全文获取类型
收费全文 | 11981篇 |
免费 | 772篇 |
国内免费 | 88篇 |
专业分类
耳鼻咽喉 | 135篇 |
儿科学 | 314篇 |
妇产科学 | 358篇 |
基础医学 | 1414篇 |
口腔科学 | 334篇 |
临床医学 | 960篇 |
内科学 | 2753篇 |
皮肤病学 | 219篇 |
神经病学 | 548篇 |
特种医学 | 359篇 |
外国民族医学 | 2篇 |
外科学 | 1889篇 |
综合类 | 331篇 |
一般理论 | 8篇 |
预防医学 | 782篇 |
眼科学 | 485篇 |
药学 | 1102篇 |
中国医学 | 128篇 |
肿瘤学 | 720篇 |
出版年
2023年 | 137篇 |
2022年 | 213篇 |
2021年 | 573篇 |
2020年 | 362篇 |
2019年 | 492篇 |
2018年 | 515篇 |
2017年 | 374篇 |
2016年 | 356篇 |
2015年 | 331篇 |
2014年 | 530篇 |
2013年 | 622篇 |
2012年 | 918篇 |
2011年 | 919篇 |
2010年 | 530篇 |
2009年 | 417篇 |
2008年 | 668篇 |
2007年 | 701篇 |
2006年 | 569篇 |
2005年 | 535篇 |
2004年 | 514篇 |
2003年 | 423篇 |
2002年 | 375篇 |
2001年 | 164篇 |
2000年 | 165篇 |
1999年 | 156篇 |
1998年 | 74篇 |
1997年 | 43篇 |
1996年 | 52篇 |
1995年 | 53篇 |
1994年 | 56篇 |
1993年 | 36篇 |
1992年 | 73篇 |
1991年 | 73篇 |
1990年 | 89篇 |
1989年 | 71篇 |
1988年 | 69篇 |
1987年 | 71篇 |
1986年 | 76篇 |
1985年 | 50篇 |
1984年 | 43篇 |
1983年 | 28篇 |
1982年 | 26篇 |
1981年 | 17篇 |
1980年 | 24篇 |
1979年 | 31篇 |
1977年 | 28篇 |
1976年 | 23篇 |
1974年 | 16篇 |
1973年 | 17篇 |
1970年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
81.
82.
Tang SN Fakhru'l-Razi A Hassan MA Karim MI 《Artificial cells, blood substitutes, and immobilization biotechnology》1999,27(5-6):411-416
Rubber latex effluent is a polluting source that has a high biochemical oxygen demand (BOD). It is estimated that about 100 million liters of effluent are discharged daily from rubber processing factories. Utilization of this effluent such as the use of a coupled system not only can reduce the cost of treatment but also yield a fermentation feedstock for the production of bioplastic. This study initially was carried out to increase the production of organic acids by anaerobic treatment of rubber latex effluent. It was found that through anaerobic treatment the concentration of organic acids did not increase. Consequently, separation of organic acids from rubber latex effluent by anion exchange resin was examined as a preliminary study of recovering acetic and propionic acids. However, the suspended solids (SS) content in the raw effluent was rather high which partially blocked the ion-exchange columns. Lime was used to remove the SS in the rubber latex effluent. After the lime precipitation process, organic acids were found to adsorb strongly onto the anion exchange resin. Less adsorption of organic acids onto the resin was observed before the lime precipitation. This was probably due to more sites being occupied by colloidal particles on the resin thus inhibiting the adsorption of organic acids. The initial concentration of organic acids in the raw effluent was 3.9 g/L. After ion exchange, the concentration of the organic acids increased to 27 g/L, which could be utilized for production of polyhydroxyalkanoates (PHA). For PHA accumulation stage, concentrated rubber latex effluent obtained from ion exchange resins and synthetic acetic acid were used as the carbon source. Quantitative analyses from fed batch culture via HPLC showed that the accumulation of PHA in Alcaligenes eutrophus was maximum with a concentration of 1.182 g/L when cultivated on synthetic acetic acid, corresponding to a yield of 87% based on its cell dry weight. The dry cell weight increased from 0.71 to 1.67 g/L. On the other hand, using concentrated rubber latex effluent containing acetic and propionic acids resulted in reduced PHA content by dry weight (14%) but the dry cell weight increased from 0.49 to 1.30 g/L. The results clearly indicated that the cells grow well in rubber latex effluent but no PHA was accumulated. This could be due to the high concentration of propionic acid in culture broth or other factors such as heavy metals. Thus further work is required before rubber latex effluent can be utilized as a substrate for PHA production industrially. 相似文献
83.
