全文获取类型
收费全文 | 252810篇 |
免费 | 17922篇 |
国内免费 | 1136篇 |
专业分类
耳鼻咽喉 | 2794篇 |
儿科学 | 6507篇 |
妇产科学 | 4611篇 |
基础医学 | 33053篇 |
口腔科学 | 4561篇 |
临床医学 | 25411篇 |
内科学 | 53812篇 |
皮肤病学 | 3396篇 |
神经病学 | 24342篇 |
特种医学 | 8420篇 |
外国民族医学 | 11篇 |
外科学 | 38557篇 |
综合类 | 3463篇 |
一般理论 | 318篇 |
预防医学 | 21459篇 |
眼科学 | 6592篇 |
药学 | 17018篇 |
6篇 | |
中国医学 | 366篇 |
肿瘤学 | 17171篇 |
出版年
2023年 | 1355篇 |
2022年 | 2446篇 |
2021年 | 5507篇 |
2020年 | 3285篇 |
2019年 | 5359篇 |
2018年 | 6018篇 |
2017年 | 4500篇 |
2016年 | 4989篇 |
2015年 | 5857篇 |
2014年 | 8648篇 |
2013年 | 11847篇 |
2012年 | 18123篇 |
2011年 | 18962篇 |
2010年 | 10606篇 |
2009年 | 9443篇 |
2008年 | 16626篇 |
2007年 | 17475篇 |
2006年 | 17325篇 |
2005年 | 17298篇 |
2004年 | 16208篇 |
2003年 | 15046篇 |
2002年 | 14071篇 |
2001年 | 2107篇 |
2000年 | 1601篇 |
1999年 | 2319篇 |
1998年 | 3068篇 |
1997年 | 2561篇 |
1996年 | 2186篇 |
1995年 | 2096篇 |
1994年 | 1745篇 |
1993年 | 1571篇 |
1992年 | 1258篇 |
1991年 | 1152篇 |
1990年 | 1000篇 |
1989年 | 976篇 |
1988年 | 966篇 |
1987年 | 947篇 |
1986年 | 951篇 |
1985年 | 963篇 |
1984年 | 1217篇 |
1983年 | 1123篇 |
1982年 | 1364篇 |
1981年 | 1312篇 |
1980年 | 1145篇 |
1979年 | 706篇 |
1978年 | 747篇 |
1977年 | 637篇 |
1976年 | 585篇 |
1975年 | 470篇 |
1974年 | 473篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Cell proliferation may be evaluated by various methods, including Ki-67 immunohistochemistry and measures of telomerase activity. Both methods would theoretically show comparable increases in a given case. To evaluate the relationship between these 2 markers of proliferation in aggressive mature B-cell lymphomas, 48 cases were studied. The study group included 5 cases of mantle cell lymphoma (MCL); 6 cases of Burkitt's/Burkitt's-like lymphoma (BL); 9 cases of follicular lymphoma, grade 3 (FLC); and 28 cases of diffuse large B-cell lymphoma (DLC). Telomerase activity was measured as total product generated (TPG) units, and TPG results for the aforementioned cases were compared to the TPG results for 10 cases of reactive follicular hyperplasia. An overlap in TPG scores between reactive cases and lymphoma cases was found. Significant differences in both log TPG (P = 0.0443) and Ki-67 (P = 0.0006) were seen in the different lymphoma types. A positive correlation between Ki-67 percentage and TPG score was identified in FLC (r = 0.9281; P = 0.0003), but a poor correlation between these 2 indicators was seen in the other lymphoma types. Cluster analysis identified distinct patterns for MCL, FLC, and BL, but heterogeneous patterns for DLC. Because increases in both Ki-67 proliferation and telomerase activity are reported in normal germinal centers (GCs), these tests were also evaluated for usefulness as markers of a GC cell phenotype. Among the FLC and DLC cases, features of a GC phenotype significantly correlated with increased Ki-67 percentage (P = 0.0152), but not with increased log TPG. An elevated log TPG correlated with CD10 expression, and elevated Ki-67 percentage correlated with both CD10 and BCL-6 expression. TPG level and Ki-67 percentage did not correlate with the presence of t(14;18) or BCL-2 protein expression. Although the proliferation patterns were fairly distinctive for MCL, FLC, and BL, these studies show that markers of cell proliferation do not by themselves,identify distinct subtypes of large cell lymphomas. With the exception of FLC, the tumors exhibited poor correlation between telomerase activity and Ki-67 proliferation index. These tests did show some correlation with expression of GC cell phenotypic markers, however. 相似文献
992.
