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1.
Cholecystokinin (CCK )isa polypeptidehor monecontaining 33aminoacidsresiduewithgastroin testinal,biliarandbrainactivities Itiswidelydis tributedinthevertebratecentralnervoussystem ,anditcanstimulateextensivelytheliberationofinsulinandglucagonfromtheLangerhansislets GreateffortshavebeendevotedtothesynthesisofCCK 8,itsderivativesandanalogues Amongthedifferentmethods ,theenzymaticmethodisthemosteffectiveonewithmanyadvantagesoverconventionalchemicalmethodologies :enzymespecificitysuppress essid… 相似文献
2.
M.W. DAVEY H. ROMMELAERE S. DE BOECK M. GOETHALS J. VAN DAMME J. VANDEKERCKHOVE 《Chemical biology & drug design》1995,45(4):380-385
Salmon calcitonin, CT(1-32)·NH2, was synthesised by the trypsin-mediated coupling of the peptide fragments CT(1-24) and CT(25-32)·NH2, prepared by conventional Fmoc solid-phase chemistry. Optimal conditions regarding reaction time course, pH, proportion of catalyst, substrate concentration and composition of the reaction medium were determined from initial studies on the coupling of CT(1-11) to CT(12-24) and of CT(12-24) to CT(25-32)·NH2. For the final successful semisynthesis, we found that it was unnecessary to protect lysine residues not involved in the coupling, and that secondary hydrolysis at these sites could be prevented by increasing the pH of the reaction medium. The reaction achieved equilibrium after 30-45 min, with overall conversion of around 30% of the initial amount of CT(1-24) substrate into product. Yields were depressed due to cyclisation of the CT(1-24) substrate via air-oxidation of the Cys1 and Cys7 residues. 相似文献
3.
张瑞生 《南京军医学院学报》2003,25(4):241-242
目的:应用血清1,5-脱水葡糖醇(1,5AG)的酶动力学法,探讨其在糖尿病诊断中的应用价值。方法:应用全自动生化分析仪,采用全酶法测定健康人和糖尿病患者血清1,5AG的含量。结果:该法测定血清1,5AG精密度好,高、低值混合血清的CV分别为1.47%和1.70%;回收率分别为98.28%、101.32%和97.64%、103.36%,平均回收率为100.15%;在1,5-AG浓度为360μmol/L内呈良好的线性;60例糖尿患者血清1,5AG(5.38-59.54μmol/L)明显低于健康人(60.89~269.79μmol/L),P<0.01。结论:该方法重复性好,准确度高,工作试剂在2 d内稳定,适合常规实验室开展;血清1,5AG测定有助于糖尿病的诊断和治疗过程的监控。 相似文献
4.
以D311离子交换树脂为载体,通过离子交换吸附法对Lipolase100L脂肪酶进行了固定化。采用考马斯亮蓝法测定了酶蛋白在离子交换树脂上的吸附率,考察并得到了酶固定化的最佳条件:在pH10缓冲液下,加酶液量为每克预处理过的树脂加入1.5mL,吸附时间为10h,吸附温度为35℃。所得固定化酶用于催化合成月桂酸月桂醇酯,在反应物质的量比为1∶1时,水质量分数为8%,在50mL异辛烷有机溶剂中固定化酶用量为200mg,反应时间为210min,温度为55℃的最佳条件下,酯化率可达91.3%。 相似文献
5.
In spite of significant efforts in academic and commercial laboratories, major breakthroughs in oral peptide and protein formulation have not been achieved. The major barriers to developing oral formulations for peptides and proteins include poor intrinsic permeability, lumenal and cellular enzymatic degradation, rapid clearance, and chemical and conformational stability. Pharmaceutical approaches to address these barriers, which have been successful with traditional, small, organic drug molecules, have not readily translated into effective peptide and protein formulations. The success achieved by Sandoz with cyclosporin formulations remains one clear example of what can be achieved, although it is likely that effective oral formulations for peptides and proteins will remain highly compound specific. Although the challenges are significant, the potential therapeutic benefit remains high, particularly with the increasing identification of potential peptide and protein drug candidates emerging from the biotechnology arena. Successful formulations will most likely require a systematic and careful merger of formulation and design delivery systems which maximize the potential for absorption across the epithelial cell layer. 相似文献
6.
