全文获取类型
收费全文 | 749779篇 |
免费 | 82611篇 |
国内免费 | 559篇 |
专业分类
832949篇 |
出版年
2018年 | 6874篇 |
2017年 | 6641篇 |
2016年 | 9277篇 |
2015年 | 12060篇 |
2014年 | 14203篇 |
2013年 | 20922篇 |
2012年 | 23004篇 |
2011年 | 23579篇 |
2010年 | 15927篇 |
2009年 | 14646篇 |
2008年 | 20914篇 |
2007年 | 21531篇 |
2006年 | 20309篇 |
2005年 | 19512篇 |
2004年 | 19310篇 |
2003年 | 18486篇 |
2002年 | 17896篇 |
2001年 | 36201篇 |
2000年 | 36210篇 |
1999年 | 28383篇 |
1998年 | 9360篇 |
1997年 | 10102篇 |
1996年 | 9422篇 |
1995年 | 8627篇 |
1994年 | 8371篇 |
1993年 | 8407篇 |
1992年 | 22878篇 |
1991年 | 22187篇 |
1990年 | 21351篇 |
1989年 | 20853篇 |
1988年 | 19167篇 |
1987年 | 17978篇 |
1986年 | 16760篇 |
1985年 | 16734篇 |
1984年 | 13705篇 |
1983年 | 11585篇 |
1982年 | 8777篇 |
1981年 | 7974篇 |
1980年 | 7538篇 |
1979年 | 13021篇 |
1978年 | 9975篇 |
1977年 | 9383篇 |
1976年 | 8520篇 |
1975年 | 9424篇 |
1974年 | 10280篇 |
1973年 | 10023篇 |
1972年 | 9128篇 |
1971年 | 8390篇 |
1970年 | 7320篇 |
1969年 | 6980篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Y Tani I Ohkubo S Higashiyama M Kunimatsu M Sasaki 《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,88(2):429-441
1. High mol. wt kininogen (HMW kininogen) was purified to a homogeneous state from porcine plasma. 2. The protein exhibited a strong inhibitory activity for thiol proteinases such as ficin, papain and calpain I, whereas it did not inhibit serine proteinases, trypsin and chymotrypsin. 3. The mol. wt, isoelectric point, amino acid and carbohydrate compositions, stabilities to temperature and pH, kinetic constants, and immunological properties of the porcine HMW kininogen were determined and compared with those of human HMW kininogen. 相似文献
22.
B B Fuks N F Avrova L V Van'ko N A Starosvetskaia M N Boltovskaia 《Biulleten' eksperimental'no? biologii i meditsiny》1986,101(1):66-68
Female BALB/c mice were immunized with human melanoma (Mewo) cells containing ganglioside GD3 as a surface antigen. Immune splenocytes were fused with syngeneic P3-X63.Ag 8 myeloma cells. Antibodies produced by hybrid clones were analyzed by solid phase immunoassay. B, C, D and Q clones producing antibodies against Raja clavata brain gangliosides were obtained. Monoclonal B and C antibodies bound monosialogangliosides. Monoclonal D antibody bound a number of gangliosides but reacted predominantly with GD1a. Monoclonal Q antibody reacted selectively with GQ1c. It is assumed that ganglioside GQ1c is expressed on the melanoma cell surface and may be found only in the early stage of ontogenesis of high vertebrates. 相似文献
23.
24.
S Kh Khaduev O S Zhukova Ia V Dobrynin K Soda T T Berezov 《Biulleten' eksperimental'no? biologii i meditsiny》1986,101(5):603-604
L-lysine-alpha-oxidase, a new fungal enzyme catalyzing oxidative deamination of L-lysine, exerts an inhibitory effect on DNA, RNA and protein synthesis in human cells of carcinoma ovarius (CaOv) in vitro. 相似文献
25.
P C de Visser N M A J Kriek P A V van Hooft A Van Schepdael D V Filippov G A van der Marel H S Overkleeft J H van Boom D Noort 《The journal of peptide research》2003,61(6):298-306
As part of a program towards the development of novel antibiotics, a convenient method for solid-phase synthesis of the cyclic cationic peptide polymyxin B1 and analogues thereof is described. The methodology, based on cleavage-by-cyclization using Kenner's safety-catch linker, yields crude products with purities ranging from 37-67%. Antibacterial assays revealed that analogues 23-26, in which the (S)-6-methyloctanoic acid moiety is replaced with shorter acyl chains, exhibit distinct antimicrobial activity. The results suggest that the length of the acyl chain is rather critical for antimicrobial activity. On the other hand, substitution of the hydrophobic ring-segment D-Phe-6/Leu-7 in polymyxin B1 with dipeptide mimics (i.e. analogues 27-33) resulted in almost complete loss of antimicrobial activity. 相似文献
26.
Localization of cathepsin D in rat liver. Immunocytochemical study using post-embedding immunoenzyme and protein A-gold techniques 总被引:1,自引:0,他引:1
Light and electron microscopic localization of cathepsin D in rat liver was investigated by post-embedding immunoenzyme and protein A-gold techniques. By light microscopy, cytoplasmic granules of parenchymal cells and Kupffer cells were stained for cathepsin D. Weak staining was also noted in sinusoidal endothelial cells. In the parenchymal cells many of positive granules located around bile canaliculi. In the Kupffer cells and the endothelial cells, diffuse staining was noted in the cytoplasm in addition to granular staining. By electron microscopy, gold particles representing the antigenic sites for cathepsin D were seen in typical secondary lysosomes and some multivesicular bodies of the parenchymal cells and Kupffer cells. The lysosomes of the endothelial cells and fat-storing cells were weakly labeled. Quantitative analysis of the labeling density in the lysosomes of these three types of cells demonstrated that the lysosomes of parenchymal cells and Kupffer cells are main containers of cathepsin D in rat liver. The results suggest that cathepsin D functions in the intracellular digestive system of parenchymal cells and Kupffer cells but not so much in that of the endothelial cells. 相似文献
27.
28.
R. A. Mueller M. J. Rosner J. N. Ghia S. K. Powers E. R. Kafer R. D. Hunt 《Cellular and molecular neurobiology》1988,8(2):235-243
1. Examination of the cerebrospinal fluid (CSF) of head-injured patients reveals that the concentration of intraventricular xanthine is elevated and that of uridine is decreased relative to those of adult lumbar CSF. 2. No correlations were observed between CSF lactate and CSF hypoxanthine, xanthine, or uridine, suggesting that changes in purine metabolites and the pyrimidine nucleoside do not index similar cellular events as does lactic acid production. 3. Ventricular CSF from hydrocephalic infants had uridine and hypoxanthine concentrations not significantly different from those of normal adult lumbar CSF, but xanthine was significantly elevated. 4. Since uridine has anticonvulsant properties and is a crucial substrate for cerebral metabolism, it may be useful to evaluate this pyrimidine for use in the management of patients with head injury. 相似文献
29.
30.