全文获取类型
收费全文 | 109669篇 |
免费 | 8911篇 |
国内免费 | 479篇 |
专业分类
耳鼻咽喉 | 1254篇 |
儿科学 | 2647篇 |
妇产科学 | 2028篇 |
基础医学 | 12926篇 |
口腔科学 | 2215篇 |
临床医学 | 14029篇 |
内科学 | 21822篇 |
皮肤病学 | 1571篇 |
神经病学 | 11064篇 |
特种医学 | 4132篇 |
外国民族医学 | 3篇 |
外科学 | 17993篇 |
综合类 | 1115篇 |
一般理论 | 132篇 |
预防医学 | 9532篇 |
眼科学 | 2500篇 |
药学 | 6604篇 |
中国医学 | 106篇 |
肿瘤学 | 7386篇 |
出版年
2024年 | 99篇 |
2023年 | 956篇 |
2022年 | 987篇 |
2021年 | 2312篇 |
2020年 | 1689篇 |
2019年 | 2235篇 |
2018年 | 3172篇 |
2017年 | 2493篇 |
2016年 | 2620篇 |
2015年 | 2921篇 |
2014年 | 4231篇 |
2013年 | 5527篇 |
2012年 | 7849篇 |
2011年 | 8268篇 |
2010年 | 5063篇 |
2009年 | 4763篇 |
2008年 | 7375篇 |
2007年 | 7626篇 |
2006年 | 7411篇 |
2005年 | 7066篇 |
2004年 | 6832篇 |
2003年 | 6148篇 |
2002年 | 5836篇 |
2001年 | 1062篇 |
2000年 | 661篇 |
1999年 | 1118篇 |
1998年 | 1476篇 |
1997年 | 1169篇 |
1996年 | 1060篇 |
1995年 | 906篇 |
1994年 | 809篇 |
1993年 | 746篇 |
1992年 | 607篇 |
1991年 | 554篇 |
1990年 | 428篇 |
1989年 | 400篇 |
1988年 | 372篇 |
1987年 | 377篇 |
1986年 | 335篇 |
1985年 | 346篇 |
1984年 | 375篇 |
1983年 | 310篇 |
1982年 | 385篇 |
1981年 | 313篇 |
1980年 | 253篇 |
1979年 | 128篇 |
1978年 | 158篇 |
1977年 | 125篇 |
1976年 | 106篇 |
1974年 | 106篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Thomas C. Klein Rainer Dffinger Mark B. Pepys Ulrich Rüther Bruno Kyewski 《European journal of immunology》1995,25(12):3489-3495
The understanding of immunological tolerance has been greatly aided by the development of transgenic animal models in which expression of a specific T cell receptor (or B cell receptor) and its cognate self antigen is experimentally controlled. In most cases, expression of the self antigen was constitutive and did not allow for variation of its time- and dose-dependent expression pattern, parameters which are known to influence the balance of tolerance versus immunity. We describe a transgenic model in which expression of human C-reactive protein (hCRP), an acute-phase protein, is tightly controlled at basal levels (female mice express around 10?9 M and male mice 5 × 10?7 M circulating hCRP) and is highly inducible (induction factor of 25–500). T cells from C57BL/6 mice recognize two epitopes of hCRP termed A (residues 79–95) and B (residues 87–102). Different efficacies of presentation in vitro and in vivo identify epitope A as subdominant and epitope B as dominant. T cells of non-induced hCRP transgenic mice are tolerant to the dominant epitope, but reactive to the subdominant epitope. A hCRP-specific IgG antibody response is detectable in transgenic mice, but is weaker than in littermates. Upon induction of hCRP, both T cell epitopes are presented by thymic and splenic antigen-presenting cells (APC) in vivo. Kinetics of presentation by splenic APC closely match serum kinetics of hCRP, whereas presentation in the thymus is considerably prolonged. This model enables epitope-specific T cell tolerance to be studied as a function of time- and dose-dependent expression of the self antigen. 相似文献
992.
