全文获取类型
收费全文 | 2232篇 |
免费 | 205篇 |
国内免费 | 4篇 |
专业分类
2441篇 |
出版年
2023年 | 11篇 |
2022年 | 27篇 |
2021年 | 33篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 28篇 |
2017年 | 16篇 |
2016年 | 45篇 |
2015年 | 88篇 |
2014年 | 111篇 |
2013年 | 94篇 |
2012年 | 168篇 |
2011年 | 133篇 |
2010年 | 89篇 |
2009年 | 70篇 |
2008年 | 130篇 |
2007年 | 118篇 |
2006年 | 123篇 |
2005年 | 104篇 |
2004年 | 90篇 |
2003年 | 92篇 |
2002年 | 76篇 |
2001年 | 66篇 |
2000年 | 61篇 |
1999年 | 32篇 |
1998年 | 18篇 |
1997年 | 19篇 |
1996年 | 19篇 |
1995年 | 14篇 |
1994年 | 22篇 |
1993年 | 12篇 |
1992年 | 27篇 |
1991年 | 32篇 |
1990年 | 22篇 |
1989年 | 34篇 |
1988年 | 34篇 |
1987年 | 31篇 |
1986年 | 33篇 |
1985年 | 32篇 |
1984年 | 19篇 |
1983年 | 23篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 22篇 |
1978年 | 14篇 |
1977年 | 24篇 |
1976年 | 14篇 |
1974年 | 12篇 |
1973年 | 17篇 |
排序方式: 共有2441条查询结果,搜索用时 15 毫秒
51.
52.
A specific and potent immunotoxin composed of antibody ZME-018 and the plant toxin gelonin 总被引:1,自引:0,他引:1
M G Rosenblum J L Murray L Cheung R Rifkin S Salmon R Bartholomew 《Molecular biotherapy》1991,3(1):6-13
Murine monoclonal antibody ZME-018 recognizes a 240 Kda glycoprotein present on the surface of most human melanoma cells and on over 80% of human biopsy specimens tested. Gelonin is a ribosome-inactivating plant toxin similar in nature and rivaling the activity of ricin A chain. ZME-018 was coupled to purified gelonin using the reagents SPDP and 2-iminothiolane. The ZME-gelonin conjugate was purified by S-300 Sephacryl and Blue Sepharose chromatography, removing unreacted gelonin and antibody, respectively. PAGE analysis showed that ZME was coupled to 1, 2, or 3 gelonin molecules. The ZME-gelonin conjugate was 10(6)-fold more active than gelonin itself in inhibiting the growth of log-phase human melanoma cells in culture. The immunoconjugate was not cytotoxic to antigen negative T-24 (human bladder carcinoma) cells. Treatment of melanoma cells with recombinant IFN-alpha or TNF substantially augmented the cytotoxicity of the immunoconjugate while treatment with IFN-gamma had a minor effect. Using the human tumor colony assay of melanoma cells obtained from fresh biopsy specimens, greater than 90% growth suppression was observed in 2 of 4 samples tested at a concentration of 250 ng/ml. In addition, 25% growth suppression was observed with a third sample tested, and no growth suppression was observed in 1 sample. Thus, clonogenic melanoma cells are sensitive in vitro to the cytotoxic activity of this immunotoxin at concentrations which we presume are pharmacologically relevant. 相似文献
53.
The expression of granulocyte/macrophage colony-stimulating factor (GM-CSF) was studied in spleen lymphocytes isolated from male C57BL/6J mice of 6, 20, and 29 months of age. GM-CSF expression (biological activity and mRNA level) was maximum after culturing the lymphocytes for 45 hr with concanavalin A and phorbol myristate acetate. The induction of both GM-CSF activity and mRNA levels was observed to decline over 60% between 6 and 29 months of age. The age-related decline in the level of GM-CSF paralleled the age-related decline in the mRNA levels of interleukin-2 and interleukin-3. 相似文献
54.
Phenylglyoxal reacts much more rapidly with N2-acetylarginine than with either N2-acetyllysine or N-acetylcysteine. The rate of the reaction of phenylglyoxal with either N-acetylarginine or arginine increases with increasing pH from 7.5 to 11.5. The model reaction with arginine is much faster in bicarbonate, diethylamine, or triethylamine buffer than in N-ethylmorpholine, borate, phosphate, or Tris buffer. This activation by various buffers should be taken into consideration when glyoxal derivatives are used to modify arginyl residues. 相似文献
55.
Extracts of Wistaria floribunda seeds contain separable erythroagglutinating and lymphocyte mitogenic activities. We wish to report the purification and characterization of the erythroagglutinating lectin of these seeds. A phosphate-buffered saline (PBS) extract of the ground seeds was made to 50% ethanol and the precipitate, which contained both the agglutinin and mitogen, was dissolved in PBS. The erythroagglutinating activity was adsorbed onto insoluble polyleycyl derivatized A + H active hog gastric mucin. After desorption with 0.2 M D-galactose and removal of the sugar by dialysis, the eluate displayed three protein bands on polyacrylamide gel electrophoresis. The major component represented 85% of the mixture. Immunoelectrophoresis of the mixture demonstrated immunochemical identity among the proteins. Gel filtration through Sephadex G-200 resulted in purification of the major component. Based upon the composition and subunit molecular weight, it was concluded that the three components represent a dimer, tetramer, and octamer of a single glycopolypeptide chain of 28 000. The erythroagglutinin has a pI at pH 5.4 and one cystine per dimeric unit. 相似文献
56.
57.
When 1,N6-ethenoadenosine triphosphate (epsilon-ATP) is free in solution, its fluorescence is collisionally quenched by iodide ion, by methionine, by tryptophan, and by cysteine. None of these quenches the fluorescence of epsilon-ATP bound to G-actin. Thus, the ethenoadenine base is bound in a region of the protein which is inaccessible to collisions with these reagents. Since we have previously shown that the fluorescence of epsilon-ATP is quenched by water, the long lifetime of epsilon-ATP bound to G-actin (36 nsec, vs 27 nsec for epsilon-ATP in water) indicates that the bound nucleotide base is inaccessible to collisional quenching by water molecules. 相似文献
58.
59.
60.
Little information is available on the interaction between lymphocytes and fibronectin (fn). To gain a better understanding on this issue we examined the adhesion of 12 lymphoid cell lines, each exhibiting different phenotypic characteristics, to fn-coated substratum. Of the cell lines tested, five that adhered to fn possessed B-cell characteristics, while neither the T-cell lines nor the pre-B-cell line adhered. The physiology and biochemistry of adhesion of a B-cell line, MOPC 315, were examined in detail. Our results indicated that (1) the adhesion was a specific and time-dependent process, (2) the adhesion was temperature-dependent and inhibited by metabolic inhibitors, such as KCN and 2-deoxyglucose, (3) the presence of cycloheximide and pretreatment of cells with trypsin inhibited adhesion, (4) a 140-kDa surface protein was immunoprecipitated by anti-fn receptor antibodies, (5) the presence of divalent cations was essential for adhesion, (6) the presence of colchicine had no effect on adhesion, while cytochalasin B partially inhibited adhesion, and (7) the treatment of cells by both phorbol 12-myristate 13-acetate and calcium ionophore A23187 enhanced adhesion. In this study, we have established the interaction between lymphoid cell lines and fn. Such an interaction might play an important role in the behavior of lymphocytes in tissues. 相似文献