全文获取类型
收费全文 | 1853篇 |
免费 | 187篇 |
国内免费 | 1篇 |
出版年
2022年 | 21篇 |
2021年 | 34篇 |
2020年 | 16篇 |
2018年 | 24篇 |
2017年 | 28篇 |
2016年 | 43篇 |
2015年 | 75篇 |
2014年 | 51篇 |
2013年 | 63篇 |
2012年 | 80篇 |
2011年 | 104篇 |
2010年 | 54篇 |
2009年 | 58篇 |
2008年 | 83篇 |
2007年 | 68篇 |
2006年 | 63篇 |
2005年 | 54篇 |
2004年 | 56篇 |
2003年 | 56篇 |
2002年 | 53篇 |
2001年 | 44篇 |
2000年 | 37篇 |
1999年 | 23篇 |
1998年 | 28篇 |
1993年 | 23篇 |
1992年 | 32篇 |
1991年 | 45篇 |
1990年 | 35篇 |
1989年 | 45篇 |
1988年 | 21篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 28篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1979年 | 28篇 |
1978年 | 33篇 |
1977年 | 23篇 |
1976年 | 27篇 |
1975年 | 16篇 |
1974年 | 17篇 |
1973年 | 21篇 |
1972年 | 21篇 |
1971年 | 25篇 |
1968年 | 19篇 |
1967年 | 16篇 |
1966年 | 23篇 |
排序方式: 共有2041条查询结果,搜索用时 15 毫秒
71.
M Schiffer F A Westholm N Panagiotopoulos A Solomon 《Journal of molecular biology》1978,124(1):287-290
A complete human κ-type Bence—Jones protein (Fin) has been isolated and crystallized. Immunochemical and physicochemical characterization of protein Fin indicates that it is of the κ-chain subgroup, κII, and that it consists of two non-covalently bound intact monomers having a molecular weight of ~23,000 Crystals of Bence—Jones protein Fin obtained from ammonium sulfate solutions have the orthorhombic space group P212121 with cell dimensions . The asymmetric unit consists of a dimer of molecular weight ~46,000. 相似文献
72.
A mixture of 3H-15alpha-hydroxyandrostenedione and 14C-15alpha-hydroxydehydroisoandrosterone was injected intravenously into two subjects in the third trimester of pregnancy and, in a second study, directly into two fetuses in utero during transfusion for erythroblastosis fetalis. The urine was collected for 4-5 days and steroid conjugates in the urine were hydrolyzed into sulfate and glucosiduronate fractions. From the glucosiduronate fraction 15alpha-hydroxyestriol, 15alpha-hydroxyestradiol, 15alpha-hydroxyandrostenedione and 15alpha-hydroxydehydroisoandrosterone were isolated. No metabolites were identified in the sulfate fraction of the urine. A marked difference was observed in the metabolism of 15alpha-hydroxyandrostenedione and 15alpha-hydroxydehydroisoandrosterone which is dependent on the route of administration of the substrates. Both substrates were converted to 15alpha-hydroxyestriol and 15alpha-hydroxyestradiol, and the 3H/14C ratios and percentage conversions suggest that 15alpha-hydroxyandrostenedione seems to be a better precursor of the urinary 15alpha-hydroxylated estrogens than 15alpha-hydroxydehydroisoandrosterone. The 3H/14C ratios also suggest that 15alpha-hydroxydehydroisoandrosterone was converted to 15alpha-hydroxyestriol via 15alpha-hydroxyandrostenedione, and that the formation of 15alpha-hydroxyestradiol from 15alpha-hydroxydehydroisoandrosterone via 15alpha-hydroxyandrostenedione is a pathway of minor importance. Finally, 15alpha-hydroxydehydroisoandrosterone was recovered from the urine only when the precursors were injected into the maternal circulation. Also, an unknown metabolite containing only 14C was detected in the glucosiduronate fraction of the urine of each subject. 相似文献
73.
The properties of 3H-catecholamine binding to α- and β-adrenergic receptors in CNS are reviewed. 3H-epinephrine and 3H-norepinephrine label one class of α-receptors throughout the brain, with high affinities for agonists and some antagonists. Agonist affinities at this site are increased in low temperature conditions but are reduced by guanine nucleotides and monovalent cations. Divalent cations reverse both effects. This α-receptor may be coupled to adenylate cyclase by GTP and/or sodium, and uncoupled by divalent cations. 3H-epinephrine labels β2, but not β1, receptors in CNS, especially in bovine cerebellum. The same β-receptor does not show agonist-specific GTP-sensitivity, but does exhibit Na+-sensitivity. This receptor appears to be linked to adenylate cyclase, and sodium rather than GTP may be the coupling agent. 相似文献
74.
This paper describes the derivation and use of predictive retention coefficients for the reversed-phase high-performance liquid chromatography of peptides. The use of predicted elution positions in the isolation of peptides is illustrated by two examples where peptides, whose existence was postulated from cDNA sequence data, have been successfully isolated. The combination of the powerful chromatographic technology and the ability to predict the elution positions of peptides based on their composition provides a very potent method for the isolation of peptides from biological tissues. 相似文献
75.
This work is concerned with statistical methods to estimate yield and maintenance parameters associated with microbial growth. For a given dilution rate, an experimenter typically measures substrate concentration, oxygen utilization rate, the rate of carbon dioxide evolution, and biomass concentration. These correlated response variables each contain information about the maintenance and yield parameters of interest. A maximum likelihood estimator which combines this correlated information for the yield and maintenance parameters is proposed, evaluated, and tested on literature data. Both point and interval estimators are considered. 相似文献
76.
