全文获取类型
收费全文 | 8190篇 |
免费 | 533篇 |
国内免费 | 90篇 |
专业分类
耳鼻咽喉 | 50篇 |
儿科学 | 388篇 |
妇产科学 | 116篇 |
基础医学 | 1349篇 |
口腔科学 | 256篇 |
临床医学 | 773篇 |
内科学 | 1480篇 |
皮肤病学 | 447篇 |
神经病学 | 801篇 |
特种医学 | 735篇 |
外科学 | 810篇 |
综合类 | 93篇 |
预防医学 | 346篇 |
眼科学 | 79篇 |
药学 | 521篇 |
2篇 | |
中国医学 | 1篇 |
肿瘤学 | 566篇 |
出版年
2022年 | 46篇 |
2021年 | 112篇 |
2020年 | 78篇 |
2019年 | 74篇 |
2018年 | 153篇 |
2017年 | 123篇 |
2016年 | 171篇 |
2015年 | 173篇 |
2014年 | 225篇 |
2013年 | 271篇 |
2012年 | 332篇 |
2011年 | 319篇 |
2010年 | 251篇 |
2009年 | 252篇 |
2008年 | 303篇 |
2007年 | 352篇 |
2006年 | 333篇 |
2005年 | 306篇 |
2004年 | 288篇 |
2003年 | 252篇 |
2002年 | 279篇 |
2001年 | 302篇 |
2000年 | 257篇 |
1999年 | 221篇 |
1998年 | 217篇 |
1997年 | 219篇 |
1996年 | 178篇 |
1995年 | 172篇 |
1994年 | 167篇 |
1993年 | 166篇 |
1992年 | 132篇 |
1991年 | 138篇 |
1990年 | 151篇 |
1989年 | 154篇 |
1988年 | 133篇 |
1987年 | 121篇 |
1986年 | 130篇 |
1985年 | 122篇 |
1984年 | 99篇 |
1983年 | 72篇 |
1982年 | 67篇 |
1981年 | 70篇 |
1980年 | 59篇 |
1979年 | 73篇 |
1978年 | 52篇 |
1977年 | 64篇 |
1976年 | 49篇 |
1975年 | 51篇 |
1973年 | 53篇 |
1968年 | 42篇 |
排序方式: 共有8813条查询结果,搜索用时 15 毫秒
101.
Stein TP; Oram-Smith JC; Leskiw MJ; Wallace HW; Long LC; Leonard JM 《The American journal of physiology》1976,230(5):1321-1325
102.
103.
Cell culture-based transdominant genetic techniques provide new methods for discovering peptide/RNA modulators of cellular pathways. We applied this technology to isolate a peptide inhibitor of human rhinovirus. A green fluorescent protein (GFP)-scaffolded library of cDNA fragments was expressed in HeLa cells from a retroviral vector and screened for inhibitors of rhinovirus-mediated cell killing. A DNA clone, I421, increased cell survival in an HRV14 challenge assay from less than 0.5% to greater than 60%. It encodes a 53-amino-acid C-terminal extension of the GFP scaffold. Particular subclones of Hela cells expressing I421 (exemplified by I421dp3) show a delay in virus production and a 50-fold decrease in viral RNA levels at 6-8 h postinfection. HRV2, HRV14, and HRV16 show a dramatic decrease in plaque-forming ability on I421dp3 while Coxsackievirus B3 showed a small reduction. Levels of ICAM-1, the receptor for the main rhinovirus serotype, are not altered in I421dp3. 相似文献
104.
