全文获取类型
收费全文 | 1460篇 |
免费 | 66篇 |
专业分类
1526篇 |
出版年
2022年 | 19篇 |
2021年 | 46篇 |
2020年 | 17篇 |
2019年 | 15篇 |
2018年 | 37篇 |
2017年 | 33篇 |
2016年 | 45篇 |
2015年 | 63篇 |
2014年 | 70篇 |
2013年 | 117篇 |
2012年 | 104篇 |
2011年 | 95篇 |
2010年 | 58篇 |
2009年 | 45篇 |
2008年 | 64篇 |
2007年 | 58篇 |
2006年 | 68篇 |
2005年 | 43篇 |
2004年 | 58篇 |
2003年 | 44篇 |
2002年 | 19篇 |
2001年 | 19篇 |
2000年 | 24篇 |
1999年 | 21篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 20篇 |
1978年 | 7篇 |
1976年 | 12篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 11篇 |
1972年 | 15篇 |
1970年 | 6篇 |
排序方式: 共有1526条查询结果,搜索用时 15 毫秒
111.
We conducted minisatellite-associated sequence amplification (MASA) with an oligo (5' CACCTCTCCACCTGCC 3') based on consensus of 33.15 repeat loci using cDNA from the testis, ovary, spleen, kidney, heart, liver, and lung of water buffalo Bubalus bubalis and uncovered 25 amplicons of six different sizes (1,263, 846/847, 602, 576, 487, and 324 base pairs). These fragments, cloned and sequenced, were found to represent several functional, regulatory, and structural genes. Blast search of all the 25 amplicons showed homologies with 43 transcribing genes across the species. Of these, the 846/847-bp fragment, having homology with the adenylate kinase gene, showed nucleotide changes at six identical places in the ovary and testis. The 1,263; 324; and 487-bp fragments showed homology with the secreted modular calcium binding protein (SMOC-1), leucine-rich repeat neuronal 6A (LRRN6A) mRNA, and human TTTY5 mRNA, respectively. Real-time PCR showed maximum expression of AKL, LRRN6A, and T-cell receptor gamma (TCR-gamma)-like genes in the testis, SMOC-1 in the liver, and the T-cell receptor-like (TCRL) gene in the spleen compared to those used as endogenous control. We construe that these genes have evolved from a common progenitor and conformed to various biological functions during the course of evolution. MASA approach coupled with real-time PCR has potentials to uncover accurate expression of a large number of genes within and across the species circumventing the screening of cDNA library. 相似文献
112.
A virus isolated from turnip in Aligarh, India, which caused mild mosaic, mottling and curling of leaves followed by overall stunting of plants, was characterized as potato virus X (PVX) on the basis of its host range, biological and physical properties, particle morphology, ultrastructural studies, and serological relationship. 相似文献
113.
Vrljic M Garg J Bellmann A Wachi S Freudl R Malecki MJ Sahm H Kozina VJ Eggeling L Saier MH Eggeling L Saier MH 《Journal of molecular microbiology and biotechnology》1999,1(2):327-336
In Corynebacterium glutamicum the LysE carrier protein exhibits the unique function of exporting L-lysine. We here analyze the membrane topology of LysE, a protein of 236 amino acyl residues, using PhoA- and LacZ-fusions. The amino-terminal end of LysE is located in the cytoplasm whereas the carboxy-terminal end is found in the periplasm. Although 6 hydrophobic domains were identified based on hydropathy analyses, only five transmembrane spanning helices appear to be present. The additional hydrophobic segment may dip into the membrane or be surface localized. We show that LysE is a member of a family of proteins found, for example, in Escherichia coil, Bacillus subtilis, Mycobacterium tuberculosis and Helicobacter pylori. This family, which we have designated the LysE family, is distantly related to two additional protein families which we have designated the YahN and CadD families. These three families, the members of which exhibit similar sizes, hydropathy profiles, and sequence motifs comprise the LysE superfamily. Functionally characterized members of the LysE superfamily export L-lysine, cadmium and possibly quarternary amines. We suggest that LysE superfamily members will prove to catalyze export of a variety of biologically important solutes. 相似文献
114.
