全文获取类型
收费全文 | 11561篇 |
免费 | 922篇 |
国内免费 | 8篇 |
出版年
2023年 | 66篇 |
2022年 | 147篇 |
2021年 | 255篇 |
2020年 | 138篇 |
2019年 | 167篇 |
2018年 | 251篇 |
2017年 | 208篇 |
2016年 | 329篇 |
2015年 | 494篇 |
2014年 | 530篇 |
2013年 | 659篇 |
2012年 | 792篇 |
2011年 | 771篇 |
2010年 | 485篇 |
2009年 | 452篇 |
2008年 | 616篇 |
2007年 | 662篇 |
2006年 | 560篇 |
2005年 | 535篇 |
2004年 | 465篇 |
2003年 | 457篇 |
2002年 | 430篇 |
2001年 | 222篇 |
2000年 | 196篇 |
1999年 | 194篇 |
1998年 | 135篇 |
1997年 | 127篇 |
1996年 | 89篇 |
1995年 | 88篇 |
1994年 | 80篇 |
1993年 | 74篇 |
1992年 | 123篇 |
1991年 | 102篇 |
1990年 | 113篇 |
1989年 | 88篇 |
1988年 | 96篇 |
1987年 | 72篇 |
1986年 | 79篇 |
1985年 | 85篇 |
1984年 | 80篇 |
1983年 | 55篇 |
1982年 | 61篇 |
1981年 | 45篇 |
1980年 | 51篇 |
1979年 | 72篇 |
1978年 | 55篇 |
1977年 | 46篇 |
1975年 | 47篇 |
1974年 | 58篇 |
1973年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
H G Fischer S Frosch K Reske A B Reske-Kunz 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(11):3882-3888
The effects of granulocyte-macrophage (GM)-CSF on the synthesis of MHC class II molecules and on the Ag presentation capacity by bone marrow derived macrophages (BMM phi) was investigated. BMM phi obtained by in vitro culture in the presence of macrophage-CSF were negative for synthesis of I-A molecules and induced the Ag-mediated proliferation of insulin-specific T clone cells with lower efficiency than splenic accessory cells. After pulse treatment with GM-CSF for 24 to 48 h, day 12 BMM phi exhibited highly efficient Ag presentation function which was superior to that induced by IFN-gamma. Expression of membrane-bound IL-1 was augmented significantly by GM-CSF, but not by IFN-gamma. However, the T cell clone used to probe for accessory cell function of BMM phi was not dependent on IL-1 for optimal proliferation. Concomitantly, GM-CSF induced the de novo synthesis of I-A molecules, although to a lesser extent than optimal doses of IFN-gamma. Thus GM-CSF appears to elicit properties in addition to Ia molecule synthesis and membrane IL-1 expression in BMM phi being essential for efficient accessory cell function to the T clone cells. The activation of BMM phi by GM-CSF was reversible and could be repeated. These data show that GM-CSF exerts a modulatory influence on preformed BMM phi, reversibly activating cells to Ia biosynthetic potential and pronounced accessory cell capacity, thus rendering the explanation unlikely that differentiation of precursor cells into a constitutively functional state had occurred. 相似文献
52.
D Emilie C Wallon P Galanaud A Fischer D Olive J F Delfraissy 《Journal of immunology (Baltimore, Md. : 1950)》1988,141(6):1912-1918
We examined the role of the lymphocyte function-associated (LFA)3 molecule in human B cell response. A mAb to this molecule did not influence B cell proliferation induced by anti-mu antibody and IL. In contrast, the same mAb inhibited the specific T-dependent B cell response induced by a particulate Ag. In the same line, two anti-CD2 mAb (directed toward the T11-1 and T11-2 epitopes) inhibited this response, whether used alone or in association. These inhibitions took place at an early stage of the response, and anti-LFA3 and anti-CD2 mAb acted on B cells and T cells, respectively. In contrast, when T cell help was provided by exogenous IL-2, the B cell response was resistant to the inhibitory effect of anti-LFA3 mAb. Taken together, these results indicate that the LFA3-CD2 pair play a major role in the direct T-B interaction required for T cell help. 相似文献
53.
Assessment of arterial-venous differences across transplanted methylcholanthrene-induced sarcomas in rats revealed significant decreases in plasma concentrations of glutamine, serine and glucose. Treatment with the glutamine antimetabolite, acivicin, significantly reduced tumor weights by 65% at the conclusion of the experiment 34 days after tumor induction. These results suggest that glutamine is an essential metabolic substrate for tumor growth and that blockade of glutamine utilization can inhibit the growth of these transplantable sarcomas. 相似文献
54.
Giovanni Bernardini Pio Belgiojoso Marina Camatini 《Molecular reproduction and development》1988,21(4):403-408
The motility status of Xenopus laevis spermatozoa does not affect their respiration rate. Oxygen consumption for 109 spermatozoa is approximately 0.4 μmol/minute. Oxygen consumption is not increased by gramicidin D, an uncoupler, and it is not blocked by KCN or NaN3. The adenosine triphosphate (ATP) content of spermatozoa that have been activated is definitely less than that in the spermatozoa that remained immotile. Incubation in KCN, NaN3, and gramicidin decreases the ATP content and impairs motility. The conclusions of the present study are that in Xenopus spermatozoa motility and oxygen consumption are not correlated, and the composition of the respiratory chain of these spermatozoa presents noteworthy peculiarities. 相似文献
55.
