全文获取类型
收费全文 | 5853篇 |
免费 | 471篇 |
国内免费 | 22篇 |
专业分类
6346篇 |
出版年
2023年 | 34篇 |
2022年 | 69篇 |
2021年 | 126篇 |
2020年 | 89篇 |
2019年 | 103篇 |
2018年 | 159篇 |
2017年 | 130篇 |
2016年 | 177篇 |
2015年 | 225篇 |
2014年 | 308篇 |
2013年 | 378篇 |
2012年 | 406篇 |
2011年 | 368篇 |
2010年 | 222篇 |
2009年 | 222篇 |
2008年 | 263篇 |
2007年 | 279篇 |
2006年 | 240篇 |
2005年 | 249篇 |
2004年 | 232篇 |
2003年 | 212篇 |
2002年 | 210篇 |
2001年 | 116篇 |
2000年 | 112篇 |
1999年 | 103篇 |
1998年 | 63篇 |
1997年 | 54篇 |
1996年 | 38篇 |
1995年 | 61篇 |
1994年 | 56篇 |
1993年 | 35篇 |
1992年 | 70篇 |
1991年 | 63篇 |
1990年 | 62篇 |
1989年 | 57篇 |
1988年 | 60篇 |
1987年 | 46篇 |
1986年 | 34篇 |
1985年 | 42篇 |
1984年 | 30篇 |
1983年 | 41篇 |
1982年 | 33篇 |
1981年 | 37篇 |
1979年 | 33篇 |
1978年 | 34篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1974年 | 32篇 |
1973年 | 25篇 |
1966年 | 21篇 |
排序方式: 共有6346条查询结果,搜索用时 0 毫秒
931.
Jan Kvíčala Václav Zamrazil Jarmila Čeřovská Jiří Bednář Jaroslav Janda 《Biological trace element research》1995,47(1-3):365-375
Blood serum selenium of 65 men and hair selenium of 77 men from three regions of the Czech Republic (CR) were analyzed by neutron activation analysis, and 202 samples of urine from the same populations were analyzed for Se by the fluorimetric method to assess selenium status of these regions. Low status (53 μg Se/L of serum and 0.29 μg Se/g lyophilized hair as means) and very low urine selenium (8.7 μg/L urine) were detected. By these data, the CR is among the countries with the lowest Se intake. A comparison of studied regions is presented. Moreover, values of serum zinc were within the reference range, but mild to moderate deficiency in the supply of iodine was detected. 相似文献
932.
Flor Y. Ramírez-Castillo Adriana C. Moreno-Flores Francisco J. Avelar-González Francisco Márquez-Díaz Josée Harel Alma L. Guerrero-Barrera 《Annals of clinical microbiology and antimicrobials》2018,17(1):34
Background
Uropathogenic Escherichia coli (UPEC) are one of the main bacteria causing urinary tract infections (UTIs). The rates of UPEC with high resistance towards antibiotics and multidrug-resistant bacteria have increased dramatically in recent years and could difficult the treatment.Methods
The aim of the study was to determine multidrug-resistant bacteria, antibiotic resistance profile, virulence traits, and genetic background of 110 E. coli isolated from community (79 isolates) and hospital-acquired (31 isolates) urinary tract infections. The plasmid-mediated quinolone resistance genes presence was also investigated. A subset of 18 isolates with a quinolone-resistance phenotype was examined for common virulence genes encoded in diarrheagenic and extra-intestinal pathogenic E. coli by a specific E. coli microarray.Results
Female children were the group most affected by UTIs, which were mainly community-acquired. Resistance to trimethoprim–sulfamethoxazole, ampicillin, and ampicillin–sulbactam was most prevalent. A frequent occurrence of resistance toward ciprofloxacin (47.3%), levofloxacin (43.6%) and cephalosporins (27.6%) was observed. In addition, 63% of the strains were multidrug-resistant (MDR). Almost all the fluoroquinolone (FQ)-resistant strains showed MDR-phenotype. Isolates from male patients were associated to FQ-resistant and MDR-phenotype. Moreover, hospital-acquired infections were correlated to third generation cephalosporin and nitrofurantoin resistance and the presence of kpsMTII gene. Overall, fimH (71.8%) and fyuA (68.2%), had the highest prevalence as virulence genes among isolates. However, the profile of virulence genes displayed a great diversity, which included the presence of genes related to diarrheagenic E. coli. Out of 110 isolates, 25 isolates (22.7%) were positive to qnrA, 23 (20.9%) to qnrB, 7 (6.4%) to qnrS1, 7 (6.4%) to aac(6′)lb-cr, 5 (4.5%) to qnrD, and 1 (0.9%) to qnrC genes. A total of 12.7% of the isolates harbored blaCTX-M genes, with blaCTX-M-15 being the most prevalent.Conclusions
Urinary tract infection due to E. coli may be difficult to treat empirically due to high resistance to commonly used antibiotics. Continuous surveillance of multidrug resistant organisms and patterns of drug resistance are needed in order to prevent treatment failure and reduce selective pressure. These findings may help choosing more suitable treatments of UTI patients in this region of Mexico.933.