Shivali Gupta Vandanajay Bhatia Jian-jun Wen Yewen Wu Ming-He Huang Nisha Jain Garg 《Free radical biology & medicine》2009,47(10):1414-1421
In this study, we investigated the role of Trypanosoma cruzi invasion and inflammatory processes in reactive oxygen species (ROS) production in a mouse atrial cardiomyocyte line (HL-1) and primary adult rat ventricular cardiomyocytes. Cardiomyocytes were incubated with T. cruzi (Tc) trypomastigotes, Tc lysate (TcTL), or Tc secreted proteins (TcSP) for 0–72 h, and ROS were measured by amplex red assay. Cardiomyocytes infected by T. cruzi (but not those incubated with TcTL or TcSP) exhibited a linear increase in ROS production for 2–48 h postinfection (max 18-fold increase), which was further enhanced by recombinant cytokines (IL-1β, TNF-α, and IFN-γ). We observed no increase in NADPH oxidase, xanthine oxidase, or myeloperoxidase activity, and specific inhibitors of these enzymes did not block the increased rate of ROS production in infected cardiomyocytes. Instead, the mitochondrial membrane potential was perturbed and resulted in inefficient electron transport chain (ETC) activity and enhanced electron leakage and ROS formation in infected cardiomyocytes. HL-1 rho (ρ) cardiomyocytes lacked a functional ETC and exhibited no increase in ROS formation in response to T. cruzi. Together, these results demonstrate that invasion by T. cruzi and an inflammatory milieu affect mitochondrial integrity and contribute to electron transport chain inefficiency and ROS production in cardiomyocytes. 相似文献
115.
In this paper, we describe a temperature-sensitive mutant of the yeast Saccharomyces cerevisiae (P5-9) which at a restrictive temperature (36 degrees C) shows a pleiotropic defect for transport of many different metabolites. The temperature sensitivity of the mutant is closely related to a reduction in phosphofructokinase activity. This conclusion is based on the following criteria. (i) Both the primary isolate, designated P5-9 (ts [rho-] Ino-), which is an inositol auxotroph and respiration deficient, and a purified derivative, SB4 (ts [rho+] Ino+ ), which is respiration competent and capable of growing in the absence of inositol, are temperature sensitive for growth and ethanol production in media containing glucose or fructose as the sole carbon source. (ii) The respiration-competent derivative SB4 is not temperature sensitive in media containing glycerol or glycerol-pyruvate; glucose inhibits its growth at 36 degrees C in these media. (iii) Assays of glycolytic enzymes in P5-9 and SB4 extracts, prepared from cells incubated for 1 to 2 h at 36 degrees C before harvesting, show selective reduction in phosphofructokinase activity. Analysis of tetrads derived from the cross of mutant and nonmutant haploids indicates that temperature sensitivity for growth is due to a single gene or to two closely linked genes. The biochemical analysis of spores from seven such tetrads revealed a uniform cosegregation of temperature sensitivity for growth and phosphofructokinase activity. Transport and ATP levels were drastically reduced in SB4 cells incubated at 36 degrees C for 1 to 2 h with glucose as the carbon source, but not when glycerol-pyruvate or lactate was the energy source. Therefore, depletion of energy as a result of phosphofructokinase inactivation appears to be the cause of the pleiotropic transport defect observed in the mutant. 相似文献
116.
Present study was conducted on prostaglandin F2alpha (PGF2alpha), oxytocin, (OT), potassium chloride (KCI) and barium chloride (BaCl2) pre-contracted perimetrial uterine strips of dioestrus and pregnant buffaloes to evaluate the tocolytic efficacy of selective beta2 adrenoceptor agonists-albuterol (salbutamol) and terbutaline. Cumulative concentration-response curves of both the beta2 adrenoceptor agonists were constructed and the mean effective concentration (EC50) values determined and compared statistically. Based on the comparative EC50 values in relaxing the pre-contracted uterine strips with different spasmogens, the rank order potency of albuterol was found to be--PGF2alpha > BaCl2 > OT > KCl on uterine strips from dioestrus animals, while OT> BaCl2> PGF2alpha >KCl on the uterine strips of pregnant buffaloes. The rank order potency of terbutaline on uterine strips from dioestrus stage animals was- BaCl2 > OT > KCl > PGF2alpha, while BaCl2 > PGF2alpha > KCl > OT on uterine tissues of pregnant animals. Thus, irrespective of the state of uterus, whether gravid or non-gravid, KCl-depolarized uterine tissues required comparatively higher concentrations of albuterol or terbutaline to produce tocolytic effect. High concentrations of K+ in biophase may have interfered with the beta2 adrenoceptor agonists-induced outward K+ current and hyperpolarization. From the results of present study, it was evident that selective beta2 adrenergic agonists had good tocolytic efficacy on the uterus of buffaloes. Further, indirectly the possibility of existence and activation of K(Ca) channels by selective beta2 adrenoceptor agonists in mediating tocolysis of buffalo myometrium can not be ruled out, however, detailed studies using specific K(Ca) channel blockers are required for characterizing the nature of such channels in buffalo uterus. 相似文献
117.
