全文获取类型
收费全文 | 1000篇 |
免费 | 115篇 |
专业分类
1115篇 |
出版年
2022年 | 10篇 |
2021年 | 13篇 |
2019年 | 11篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 23篇 |
2014年 | 28篇 |
2013年 | 40篇 |
2012年 | 49篇 |
2011年 | 41篇 |
2010年 | 42篇 |
2009年 | 37篇 |
2008年 | 40篇 |
2007年 | 30篇 |
2006年 | 30篇 |
2005年 | 35篇 |
2004年 | 24篇 |
2003年 | 24篇 |
2002年 | 34篇 |
2001年 | 26篇 |
2000年 | 33篇 |
1999年 | 23篇 |
1998年 | 18篇 |
1997年 | 20篇 |
1996年 | 20篇 |
1995年 | 11篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 22篇 |
1990年 | 13篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1980年 | 9篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1975年 | 14篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1971年 | 8篇 |
1969年 | 11篇 |
1968年 | 9篇 |
1967年 | 9篇 |
排序方式: 共有1115条查询结果,搜索用时 15 毫秒
51.
Peter Woodward 《Visual Anthropology: Published in cooperation with the Commission on Visual Anthropology》2013,26(3-4):307-330
This article seeks to explore the use of photography as a tool for ethnographic research, having regard to the nature of participant observation as the primary method involved. A study of Jewish children in the center of England highlights a range of creative possibilities for the use of photography. An examination of the Jewish tradition reinforces the need for depth of understanding if one is to forge a truly empathetic relationship that links subject and object in photographic exploration. 相似文献
52.
Barbara R. Evans Amanda K. Gilman Kimberley Cordray Jonathan Woodward 《Biotechnology letters》2000,22(9):735-740
A cellulase from the thermophile, Thermotoga maritima, hydrolyzed oligosaccharide substrates by an exoglucanase mode of action but acted as an endoglucanase to rapidly reduce the viscosity of the soluble polysaccharides carboxymethylcellulose and barley -glucan. The V
max for hydrolysis of the substrate, p-nitrophenyl -d-cellobioside, was 42 mol min–1 (mg protein)–1, while that for barley -glucan was 637. The enzyme had little activity on crystalline cellulose. 相似文献
53.
The temperature and pH optima, and the temperature and pH stability, of crude and purified enzymes of the cellulase complex of the cellulolytic ascomycete fungus Neurospora crassa were investigated. The effects of some non-ionic surfactants and fatty acids on the production/release of enzymes of cellulase complex were also examined. For the different enzymes of the complex, activity maxima occurred between pH 4.0 and 7.0, with pH 5.0 being close to optimal for stability of all. Temperature optima for activity ranged between 45 and 65 degrees C, with the stability optimum between 45 and 50 degrees C. The presence of C18 fatty acids and surfactants resulted in increased production of both endoglucanase and exoglucanase in the medium. Oleic acid was the most effective fatty acid tested, and Tween 80 the most effective surfactant. Oleic acid had no detectable effect on production of beta-glucosidase, and Tween 80 actually reduced its production. 相似文献
54.
Priyanka Chakraborty Jason T George Wendy A Woodward Herbert Levine Mohit Kumar Jolly 《Translational oncology》2021,14(4):101026
Inflammatory breast cancer (IBC) is a highly aggressive breast cancer that metastasizes largely via tumor emboli, and has a 5-year survival rate of less than 30%. No unique genomic signature has yet been identified for IBC nor has any specific molecular therapeutic been developed to manage the disease. Thus, identifying gene expression signatures specific to IBC remains crucial. Here, we compare various gene lists that have been proposed as molecular footprints of IBC using different clinical samples as training and validation sets and using independent training algorithms, and determine their accuracy in identifying IBC samples in three independent datasets. We show that these gene lists have little to no mutual overlap, and have limited predictive accuracy in identifying IBC samples. Despite this inconsistency, single-sample gene set enrichment analysis (ssGSEA) of IBC samples correlate with their position on the epithelial-hybrid-mesenchymal spectrum. This positioning, together with ssGSEA scores, improves the accuracy of IBC identification across the three independent datasets. Finally, we observed that IBC samples robustly displayed a higher coefficient of variation in terms of EMT scores, as compared to non-IBC samples. Pending verification that this patient-to-patient variability extends to intratumor heterogeneity within a single patient, these results suggest that higher heterogeneity along the epithelial-hybrid-mesenchymal spectrum can be regarded to be a hallmark of IBC and a possibly useful biomarker. 相似文献
55.