Problems associated with the use of 5-iodo-2-deoxyundine (IDU) in the treatment of herpes simplex keratitis can be attributed largely to the polar nature of IDU resulting in its poor permeability across the lipoidal epithelial layer of the corneal membrane. Five aliphatic 5-esters of IDU were synthesized and evaluated as prodrugs for potential use in the treatment of deep ocular infections such as stromal keratitis, iritis, and even retinitis. A parabolic relationship between in vitro corneal membrane permeability and carbon chain length of prodrugs is evident. For a given prodrug, enzymatic hydrolysis proceeded most readily in iris–ciliary body, followed by cornea and aqueous humor. An increase in carbon chain length made the prodrugs more enzymatically labile but more resistant to chemical hydrolysis at pH 7.4 and 34°C. The 5-butyryl ester of IDU exhibited an approximately fourfold increase in aqueous humor IDU concentration relative to IDU at 25 min following instillation of 25-µl 5 mM solutions. 相似文献
7.
Ji-Su Li Shu-Ping Tong Ludmila Vitvitski Christian Trpo 《Journal of medical virology》1995,45(2):151-155
Hepatitis C virus (HCV) exhibits considerable sequence variability and circulates in the blood at extremely low levels. Current methods for detecting HCV RNA are based mostly on nested polymerase chain reaction (PCR), in which part of the first amplification product is reamplified in the second tube by an internal primer pair. A novel nested PCR method was developed in which the two successive amplification processes are carried out in the same tube with a single step of physical manipulation. Careful selection of highly conserved sequences of the 5′ noncoding region as primers enabled successful detection of all three major genotypes circulating in France, including the one with variation in this region. Retaining high sensitivity of the conventional nested PCR, the novel method reduced greatly the risk of carry-over contaminations. It was also cost- and time-saving. The one-step nested PCR method is especially suitable for routine diagnosis of HCV infection in clinical laboratories. © 1995 Wiley-Liss, Inc. 相似文献
8.
Andrulis IL Anton-Culver H Beck J Bove B Boyd J Buys S Godwin AK Hopper JL Li F Neuhausen SL Ozcelik H Peel D Santella RM Southey MC van Orsouw NJ Venter DJ Vijg J Whittemore AS;Cooperative Family Registry for Breast Cancer studies 《Human mutation》2002,20(1):65-73
A number of methods are used for mutational analysis of BRCA1, a large multi-exon gene. A comparison was made of five methods to detect mutations generating premature stop codons that are predicted to result in synthesis of a truncated protein in BRCA1. These included four DNA-based methods: two-dimensional gene scanning (TDGS), denaturing high performance liquid chromatography (DHPLC), enzymatic mutation detection (EMD), and single strand conformation polymorphism analysis (SSCP) and an RNA/DNA-based protein truncation test (PTT) with and without complementary 5' sequencing. DNA and RNA samples isolated from 21 coded lymphoblastoid cell line samples were tested. These specimens had previously been analyzed by direct automated DNA sequencing, considered to be the optimum method for mutation detection. The set of 21 cell lines included 14 samples with 13 unique frameshift or nonsense mutations, three samples with two unique splice site mutations, and four samples without deleterious mutations. The present study focused on the detection of protein-truncating mutations, those that have been reported most often to be disease-causing alterations that segregate with cancer in families. PTT with complementary 5' sequencing correctly identified all 15 deleterious mutations. Not surprisingly, the DNA-based techniques did not detect a deletion of exon 22. EMD and DHPLC identified all of the mutations with the exception of the exon 22 deletion. Two mutations were initially missed by TDGS, but could be detected after slight changes in the test design, and five truncating mutations were missed by SSCP. It will continue to be important to use complementary methods for mutational analysis. 相似文献
9.
A simple, economic, and sparing method for isolation of cardiomyocytes from adult rat heart is proposed. Ultrastructure of
cardiomyocytes from suspension of freshly isolated cells was studied by light and transmission electron microscopy. The isolated
cardiomyocytes were viable, had characteristic shape and size, and retained their normal structure.
__________
Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 9, pp. 357–360, September, 2005 相似文献
10.
Yoshihiro Kikkawa Hideki Abe Masahiro Fujita Tadahisa Iwata Yoshio Inoue Yoshiharu Doi 《Macromolecular chemistry and physics.》2003,204(15):1822-1831
Direct visualization of crystal growth in poly(L ‐lactide) thin films was carried out by using a temperature‐controlled atomic force microscopy (AFM). At the initial stage of crystallization, edge‐on lamellar crystals have nucleated and elongated. Subsequently, the edge‐on lamellar crystals showed S‐shaped morphology and changed their orientation from edge‐on manner to flat‐on one. The curvature of edge‐on lamellar crystal has been discussed in terms of inclination and distortion of polymer chains in the crystal. In addition, mechanism on the formation of flat‐on crystal from edge‐on lamellae was proposed as derivative growth on the basis of in situ AFM observation of crystal growth and enzymatic degradation.