全文获取类型
收费全文 | 8136篇 |
免费 | 681篇 |
国内免费 | 8篇 |
专业分类
8825篇 |
出版年
2023年 | 30篇 |
2022年 | 84篇 |
2021年 | 130篇 |
2020年 | 69篇 |
2019年 | 113篇 |
2018年 | 158篇 |
2017年 | 119篇 |
2016年 | 239篇 |
2015年 | 380篇 |
2014年 | 435篇 |
2013年 | 458篇 |
2012年 | 577篇 |
2011年 | 580篇 |
2010年 | 368篇 |
2009年 | 343篇 |
2008年 | 461篇 |
2007年 | 443篇 |
2006年 | 406篇 |
2005年 | 405篇 |
2004年 | 408篇 |
2003年 | 361篇 |
2002年 | 325篇 |
2001年 | 308篇 |
2000年 | 245篇 |
1999年 | 223篇 |
1998年 | 79篇 |
1997年 | 81篇 |
1996年 | 60篇 |
1995年 | 59篇 |
1994年 | 39篇 |
1993年 | 31篇 |
1992年 | 80篇 |
1991年 | 84篇 |
1990年 | 54篇 |
1989年 | 57篇 |
1988年 | 49篇 |
1987年 | 45篇 |
1986年 | 32篇 |
1985年 | 35篇 |
1984年 | 34篇 |
1982年 | 24篇 |
1979年 | 20篇 |
1978年 | 25篇 |
1977年 | 23篇 |
1976年 | 25篇 |
1975年 | 19篇 |
1974年 | 25篇 |
1973年 | 20篇 |
1971年 | 20篇 |
1970年 | 19篇 |
排序方式: 共有8825条查询结果,搜索用时 15 毫秒
101.
An attempt has been made to discriminate additional types of synapses than have been previously described in the nucleus accumbens septi of the cat, which can, according to Brockhaus (1942), justifiably be termed the fundus striati due to the fact that it possesses all of the morphological and some of the neurochemical features of the striatum. This was undertaken in order to correlate at least one type of synapse with each different afferent pathway. Nine distinct types of synapses could be differentiated electron microscopically: Type I: axo-spinous synapses with sparse, small, round vesicles which seemed to be the nigro-striatal endings (35%). Type II: axo-somatic or axo-dendritic en passant synapses containing small, round vesicles (3%). Type III: axo-spinous synapses filled with densely-packed, small, round vesicles displaying strong postsynaptic thickenings which seem to be cortico-striatal (17%). Type IV: large axo-spinous synapses with densely-arranged, small, round vesicles contacting larger spines branching off a pedicle (9%). Type V: axo-somatic or axo-dendritic synapses containing large pleomorphic vesicles, probably axon collaterals (1%). Type VI: axo-somatic or axo-dendritic synapses with elongated small vesicles (20 X 45 nm) (3%). Type VII: large axo-somatic or axo-dendritic synapses filled by densely-packed, small, round vesicles (11%). Type VIII: large axo-somatic or axo-dendritic synapses containing loosely-arranged, small, round vesicles (8%). Type IX: axo-somatic or axo-dendritic synapses containing large, round vesicles in a translucent axoplasm (13%). 相似文献
102.
1. Gene ? is a recessive lethal factor found in the white strain of axolotls. Animals heterozygous for the gene are phenotypically normal. When mated with each other they give offspring 25% of which exhibit the lethal effects of the gene. 2. The ?/? homozygotes develop normally to an advanced embryonic stage (Harrison stage 40) before the effects of the gene are first manifested. They then come to display a characteristic combination of abnormalities, including a disproportionately small head, small and poorly developed eyes, abnormal poorly developed gills, undifferentiated limb buds, and reduced overall growth rate. They may feed briefly, but soon stop and invariably die within a few weeks of the time of hatching. 3. The action of gene ? has been analyzed by parabiosing mutant and normal embryos, and by grafting various organ primordia reciprocally between mutant and normal embryos. Parabiosis to normal embryos fails to correct the abnormalities of the mutants, although their survival may be somewhat prolonged. Grafts of mutant organ primordia (eye, limb, gill, pronephros, gonad, head) also invariably fail to show improved development or to survive on normal hosts; normal organ primordia develop normally on mutant hosts so long as the mutant survives. These experiments indicate that gene ? is a recessive autonomous cell lethal affecting all of the organ systems during late embryonic and early larval development. 相似文献
103.
