全文获取类型
收费全文 | 737篇 |
免费 | 59篇 |
国内免费 | 1篇 |
专业分类
797篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 16篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 36篇 |
2015年 | 37篇 |
2014年 | 28篇 |
2013年 | 46篇 |
2012年 | 57篇 |
2011年 | 56篇 |
2010年 | 33篇 |
2009年 | 26篇 |
2008年 | 48篇 |
2007年 | 37篇 |
2006年 | 40篇 |
2005年 | 16篇 |
2004年 | 22篇 |
2003年 | 20篇 |
2002年 | 21篇 |
2001年 | 7篇 |
2000年 | 25篇 |
1999年 | 12篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1971年 | 5篇 |
1970年 | 2篇 |
1968年 | 3篇 |
1967年 | 4篇 |
排序方式: 共有797条查询结果,搜索用时 6 毫秒
51.
Petr Novák Lukáš Žídek Veronika Motáčková Petr Padrta Alžběta Švenková Jean-Marc Nuzillard Libor Krásný Vladimír Sklenář 《Journal of biomolecular NMR》2010,46(2):191-197
S3EPY is a Python extension to the program Sparky written to facilitate the assessment of coupling constants from in-phase/antiphase
and spin-state-selective excitation (S3E) experiments. It enables the routine use of small scalar couplings by automating the coupling evaluation procedure. S3EPY
provides an integrated graphical user interface to programs which outputs graphs and the table of determined couplings. 相似文献
52.
Hannan NJ Stephens AN Rainczuk A Hincks C Rombauts LJ Salamonsen LA 《Journal of proteome research》2010,9(12):6256-6264
Endometrial secretions in the uterine cavity contain mediators important for endometrial receptivity and embryo implantation. Unbiased analysis of uterine fluid from a receptive versus nonreceptive time of the menstrual cycle and in fertile and infertile women will provide new insights into uterine receptivity. We hypothesized that proteomic analysis of human uterine lavages would identify proteins important for the establishment of pregnancy in humans. Lavages collected from fertile (n = 7) and infertile (n = 8) women during the midsecretory (MS) phase, and from fertile women during the midproliferative (MP) (n = 7) phase, were assessed using 2D-differential in gel electrophoresis (2D-DiGE) over a pI 4-7 range. Statistical analysis revealed 7 spots that were significantly decreased in the MP compared to the MS phase, while 18 spots showed differential expression between fertile and infertile women. A number of proteins were identified by mass spectrometry, including antithrombin III and alpha-2-macroglobulin, whose production was confirmed in endometrial epithelium. Their staining pattern suggests roles during embryo implantation. Assessment of the human endometrial secretome has identified differences in the protein content of uterine fluid with respect to receptivity and fertility. 相似文献
53.
Spíchal L Krystof V Paprskárová M Lenobel R Styskala J Binarová P Cenklová V De Veylder L Inzé D Kontopidis G Fischer PM Schmülling T Strnad M 《The Journal of biological chemistry》2007,282(19):14356-14363
Cytokinins are a class of plant hormones that regulate the cell cycle and diverse developmental and physiological processes. Several compounds have been identified that antagonize the effects of cytokinins. Based on structural similarities and competitive inhibition, it has been assumed that these anticytokinins act through a common cellular target, namely the cytokinin receptor. Here, we examined directly the possibility that various representative classical anticytokinins inhibit the Arabidopsis cytokinin receptors CRE1/AHK4 (cytokinin response 1/Arabidopsis histidine kinase 4) and AHK3 (Arabidopsis histidine kinase 3). We show that pyrrolo[2,3-d]pyrimidine and pyrazolo[4,3-d]pyrimidine anticytokinins do not act as competitors of cytokinins at the receptor level. Flow cytometry and microscopic analyses revealed that anticytokinins inhibit the cell cycle and cause disorganization of the microtubular cytoskeleton and apoptosis. This is consistent with the hypothesis that they inhibit regulatory cyclin-dependent kinase (CDK) enzymes. Biochemical studies demonstrated inhibition by selected anti-cytokinins of both Arabidopsis and human CDKs. X-ray determination of the crystal structure of a human CDK2-anticytokinin complex demonstrated that the antagonist occupies the ATP-binding site of CDK2. Finally, treatment of human cancer cell lines with anticytokinins demonstrated their ability to kill human cells with similar effectiveness as known CDK inhibitors. 相似文献
54.
Bendlová B Zavadilová J Vanková M Vejrazková D Lukásová P Vcelák J Hill M Cibula D Vondra K Stárka L Vrbíková J 《The Journal of steroid biochemistry and molecular biology》2007,104(1-2):68-74
SHBG (sex hormone-binding globulin) is a transport protein specific for dihydrotestosterone, testosterone and estradiol. The missense mutation in exon 8 (GAC-->AAC) causing the amino acid exchange Asp-->Asn in codon 327 (D327N) correlates according to the published data with increased SHBG levels. We studied possible association of this polymorphism with polycystic ovary syndrome (PCOS) and anthropometric and biochemical parameters in 248 PCOS patients and 109 healthy control women. The D327N polymorphism (wild-type and variant allele) was detected using PCR-RFLP method (restriction enzyme Bbs-I). For statistical evaluation chi(2) test, Mann-Whitney test, ANCOVA, ANOVA (NCSS 2004, Statgraphics Plus v.5.1, USA) were used. There was no significant difference in genotype distribution between PCOS and controls (chi(2)=1.03, p=0.59). Moreover, we did not find an association of the variant allele with plasma SHBG level, steroid hormones, or screened parameters of lipid and glucose metabolism. In conclusion, the D327N polymorphism of the SHBG gene does not influence susceptibility to PCOS. 相似文献
55.
