全文获取类型
收费全文 | 3347篇 |
免费 | 170篇 |
出版年
2023年 | 37篇 |
2022年 | 21篇 |
2021年 | 47篇 |
2020年 | 38篇 |
2019年 | 55篇 |
2018年 | 93篇 |
2017年 | 77篇 |
2016年 | 108篇 |
2015年 | 108篇 |
2014年 | 139篇 |
2013年 | 210篇 |
2012年 | 224篇 |
2011年 | 189篇 |
2010年 | 122篇 |
2009年 | 118篇 |
2008年 | 150篇 |
2007年 | 153篇 |
2006年 | 167篇 |
2005年 | 130篇 |
2004年 | 134篇 |
2003年 | 154篇 |
2002年 | 142篇 |
2001年 | 74篇 |
2000年 | 79篇 |
1999年 | 44篇 |
1998年 | 26篇 |
1997年 | 19篇 |
1996年 | 21篇 |
1995年 | 19篇 |
1994年 | 22篇 |
1993年 | 18篇 |
1992年 | 33篇 |
1991年 | 26篇 |
1990年 | 22篇 |
1989年 | 28篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 21篇 |
1985年 | 31篇 |
1984年 | 22篇 |
1983年 | 38篇 |
1982年 | 17篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1974年 | 18篇 |
1973年 | 20篇 |
1972年 | 21篇 |
1970年 | 15篇 |
1969年 | 16篇 |
1967年 | 15篇 |
排序方式: 共有3517条查询结果,搜索用时 31 毫秒
1.
Fazile Nur Ekinci Akdemir Berna Karagöz Recep Soslu Saleh H. Alwasel 《Journal of enzyme inhibition and medicinal chemistry》2016,31(6):114-118
AbstractThe antioxidant effects of ellagic acid (EA) and hesperidin (HES) against skeletal muscle ischemia/reperfusion injury (I/R) were performed. Hindlimb ischemia has been induced by tourniquet occlusion for 2?h on left hindlimb. At the end of ischemia, the tourniquate has been removed and initiated reperfusion for 2?h. EA (100?mg/kg) has been applied orally before ischemia/reperfusion in the EA?+?I/R group. HES (100?mg/kg) has been given orally in the HES?+?I/R group. The left gastrocnemius muscle has been harvested and stored immediately at??80?°C until assessed for the levels of MDA and antioxidant enzymes activities. MDA level has statistically increased in I/R group (p?<?0.05) compared to other groups. The muscle tissue antioxidant enzymes activities were lower than the other groups in the I/R group (p?<?0.05). EA and HES treatments significantly reversed the damage level in I/R, also activity of tissue SOD increased in the EA?+?I/R and HES?+?I/R groups. 相似文献
2.
3.
Anna Nilsson Thomas E. Fehniger Lena Gustavsson Malin Andersson Kerstin Kenne Gy?rgy Marko-Varga Per E. Andrén 《PloS one》2010,5(7)
Readouts that define the physiological distributions of drugs in tissues are an unmet challenge and at best imprecise, but are needed in order to understand both the pharmacokinetic and pharmacodynamic properties associated with efficacy. Here we demonstrate that it is feasible to follow the in vivo transport of unlabeled drugs within specific organ and tissue compartments on a platform that applies MALDI imaging mass spectrometry to tissue sections characterized with high definition histology. We have tracked and quantified the distribution of an inhaled reference compound, tiotropium, within the lungs of dosed rats, using systematic point by point MS and MS/MS sampling at 200 µm intervals. By comparing drug ion distribution patterns in adjacent tissue sections, we observed that within 15 min following exposure, tiotropium parent MS ions (mass-to-charge; m/z 392.1) and fragmented daughter MS/MS ions (m/z 170.1 and 152.1) were dispersed in a concentration gradient (80 fmol-5 pmol) away from the central airways into the lung parenchyma and pleura. These drug levels agreed well with amounts detected in lung compartments by chemical extraction. Moreover, the simultaneous global definition of molecular ion signatures localized within 2-D tissue space provides accurate assignment of ion identities within histological landmarks, providing context to dynamic biological processes occurring at sites of drug presence. Our results highlight an important emerging technology allowing specific high resolution identification of unlabeled drugs at sites of in vivo uptake and retention. 相似文献
4.