The isolation and identification of multiple forms of the neutrophil granule peptides from human leukemic cells 总被引:4,自引:0,他引:4
A Bateman A Singh C Shustik W M Mars S Solomon 《The Journal of biological chemistry》1991,266(12):7524-7530
HP-1 is a 30-residue cysteine- and arginine-rich peptide of the human neutrophil primary granule and is the most abundant human representative of the family of peptides variously called defensins and corticostatins. Peptides belonging to this family have many biological activities including the non-oxidative destruction of ingested microorganisms, the inhibition of adrenocorticotropin-stimulated synthesis of glucocorticoids, monocyte chemotaxis, the non-cytolytic inhibition of [3H]thymidine incorporation in HL-60 promyelocyte-like cells and the stimulation of nifedipine-sensitive calcium channels. Using a combination of reversed-phase and size-exclusion high performance liquid chromatography and an HP-1 radio-immunoassay, three immunoreactive peptides were detected and isolated from the promyelocyte-like cell line, HL-60, and from leukocytes of patients with chronic myelogenous and chronic lymphocytic leukemias. One of these peptides was HP-1 itself. A second was identified by gas-phase Edman microsequencing as an amino-terminally extended fragment of the HP-1 precursor which we call HP1-56. The third is likely to arise from enzymatic cleavage of the precursor at a dibasic site. Of the leukemic cells the greatest amount of HP1-56 relative to HP-1 was found in cells from a patient in myeloblastic crisis but overall the richest source of HP1-56 relative to HP-1 was found to be in fetal lung tissue. HP1-56 is difficult to detect in normal peripheral neutrophils and its presence in cells that are actively biosynthesizing primary granule components such as HL-60 may make it useful for studying the biosynthesis of granule polypeptides, their ontogeny, and possibly as a marker protein for leukemic diseases. 相似文献
77.
Corticostatic peptides. 总被引:2,自引:0,他引:2
S Solomon J Hu Q Zhu D Belcourt H P Bennett A Bateman T Antakly 《The Journal of steroid biochemistry and molecular biology》1991,40(1-3):391-398
In the last four years corticostatic (anti-ACTH) peptides have been isolated from human, rabbit, guinea pig and rat tissues. These peptides do not act via the cAMP cell signalling system but rather via the inhibition of the binding of ACTH to its receptor most probably through direct competition with the 14-18 sequence of ACTH for receptor binding. ACTH has specific high affinity receptors on adrenal cells but rabbit corticostatin I (CSI) has high capacity, low affinity receptors which are competed for by unlabelled excess CSI but not by excess ACTH. This indicates the presence of specific CSI adrenal cell receptors. The rabbit pituitary, hypothalamus, thalamus, adrenals, lungs and placenta contain sizeable amounts of immunoassayable CSI. Immunochemical localization of CSI indicates that it is present in the large macrophages and in neutrophils in rabbit lung, in macrophages and "supporting" endothelial cells in the spleen and in the adrenals in the cells of the zona reticularis. We have also isolated and identified new peptides which contain 12 cysteines from immune cells of humans, rats and a teleost, the carp. The functions of these peptides are now being determined. This large family of peptides may have many other, yet unidentified functions but at present we can only describe a small number of these. 相似文献
78.
Bruce L. Wilson Glenn L. Albright Ph.D. Solomon S. Steiner John L. Andreassi 《Applied psychophysiology and biofeedback》1991,16(1):45-53
In the present study 36 police officers were exposed to a psychological stressor (IQ quiz) and to cold pressor stress while several cardiovascular variables were monitored. Impedance cardiography was used to provide measures of heart rate, stroke volume, cardiac output, myocardial contractility, and total peripheral resistance. In addition, measures of systolic and diastolic blood pressure and peripheral skin temperature were obtained. A multivariate analysis of variance (MANOVA) indicated that significant increases in diastolic and systolic blood pressure during the cold pressor test were mediated by large increases in total peripheral resistance, whereas blood pressure elevation during the IQ quiz were accompanied by significant increases in heart rate and, to a lesser extent, cardiac output. Peripheral skin temperature decreased in response to each stressor. Additional analysis indicated a degree of stimulus specificity for several variables. For example, diastolic blood pressure showed greater increases to cold pressor than quiz, whereas systolic blood pressure increased more with the psychological than the physical stressor. Directional fractionation occurred for both myocardial contractility and cardiac output. 相似文献
79.
We have cloned the Escherichia coli phoP gene, a member of the family of environmentally responsive two-component systems, and found its deduced amino acid sequence to be 93% identical to that of the Salmonella typhimurium homolog, which encodes a major virulence regulator necessary for intramacrophage survival and resistance to cationic peptides of phagocytic cells. The phoP gene was mapped to kilobase 1202 on the Kohara map (25-min region) of the E. coli genome (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987) and found to be transcribed in a counterclockwise direction. Both E. coli and S. typhimurium phoP mutants were more sensitive than their isogenic wild-type strains to the frog-derived antibacterial peptide magainin 2, suggesting a role for PhoP in the response to various stresses in both enteric species. 相似文献
80.
Lawrence W. Solomon 《The Yale journal of biology and medicine》1992,65(5):537-Oct;65(5):537