全文获取类型
收费全文 | 491篇 |
免费 | 30篇 |
出版年
2022年 | 6篇 |
2021年 | 4篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 19篇 |
2015年 | 5篇 |
2014年 | 16篇 |
2013年 | 28篇 |
2012年 | 26篇 |
2011年 | 39篇 |
2010年 | 19篇 |
2009年 | 15篇 |
2008年 | 32篇 |
2007年 | 28篇 |
2006年 | 31篇 |
2005年 | 29篇 |
2004年 | 27篇 |
2003年 | 14篇 |
2002年 | 14篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1972年 | 8篇 |
1971年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有521条查询结果,搜索用时 15 毫秒
361.
Paul J. Emmerson Mary J. Clark Fedor Medzihradsky Ann E. Remmers 《Journal of neurochemistry》1999,73(1):289-300
The influence of membrane microviscosity on mu-opioid agonist and antagonist binding, as well as agonist efficacy, was examined in membranes prepared from SH-SY5Y cells and from a C6 glioma cell line stably expressing the rat mu-opioid receptor (C6mu). Addition of cholesteryl hemisuccinate (CHS) to cell membranes increased membrane microviscosity and reduced the inhibitory effect of sodium and guanine nucleotides on the affinity of the full agonists sufentanil and [D-Ala2,N-MePhe4,Gly-ol5]enkephalin (DAMGO) for the mu-opioid receptor. Binding of the antagonists [3H]naltrexone and [3H]diprenorphine and the partial agonist nalbuphine was unaffected by CHS. The effect of CHS on agonist binding was reversed by subsequent addition of cis-vaccenic acid, suggesting that the effect of CHS is the result of increased membrane microviscosity and not a specific sterol-receptor interaction. CHS addition increased the potency of DAMGO to stimulate guanosine-5'-O-(3-[35S]thio)triphosphate binding by fourfold, whereas the potency of nalbuphine was unaffected. However, nalbuphine efficacy relative to that of the full agonist DAMGO was strongly increased in CHS-treated membranes compared with that in control membranes. Membrane rigidification also resulted in an increased efficacy for the partial agonists meperidine, profadol, and butorphanol relative to that of DAMGO as measured by agonist-stimulated GTPase activity in control and CHS-modified membranes. These findings support a regulatory role for membrane microviscosity in receptor-mediated G protein activation. 相似文献
362.
V. P. Sedel’nikov E. I. Lapshina A. Yu. Korolyuk V. I. Valutskii N. B. Ermakov E. A. Ershova N. I. Makunina T. V. Mal’tseva 《Contemporary Problems of Ecology》2008,1(2):153-167
An ecophytocenotic map has been compiled for southern Siberia at a scale of 1 : 1 000 000. The legend for mountainous areas includes information on the vegetation of the mapped units and environmental conditions (Σ t > 10°, annual precipitation, altitudes above sea, and topographic features). 相似文献
363.
Cynthia Shaheen Cameron Hastie Kimberly Metera Shane Scott Zhi Zhang Sitong Chen Gracia Gu Lisa Weber Brian Munsky Fedor Kouzine David Levens Craig Benham Sabrina Leslie 《Nucleic acids research》2022,50(5):2754
Many cellular processes occur out of equilibrium. This includes site-specific unwinding in supercoiled DNA, which may play an important role in gene regulation. Here, we use the Convex Lens-induced Confinement (CLiC) single-molecule microscopy platform to study these processes with high-throughput and without artificial constraints on molecular structures or interactions. We use two model DNA plasmid systems, pFLIP-FUSE and pUC19, to study the dynamics of supercoiling-induced secondary structural transitions after perturbations away from equilibrium. We find that structural transitions can be slow, leading to long-lived structural states whose kinetics depend on the duration and direction of perturbation. Our findings highlight the importance of out-of-equilibrium studies when characterizing the complex structural dynamics of DNA and understanding the mechanisms of gene regulation. 相似文献
364.
Malý MA Tomasov P Hájek P Blasko P Hrachovinová I Salaj P Veselka J 《Physiological research / Academia Scientiarum Bohemoslovaca》2007,56(6):685-695
The tissue factor (TF) is one of the most important regulators of arterial thrombosis. Because arterial thrombosis is the pathophysiologic background of acute coronary syndrome, the possible impact of blocking the arterial thrombosis on its onset is a challenging problem. The investigations of TF brought a new concept of "cell-based coagulation model" which highlighted the question of blood-borne TF as a source of TF in circulating blood. In this review we summarize essential information on the pathophysiology, molecular structure, expression and distribution of TF and we propose a novel concept of blood-borne TF, suggesting the possibilities of inhibition of the coagulation cascade with newly synthetized drugs. 相似文献
365.