H Burkhardt R Holmdahl R Deutzmann H Wiedemann H von der Mark S Goodman K von der Mark 《European journal of immunology》1991,21(1):49-54
Immunization of certain strains of mice with native type II collagen (CII) induces both development of arthritis and an antibody response to autologous CII. The autoantibody response in a high-responder strain, the DBA/1 mouse, has been described earlier, and a number of monoclonal antibodies have been characterized for arthritogenicity and autoreactive binding to cartilage in vivo and in vitro. Here we map the antigenic epitope of one of these arthritogenic monoclonal antibodies (CII-C1). It belongs to a group of antibodies recognizing the CNBr fragment alpha 1(II)-CB11 of CII. Using the enzyme-linked immunosorbent assay technique, we show that the antibody reacts only with native, triplehelical CII, but not with other collagens. The antibody is able to stain specifically the CB11 fragment by immunoblotting, suggesting some partial renaturation of the CNBr fragment into triple-helical structures after blotting. The binding site of CII-C1 on CB11 was further focused by rotary shadowing of antibody-labeled CII to a site 89 +/- 8 nm from the amino end of CII, corresponding to the middle of CB11. This location was confirmed by cleavage of CB11 with trypsin, separation of the tryptic peptides by high-performance liquid chromatography and dot-blot analysis of the antigenic peptides with the CII-C1 antibody. Sequencing of the single positive peptide located the antigenic epitope within the sequence GFAGQAGPAGATGAPGRP (residues 316-333). Assuming 0.29 nm per residue, this corresponds to a position within 92-96.5 nm from NH2 terminal end of CII. Apart from glycine residues, which are not exposed on the triple-helical structure, only two amino acid residues (F-x-y-Q) are conserved in CII from different species but are not found in the triple-helix of other collagens except type IV collagen. Therefore, this structure is likely to be of critical importance for the binding of the CII-C1 antibody. Of potential importance is that this structure is also found in certain other arthritogenic proteins such as 65-kDa mycobacterial protein, in CMV and EBV. 相似文献
993.
Mark J Elder MD FRACS FRACO Paul Hiscott PhD FRCS MRCPath John K.G Dart DM FRCS FRCOphth 《Human pathology》1997,28(12):1348-1354
Cicatricial conjunctivitis may be a sequel to systemic disorders (eg, Stevens-Johnson syndrome, cicatricial pemphigoid) or local disorders such as chemical burns. The cicatrisation is often associated with corneal epithelial changes that cause visual loss. These have been attributed to encroachment of the conjunctival epithelium over the cornea. However, the epithelial anomalies are poorly understood. We investigated the corneal epithelial changes in cicatricial conjunctivitis with an immunohistochemical study of intermediate filaments in normal and pathological specimens. Our results show that the normal corneal epithelium is immunoreactive for cytokeratin 3 (CK 3) but not cytokeratin 19 (CK 19), whereas normal conjunctival epithelium is CK 3 negative and CK 19 positive. Conjunctiva artificially transposed over the cornea (after therapeutic conjunctival flap reconstruction) retained the normal pattern of conjunctival cytokeratin expression (CK 3 negative, CK 19 positive). Conversely, the entire corneal epithelium exhibited the normal cytokeratin pattern (CK 3 positive, CK 19 negative) in 82% of Stevens-Johnson, 80% of cicatricial pemphigoid, and 69% of chemical burns specimens. The findings suggest that conjunctival encroachment is not responsible for the changes at the corneal surface in cicatricial conjunctivitis and that the abnormal corneal epithelium is derived from native corneal cells in these diseases. 相似文献
994.
The effect of buprenorphine on bremazocine-induced diuresis was tested in the rat to determine the nature of buprenorphine's action at the opioid receptor. Both morphine-tolerant and naive rats were used to account for possible antidiuretic effects of buprenorphine at the µ site. Separate experiments established that the morphine pretreatment caused profound tolerance with respect to the antidiuretic action of µ agonists. Buprenorphine acted as a potent antagonist (ID50 = 11µg/kg) of the diuretic action of the agonist bremazocine (ED50 = l0 µg/kg). The similar potency of buprenorphine as an antagonist of bremazocine in naive and morphine-tolerant rats further supports the hypothesis that buprenorphine exerts it's antidiuresis via an antagonistic effect at sites, rather than as an agonist at the µ sites. The high affinity displayed by buprenorphine at the opioid receptor in vivo is consistent with this conclusion. Hence, buprenorphine can now be classified as a partial agonist at the µ site and as an antagonist at the site against bremazocine induced urine flow, while its action at the site to which it has much lower affinity in vivo remains unknown. 相似文献
995.
996.
Primary sphincter repair in anorectal trauma 总被引:2,自引:1,他引:1
Dr. Jonathan F. Critchlow M.D. Mary Jane Houlihan M.D. Cleland C. Landolt M.D. Mark E. Weinstein M.D. 《Diseases of the colon and rectum》1985,28(12):945-947
Two patients who sustained severe anorectal trauma from "fist fornication" were treated by irrigation, colostomy, drainage, antibiotics, and primary repair of the rectum and anal sphincters without complications. Both had complete return of continence. Primary sphincter repair is advocated for these and similar anorectal injuries. 相似文献
997.