104.
105.
106.
Wei-Kai Hung Meng-Han Shen Kuan-Yu Chen Wen-Hung Chung I-Hsin Shih Chia-Hsieh Chang Chin-Yi Yang 《Journal of musculoskeletal & neuronal interactions》2022,22(2):292
Buschke-Ollendorff syndrome (BOS) is a rare, usually benign, autosomal dominant genetic disease affecting about 0.005% globally. BOS commonly manifests with asymptomatic connective tissue nevi, sometimes with sclerotic bone lesions like osteopoikilosis or melorheostosis. However, BOS may develop severe, symptomatic complications that require surgical intervention. Here we report a 9-year-8-month girl presenting with multiple nonpruritic, nonpainful skin plaques scattered around the trunk, buttocks, and bilateral legs. She had a history of right varus foot with inadequate plantar flexion. Upon visiting, obvious leg length discrepancy (LLD) was noted. Lesional biopsy revealed increased fibroblasts within dermal collagen bundles. Verhoeff-van Gieson stain revealed scattered foci of thickened elastic fibers between collagen fibers, especially in the mid-dermis. Radiographic examination of the lower extremities showed multiple small, round-to-oval shaped, radiopaque spots on the pelvic bones, femurs, tibiae, and both feet. Hyperostosis along the long axis with “dripping candle wax” appearance was characteristic of osteopoikilosis and melorheostosis. Genetic analysis showed heterozygous point mutation in exon 1 of LEMD3 gene (c.1323C>A, p.Y441X), confirming diagnosis of BOS. Sequential and epiphyseodesis were performed to correct LLD with a favorable outcome at 2-year follow-up. BOS associated with severe bone abnormalities is rare, but orthopedic surgical intervention can provide satisfactory outcome. 相似文献
107.
Eliza F. Chakravarty Viktor Martyanov David Fiorentino Tammara A. Wood David James Haddon Justin Ansel Jarrell Paul J. Utz Mark C. Genovese Michael L. Whitfield Lorinda Chung 《Arthritis research & therapy》2015,17(1)
IntroductionSystemic sclerosis is an autoimmune disease characterized by inflammation and fibrosis of the skin and internal organs. We sought to assess the clinical and molecular effects associated with response to intravenous abatacept in patients with diffuse cutaneous systemic.MethodsAdult diffuse cutaneous systemic sclerosis patients were randomized in a 2:1 double-blinded fashion to receive abatacept or placebo over 24 weeks. Primary outcomes were safety and the change in modified Rodnan Skin Score (mRSS) at week 24 compared with baseline. Improvers were defined as patients with a decrease in mRSS of ≥30 % post-treatment compared to baseline. Skin biopsies were obtained for differential gene expression and pathway enrichment analyses and intrinsic gene expression subset assignment.ResultsTen subjects were randomized to abatacept (n = 7) or placebo (n = 3). Disease duration from first non-Raynaud’s symptom was significantly longer (8.8 ± 3.8 years vs. 2.4 ± 1.6 years, p = 0.004) and median mRSS was higher (30 vs. 22, p = 0.05) in the placebo compared to abatacept group. Adverse events were similar in the two groups. Five out of seven patients (71 %) randomized to abatacept and one out of three patients (33 %) randomized to placebo experienced ≥30 % improvement in skin score. Subjects receiving abatacept showed a trend toward improvement in mRSS at week 24 (−8.6 ± 7.5, p = 0.0625) while those in the placebo group did not (−2.3 ± 15, p = 0.75). After adjusting for disease duration, mRSS significantly improved in the abatacept compared with the placebo group (abatacept vs. placebo mRSS decrease estimate −9.8, 95 % confidence interval −16.7 to −3.0, p = 0.0114). In the abatacept group, the patients in the inflammatory intrinsic subset showed a trend toward greater improvement in skin score at 24 weeks compared with the patients in the normal-like intrinsic subset (−13.5 ± 3.1 vs. −4.5 ± 6.4, p = 0.067). Abatacept resulted in decreased CD28 co-stimulatory gene expression in improvers consistent with its mechanism of action. Improvers mapped to the inflammatory intrinsic subset and showed decreased gene expression in inflammatory pathways, while non-improver and placebos showed stable or reverse gene expression over 24 weeks.ConclusionsClinical improvement following abatacept therapy was associated with modulation of inflammatory pathways in skin.
