首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8578篇
  免费   421篇
  国内免费   58篇
耳鼻咽喉   45篇
儿科学   152篇
妇产科学   115篇
基础医学   1516篇
口腔科学   131篇
临床医学   733篇
内科学   1469篇
皮肤病学   189篇
神经病学   947篇
特种医学   409篇
外科学   1210篇
综合类   48篇
一般理论   3篇
预防医学   417篇
眼科学   255篇
药学   713篇
中国医学   11篇
肿瘤学   694篇
  2023年   32篇
  2022年   73篇
  2021年   112篇
  2020年   70篇
  2019年   103篇
  2018年   106篇
  2017年   84篇
  2016年   126篇
  2015年   165篇
  2014年   192篇
  2013年   321篇
  2012年   457篇
  2011年   510篇
  2010年   323篇
  2009年   297篇
  2008年   513篇
  2007年   593篇
  2006年   575篇
  2005年   638篇
  2004年   532篇
  2003年   579篇
  2002年   522篇
  2001年   123篇
  2000年   91篇
  1999年   134篇
  1998年   151篇
  1997年   100篇
  1996年   92篇
  1995年   73篇
  1994年   67篇
  1993年   80篇
  1992年   81篇
  1991年   93篇
  1990年   56篇
  1989年   65篇
  1988年   45篇
  1987年   44篇
  1986年   45篇
  1985年   34篇
  1984年   33篇
  1983年   37篇
  1982年   38篇
  1981年   32篇
  1980年   34篇
  1979年   33篇
  1978年   30篇
  1977年   32篇
  1975年   27篇
  1974年   29篇
  1971年   26篇
排序方式: 共有9057条查询结果,搜索用时 10 毫秒
71.
To increase the likelihood of finding genetic variation conferring liability to eating disorders, we measured over 100 attributes thought to be related to liability to eating disorders on affected individuals from multiplex families and two cohorts: one recruited through a proband with anorexia nervosa (AN; AN cohort); the other recruited through a proband with bulimia nervosa (BN; BN cohort). By a multilayer decision process based on expert evaluation and statistical analysis, six traits were selected for linkage analysis (1): obsessionality (OBS), age at menarche (MENAR), and anxiety (ANX) for quantitative trait locus (QTL) linkage analysis; and lifetime minimum body mass index (BMI), concern over mistakes (CM), and food-related obsessions (OBF) for covariate-based linkage analysis. The BN cohort produced the largest linkage signals: for QTL linkage analysis, four suggestive signals: (for MENAR, at 10p13; for ANX, at 1q31.1, 4q35.2, and 8q13.1); for covariate-based linkage analyses, both significant and suggestive linkages (for BMI, one significant [4q21.1] and three suggestive [3p23, 10p13, 5p15.3]; for CM, two significant [16p13.3, 14q21.1] and three suggestive [4p15.33, 8q11.23, 10p11.21]; and for OBF, one significant [14q21.1] and five suggestive [4p16.1, 10p13.1, 8q11.23, 16p13.3, 18p11.31]). Results from the AN cohort were far less compelling: for QTL linkage analysis, two suggestive signals (for OBS at 6q21 and for ANX at 9p21.3); for covariate-based linkage analysis, five suggestive signals (for BMI at 4q13.1, for CM at 11p11.2 and 17q25.1, and for OBF at 17q25.1 and 15q26.2). Overlap between the two cohorts was minimal for substantial linkage signals.  相似文献   
72.
73.
The synthesis and the results of the structural study of two copolysiloxanes with laterally fixed trinitrofluorenone (TNF) units is reported. The two copolysiloxanes having 2,4 ( 1a ) and 5,3 ( 1b ) dimethylsiloxane comonomer units per TNF side group differ significantly in their phase behaviour as evident from optical microscopy, differential scanning calorimetry and X-ray scattering: 1b shows a nematic mesophase whereas 1a is an amorphous material. The different phase behaviour is discussed in terms of microphase separation between the siloxane backbone and TNF side groups.  相似文献   
74.
Differential pulse polarography (DPP) and cyclovoltammetry (CV) were conducted to study the redox behaviour of poly(p-phenylenevinylene) (PPV; E = 0,76 V; E = ?1,74 V) as well as of three insoluble PPV-derivatives and four soluble aryl-substituted PPV's. Oxidation studies of DP-PPV, DMOP-PPV and DPOP-PPV in comparison with two series of the oligomeric model compounds 1a–e and 2a–d lead to the conclusion that for DMOP-PPV (E = 0,98, 1,24,1,31 V) and DPOP-PPV (E = 1,10, 1,29, 1,44 V) three distinct oxidation stages exist, which are reversibly occupied and represent 1/2, 1 and 2 positive charges per repeating unit. In DP-PPV two oxidation stages representing 1/2 and 1 positive charges were found to be reversibly occupied (E = 1,17, 1,69 V), whereas at higher potentials irreversible dehydrocyclization occurred.  相似文献   
75.
U. Wahn    U. Herold    K. Danielsen  H. Løwenstein 《Allergy》1982,37(5):335-343
In order to determine the allergenic activity of five purified horse allergens, 22 children allergic to horses according to history, skin test, and leukocyte histamine release were evaluated. Washed leukocytes from all patients were tested for allergen-induced histamine release utilizing four epidermal horse allergens (Ags 6, 9, 11 , and 15) and horse serum albumin. Crossed radioimmunoelectrophoresis was carried out with a standardized horse dander extract and serum from each patient.
