全文获取类型
收费全文 | 2232篇 |
免费 | 150篇 |
专业分类
2382篇 |
出版年
2022年 | 28篇 |
2021年 | 54篇 |
2020年 | 27篇 |
2019年 | 33篇 |
2018年 | 48篇 |
2017年 | 39篇 |
2016年 | 77篇 |
2015年 | 89篇 |
2014年 | 109篇 |
2013年 | 138篇 |
2012年 | 144篇 |
2011年 | 141篇 |
2010年 | 91篇 |
2009年 | 79篇 |
2008年 | 100篇 |
2007年 | 93篇 |
2006年 | 98篇 |
2005年 | 81篇 |
2004年 | 67篇 |
2003年 | 48篇 |
2002年 | 44篇 |
2001年 | 59篇 |
2000年 | 44篇 |
1999年 | 46篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1992年 | 26篇 |
1990年 | 29篇 |
1989年 | 17篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 30篇 |
1985年 | 21篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 20篇 |
1981年 | 25篇 |
1980年 | 13篇 |
1979年 | 24篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1975年 | 20篇 |
1974年 | 17篇 |
1973年 | 17篇 |
1972年 | 22篇 |
1971年 | 13篇 |
1970年 | 15篇 |
1969年 | 14篇 |
排序方式: 共有2382条查询结果,搜索用时 0 毫秒
991.
S Chaudhuri J Ghosh B Mukherjee A K Roychoudhury 《American journal of physical anthropology》1967,26(3):307-311
Blood specimens of the Santals in Midnapore District of West Bengal, India were tested for the antigens A, B, C, D, E, c and e, when the incidence of B gene was found to be 26.8%. Another feature of the Santals was the high frequency (74.6%) of CDe chromosome with complete absence of cde. Trace of sickle-cell trait was also noticed among the Santals as is known to occur in some of the aboriginal tribes of the Nilgiri Hills, Uttar Pradesh, Gujarat and Western India. HbS was the only haemoglobin variant detected among them. 相似文献
992.
The molecular mechanism(s) of immunoglobulin A (IgA) nephropathy, the most common primary renal glomerular disease worldwide, is unknown. Its pathologic features include hematuria, high levels of circulating IgA-fibronectin (Fn) complexes, and glomerular deposition of IgA, complement C3, Fn and collagen. We report here that two independent mouse models (gene knockout and antisense transgenic), both manifesting deficiency of an anti-inflammatory protein, uteroglobin (UG), develop almost all of the pathologic features of human IgA nephropathy. We further demonstrate that Fn-UG heteromerization, reported to prevent abnormal glomerular deposition of Fn and collagen, also abrogates both the formation of IgA-Fn complexes and their binding to glomerular cells. Moreover, UG prevents glomerular accumulation of exogenous IgA in UG-null mice. These results define an essential role for UG in preventing mouse IgA nephropathy and warrant further studies to determine if a similar mechanism(s) underlies the human disease. 相似文献
993.
Two diterpenoid quinones, 20-hydroxy-7α-acetoxyroyleanone and royleanone, have been isolated from the whole plant (aerial parts and roots) of Salvia lanata. 相似文献
994.
995.
996.
997.
Kirsten Heimann B. Becker Helga Harnisch K. D. Mukherjee M. Melkonian 《Plant biology (Stuttgart, Germany)》1997,110(5):401-410
Plasma membrane vesicles (PMVs) were isolated from Cyanophora paradoxa Korshikov (Claucocystophyta) and purified by differential and sucrose density gradient centrifugation. PMVs were identified ultrastructurally and biochemically using marker enzymes. Analysis of monosaccharides revealed a sugar content of 37.3% of dry weight of delipidated PMVs with high amounts of fucose (28 mol% of total carbohydrate), galactose (23%), mannose (21%) and the minor constituents xylose, rhamnose, glucose and N-acetylglucosamine. Proteins were analyzed by SDS-PACE. More than 20 polypeptides were resolved and several were identified as glycopeptides, as shown by PAS staining and lectin blots. Fucose linked α-1→6 to N-acetylglucosamine (AAA-binding), mannose linked α-1→2,3,6 to mannose (CNA-binding) and terminally bound galactose (RCA-binding) were identified on several polypeptides. Sterols (β-sitosterol and an additional unknown sterol, 40% of total lipids) and diacylglycerol (43%) are the major lipid components in the PMVs of C. paradoxa. Minor components are PE, PC, PC and an unknown glycolipid. Fatty acid analysis revealed 12 different fatty acids, predominantly 16:0,18:0 and the polyunsaturated acids 20:4 and 20:5 (together 69% of total fatty acids), α-Linolenic acid, common in higher plant PMs, could only be detected as a minor constituent (< 1 %) of PMVs of C. paradoxa. 相似文献
998.
Yeast extract (0.5%) stimulates the production of glucoamylase and cell synthesis while methylene blue (0.1 mM) activates the synthesis of glucoamylase. Studies on the metabolic changes during fermentation of glucoamylase in a selected medium by P. italicum show that the rate of production of glucoamylase and cellular growth are greatly accelerated between 48 and 168 hr. Rapid growth of cells during this period may account for enhanced utilization of maltose and NH4NO3 from the medium. The acid production remains constant from 48 to 144 hr. Different forms of nitrogen decrease steadily. Although methylene blue stimulates the production of glucoamylase in the broth it has practically no effect on the rate of utilization of amino and total nitrogen from the broth. 相似文献
999.
Aspects of plant growth such as height, branch number, leaf number, leaf area, pod area, 100-seed mass, etc., were correlated with biochemical changes such as contents of chlorophyll (Chl), proteins, DNA, and RNA, and protease activity
during development and senescent phases in leaves, flowers, and pods of Cajanus cajan L. cv. UPAS-120 after treatments with kinetin (Kn). A significant increase was noticed in branch number, leaf number, leaf
area, and seed mass while other growth processes registered a small increase after Kn application. Effectiveness of 5 μM Kn
was also noticed in minimizing the loss of Chls, proteins, and nucleic acids as well as reducing the protease activity during
maturity and senescence. Chl a/b ratio maintained a high value up to 30-d followed by a decline in leaves while flowers registered much lower ratio at 20-d-age.
Pods were unique in having relatively lower ratio of Chl a/b in comparison to leaves. 相似文献
1000.
In an attempt to isolate chitinase producers from soil, a streptomycete strain was found potent using natural chitin as the substrate. Chitinolytic activity was tested directly on agar plates, also with crude enzyme. Chitinase assay showed that the isolate could produce 0.8 U/ml of the enzyme. The morphological, cultural, physiological and biochemical characters of the isolate P10 were studied, and identified as Streptomyces venezuelae P10. 相似文献