全文获取类型
收费全文 | 5813篇 |
免费 | 220篇 |
出版年
2023年 | 11篇 |
2022年 | 3篇 |
2021年 | 20篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2018年 | 36篇 |
2017年 | 33篇 |
2016年 | 50篇 |
2015年 | 76篇 |
2014年 | 78篇 |
2013年 | 87篇 |
2012年 | 484篇 |
2011年 | 581篇 |
2010年 | 119篇 |
2009年 | 97篇 |
2008年 | 542篇 |
2007年 | 544篇 |
2006年 | 548篇 |
2005年 | 470篇 |
2004年 | 448篇 |
2003年 | 430篇 |
2002年 | 391篇 |
2001年 | 256篇 |
2000年 | 321篇 |
1999年 | 169篇 |
1998年 | 22篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1980年 | 6篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1971年 | 7篇 |
1970年 | 9篇 |
1969年 | 5篇 |
1968年 | 8篇 |
排序方式: 共有6033条查询结果,搜索用时 265 毫秒
1.
One of the most widely used mechanisms by which the role of glutathione (GSH) in cellular functions has been withdrawn, is to deplete GSH intracellularly. The importance of the procedure and xenobiotic chosen to get it is discussed. Mitochondrial GSH plays certainly an important role in maintaining cellular homeostasis. This contribution varies depending on the tissue and the conclusions obtained about the functions of this GSH pool in one organ may not be applied to others. Original data on the subcellular distribution of GSH in myocardial tissue of the rat are presented, and the effect of phorone on both cardiac GSH pools is compared with the effect in liver. The mechanical failure of myocardium after ischemic or reperfusion damage might involve mitochondrial GSH, in view of the literature data referring to the role of thiol groups in energy transfer from mitochondria to cytosol. 相似文献
2.
Biosynthesis of chlortetracycline is localized differently under low- and high-production conditions (standard low-production strain and its high-production variant). The experimental evidence was based on the assay of anhydrotetracycline oxygenase in subcellular fractions, ultracytochemical localization and electron-probe X-ray microanalysis of the product in the mycelium. Overproduction of chlortetracycline is closely associated with compartmentation of biosynthetic enzymes and with an efficient export of the antibiotic out of the cell. 相似文献
3.
Enzyme immunoassay of oestrogen and progesterone receptors in uterine and intrauterine tissue during human pregnancy and labour 总被引:4,自引:0,他引:4
T Padayachi R J Pegoraro L Rom S M Joubert 《The Journal of steroid biochemistry and molecular biology》1990,37(4):509-511
Oestrogen and progesterone receptors were studied in the non-pregnant state, in early pregnancy and at term using monoclonal antibody enzyme immunoassays. Receptors for both steroids were found in tissues from non-pregnant patients and patients in early pregnancy. At term oestrogen receptors were undetectable in all tissues studied. Progesterone receptors were undetectable in chorion, amnion and placenta at term, while present in extremely low concentrations in decidua and myometrium. 相似文献
4.
S Natarajan E M Gordon E F Sabo J D Godfrey H N Weller J Pluscec M B Rom J Engebrecht D W Cushman J M Deforrest 《Journal of enzyme inhibition》1988,2(2):91-97
The design rationale for a new series of tripeptide derived angiotensin converting enzyme (ACE) inhibitors, which we term "ketomethylureas", is described. Analogs of tripeptide substrates (i.e. N-benzoyl-Phe-Ala-Pro) in which the nitrogen atom of the scissile amide bond and the adjacent asymmetric carbon atom of the penultimate amino acid residue are formally transposed give rise to this novel class of inhibitors. The most potent ketomethylureas inhibit ACE with I50 values in the nM range. 相似文献
5.
Uri Werner Edith Suss-Toby Ayelet Rom Baruch Minke 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(4):427-434
Summary Illumination of barnacle (Balanus amphitrite) photoreceptors is known to increase the membrane permeability to sodium and Ca2+ ions resulting in a depolarizing receptor potential. In this report, we show that lanthanum (La3+), a known inhibitor of Ca-binding proteins, reversibly eliminates the receptor potential of barnacle photoreceptors when applied to the extracellular space. Similar reversible elimination of the light response was obtained by removing extracellular Ca2+ by application of the calcium chelating agent EGTA. Iontophoretic injection of Ca2+, but not K+ into the cells protected both the transient and the steady-state phases of the receptor potential from elimination by EGTA while only the transient phase was protected in the presence of La3+. The EGTA experiments suggest that internal Ca2+ is necessary for light excitation of barnacle photoreceptors while the La3+ experiments suggest that La3+-sensitive inward current is necessary to maintain excitation during prolonged light.Abbreviations EGTA
ethylenglyol-bis-(-aminoethylether) N, N, N1, N1-tetraacetate
- BAPTA
bis-(0-aminophenoxy)-ethane-N, N, N1, N1-tetraacetic acid
- DMSO
dimethyl sulfoxide
- trp
transient receptor potential
- nss
no steady state
- ASW
artificial sea water 相似文献
6.
