全文获取类型
收费全文 | 822篇 |
免费 | 113篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 12篇 |
2018年 | 6篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 26篇 |
2014年 | 23篇 |
2013年 | 42篇 |
2012年 | 52篇 |
2011年 | 45篇 |
2010年 | 29篇 |
2009年 | 23篇 |
2008年 | 39篇 |
2007年 | 37篇 |
2006年 | 40篇 |
2005年 | 36篇 |
2004年 | 42篇 |
2003年 | 40篇 |
2002年 | 35篇 |
2001年 | 31篇 |
2000年 | 28篇 |
1999年 | 29篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1970年 | 4篇 |
排序方式: 共有935条查询结果,搜索用时 15 毫秒
1.
2.
3.
Acyl-CoA-binding protein from cow. Binding characteristics and cellular and tissue distribution. 总被引:7,自引:3,他引:4
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)
Hydroxyl radicals (OH.) in free solution react with scavengers at rates predictable from their known second-order rate constants. However, when OH. radicals are produced in biological systems by metal-ion-dependent Fenton-type reactions scavengers do not always appear to conform to these established rate constants. The detector molecules deoxyribose and benzoate were used to study damage by OH. involving a hydrogen-abstraction reaction and an aromatic hydroxylation. In the presence of EDTA the rate constant for the reaction of scavengers with OH. was generally higher than in the absence of EDTA. This radiomimetic effect of EDTA can be explained by the removal of iron from the detector molecule, where it brings about a site-specific reaction, by EDTA allowing more OH. radicals to escape into free solution to react with added scavengers. The deoxyribose assay, although chemically complex, in the presence of EDTA appears to give a simple and cheap method of obtaining rate constants for OH. reactions that compare well with those obtained by using pulse radiolysis. 相似文献
4.
The use of databanks in genetic research assumes reliability of the information they contain. Currently, error-detection in the manually or electronically entered data contained in the nucleotide sequence databanks at EMBL, Heidelberg and GenBank at Los Alamos is limited. We have used a subset of sequences from these databanks to train neural networks to recognize pre-mRNA splicing signals in human genes. During the training on 33 human genes from the EMBL databank seven genes appeared to disturb the learning process. Subsequent investigation revealed discrepancies from the original published papers, for three genes. In four genes, we found wrongly assigned splicing frames of introns. We believe this to be a reflection of the fact that splicing frames cannot always be unambiguously assigned on the basis of experimental data. Thus incorrect assignment appear both due to mere typographical misprints as well as erroneous interpretation of experiments. Training on 241 human sequences from GenBank revealed nine new errors. We propose that such errors could be detected by computer algorithms designed to check the consistency of data prior to their incorporation in databanks. 相似文献
5.
The eastern Caribbean island of Saint Lucia is now famous in parasitological history as the setting for a major programme of schistosomiasis control'. Perhaps less well-known are the island's effective control of many intestinal parasites, and elimination of malaria, such that the current patterns of mortality and other demographic indicators now resemble those of industrialized countries. More recently, the island has become the focus for another community-based health programme as the Caribbean region again comes to grips with Aedes aegypti and its recently imported relative, Aedes albopictus, important vectors of yellow fever and dengue viruses (see Box 1). 相似文献
6.
Matrix plasminogen activator inhibitor. Modulation of the extracellular proteolytic environment 总被引:7,自引:0,他引:7
We have previously demonstrated that plasminogen activator inhibitor (PAI-1) is associated with the extracellular matrix of cultured bovine smooth muscle cells (Knudsen, B.S., Harpel, P.C., Nachman, R.L. (1987) J. Clin. Invest. 80, 1082-1089). In this report we describe the physiologic role of PAI-1 during the interaction of the tissue plasminogen activator (t-PA) secreting Bowes human melanoma cell line with endothelial extracellular matrices. In addition we have characterized the t-PA.PAI complexes formed during this interaction in the presence and absence of plasminogen. In the absence of plasminogen, a 104-kDa complex between Bowes t-PA and PAI-1 appears in the supernatant. In the presence of plasminogen, PAI initially prevents plasmin formation on the matrix and protects the matrix from degradation by plasmin. The 104-kDa t-PA.PAI complex is degraded into a 68 and a 47-kDa complex by small amounts of plasmin generated from secreted Bowes t-PA and plasminogen. Analysis of these complexes revealed that t-PA is rapidly cleaved by plasmin within the complex whereas complexed PAI-1 is not further degraded. Matrix-associated PAI-1 may play an important role in the protection of extracellular matrices from remodeling and degradation by cellular t-PA and plasminogen. 相似文献
7.
