全文获取类型
收费全文 | 1883篇 |
免费 | 55篇 |
国内免费 | 47篇 |
出版年
2023年 | 15篇 |
2022年 | 29篇 |
2021年 | 34篇 |
2020年 | 27篇 |
2019年 | 28篇 |
2018年 | 35篇 |
2017年 | 29篇 |
2016年 | 38篇 |
2015年 | 59篇 |
2014年 | 146篇 |
2013年 | 267篇 |
2012年 | 160篇 |
2011年 | 156篇 |
2010年 | 123篇 |
2009年 | 87篇 |
2008年 | 83篇 |
2007年 | 79篇 |
2006年 | 77篇 |
2005年 | 61篇 |
2004年 | 47篇 |
2003年 | 52篇 |
2002年 | 25篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 26篇 |
1998年 | 22篇 |
1997年 | 27篇 |
1996年 | 22篇 |
1995年 | 20篇 |
1994年 | 11篇 |
1993年 | 14篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1972年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有1985条查询结果,搜索用时 31 毫秒
101.
Simultaneous and continuous measurements of extracellular pH, potassium (K(+)), and lactate (L(-)) in ischemic rabbit papillary muscle are presented for the first time. Potentiometric pH and K(+) sensors and an amperometric lactate biosensor were used. These miniature electrodes were previously developed and individually tested for this purpose. The pH sensor was based on an iridium oxide layer electrodeposited on a planar platinum electrode fabricated on a flexible substrate. The potentiometric K(+) sensor was based on a polymeric membrane and valinomycin ionophore. The L(-) biosensor was based on lactate oxidase and an organic conducting salt polarized at 0.15V vs Ag/AgCl reference electrode. The utility of this novel analytical system to cardiovascular research was demonstrated by using the system to study the interrelationship of cellular K(+) and lactate loss in ischemic myocardium, and the role of extracellular pH and buffer capacity on this relationship. The results indicated: (i) sequential brief episodes of ischemia produced reproducible trends of L(-), pH, and K(+) changes during the first three episodes, (ii) extracellular L(-) increased with increasing buffer capacity of extracellular compartment, (iii) the patterns of extracellular L(-) and K(+) changes were not related directly, and (iv) L(-) transport and lactic acid diffusion were not the primary cause of extracellular acidosis during ischemia. 相似文献
102.
Popescu GA 《Journal of cellular and molecular medicine》2002,6(4):661-664
Now it is quite usual to use real computers to simulte virtual cells. I suggest that real cells (e.g. cells cultured in vitro ) might be considered and used as molecular automata. As an imaginary experience, a molecular automata can be built, using real cells and a chemical inert molecule. I suggest that one could be able to test statistical properties of a 2D gas trapped in a box using this sort of automata. Moreover, I would conjecture that any possible algorithm can be implemented in such molecular automata. 相似文献
103.
Many diseases such as cardiac arrhythmia, diabetes, and chronic alcoholism are associated with a marked decrease of plasma and parenchymal Mg(2+), and Mg(2+) administration is routinely used therapeutically. This study uses isolated rat hepatocytes to ascertain if and under which conditions increases in extracellular Mg(2+) result in an increase in intracellular Mg(2+). In the absence of stimulation, changing extracellular Mg(2+) had no effect on total cellular Mg(2+) content. By contrast, carbachol or vasopressin administration promoted an accumulation of Mg(2+) that increased cellular Mg(2+) content by 13.2 and 11.8%, respectively, and stimulated Mg(2+) uptake was unaffected by the absence of extracellular Ca(2+). Mg(2+) efflux resulting from stimulation of alpha- or beta-adrenergic receptors operated with a Mg(2+):Ca(2+) exchange ratio of 1. These data indicate that cellular Mg(2+) uptake can occur rapidly and in large amounts, through a process distinct from Mg(2+) release, but operating only upon specific hormonal stimulation. 相似文献
104.
