全文获取类型
收费全文 | 40010篇 |
免费 | 3724篇 |
国内免费 | 16篇 |
出版年
2022年 | 258篇 |
2021年 | 597篇 |
2020年 | 354篇 |
2019年 | 478篇 |
2018年 | 562篇 |
2017年 | 511篇 |
2016年 | 825篇 |
2015年 | 1299篇 |
2014年 | 1492篇 |
2013年 | 1955篇 |
2012年 | 2354篇 |
2011年 | 2420篇 |
2010年 | 1558篇 |
2009年 | 1443篇 |
2008年 | 2136篇 |
2007年 | 2177篇 |
2006年 | 2060篇 |
2005年 | 2142篇 |
2004年 | 2000篇 |
2003年 | 1975篇 |
2002年 | 1908篇 |
2001年 | 482篇 |
2000年 | 283篇 |
1999年 | 444篇 |
1998年 | 561篇 |
1997年 | 396篇 |
1996年 | 420篇 |
1995年 | 332篇 |
1994年 | 371篇 |
1993年 | 350篇 |
1992年 | 332篇 |
1991年 | 305篇 |
1990年 | 291篇 |
1989年 | 257篇 |
1988年 | 285篇 |
1987年 | 271篇 |
1986年 | 239篇 |
1985年 | 339篇 |
1984年 | 415篇 |
1983年 | 337篇 |
1982年 | 400篇 |
1981年 | 457篇 |
1980年 | 443篇 |
1979年 | 270篇 |
1978年 | 273篇 |
1977年 | 293篇 |
1976年 | 285篇 |
1975年 | 192篇 |
1974年 | 249篇 |
1973年 | 213篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
Hereditary spherocytosis of man. Altered binding of cytoskeletal components to the erythrocyte membrane 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
John S. Hill William H. Sawyer Geoffrey J. Howlett James S. Wiley 《The Biochemical journal》1982,201(2):259-266
The endogenous respiration of the rumen ciliate Dasytricha ruminantium maintained under an O2 tension of 2kPa (approximately 0.02 atm) was partially inhibited by KCN (40% inhibition) and NaN3 (58% inhibition). The organisms lack cytochromes, and sensitivity of respiration to KCN, NaN3, chloroquine and quercetin suggest that the operation of flavoprotein-iron-sulphur-mediated electron transport. As in Tritrichomonas foetus, hydrogenosomal respiration can be stimulated by the addition of CoA in the presence of 0.025% Triton X-100; stimulation by ADP was not detected. Stimulation of pyruvate-supported O2 uptake by Pi suggests that acetate is produced via acetyl phosphate. 相似文献
992.
993.
Bruce A. Macheri William M. F. Lee Mary Alice Westrick 《Molecular and cellular biochemistry》1982,47(2):81-95
Summary We have reviewed the studies on neutral glycosphingolipids and gangliosides of normal and leukemia human leukocytes. In this review, we examine (a) the glycosphingolipid composition of various leukocyte populations, (b) the differences in glycosphingolipids found among subsets of these cells, (c) the possible use of these compounds as markers of differentiation, and (d) the changes in glycosphingolipid composition that occur with leukemogenesis. 相似文献
994.
The amino acid sequence of the subunit of equine chorionic gonadotropin (eCG, also pregnant mare serum gonadotropin, PMSG) has been determined. Overlapping peptides from tryptic and chymotrypic digests were isolated by a two-dimensional peptide mapping technique and sequenced by the Edman procedure. The proposed amino acid sequence of eCG is: (**Denotes carbohydrate attachment points.) This sequence differs significantly from that proposed by Rathnamet al. (1978) for equine follitropin subunit; in particular, their sequence lacked the first fourteen residues.For the subunit we have placed in sequence 104 amino acid residues by direct sequence determination and peptide overlap procedures; in addition, 37 residues have been placed provisionally by homology with the human chorionic gonadotropin (hCG) sequence and composition and/or sequence data for the peptides isolated in the present studies. Difficulties in the procurement of the hormone have stalled completion of the -subunit amino acid sequence determination. The data now available indicate that eCG -subunit is highly homologous to hCG subunit and the subunits of luteinizing hormone from the pituitary gland of the several species so far described. The proposed partial sequence of eCG is: 相似文献
995.
Cellular localization of thiol-proteinase inhibitor in the epidermis of the newborn rat 总被引:4,自引:0,他引:4
Dr. Kimie Fukuyama Osamu Ohtani Toshihiko Hibino William L. Epstein 《Cell and tissue research》1982,222(2):313-323
Summary In cichlid, poecilid and centrarchid fishes luteinizing hormone releasing hormone (LHRH)-immunoreactive neurons are found in a cell group (nucleus olfactoretinalis) located at the transition between the ventral telencephalon and olfactory bulb. Processes of these neurons project to the contralateral retina, traveling along the border between the internal plexiform and internal nuclear layer, and probably terminating on amacrine or bipolar cells. Horseradish peroxidase (HRP) injected into the eye or optic nerve is transported retrogradely in the optic nerve to the contralateral nucleus olfactoretinalis where neuronal perikarya are labeled. Labeled processes leave this nucleus in a rostral direction and terminate in the olfactory bulb. The nucleus olfactoretinalis is present only in fishes, such as cichlids, poecilids and centrarchids, in which the olfactory bulbs border directly the telencephalic hemispheres. In cyprinid, silurid and notopterid fishes, in which the olfactory bulbs lie beneath the olfactory epithelium and are connected to the telencephalon via olfactory stalks, the nucleus olfactoretinalis or a comparable arrangement of LHRH-immunoreactive neurons is lacking. After retrograde transport of HRP in the optic nerve of these fishes no labeling of neurons in the telencephalon occurred. It is proposed that the nucleus olfactoretinalis anatomically and functionally interconnects and integrates parts of the olfactory and optic systems. 相似文献
996.