Claudio Gustavo Stefanoff Rocío Hassan Ana Carolina Gonzalez Luiz Ant?nio B Andrade Daniel G Tabak Sérgio Romano Ilana R Zalcberg 《Diagnostic molecular pathology》2003,12(2):79-87
We herein present a technical strategy to optimize DNA isolation from paraffin-embedded tissue (PET). This includes the choice of adequate buffers for proteinase K digestion and multiplex PCR amplifications for assessing the appropriateness of DNA extracts for subsequent PCR assays for detecting clonality. We found that the association of proteinase K digestion in nonionic buffer and subsequent extract dilutions accounted for 79% of successful amplifications. A final efficiency of 88% was achieved by additional organic extractions and/or re-extractions. Comparisons were carried out with control DNA extracts from fresh samples to assess the efficiency of each clonality assay. Immunoglobulin CDRIII rearranged region amplification was more efficient for pregerminal center B-cell lymphomas in contrast to CDRII rearrangement detection, which was more effective for germinal and postgerminal lymphomas. T-cell clonality detection by TCRgamma PCR was less efficient in PET samples than in fresh tissues showing that DNA integrity is more critical for TCR than for IGH amplification. Two inconclusive cases without phenotypic markers and two other atypical lymphoproliferations masked by reactive T cells were diagnosed as plasmablastic lymphomas and as monoclonal B-proliferations, respectively, due to IGH rearrangements. 相似文献
84.
The dragon lizard <Emphasis Type="Italic">Pogona vitticeps</Emphasis> has ZZ/ZW micro-sex chromosomes 总被引:1,自引:0,他引:1
Tariq?EzazEmail author Alexander?E.?Quinn Ikuo?Miura Stephen?D.?Sarre Arthur?Georges Jennifer?A.?Marshall Graves 《Chromosome research》2005,13(8):763-776
The bearded dragon, Pogona vitticeps (Agamidae: Reptilia) is an agamid lizard endemic to Australia. Like crocodilians and many turtles, temperature-dependent
sex determination (TSD) is common in agamid lizards, although many species have genotypic sex determination (GSD). P. vitticeps is reported to have GSD, but no detectable sex chromosomes. Here we used molecular cytogenetic and differential banding techniques
to reveal sex chromosomes in this species. Comparative genomic hybridization (CGH), GTG- and C-banding identified a highly
heterochromatic microchromosome specific to females, demonstrating female heterogamety (ZZ/ZW) in this species. We isolated
the P. vitticeps W chromosome by microdissection, re-amplified the DNA and used it to paint the W. No unpaired bivalents were detected in
male synaptonemal complexes at meiotic pachytene, confirming male homogamety. We conclude that P. vitticeps has differentiated previously unidentifable W and Z micro-sex chromosomes, the first to be demonstrated in an agamid lizard.
Our finding implies that heterochromatinization of the heterogametic chromosome occurred during sex chromosome differentiation
in this species, as is the case in some lizards and many snakes, as well as in birds and mammals. Many GSD reptiles with cryptic
sex chromosomes may also prove to have micro-sex chromosomes. Reptile microchromosomes, long dismissed as non-functional minutiae
and often omitted from karyotypes, therefore deserve closer scrutiny with new and more sensitive techniques. 相似文献
85.
Models of hypersensitivity pneumonitis (HP) should exhibit progression of pulmonary histological abnormalities during continuing challenges. Strain II guinea-pigs were sensitized with Micropolyspora faeni and received 2, 4, or 8 weekly intratracheal (i.t.) particulate M. faeni challenges. Control animals received normal saline (NS). Four days after the last exposure, randomly selected microscopic fields of lung (200/animal) were judged to be normal or abnormal. If abnormal, the location and nature of the abnormalities were determined. Compared with NS treated guinea-pigs, those exposed to 2, 4 and 8 weekly M. faeni challenges exhibited more extensive (P less than 0.001) pulmonary histological abnormalities which involved both the intraalveolar and interstitial compartments. More extensive abnormalities in the 8 week group compared with the 4 week group were caused by increased extent of interstitial mononuclear cell infiltration. The extent of pulmonary interstitial histological abnormalities transiently (four challenges) decreases, but then increases, so that progressive pulmonary inflammation occurs during continuing challenges. 相似文献
86.