Twenty-one heifers were synchronized with PGF(2) alpha and 22 heifers were stimulated with FSH-P in decreasing doses and synchronized with PGF(2) alpha. The beginning of LH rise was observed to be 47.6+/-14.0 h and 35.9+/-1.3 h (P < 0.05) and the peak of LH rise was observed at 53.8 +/- 13.4 h and 40.14+/-1.4 h (P < 0.05) after the luteolyticum administration in the synchronized and superovulated group respectively. The beginning of LH rise was observed 6.9+/-6.7 h and 4.8+/-2.6 h (P < 0.05) and the LH peak was observed 11.8+/-7.7 h and 8.3+/-3.2 h (P < 0.05) after the frist symptoms of oestrus in the synchronized and superovulated group respectively. Ovulation was not observed in stimulated heifers in the period of 23-25 h after the preovulatory LH rise. Compact cumulus oophorus was seen at 30.5%, expanded at 67.0 and partial at 2.5% during this interval of 23-25h. Within this same interval 26.9%, 51.3% and 21.8% oocytes without perivitelline space, with perivitelline space and with extruded first polar body were aspirated respectively. It may be concluded from the reported results that to recover fully mature oocytes for in vitro fertilization, it will be necessary to monitor the preovulatory period of the donor cow in great detail. 相似文献
7.
Isolation of cDNA clones and complete amino acid sequence of human erythrocyte glycophorin C 总被引:7,自引:0,他引:7
Y Colin C Rahuel J London P H Roméo L d'Auriol F Galibert J P Cartron 《The Journal of biological chemistry》1986,261(1):229-233
Two cDNA clones for glycophorin C, a transmembrane glycoprotein of the human erythrocyte which carries the blood group Gerbich antigens, have been isolated from a human reticulocyte cDNA library. The clones were identified with a mixture of 32 oligonucleotide probes (14-mer) which have been synthetized according to the amino acid sequence Asp-Pro-Gly-Met-Ala present in the N-terminal tryptic peptide of the molecule. The primary structure of glycophorin C deduced from the nucleotide sequence of the 460 base-pair insert of the pGCW5 clone indicates that the complete protein is a single polypeptide chain of 128 amino acids clearly organized in three distinct domains. The N-terminal part (residues 1-57, approximately) which is N- and O-glycosylated is connected to a hydrophilic C-terminal domain (residues 82-128, approximately) containing 4 tyrosine residues by a hydrophobic stretch of nonpolar amino acids (residues 58-81, approximately) probably interacting with the membrane lipids and permitting the whole molecule to span the lipid bilayer. Northern blot analysis using a 265-base-pair restriction fragment obtained by DdeI digestion of the inserted DNA shows that the glycophorin C mRNA from human erythroblasts is approximately 1.4 kilobases long and is present in the human fetal liver and the human K562 and HEL cell lines which exhibit erythroid features. The glycophorin C mRNA, however, is absent from adult liver and lymphocytes, indicating that this protein represents a new erythrocyte-specific probe which might be useful to study erythroid differentiation. 相似文献
8.
Photobiont cells of the lichen Evernia prunastri have completely been separated from their fungal partner by filtration through a bed of Sepharose 2B. Both mannitol and ribitol have been quantified by gas-liquid chromatography in the different steps of the isolation procedure. Absence of mannitol, which is exclusively produced by the mycobiont, has been used as the best probe to monitor isolation. 相似文献
9.
Invertase immobilization via its carbohydrate moiety 总被引:1,自引:0,他引:1
After periodate oxidation of its glycosidic component, invertase was covalently bound onto three types of modified solid supports: glycidyl methacrylate, styrene-divinylbenzene copolymers, and bead cellulose. Direct reaction of the invertase aldehyde groups that were formed with amino groups of the support and use of the modified Ugi reaction have been employed as immobilization procedures. Apart from binding methods, the important effects of the buffer, support, conditions of periodate oxidation, and the length of the spacer on the activity of the enzyme conjugate have been investigated. Superior conjugate activity was obtained, via modified Ugi reaction, by the immobilization of a suitably oxidized invertase to a styrene-divinylbenzene copolymer having free amino groups. 相似文献
10.
Cloning and sequencing of mRNAs coding for two adult alpha globin chains of the salamander Pleurodeles waltlii 总被引:1,自引:0,他引:1
A cDNA library of erythrocyte mRNAs was established from immature red blood cells of the adult amphibian, Pleurodeles waltlii (urodele; salamander). The cDNA clones corresponding to the four adult globin chains were first identified and characterized by positive selection and the cDNAs derived from the two (major and minor) alpha-globin chains sequenced. The sequences presented contain both the complete 3'-noncoding region and the coding region of both chains, with the exception of the first nine codons of the minor alpha-chain, and a portion of the 5'-noncoding region of the major chain. The amino acid sequences of the encoded alpha-globin polypeptides have been deduced and compared with those of Xenopus laevis and of man. These comparative studies suggest that the alpha-globins of Pleurodeles waltlii and Xenopus laevis may have diverged from a common ancestral gene at the time when mammalian and amphibian lines diverged, and that they then evolved separately. Duplication of the alpha-gene, which is responsible for the polypeptide heterogeneity, appears to have occurred earlier in Pleurodeles waltlii than in Xenopus laevis. 相似文献