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   12040篇
  免费   1196篇
  国内免费   40篇
耳鼻咽喉   74篇
儿科学   405篇
妇产科学   371篇
基础医学   1886篇
口腔科学   255篇
临床医学   1338篇
内科学   2490篇
皮肤病学   209篇
神经病学   823篇
特种医学   588篇
外科学   1589篇
综合类   348篇
一般理论   7篇
预防医学   1147篇
眼科学   127篇
药学   990篇
中国医学   4篇
肿瘤学   625篇
  2021年   147篇
  2020年   98篇
  2019年   151篇
  2018年   162篇
  2017年   144篇
  2016年   136篇
  2015年   184篇
  2014年   261篇
  2013年   406篇
  2012年   491篇
  2011年   517篇
  2010年   305篇
  2009年   268篇
  2008年   437篇
  2007年   465篇
  2006年   469篇
  2005年   428篇
  2004年   411篇
  2003年   392篇
  2002年   387篇
  2001年   347篇
  2000年   356篇
  1999年   330篇
  1998年   203篇
  1997年   205篇
  1996年   229篇
  1995年   176篇
  1994年   171篇
  1993年   182篇
  1992年   266篇
  1991年   284篇
  1990年   259篇
  1989年   255篇
  1988年   270篇
  1987年   276篇
  1986年   251篇
  1985年   241篇
  1984年   209篇
  1983年   165篇
  1982年   123篇
  1981年   118篇
  1980年   114篇
  1979年   127篇
  1978年   112篇
  1977年   112篇
  1976年   109篇
  1975年   114篇
  1972年   109篇
  1971年   98篇
  1970年   95篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This study investigated the applicability and utility of Megargee and Bohn's MMPI-based offender classification system in correctional mental health units (MHUs). Previous studies found that 11 MHU samples (n = 1723) had substantially more offenders classified in the more pathological MMPI types than did 21 samples (n = 5881) drawn from general male populations in US prisons. In this study of 63 severely disturbed felons, 43% belonged to the most pathological type (‘group How’). Comparing MHU patients with general offenders from the same IvfIvIPI types on staff ratings and case history variables, we found that the MHU patients were significantly poorer in adjustment. Within the MHU sample, there was no difference in case history variables or adjustment ratings between those in the most and least severe MMPI types. These findings differed from those of studies using less severely disturbed, more heterogeneous, MHU populations. It was concluded that, in settings in which the entire population is flagrantly disturbed, the MMPI-based system is more useful in screening potential admissions than it is in making meaningful distinctions among those already admitted.  相似文献   
82.
Norbinaltorphimine (nor-BNI) is a bifunctional reagent developed as a selective antagonist of the kappa opioid receptor. In this paper we examined the in vitro selectivity of nor-BNI, 6-desoxy-6 beta-fluoronaltrexone (cycloFOXY), and the enantiomer of cycloFOXY, among opioid receptor subtypes. Nor BNI exhibited the highest affinity for kappa binding sites labeled by 3H-U69593 (Ki = 1.8nM), and was 27- to 29-fold less potent at mu and delta binding sites. In contrast, cycloFOXY had the highest affinity for mu binding sites (Ki = 2.62 nM), and bound to kappa and delta binding sites with Ki's of 9.3 nM and 89 nM, respectively. The enantiomer of cycloFOXY, did not inhibit binding even at concentrations greater than 10 microM, validating in part the use of 18F-labeled (+)-cycloFOXY to estimate "non-specific binding" in positron emission tomography. Additionally, we report that (S,S)-U50 488 and (R.R)-U50 488 bind to kappa binding sites labeled by 3H-U69 593 with Ki's of 0.89 nM and 299 nM, respectively.  相似文献   
83.
Single photon emission computed tomography (SPECT) imaging of six Huntington's disease patients revealed a striking reduction in regional uptake of cerebral blood flow markers in vivo. Similar changes were found in one patient with "early stage" disease. The findings are compared with parallel magnetic resonance imaging (MRI) studies, and in one case, results of postmortem examination.  相似文献   
84.
