全文获取类型
收费全文 | 3169篇 |
免费 | 186篇 |
出版年
2022年 | 11篇 |
2021年 | 32篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 29篇 |
2017年 | 39篇 |
2016年 | 57篇 |
2015年 | 84篇 |
2014年 | 72篇 |
2013年 | 148篇 |
2012年 | 141篇 |
2011年 | 166篇 |
2010年 | 92篇 |
2009年 | 93篇 |
2008年 | 165篇 |
2007年 | 156篇 |
2006年 | 163篇 |
2005年 | 166篇 |
2004年 | 159篇 |
2003年 | 140篇 |
2002年 | 167篇 |
2001年 | 113篇 |
2000年 | 111篇 |
1999年 | 98篇 |
1998年 | 56篇 |
1997年 | 55篇 |
1996年 | 30篇 |
1995年 | 26篇 |
1994年 | 35篇 |
1993年 | 23篇 |
1992年 | 70篇 |
1991年 | 58篇 |
1990年 | 52篇 |
1989年 | 51篇 |
1988年 | 75篇 |
1987年 | 47篇 |
1986年 | 32篇 |
1985年 | 24篇 |
1984年 | 31篇 |
1983年 | 21篇 |
1982年 | 23篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 21篇 |
1978年 | 23篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 20篇 |
1971年 | 13篇 |
1968年 | 10篇 |
排序方式: 共有3355条查询结果,搜索用时 15 毫秒
81.
Leukotriene A: stereochemistry and enzymatic conversion to leukotriene B 总被引:13,自引:0,他引:13
Olof Rådmark Curt Malmsten Bengt Samuelsson David A. Clark Giichi Goto Anthony Marfat E.J. Corey 《Biochemical and biophysical research communications》1980,92(3):954-961
Leukotriene A was assigned the structure 5(S)--5,6-oxido-7,9--eicosatetraenoic acid by the enzymatic conversion of a synthetic product of known stereochemistry into the naturally occurring isomer of 5(S),12(R)-dihydroxy-6,8,10,14-eicosatetraenoic acid in human polymorphonuclear leukocytes. 相似文献
82.
David A. Clark Giichi Goto Anthony Marfat E.J. Corey Sven Hammarström Bengt Samuelsson 《Biochemical and biophysical research communications》1980,94(4):1133-1139
A slow reacting substance, produced by murine mastocytoma cells, has been shown to have the structure 5(S)-hydroxy-6(R)--glutathionyl-7,9,11- leukotriene C, previously referred to as leukotriene C-2) by ultraviolet spectroscopy, amino acid analyses, lipoxygenase conversion and comparisions with a synthetic compound of known structure and stereochemistry. 相似文献
83.
Formation of bile acids in hemoglobin-free perfused rat livers 总被引:1,自引:0,他引:1
84.
85.
Purification, characterization, and amino acid sequences of pepsinogens and pepsins from the esophageal mucosa of bullfrog (Rana catesbeiana) 总被引:1,自引:0,他引:1
E Yakabe M Tanji M Ichinose S Goto K Miki K Kurokawa H Ito T Kageyama K Takahashi 《The Journal of biological chemistry》1991,266(33):22436-22443
Two pepsinogens (pepsinogens 1 and 2) were purified from the esophageal mucosa of the bullfrog (Rana catesbeiana), and their molecular weights were determined to be 40,100 and 39,200, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The NH2-terminal 70-residue sequences of both pepsinogens are the same, including the 36-residue activation segment. Furthermore, a cDNA clone encoding frog pepsinogen was obtained and sequenced, which permitted deduction of the complete amino acid sequence (368 residues) of one of the pepsinogen isozymogens. The calculated molecular weight of the protein (40,034) coincided well with the values obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These results are incompatible with the previous report (Shugerman R. P., Hirschowitz, B. I., Bhown, A. S., Schrohenloher, R. E., and Spenney, J. G. (1982) J. Biol. Chem. 257, 795-798) that the major pepsinogen isolated from the bullfrog esophageal gland is a unique "mini" pepsinogen with a molecular weight of approximately 32,000-34,000. The two pepsinogens were immunologically indistinguishable from each other and related to human pepsinogen C. The deduced amino acid sequence was also more homologous with those of pepsinogens C than those of pepsinogens A and prochymosin. These results indicate that the frog pepsinogens belong to the pepsinogen C group. They were both glycoproteins, and therefore, this is the first finding of carbohydrate-containing pepsinogens C. Both pepsinogens were activated to pepsins in the same manner by an apparent one-step mechanism. The resulting pepsins were enzymatically indistinguishable from each other, and their properties resembled those of tuna pepsins. 相似文献
86.
