全文获取类型
收费全文 | 8039篇 |
免费 | 863篇 |
国内免费 | 1篇 |
出版年
2023年 | 36篇 |
2022年 | 85篇 |
2021年 | 220篇 |
2020年 | 126篇 |
2019年 | 169篇 |
2018年 | 189篇 |
2017年 | 176篇 |
2016年 | 243篇 |
2015年 | 373篇 |
2014年 | 377篇 |
2013年 | 481篇 |
2012年 | 566篇 |
2011年 | 578篇 |
2010年 | 338篇 |
2009年 | 316篇 |
2008年 | 408篇 |
2007年 | 435篇 |
2006年 | 508篇 |
2005年 | 356篇 |
2004年 | 302篇 |
2003年 | 280篇 |
2002年 | 256篇 |
2001年 | 163篇 |
2000年 | 124篇 |
1999年 | 100篇 |
1998年 | 78篇 |
1996年 | 54篇 |
1995年 | 43篇 |
1994年 | 40篇 |
1992年 | 82篇 |
1991年 | 85篇 |
1990年 | 80篇 |
1989年 | 100篇 |
1988年 | 77篇 |
1987年 | 75篇 |
1986年 | 55篇 |
1985年 | 62篇 |
1984年 | 57篇 |
1983年 | 44篇 |
1982年 | 39篇 |
1979年 | 54篇 |
1978年 | 45篇 |
1977年 | 37篇 |
1976年 | 36篇 |
1975年 | 49篇 |
1974年 | 46篇 |
1973年 | 43篇 |
1972年 | 39篇 |
1971年 | 42篇 |
1970年 | 41篇 |
排序方式: 共有8903条查询结果,搜索用时 31 毫秒
111.
Mühlebach S. M. Gross M. Wirz T. Wallimann T. Perriard J. -C. Wyss M. 《Molecular and cellular biochemistry》1994,133(1):245-262
Comparisons of the protein sequences and gene structures of the known creatine kinase isoenzymes and other guanidino kinases revealed high homology and were used to determine the evolutionary relationships of the various guamidino kinases. A CK framework is defined, consisting of the most conserved sequence blocks, and diagnostic boxes are identified which are characteristic for anyone creatine kinase isoenzyme (e.g. for vertebrate B-CK) and which may serve to distinguish this isoenzyme from all others (e.g. from M-CKs and Mi-CKs). Comparison of the guanidino kinases by near-UV and far-UV circular dichroism further indicates pronounced conservation of secondary structure as well as of aromatic amino acids that are involved in catalysis.Abbreviations GuaK
guanidino kinase
- CK
creatine kinase
- B-and M-CK
brain and muscle cytosolic CK isoenzyme
- Mi-CK
mitochondrial CK isoenzyme
- ArgK
arginine kinase
- Cr
creatine
- PCr
phosphorylcreatine
- PArg
phosphorylarginine 相似文献
112.
113.
Calcium uptake by microsomal membranes from the cellular slime mould Dictyostelium discoideum was measured using Calcium Green-2 as a fluorescent probe of external free Ca2+ concentration. High-affinity Ca2+ uptake was found to be completely inhibited by low concentrations of vanadate, but not by thapsigargin, suggesting that the activity is mediated by a Ca2+-ATPase distinct from sarco(endo)plasmic reticulum type of higher animal cells. On sucrose density gradients, Ca2+ uptake distributes with vacuolar proton pump activity and part of the observed Ca2+ uptake is dependent on the pH gradient generated by the vacuolar-type H+-ATPase, indicating that the Ca2+ pump is located on both acidic and non-acidic vesicles, possibly derived from the H+-ATPase-rich contractile vacuole complex. 相似文献
114.
Summary Direct measurements of membrane fluidity by fluorescence anisotropy of protoplasts fromKloeckera apiculata andSaccharomyces cerevisiae, a low and a high ethanol tolerant strain respectively, are presented. The comparison of the behaviour of the two strains
grown with or without ethanol enabled us to demonstrate the existing relationship between ethanol tolerance and membrane fluidity. 相似文献
115.
Elham A. Ghabbour Ahmed H. Khairy Donald P. Cheney Verena Gross Geoffrey Davies Thomas R. Gilbert Xinyu Zhang 《Journal of applied phycology》1994,6(5-6):459-468
A standard humic acid extraction procedure has been used to isolate dark brown organic residues from samples of the macroscopic marine brown algaPilayella littoralis. The residues are insoluble in water, but soluble at high pH, and are similar in elemental composition, ash content, UV-visible, IR, PMR and X-Ray fluorescence spectra, X-Ray diffractograms and scanning electron micrographs to residues of a humic acid isolated from municipal compost. These results indicate thatPilayella produces humic acids.Author for correspondence 相似文献
116.