Kirsten M. Madsen C. William Applegate Dr. C. Craig Tisher 《Cell and tissue research》1982,226(2):363-374
Summary Morphological examination of kidney biopsies from patients with glomerulonephritis and hematuria has revealed the presence of erythrocytes within epithelial cells of the proximal tubule. This observation suggested that the proximal tubule might be capable of phagocytizing morphologically intact erythrocytes. To examine this possibility small quantities of heparinized autologous blood were injected into surface convolutions of proximal tubules of the rat kidney using standard micropuncture techniques. At time intervals ranging from 10 min to 120 h after injection, the kidneys were preserved for light and transmission electron microscopy by drip-fixation with a half-strength Karnovsky's glutaraldehyde-formaldehyde fixative.During the initial 6 h there was a flattening of the brush border and accumulation of electron-dense material representing hemoglobin in apical vacuoles and in lysosome-like structures. From 6 to 15 h after micropuncture, there was progressive loss of the brush border and the simultaneous formation of pseudopodia-like evaginations that extended from the apical plasma membrane and surrounded the individual erythrocytes. By 18 and 24 h, erythrocytes were observed in the proximal tubule cells. At later time intervals, edema, lymphocytic infiltration, and fibrosis were observed in the interstitium. In addition, crystalline structures were present in the lumen and the cells of both proximal and distal tubules. These findings suggest that in addition to their well-established ability to pinocytize hemoglobin and other proteins, the cells of the proximal tubule are capable of phagocytizing morphologically intact autologous erythrocytes. It is possible that phagocytosis by the proximal tubule cells may play a role in the disposal of erythrocytes from the tubular fluid in hematuric conditions. 相似文献
997.
A ninhydrin-positive, phosphorus-negative lipid from Paracoccus denitrificans ATCC 13543 has been isolated and purified by mild alkaline methanolysis followed by silicic acid column chromatography and preparative thin-layer chromatography. The lipid was identified as an ornithine-containing lipid. The major ester-linked fatty acid was cis vaccenic acid. Major amide-linked fatty acids were 3-OH-20:1 and 3-OH-18:0. Ornithine-containing lipid was a major lipid component of P. denitrificans. Phospholipids made up about 57% and ornithine-containing lipid about 14% of the weight of the total lipid of the organism. The ratios of lipid ornithine: lipid phosphorus were 0.23, 0.65 and 0.58 in cytoplasmic membrane, outer membrane, and an NaCl extract, which is thought to represent chiefly outer membrane, respectively. Thus ornithine-containing lipid appears to be present in larger amounts in outer membrane than cytoplasmic membrane. No substantial variations in lipid ornithine levels were noted in stationary phase versus exposnential phase organisms, organisms grown in complex medium versus organisms grown in minimal medium with and without amino acid supplements, or in organisms grown in low phosphate-containing medium.Non standard abbreviations TLC
thin-layer chromatography
- Tris-HCl
tris(hydroxymethyl)aminomethane hydrochloride
- TMS
trimethylsilyl
- TFA
triluoroacetyl
- NPPN
ninhydrin-positive, phosphorus-negative
- ECL
equivalent chain length 相似文献
998.
Twelve strains ofLegionella pneumophila were tested for the presence of plasmid DNA. Three strains, belonging to serogroup 1, had large plasmids of 83.8×106 daltons, as determined by electron microscopy. A fourth strain, also from serogroup 1, had a similar large plasmid in addition to a smaller plasmid. Restriction analysis of plasmid DNA isolated from the strains with a single size plasmid indicated that the plasmids were structurally very similar. The biologic functions of these plasmids are yet to be determined. 相似文献
999.
R. Rodney Howell Amir I. Arbisser David S. Parsons Charles I. Scott Ursula Fraustadt William R. Collie Robert N. Marshall Oscar Cavazos Ibarra 《American journal of human genetics》1981,33(6):957-967
We have defined a new autosomal recessive disorder in patients stemming from a small community in northern Mexico. Diagnosable at birth, its major symptoms include brittle hair, mental retardation, and nail dysplasia. Structural hair abnormalities are seen by both light and electron microscopy. Hair cystine content is reduced while the copper/zinc ratio in hair is increased. 相似文献
1000.
There is still disagreement concerning the functional significance of split-line patterns in bone. This study was undertaken to reexamine the mechanical forces hypothesis for split-line formation by comparing split-line patterns with in vivo mandibular bone strain patterns. The relationship between split-line orientation and in vivo stress and strain patterns on macaque and galago mandibles was examined during jaw opening and the power stroke of mastication and incision. An attempt was made to relate split-line orientation to the direction of tensile stress and strain along the primate mandible. In addition, we also investigated the alternative possibility that split-line orientation is related to the direction of low stresses (and strains) on the primate mandible. The results of this study showed that there was no consistent relationship between split-line orientation and the principal strains or stresses. Thus, split-lines did not run consistently in the direction of high or low stress and strain. Therefore, we have concluded that split-line orientation provides little useful information for inferring patterns of stress and strain in bone. 相似文献