全文获取类型
收费全文 | 175697篇 |
免费 | 10896篇 |
国内免费 | 11139篇 |
专业分类
197732篇 |
出版年
2023年 | 2354篇 |
2022年 | 3628篇 |
2021年 | 4741篇 |
2020年 | 4944篇 |
2019年 | 6626篇 |
2018年 | 5457篇 |
2017年 | 4224篇 |
2016年 | 4622篇 |
2015年 | 6035篇 |
2014年 | 9533篇 |
2013年 | 12570篇 |
2012年 | 7669篇 |
2011年 | 10285篇 |
2010年 | 7688篇 |
2009年 | 8390篇 |
2008年 | 8809篇 |
2007年 | 8961篇 |
2006年 | 8075篇 |
2005年 | 7235篇 |
2004年 | 6352篇 |
2003年 | 5489篇 |
2002年 | 4873篇 |
2001年 | 3574篇 |
2000年 | 3107篇 |
1999年 | 3087篇 |
1998年 | 2861篇 |
1997年 | 2480篇 |
1996年 | 2277篇 |
1995年 | 2441篇 |
1994年 | 2272篇 |
1993年 | 2063篇 |
1992年 | 1997篇 |
1991年 | 1749篇 |
1990年 | 1513篇 |
1989年 | 1387篇 |
1988年 | 1330篇 |
1987年 | 1285篇 |
1986年 | 944篇 |
1985年 | 1522篇 |
1984年 | 2019篇 |
1983年 | 1507篇 |
1982年 | 1878篇 |
1981年 | 1369篇 |
1980年 | 1376篇 |
1979年 | 1210篇 |
1978年 | 773篇 |
1977年 | 658篇 |
1976年 | 563篇 |
1975年 | 420篇 |
1973年 | 425篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Nancy Burton Wurster George Lust 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,800(1):52-58
The content and the biosynthesis of fibronectin was examined in disease-free articular cartilage and in articular cartilage from osteoarthritic canine joints. Fibronectin content was increased in extracts of cartilage from osteoarthritic joints. Incubation of cartilage in vitro with [3H]phenylalanine and subsequent isolation of [3H]fibronectin from a gelatin affinity column and characterization by SDS-polyacrylamide gel electrophoresis and by immunoprecipitation indicated that disease-free and osteoarthritic cartilage explants synthesized fibronectin. About 50% of the [3H]fibronectin was recovered in the incubation medium. The osteoarthritic cartilage synthesized and accumulated up to 5-fold more [3H]fibronectin than disease-free cartilage. 相似文献
92.
The distribution of vitamin K epoxidase activity in rough and smooth microsomes has been studied and compared to the prothrombin precursor and vitamin K-dependent carboxylase activity. All three activities were high in rough microsomes as compared to the low levels found in smooth microsomes. The results are in agreement with the suggestion that there might be a linkage between the vitamin K-dependent carboxylation and epoxidation reaction in vivo. 相似文献
93.
94.
ANATH BANDHU DAS ARUP KUMAR MUKHERJEE PREMANANDA DAS 《Botanical journal of the Linnean Society. Linnean Society of London》2001,136(2):221-229
Random amplified polymorphic DNA (RAPD) markers are used to estimate interspecific variation among mangrove and non-mangrove Heritiera fomes, H. littoralis and H. macrophylla. All the species have 2n = 38 chromosomes, with minute structural changes distinguishing the karyotype of each species. Significant variation of 4C DNA content occurs at the interspecific level. Interspecific polymorphism ranged from 14.09% between H. fomes and H. littoralis to 52.73% between H. fomes and H. macrophylla. H. macrophylla showed wide polymorphism in the RAPD marker with H. littoralis (51.23%) and H. fomes (52.73%). Two distinct RAPD products obtained from OPA-10 (1000 bp) and OPD-15 (900 bp) found characteristic molecular markers in H. macrophylla , a species from a non-mangrove habitat. H. macrophylla was more distantly related to H. fomes [genetic distance (1-F) = 0.305] than to H. littoralis [genetic distance (1-F) = 0.273]. H. littoralis was of a closer affinity to H. fomes [genetic distance (1-F) = 0.218] than to H. macrophylla. 相似文献
95.