Heintel T Breinig F Schmitt MJ Meyerhans A 《FEMS immunology and medical microbiology》2003,39(3):279-286
The human cellular immune response against 14 distantly related yeast species was analyzed by intracellular cytokine staining of lymphocytes after ex vivo stimulation of whole blood. While the CD4 T cell response was marginal, extensive MHC class I-restricted CD8 T cell responses were detected against a number of species including spoiling, environmental and human pathogenic yeasts. The yeast-specific CD8 T cells expressed interferon-gamma but lacked expression of CD27 and CCR7, indicating that they were end-differentiated effector memory cells. Mainly intact yeast cells rather than spheroplasts were able to induce cytokine expression in T cells demonstrating that the dominant immunogens were located in the yeast cell wall. Together these data underline the importance of the cellular immune response in protecting humans against yeast and fungal infections. And, from another perspective, recombinant yeast suggests itself as a potential vaccine candidate to efficiently induce antigen-specific CD8 T cell responses. 相似文献
105.
Cancer vaccines: single-epitope anti-idiotype vaccine versus multiple-epitope antigen vaccine 总被引:5,自引:0,他引:5
Maruyama H Zaloudik J Li W Sperlagh M Koido T Somasundaram R Scheck S Prewett M Herlyn D 《Cancer immunology, immunotherapy : CII》2000,49(3):123-132
In this study, we compared the immunogenicity and tumor-protective activity of anti-idiotypic antibodies mimicking a single
tumor-associated epitope and tumor-associated antigen expressing multiple potentially immunogenic epitopes. We focused our
study on the colorectal-carcinoma(CRC)-associated antigen GA733 (also known as CO17-1A/KS1-4/KSA/EpCAM). Monoclonal anti-idiotypic
antibody (Ab2) BR3E4 was produced against murine anti-CRC mAb CO17-1A (Ab1) in rats. Full-length native GA733 protein was
isolated from human tumor cells, and the extracellular domain protein (GA733-2E) was isolated from supernatants of recombinant
baculovirus-infected insect cells by immunoafffinity chromatography. The immunomodulatory activity of the Ab2 was compared
with that of the antigen, both in rabbits and in mice. Mice, like humans but not rabbits, express a GA733 antigen homologue
on some of their normal tissues. Thus, these in vivo models allow the comparison of the immunogenicity of Ab2 and antigen
in the presence (mice) and absence (rabbits) of normal tissue expression and immunological tolerance of the GA733 antigen
homologue. In rabbits, aluminum-hydroxide(alum)-precipitated native GA733 antigen was superior to alum-precipitated Ab2 in
inducing specific humoral immunity. In mice, alum-precipitated recombinant GA733-2E antigen, but not alum-precipitated Ab2,
induced specific humoral immunity. However, when the Ab2 was administered to mice in Freund's complete adjuvant, specific
humoral immune responses were elicited. Ab2 in complete Freund's adjuvant and GA733-2E in alum were compared for their capacity
to induce antigen-specific cellular immunity in mice. Whereas lymphoproliferative responses were obtained with the recombinant
antigen only, delayed-type hypersensitivity responses were obtained with both recombinant antigen and Ab2, although these
responses were lower than after antigen immunization. The recombinant antigen in alum did not protect mice against challenge
with antigen-positive syngeneic murine CRC cells. Similar studies with Ab2 BR3E4 mimicking the CO17-1A epitope were not possible
because the tumor cells do not express this epitope after transfection with the human GA733-2 cDNA. However, similar studies
with Ab2 mimicking the epitope defined by mAb GA733, which is expressed by the transfected tumor cells, indicated a lack of
tumor-protective activity of this Ab2. In contrast, the full-length antigen expressed by recombinant adenovirus inhibited
the growth of established tumors in mice. In conclusion, soluble antigen is a more potent modulator of humoral and cellular
immune responses than Ab2, both administered in adjuvant. However, for induction of protective immunity, the immunogenicity
of the antigen must be further enhanced, e.g., by expression of the antigen in a viral vector.
