全文获取类型
收费全文 | 26816篇 |
免费 | 2388篇 |
国内免费 | 2306篇 |
专业分类
31510篇 |
出版年
2024年 | 48篇 |
2023年 | 222篇 |
2022年 | 509篇 |
2021年 | 809篇 |
2020年 | 635篇 |
2019年 | 744篇 |
2018年 | 771篇 |
2017年 | 648篇 |
2016年 | 892篇 |
2015年 | 1470篇 |
2014年 | 1713篇 |
2013年 | 1878篇 |
2012年 | 2370篇 |
2011年 | 2113篇 |
2010年 | 1453篇 |
2009年 | 1314篇 |
2008年 | 1664篇 |
2007年 | 1543篇 |
2006年 | 1429篇 |
2005年 | 1330篇 |
2004年 | 1248篇 |
2003年 | 1133篇 |
2002年 | 966篇 |
2001年 | 684篇 |
2000年 | 592篇 |
1999年 | 510篇 |
1998年 | 317篇 |
1997年 | 241篇 |
1996年 | 219篇 |
1995年 | 186篇 |
1994年 | 175篇 |
1993年 | 134篇 |
1992年 | 194篇 |
1991年 | 165篇 |
1990年 | 133篇 |
1989年 | 145篇 |
1988年 | 87篇 |
1987年 | 118篇 |
1986年 | 95篇 |
1985年 | 68篇 |
1984年 | 53篇 |
1983年 | 67篇 |
1982年 | 44篇 |
1981年 | 37篇 |
1980年 | 27篇 |
1979年 | 43篇 |
1978年 | 42篇 |
1977年 | 30篇 |
1976年 | 29篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Daren Lee Seth Ruffins Queenie Ng Nikhil Sane Steve Anderson Arthur Toga 《BMC bioinformatics》2010,11(1):608
Background
Digital atlases provide a common semantic and spatial coordinate system that can be leveraged to compare, contrast, and correlate data from disparate sources. As the quality and amount of biological data continues to advance and grow, searching, referencing, and comparing this data with a researcher's own data is essential. However, the integration process is cumbersome and time-consuming due to misaligned data, implicitly defined associations, and incompatible data sources. This work addressing these challenges by providing a unified and adaptable environment to accelerate the workflow to gather, align, and analyze the data. 相似文献2.
C Y Kwan 《Biochimica et biophysica acta》1985,819(1):148-152
Saponin, a cell-skinning reagent which perforates the cell membrane via its specific interaction with plasmalemmal cholesterol, was used to identify the subcellular origin of ATP-dependent Ca2+ accumulation in the presence and absence of inorganic phosphate and oxalate by microsomal fractions isolated from rat vas deferens and dog aorta. The purified plasma membranes from rat gastric fundus muscle, which elicit the stimulation of ATP-dependent Ca2+ accumulation by inorganic phosphate but not by oxalate, were used as a control reference. Saponin at concentrations effective for skinning smooth muscle fibres (10-50 micrograms/ml) inhibited Ca2+ binding in the absence of ATP to a similar extent in all fractions, but the inhibition of ATP-dependent Ca2+ accumulation was more pronounced in dog aorta microsomes and rat gastric fundus muscle plasma membranes than in rat vas deferens microsomes. The resistance of phosphate- and oxalate-stimulated ATP-dependent Ca2+ accumulation to inhibition by saponin was much greater in rat vas deferens than in dog aorta microsomes. Our results suggest that phosphate- and oxalate-stimulated ATP-dependent Ca2+ accumulation also occurs in plasma membrane vesicles isolated from smooth muscle and is by no means an unique property of endoplasmic reticulum. 相似文献
3.
Ai‐Xin Song Chen‐Jie Zhou Xiao Guan Kong‐Hung Sze Hong‐Yu Hu 《Protein science : a publication of the Protein Society》2010,19(5):1104-1109
DC‐UbP/UBTD2 is a ubiquitin (Ub) domain‐containing protein first identified from dendritic cells, and is implicated in ubiquitination pathway. The solution structure and backbone dynamics of the C‐terminal Ub‐like (UbL) domain were elucidated in our previous work. To further understand the biological function of DC‐UbP, we then solved the solution structure of the N‐terminal domain of DC‐UbP (DC‐UbP_N) and studied its Ub binding properties by NMR techniques. The results show that DC‐UbP_N holds a novel structural fold and acts as a Ub‐binding domain (UBD) but with low affinity. This implies that the DC‐UbP protein, composing of a combination of both UbL and UBD domains, might play an important role in regulating protein ubiquitination and delivery of ubiquitinated substrates in eukaryotic cells. 相似文献
4.
Xiuyun Ye Shigeru Yoshida T. B. Ng 《The international journal of biochemistry & cell biology》2000,32(11-12)
A mild and rapid method is described for isolating various milk proteins from bovine rennet whey. β-Lactoglobulin from bovine rennet whey was easily adsorbed on and desorbed from a weak anion exchanger, diethylaminoethyl-Toyopearl. However, α-lactalbumin could not be adsorbed onto the resin. α-Lactalbumin and β-lactoglobulin from rennet whey could also be adsorbed and separated using a strong anion exchanger, quaternary aminoethyl-Toyopearl. The rennet whey was passed through a strong cation exchanger, sulphopropyl-Toyopearl, to separate lactoperoxidase and lactoferrin. α-Lactalbumin and β-lactoglobulin were adsorbed onto quaternary aminoethyl-Toyopearl. α-Lactalbumin was eluted using a linear (0–0.15 M) concentration gradient of NaCl in 0.05 M Tris–HCl buffer (pH 8.5). Subsequently, β-lactoglobulin B and β-lactoglobulin A were eluted from the column with 0.05 M Tris–HCl (pH 6.8), using a linear (0.1–0.25 M) concentration gradient of NaCl. The yields were 1260 mg α-lactalbumin, 1290 mg β-lactoglobulin B and 2280 mg β-lactoglobulin A from 1 l rennet whey. 相似文献
5.