J. K. Klar W. B. Homoky P. J. Statham A. J. Birchill E. L. Harris E. M. S. Woodward B. Silburn M. J. Cooper R. H. James D. P. Connelly F. Chever A. Lichtschlag C. Graves 《Biogeochemistry》2017,135(1-2):49-67
Shelf sediments underlying temperate and oxic waters of the Celtic Sea (NW European Shelf) were found to have shallow oxygen penetrations depths from late spring to late summer (2.2–5.8 mm below seafloor) with the shallowest during/after the spring-bloom (mid-April to mid-May) when the organic carbon content was highest. Sediment porewater dissolved iron (dFe, <0.15 µm) mainly (>85%) consisted of Fe(II) and gradually increased from 0.4 to 15 μM at the sediment surface to ~100–170 µM at about 6 cm depth. During the late spring this Fe(II) was found to be mainly present as soluble Fe(II) (>85% sFe, <0.02 µm). Sub-surface dFe(II) maxima were enriched in light isotopes (δ56Fe ?2.0 to ?1.5‰), which is attributed to dissimilatory iron reduction (DIR) during the bacterial decomposition of organic matter. As porewater Fe(II) was oxidised to insoluble Fe(III) in the surface sediment layer, residual Fe(II) was further enriched in light isotopes (down to ?3.0‰). Ferrozine-reactive Fe(II) was found in surface porewaters and in overlying core top waters, and was highest in the late spring period. Shipboard experiments showed that depletion of bottom water oxygen in late spring can lead to a substantial release of Fe(II). Reoxygenation of bottom water caused this Fe(II) to be rapidly lost from solution, but residual dFe(II) and dFe(III) remained (12 and 33 nM) after >7 h. Iron(II) oxidation experiments in core top and bottom waters also showed removal from solution but at rates up to 5-times slower than predicted from theoretical reaction kinetics. These data imply the presence of ligands capable of complexing Fe(II) and supressing oxidation. The lower oxidation rate allows more time for the diffusion of Fe(II) from the sediments into the overlying water column. Modelling indicates significant diffusive fluxes of Fe(II) (on the order of 23–31 µmol m?2 day?1) are possible during late spring when oxygen penetration depths are shallow, and pore water Fe(II) concentrations are highest. In the water column this stabilised Fe(II) will gradually be oxidised and become part of the dFe(III) pool. Thus oxic continental shelves can supply dFe to the water column, which is enhanced during a small period of the year after phytoplankton bloom events when organic matter is transferred to the seafloor. This input is based on conservative assumptions for solute exchange (diffusion-reaction), whereas (bio)physical advection and resuspension events are likely to accelerate these solute exchanges in shelf-seas. 相似文献
56.
57.
T. A. Wheeler K. T. Siders M. G. Anderson S. A. Russell J. E. Woodward B. G. Mullinix Jr. 《Journal of nematology》2014,46(2):101-107
Management of Meloidogyne incognita (root-knot nematode) in cotton in the United States was substantially affected by the decision to stop production of aldicarb by its principle manufacturer in 2011. The remaining commercially available tools to manage M. incognita included soil fumigation, nematicide seed treatments, postemergence nematicide application, and cultivars partially resistant to M. incognita. Small plot field studies were conducted on a total of nine sites from 2011–2013 to examine the effects of each of these tools alone or in combinations, on early season galling, late-season nematode density in soil, yield, and value ($/ha = lint value minus chemical costs/ha). The use of a partially resistant cultivar resulted in fewer galls/root system at 35 d after planting in eight of nine tests, lower root-knot nematode density late in the growing season for all test sites, higher lint yield in eight of nine sites, and higher value/ha in six of nine sites. Galls per root were reduced by aldicarb in three of nine sites and by 1,3-dichloropropene (1,3-D) in two of eight sites, relative to the nontreated control (no insecticide or nematicide treatment). Soil fumigation reduced M. incognita density late in the season in three of nine sites. Value/ha was not affected by chemical treatment in four of nine sites, but there was a cultivar × chemical interaction in four of nine sites. When value/ha was affected by chemical treatment, the nontreated control had a similar value to the treatment with the highest value/ha in seven of eight cultivar-site combinations. The next “best” value/ha were associated with seed treatment insecticide (STI) + oxamyl and aldicarb (similar value to the highest value/ha in six of eight cultivar-site combinations). The lowest valued treatment was STI + 1,3-D. In a semi-arid region, where rainfall was low during the spring for all three years, cultivars with partial resistance to M. incognita was the most profitable method of managing root-knot nematode in cotton. 相似文献
58.
