全文获取类型
收费全文 | 1262篇 |
免费 | 37篇 |
专业分类
1299篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 17篇 |
2016年 | 25篇 |
2015年 | 27篇 |
2014年 | 42篇 |
2013年 | 72篇 |
2012年 | 84篇 |
2011年 | 89篇 |
2010年 | 59篇 |
2009年 | 44篇 |
2008年 | 67篇 |
2007年 | 78篇 |
2006年 | 98篇 |
2005年 | 87篇 |
2004年 | 84篇 |
2003年 | 85篇 |
2002年 | 85篇 |
2001年 | 19篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1978年 | 9篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1956年 | 2篇 |
排序方式: 共有1299条查询结果,搜索用时 15 毫秒
81.
Janusz Błaszkowski 《Mycorrhiza》1994,4(4):173-181
Spores of Acaulospora dilatata and Scutellospora dipurpurascens found in Poland are described and illustrated and their occurrence and distribution are characterized and mapped. Spores of Acaulospora dilatata from Poland do not differ from those originally described in the United States of America. The germination shield found in a number of spores is described and illustrated, and compared with that occurring in members of the genus Scutellospora. Acaulospora dilatata was found in five of the 303 soil samples taken from around the roots of Ammophila arenaria colonizing maritime sand dunes of the Sowinski National Park. Polish specimens of S. dipurpurascens are similar in size, wall structure, and reaction in Melzer's reagent to those described from the type localized in the United States of America. However, some spores from Poland have a thicker wall, greater sporogenous cells, and are somewhat darker coloured. They were recovered from 34 soils sampled from forests, gardens, sand dunes, and both cultivated and uncultivated soils. S. dipurpurascens was commonly associated with different plants of the Hel Peninsula and occurred regularly among the roots of Ammophila arenaria growing in the Slowinski National Park. Both species were found for the first time in Poland and are probably new to Europe. 相似文献
82.
83.
Zubrzak P Banaś A Kaczmarek K Leplawy MT Sochacki M Kowalski ML Szkudlińska B Zabrocki J Di Lello P Isernia C Saviano M Pedone C Benedetti E 《Biopolymers》2005,80(2-3):347-356
Linear and cyclic cyclolinopeptide A (CLA) analogues containing alpha-hydroxymethylleucine (HmL) in positions 1, 4, and 1&4, and alpha-hydroxymethylvaline (HmV) in position 5, were synthesized by the solid-phase peptide strategy and cyclized with the 1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide/1-hydroxy-7-azabenzotriazole (EDC/HOAt) reagent. The peptides were examined for their immunosuppressive activity in the lymphocyte proliferation assays (LPA). Only HmL-containing peptides demonstrated at about 25% lower immunosuppressive activity, but they are four times more soluble in water solutions than the native CLA. It seems from the LPA results that peptide [(HmL4)CLA] is the most promising for further studies. This peptide was characterized in solution, at room temperature in CDCl3, and the conformation compared with that observed for CLA in the solid state. 相似文献
84.
Beata S. Lipska Irena Balasz-Chmielewska Lucyna Morzuch Kacper Wasielewski Dominika Vetter Halina Borzecka Dorota Drozdz Agnieszka Firszt-Adamczyk Ewa Gacka Tomasz Jarmolinski Joanna Ksiazek Elzbieta Kuzma-Mroczkowska Mieczyslaw Litwin Anna Medynska Magdalena Silska Maria Szczepanska Marcin Tkaczyk Anna Wasilewska Franz Schaefer Aleksandra Zurowska Janusz Limon 《Journal of applied genetics》2013,54(3):327-333
Hereditary nephrotic syndrome is caused by mutations in a number of different genes, the most common being NPHS2. The aim of the study was to identify the spectrum of NPHS2 mutations in Polish patients with the disease. A total of 141 children with steroid-resistant nephrotic syndrome (SRNS) were enrolled in the study. Mutational analysis included the entire coding sequence and intron boundaries of the NPHS2 gene. Restriction fragment length polymorphism (RFLP) and TaqMan genotyping assay were applied to detect selected NPHS2 sequence variants in 575 population-matched controls. Twenty patients (14 %) had homozygous or compound heterozygous NPHS2 mutations, the most frequent being c.1032delT found in 11 children and p.R138Q found in four patients. Carriers of the c.1032delT allele were exclusively found in the Pomeranian (Kashubian) region, suggesting a founder effect origin. The 14 % NPHS2 gene mutation detection rate is similar to that observed in other populations. The heterogeneity of mutations detected in the studied group confirms the requirement of genetic testing the entire NPHS2 coding sequence in Polish patients, with the exception of Kashubs, who should be initially screened for the c.1032delT deletion. 相似文献
85.
86.