A 2-week efficacy and safety study of eszopiclone in elderly patients with primary insomnia 总被引:6,自引:0,他引:6
STUDY OBJECTIVES: Evaluate the efficacy of eszopiclone in primary insomnia. DESIGN/SETTING: Randomized, double-blind, placebo-controlled multicenter in outpatient setting with weekly visits. PARTICIPANTS: Two-hundred thirty one men and women aged 65 to 85 years (mean age 72.3 years) with primary insomnia, as defined by the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition. INTERVENTIONS: Eszopiclone 1 mg (n = 72), eszopiclone 2 mg (n = 79), or placebo (n = 80) nightly for 2 weeks. MEASUREMENTS/RESULTS: Efficacy was assessed using an interactive voice response system. Following the predefined hierarchical testing strategy, the eszopiclone 2-mg group had a significantly shorter sleep latency compared with placebo over the double-blind period (P = .0034). The eszopiclone 2-mg group had significantly longer total sleep time (P = .0003) and eszopiclone 1-mg group had significantly shorter sleep latency (P < or = .012) compared with placebo. The eszopiclone 1-mg group was not significantly different from placebo on total sleep time or any other secondary efficacy endpoint. Secondary analyses indicated that the eszopiclone 2-mg group had significantly less wake after sleep onset; significantly fewer and shorter in duration daytime naps; and significantly higher ratings of sleep quality and depth, daytime alertness, and sense of physical well-being compared with placebo (P < .05). Eszopiclone was well tolerated. The most frequent treatment-related adverse event was unpleasant taste. CONCLUSION: Nightly treatment with eszopiclone 1 mg effectively induced sleep, while the 2-mg dose was effective in inducing and maintaining sleep. Eszopiclone was well tolerated in elderly patients with primary insomnia, and the sleep efficacy was accompanied by significantly less napping and significantly higher ratings of daytime alertness, sense of physical well-being, and several quality-of-life parameters at the higher dose. 相似文献
993.
Detection of turkey rhinotracheitis virus in turkeys using the polymerase chain reaction 总被引:1,自引:0,他引:1
Six-week-old turkey poults were infected with the virulent UK/3B/85 strain of TRTV. Tracheal and oesophageal swabs were made every 2 to 3 days from groups of five poults and the RNA extracted. The TRTV RNA was then reverse-transcribed into complementary DNA (cDNA) using an oligonucleotide complementary to the 3' end of the fusion protein (F) mRNA. The cDNA was then used in a polymerase chain reaction (PCR) with an upstream primer to generate a product of approximately 0.5 kbp which was detected by ethidium bromide staining after electrophoresis. In this way, TRTV was detected in both types of swab for 17 to 19 days post-infection, nearly 2 weeks after the peak titres of infectious virus. Swabs which were allowed to dry completely before RNA extraction were as successful as swabs kept wet and extracted almost immediately, useful for when samples are collected in the field. The oligonucleotides amplified the 0.5 kbp product from TRTV strains isolated in six countries over a 13-year period, indicating that they might be usable as 'universal' oligonucleotides for TRTV detection. 相似文献
994.
Recent studies [8,9] have shown that odors from stressed Norway rats act as signals to which other rats respond primarily by overall changes in activity and exploration. At present the source of these odors is unknown. In this study odors from urine, feces and the bodies of stressed rats were delivered along a runway in which the subjects had been previously trained to run for a water reward in the presence of odors from non-stressed rats. The results indicate that odors are released from the body surface and in the urine but not the feces of stressed rats. 相似文献
995.