A new significantly improved method for purification of pregnancy zone protein (PZP), α2-macroglobulin (α2M), and the C-terminal PZP receptor binding domain is presented. Several steps in an earlier procedure have been deleted, and modifications in the gradients in the DEAE step leave most of the contaminants bound to a DEAE-Sephacel gel. This procedure makes possible the rapid, simultaneous purification of both of these closely related unstable proteins in native form from human plasma, with no thiolester cleavage or formation of tetrameric PZP. The final preparations of both α2M and PZP are pure as determined by nonreducing and reducing polyacrylamide gel electrophoresis following silver staining and no cross-contamination can be observed. The yield has been significantly improved and typically more than 500 mg PZP can be obtained from 1 liter pregnancy plasma. Furthermore, the stability of PZP at different temperatures on storage was studied. In liquid nitrogen PZP can be maintained in native dimeric form with intact thiolester for many years. The storage of native PZP with intact functional properties during and after purification is an obligatory prerequisite to elucidate the biological role of PZP. The receptor binding domain of PZP can be cleaved from the PZP–methylamine complex by papain and isolated from the other peptides by S-200 gel filtration. The cleavage site was determined and the C-terminal fragment was identified with several site-specific monoclonal antibodies against PZP. 相似文献
5.
6.
7.
Barna Györffy 《Planta》1941,32(1):15-37
Zusammenfassung In der Mehrzahl der untersuchten Fälle (insgesamt über 1000 Einzelmessungen) wurden die osmotischen Werte der Tetraploiden niedriger gefunden als die der Diploiden, doch sind die Unterschiede im allgemeinen gering. Junge Pflanzen hatten immer niedrigere 4n-Werte; bei alten Pflanzen und bei Pflanzen unter extremen Kulturbedingungen waren aber vielfach die Werte der 4n höher. Es wird die Hypothese aufgestellt, daß niedrigere osmotische Werte der Tetraploiden den Normalzustand darstellen, daß aber die Polyploiden wie in anderen Eigenschaften, so auch in ihrer Osmotik variabler sind und unter dem Einfluß von Außen-bedingungen ihre osmotischen Werte stärker modifizieren.Unter physiologischen Zwangsbedingungen (Trockenkultur, Pfropfungen) wurde an den Tetraploiden eine unter den gegebenen Verhältnissen zweckmäßige Erhöhung ihrer osmotischen Werte über das Niveau der 2n beobachtet. Gegen Trockenklima erwiesen sich die untersuchten Tetraploiden im Vergleich mit den Diploiden resistenter.Irgendwelche artspezifischen Eigentümlichkeiten konnten im Rahmen der untersuchten Pflanzen nicht festgestellt werden.Mit 6 Textabbildungen. 相似文献
8.
J.J. Virgen-Ortíz V. Ibarra-Junquera P. Escalante-Minakata J.A. Osuna-Castro J. de J. Ornelas-Paz N.A. Mancilla-Margalli R.L. Castañeda-Aguilar 《Analytical biochemistry》2013
This work presents a rapid and simple freeze centrifugation method to concentrate dilute protein solutions for detection by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) Coomassie blue staining. Moreover, a simple way to assemble a cryoconcentration device is presented, and its use is discussed. Commercial purified protein standard and an enzyme with high fructosyltransferase (FTase) activity, coming from target fractions obtained by chromatographic separation, were used as an example. FTase, coming directly from the chromatographic fractions, was difficult to view through SDS–PAGE analysis; however, it was easily visualized, and its activity was enhanced, after the application of the freeze centrifugation protocol presented here. 相似文献
9.
10.
P. Usobiaga J. J. Calvete J. L. Saíz M. T. Eirín J. González-Rodríguez 《European biophysics journal : EBJ》1987,14(4):211-218
Sedimentation equilibrium and low-angle laser-light scattering were used to determine the molar mass of the glycoprotein moieties in the complexes of sodium dodecyl sulphate with the human platelet membrane glycoproteins IIb (GPIIb), IIIa (GPIIIa), and the (GPIIb) and (GPIIb) subunits of GPIIb. The values obtained by both procedures, except those for GPIIb, agree within experimental error with those calculated from their chemical composition: GPIIb (114,000 g mol-1), GPIIb (22,200 g mol-1), and GPIIIa (91,500 g mol-1). The molar mass of GPIIb determined by light scattering (142,000 g mol-1) and sedimentation equilibrium at different solvent densities (134,000 g mol-1) also agree, within experimental error, with the values calculated either from its chemical composition (136,500 g mol-1) or from the sum of the molar masses of its subunits. However the molar mass determined by sedimentation equilibrium at constant solvent density, is consistently underestimated (116,000 g mol-1).High-performance size-exclusion chromatography in sodium dodecyl sulphate solutions overestimates the molar mass of these glycoproteins and their Stokes radii, and therefore the maximal frictional ratios derived from them.Abbreviations GPIIb
glycoprotein IIb
- GPIIIa
glycoprotein IIIa
- GPIIb and GPIIb
and subunits of GPIIb, respectively
- CM-GPIIb
CM-GPIIb, and CM-GPIIIa, totally reduced and carboxymethylated forms of GPIIb, GPIIb, and GPIIIa, respectively
- SDS
sodium dodecyl sulphate
- eosin-ITC
eosin-5-isothiocyanate 相似文献