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971.
Both normetanephrine and metanephrine were found to be oxidized by both types of monoamine oxidase in mouse liver mitochondria. Both Km and Vmax values of type B MAO for both substrates were higher than those of type A MAO, which caused the shift of inhibition curves with clorgyline and deprenyl according to the increase in substrate concentration. 相似文献
972.
Human gamma-chain genes are rearranged in leukaemic T cells and map to the short arm of chromosome 7 总被引:1,自引:0,他引:1
C Murre R A Waldmann C C Morton K F Bongiovanni T A Waldmann T B Shows J G Seidman 《Nature》1985,316(6028):549-552
Three gene families that rearrange during the somatic development of T cells have been identified in the murine genome. Two of these gene families (alpha and beta) encode subunits of the antigen-specific T-cell receptor and are also present in the human genome. The third gene family, designated here as the gamma-chain gene family, is rearranged in murine cytolytic T cells but not in most helper T cells. Here we present evidence that the human genome also contains gamma-chain genes that undergo somatic rearrangement in leukaemia-derived T cells. Murine gamma-chain genes appear to be encoded in gene segments that are analogous to the immunoglobulin gene variable, constant and joining segments. There are two closely related constant-region gene segments in the human genome. One of the constant-region genes is deleted in all three T-cell leukaemias that we have studied. The two constant-region gamma-chain genes reside on the short arm of chromosome 7 (7p15); this region is involved in chromosomal rearrangements identified in T cells from individuals with the immunodeficiency syndrome ataxia telangiectasia and observed only rarely in routine cytogenetic analyses of normal individuals. This region is also a secondary site of beta-chain gene hybridization. 相似文献
973.
Stromal cells play a critical role in haematopoiesis, both in a permissive and, probably, in a directive manner. Study of the interactions between stromal cells and haematopoietic stem cells, however, is difficult to perform using whole bone marrow, in which stem cells are indistinguishable from precursor cells and maturing haematopoietic cells, and where stromal and haematopoietic cells co-exist in a heterogeneous mixture. We have purified primitive haematopoietic spleen colony-forming cells (CFU-S) using fluorescence-activated cell sorting (FACS) and produced CFU-S populations which approach 100% purity (ref. 6 and B.I.L. and E.S., in preparation). This cell population is devoid of significant stromal cells and mature haematopoietic cells. Here, we report that when purified CFU-S are seeded onto a stromal adherent layer in vitro, foci of haematopoietic cells develop within the stroma followed by production of a wave of maturing and mature progeny. However, self-renewal of CFU-S does not occur and haematopoietic activity rapidly declines, indicating that caution should be applied in the use of highly purified stem cells for human bone marrow transplantation. 相似文献
974.
Morphological transformation in vivo of human uterine cervix with papillomavirus from condylomata acuminata 总被引:3,自引:0,他引:3
J W Kreider M K Howett S A Wolfe G L Bartlett R J Zaino T Sedlacek R Mortel 《Nature》1985,317(6038):639-641
Carcinoma of the human uterine cervix has been associated with several infectious agents including papillomavirus. Papillomavirus group-specific antigen (GSA) and viral particles have been demonstrated in human condylomata acuminata (CA) and flat warts of the uterine cervix. Cell alterations consisting of nuclear enlargement, hyperchromasia, irregularity, binucleation and cytoplasmic clearing (koilocytosis) are often interpreted as mild to moderate dysplasia. Present evidence that human papillomavirus (HPV) is responsible for the development of these lesions relies on the association of GSA and virus particles in the affected tissue, fulfilling the first two of Koch's postulates. Direct proof of an aetiological relationship, however, requires induction of the CA change in normal, human uterine cervix after exposure to papillomavirus. Infecting human subjects with HPV is ethically unacceptable and no satisfactory alternative systems have been defined. Also, human cell cultures do not support growth or transformation by HPV. Here we report the first demonstration of the morphological transformation of human tissues with a human papillomavirus under controlled, experimental conditions. 'Transformation' is used here in its literal sense to refer to a heritable morphological alteration in the appearance of the cells. The use of this term does not indicate that the changes described are neoplastic, but they are identical to the dysplastic changes found in biopsies of uterine cervical CA. Our results demonstrate the direct involvement of CA virus in dysplastic change of human cervical tissue and indicate that the experimental system described may be useful in elucidating the contribution of human papillomaviruses to the pathogenesis of human cervical cancer. 相似文献
975.
N T Chang J Huang J Ghrayeb S McKinney P K Chanda T W Chang S Putney M G Sarngadharan F Wong-Staal R C Gallo 《Nature》1985,315(6015):151-154
Human T-cell lymphotropic retrovirus type III (HTLV-III), also called lymphadenopathy-associated virus (LAV), has been identified as the aetiological agent of acquired immune deficiency syndrome (AIDS). The sera of most patients with AIDS or AIDS-related complexes, and of asymptomatic individuals infected with HTLV-III, contain antibodies against antigens of HTLV-III. The characterization of these antibodies and their corresponding viral antigens is important not only for understanding immunity against HTLV-III and the pathology of AIDS, but also for the development of diagnostic methods and preventive vaccine for AIDS. Following the successful establishment of a long-term T-cell line permissive for HTLV-III replication, large quantities of virus have been produced, facilitating the purification of viral proteins and the development of mouse monoclonal antibodies against several viral antigens. More recently, the structure of HTLV-III proviral DNA has been elucidated. We now report the production, by genetic engineering methods, of a peptide encoded by a gene segment of HTLV-III. A 1.1-kilobase (kb) EcoRI DNA segment from an isolate of HTLV-III was inserted into a lpp and lac promoter-coupled expression vector, pIN-III-ompA. Escherichia coli transformants of this plasmid produced a peptide of relative molecular mass (Mr) 15,000 (15K) which was strongly immunoreactive with anti-HTLV-III antibodies present in sera from AIDS patients. Lysates of the clones expressing this 15K peptide inhibited the reactivity of the p31 virion protein with AIDS sera, suggesting that it is a fragment of the viral p31 protein. The peptide reacted with sera from all 20 AIDS patients but none of the 8 normal controls tested. These results suggest that the peptide may be useful for detecting anti-HTLV-III antibodies in blood samples. 相似文献
976.
