全文获取类型
收费全文 | 2496篇 |
免费 | 104篇 |
专业分类
2600篇 |
出版年
2022年 | 13篇 |
2021年 | 22篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 28篇 |
2017年 | 27篇 |
2016年 | 43篇 |
2015年 | 80篇 |
2014年 | 77篇 |
2013年 | 125篇 |
2012年 | 163篇 |
2011年 | 146篇 |
2010年 | 87篇 |
2009年 | 79篇 |
2008年 | 134篇 |
2007年 | 129篇 |
2006年 | 110篇 |
2005年 | 136篇 |
2004年 | 124篇 |
2003年 | 129篇 |
2002年 | 131篇 |
2001年 | 55篇 |
2000年 | 45篇 |
1999年 | 49篇 |
1998年 | 25篇 |
1997年 | 36篇 |
1996年 | 20篇 |
1995年 | 29篇 |
1994年 | 16篇 |
1993年 | 26篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 31篇 |
1989年 | 37篇 |
1988年 | 29篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 45篇 |
1984年 | 38篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1972年 | 11篇 |
1971年 | 14篇 |
1970年 | 15篇 |
排序方式: 共有2600条查询结果,搜索用时 46 毫秒
71.
In occidental countries, the biodegradation of synthetic detergents has become one of the important problems in relation to the water quality protection programs. Their detergent industries are going to change active ingredient in detergent formulation from the non-biodegradable tetrapropylene-derived ABS (TBS) to the biodegradable Linear Alkylate Sulfonates (LAS). In our country, cesspools are served as domestic sewage disposal systems in very many homes, so that, it is necessary to observe the biodegradability of LAS in the cesspool. 相似文献
72.
Tadao Kurata Hideo Wakabayashi Yosito Sakurai 《Bioscience, biotechnology, and biochemistry》2013,77(1):101-105
In the presence of oxygen, L-ascorbic acid sol ution (0.05 M) browned more intense1 y than dehydro-L-ascorbic acid solution (0.05 M) during storage for longer period.The mixed solution of L-ascorbic acid (ASA) and dehydro-L-ascorbic acid (DHA) with the ratio of 1:1 or 1:3 in concentration gave more intense browning than DHA solution during storage at 38°C for about 3 weeks. Essentially the same type of browning was observed in case of the mixture of ASA and DHA with D-glucose. Browning of partially oxidized ASA solution also showed substantially the same results as those mentioned above. 相似文献
73.
Mizuki Akahori Atsushi Takatori Seiji Kawamura Shinichi Itagaki Yasuhiro Yoshikawa 《Experimental Animals》2005,54(2):131-136
Non-human primates are frequently used in toxicological studies the result of which are extrapolated to humans, but background data on drug metabolism ability among monkeys derived from different countries has not been published, especially on the key enzyme, cytochrome P450 (CYP450). We assessed the amounts of hepatic CYP450 obtained from cynomolgus monkeys of different ages and from different countries in this study. There were no regional differences of total P450 content, as well as major CYP450 isozymes (CYP 1A, 2A, 2B, 2C, 2D, 2E1 and 3A4) in cynomolgus monkeys by westernblot analysis. Similarly, there were no significant differences with hybrid cynomolgus monkeys, but variations in individual values were large. As for aging, total P450 contents declined in old cynomolgus monkeys (12-32 years of age). These results indicate the usefulness of basic data of hepatic CYP450 obtained from cynomolgus monkeys of different ages and from different countries. 相似文献
74.