The results showed considerable variation in the individual allergoprints. Ag 11 had the highest mean allergenic activity. Sensitivity to horse serum albumin was demonstrated three times. Our data show that the amount of serum IgE antibodies bound by horse allergens correlates significantly with the capacity of the allergens to induce histamine release from washed leukocytes.  相似文献   
76.
Copolymers of N,N-dimethylacrylamide (DMA) and 4-phenylazophenyl acrylate (PAPA) have been prepared by free-radical copolymerization in dioxane (DMAP-x). The molecular weights of the copolymers show a strong decrease with increasing azobenzene content due to the retardation effect of the azobenzene group. An analogous decrease in molecular weight was found with a number of polymers of DMA which were polymerized in the presence of the non-polymerizable model 4-phenylazophenyl propionate (PAPP). We were able to induce a lower critical solution temperature (LCST) above a certain content of azobenzene moieties in the copolymers (DMAP-x) in contrast to the good water solubility of poly(DMA). Due to the reversible photoisomerization and the concomitant change in the dipole moment of the azobenzene moieties, the LCST depends not only on the content of azobenzene but also on the degree of isomerization. A difference in the LCST up to 20°C was found for dark adapted polymer solutions (0% Z-isomer) and polymer solutions in the photostationary state (ca. 85% Z-isomer). Within this temperature range the polymer can be precipitated by irradiation with light.  相似文献   
77.
The inheritance of a deficient delta-aminolevulinic acid dehydrase (ALA-D; synonym: porphobilinogen synthase; EC 4.2.1.24) was studied in blood samples of two families over three generations. The propositus in each family was a young male acute hepatic porphyria patient with an almost complete ALA-D deficiency in the homozygous state (ALA-D activity less than 2% of controls). Heterozygotes are clinically non-affected (mean ALA-D 36% of controls). The mode of transmission could be traced by enzyme activity and electrophoretic polymorphism studies. Heterozygotes are detected by the demonstration of enzyme activity in the gel. The notation D was used for the gene expressing the defective enzyme. The "phenotype" D-1 was observed in six, the "phenotype" D-2 in three of all heterozygotes studied. These results are compatible with a single normal allele in heterozygotes responsible for enzyme activity. Quantitative assays and the segregation pattern in both families suggest a 3-allele-system for the inheritance of ALA-D deficiency.  相似文献   
78.
Tracer diffusion coefficients D* of both components were measured in mixtures of polystyrene (PS) and polymethylstyrene (PMS), a random copolymer from 60 wt.-% of m-methylstyrene and 40 wt.-% of p-methylstyrene. The results are interpreted in terms of the free-volume theory which yields master curves even for “asymmetric” mixtures of oligomer and polymer chains, if D* is drawn versus the distance from the glass transition temperature, TTg. Whereas D* was measured by the forced Rayleigh scattering technique, we also studied photon correlation spectroscopy in these mixtures and observed “slow modes” with decay constants that correspond to diffusion coefficients 2–3 decades smaller than the interdiffusion coefficient.  相似文献   
79.
Chronic allograft nephropathy is characterized by chronic inflammation and fibrosis. Because retinoids exhibit anti-proliferative, anti-inflammatory, and anti-fibrotic functions, the effects of low and high doses of 13-cis-retinoic acid (13cRA) were studied in a chronic Fisher344-->Lewis transplantation model. In 13cRA animals, independent of dose (2 or 20 mg/kg body weight/day) and start (0 or 14 days after transplantation) of 13cRA administration, serum creatinine was significantly lower and chronic rejection damage was dramatically reduced, including subendothelial fibrosis of preglomerular vessels and chronic tubulointerstitial damage. The number of infiltrating mononuclear cells and their proliferative activity were significantly diminished. The mRNA expression of chemokines (MCP-1/CCL2, MIP-1alpha/CCL3, IP-10/CXCL10, RANTES/CCL5) and proteins associated with fibrosis (plasminogen activator inhibitor-1, transforming growth factor-beta1, and collagens I and III) were strikingly lower in treated allografts. In vitro, activated peritoneal macrophages of 13cRA-treated rats showed a pronounced decrease in protein secretion of inflammatory cytokines (eg, tumor necrosis factor-alpha, interleukin-6). The suppression of the proinflammatory chemokine RANTES/CCL5 x 13cRA in fibroblasts could be mapped to a promoter module comprising IRF-1 and nuclear factor-kappaB binding elements, but direct binding of retinoid receptors to promoter elements could be excluded. In summary, 13cRA acted as a potent immunosuppressive and anti-fibrotic agent able to prevent and inhibit progression of chronic allograft nephropathy.  相似文献   
80.
Zusammenfassung 1. Es werden an quergestreiften Muskeln (Zwerchfell, Herzvorhof von Warmblütern, Froschherz) unter den Bedingungen von Substratund Sauerstoffmangel Funktion und histologischer Zustand verglichen.2. Drosselung der Energiezufuhr führt in jedem Falle zu negativer Inotropie und diastolischem Stillstand. Dies führt zu dem zwingenden Schluß, daß die Kontraktion und nicht die Erschlaffung den energieverbrauchenden Teil des Kontraktionsvorganges darstellt.3. Gleichzeitiger Glucose- und Sauerstoffmangel führt erst mit dem Erlöschen der Glykogenolyse zur Kontraktur, die nach völligem Glykogenschwund irreversibel wird (Totenstarre).4. Die Totenstarre wird als Modellkontraktion abgelehnt.5. Aus den untersuchten Mangelbedingungen läßt sich eine Reihenfolge der Energieausnützung für den quergestreiften Muskel ableiten, wobei wesentliche Unterschiede zwischen Warmblüter und Kaltblüter bestehen.Mit 7 Textabbildungen  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号