OBJECTIVE: To determine the extent of variation in physicians'' charges for health care encounters with unannounced standardized patients and factors associated with the variation. DESIGN: Cross-sectional study. SETTING: Family practices open to new patients within 1 hour''s drive of Hamilton, Ont. PARTICIPANTS: A stratified random sample of 125 physicians who had responded to an earlier survey regarding preventive care were invited to participate. Of the 125, 44 (35.2%) declined to participate, and an additional 19 (15.2%) initially consented but later withdrew because they closed their practices to new patients. Sixty-two physicians thus participated in the study. INTERVENTION: Unannounced standardized patients posing as new patients to the practice visited study physicians'' practices between September 1994 and August 1995, portraying 4 scenarios: 28-year-old woman, 52-year-old woman, 48-year-old man and 70-year-old man. OUTCOME MEASURES: Physician characteristics, encounter characteristics and charges made for services. RESULTS: The 62 physicians had 246 encounters with the standardized patients. Charges were made to the health insurance plan for services by 59 physicians for up to 4 encounters (215 encounters in all). Charges varied considerably both within and across patient scenarios. Time spent with the patient was an important factor predicting charges made (p < 0.01), although the effect of time spent on charges varied across scenarios (p < 0.01). Fee-for-service physicians charged more for their services than physicians who usually had alternative billing arrangements (p < 0.01). Female physicians charged more for their services than their male colleagues (p = 0.03). No relation was found between quality of preventive care and charges made (p = 0.15). CONCLUSIONS: Physician-related factors are better able to account for the variability in charges for their services than patient-related factors. Physicians seeing comparable patients may earn much more or less than their colleagues because of differences in the services they provide and the way they apply the fee schedule. Quality-assurance techniques are likely needed to reduce the variability in charges seen and increase value for money spent in health care. 相似文献
59.
60.
Liang Y Li C Guzman VM Evinger AJ Protzman CE Krauss AH Woodward DF 《The Journal of biological chemistry》2003,278(29):27267-27277
Connective tissue growth factor (CTGF) and Cyr61 (cysteine-rich angiogenic protein 61) are members of the CCN gene family that encode multifunctional, extracellular matrix-associated signaling proteins. Because the mechanism of action of certain anti-glaucoma drugs involves extracellular matrix remodeling of ocular ciliary muscle, with a resultant increase in drainage of aqueous humor from the eye, we compared the effects of three pharmacologically distinct ocular hypotensive agents on Cyr61 and CTGF gene expression. Thus, prostaglandin F2alpha (PGF2alpha) (FP receptor agonist), Butaprost (EP2 receptor agonist), and Bimatoprost (a prostamide) were compared. Using Affymetrix gene chip technology, we first identified that PGF2alpha dramatically up-regulated Cyr61 and CTGF mRNA expression in HEK 293/EBNA cells (hFP-HEK 293/EBNA). Northern blot further confirmed the Cyr61 and CTGF up-regulation is in a dose- and time-dependent manner. PGF2alpha-induced up-regulation of Cyr61 appeared to exclusively involve the Rho pathway, and up-regulation of CTGF was via multiple intracellular pathways. Because prostamide receptors are, to date, defined only at the pharmacological level, Bimatoprost effects on Cyr61 and CTGF were studied in the isolated feline iris sphincter preparation, a tissue highly responsive to prostamides. Both PGF2alpha and Bimatoprost up-regulated Cyr61 mRNA expression in the cat iris tissue. Only PGF2alpha up-regulated CTGF mRNA expression in the cat iris. Therefore, PGF2alpha and Bimatoprost appear to interact with different receptors populations in the cat iris, according to their markedly different effects on CTGF. Activation of prostaglandin EP2 receptors (Gs-coupled) also up-regulated Cyr61 but not CTGF mRNA expression in the isolated cat iris. Similar data were observed in human primary ciliary smooth muscle cells. Thus, despite quite different signal transduction pathways, FP receptor stimulation up-regulates CTGF and Cyr61. The prostamide analog Bimatoprost and an EP2-selective agonist affects only Cyr61. 相似文献