Isolation and identification of bile salts conjugated with cysteinolic acid from bile of the red seabream, Pagrosomus major. 总被引:1,自引:0,他引:1
M Une T Goto K Kihira T Kuramoto K Hagiwara T Nakajima T Hoshita 《Journal of lipid research》1991,32(10):1619-1623
Bile salts present in gallbladder of wild and cultured red seabream, Pagrosomus major, a marine teleost were analyzed. The bile from wild red seabream was found to contain two previously unknown bile salts along with two known bile salts, taurocholate and taurochenodeoxycholate. Isolation of each bile salt was performed by column chromatography. Fast atom bombardment mass spectra of the unknown bile salts showed the molecular ions (M-H)- of m/z 544 and 528 which are shifted 30 mass units upfield compared to those (m/z 514 and 498) of taurocholate and taurochendeoxycholate, respectively; this is consistent with the presence of cysteinolic acid (mol wt 155) instead of taurine (mol wt 125). Enzymatic hydrolysis of the bile salts released cholic acid and chenodeoxycholic acid, respectively, and an amino acid that was identified as D-cysteinolic acid by direct comparison with an authentic sample. From these results, the bile salts in the bile of wild red seabream were identified as the conjugates of cholic acid and chenodeoxycholic acid with cysteinolic acid. 1H- and 13C-magnetic resonance spectra of the bile salts were also consistent with the proposed structure. The cysteinolic acid conjugates were found only in wild and not in cultured red seabream; this distinction seems to result from differences in dietary cysteinolic acid. 相似文献
87.
The skin and lymphoid organs of Mexican hairless dogs and their hairless offspring were examined histologically. The hairless dogs lacked most hairs except for sparse hairs on the head, tail and feet. The skin of newborn pups consisted of a thick epidermis with epidermal ingrowths forming the rudiments of hair follicles. In older dogs more than 2 months of age, however, the epidermis was thin and the ingrowths were few. Neither hair follicles nor skin glands were present. The hairy skin of the head and tail had hair follicles with sebaceous glands. Regarding the lymphoid organs, the newborn pups possessed a thymus like haired pups. But in the older dogs more than 2 months of age, the thymus was atrophied and the lymphocyte population was too sparse to demarcate the cortex and the medulla. Lymphocyte accumulation in older dogs was also poor in the spleen and mesenteric lymph nodes. The present findings indicate that the hairlessness of the Mexican hairless dogs and their descendants is accompanied by early atrophy of the thymus after birth, and is followed by poor accumulation of lymphocytes in the thymus-dependent area of the spleen and the mesenteric lymph nodes. The defect of the thymus in the hairless dog seems to be different from that in athymic nude mice and rats. Further studies are needed to elucidate the immunological response and function in hairless dogs. 相似文献
88.
Biochemical and Immunological Characterization of Collagenase in Tissues of Metamorphosing Bullfrog Tadpoles 总被引:5,自引:4,他引:1
Tissue inhibitor of metalloproteinases (TIMP, a specific inhibitor of collagenase) was found to inhibit thyroid hormone-induced tail regression, suggesting the important role of collagenase in this process. Collagenase was purified from culture media of back skin of tadpole of bullfrog, Rana catesbeiana . Anti-tadpole collagenase polyclonal antisera were obtained against the purified enzyme. The antibody inhibited the activity of tadpole collagenase. The antisera reacted to tissues of adult bullfrogs, tadpoles of african clawed frog, Xenopus laevis , and adult newts, Cynopus pyrrhogaster , and also reacted to human fibroblast collagenase. Immunoblot analyses suggested that tadpole collagenase lacks the procollagenase which is generally found in mammalian collagenases. Intense immunological stains were observed for the tissues of thyroid hormone-treated tadpoles as compared to those of untreated animals. Thyroid hormone increased amounts of collagenase not only in epidermal layer but also in mesenchymal tissues including fibroblastic cells. 相似文献
89.
A Moribayashi N Goto Y Arimitsu K Himeno S Tatsuki 《Japanese journal of medical science & biology》1991,44(3):87-97
Lipids and fatty acids of Leptospira interrogans serovar copenhageni virulent strain Shibaura were analyzed by thin-layer chromatography, gas-liquid chromatography, gas-mass spectrometry and infrared absorption spectrometry. The virulent cells possessed a characteristic lipid pattern consisting of free fatty acid (FFA) (41.8%), one major unidentified phospholipid (14.8%), phosphatidylethanolamine (PE) (12.9%), cholesteryl ester (CE) (9.3%), lysophosphatidylethanolamine (LPE) (4.9%) and diphosphatidyl-glycerol (DPG) (1.1%). Various fatty acids such as hexadecanoic (26.9%), hexadecenoic (15.4%), octadecenoic (26.5%) and octadecadienoic (27.4%) acids were detected in the FFA. The fatty acid composition of the major unidentified phospholipid distinctly differed from those of other lipids including PE, LPE, DPG and CE, and comprised mainly tetradecadienoic (53.6%), tetradecatrienoic (14.0%) and octadecanoic (13.8%) acids. This phospholipid with a large amount of polyunsaturated fatty acids with chain lengths of 14 carbon atoms was detected only in the lipids of the virulent cells. 相似文献
90.
The molten globule has been assumed to be a major intermediate state of protein folding. To extend our understanding of protein folding it is important to elucidate the thermodynamic mechanism of conformational stability of the molten globule. To clarify the role of electrostatic charge repulsion in the stability of the acidic molten globule state, we prepared a series of acetylated horse ferricytochrome c species with various degrees of charge repulsion. On the basis of circular dichroism measurement, we show that the stability of the acidic molten globule is determined by a balance of electrostatic repulsions between positive residues, which favor the extended conformation, and the opposing forces, which stabilize the molten globule. These results provide a clear example of charge repulsions producing unfolding of the compact protein structure, and suggest that the reversibly denatured conformation of ferricytochrome c under physiological conditions (i.e. neutral pH, ambient temperature and no denaturant) is the molten globule. 相似文献