (b) inserted a 93 base pair (bp) exon resulting in a new cytoplasmic tail of 26 amino acids; (c) deleted a 42 bp exon from the extracellular Ser/Thr rich region; (d) used a cryptic splice acceptor sequence to delete 37 bp from an exon encoding transmembrane sequence; or (e) failed to splice the intron after the four SCR units. These were shown by northern blot and polymerase chain reaction to arise by alternative splicing of CD46 RNA. Forms (a), (b), and (c) of CD46 RNA are common in placental RNA, but (d) was rare, and (e) was incompletely processed and therefore aberrant. The polymerase chain reaction (PCR) was used to map the sites of the intron/exon junctions and demonstrate further possible splice variants of CD46. The alternative RNAs for CD46 may correlate to the different isoforms of CD46 found in different tissues, tumors, and in serum.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number M58050.
Address correspondence and offprint requests to: D. F. J. Purcell. 相似文献