Říha Milan Rabaneda-Bueno Ruben Jarić Ivan Souza Allan T. Vejřík Lukáš Draštík Vladislav Blabolil Petr Holubová Michaela Jůza Tomas Gjelland Karl Ø. Rychtecký Pavel Sajdlová Zuzana Kočvara Luboš Tušer Michal Prchalová Marie Seďa Jaromír Peterka Jiří 《Hydrobiologia》2022,849(15):3351-3371
Hydrobiologia - To understand the spatiotemporal overlap in the habitat use of sympatric predators, we studied longitudinal activity and reservoir section and depth use of pike (Esox lucius),... 相似文献
56.
57.
Michail Rovatsos Jasna Vuki? Petros Lymberakis Luká? Kratochvíl 《Proceedings. Biological sciences / The Royal Society》2015,282(1821)
Amniote vertebrates possess various mechanisms of sex determination, but their variability is not equally distributed. The large evolutionary stability of sex chromosomes in viviparous mammals and birds was believed to be connected with their endothermy. However, some ectotherm lineages seem to be comparably conserved in sex determination, but previously there was a lack of molecular evidence to confirm this. Here, we document a stability of sex chromosomes in advanced snakes based on the testing of Z-specificity of genes using quantitative PCR (qPCR) across 37 snake species (our qPCR technique is suitable for molecular sexing in potentially all advanced snakes). We discovered that at least part of sex chromosomes is homologous across all families of caenophidian snakes (Acrochordidae, Xenodermatidae, Pareatidae, Viperidae, Homalopsidae, Colubridae, Elapidae and Lamprophiidae). The emergence of differentiated sex chromosomes can be dated back to about 60 Ma and preceded the extensive diversification of advanced snakes, the group with more than 3000 species. The Z-specific genes of caenophidian snakes are (pseudo)autosomal in the members of the snake families Pythonidae, Xenopeltidae, Boidae, Erycidae and Sanziniidae, as well as in outgroups with differentiated sex chromosomes such as monitor lizards, iguanas and chameleons. Along with iguanas, advanced snakes are therefore another example of ectothermic amniotes with a long-term stability of sex chromosomes comparable with endotherms. 相似文献
58.
The main goal of this research was to investigate how different factors influence membrane fouling. The impact of the different concentrations of activated sludge and the amount of extracellular polymer substances (EPS) were monitored. Two pilot plants with submerged membrane modules (hollow fiber and flat sheet) were operated and the raw wastewater was used.Humic substances were identified as the major components of EPS in the activated sludge (more than 34%) in both pilot plants. As the basic constituent in permeate, humic substances were identified as the most dominant components in the effluent (61%) in both pilot plants. Conversely, proteins were mostly analyzed in permeate and supernatant below the detection limit. The total amount of EPS [mg g−1 (VSS)] was similar for concentrations of activated sludge 6, 10 and 14 g L−1. Carbohydrates were identified as the component of EPS which tends most to clog membranes. 相似文献
59.
Mik V Szüčová L Spíchal L Plíhal O Nisler J Zahajská L Doležal K Strnad M 《Bioorganic & medicinal chemistry》2011,19(23):7244-7251
Rational design is one of the latest ways how to evaluate particular activity of signal molecules, for example cytokinin derivatives. A series of N(6)-[(3-methylbut-2-en-1-yl)amino]purine (iP) derivatives specifically substituted at the N9 atom of purine moiety by tetrahydropyran-2-yl, ethoxyethyl, and C2-C4 alkyl chains terminated by various functional groups were prepared. The reason for this rational design was to reveal the relationship between specific substitution at the N9 atom of purine moiety of iP and cytokinin activity of the prepared compounds. The synthesis was carried out either via 6-chloro-9-substituted intermediates prepared originally from 6-chloropurine, or by a direct alkylation of N9 atom of N(6)-[(3-methylbut-2-en-1-yl)amino]purine. Selective reduction was implemented in the preparation of compound N(6)-[(3-methylbut-2-en-1-yl)amino]-9-(2-aminoethyl-amino)purine (12) when 6-[(3-methylbut-2-en-1-yl)amino]-9-(2-azidoethyl)purine (7) was reduced by zinc powder in mild conditions. The prepared derivatives were characterized by C, H, N elemental analyses, thin layer chromatography (TLC), high performance liquid chromatography (HPLC), melting point determinations (mp), CI+ mass spectral measurement (CI+ MS), and by (1)H NMR spectroscopy. Biological activity of prepared compounds was assessed in three in vitro cytokinin bioassays (tobacco callus, wheat leaf senescence, and Amaranthus bioassay). Moreover, the perception of prepared derivatives by cytokinin-sensitive receptor CRE1/AHK4 from Arabidopsis thaliana, as well as by the receptors ZmHK1 and ZmHK3a from Zea mays, was studied in a bacterial assay where the response to the cytokinin treatment could be specifically quantified with the aim to reveal the way of the perception of the above mentioned derivatives in two different plant species, that is, Arabidopsis, a model dicot, and maize, a model monocot. The majority of cytokinin derivatives were significantly active in both Amaranthus as well as in tobacco callus bioassay and almost inactive in detached wheat leaf senescence assay. N9-Substituted iP derivatives remained active in both in vitro bioassays in a broad range of concentrations despite the fact that most of the derivatives were unable to trigger the cytokinin response in CRE1/AHK4 and ZmHK1 receptors. However, several derivatives induced low but detectable cytokinin-like activation in maize ZmHK3a receptor. Compound 6-[(3-methylbut-2-en-1-yl)amino]-9-(tetrahydropyran-2-yl)purine (1) was also recognized by CRE1/AHK4 at high concentration ≥ 50 μM. 相似文献
60.