Received: 27 December 1999 / Accepted: 27 January 2000 相似文献
106.
Cellular compartmentation of cadmium and zinc in relation to other elements in the hyperaccumulator Arabidopsis halleri 总被引:21,自引:0,他引:21
The cellular compartmentation of elements was analysed in the Zn hyperaccumulator Arabidopsis halleri (L.) O'Kane & Al-Shehbaz (=Cardaminopsis halleri) using energy-dispersive X-ray microanalysis of frozen-hydrated tissues. Quantitative data were obtained using oxygen as
an internal standard in the analyses of vacuoles, whereas a peak/background ratio method was used for quantification of elements
in pollen and dehydrated trichomes. Arabidopsis halleri was found to hyperaccumulate not only Zn but also Cd in the shoot biomass. While large concentrations of Zn and Cd were found
in the leaves and roots, flowers contained very little. In roots grown hydroponically, Zn and Cd accumulated in the cell wall
of the rhizodermis (root epidermis), mainly due to precipitation of Zn/Cd phosphates. In leaves, the trichomes had by far
the largest concentrations of Zn and Cd. Inside the trichomes there was a striking sub-cellular compartmentation, with almost
all the Zn and Cd being accumulated in a narrow ring in the trichome base. This distribution pattern was very different from
that for Ca and P. The epidermal cells other than trichomes were very small and contained lower concentrations of Zn and Cd
than mesophyll cells. In particular, the concentrations of Cd and Zn in the mesophyll cells increased markedly in response
to increasing Zn and Cd concentrations in the nutrient solution. This indicates that the mesophyll cells in the leaves of
A. halleri are the major storage site for Zn and Cd, and play an important role in their hyperaccumulation.
Received: 4 April 2000 / Accepted: 16 May 2000 相似文献
107.
Tsukasa Tameyasu Naokata Ishii Noboru Oishi Mitsuyo Shimada Ibuki Shirakawa Tsuyoshi Akimoto Naoto Yamamoto Shoichi Kosuge Haruo Sugi 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》1998,120(4):731-736
To investigate characteristics of ATP-dependent sliding of a non-muscle cell myosin, obtained from a cellular slime mold Dictyostelium discoideum, on actin filament, we prepared hybrid thick filaments, in which Dictyostelium myosin was regularly arranged around paramyosin filaments obtained from a molluscan smooth muscle. A single to a few hybrid filaments were attached to a polystyrene bead (diameter, 4.5 μm; specific gravity, 1.5), and the filaments were made to slide on actin filament arrays (actin cables) in the internodal cell of an alga Chara corallina, mounted on the rotor of a centrifuge microscope. The filament-attached bead was observed to move with a constant velocity under a constant external load for many seconds. The steady-state force–velocity relation of Dictyostelium myosin sliding on actin cables was hyperbolic in shape except for large loads ≤0.7–0.8 P0, being qualitatively similar to that of skeletal muscle fibres, despite a considerable variation in the number of myosin molecules interacting with actin cables. Comparison of the P–V curves between Dictyostelium myosin and muscle myosins sliding on actin cables suggests that the time of attachment to actin in a single attachment–detachment cycle is much longer in Dictyostelium myosin than in muscle myosins. 相似文献
108.
