全文获取类型
收费全文 | 497篇 |
免费 | 53篇 |
专业分类
550篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 23篇 |
2015年 | 32篇 |
2014年 | 35篇 |
2013年 | 39篇 |
2012年 | 44篇 |
2011年 | 42篇 |
2010年 | 19篇 |
2009年 | 17篇 |
2008年 | 23篇 |
2007年 | 20篇 |
2006年 | 19篇 |
2005年 | 10篇 |
2004年 | 17篇 |
2003年 | 16篇 |
2002年 | 8篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1972年 | 3篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有550条查询结果,搜索用时 0 毫秒
1.
Cristina Sánchez-Roldán Antonio Heredia Victoriano Valpuesta Martin J. Bukovac 《Journal of Plant Growth Regulation》1990,9(1-3):171-174
The indole-3-acetic acid (IAA) content in peach pericarp (Prunus persica L. Batsch cv. Merry) was highest at early stage I of development (200 ng/g fresh wt), decreased to the lowest level during stage II, and rose again at stage III to 60–70 ng/g fresh wt. High activity of glutamine synthetase was found in the pericarp during stage I. The soluble peroxidase activity was highest in the meso- and exocarp at stage II, and isoenzymatic changes in this fraction corresponded to the transition from cationic isoenzymes, predominant at stage I, to anionic isoenzymes at stage III. The ionically bound peroxidase activity in these tissues was highest at stage I. The three developmental stages showed marked differences in auxin content and enzyme activities; for peroxidases these changes reflect a developmental expression pattern for the isoenzymes. 相似文献
2.
3.
4.
Summary Saponite support considerably increased the kinetics of a. semicontinuous anaerobic digestion process treating soft drink wastewater showing values of the max andK kinetic parameters (Chen and Hashimoto model) 2.5 and 1.4 times higher than for bentonite and polyurethane support, respectively. This was significant at 95% confidence level. 相似文献
5.
6.
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
7.
阿根廷前科迪勒拉区寒武─奥陶系地层发育。中晚奥陶世时,前科迪勒拉东部与中部山区为浅水陆棚相,西部山区为斜坡─盆地相。牙形刺的分布主要与平静的暖水大洋有关。寒武纪仅发现晚寒武世Proconodontus带,此期间有一次海侵事件。在奥陶纪发现了牙形刺并可识别出四次海侵事件三次海退事件和二次缺氧事件。 相似文献
8.
Ana Gonzlez Moreno Eva Domínguez Konrad Mayer Nannan Xiao Peter Bock Antonio Heredia Notburga Gierlinger 《Plant physiology》2023,191(1):219
The cuticle is a protective extracellular matrix that covers the above-ground epidermis of land plants. Here, we studied the cuticle of tomato (Solanum lycopersicum L.) fruits in situ using confocal Raman microscopy. Microsections from cuticles isolated at different developmental stages were scanned to visualize cuticle components with a spatial resolution of 342 nm by univariate and multivariate data analysis. Three main components, cutin, polysaccharides, and aromatics, were identified, with the latter exhibiting the strongest Raman scattering intensity. Phenolic acids and flavonoids were differentiated within the cuticle, and three schematic cuticle models were identified during development. Phenolic acids were found across the entire cuticle at the earliest stage of development, i.e. during the formation of the procuticle layer. Based on a mixture analysis with reference component spectra, the phenolic acids were identified as mainly esterified p-coumaric acid together with free p-hydroxybenzoic acid. During the cell expansion period of growth, phenolic acids accumulated in an outermost layer of the cuticle and in the middle region of the pegs. In these stages of development, cellulose and pectin were detected next to the inner cuticle region, close to the epidermal cell where flavonoid impregnation started during ripening. In the first ripening stage, chalconaringenin was observed, while methoxylated chalcones were chosen by the algorithm to fit the mature cuticle spectra. The colocation of carbohydrates, esterified p-coumaric acid, and methoxylated chalconaringenin suggests that the latter two link polysaccharide and cutin domains. Elucidating the different distribution of aromatics within the cuticle, suggests important functions: (1) overall impregnation conferring mechanical and thermal functions (2) the outermost phenolic acid layer displaying UV-B protection of the plant tissue.Raman mapping and multivariate data analysis provide insights into the distribution of cutin, carbohydrates, and phenolics along cross sections of green and mature tomato fruit cuticles. 相似文献
9.
10.
Borja Cascales-Mi?ana Jesús Mu?oz-Bertomeu María Flores-Tornero Armand Djoro Anoman José Pertusa Manuel Alaiz Sonia Osorio Alisdair R. Fernie Juan Segura Roc Ros 《The Plant cell》2013,25(6):2084-2101
This study characterizes the phosphorylated pathway of Ser biosynthesis (PPSB) in Arabidopsis thaliana by targeting phosphoserine phosphatase (PSP1), the last enzyme of the pathway. Lack of PSP1 activity delayed embryo development, leading to aborted embryos that could be classified as early curled cotyledons. The embryo-lethal phenotype of psp1 mutants could be complemented with PSP1 cDNA under the control of Pro35S (Pro35S:PSP1). However, this construct, which was poorly expressed in the anther tapetum, did not complement mutant fertility. Microspore development in psp1.1/psp1.1 Pro35S:PSP1 arrested at the polarized stage. The tapetum from these lines displayed delayed and irregular development. The expression of PSP1 in the tapetum at critical stages of microspore development suggests that PSP1 activity in this cell layer is essential in pollen development. In addition to embryo death and male sterility, conditional psp1 mutants displayed a short-root phenotype, which was reverted in the presence of Ser. A metabolomic study demonstrated that the PPSB plays a crucial role in plant metabolism by affecting glycolysis, the tricarboxylic acid cycle, and the biosynthesis of amino acids. We provide evidence of the crucial role of the PPSB in embryo, pollen, and root development and suggest that this pathway is an important link connecting primary metabolism with development. 相似文献