全文获取类型
收费全文 | 161192篇 |
免费 | 12520篇 |
国内免费 | 11492篇 |
专业分类
185204篇 |
出版年
2024年 | 337篇 |
2023年 | 1968篇 |
2022年 | 4439篇 |
2021年 | 7412篇 |
2020年 | 5001篇 |
2019年 | 6183篇 |
2018年 | 6345篇 |
2017年 | 4861篇 |
2016年 | 6695篇 |
2015年 | 9106篇 |
2014年 | 11072篇 |
2013年 | 11802篇 |
2012年 | 14087篇 |
2011年 | 12912篇 |
2010年 | 8360篇 |
2009年 | 7411篇 |
2008年 | 8593篇 |
2007年 | 7679篇 |
2006年 | 6788篇 |
2005年 | 5398篇 |
2004年 | 4863篇 |
2003年 | 4374篇 |
2002年 | 3749篇 |
2001年 | 3232篇 |
2000年 | 2920篇 |
1999年 | 2632篇 |
1998年 | 1508篇 |
1997年 | 1552篇 |
1996年 | 1406篇 |
1995年 | 1280篇 |
1994年 | 1291篇 |
1993年 | 927篇 |
1992年 | 1316篇 |
1991年 | 1141篇 |
1990年 | 856篇 |
1989年 | 769篇 |
1988年 | 629篇 |
1987年 | 583篇 |
1986年 | 540篇 |
1985年 | 532篇 |
1984年 | 318篇 |
1983年 | 293篇 |
1982年 | 231篇 |
1981年 | 194篇 |
1980年 | 160篇 |
1979年 | 177篇 |
1978年 | 148篇 |
1974年 | 121篇 |
1973年 | 123篇 |
1972年 | 117篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
<正>Aristolochic acids, mutational signature, and hepatocellular carcinoma Aristolochic acids (AA) are the etiologic agents of aristolochic acid nephropathy (AAN) and contribute to the global prevalence of chronic kidney disease and urothelial cancer (Grollman et al., 2007). DNA adducts formed by AA generate a unique AT transversions mutation spectrum at 相似文献
43.
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
44.
O. B. Kazakova E. F. Khusnutdinova G. A. Tolstikov K. Yu. Suponitsky 《Russian Journal of Bioorganic Chemistry》2010,36(4):512-515
New olean-18(19)-ene triterpenoids were effectively synthesized by the interaction of allobetulin or its acetate with phosphorous
oxychloride in refluxing pyridine. The structures of the synthesized 17-chloromethyloleane-18(19)-enes were confirmed by NMR
spectroscopy and X-ray analysis. 相似文献
45.
46.
Following arteriolar occlusion, tissue oxygen concentration decreases and anoxic tissue eventually develops. Although anoxia
first appears in the region most distal to the capillary at the venous end, it eventually spreads throughout the entire region
of supply. In this paper the changing oxygen concentration, from the time of occlusion until the tissue is entirely anoxic,
is examined mathematically. The equations governing oxygen transport to tissue are solved by iterating a nonlinear integral
equation. This solution is valid until anoxia first appears. After anoxia develops it is necessary to solve a moving boundary
problem. This is done using the method of matched asymptotic expansions, and accurate solutions are obtained for a wide range
of physiological conditions. 相似文献
47.
L. A. Piruzyan V. A. Sukhanov E. V. Kalinina T. Yu. Fedorova A. N. Saprin 《Biology Bulletin》2002,29(2):115-119
We studied intraspecific features of the main enzymes of metabolism and detoxication of xenobiotics on mice (eight inbred lines) and rats (five lines) for estimation of possible variants of complete or incomplete metabolic equality. Significant genetically determined intraspecific differences for activities of the enzymes of metabolism and detoxication of xenobiotics were described. Generalized criteria for comparison of the metabolic status were proposed on the basis of activities of the main enzymes: cytochrome P-450 (hydroxylation and epoxidation), epoxyhydrolase, glutathione-S-transferase, UDP-glucuronosyl transferase, and sulfotransferase. The proposed criteria for estimation of the metabolic parameters of an individual can serve as a basis of metabolic portraiting. 相似文献
48.
C Wang 《Biochimica et biophysica acta》1986,888(1):107-115
Insulin receptors of rat skeletal muscle were purified by first extracting a plasma membrane-enriched pellet obtained from a muscle homogenate with Triton X-100, followed by WGA-Sepharose and insulin-Sepharose affinity chromatography. Routinely, 4-5 micrograms of purified receptor were obtained from 15 g of tissue. The purified receptors are composed of two major polypeptides with molecular weights of 130,000 and 95,000, respectively. The binding of [125I]insulin by the purified receptors was analyzed by a Scatchard plot. There are at least two binding components. The high-affinity component, with an apparent association constant (Ka) of 2.0 X 10(9) M-1, comprises 10% of the total insulin binding sites; while the low-affinity component, with a Ka value of 1.4 X 10(8) M-1, represents 90% of the binding sites. Assuming the insulin receptor to have a molecular weight of 300,000, the receptor binds 1.7 mol of insulin per mol at saturation. Insulin is capable of stimulating the autophosphorylation of the beta-subunit of the muscle insulin receptor (Mr 95,000) by 5-10-fold. The stoichiometry of this phosphorylation reaction was determined as 0.8 phosphate per insulin binding site after a 10 min incubation with 100 nM insulin. In a previous report, I showed that the insulin stimulation of glucose transport in diaphragms from neonatal rats was small, even although the diaphragms had normal levels of insulin receptors and glucose transporters (Wang, C. (1985). Proc. Natl. Acad. Sci. USA 82, 3621-3625). To determine whether or not receptor autophosphorylation might be related to this insensitivity to insulin, the level of receptor phosphorylation was quantitated in diaphragms from rats at different stages of development. Autophosphorylation remains unchanged from birth to 21 days of age, suggesting that the lower insulin-stimulated glucose uptake by diaphragms at early stages of postnatal development as compared to that by diaphragms of older rats, is not due to a difference in receptor kinase. 相似文献
49.
50.