Mark A. Rabinovitch Victor Kalff Richard Allen Amnon Rosenthal James Albers Sunil K. Das Bertram Pitt Dennis P. Swanson Thomas Mangner W. Leslie Rogers James H. Thral William H. Beierwaltes 《European journal of nuclear medicine and molecular imaging》1985,10(5-6):222-227
The utility of -123I-hexadecanoic acid myocardial scintigraphy as a metabolic probe of cardiomyopathies was investigated. Sixteen patients with a variety of cardiomyopathies and myopathies that involve cardiac muscle and ten volunteers were imaged in the postabsorptive state in a 40° LAO projection after a standard dose of -123I-hexadecanoic acid. An elimination T1/2 was calculated from the left ventricular myocardial time-activity curve. An uptake index, corrected for chest wall attenuation, was also computed in 7 of 10 volunteers and 8 of 16 patients.Of the 16 patients, only 2 had distinctly abnormal -123I-hexadecanoic acid myocardial tracer kinetics. The first patient had a metabolic disorder of which cartine deficiency was one component. The second patient had endocardial fibroelastosis, a process which has been linked to disorders which deprive the myocardium of oxygen and energy. Therefore, the cardiomyopathy may have been caused by some abnormality of cardiac metabolism other than carnitine deficiency. Although of limited utility in the overall cardiomyopathic population, -123I-hexadecanoic acid myocardial scintigraphy should be further investigated as a screening test for carnitine deficiency and related metabolic abnormalities in patients at risk.Supported by a Canadian Heart Foundation Research FellowshipSupported by an Australian Heart Foundation Travel Grant 相似文献
998.
In a consecutive series of 117 depressed patients referred for electroconvulsive therapy, the 10 with secondary depression had significantly poorer outcomes according to three independently assessed measures-Hamilton rating scale score at discharge, global rating at discharge, and mean depressive symptom score during a 6-month follow-up. 相似文献
999.
1000.
Kathleen R. Ambrose Dennis E. Rice Mark M. Goodman F. F. Knapp Jr. 《European journal of nuclear medicine and molecular imaging》1987,13(7):374-379
The metabolism of two new 3-methyl-branched iodovinyl fatty acids in rat hearts was evaluated by determining the subcellular and lipid pool distribution of these radiolabeled analogues after intravenous injection. Methyl branching had been introduced into the straight chain analogue, 19-iodo-18-nonadecenoic acid (IVN), to produce the monomethyl analogue, 19-iodo-3-(R,S)-methyl-18-nonadecenoic acid (BMIVN) and the dimethyl derivative, 19-iodo-3,3-dimethyl-18-nonadecenoic acid (DMIVN) in the hope of inhibiting oxidation. Since the presence of 3-methyl branching results in delayed myocardial clearance in rats, differences were sought in the lipid and subcellular distribution of these branched analogues that might correlate with the prolonged retention and reflect differences in metabolism. Hearts of rats injected intravenously with the radiolabeled fatty acids were removed and homogenized and the homogenates partitioned between the chloroform-methanol (organic) fraction and the aqueous fraction. Comparison of the distribution of radioactivity between the organic and aqueous fractions showed that most of the DMIVN and BMIVN activity was in the organic fraction with IVN activity initially divided equally between the two fractions. Identification of the lipid components of these organic fractions showed that there was slow incorporation of DMIVN into the triglyceride and polar lipid fractions with a slow loss from the free fatty acid fraction. With the straight chain IVN analogue which shows rapid washout from rat hearts, there was loss of activity from all 3 lipid components during the 60 min. The monomethyl branched BMIVN analogue demonstrated predominant storage in the polar lipid fraction with some incorporation into triglycerides. Subcellular distribution studies of the three analogues also showed differences that correlated with the observed differences in heart retention properties. With the unbranched IVN analogue, radioactivity was found primarily in the cytoplasmic fraction 30 min after injection, whereas the branched analogues demonstrated a much higher association with the microsomal and mitochondrial fractions of the heart. In rats fed prior to injection, these differences in the subcellular distribution profiles were minimized. The lipid and subcellular distribution patterns reported here for the methyl branched analogues as compared to those of the straight chain iodovinyl fatty acid may provide some understanding as to the mechanisms of retention in rat myocardium.Research supported by the Office of Health and Environmental Research, U.S. Department of Energy, under contract DE-AC0 5-840 R21400 with Martin Marietta Energy Systems, Inc. 相似文献