Summary The site of omeprazole inhibition of adrenal steroidogenesis has been sought in vivo by analyzing the patterns of urinary steroid metabolite excretion after 6 days of treatment with placebo/omeprazole.Excretion rates of androsterone, aetiocholanolone, dehydroepiandrosterone, 11 hydroxyandrosterone, tetrahydrocortisone, tetrahydrocortisol and cortolone were reduced, indicating a block at an early step in steroidogenesis, possibly cholesterol side-chain cleavage. In vitro studies have confirmed this finding by measuring conversion of added precursors to cortisol in isolated bovine adrenocortical cells. Cortisol synthesis from added 20 hydroxycholesterol was inhibited by 83% in the presence of 100 µg omeprazole/ml. Conversion from pregnenolone and progesterone and their 17 hydroxylated derivatives was inhibited by 20–40% whereas cortisol production from added 11 deoxycortisol was not affected.These data suggest that omeprazole primarily inhibits cholesterol cleavage and does not inhibit 3 hydroxysteroid dehydrogenase, 17 hydroxylase or 11 hydroxylation; 21 hydroxylase activity may be marginally attenuated.  相似文献   
85.
We have found that neoplastic transformation alters the ability of cells to grow on substrata of tissue extracts, "biomatrices", enriched in extracellular matrix. Tumor cells were able to survive and grow at lower densities and on more types of biomatrices than normal cells. When plated at high densities (greater than 10(5) cells/60 mm dish), tumor cells attached with equal efficiency and grew at similar rates and to equivalent saturation densities on biomatrices derived from all tissues. However, at low (10(2)-10(4)/60-mm dish) seeding densities, the tumor cells grew only on certain types of biomatrix. For the various hepatoma and mammary carcinoma cell lines tested, the tissue specificity in clonal growth on biomatrices correlated with their organ site specificity for metastasis in vivo in immunosuppressed, athymic nude mice. Analysis of the effects of purified matrix components (adhesion proteins, collagens, glycosaminoglycans) indicated that only the glycosaminoglycans influenced density-dependent survival and growth of tumor cells with effects that differed with respect to the cell's metastatic potential. The results indicate that the ability of tumor cells to colonize specific tissues represents, in part, regulation of low density survival and growth by extracellular matrix and are suggestive that one of the matrix components responsible may be proteoglycans or their glycosaminoglycan chains.  相似文献   
86.
87.
The Second International Nonhuman Primate Histocompatibility Workshop permitted comparison of rhesus monkey alloantisera developd in various laboratories on a single common panel of related and unrelated monkeys. Analysis of the data permits the conclusion that at least nine specificities are recognized by more than one laboratory, including six at the first locus and three at the second locus.  相似文献   
88.
The Gm-Pi linkage heterogeneity in view of Pi M subtypes   总被引:1,自引:3,他引:1  
In this study linkage between the loci for Gm (γ-type heavy-chain immunoglobulin markers) and Pi (α1-antitrypsin/α1-protease inhibitor) has been shown in families segregating for the Pi M subtypes (Ml, M2, M3 and Msal) as identified by separator isoelectric focusing. The estimate for the Gm-Pi (M-type) recombination is 0-29 (95% limits 0-24-O37) at a peak lod score of 4-31 and with no sex difference. This value is not significantly different from updated recombination frequency estimates for Gm-Pi in Pi MS (0-26) and Pi MZ, SZ and FZ families (0 21). The overall Gm-Pi recombination fraction estimate of 0 26 (95 % limits O23-0-30) at a peak lod score of 20-75 must now be considered as solid. There is a significant heterogeneity within the male Pi MZ families in that the new Finnish families show a higher recombination between Gm and Pi. There is also a possible segregation distortion (Z:M = 23:8). The heterogeneity is discussed in terms of haplotypes, the behaviour of which could be determined by linked genes or chromosomal rearrangements. The possibility that the α1-antitrypsin level influences recombination frequency has not been ruled out, but cannot explain the heterogeneity within Pi MZ families.  相似文献   
89.
The ramification of the portal vein at the porta hepatis was studied by anatomic dissection performed in 32 formalin fixed human livers. In all the specimens there were branches which ran towards the caudate lobe, arising from the portal vein and either from the left or the right portal branches. Tri-and quadrifurcation of the portal vein was observed. In 5 cases (16%) there were branches arising from left portal branch or portal vein and directed anteriorly to the quadrate lobe or to the region of the gall-bladder sulcus. These branches ranged from 1.0 to 6.0 mm in diameter. The portal caudate branches were divided into 3 groups.Group 1: Branches to the papillary process; 1 or 2 branches in 26 cases (82%), 3 or 5 branches in 3 cases (9%) and no branches in 3 cases (9%);  相似文献   
90.
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