Didem Şöhretoğlu Merve Yüzbaşıoğlu Baran Randolph Arroo Ayşe Kuruüzüm-Uz 《Phytochemistry Reviews》2018,17(5):973-1005
Polydatin (PLD), the 3-O-β-glucopyranoside of the well-known stilbenoid compound resveratrol, is a major compound of Fallopia japonica (Houtt.) R. Decr. (Japanese knotweed), which is widely used in traditional Chinese medicine to treat infection, inflammatory diseases and circulatory problems. It has shown a wide range of biological activities including anti-inflammatory, anti-oxidant, anti-cancer, neuroprotective, hepatoprotective, nephroprotective and immunostimulatory effects. Although resveratrol has similar beneficial effects, its low bioavailability has remained a problem. Glycosylation increases solubility of resveratrol in an aqueous environment, thus improving its bioavailability. This has led to a growing interest in PLD. Promising results obtained from bioactivity studies have boosted an intense research on this compound. The aim of this review is to give a comprehensive overview of the botanical sources, pharmacology, biosynthesis, biotechnological production, and bioactivities of PLD, and to discuss clinical studies on this compound. 相似文献
934.
Peter Sandøe Annika Patursson Nørspang Sara Vincentzen Kondrup Charlotte Reinhard Bjørnvad Björn Forkman Thomas Bøker Lund 《Anthrozo?s》2018,31(4):459-473
Cats have grown in popularity as companion animals, but there are also people who strongly dislike them. Companion cats allowed to roam freely outdoors are seen by some as a nuisance. This paper, drawing on research conducted in Denmark, aims to quantify potentially conflicting attitudes to cats among the public that may feed into cat-related conflicts and controversies. Questionnaire data were collected from a representative sample of the Danish population (n = 2,003), where 21% (n = 415) owned cats and 79% (n = 1,588) did not. In all, 65% of respondents confirmed that they liked cats, 21% reported that they did not, and 14% were undecided. The main reasons for disliking cats concerned “behavior,” not hazards such as the spread of diseases and predation. Of the 21% of the surveyed Danes who reported that they currently had a cat in the household, 72% allowed their cat to roam outdoors. Sixty percent of the respondents did not perceive this as a problem. However, the potential for conflict was demonstrated by the fact that 27% of respondents regarded outdoor roaming as problematic. Of these, about a quarter saw free-roaming cats as a big problem and as a cause of strife between neighbors. Comparatively fewer of those who owned cats saw their animals as a cause of problems. Thus, only 12% of those owning outdoor cats thought that problems were caused when their cats defecated in a neighbor’s garden, which compares with the 17% of the total population who are bothered by other people’s cats defecating in their gardens. Our data show that while the majority of Danes believe cats should be allowed to roam in public spaces, a significant minority strongly dislikes cats and would prefer restrictions on roaming. 相似文献
935.
Annerieke Sierksma Ashley Lu Evgenia Salta Elke Vanden Eynden Zsuzsanna Callaerts-Vegh Rudi D’Hooge David Blum Luc Buée Mark Fiers Bart De Strooper 《Molecular neurodegeneration》2018,13(1):54
Background
Despite diverging levels of amyloid-β (Aβ) and TAU pathology, different mouse models, as well as sporadic AD patients show predictable patterns of episodic memory loss. MicroRNA (miRNA) deregulation is well established in AD brain but it is unclear whether Aβ or TAU pathology drives those alterations and whether miRNA changes contribute to cognitive decline.Methods
miRNAseq was performed on cognitively intact (4 months) and impaired (10 months) male APPtg (APPswe/PS1L166P) and TAUtg (THY-Tau22) mice and their wild-type littermates (APPwt and TAUwt). We analyzed the hippocampi of 12 mice per experimental group (n =?96 in total), and employed a 2-way linear model to extract differentially expressed miRNAs. Results were confirmed by qPCR in a separate cohort of 4 M and 10 M APPtg and APPwt mice (n =?7–9 per group) and in human sporadic AD and non-demented control brain. Fluorescent in situ hybridization identified their cellular expression. Functional annotation of predicted targets was performed using GO enrichment. Behavior of wild-type mice was assessed after intracerebroventricular infusion of miRNA mimics.Results
Six miRNAs (miR-10a-5p, miR-142a-5p, miR-146a-5p, miR-155-5p, miR-211-5p, miR-455-5p) are commonly upregulated between APPtg and TAUtg mice, and four of these (miR-142a-5p, miR-146a-5p, miR-155-5p and miR-455-5p) are altered in AD patients. All 6 miRNAs are strongly enriched in neurons. Upregulating these miRNAs in wild-type mice is however not causing AD-related cognitive disturbances.Conclusion
Diverging AD-related neuropathologies induce common disturbances in the expression of neuronal miRNAs. 4 of these miRNAs are also upregulated in AD patients. Therefore these 4 miRNAs (miR-142a-5p, miR-146a-5p, miR-155-5p and miR-455-5p) appear part of a core pathological process in AD patients and APPtg and TAUtg mice. They are however not causing cognitive disturbances in wild-type mice. As some of these miRNA target AD relevant proteins, they may be, in contrast, part of a protective response in AD.936.
