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1.
The kinetics of the electrostatically induced phase transition of dimyristoyl phosphatidic acid bilayers was followed using the stopped-flow technique. The phase transition was triggered by a fast change in the pH or the magnesium ion concentration and followed by recording the time dependence of the absorbance. When the phase transition was induced by a pH jump the time course of the absorbance could be described by two exponentials, their time constants displaying the for cooperative processes characteristic maximum at the transition midpoint. The time constants are in the 10 and 100 ms range for the H+ triggered transition from the fluid to the ordered state. A third slower process shows no appreciable temperature dependence and is probably caused by vesicle aggregation. For the OH--induced transition fron the ordered to the fluid state the time constants are in the 100 and 1000 ms range. The fluid-ordered transition could also be triggered by addition of magnesium ions. Of the several observed processes only the fastest in the 10–100 ms time range could definitely be assigned to the fluid-ordered transition while the others are due to aggregation phenomena. The experimental data were compared with results obtained from pressure jump experiments and could be interpreted on the basis of theories for non-equilibrium relaxation. 相似文献
2.
Khalid M. Chraibi B Jean-Claude Castelle Alain Latche Jean-Paul Roustan Jean Fallot 《Plant cell reports》1992,10(12):617-620
We describe here a liquid culture system for the regeneration of shoots at high frequencies from mature cotyledon tissues of three genotypes of sunflower (Helianthus annuus L.) one of which had previously been found to be recalcitrant to regeneration when cotyledons were cultured on solid medium. Cotyledons were excised from 2-day-old seedlings and incubated in liquid Murashige and Skoog's modified medium supplemented with 5.4 M naphthaleneacetic acid (NAA) and 4.4 M benzylaminopurine (BAP). After two weeks in culture, the whole upper surface of regenerating explants was covered with green shootlets. The percentages of regenerating explants of three genotypes varied between 60 and 70%, and the number of shoots per regenerating explant was highly increased. The shootlets were transferred to solid Murashige and Skoog's medium allowing shoot development, then to rooting medium. Rooted plantlets were successfully acclimatized and gave fertile plants. The role of liquid medium culture in the induction of sunflower regeneration is discussed.Abbreviations BAP
6-benzylaminopurine
- NAA
1-naphthaleneacetic acid
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid 相似文献
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Khalid Meksem Dario Leister Johan Peleman Marc Zabeau Francesco Salamini Christiane Gebhardt 《Molecular & general genetics : MGG》1995,249(1):74-81
The R1 allele confers on potato a race-specific resistance to Phytophthora infestans. The corresponding genetic locus maps on chromosome V in a region in which several other resistance genes are also located. As part of a strategy for cloning R1, a high-resolution genetic map was constructed for the segment of chromosome V that is bordered by the RFLP loci GP21 and GP179 and includes the R1 locus. Bulked segregant analysis and markers based on amplified fragment length polymorphisms (AFLP markers) were used to select molecular markers closely linked to R1. Twenty-nine of approximately 3200 informative AFLP loci displayed linkage to the R1 locus. Based on the genotypic analysis of 461 gametes, eight loci mapped within the GP21–GP179 interval. Two of those could not be seperated from R1 by recombination. For genotyping large numbers of plants with respect to the flanking markers GP21 and GP179 PCR based assays were also developed which allowed marker-assisted selection of plants with genotypes Rr and rr and of recombinant plants. 相似文献
6.
Mazhar N. Malik Laurie A. Meyers Khalid Iqbal Ashfaq M. Sheikh Lois Scotto Henryk M. Wisniewski 《Life sciences》1981,29(8):795-802
A Ca2+ activated protease(s) capable of hydrolyzing several polypeptides at neutral pH including cytoskeletal proteins, actin, myosin, tubulin and neurofilament triplet was identified in calf brain cortex. The enzyme activity precipitates at 75 mM KCl, pH 6.5 – 7.0 and is inhibited by the sulfhydryl inhibitors, N-ethylmaleimide and para-chloromercuribenzoate and the protease inhibitors, antipain, pepstatin and leupeptin, leupeptin being the most effective. 相似文献
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Krupa Madhvani Silvia Fernandez Garcia Borja M. Fernandez-Felix Javier Zamora Tyrone Carpenter Khalid S. Khan 《CMAJ》2022,194(38):E1306
Background:Hysterectomy, the most common gynecological operation, requires surgeons to counsel women about their operative risks. We aimed to develop and validate multivariable logistic regression models to predict major complications of laparoscopic or abdominal hysterectomy for benign conditions.Methods:We obtained routinely collected health administrative data from the English National Health Service (NHS) from 2011 to 2018. We defined major complications based on core outcomes for postoperative complications including ureteric, gastrointestinal and vascular injury, and wound complications. We specified 11 predictors a priori. We used internal–external cross-validation to evaluate discrimination and calibration across 7 NHS regions in the development cohort. We validated the final models using data from an additional NHS region.Results:We found that major complications occurred in 4.4% (3037/68 599) of laparoscopic and 4.9% (6201/125 971) of abdominal hysterectomies. Our models showed consistent discrimination in the development cohort (laparoscopic, C-statistic 0.61, 95% confidence interval [CI] 0.60 to 0.62; abdominal, C-statistic 0.67, 95% CI 0.64 to 0.70) and similar or better discrimination in the validation cohort (laparoscopic, C-statistic 0.67, 95% CI 0.65 to 0.69; abdominal, C-statistic 0.67, 95% CI 0.65 to 0.69). Adhesions were most predictive of complications in both models (laparoscopic, odds ratio [OR] 1.92, 95% CI 1.73 to 2.13; abdominal, OR 2.46, 95% CI 2.27 to 2.66). Other factors predictive of complications included