An immunoblotting technique was modified to detect and biochemically characterize HLA-DR antigens expressed on circulating human monocytes. Membrane proteins of peripheral blood monocytes were solubilised using the mildly anionic detergent, sodium deoxycholate. These solubilised proteins were resolved by SDS-PAGE and transferred electrophoretically to nitrocellulose. The HLA-DR antigen was detected using a polyclonal antiserum and two monoclonal anti-HLA-DR antibodies. Both immunoperoxidase and 125 I autoradiography techniques were used for visualisation of the antigen. The resolution of HLA-DR reactive material was increased when proteins were renatured with 4M urea after blotting. Immunoprobing of a sample of solubilized membrane proteins showed three bands of HLA-DR antigenic reactivity at molecular weights 65kDa, 55kDa and 46kDa. After storage at –70°C for 2 months, only the 46kDa HLA-DR antigen band was detectable. Nonetheless, the 2-chain HLA-DR molecule was found to be an extremely stable complex which could not be dissociated by boiling in sample buffer containing 5% 2-mercaptoethanol and 2% SDS. A stronger reducing agent, 25 mM dithiotreitol, was required to split the HLA-DR molecule into its alpha and beta subunit chains. Finally, in a study of circulating monocytes from normal subjects, the immunoblotting technique was shown to quantitate solubilised HLA-DR antigen in a reproducible manner. 相似文献
87.
Immunomodulation of autoimmune and inflammatory diseases with intravenous immunoglobulin 总被引:2,自引:0,他引:2
Ephrem A Misra N Hassan G Dasgupta S Delignat S Duong Van Huyen JP Chamat S Prost F Lacroix-Desmazes S Kavery SV Kazatchkine MD 《Clinical and experimental medicine》2005,5(4):135-140
Abstract Intravenous immunoglobulin (IVIg) has been used in the treatment of primary and secondary antibody deficiencies for over two
decades. Since the early 1980s, the therapeutic efficacy of IVIg has been established in idiopathic thrombocytopenic purpura,
Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, myasthenia gravis, dermatomyositis and Kawasaki
syndrome, and the prevention of graft versus host disease in recipients of allogeneic bone marrow transplants. Its use has
also been reported in a large number of other autoimmune and systemic inflammatory conditions. In this review, we discuss
the mechanisms by which IVIg exerts immunomodulatory effects in immune pathologies. 相似文献
88.
Mohamed HS Ibrahim ME Miller EN Peacock CS Khalil EA Cordell HJ Howson JM El Hassan AM Bereir RE Blackwell JM 《Genes and immunity》2003,4(5):351-355
Longitudinal studies in Sudan show ethnic differences in incidence and clinical phenotypes associated with Leishmania donovani. Immunologically, bias in type 1 vs type 2 cytokine responses is important. To determine whether polymorphisms at IL4/IL9 or IFNGR1 contribute to susceptibility, we examined 59 multicase families of visceral leishmaniasis (VL) with/without post Kala-azar dermal leishmaniasis (PKDL). Multipoint nonparametric analysis (Allegro) linked IL4/IL9 to VL per se (P=0.002). Transmission disequilibrium testing with robust variance estimates confirmed association in the presence of linkage between VL per se and IL4 (P=0.008) but not IL9. Stepwise logistic regression analysis showed both IL4RP2 and IL4RP1 markers contributed significantly to the association, suggesting a common disease-associated haplotype. In contrast, IFNGR1 was linked (P=0.031) and associated (P=0.007) to PKDL but not VL or VL per se. Hence, polymorphism in a type 2 cytokine gene influences underlying susceptibility to VL, whereas IFNGR1 is specifically related to susceptibility to PKDL. 相似文献
89.