Melichar B Solichová D Melicharová K Malírová E Cermanová M Zadák Z 《The International journal of biological markers》2006,21(3):190-198
In previous studies, mostly in patients with early stage colorectal carcinoma, neopterin, an indicator of systemic immune activation, has been associated with poor prognosis. The aim of the present study was to evaluate urinary neopterin in patients with advanced or metastatic colorectal carcinoma treated with chemotherapy. A retrospective analysis was performed of urinary neopterin, determined by high-performance liquid chromatography, in 88 patients with advanced or metastatic colorectal carcinoma. Peripheral blood cell count and serum carcinoembryonic antigen (CEA) were determined in 72 patients before the start of chemotherapy. Urinary neopterin in colorectal carcinoma patients was significantly increased compared to controls, but lower than in patients with inflammatory bowel disease. Neopterin correlated significantly with serum CEA, age, peripheral blood leukocyte and platelet counts. The median survival of colorectal carcinoma patients with urinary neopterin below 214 micromol/mol creatinine was significantly longer compared to that of patients with higher neopterin concentrations (median 18 vs 5 months, log-rank test p=0.003). CEA and hemoglobin were also associated with survival in univariate analysis, but in multivariate analysis only urinary neopterin and serum CEA were independent predictors of survival. High urinary neopterin during follow-up was also predictive of poor prognosis. 相似文献
366.
This article evaluates the implications of uncertainty in the life cycle (LC) energy efficiency and greenhouse gas (GHG) emissions of rapeseed oil (RO) as an energy carrier displacing fossil diesel (FD). Uncertainties addressed include parameter uncertainty as well as scenario uncertainty concerning how RO coproduct credits are accounted for (uncertainty due to modeling choices). We have carried out an extensive data collection to build an LC inventory accounting for parameter uncertainty. Different approaches for carbon stock changes associated with converting set‐aside land to rapeseed cultivation have been considered, which result in different values: from ?0.25 t C/ha.yr (carbon uptake by the soil in tonnes per hectare year) to 0.60 t C/ha.yr (carbon emission). Energy renewability efficiency and GHG emissions of RO are presented, which show the influence of parameter versus scenario uncertainty. Primary energy savings and avoided GHG emissions when RO displaces FD have also been calculated: Avoided GHG emissions show considerably higher uncertainty than energy savings, mainly due to land use (nitrous oxide emissions from soil) and land use conversion (carbon stock changes). Results demonstrate the relevance of applying uncertainty approaches; emphasize the need to reduce uncertainty in the environmental life cycle modeling, particularly GHG emissions calculation; and show the importance of integrating uncertainty into the interpretation of results. 相似文献
367.
368.
Kotulák T Drápalová J Kopecký P Lacinová Z Kramář P Říha H Netuka I Malý J Housa D Bláha J Svačina Š Haluzík M 《Physiological research / Academia Scientiarum Bohemoslovaca》2011,60(5):757-767
We studied the changes in serum fibroblast growth factor-21 (FGF-21) concentrations, its mRNA, and protein expression in skeletal muscle and adipose tissue of 15 patients undergoing cardiac surgery. Blood samples were obtained: prior to initiation of anesthesia, prior to the start of extracorporeal circulation, upon completion of the surgery, and 6, 24, 48, and 96 hours after the end of the surgery. Tissue sampling was performed at the start and end of surgery. The mean baseline serum FGF-21 concentration was 63.1 (43.03-113.95) pg/ml and it increased during surgery with peak 6 hours after its end [385.5 (274.55-761.65) pg/ml, p < 0.001], and returned to baseline value [41.4 (29.15-142.83) pg/ml] 96 hours after the end of the surgery. Serum glucose, insulin, CRP, IL-6, IL-8, MCP-1, and TNF-alpha concentrations significantly increased during the surgery. Baseline FGF-21 mRNA expression in skeletal muscle was higher than in both adipose tissue depots and it was not affected by the surgery. Epicardial fat FGF-21 mRNA increased after surgery. Muscle FGF-21 mRNA positively correlated with blood glucose levels at the end of the surgery. Our data suggest a possible role of FGF-21 in the regulation of glucose metabolism and insulin sensitivity in surgery-related stress. 相似文献
369.
370.