The Indochinese silvered langur (Trachypithecus germaini) is distributed to the west of Mekong River in Cambodia, Lao PDR, Thailand and Vietnam. During a two‐year study, from May 2014 to May 2016, we collected 320.44 hr of behavior, with 17,040 feeding bouts recorded (142 hr) for T. germaini on Chua Hang Karst Mountain, Kien Luong District, Kien Giang Province, Vietnam. Feeding accounted for 45% of the Indochinese silvered langurs’ activity budget. The plant diet of the Indochinese silvered langurs was principally composed of young leaves (58%), followed by mature leaves (9.5%), fruits (22.7%), flowers (4.7%), buds (3.3%), petioles (1.2%), and other (0.5%). A total of 58 plant species were fed on by the silvered langurs, and leaves of eight species (Phyllathus reticulatus, Ficus rumphii, Ficus tinctoria, Ficus microcarpa, Cayratia trifolia, Streblus ilicifolia, Combretum latifolium, and Streblus asper) were fed on throughout the year. P. reticulatus was most frequently eaten (13.9% feeding time, n = 1,733). Food selection differed significantly between months and seasons. The Indochinese silvered langurs ate 27 plant species in the wet season compared with 23 plant species in the dry season. Leaf chemical composition of two food categories, 16 eaten species (with 10 most frequently consumed species and six least consumed species), and four noneaten species, were analyzed. Feeding samples from eaten species in the Indochinese silvered langurs's diet contained lower amounts of condensed tannin, lignin, protein, ash, and lipids, but a higher amount of total sugar compared with samples from noneaten species. Furthermore, the most frequently consumed species contained lower amounts of lignin compared with the less frequently consumed species. Using a generalized linear model with five variables, including neutral detergent fiber (NDF), total sugar, lignin, lipid, and calcium (Ca) indicated that NDF positively correlated and lignin content negatively correlated with feeding records in the diet of these langur. 相似文献
6.
We tried to establish compatible carbon content models of individual trees for a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantation from Fujian province in southeast China. In general, compatibility requires that the sum of components equal the whole tree, meaning that the sum of percentages calculated from component equations should equal 100%. Thus, we used multiple approaches to simulate carbon content in boles, branches, foliage leaves, roots and the whole individual trees. The approaches included (i) single optimal fitting (SOF), (ii) nonlinear adjustment in proportion (NAP) and (iii) nonlinear seemingly unrelated regression (NSUR). These approaches were used in combination with variables relating diameter at breast height (D) and tree height (H), such as D, D2H, DH and D&H (where D&H means two separate variables in bivariate model). Power, exponential and polynomial functions were tested as well as a new general function model was proposed by this study. Weighted least squares regression models were employed to eliminate heteroscedasticity. Model performances were evaluated by using mean residuals, residual variance, mean square error and the determination coefficient. The results indicated that models with two dimensional variables (DH, D2H and D&H) were always superior to those with a single variable (D). The D&H variable combination was found to be the most useful predictor. Of all the approaches, SOF could establish a single optimal model separately, but there were deviations in estimating results due to existing incompatibilities, while NAP and NSUR could ensure predictions compatibility. Simultaneously, we found that the new general model had better accuracy than others. In conclusion, we recommend that the new general model be used to estimate carbon content for Chinese fir and considered for other vegetation types as well. 相似文献
7.
8.
9.
Relationships between induced high leaf intercellular CO2 concentrations, leaf K+ and NO3 ? ion movement and early fruit formation under macronutrient limitation are not well understood. We examined the effects and interactions of reduced K/N input treatments on leaf intercellular CO2, photosynthesis rate, carboxylation and water use efficiency, berry formation as well as leaf/fruit K+, NO3 ? and photosynthate retention of strawberry (Fragaria × ananassa Duch.) to enhance low-input agriculture. The field study was conducted in Nova Scotia, eastern Canada during 2009–2010. The experimental treatments consisted of five K2O rates (0, 6, 12, 18, and 24 kg ha?1) and five N rates (0, 5, 10, 15, and 20 kg ha?1), representing respectively, 0, 25, 50, 75, and 100 % of regular macronutrient recommendations based on the soil testing. The treatments were arranged in a split-plot design with three blocks in the field. The cultivar was ‘Mira’, a June-bearing crop. The results showed that strawberry plants treated with 25 %-reduced inputs could induce significantly higher leaf intercellular CO2 concentrations to improve plant photosynthesis, carboxylation and water use efficiency and translocation of leaf/fruit K+ and dissolved solids, which could advance berry formation by 6 days and produce significantly higher marketable yields (P < 0.05). Higher leaf intercellular CO2 inhibited leaf/fruit NO3 ? ion retention, but this inhibition did not occur in leaf/fruit K+ retention. Linear interactions of the K/N treatments were significant on fruit marketable yields, intercellular CO2, net photosynthesis, leaf transpiration rates, and leaf temperatures (P < 0.05). It was concluded that higher leaf CO2 could enhance plant photosynthesis, promote plant carboxylation and water use efficiency, and advance berry formation, but it could inhibit leaf NO3 ? retention. This inhibition did not find in leaf K+ ion and dissolved solid retention. Overlay co-limitation of leaf intercellular CO2 and translocation of leaf/fruit K+/NO3 ? and total dissolved solids could constrain more fruit formation attributes under full macronutrient supply than reduced inputs. It was suggested that low input would be an optimal and sustainable option for improving small fruit crop physiological development and dealing with macronutrient deficiency challenge. 相似文献
10.