Fine root growth and demographic responses to nutrient patches in four old-field plant species 总被引:10,自引:0,他引:10
Proliferation of roots in a nutrient patch can occur either as a result of an increase in root length (morphological response) or by a change in root birth or death rates (demographic responses). In this study we attempted to distinguish between these two mechanisms of response to nutrient patches and to compare the responses of four old-field plant species (two annuals, two perennials). For all four species combined, there were significant increases in root numbers and root length in fertilized patches. Root proliferation in fertilized patches was largely due to increased birth (=branching) rates of new roots. However, there was also a significant increase in root death rates in the fertilized patches which reduced the magnitude of the increase in net root numbers. Plots for individual species suggested they differed in the magnitude and timing of root proliferation in fertilized patches due to differences in root birth and death rates. However, because of the limited sample size in this study, there was only a marginally significant difference among species in root birth rates, and no difference in death rates. Further studies are currently underway to better quantify species differences in the demographic mechanism, as well as magnitude, of response to nutrient patches and if this would affect the ability to exploit small-scale heterogeneity in soil resources. 相似文献
117.
A 37-kilodalton glycoprotein from a baculovirus of Orgyia pseudotsugata is localized to cytoplasmic inclusion bodies. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The gene encoding a 37-kDa glycoprotein (gp37) of Orgyia pseudotsugata multinucleocapsid nuclear polyhedrosis virus (OpMNPV) was located and sequenced. gp37 of OpMNPV was found to have 62 and 37% amino acid sequence identity with gp37 of Autographa californica multinucleocapsid nuclear polyhedrosis virus (AcMNPV) and with a protein reported to be a component of occlusion bodies from Choristoneura biennis entomopoxvirus, respectively. The mRNA start site of the OpMNPV gp37 gene was mapped within a late promoter sequence (TTAAG). A TrpE fusion protein containing 55% of the OpMNPV gp37 gene amino acid sequence was used to generate a monospecific antiserum. Western immunoblot analysis of OpMNPV-infected Lymantria dispar cells detected gp37 beginning at 24 h postinfection. Immunoelectron microscopy indicated that the protein is concentrated in cytoplasmic inclusion bodies late in infection. In contrast to gp37 of AcMNPV which was present in the matrix of occlusion bodies, OpMNPV gp37 was not observed in this location. Neither OpMNPV nor AcMNPV gp37 was associated with the polyhedron envelope. 相似文献
118.
119.
Paul M. Gross Madan G. Joneja Judy J. Pang Trevor M. Polischuk Steven W. Shaver Dan S. Wainman 《Cell and tissue research》1993,272(1):79-88
We applied scanning electron microscopy combined with imaging and morphometric techniques to analyze the dorsal topography and morphology of short portal vessels linking the capillary beds of the pituitary neural and anterior lobes in adult male albino rats. The pituitary microvasculature was replicated by intracarotid injection of Batson's No. 17 compound producing plastic casts that were advantageous for comprehensive morphometric analyses using an imaging device. The analysis revealed the existence of two types of portal vessels having quantitatively different morphological properties. The bilateral venular plexus of 3–4 vessels located at the base of the infundibular stalk (each venule measuring 300 m in length and 32 m in diameter) appears to be the major part of the short portal system in the dorsum of the rat pituitary gland. Narrower capillary-like shunt vessels (6.8 m in diameter), of about the same length as the venules, were situated throughout other subregions of the intermediate lobe cleft. The short portal vessels of both types made direct anastomoses with the capillary networks in the neural and anterior lobes. The neural lobe capillaries were twice as numerous (1324 per mm2), and only half as wide (6.2 m), as the sinusoidal capillaries in the anterior lobe (density of 637 per mm2; diameter of 13.7 m). The topographical position of the portal venular system suggests that the caudolateral subregions of the pituitary neural and anterior lobes have a functional relationship dependent on rapid interlobe transfer of neurohumoral factors such as hormones via the portal blood. This process appears to be supplemented throughout the rest of the cleft between the two lobes by a small number of capillary shunts that supply the epithelial cell lobules of the intermediate lobe in situ. The findings collectively indicate that this portal system provides a constant stream of neurohumoral information that is shared moment-by-moment between the pituitary neural and anterior lobes. 相似文献
120.