adenomyosis in the laparoscopic model, and Asian ethnicity and diabetes in the abdominal model. Protective factors included age and diagnoses of menstrual disorders or benign adnexal mass in both models and diagnosis of fibroids in the abdominal model.Interpretation:Personalized risk estimates from these models, which showed moderate discrimination, can inform clinical decision-making for people with benign conditions who may require hysterectomy.Hysterectomy is one of the most frequently performed surgical procedures. Canada has one of the highest rates of hysterectomy globally, with one-third of women undergoing this procedure before 60 years of age.1 Minimal access approaches are favoured by both clinicians and patients,2 and the proportion of hysterectomies being undertaken by a laparoscopic approach has increased substantially in many countries over the last 10 years.3–7 The evidence-based medicine paradigm for surgical approaches to hysterectomy for benign disease advocates that the chosen surgical approach should be discussed with the patient by their surgeon and decided in light of the relative benefits and risks.2 This advice is echoed by national guidelines.8,9Most clinicians undertaking hysterectomy will intuitively identify patient characteristics that have the potential to increase the complexity and complications of surgery. A 2016 systematic review of studies that reported significant associations between patient characteristics and surgical outcomes for laparoscopic hysterectomy and a 2020 population-based prospective cohort study using data from the Danish hysterectomy database have suggested that older age, race, raised body mass index (BMI), diabetes mellitus, increased uterine weight, fibroids, endometriosis and adhesions are predictors of complications in patients undergoing hysterectomy for benign indications.10,11 However, assimilating this information to individualize and anticipate the precise risk for each patient if there are multiple factors present can be challenging. A 2020 systematic review reported that surgeons in other specialties were outperformed by risk prediction models in estimating postoperative risk and outcomes; their discriminatory ability showed greater variation (C-statistic 0.51–0.75) than other risk prediction tools.12Patients should be given information about potential risks before surgery to manage expectations.13 This is especially important when surgery is considered for benign disease because nonsurgical options are often available.Our aim was to generate prediction models that can be used in conjunction with a surgeon’s intuition to enhance preoperative patient counselling and match the advances made in the technical aspects of surgery. We sought to quantify the proportion of patients who underwent hysterectomy for benign disease and will have a major complication, and to develop and validate prognostic models to individualize this risk, using a national data set. 相似文献
9.
Syed Mohsin Bukhari Huda Ahmed Alghamdi Khalil Ur Rehman Shahla Andleeb Shahbaz Ahmad Nimra Khalid 《Saudi Journal of Biological Sciences》2022,29(3):1781-1788
Pheasant reintroduction and conservation efforts have been in place in Pakistan since the 1980 s, yet there is still a scarcity of data on pheasant microbiome and zoonosis. Instead of growing vast numbers of bacteria in the laboratory, to investigate the fecal microbiome, pheasants (green and ring neck pheasant) were analyzed using 16S rRNA metagenomics and using IonS5TMXL sequencing from two flocks more than 10 birds. Operational taxonomic unit (OTU) cluster analysis and phylogenetic tree analysis was performed using Mothur software against the SSUrRNA database of SILVA and the MUSCLE (Version 3.8.31) software. Results of the analysis showed that firmicutes were the most abundant phylum among the top ten phyla, in both pheasant species, followed by other phyla such as actinobacteria and proteobacteria in ring necked pheasant and bacteroidetes in green necked pheasant. Bacillus was the most relatively abundant genus in both pheasants followed by Oceanobacillus and Teribacillus for ring necked pheasant and Lactobacillus for green necked pheasant. Because of their well-known beneficial characteristics, these genus warrants special attention. Bird droppings comprise germs from the urinary system, gut, and reproductive sites, making it difficult to research each anatomical site at the same time. We conclude that metagenomic analysis and classification provides baseline information of the pheasant fecal microbiome that plays a role in disease and health. 相似文献
10.
Alonso Adel C Mederlyova A Novak M Grundke-Iqbal I Iqbal K 《The Journal of biological chemistry》2004,279(33):34873-34881
Mutations in the tau gene are known to cosegregate with the disease in frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17). However, the molecular mechanism by which these mutations might lead to the disease is not understood. Here, we show that four of the FTDP-17 tau mutations, R406W, V337M, G272V, and P301L, result in tau proteins that are more favorable substrates for phosphorylation by brain protein kinases than the wild-type, largest four-repeat protein tau4L and tau4L more than tau3L. In general, at all the sites studied, mutant tau proteins were phosphorylated faster and to a higher extent than tau4L and tau4L > tau3L. The most dramatic difference found was in the rate and level of phosphorylation of tau4L(R406W) at positions Ser-396, Ser-400, Thr-403, and Ser-404. Phosphorylation of this mutant tau was 12 times faster and 400% greater at Ser-396 and less than 30% at Ser-400, Thr-403, and Ser-404 than phosphorylation of tau4L. The mutated tau proteins polymerized into filaments when 4-6 mol of phosphate per mol of tau were incorporated, whereas wild-type tau required approximately 10 mol of phosphate per mol of protein to self-assemble. Mutated and wild-type tau proteins were able to sequester normal tau upon incorporation of approximately 4 mol of phosphate per mol of protein, which was achieved at as early as 30 min of phosphorylation in the case of mutant tau proteins. These findings taken together suggest that the mutations in tau might cause neurodegeneration by making the protein a more favorable substrate for hyperphosphorylation. 相似文献