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991.
Bapat A Nguyen TP Lee JH Sovari AA Fishbein MC Weiss JN Karagueuzian HS 《American journal of physiology. Heart and circulatory physiology》2012,302(11):H2331-H2340
Unlike young hearts, aged hearts are highly susceptible to early afterdepolarization (EAD)-mediated ventricular fibrillation (VF). This differential may result from age-related structural remodeling (fibrosis) or electrical remodeling of ventricular myocytes or both. We used optical mapping and microelectrode recordings in Langendorff-perfused hearts and patch-clamp recordings in isolated ventricular myocytes from aged (24-26 mo) and young (3-4 mo) rats to assess susceptibility to EADs and VF during either oxidative stress with ANG II (2 μM) or ionic stress with hypokalemia (2.7 mM). ANG II caused EAD-mediated VF in 16 of 19 aged hearts (83%) after 32 ± 7 min but in 0 of 9 young hearts (0%). ANG II-mediated VF was suppressed with KN-93 (Ca(2+)/calmodulin-dependent kinase inhibitor) and the reducing agent N-acetylcysteine. Hypokalemia caused EAD-mediated VF in 11 of 11 aged hearts (100%) after 7.4 ± 0.4 min. In 14 young hearts, however, VF did not occur in 6 hearts (43%) or was delayed in onset (31 ± 22 min, P < 0.05) in 8 hearts (57%). In patch-clamped myocytes, ANG II and hypokalemia (n = 6) induced EADs and triggered activity in both age groups (P = not significant) at a cycle length of >0.5 s. When myocytes of either age group were coupled to a virtual fibroblast using the dynamic patch-clamp technique, EADs arose in both groups at a cycle length of <0.5 s. Aged ventricles had significantly greater fibrosis and reduced connexin43 gap junction density compared with young hearts. The lack of differential age-related sensitivity at the single cell level in EAD susceptibility indicates that increased ventricular fibrosis in the aged heart plays a key role in increasing vulnerability to VF induced by oxidative and ionic stress. 相似文献
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994.
Hoofd C Devreker F Deneubourg L Deleu S Nguyen TM Sermon K Englert Y Erneux C 《Cellular signalling》2012,24(7):1461-1470
Human embryonic stem cells (hESCs) are of great hope for regenerative medicine due to their dual pluripotency and self-renewal properties. We report a comparison of inositol phosphate (InsP(s)) production in undifferentiated, differentiated hESCs and in two cancer cell lines, Ntera2 cells, a human embryonal carcinoma cell (hECC) line and HeLa cells. To evaluate the potential impact of InsP(s) in differentiation, hESCs were spontaneously differentiated in culture for two weeks. The distribution of the different InsP(s) was affected upon differentiation: the level of highly phosphorylated InsP(s) was decreased. In contrast, the total level of phosphoinositides (PI) was increased. Using real time quantitative PCR (qPCR), the mRNA expression of several enzymes of the metabolism of InsP(s) was determined: a specific increase in inositol 1,4,5-trisphosphate 3-kinase A and B (ITPKA and ITPKB) was observed upon hESCs spontaneous differentiation. Ins(1,4,5)P(3) 3-kinase activity, undetectable in undifferentiated hESCs, increased upon differentiation. The same observation was made by Western blotting using an antibody directed against human ITPKB. This is the first report showing the potential implication of soluble InsP(s) in hESCs and possible function of isoenzymes of the inositol trisphosphate 3-kinase family in differentiation. 相似文献
995.
This study examines the hypothesis that the stopping rule - a traditional postnatal sex selection method where couples decide to cease childbearing once they bear a son - plays a role in high sex ratio of last births (SRLB). The study develops a theoretical framework to demonstrate the operation of the stopping rule in a context of son preference. This framework was used to demonstrate the impact of the stopping rule on the SRLB in Vietnam, using data from the Population Change Survey 2006. The SRLB of Vietnam was high at the level of 130 in the period 1970-2006, and particularly in the period 1986-1995, when sex-selective abortion was not available. Women were 21% more likely to stop childbearing after a male birth compared with a female birth. The SRLB was highest at parity 2 (138.7), particularly in rural areas (153.5), and extremely high (181.9) when the previous birth was female. Given the declining fertility, the stopping rule has a potential synergistic effect with sex-selective abortion to accentuate a trend of one-son families in the population. 相似文献
996.