ABSTRACT. A non-dispersive infrared gas analyser equipped with a Luft-type sonic detector and flow-through reference cell was automated to monitor the total volume of carbon dioxide (CO2) respired by single insects or groups of insects. The infrared analyser was interfaced with an integrator for quantification, a microprocessor to control intermittent air flow through the insect respiration chambers, and a microcomputer for data storage and reduction. This technique has been used to monitor the CO2 Output of diapausing and non-diapausing mature fifth instar larvae and of developing pupae of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae). The resulting data were accurate, quantitative and reproducible. 相似文献
96.
Jean-Marie Delaissé Philippe Martin Marie-Françoise Verheyen-Bouvy Edmond-Jacques Nyns 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,676(1):77-90
The subcellular localization of the ω-hydroxylase of Saccharomycopsis lipolytica was assessed by the analytical fractionation technique, originally described by de Duve C., Pressman, B.C., Gianetto, R., Wattiaux, R. and Appelmans, F., and hitherto little, if at all, applied to yeast. Protoplasts were separated in six fractions by differential centrifugation. Some of these fractions were further fractioned by density gradient centrifugation. The distribution of ω-hydroxylase and 15 other constituents chosen as possible markers of its subcellular membranes has been established. ω-Hydroxylase resulted in being bound to a membrane that containes also cytochrome P-450 and NADPH-cytochrome c reductase. This membrane clearly differs from five other subcellular entities. (1) Mitochondria were characterized by particulate malate dehydrogenase, particulate Antimycin A-insensitive NADH-cytochrome c reductase, oligomycin-sensitive and K+-stimulated ATPase pH 9. (2) Most if not all of the catalase and urate oxidase is peroxisomal. (3) Free ribosomes account for most RNA. (4) Nucleoside diphosphatase is for the first time reported in a yeast and appears to belong to an homogeneous population of small membranes. (5) The soluble compartment contains magnesium pyrophosphatase, alkaline phosphatase, 5′-nucleotidase and part of the NADH-cytochrome c reductase. Latent arylesterase and ATPase pH7 have an unspecific distribution. Alkaline phosphodiesterase I has not been detected. 相似文献
97.
98.
Harry Le Vine Pedro Cuatrecasas 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,672(3):248-261
A cytosolic, macromolecular factor required for the cholera toxin-dependent activation of pigeon erythrocyte adenylate cyclase and cholera toxin-dependent ADP-ribosylation of a membrane-bound 43 000 dalton polypeptide has been purified 1100-fold from horse erythrocyte cytosol using organic solvent precipitation and heat treatment. This factor, 13 000 daltons, does not absorb to anionic or cationic exchange resins, is sensitive to trypsin or 10% trichloroacetic acid and is not extractable by diethyl ether. Activation of adenylate cyclase by cholera toxin requires the simultaneous presence of ATP (including possible trace GTP), NAD+, dithiothreitol, cholera toxin, membranes and the cytosolic macromolecular factor. Reversal of cholera toxin activation of adenylate cyclase, and of the toxin-dependent ADP-ribosylation, requires the presence of the cytosolic factor. The ability of the purified cytosolic factor to influence the hormonal sensitivity of liver membrane adenylate cyclase may provide clues to its physiological functions. 相似文献
99.
100.
CHRISTOPHE GONINDARD CATHERINE GOIGOUX ETIENNE HOLLANDE LUCIEN DUSSOURD D'HINTERLAND 《Pigment cell & melanoma research》1996,9(3):148-153
The injection of α-MSH or of one of its analogues ([Nle4-D.Phe7] α-MSH4–10) reduced, in vivo, the release of two cytokines (IL-1α and TNFα) involved in inflammation. The inflammatory state was induced in BALB/c mice by intraperitoneal injection of a sublethal dose of lipopolysaccharides (LPS). The assay of these cytokines by ELISA showed a reduction of 20% with α-MSH and between 30 and 60% with the α-MSH analogue. The α-MSH or the analogue was administered in one of two ways: intravenously or subcutaneously. The most efficient method seemed to be the subcutaneous one because it improved the activity 10,000 times more than the intravenous method. Moreover, the analogue induced a regression of mortality in the animals treated by the intravenous method. Our results show that α-MSH and one of its analogues inhibit IL-1α and TNFα, and can be used as anti-inflammatory molecules. 相似文献