A total storage protein fraction was prepared from mustard (Sinapis alba L.) seeds via isolated protein bodies and characterized by sedimentation, immunological, and electrophoretic techniques. Mustard seed storage protein consists of three fractions (1) a “legumin-like” 13-S complex composed of two pairs of disulfide-linked polypeptides (16.5 + 28.5 kDa and 19.5 + 34 kDa, respectively) and two single polypeptides (18 kDa and 26 kDa), (2) a “vicilin-like” 9-S complex composed of two glycoproteins (64 kDa and 77 kDa), and (3) two small polypeptides (10 kDa and 11 kDa) which probably represent the 1.7-S complex found in other Cruciferae. In contrast to related species, no glycosylated polypeptide was found in the 13-S complex. Immunological relationships were found between the paired polypeptides of the 13-S complex but not between polypeptides of the 13-S complex and polypeptides of the 9-S complex. Pulse-chase labeling and in vitro translation of polysomal RNA from young embryos demonstrated that the polypeptides of the 13-S complex originate from high molecular mass precursors, except for the 18 kDa polypeptide which appears to be synthesized in its final size. The amino-acid composition of the major polypeptides of the mustard storage protein is given. 相似文献
56.
Fast one-step procedure for the detection of nucleic acids in situ by primer-induced sequence-specific labeling with fluorescein-12-dUTP. 总被引:5,自引:0,他引:5
J Koch J Mogensen S Pedersen H Fischer J Hindkjaer S K?lvraa L Bolund 《Cytogenetics and cell genetics》1992,60(1):1-3
We provide fast, simple, one-step procedures for sequence-specific detection of nucleic acids in situ. Tandem repeat sequences in DNA are stained within 30 min, and mRNA is stained within 2 h. The procedures are based on the incorporation of the newly available fluorescein-labeled dUTP into DNA synthesized in situ by primed in situ labeling, with denatured fragments of cloned DNA or oligonucleotides as primers. The extreme speed and simplicity of the reaction make it attractive for automatization in routine laboratory procedures and opens up new diagnostic possibilities. 相似文献
57.
Thiobacillus tepidarius (type strain) was grown in microaerophilic conditions, on tetrathionate, thiosulfate or crystalline So. The rates of tetrathionate, thiosulfate, elemental sulfur (So) and sulfite oxidation of the different cultures were measured respirometrically, using exponentially growing cells, with an oxygen electrode. Cells growing on the three different sulfur compounds retain thiosulfate-, tetrathionate, and So-oxidizing activities (SOA), but lack respiratory sulfite-oxidizing activity. The SOA for all the cultures was almost totally inhibited by 50 M myxothiazol, an inhibitor of the quinone-cytochrome b region, and by 10 M of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). Tetrathionate- and thiosulfate-oxidizing activities were moderately and weakly inhibited by 50 M totally inhibited (>95%) all respiratory activities. This study suggests that electrons released by So oxidation enter the respiratory chain in the quinone-cytochrome b region.Abbreviation SOA
sulfur-oxidizing activity 相似文献
58.
59.
Andrej Anokhin Ortrud Steinlein Christine Fischer Yiping Mao Peter Vogt Edda Schalt Friedrich Vogel 《Human genetics》1992,90(1-2):99-112
Summary The studied phenotype, the low-voltage electroencephalogram (LVEEG), is characterized by the absence of an alpha rhythm from the resting EEG. In previous studies, evidence was found for a simple autosomal-dominant mode of inheritance of the LVEEG. Such a polymorphism in brain function can be used as a research model for the stepwise elucidation of the molecular mechanism involved in those aspects of neuronal activity that are reflected in the EEG. Linkage with the variable number of tandem repeats (VNTR) marker CMM6 (D20S19) and localization of an LVEEG (EEGV1) gene on 20q have previously been reported, and genetic heterogeneity has been demonstrated. This latter result has been corroborated by studing new marker (MS214). The phenotype of the LVEEG is described here in greater detail. Its main characteristic is the absence of rhythmic alpha activity, especially in occipital leads, whereas other wave forms such as beta or theta waves may be present. Analysis of 17 new families (some of them large), together with 60 previously described nuclear families, supports the genetic hypothesis of an autosomal-dominant mode of inheritance. Problems connected with the analysis of linkage heterogeneity, exclusion mapping, and the study of multipoint linkage are discussed. A possible explanation of the localization of LVEEG in the close vicinity of another gene influencing synchronization of the normal EEG, the gene for benign neonatal epilepsie, is given. 相似文献
60.
Giuseppe Ravizzola Gabriele Pinsi Marina Cesana Carmela De Rango Laura Peroni Prof. Adolfo Turano 《Current microbiology》1992,24(6):349-353
The protective effects of rufloxacin againstStaphylococcus aureus-induced infections were compared with those of ciprofloxacin in the granuloma pouch model in the rat. Two strains with different in vitro sensitivity to the drugs were studied. Rufloxacin concentrations persisted longer than ciprofloxacin in the exudate in the pouch cavity and were about eight times higher. Equal doses of rufloxacin and ciprofloxacin had similar antibacterial activities. However, rufloxacin inhibitedStaphylococcus aureus bacterial growth significantly longer than did ciprofloxacin. 相似文献