Benet M Dulman RY Suzme R de Miera EV Vega ME Nguyen T Zavadil J Pellicer A 《Journal of cellular physiology》2012,227(6):2341-2351
Previously, we have shown that wild type N-ras (wt N-ras) harbors an anti-malignant effect against mutated Ras and in tumors without Ras mutations. To investigate the molecular bases of this anti-malignant activity, we have studied the potency of this anti-malignant effect in a model system against SV40 large T antigen (SV40T). We show that wild-type N-ras (wt N-ras) counteracts the effects of SV40T in NIH3T3 cells as seen by a decrease in proliferation, anchorage independence and changes in migration. We also show that wt N-ras elicits the same anti-malignant effects in some human tumor cell lines (HT1080 and MDA-MB-231). Through mRNA and microRNA (miRNAs) expression profiling we have identified genes (decorin) and miRNAs (mir-29A, let-7b) modulated by wt N-ras potentially responsible for the anti-malignant effect. Wt N-ras appears to mediate its anti-malignant effect by downregulating some of the targets of the TGFβ pathway and decorin, which are able to reverse the inhibition of migration induced by wt N-ras. Our experiments show that the molecules that mediate the anti-malignant effect by wt N-ras appear to be different from those modulated by transforming N-ras. The components of the pathways modulated by wt N-ras mediating its anti-malignant effects are potential targets for therapeutic intervention in cancer. 相似文献
997.
Jens H. Vogel Huong Nguyen Roberto Giovannini Jolene Ignowski Steve Garger Anil Salgotra Jennifer Tom 《Biotechnology and bioengineering》2012,109(12):3049-3058
Complex biopharmaceuticals, such as recombinant blood coagulation factors, are addressing critical medical needs and represent a growing multibillion‐dollar market. For commercial manufacturing of such, sometimes inherently unstable, molecules it is important to minimize product residence time in non‐ideal milieu in order to obtain acceptable yields and consistently high product quality. Continuous perfusion cell culture allows minimization of residence time in the bioreactor, but also brings unique challenges in product recovery, which requires innovative solutions. In order to maximize yield, process efficiency, facility and equipment utilization, we have developed, scaled‐up and successfully implemented a new integrated manufacturing platform in commercial scale. This platform consists of a (semi‐)continuous cell separation process based on a disposable flow path and integrated with the upstream perfusion operation, followed by membrane chromatography on large‐scale adsorber capsules in rapid cycling mode. Implementation of the platform at commercial scale for a new product candidate led to a yield improvement of 40% compared to the conventional process technology, while product quality has been shown to be more consistently high. Over 1,000,000 L of cell culture harvest have been processed with 100% success rate to date, demonstrating the robustness of the new platform process in GMP manufacturing. While membrane chromatography is well established for polishing in flow‐through mode, this is its first commercial‐scale application for bind/elute chromatography in the biopharmaceutical industry and demonstrates its potential in particular for manufacturing of potent, low‐dose biopharmaceuticals. Biotechnol. Bioeng. 2012; 109: 3049–3058. © 2012 Wiley Periodicals, Inc. 相似文献
998.