The effects of thermochemotherapy using cyclophosphamide plus hyperthermia on the malignant pleural mesothelioma in vivo 总被引:2,自引:0,他引:2
The human malignant pleural mesothelioma is related to the use of asbestos in the majority of cases. Though the use of asbestos has been prohibited since the 1990s, the incidence of pleural mesothelioma is still increasing because of a latency period of at least 20 years. This study investigated the benefit of single therapy with cyclophosphamide or hyperthermia or the combination of both on cells of a human pleural mesothelioma cell line, xenotransplanted subcutaneously in the paw of mice. A CONTROL group received the same volume of physiological saline. The oxygenation of tumours was measured, tumour growth was followed over 3 weeks, immunohistochemical studies and a light and electron microscopic evaluation were performed. Chemotherapy or hyperthermia alone was only temporarily effective. The greatest benefit was achieved using combined thermochemotherapy consisting of cyclophosphamide plus hyperthermia: 50% of this group had partial remissions, and 67% responded to this therapy. After 3 weeks tumours grew again. Superior effects could be achieved by performing additional cycles of chemotherapy or adding another drug or radiation for instance. This study shows promising results in the treatment of malignant pleural mesothelioma. 相似文献
105.
Apoptotic cell death in mouse models of GM2 gangliosidosis and observations on human Tay-Sachs and Sandhoff diseases 总被引:5,自引:2,他引:5
Huang JQ; Trasler JM; Igdoura S; Michaud J; Hanal N; Gravel RA 《Human molecular genetics》1997,6(11):1879-1885
Tay-Sachs and Sandhoff diseases are autosomal recessive neurodegenerative
diseases resulting from the inability to catabolize GM2 ganglioside by
beta-hexosaminidase A (Hex A) due to mutations of the alpha subunit
(Tay-Sachs disease) or beta subunit (Sandhoff disease) of Hex A. Hex B
(beta beta homodimer) is also defective in Sandhoff disease. We previously
developed mouse models of both diseases and showed that Hexa-/- (Tay-Sachs)
mice remain asymptomatic to at least 1 year of age while Hexb-/- (Sandhoff)
mice succumb to a profound neurodegenerative disease by 4-6 months of age.
Here we find that neuron death in Hexb-/- mice is associated with apoptosis
occurring throughout the CNS, while Hexa-/- mice were minimally involved at
the same age. Studies of autopsy samples of brain and spinal cord from
human Tay-Sachs and Sandhoff diseases revealed apoptosis in both instances,
in keeping with the severe expression of both diseases. We suggest that
neuron death is caused by unscheduled apoptosis, implicating accumulated
GM2 ganglioside or a derivative in triggering of the apoptotic cascade.
相似文献
106.
The bias favoring deletion over inversion in DH-JH rearrangement has been
known for years, but the underlying mechanism has yet to be fully defined.
It has been suggested that the ratio of deletion/inversion is determined by
the combined effect of two factors: (i) the relative strengths of 5' and 3'
recombination signal sequences (RSS) of a DH segment, and (ii) the
efficiency with which the deletional product (one joint) forms relative to
the inversional product (two joints). In this study, we analyzed for the
first time the effect of factor 1 alone on the biased 3' RSS utilization in
DH-JH joining by using deletional plasmids in an extrachromosomal substrate
V(D)J recombination assay. It was found that the 3' RSS and associated
coding end (12 bp) mediate recombination more efficiently than the 5'
RSS/coding end DH-JH plasmids. These results demonstrate that the effect of
the RSS/coding end alone can account, at least partially, for the
predominant deletion in DH-JH recombination. The potential effect of the
relative strength of RSS and associated coding end on the ordered
rearrangement of DH-JH followed by VH to DH-JH was also assessed. When
recombination frequencies of D-->J (3' DH to J3) were compared with
frequencies of V-- >D (VHPJ14 to 3' DH or VHOX2 to 3' DH), it was found
that V-->D joining was, if anything, more efficient than D-->J
joining. Therefore, if all three segments were accessible, RSS/coding end
effects would not contribute to the ordered rearrangement of the IgH locus.
相似文献
107.
JM Hopkin 《Current opinion in immunology》1997,9(6):788-792
Atopy — a T helper 2 cell driven hypersensitivity to innocuous antigens (allergens) which causes most cases of asthma — is of complex genetic and environmental origins. There is compelling epidemiological evidence for a rise in atopic disease in ‘westernised’ communities. The changing pattern of microbial exposure in early childhood is suggested to be the principal candidate mechanism for this rise. 相似文献
108.
Treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or irradiation with ultraviolet light (uv254 nm) induces amplification of integrated as well as episomal sequences of bovine papillomavirus (BPV) type 1 DNA in BPV-1-transformed mouse C127 cells (i.e., ID13 cells). This is shown by filter in situ hybridization and Southern blot analysis of cellular DNA. Similarly, infection of ID13 cells with herpes simplex virus (HSV) type 1 which has been shown to be mutagenic for host cell DNA leads to amplification of BPV DNA sequences. In contrast to this induction of DNA amplification by initiators, treatment of ID13 cells with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) does not result in increased synthesis of BPV DNA nor does TPA treatment modulate the initiator-induced DNA amplification. Similar to other cell systems infection with adeno-associated virus (AAV) type 2 inhibits BPV-1 DNA amplification irrespective of the inducing agent. In contrast to initiator-induced DNA amplification, treatment with carcinogen (MNNG) or tumor promoters or combination of MNNG and promoter of C127 cells prior to transformation by BPV-1 does not lead to an increase in the number of transformed foci. The induction of amplification of papillomavirus DNA by initiating agents possibly represents one of the mechanisms by which the observed synergism between papillomavirus infection and initiators in tumorigenesis might occur. 相似文献
109.
Stretch activation and isoforms of myosin heavy chain and troponin-T of rat skeletal muscle fibres 总被引:5,自引:0,他引:5
Galler S. Schmitt T. L. Hilber K. Pette D. 《Journal of muscle research and cell motility》1997,18(5):555-561
Recent studies on single mammalian skeletal muscle fibres revealed a correlation between the kinetics of stretch-induced delayed
force increase (stretch activation) and the isoforms of the myosin heavy chain. This observation suggests a causal relation
between stretch activation and myosin heavy chain. However, the assumption is weakened by the fact that isoforms of other
myofibrillar proteins tend to be coexpressed with myosin heavy chain isoforms. The relation between the isoforms of the tropomyosin-binding
troponin subunit and myosin heavy chain is unknown. For a variety of reasons, tropomyosin-binding troponin subunit is a possible
candidate for being involved in stretch activation. Therefore, we measured stretch activation of single, maximally Ca2+-activated
skinned rat skeletal muscle fibres and characterized them by their myosin heavy chain composition, as well as by the isoform
species of tropomyosin-binding troponin subunit. Four myosin heavy chain isoforms (I, IIa, IId or IIx and IIb) and six tropomyosin-binding
troponin subunit isoforms (TnT1s, TnT2s, TnT1f, TnT2f, TnT3f, TnT4f) were distinguis hed. The following preferential coexpression
patterns of the myosin heavy chain and tropomyosin-binding troponin subunit isoforms were observed: MHCI-TnT1s, MHCIIa-TnT3f,
MHCIId-TnT1f, and MHCIIb-TnT4f. Stretch activation kinetics was found to be correlated with the myosin heavy chain isoform
complement also in fibres not displaying one of the preferential MHC-TnTf isoform coexpression patterns. This corroborates
the assumption of a causal relation between myosin heavy chain and stretch activation
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
110.
C Maechling-Strasser P Déjardin J C Galin A Schmitt 《Journal of biomedical materials research》1989,23(12):1385-1393
Glass and silica beads were precoated with various polymers to obtain steric exclusion chromatography (SEC) supports which are nonadsorbant for hydrophilic macromolecules. The efficiency of this treatment was estimated by subsequent radiolabeled fibrinogen adsorption. The result obtained with a block copolymer was better than with various hydrophilic homopolymers. This ABA type block copolymer, where A is a poly(N-acetylethyleneimine) (PAEI) sequence and B a polyethylene oxide (PEO) sequence was preadsorbed at pH 4.5 and 25 degrees C; the fibrinogen adsorption was reduced to less than 5% of the value observed on untreated solid surfaces. Thus the hemocompatibility of solid supports should be increased by precoating with this block copolymer. Results for nonporous glass beads and porous silica particles were in good correlation. 相似文献