Guha U Gomes WA Samanta J Gupta M Rice FL Kessler JA 《Development (Cambridge, England)》2004,131(5):1175-1186
The role of target-derived BMP signaling in development of sensory ganglia and the sensory innervation of the skin was examined in transgenic animals that overexpress either the BMP inhibitor noggin or BMP4 under the control of a keratin 14 (K14) promoter. Overexpression of noggin resulted in a significant increase in the number of neurons in the trigeminal and dorsal root ganglia. Conversely, overexpression of BMP4 resulted in a significant decrease in the number of dorsal root ganglion neurons. There was no significant change in proliferation of trigeminal ganglion neurons in the noggin transgenic animals, and neuron numbers did not undergo the normal developmental decrease between E12.5 and the adult, suggesting that programmed cell death was decreased in these animals. The increase in neuron numbers in the K14-noggin animals was followed by an extraordinary increase in the density of innervation in the skin and a marked change in the pattern of innervation by different types of fibers. Conversely, the density of innervation of the skin was decreased in the BMP4 overexpressing animals. Further Merkel cells and their innervation were increased in the K14-noggin mice and decreased in the K14-BMP4 mice. The changes in neuron numbers and the density of innervation were not accompanied by a change in the levels of neurotrophins in the skin. These findings indicate that the normal developmental decrease in neuron numbers in sensory ganglia depends upon BMP signaling, and that BMPs may limit both the final neuron number in sensory ganglia as well as the extent of innervation of targets. Coupled with prior observations, this suggests that BMP signaling may regulate the acquisition of dependence of neurons on neurotrophins for survival, as well as their dependence on target-derived neurotrophins for determining the density of innervation of the target. 相似文献
118.
N. Kumar A.K. Garg R.S. Dass V.K. Chaturvedi V. Mudgal V.P. Varshney 《Animal Feed Science and Technology》2009,153(1-2):77-87
To investigate and compare the effect of inorganic and organic Se supplementation, 18 male lambs (24.68 ± 2.89 kg mean body weight, about 8–9 months of age) were divided into three groups of six animals in each, following randomized block design. While animals in the control group (Gr I) were fed a standard TMR containing 195 g/kg crushed maize grain, 175.5 g/kg soybean meal, 260 g/kg wheat bran, 13 g/kg mineral mixture (without Se), 6.5 g/kg common salt and 350 g/kg wheat straw, animals in Gr II and Gr III were additionally supplemented with 0.15 mg Se/kg of diet through sodium selenite (inorganic Se) and Jevsel-101 (organic Se), respectively. Experimental feeding was done for a period of 90 days. To assess the humoral immune response, all the lambs were intramuscularly inoculated with a single dose (2 mL) of Haemorrhagic septicaemia oil adjuvant vaccine on day 0; and blood samples were collected on day 0, 30, 60 and 90. Supplementation of Se had no effect on serum total cholesterol, total protein, albumin, globulin, albumin:globulin ratio, T3, T4, T4:T3 ratio; serum Ca and P levels and SGOT and SGPT activity. However, there was a significant increase in the serum Se level, RBC GSH-Px activity and humoral immune response in both the Se supplemented groups as compared to control group. Average daily gain (g) was highest (110) in Gr III, followed by Gr II (98.2) and lowest in Gr I (89.1). Thus, supplementation of organic as well as inorganic Se was found to improve the growth rate, humoral immune response and antioxidant status of the lambs; and between two sources, organic Se was more effective than inorganic Se. 相似文献
119.
Plasmodium falciparum alanine M1-aminopeptidase (PfA-M1) is a validated target for anti-malarial drug development. Presence ofsignificant similarity between PfA-M1 and human M1-aminopeptidases, particularly within regions of enzyme active site leads toproblem of non-specificity and off-target binding for known aminopeptidase inhibitors. Molecular docking based in silico screeningapproach for off-target binding has high potential but requires 3D-structure of all human M1-aminopeptidaes. Therefore, in thepresent study 3D structural models of seven human M1-aminopeptidases were developed. The robustness of docking parametersand quality of predicted human M1-aminopeptidases structural models was evaluated by stereochemical analysis and docking oftheir respective known inhibitors. The docking scores were in agreement with the inhibitory concentrations elucidated in enzymeassays of respective inhibitor enzyme combinations (r2≈0.70). Further docking analysis of fifteen potential PfA-M1 inhibitors(virtual screening identified) showed that three compounds had less docking affinity for human M1-aminopeptidases as comparedto PfA-M1. These three identified potential lead compounds can be validated with enzyme assays and used as a scaffold fordesigning of new compounds with increased specificity towards PfA-M1. 相似文献
120.
Jianzhong Huang Wandee Yindeeyoungyeon Ram P. Garg Timothy P. Denny Mark A. Schell 《Journal of bacteriology》1998,180(10):2736-2743