Gyrd-Hansen M Darding M Miasari M Santoro MM Zender L Xue W Tenev T da Fonseca PC Zvelebil M Bujnicki JM Lowe S Silke J Meier P 《Nature cell biology》2008,10(11):1309-1317
The covalent attachment of ubiquitin to target proteins influences various cellular processes, including DNA repair, NF-kappaB signalling and cell survival. The most common mode of regulation by ubiquitin-conjugation involves specialized ubiquitin-binding proteins that bind to ubiquitylated proteins and link them to downstream biochemical processes. Unravelling how the ubiquitin-message is recognized is essential because aberrant ubiquitin-mediated signalling contributes to tumour formation. Recent evidence indicates that inhibitor of apoptosis (IAP) proteins are frequently overexpressed in cancer and their expression level is implicated in contributing to tumorigenesis, chemoresistance, disease progression and poor patient-survival. Here, we have identified an evolutionarily conserved ubiquitin-associated (UBA) domain in IAPs, which enables them to bind to Lys 63-linked polyubiquitin. We found that the UBA domain is essential for the oncogenic potential of cIAP1, to maintain endothelial cell survival and to protect cells from TNF-alpha-induced apoptosis. Moreover, the UBA domain is required for XIAP and cIAP2-MALT1 to activate NF-kappaB. Our data suggest that the UBA domain of cIAP2-MALT1 stimulates NF-kappaB signalling by binding to polyubiquitylated NEMO. Significantly, 98% of all cIAP2-MALT1 fusion proteins retain the UBA domain, suggesting that ubiquitin-binding contributes to the oncogenic potential of cIAP2-MALT1 in MALT lymphoma. Our data identify IAPs as ubiquitin-binding proteins that contribute to ubiquitin-mediated cell survival, NF-kappaB signalling and oncogenesis. 相似文献
87.
Katarzyna Oszajca Konrad Wroński Grażyna Janiszewska Małgorzata Bieńkiewicz Jacek Bartkowiak Janusz Szemraj 《Molecular biology reports》2014,41(5):2859-2864
The most important feature of abdominal aortic aneurysm (AAA) pathogenesis is an enzymatic degradation of elastic lamellae and extracellular matrix proteins particularly with participation of matrix metalloproteinases. Plasmin, which is responsible for the dissolution of fibrin in blood vessels, plays also a key role in the cascade for activation of the metalloproteinases. The purpose of this study was to evaluate the influence of selected polymorphisms in genes coding for tissue plasminogen activator (?7351 C/T polymorphism), urokinase-type plasminogen activator (1788 C/T polymorphism) and plasminogen activator inhibitor 1 (?675 4G/5G and ?844 G/A polymorphism) on the susceptibility to AAA. We performed a case–control study of 153 polish patients hospitalized due to AAA and compared them with matched healthy control subjects. The polymorphisms were ascertained through genotyping by polymerase chain reaction and restriction digestion of amplified fragments or through high-resolution melting analysis. In this study we have found lower frequency of wild-type GG genotype of the ?844G/A PAI-1 polymorphism in cases than in controls, what may suggest the protective effect of this genotype for the risk of AAA development. None of the remaining polymorphisms tested were associated with AAA occurrence. 相似文献
88.
Katarzyna Gach Janusz Szemraj Anna Wyrębska Anna Janecka 《Molecular biology reports》2011,38(2):1231-1236
Matrix metalloproteinases (MMPs) are proteolytic enzymes involved in degradation of extracellular matrix, a process that initiates
uncontrolled spread of proliferating cancer cells and therefore plays a crucial role in cancer invasion and metastasis. Compounds
able to modulate MMP activity may become important tools in cancer research. In the present study we examined the effect of
two μ-selective opioids, morphine and endomorphin-2 (EM-2) on the production of MMP-2 and MMP-9 in MCF-7 cells. We report
that both opioids time- and concentration-dependently inhibited the expression and secretion of these MMPs. The observed effect
was not reversed by naloxone (Nal). Further experiments showed that morphine and EM-2 decreased endothelial nitric oxide synthase
(eNOS) mRNA level and nitric oxide (NO) secretion in MCF-7 cells. These findings indicate that attenuation of MMP secretion
by opioids was not mediated by opioid receptors but was under the control of nitric oxide system. 相似文献
89.
Janusz Janiszewski Dietmar Otto 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1988,162(6):739-746
1. | Intracellular recordings of suboesophageal neurons were performed in the cricketGryllus bimaculatus during applied changes of head temperature in the range 8 to 32.5 °C. The temperature was controlled by perfusing the head with Ringer solution of appropriate temperature. Subsequent staining with Lucifer Yellow revealed descending, ascending or T-shaped cells with ventrally located somata (Fig. 1). |
2. | In 6 out of 7 neurons recorded (Fig. 1, neurons A, B, C, D, E, G) the firing rate was correlated with abdominal ventilatory pumping (Fig. 2a, b). These neurons also received input from cereal sensory hairs (Fig. 2c). Furthermore, one of them (Fig. 1, neuron A) showed responses to auditory (Fig. 2d) and another (Fig. 1, neuron E) to visual input (Fig. 2e). |
3. | Activity of every tested neuron was correlated with the temperature of the perfusing Ringer solution: the amplitude and duration of spikes and excitatory postsynaptic potentials increased with cooling (Fig. 3). Two types of temperature-dependent changes in firing rate were identified. In type I the spiking rate was higher at higher temperature (Figs. 4a, b; 5). In type II spiking rate was related to the direction of temperature change (Fig. 4c, d). |
4. | The possible involvement of one of the recorded cells (Fig. 1, neuron F) in thermoreception processes is discussed. Activity of this neuron was not related to the rhythm of abdominal ventilatory pumping, nor did the cell receive cereal, visual or auditory input. Its activity was related mainly to the direction of temperature changes i.e. with an increase in firing rate during cooling, independent of the temperature at which the cooling started and with a transient decrease in firing rate during warming from starting point of 10 °C. |
90.