Scavenger receptor family proteins: roles for atherosclerosis, host defence and disorders of the central nervous system 总被引:11,自引:1,他引:10
Y. Yamada T. Doi T. Hamakubo T. Kodama 《Cellular and molecular life sciences : CMLS》1998,54(7):628-640
In this review, we summarize the structure and function of the scavenger receptor family of proteins including class A (type
I and II macrophage scavenger receptors, MARCO), class B (CD36, scavenger receptor class BI), mucinlike (CD68/macrosialin,
dSR-CI) and endothelial (LOX-1) receptors. Two motifs have been identified as ligand-binding domains a charged collagen structure
of type I and II receptors, and an immunodominant domain of CD36. These structures can recognize a wide range of negatively
charged macromolecules, including oxidized low-density lipoproteins, damaged or apoptotic cells, and pathogenic microorganisms.
After binding, these ligands can be either internalized by endocytosis or phagocytosis, or remain at the cell surface and
mediate adhesion or lipid transfer through caveolae. Under physiological conditions, scavenger receptors serve to scavenge
or clean up cellular debris and other related materials, and they play a role in host defence. In pathological states, they
mediate the recruitment, activation and transformation of macrophages and other cells which may be related to the development
of atherosclerosis and to disorders caused by the accumulation of denatured materials, such as Alzheimer's disease.
Received 17 September 1997; received after revision 16 March 1998; accepted 17 March 1998 相似文献
977.
多机组空调系统部分负荷下的节能策略研究 总被引:1,自引:1,他引:0
针对冷水机组大部分时间都是在部分负荷下运行的现状,提出了一种多机组空调系统并联的节能策略.运用模型仿真和试验验证手段研究节能优化运行策略对机组性能改善效果.试验结果表明:当机组由100%负荷降为50%负荷时,机组的冷凝温度由47.2℃下降到42.5℃,蒸发温度由2.2℃上升到3.5℃,COP值提高9.5%.从而表明该节能策略对多机组空调系统在部分负荷下的性能改善具有较大潜力.同时针对试验结果与仿真结果存在的差距,分析了产生的原因并提出了进一步的改进措施. 相似文献
978.
Conversion of mdx myofibres from dystrophin-negative to -positive by injection of normal myoblasts 总被引:38,自引:0,他引:38
An important corollary to the recent advances in our understanding of the primary cause of Duchenne muscular dystrophy, is the validation of genuine genetic homologues as animal models of the disease in which potential therapies can be tested. The persistent skeletal muscle necrosis that characterizes human Duchenne muscular dystrophy is also seen in the mdx mouse and is, in both, a consequence of a deficiency of dystrophin, probably within the muscle fibres themselves. As injected muscle precursor cells of one genotype can fuse with host muscle fibres of a different genotype and express the donor genes, we decided to test grafts of normal muscle precursor cells to see if they could induce synthesis of dystrophin in innately dystrophin-deficient mdx muscle fibres. We show that injected normal muscle precursor cells can fuse with pre-existing or regenerating mdx muscle fibres to render many of these fibres dystrophin-positive and so to partially or wholly rescue them from their biochemical defect. 相似文献
979.
Effect of high anodic polarization on the passive layer properties of superduplex stainless steel friction stir welds at different chloride electrolyte pH values and temperatures 下载免费PDF全文
L. A. Santa-Cruz G. Machado A. A. Vicente T. F. C. Hermenegildo T. F. A. Santos 《矿物冶金与材料学报》2019,26(6):710-721
The conditions used for friction stir welding of duplex stainless steels determine the resulting mechanical and corrosion performance of the material.This study investigates the corrosion resistance of UNS S32750 and S32760 superduplex stainless steels(SDSSs)joined by friction stir welding,employing cyclic polarization,Mott–Schottky,and microscopy techniques for analysis.The microscopy images indicated the presence of a deleterious intermetallic phase after electrolytic etching of S32760,as well as decreased corrosion resistance.The presence of molybdenum in the steels promoted better passive behavior at low pH.The Mott–Schottky curves revealed p-n heterojunction behavior of the passive oxide.Images acquired after the polarization test by scanning electron microscopy showed higher passivation propensity with increases of temperature and pH. 相似文献
980.
基于分级遗传算法的结构损伤识别方法 总被引:7,自引:1,他引:6
提出了一种基于遗传算法的利用不完整振动数据识别结构损伤的新方法,该方法首先扩展不完整的振型并利用单元能量熵差比确定结构损伤的大致位置,然后采用二级搜索策略,借助遗传算法确定结构损伤的程度,数值计算结果表明,当可能的损伤区域较大时,本方法较直接搜索策略更能有效地确定结构损伤的程度。 相似文献