B S Vallée P Tauc J C Brochon R Maget-Dana D Lelièvre M H Metz-Boutigue N Bureaud F Schoentgen 《European journal of biochemistry》2001,268(22):5831-5841
The ability of phosphatidylethanolamine-binding protein (PEBP) to bind membranes was tested by using small and large unilamellar vesicles and monolayers composed of l-alpha-1,2-dimyristoylphosphatidylcholine, l-alpha-1,2-dimyristoylphosphatidylglycerol and l-alpha-1,2-dimyristoylphosphatidylethanolamine. PEBP only bound to model membranes containing l-alpha-1,2-dimyristoylphosphatidylglycerol; the interaction was primarily due to electrostatic forces between the basic protein and the acidic phospholipids. Further experiments indicated that the interaction was not dependent on the length and unsaturation of the phospholipid acyl chains and was not modified by the presence of cholesterol in the membrane. PEBP affinity for negatively charged membranes is puzzling considering the previous identification of the protein as a phosphatidylethanolamine-binding protein, and suggests that the association of PEBP with phospholipid membranes is driven by a mechanism other than its binding to solubilized phosphatidylethanolamine. An explanation was suggested by its three-dimensional structure: a small cavity at the protein surface has been reported to be the binding site of the polar head of phosphatidylethanolamine, while the N-terminal and C-terminal parts of PEBP, exposed at the protein surface, appear to be involved in the interaction with membranes. To test this hypothesis, we synthesized the two PEBP terminal regions and tested them with model membranes in parallel with the whole protein. Both peptides displayed the same behaviour as whole PEBP, indicating that they could participate in the binding of PEBP to membranes. Our results strongly suggest that PEBP directly interacts with negatively charged membrane microdomains in living cells. 相似文献
937.
938.
939.
The purpose of this investigation was to determine the possible relationships between anthropometrical and health-related fitness parameters in obese middle-aged women. Twenty one obese (BMI > 27 kg/m2) and 12 control (BMI < 27 kg/m2) middle-aged females (35-45 yrs) participated in this investigation. Three series of anthropometrical measurements on the right side of the body were taken according to the O-scale physique assessment system. The Heath-Carter anthropometric somatotyping method was used and the ratio of waist to hip circumferences was calculated. The body composition was measured using bioelectrical impedance method (Bodystat-500, UK). The following health-related fitness tests used were: dynamic sit-up, hand grip, sit-and-reach, single leg balance and plate tapping. Physical working capacity (PWC) was measured using single ergometer test. Obese women possessed significantly higher (p < 0.05) values for skinfold, girth and breadth measurements. While the differences in somatotype indices were not statistically significant (p > 0.05) between obese and control groups, the transformation of somatotype characteristics to the effect sizes (ESs) revealed that these differences were large (ectomorphy: ES = 1.73; endomorphy: ES = 1.64; mesomorphy: ES = 1.71). Relative aerobic fitness (VO2max/kg, calculated from PWC) and dynamic sit-up were higher (p < 0.05) in control subjects, while obese women presented significantly higher values for hand grip strength. The thicker skinfold thicknesses increased the absolute value of PWC in obese group (r = 0.39-0.57; p < 0.05). In contrast, the thinner skinfold thicknesses in suprailiac and mid-thigh significantly increased the absolute value of PWC in control women. There were only a few significant correlations between girth and breadth measures, and health-related fitness parameters. In addition, somatotype characteristics seldom influenced the results of health-related fitness tests. Stepwise multiple regression analysis demonstrated that health-related fitness test items were more dependent on the anthropometrical parameters in obese than in control women. 相似文献
940.
An efficient technique for biotyping, using disposable trays instead of glass tubes and agar instead of liquid media, is described. 相似文献