The autosomal mutation brachypod (bpH/bpH) in the mouse affects the development of precartilage mesenchymal condensation in the limb-bud. We have previously shown that this defect is localized to the expression of terminal N-acetylglucosamine (GlcNAc) glycoproteins in the plasma membrane (Elmer and Wright, '83). The present study is focused on cell surface galactosyltransferase (GalTase), an ectoenzyme that transfers galactose to its GlcNAc substrate. Purified plasma membrane preparations derived from wild-type (+/+), heterozygote (+/bpH) and brachypod (bpH/bpH) embryonic mouse limb cells were assayed for GalTase activity during in vitro and in utero chondrogenesis using High-Performance Liquid Chromatography (HPLC). On embryonic day E12, prior to overt expression of the mutant gene, no significant difference in GalTase activity was observed. By the third day in culture, all major chondrogenic elements of the autopod were present in +/+ and +/bpH embryos, whereas the mutant autopods were markedly deficient in staining and appeared consistently shorter. The accumulation of alcianophilic cartilage matrix in the wild-type was accompanied by a 29% increase in GalTase activity, which reflected the net change (29%) observed during development from days E12 to E13 in utero. The GalTase activity for the in utero E13 mutant (13%) was significantly different from control. In culture, day E12 mutant autopods actually decreased in their GalTase level by 3 days so that the activity was reduced to only 57% of the wild-type. Though GalTase activity in the heterozygote showed an intermediate expression, optical image analysis did not reveal consistent differences in cartilage development when compared to +/+, arguing against a gene-dosage effect at the gross anatomical level. These data indicate that an increase in plasma membrane GalTase activity is a natural developmental event that occurs during limb-bud chondrogenesis and a decrease in GalTase activity contributes to the dysmorphogenesis in brachypod limb-buds. 相似文献
8.
Floral scents of male and female inflorescences of three dioeciousSalix species were collected by head-space adsorption, and analysed by GC-MS. InSalix caprea andS. cinerea 1,4-dimethoxy benzene was the main compound, and male and female scents showed a high degree of resemblance. No dominant compound was found inS. repens and malefemale scent similarity was low. Floral scent inSalix is likely a strong orientation cue, guiding pollinators between male and female plants ensuring pollen transfer and pollination. We suggest that a high degree of male-female floral scent resemblance is coupled to a high degree of insect pollination. Floral scent does not promote reproductive isolation betweenS. caprea andS. cinerea. 相似文献
9.
Predictive model of conjugative plasmid transfer in the rhizosphere and phyllosphere. 总被引:4,自引:3,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
G R Knudsen M V Walter L A Porteous V J Prince J L Armstrong R J Seidler 《Applied microbiology》1988,54(2):343-347
A computer simulation model was used to predict the dynamics of survival and conjugation of Pseudomonas cepacia (carrying the transmissible recombinant plasmid R388:Tn1721) with a nonrecombinant recipient strain in simple rhizosphere and phyllosphere microcosms. Plasmid transfer rates were derived for a mass action model, and donor and recipient survival were modeled as exponential growth and decay processes or both. Rate parameters were derived from laboratory studies in which donor and recipient strains were incubated in test tubes with a peat-vermiculite solution or on excised radish or bean leaves in petri dishes. The model predicted donor, recipient, and transconjugant populations in hourly time steps. It was tested in a microcosm planted with radish seeds and inoculated with donor and recipient strains and on leaf surfaces of radish and bean plants also growing in microcosms. Bacteria were periodically enumerated on selective media over 7 to 14 days. When donor and recipient populations were 10(6) to 10(8) CFU/g (wet weight) of plant or soil, transconjugant populations of about 10(1) to 10(4) were observed after 1 day. An initial rapid increase and a subsequent decline in numbers of transconjugants in the rhizosphere and on leaf surfaces were correctly predicted. 相似文献
10.
Aerial Dispersal and Epiphytic Survival of Pseudomonas syringae during a Pretest for the Release of Genetically Engineered Strains into the Environment 总被引:15,自引:15,他引:0
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Steven E. Lindow Guy R. Knudsen Ramon J. Seidler Michael V. Walter Victor W. Lambou Penny S. Amy David Schmedding Valerie Prince Stephen Hern 《Applied microbiology》1988,54(6):1557-1563
Prospective experimental field evaluation of genetically engineered microorganisms, such as microbial pest control agents, raises issues of how to properly ascertain their fate and survival in the environment. Field trials with recombinant organisms must reflect requirements for sampling and monitoring. Field trials were conducted at Tulelake, Calif., to monitor the numbers of viable cells of a nonrecombinant strain of Pseudomonas syringae that entered the atmosphere and landed on plants and soil during and after an aerosol spray application. An exponential decrease in numbers of viable cells deposited at increasing distances from three sprayed plots was observed. The relative rate of survival of cells sprayed directly on plants was more than 10 times higher than that of cells dispersed through the air to similar adjacent plants. Results are being used to gain experience with the characteristics of a release site that influence containment or dispersal and to develop appropriate sampling methodologies for evaluating survival and dispersal characteristics of genetically engineered bacteria released into the environment. The ability to make predictions about microbial dispersal and survival will reduce the uncertainties associated with environmental releases of recombinant organisms. 相似文献