Yoshio Araki Kazuhiro Yoshikawa Sho Okamoto Masaki Sumitomo Mikio Maruwaka Toshihiko Wakabayashi 《BMC neurology》2010,10(1):112
Background
Moyamoya disease (MMD) is an uncommon cerebrovascular condition with unknown etiology characterized by slowly progressive stenosis or occlusion of the bilateral internal carotid arteries associated with an abnormal vascular network. MMD is a major cause of stroke, specifically in the younger population. Diagnosis is based on only radiological features as no other clinical data are available. The purpose of this study was to identify novel biomarker candidate proteins differentially expressed in the cerebrospinal fluid (CSF) of patients with MMD using proteomic analysis.Methods
For detection of biomarkers, CSF samples were obtained from 20 patients with MMD and 12 control patients. Mass spectral data were generated by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) with an anion exchange chip in three different buffer conditions. After expression difference mapping was undertaken using the obtained protein profiles, a comparative analysis was performed.Results
A statistically significant number of proteins (34) were recognized as single biomarker candidate proteins which were differentially detected in the CSF of patients with MMD, compared to the control patients (p < 0.05). All peak intensity profiles of the biomarker candidates underwent classification and regression tree (CART) analysis to produce prediction models. Two important biomarkers could successfully classify the patients with MMD and control patients.Conclusions
In this study, several novel biomarker candidate proteins differentially expressed in the CSF of patients with MMD were identified by a recently developed proteomic approach. This is a pilot study of CSF proteomics for MMD using SELDI technology. These biomarker candidates have the potential to shed light on the underlying pathogenesis of MMD.75.
76.
Fujii H Osa Y Ishihara M Hanamura S Nemoto T Nakajima M Hasebe K Mochizuki H Nagase H 《Bioorganic & medicinal chemistry letters》2008,18(18):4978-4981
Selective ring opening reaction of the N-cyclopropylmethyl group in naltrexone (1d) was effected in the presence of platinum (IV) oxide and hydrobromic acid under a hydrogen atmosphere at rt to selectively afford N-isobutyl derivative 10. The binding affinity of N-i-Bu derivative 10 for opioid receptors was 11-17 times less than that of the corresponding N-CPM compound, naltrexone (1d). However, compound 10 showed dose-dependent analgesic effects. Contrary to expectations based on previous structure-activity relationship studies for a series of N-substituted naltrexone derivatives that compound 10 would be an opioid antagonist, 10 showed dose-dependent analgesia in the mouse acetic acid writhing test (ED(50): 5.05 mg/kg, sc), indicating it was an opioid agonist. This finding may have a great influence on the drug design of opioid agonists. 相似文献
77.
Hirabayashi H Sugimoto H Matsumoto S Amano N Moriwaki T 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2011,879(32):3837-3844
Highly sensitive and accurate liquid chromatography-tandem mass spectrometry (LC/MS/MS) methods have been developed and validated for measuring digoxin (DGX), a typical P-glycoprotein probe, in human plasma, rat plasma, and rat brain. We extracted DGX and deuterium-labeled DGX (as internal standard) from sample fluids under basic conditions using acetonitrile and sodium chloride-saturated 0.1 mol/L sodium hydroxide. The upper organic layer was diluted with distilled water, and the resulting solution was injected into an LC/MS/MS system in negative ionization mode. Chromatographic separation was achieved on a C(18)-ODS column in the gradient mobile phase, which comprised 0.05% (w/v) ammonium carbonate (pH 9.0) and methanol at a flow rate of 0.7 mL/min. Regardless of the type of biological matrix, intra-day and inter-day validation tests demonstrated good linearity of calibration curves within ranges of 0.1-10 ng/mL for plasma and 0.5-50 ng/g for rat brain and gave excellent accuracy and precision of quality control samples at 4 concentration levels. Unlike existing methods, our approach uses negative ionization to avoid competitive adduct formation of DGX. Our method showed higher sensitivity and wider applicability to various types of biological matrices than existing methods. Our method will support clinical and preclinical investigation of in vivo P-glycoprotein functionality using DGX. 相似文献
78.