摘要 目的:探讨右美托咪定联合舒芬太尼术后镇痛对卵巢癌根治术患者细胞免疫功能和炎症应激反应的影响。方法:根据随机数字表法将2020年2月至2023年2月期间陕西省肿瘤医院120例择期行卵巢癌根治术的患者分为对照组(n=60,术后镇痛药物选用舒芬太尼)和研究组(n=60,术后镇痛药物选用右美托咪定联合舒芬太尼)。对比两组镇静(Ramsay镇静评分)、细胞免疫功能[CD3+、CD4+、CD8+、CD4+/CD8+]、镇痛情况[视觉模拟评分法(VAS)]、不良反应、炎症应激反应[白细胞介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)、皮质醇(Cor)和去甲肾上腺素(NE)]变化情况。结果:与对照组术后6 h、12 h、24 h、48 h 相比,研究组同时间点VAS评分更低,Ramsay镇静评分更高(P<0.05)。与对照组术后24 h相比,研究组同时间点CD3+、CD4+、CD4+/CD8+更高,CD8+更低(P<0.05)。两组不良反应发生率组间对比未见差异(P>0.05)。与对照组术后24 h相比,研究组同时间点IL-6、TNF-α、Cor、NE更低(P<0.05)。结论:右美托咪定联合舒芬太尼用于卵巢癌根治术患者术后镇痛,镇静、镇痛效果显著,同时还可减轻机体炎症应激反应,缓解免疫抑制。 相似文献
109.
细胞信号网络对于外界环境的干扰表现出优良的鲁棒性,但是其维持功能鲁棒的内在机制尚未明确,本文研究了细胞信号网络功能鲁棒性的拓扑特征。选择布尔网络模型模拟细胞网络的动态行为,利用网络节点状态的扰动模拟外界环境干扰。基于演化策略探寻不同网络拓扑的功能并分析其在干扰环境下的鲁棒性,采用埃德尔曼提出的基于信息论的计算方法评估网络拓扑的简并度、冗余度和复杂度等拓扑属性,对比分析它们与功能鲁棒度的相关性及作用机理。结果显示,在网络模型的演化过程中,其拓扑简并度与功能鲁棒度显著正相关,相关性水平高于拓扑冗余度与鲁棒度的相关性。并且,随着鲁棒度的提升,网络的节点数和复杂度也随之升高,同样简并度与网络的节点数和复杂度的相关性高于拓扑冗余度与网络的节点数和复杂度的相关性。这说明增加的网络节点以简并的方式同时提高了网络拓扑的鲁棒度和复杂度。因此,细胞网络功能鲁棒性的拓扑特征是简并而不是冗余,简并为解决生物系统的复杂问题提供了有效手段,为人工系统的可靠性设计提供有益的借鉴。 相似文献
110.
Carolina Amália Barcellos Silva Elizabeth Ferreira Martinez Ana Paula Dias Demasi Albina Altemani Jeruza Pinheiro da Silveira Bossonaro Ney Soares Araújo Vera Cavalcanti de Araújo 《Journal of cell communication and signaling》2015,9(3):255-265
During tumor invasion, benign myoepithelial cells of carcinoma ex-pleomorphic adenoma (CXPA) surround malignant epithelial cells and disappear. The mechanisms involved in the death and disappearance of these myoepithelial cells were investigated via analysis of the expression of regulatory proteins for apoptosis, autophagy and cellular senescence in an in situ in vitro model. Protein expression relating to apoptosis (Bax, Bcl-2, Survivin), autophagy (Beclin-1, LC3B) and cellular senescence (p21, p16) was evaluated using indirect immunofluorescence. β-galactosidase expression was assessed via histochemistry. Biopsies of CXPA (ex vivo) allowed immunhistochemical evaluation of p21 and p16, whilst LC3B, p21 and p16 protein expression was analyzed by western blotting. In the in vitro model, the myoepithelial cells were positive for LC3B (cytoplasm) and p21 (nucleus), whilst in vivo positivity for p21 and p16 was observed. In vitro, β-galactosidase activity increased in the myoepithelial cells over time. Western blotting analysis revealed an increased LC3B, p16 and p21 expression in the myoepithelial cells with previous contact with the malignant cells when compared with those without contact. The investigation of behavior of benign myoepithelial cells in ductal areas of CXAP revealed that the myoepithelial cells are involved in the autophagy-senescence phenotype that subsequently leads to their disappearance. 相似文献