Trial registration
ClinicalTrials.gov . Registered 1 March 2007. NCT00442611Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0669-3) contains supplementary material, which is available to authorized users. 相似文献108.
Involvement of Matrix Metalloproteinases on the Inhibition of Cells Invasion and Migration by Emodin in Human Neuroblastoma SH-SY5Y Cells 总被引:1,自引:0,他引:1
Hsu-Feng Lu Kuang-Chi Lai Shu-Chun Hsu Hui-Ju Lin Chao-Lin Kuo Ching-Lung Liao Jai-Sing Yang Jing-Gung Chung 《Neurochemical research》2009,34(9):1575-1583
Emodin (1,3,8-trihydroxy-6-methylanthaquinone), an active component present in the root and rhizome of Rheum palmatum L. (Polygonaceae) has anti-bacterial, anti-tumor, diuretic and vasorelaxant effects. However, its mechanism of action on
the cell migration and invasion of human neuroblastoma cancer SH-SY5Y cells is not fully understood. In this study, firstly,
the effects of emodin on the percentage of viable cells were examined by using MTT assay and it was found that emodin induced
dose-and time-dependent inhibition in human neuroblastoma SH-SY5Y cells. Second, the effects of emodin on the migration and
invasion of SH-SY5Y cells were examined by using wound assay and matrigel counting and the results showed that emodin suppressed
the migration and invasion of SH-SY5Y cells. Third, we examined the effect of emodin on the levels of associated proteins
by using Western blotting and the results indicated that emodin inhibited the levels of GRB2, RhoA, HIF-1α, VEGF, FAK, iNOS,
COX2, p-p38, p-c-jun, MMP2, MMP9 and MMP7 but promoted the levels of PKC, PI3K, MEKK3 and NF-κB p65 that led to the inhibition
of migration and invasion of SH-SY5Y cells in vitro. 相似文献
109.
Effective immunotherapy of cancer by DNA vaccination. 总被引:11,自引:0,他引:11
Direct injection of naked plasmid DNA either intramuscularly or intradermally induces strong, long-lived cell-mediated and humoral immune responses to the antigen encoded by the gene vaccine. In the present study, we used gene vaccination with naked plasmid DNA to induce prophylactic immune responses to tumor associated antigens. MAGE-1 (melanoma antigen 1) is an ideal candidate for cancer vaccines because it belongs to a family of genes that are expressed in a number of human tumors of various histological types but not in normal adult tissues except for the testis, and because both humoral and cell-mediated immune responses against MAGE-1 antigen were detected in tumor patients. Intradermal administration of plasmid DNA encoding MAGE-1 (pcMAGE1) induced anti-MAGE-1-specific antibody in BALB/c mice. In contrast, no detectable level of anti-MAGE-1 antibody was induced by intramuscular injection of pcMAGE1. Also, intradermal injection of pcMAGE1 was capable of generating CTLs reactive with MAGE-1-transfected murine tumor cells, M-MSV-MAGE1. Most of the mice (8 out of 10) immunized with pcMAGE1 rejected the challenge of M-MSV-MAGE1 tumor cells, compared with control animals most of which developed tumors. This suggests that intradermal DNA vaccination could provide a novel immunotherapy of cancer. 相似文献
110.
X-ray diffraction patterns have been obtained for the lyotropic phases of n-octyl 1-O-beta-D-glucopyranoside and the related n-heptyl, n-nonyl and n-decyl compounds with water. The octyl compound exhibits all three liquid crystal phases and forms a micellar solution with increasing solvation, when the crystal come into contact with water at room temperature. The X-ray diffraction patterns show a one-dimensional lamellar phase with [dx] = 28.4 A, a three-dimensional face-centered cubic phase with [a] = 51.2 A, and a two-dimensional hexagonal phase with [a] = [b] = 36.7 A. The micellar solution has a distribution pattern with a maximum at [dx] = 33.8 A. Crystals of the heptyl, nonyl and decyl derivatives form only the lamellar phases and the micellar solution on contact with water at room temperature. 相似文献