Katsuhiko Mikoshiba Shinichi Kohsaka Ken Takamatsu Emiko Aoki Yasuzo Tsukada 《Journal of neurochemistry》1980,34(4):835-844
Abstract: Cerebral cortex from reeler mutant mice was examined morphologically and biochemically. The sequential process of postnatal cell migration in the cerebral cortex of reeler (rl/rl) was examined morphologically. The dense cellular cortical plate lies below the molecular layer near the cerebral surface just after birth in normal mice while in reeler most of the cells are concentrated in the center of the cortex. In the cortex of adult reeler, the broad laminar structure of the neurons could be seen to form inverted positions in the cortical layers. The total wet weight, and the concentration of DNA and RNA in the pallium cerebri from reeler did not differ significantly from those in the control. As to the protein profiles of the pallium cerebri detected by SDS- polyacrylamide gel electrophoresis, no significant differences were observed. Activities of CNPase (2',3'-cyclic nucleotide 3'-phosphohydrolase), which is a myelin enzyme of CNS, and choline acetyltransferase were at the same level in both the reeler and the control. Therefore, reeler mutation does not appear to affect the genetically determined cell numbers, number of cholinergic fibers, and myelination. By autoradiographic observation of the cerebral cortex after intraperitoneal injection of [14 C]2-deoxyglucose, it was revealed that 2-deoxyglucose was incorporated intensively into the fourth layer (granular layer) of the cerebrum from the control. In reeler it was also incorporated into the granular layer but in a more widespread distribution. We conclude that terminals to the granular layer make metabolically active synapse, perhaps even in a manner inverted from normal. 相似文献
79.
The relationship between cell size, [3H]thymidine incorporation capacity, and cell surface property of human diploid fibroblasts was investigated using the concanavalin A (ConA)-mediated red blood cell (RBC) adsorption assay. Small cells in late passage populations adsorbed RBCs well with the RBC coating method (in which ConA-coated RBCs are adsorbed to fibroblasts) as did large cells of this population, while small cells in early passage populations did not. The RBC adsorption capacity of rapidly dividing cells with this method differed among young, middle-aged and old cell populations. The results suggest that temporal cell size and [3H]thymidine incorporating capacity is not a measure of the division age of human diploid cells at the individual cell level. On the other hand, RBC adsorption with the fibroblast coating method (in which RBCs are adsorbed to ConA-coated fibroblasts) occurred to non-dividing cells of the populations. Thus, the increase in RBC adsorption with this method is considered to be a reflection of the increase in non-dividing cells at phase III. Our results support the hypothesis that RBC adsorption with the RBC and fibroblast-coating methods represents a cell surface marker for division age and senescence of human diploid cells, respectively, at the individual cell level. 相似文献
80.
We reported the first case of a congenital histidine-rich glycoprotein deficiency (HRG Tokushima) in which substitution of Gly85 with Glu (G85E) in the first cystatin domain resulted in intracellular degradation and a low plasma level of HRG [Shigekiyo, T. et al. (1998) Blood 91, 128-133]. Recently, we identified the gene mutation of a second case of HRG deficiency as a Cys223 to Arg (C223R) mutation in the second cystatin domain. To investigate the molecular and cellular bases of these deficiencies, we expressed these HRG mutants in baby hamster kidney (BHK) cells. Pulse-chase experiments in the absence and presence of various proteinase inhibitors revealed that, while wild-type HRG was completely secreted during 4-h chase periods, both the G85E and C223R mutants were only partially secreted and primarily degraded within the cells. The intracellular degradation of the C223R mutant was almost completely inhibited in the presence of a proteasome inhibitor, lactacystin, carbobenzoxy-leucyl-leucyl-leucinal or N-acetyl-leucyl-leucyl-norleucinal, resulting in increased secretion of the C223R mutant, and thus implicating the proteasome system in this degradation process. In contrast, the sum of the amounts of the G85E mutant inside and outside the cells decreased during the chase periods even in the presence of the proteasome inhibitor, carbobenzoxy-leucyl-leucyl-leucinal or N-acetyl-leucyl-leucyl-norleucinal, although proteasome-specific inhibitor lactacystin and one of the cysteine protease inhibitors, E-64-d, prevented the intracellular degradation. These results suggested that intracellular degradation of G85E HRG occurred to some extent through a hitherto unknown mechanism. Similar studies involving recombinant mutants in which Gly85 or Cys223 was replaced with several other amino acids revealed that proteins with mutations leading to the destruction of the predicted b-sheet structure of the cystatin domains were eliminated by the intracellular quality control system. 相似文献