996.
997.
A laboratory-developed analog signal processor, driven by a conventional polygraph recorder and associated signal conditioning devices, provides automatic heart beat-by-heart beat preprocessing of various cardiovascular functions for input to a laboratory-type minicomputer. The technique of preprocessing individual functions, integrated with the minicomputer system which includes an A/D converter and teletype as input-output peripherals, provides a low-cost data acquisition and reduction system for the on-line computation and analysis of cardiovascular functions in experimental research applications. Such preprocessing more efficiently uses the minicomputer's memory to handle large amounts of information since the digitized data is in the form of one data sample, per function, per heart beat. Preprocessing analog data provides a low density data format and simplified software programs that are ideally suited for the utilization of a minicomputer in this on-line application. 相似文献
998.
Polynucleotide Immune Complexes in Serum and Glomeruli of Patients with Systemic Lupus Erythematosus 总被引:25,自引:2,他引:25 下载免费PDF全文
Several types of antipolynucleotide antibodies were eluted by acid buffer or deoxyribonuclease treatment of glomeruli obtained from nine kidneys from patients with systemic lupus erythematosus (SLE). Anti-SDNA antibodies were found concentrated over serum levels in eight eluates, anti-NDNA in six eluates and anti-RNA Pr in four eluates; anti-DSRNA antibodies were not demonstrable in any eluate tested. Deoxyribonuclease treatment eluted a high incidence and greater quantity of anti-NDNA and anti-SDNA antibody, whereas anti-RNA Pr antibody was mainly eluted by acid buffer. Simultaneous studies of antibody and antigen in serial serum specimens and in glomeruli suggested that complexes of SDNA antibody or antigen excess were frequently deposited in SLE kidneys, in addition to complexes containing anti-NDNA and anti-RNA Pr. It was observed that studies of antibody titers alone were inadequate for predicting the types of complexes deposited in the kidney. Either antigen excess could obscure detection of humoral antibody or extremely high titers of antibody as observed for RNA Pr are not conducive to the formation of kidney localizing immune complexes in the absence of antigen. Immunofluorescence studies demonstrated the presence of SDNA antigen in most cases from which anti-SDNA antibody was eluted providing direct evidence for the presence of SDNA-anti-SDNA complexes in renal glomeruli. A study of complement components indicated that Clq was absent from cases in which little or no SDNA was deposited in renal glomeruli; although all nephritic kidneys demonstrated C3 deposits. Several hypotheses accounting for this observation are discussed, including the probable utilization of the alternate pathway by certain types of complexes and a direct reaction between C1q and circulating or tissue-bound NDNA or SDNA. 相似文献
999.
1000.
Irving Dardick Sharon Cavell David Moher Peggy Seely Alexander Dardick Marilyn McDougall Bruce F. Burns 《Ultrastructural pathology》1989,13(4):393-404
Ultrastructural morphometric analysis was carried out on six cases of lymph node biopsies with reactive hyperplasia to establish the frequency and depth of invaginations in nuclear profiles situated in the mantle zones and follicular centers. The frequency distribution of the depth of invaginations was similar in nuclear profiles whether in the small lymphocytes of mantle zones or the small, partially transformed (centrocytes) and fully transformed (centroblasts) lymphocytes of follicular centers. Invaginated and cleaved lymphocytes were not confined to the partially transformed (centrocytic) lymphocytes of follicular centers, and nuclear profiles with invaginations bore no resemblance to those depicted in the Lukes-Collins model. A considerable proportion of mantle zone lymphocyte nuclear profiles had invaginations (ranging from 7.5% to 53.6%) and there was no difference between the frequency of deep indentations or clefts in mantle zone lymphocytes (8.1 ± 5.4%) and the small unstimulated (9.3 ± 5.3%) and partially transformed (8.4 ± 1.4%) lymphocytes in follicular centers. Computer modeling of stylized nuclei with conical indentations indicated that all lymphocytic nuclei likely have multiple invaginations or groove-like creases. 相似文献