全文获取类型
收费全文 | 7746篇 |
免费 | 691篇 |
国内免费 | 1篇 |
出版年
2023年 | 27篇 |
2022年 | 18篇 |
2021年 | 152篇 |
2020年 | 93篇 |
2019年 | 116篇 |
2018年 | 156篇 |
2017年 | 118篇 |
2016年 | 255篇 |
2015年 | 434篇 |
2014年 | 472篇 |
2013年 | 520篇 |
2012年 | 682篇 |
2011年 | 734篇 |
2010年 | 501篇 |
2009年 | 380篇 |
2008年 | 541篇 |
2007年 | 517篇 |
2006年 | 456篇 |
2005年 | 437篇 |
2004年 | 411篇 |
2003年 | 350篇 |
2002年 | 380篇 |
2001年 | 74篇 |
2000年 | 45篇 |
1999年 | 73篇 |
1998年 | 89篇 |
1997年 | 60篇 |
1996年 | 46篇 |
1995年 | 24篇 |
1994年 | 31篇 |
1993年 | 25篇 |
1992年 | 25篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1969年 | 4篇 |
1968年 | 4篇 |
1967年 | 7篇 |
排序方式: 共有8438条查询结果,搜索用时 93 毫秒
91.
Bart J.M. Rooijakkers Suvi Arola Rama Velagapudi Markus B. Linder 《Biochemistry and Biophysics Reports》2020
Many cellulose degrading and modifying enzymes have distinct parts called carbohydrate binding modules (CBMs). The CBMs have been shown to increase the concentration of enzymes on the insoluble substrate and thereby enhance catalytic activity. It has been suggested that CBMs also have a role in disrupting or dispersing the insoluble cellulose substrate, but dispute remains and explicit evidence of such a mechanism is lacking. We produced the isolated CBMs from two major cellulases (Cel6A and Cel7A) from Trichoderma reesei as recombinant proteins in Escherichia coli. We then studied the viscoelastic properties of native unmodified cellulose nanofibrils (CNF) in combination with the highly purified CBMs to detect possible functional effects of the CBMs on the CNF. The two CBMs showed clearly different effects on the viscoelastic properties of CNF. The difference in effects is noteworthy, yet it was not possible to conclude for example disruptive effects. We discuss here the alternative explanations for viscoelastic effects on CNF caused by CBMs, including the effect of ionic cosolutes. 相似文献
92.
93.
94.
Papenkort Stefan Böl Markus Siebert Tobias 《Biomechanics and modeling in mechanobiology》2021,20(5):2031-2044
Biomechanics and Modeling in Mechanobiology - Muscle architecture, which includes parameters like fascicle length, pennation angle, and physiological cross-sectional area, strongly influences... 相似文献
95.
Elgar Susanne Quabius Silke Tribius Alessa Heinrichs Dirk Haaser Andr Kühnel Martin Laudien Florian Hoppe Robert Mlynski Petra Ambrosch Markus Hoffmann 《Translational oncology》2021,14(2)
Previous studies describe a correlation between HPV-positivity and non-smoking in TSCC; p16INK4A-expression as surrogate-marker for HPV-DNA/RNA-positivity is discussed controversially. In the present study, these parameters are assessed prospectively. HPV-status of sputum and tonsillar-swabs was analyzed to determine their validity as surrogate-marker for tissue-HPV-status.TSCC- (n = 52) and non-neoplastic tonsillar tissue (n = 163) were analyzed. HPV-DNA- and HPV-RNA-status of total sputum, cellular fraction and supernatants, tonsillar-swabs and -tissue was determined by (RT)-PCR. Immunohistochemistry determined p16INK4A-expression.23/163 (14.2%) non-neoplastic tonsils were HPV-DNA-positive; five patients (3 HPV16, 2 HPV11) had active HPV-infections (HPV-RNA-positive), in all biomaterials. 140/163 (85.9%) patients were either HPV-DNA-positive or HPV-DNA-negative in all samples. 21/52 (40.4%) TSCC-tonsils were HPV-DNA-positive; 17 patients were HPV-RNA-positive (14 HPV16; 4 HPV18). 40/52 (76.9%) TSCC-patients were congruent in all biomaterials. p16INK4A-expression alone would have misclassified the HPV-status of 14/52 (26.2%) TSCC-patients.This prospective study confirms the discrepancy between HPV-status and p16INK4A-expression and the significant correlation between non-smoking and HPV-DNA-positivity. HPV-sputum- and/or swab-results do not consistently match tissue-results, possibly having (detrimental) consequences if those were used to assess tissue-HPV-status. In the 5 patients with active HPV infection in the non-neoplasitic tonsils, tonsillectomy likely prevented subsequent development of TSCC. 相似文献
96.
Tanja B. Grammer Wilfried Renner Michael M. Hoffmann Markus Kleber Brigitte M. Winkelhofer-Roob Bernhard O. Boehm 《Free radical research》2013,47(7):677-684
This study examined the superoxide dismutase 3 (SOD3) R231G polymorphism in relation to the severity of coronary artery disease (CAD) and the risk of myocardial infarction (MI) in 3211 individuals; 94.4% of study participants were homozygous for SOD3 231RR and 5.5% were heterozygous for SOD3 231RG. The odds ratios of the RG and GG genotype (adjusted for age, gender and for conventional cardiovascular risk factors) were 2.02 (95% CI, 1.23–3.33, p=0.005) for the highest vs the lowest Friesinger coronary score and 1.40 (95% CI, 1.02–1.92, p=0.037) for MI, respectively. Further the SOD3 RG and GG genotype was associated with lower alpha-tocopherol levels than the wild type SOD3 RR genotype. It is concluded that the SOD3 231RG and GG genotype is associated with lower alpha-tocopherol levels and the severity of CAD and the risk of MI. 相似文献
97.
Gerhard Müller Markus Albers Gerhard He?ler? Thomas E. Lehmann Hiromi Okigami Masaomi Tajimi 《Journal of enzyme inhibition and medicinal chemistry》2013,28(4):309-312
Terephthalic acid based derivatives containing β- and γ-amino acid residues were prepared as antagonists of the leukocyte cell adhesion process that is mediated through the interaction of the very late antigen 4 (VLA-4) and the vascular cell adhesion molecule 1 (VCAM-1). The compounds 2, 10–12, 14, and 16–17 inhibited the adhesion in a cell based assay in the low and sub micromolar range. 相似文献
98.
Markus W. Gerrnann James M. Aramini Bernd W. Kalisch Richard T. Pon Johan H. van de Sande 《Nucleosides, nucleotides & nucleic acids》2013,32(7-9):1481-1485
Abstract Oligodeoxynucleotides that possess alpha anomeric nucleotides and polarity reversals show promise for application in the area of antisense therapy. Here we provide a survey of the spectroscopic, thermodynamic, and enzymatic techniques used in our laboratories to investigate model systems containing such unnatural features with the ultimate goal of designing a new class of more potent and effective antisense therapeutics. 相似文献
99.
Abstract The detailed mechanisms of pH-independent cleavage and isomerization reactions of the phosphodiester bond are evaluated by examining kinetics of hydrolytic reactions of selected mono- and dialkyl esters of 3′-uridylic acid. The mechanistic choices are made by comparing LFER's between reaction rates and acidity of the alkyl group of phosphodi- and triesters. 相似文献
100.