Tan JA George E Tan KL Chow T Tan PC Hassan J Chia P Subramanium R Chandran R Yap SF 《Clinical and experimental medicine》2004,4(3):142-147
Abstract
β-thalassemia is the most-common genetic disorder of hemoglobin synthesis in Malaysia, and about 4.5% of the population are
heterozygous carriers of the disorder. Prenatal diagnosis was performed for 96 couples using the Amplification Refractory
Mutation System and Gap-Polymerase Chain Reaction. We identified 17 β-globin defects-initiation codon for translation (T-G),
-29 (A-G), -28 (A-G), CAP +1 (A-C), CD 8/9 (+G), CD 15 (G-A), CD 17 (A-T), CD 19 (A-G), Hb E (G-A), IVS1-1 (G-T), IVS1-5 (G-C),
CD 41/42 (-CTTT), CD 71–72 (+A), IVS2-654 (CT), poly A(A-G), 100-kb Gγ(Aγδβ)° and 45-kb Filipino deletions. The 192 β-alleles studied comprised Chinese (151 patients), Malay (21), Orang Asli from
East Malaysia (15), Filipino (1), Indian (1), Indonesian Chinese (2), and Thai (1). In the Chinese, 2 β-globin defects at
CD 41/42 and IVS2-654 were responsible for 74% of β-thalassemia. β-mutations at CD 19, IVS1-1 (G-T), IVS1-5, poly A, and hemoglobin
E caused 76% of the hemoglobin disorders in the Malays. The Filipino 45-kb deletion caused 73.3% of bthalassemia in the Orang
Asli. Using genomic sequencing, the rare Chinese β-mutation at CD 43 (G-T) was confirmed in 2 Chinese, and the Mediterranean
mutation IVS1-1 (G-A) was observed in a Malay β-thalassemia carrier. The β-globin mutations confirmed in this prenatal diagnosis
study were heterogenous and 65 (68%) couples showed a different globin defect from each other. The use of specific molecular
protocols has allowed rapid and successful prenatal diagnosis of β-thalassemia in Malaysia. 相似文献
90.
Defining epithelial cell progenitors in the human oxyntic mucosa 总被引:7,自引:0,他引:7
In the human stomach, the oxyntic epithelium includes numerous tubular invaginations consisting of short pits opening into long glands. The pit is lined by pit cells, whereas the gland is composed of three regions: the base, containing zymogenic cells; the neck, containing neck cells; and the isthmus, composed of little known immature cells and of parietal cells, which are also scattered through the neck and base. The aim of this study was to examine the ultrastructure of the immature cells and to determine their relation to mature cells. To do so, normal oxyntic mucosal biopsies from subjects ranging from 20-43 years old were fixed in aldehydes and postfixed in reduced osmium for electron microscopy and morphometric analysis. The immature cells were sorted out into four classes, whose roles were clarified by comparison with the thoroughly investigated mouse oxyntic epithelium. The first class was composed of the least differentiated immature cells, which were rare and characterized by minute, dense, or cored secretory granules and were accordingly named mini-granule cells. Their function was not clarified. The second class consisted of pre-pit cells, which were characterized by few dense mucous granules and give rise to pit cells that ascend the pit wall and, after reaching the luminal surface, die or are extruded. Both pre-pit and pit cells underwent continuous renewal and, therefore, together constituted a renewal system referred to as pit cell lineage. The third class, or pre-neck cells, characterized by cored secretory granules, give rise to neck cells that descend toward the base region and differentiate further into pre-zymogenic cells, which finally become zymogenic cells. The latter eventually degenerate and die. Thus pre-neck cells and their progeny constitute a renewing system, designated zymogenic cell lineage. The fourth class, or pre-parietal cells, characterized by long microvilli and few tubulovesicles, differentiate into parietal cells that descend along the neck and base regions and eventually degenerate and die. Pre-parietal and parietal cells represent a renewing system referred to as parietal cell lineage. While the origin of the last three classes of progenitor cells has not been elucidated, it is likely that they arise either from an unidentified multipotential stem cell, possibly the mini-granule cell itself, or from the mitotic activity of pre-pit and pre-neck cells. In conclusion, the human oxyntic epithelium is composed of continually renewing cells organized in distinct cell lineages. 相似文献