Lipase B from Candida antarctica (CalB) is a versatile biocatalyst for various bioconversions. In this study, the thermostability of CalB was improved through the introduction of a new disulfide bridge. Analysis of the B‐factors of residue pairs in CalB wild type (CalB‐WT) followed by simple flexibility analysis of residues in CalB‐WT and its designated mutants using FIRST server were newly proposed to enhance the selective power of two computational tools (MODIP and DbD v1.20) to predict the possible disulfide bonds in proteins for the enhancement of thermostability. Five residue pairs (A162‐K308, N169‐F304, Q156‐L163, S50‐A273, and S239C‐D252C) were chosen and the respective amino acid residues were mutated to cysteine. In the results, CalB A162C‐K308C showed greatly improved thermostability while maintaining its catalytic efficiency compared to that of CalB‐WT. Remarkably, the temperature at which 50% of its activity remained after 60‐min incubation (T) of CalB A162C_K308C was increased by 8.5°C compared to that of CalB‐WT (55 and 46.5°C, respectively). Additionally, the half‐life at 50°C of CalB A162C‐K308C was 4.5‐fold higher than that of CalB‐WT (220 and 49 min, respectively). The improvement of thermostability of CalB A162C‐K308C was elucidated at the molecular level by molecular dynamics (MD) simulation. Biotechnol. Bioeng. 2012; 109:867–876. © 2011 Wiley Periodicals, Inc. 相似文献
999.
Jose Renato Pinto Aldrin V. Gomes Michelle A. Jones Jingsheng Liang Susan Nguyen Todd Miller Michelle S. Parvatiyar James D. Potter 《The Journal of biological chemistry》2012,287(44):37362-37370
Human slow skeletal troponin T (HSSTnT) shares a high degree of homology with cardiac TnT (CTnT). Although the presence of HSSTnT has not been confirmed in the heart at the protein level, detectable levels of HSSTnT mRNA have been found. Whether HSSTnT isoforms are expressed transiently remains unknown. Because transient re-expression of HSSTnT may be a potential mechanism of regulating function, we explored the effect of HSSTnT on the regulation of cardiac muscle. At least three HSSTnT isoforms have been found to exist in slow skeletal muscle: HSSTnT1 (+exons 5 and 12), HSSTnT2 (+exon 5, −exon 12), and HSSTnT3 (−exons 5 and 12). Another isoform, HSSTnT hypothetical (Hyp) (−exon 5, +exon 12), has only been found at the mRNA level. Compared with HCTnT3 (adult isoform), Tn complexes containing HSSTnT1, -2, and -3 did not alter the actomyosin ATPase activation and inhibition in the presence and absence of Ca2+, respectively. HSSTnTHyp was not evaluated as it did not form a Tn complex under a variety of conditions. Porcine papillary skinned fibers displaced with HSSTnT1, -2, or -3 and reconstituted with human cardiac troponin I and troponin C (HCTnI·TnC) complex showed a decrease in the Ca2+ sensitivity of force development and an increase in maximal recovered force (HSSTnT1 and -3) compared with HCTnT3. In contrast, HSSTnTHyp showed an increase in the Ca2+ sensitivity of force development. This suggests that re- or overexpression of specific SSTnT isoforms might have therapeutic potential in the failing heart because they increase the maximal force of contraction. In addition, circular dichroism and proteolytic digestion experiments revealed structural differences between HSSTnT isoforms and HCTnT3 and that HSSTnT1 is more susceptible to calpain and trypsin proteolysis than the other HSSTnTs. Overall, HSSTnT isoforms despite being homologues of CTnT may display distinct functional properties in muscle regulation. 相似文献
1000.
O'Dowd BF Ji X Nguyen T George SR 《Biochemical and biophysical research communications》2012,417(1):23-28
D(1) and D(2) dopamine receptors exist as heteromers in cells and brain tissue and are dynamically regulated and separated by agonist concentrations at the cell surface. We determined that these receptor pairs interact primarily through discrete amino acids in the cytoplasmic regions of each receptor, with no evidence of any D(1)-D(2) receptor transmembrane interaction found. Specifically involved in heteromer formation we identified, in intracellular loop 3 of the D(2) receptor, two adjacent arginine residues. Substitution of one of the arginine pair prevented heteromer formation. Also involved in heteromer formation we identified, in the carboxyl tail of the D(1) receptor, two adjacent glutamic acid residues. Substitution of one of the glutamic acid pair prevented heteromer formation. These amino acid pairs in D(1) and D(2) receptors are oppositely charged, and presumably interact directly by electrostatic interactions. 相似文献