全文获取类型
收费全文 | 394542篇 |
免费 | 45391篇 |
国内免费 | 360篇 |
专业分类
440293篇 |
出版年
2016年 | 3565篇 |
2015年 | 5342篇 |
2014年 | 6231篇 |
2013年 | 8958篇 |
2012年 | 9938篇 |
2011年 | 10008篇 |
2010年 | 6659篇 |
2009年 | 6289篇 |
2008年 | 8901篇 |
2007年 | 9386篇 |
2006年 | 8927篇 |
2005年 | 8688篇 |
2004年 | 8612篇 |
2003年 | 8208篇 |
2002年 | 8205篇 |
2001年 | 18198篇 |
2000年 | 18753篇 |
1999年 | 14890篇 |
1998年 | 4899篇 |
1997年 | 5159篇 |
1996年 | 4809篇 |
1995年 | 4612篇 |
1994年 | 4549篇 |
1993年 | 4550篇 |
1992年 | 12057篇 |
1991年 | 11644篇 |
1990年 | 11304篇 |
1989年 | 10957篇 |
1988年 | 10342篇 |
1987年 | 9865篇 |
1986年 | 9371篇 |
1985年 | 9458篇 |
1984年 | 7812篇 |
1983年 | 6719篇 |
1982年 | 5347篇 |
1981年 | 4980篇 |
1980年 | 4520篇 |
1979年 | 7626篇 |
1978年 | 6157篇 |
1977年 | 5654篇 |
1976年 | 5339篇 |
1975年 | 5999篇 |
1974年 | 6626篇 |
1973年 | 6571篇 |
1972年 | 6086篇 |
1971年 | 5509篇 |
1970年 | 4757篇 |
1969年 | 4718篇 |
1968年 | 4300篇 |
1967年 | 3616篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
751.
Fluorescence polarization, P, of 1,6-diphenyl-1,3,5-hexatriene was studied in Escherichia coli B/r. Modification of nutritional conditions was not compensated by homeoviscous adaptation, demonstrated to exist for temperature variations. Cell diameter, which is known also to vary with nutrition but not with temperature, was found to be positively correlated with 1/P, and may therefore be regulated by membrane lipid order and fluidity. 相似文献
752.
Monica BreurkenEdith H.M. Lempens Rinske P. TemmingBrett A. Helms E.W. MeijerMaarten Merkx 《Bioorganic & medicinal chemistry》2011,19(3):1062-1071
Collagen is an attractive marker for tissue remodeling in a variety of common disease processes. Here we report the preparation of protein dendrimers as multivalent collagen targeting ligands by native chemical ligation of the collagen binding protein CNA35 to cysteine-functionalized dendritic divalent (AB2) and tetravalent (AB4) wedges. The binding of these multivalent protein constructs was studied on collagen-immobilized chip surfaces as well as to native collagen in rat intestinal tissues. To understand the importance of target density we also created collagen-mimicking surfaces by immobilizing synthetic collagen triple helical peptides at various densities on a chip surface. Multivalent display of a weak-binding variant (CNA35-Y175K) resulted in a large increase in collagen affinity, effectively restoring the collagen imaging capacities for the AB4 system. In addition, dissociation of these multivalent CNA35 dendrimers from collagen surfaces was found to be strongly attenuated. 相似文献
753.
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
754.
755.
Calorimetric properties of mixtures of ganglioside GM1 and dipalmitoylphosphatidylcholine 总被引:2,自引:0,他引:2
L O Sillerud D E Schafer R K Yu W H Konigsberg 《The Journal of biological chemistry》1979,254(21):10876-10880
756.
757.
R H Mole 《BMJ (Clinical research ed.)》1986,293(6552):953-954
758.
The beta subunits of equine lutropin and equine chorionic gonadotropin were incubated in 0.013 N HCl for 30 min at 110 degrees C and separated into two fragments by reverse-phase high performance liquid chromatography. The amino acid and carbohydrate compositions of both fragments from each subunit were analyzed. The results demonstrated that equine lutropin-beta has a glycosylated COOH-terminal extension that differs only in carbohydrate composition from the COOH-terminal portion of equine chorionic gonadotropin-beta. This is the first demonstration of a glycosylated COOH-terminal extension in a pituitary glycoprotein hormone. 相似文献
759.
O W Petersen P E H?yer J Hilgers P Briand B van Deurs 《Virchows Archiv. B, Cell pathology including molecular pathology》1985,50(1):27-42
Epithelial cell islets in primary monolayer cultures of human breast biopsies were characterized by combined immuno-, enzyme- and DNA cytochemistry as well as by analysis of attachment-, spread- and growth patterns. For cultivation we used explants from reduction mammoplasties, benign lesions, primary carcinomas and metastases. Milk fat globule membrane antigen (MFGM-A) was detected with a monoclonal antibody, and the tetrazolium reaction for glucose 6-phosphate dehydrogenase (G6PDH) as well as DNA content of the cultured cells were quantified. Spreading and growth of individual islets were studied by image analysis. Fibroblast-like cells did not express MFGM-A, and whereas epithelial (MFGM-A positive) cell islets of normal and benign origin showed cells with no or low G6PDH reaction, respectively, the majority of epithelial cell islets from 11 out of 21 carcinomas showed strong reaction. Cell islets with strong G6PDH reaction were sometimes hyperdiploid. Moreover, whereas cell islets with no or low reaction from both benign lesions and carcinomas readily attached and spread in a serum-free medium and showed population doubling times of 30 to 110 h, cell islets with strong reaction from carcinomas and metastatic lesions required serum for attachment and their growth rate was too low to be determined. 相似文献
760.
K H?kkinen M Alén P V Komi 《European journal of applied physiology and occupational physiology》1984,53(2):97-105
Various aspects of neuromuscular, anaerobic, and aerobic performance capacity were investigated in four powerlifters, seven bodybuilders, and three wrestlers with a history of specific training for several years. The data (means +/- SD) showed that the three subject groups possessed similar values for maximal isometric force per unit bodyweight (50.7 +/- 9.6, 49.3 +/- 4.1, and 49.3 +/- 10.9 N/kg, respectively). However, significant (P less than 0.05) differences were observed in the times for isometric force production, so that e.g., times to produce a 30% force level were shorter for the wrestlers and bodybuilders (28.3 +/- 3.1 and 26.4 +/- 6.6 ms) than that (53.3 +/- 23.7 ms) for the powerlifters. Utilization of elastic energy by the wrestlers was significantly (P less than 0.05) better than that of the other two subject groups, as judged from differences between the counter-movement and squat jumps at 0, 40, and 100 kg's loads. No differences were observed between the groups in anaerobic power in a 1-min maximal test, but the values for VO2 max were higher (P less than 0.05) among the wrestlers and bodybuilders (57.8 +/- 6.6 and 50.8 +/- 6.8 ml X kg-1 X min-1) as compared to the powerlifters (41.9 +/- 7.2 ml X kg-1 X min-1). Within the limitations of the subject sample, no differences of a statistical significancy were observed between the groups in fibre distribution, fibre areas, or the area ratio of fast (FT) and slow (ST) twitch fibres in vastus lateralis.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献