全文获取类型
收费全文 | 14595篇 |
免费 | 1416篇 |
国内免费 | 5篇 |
专业分类
16016篇 |
出版年
2023年 | 53篇 |
2022年 | 194篇 |
2021年 | 350篇 |
2020年 | 192篇 |
2019年 | 243篇 |
2018年 | 306篇 |
2017年 | 252篇 |
2016年 | 437篇 |
2015年 | 768篇 |
2014年 | 783篇 |
2013年 | 888篇 |
2012年 | 1187篇 |
2011年 | 1146篇 |
2010年 | 705篇 |
2009年 | 613篇 |
2008年 | 866篇 |
2007年 | 848篇 |
2006年 | 827篇 |
2005年 | 741篇 |
2004年 | 698篇 |
2003年 | 682篇 |
2002年 | 592篇 |
2001年 | 114篇 |
2000年 | 69篇 |
1999年 | 134篇 |
1998年 | 201篇 |
1997年 | 114篇 |
1996年 | 117篇 |
1995年 | 108篇 |
1994年 | 96篇 |
1993年 | 113篇 |
1992年 | 94篇 |
1991年 | 71篇 |
1990年 | 77篇 |
1989年 | 62篇 |
1988年 | 74篇 |
1987年 | 53篇 |
1986年 | 50篇 |
1985年 | 54篇 |
1984年 | 64篇 |
1983年 | 74篇 |
1982年 | 66篇 |
1981年 | 61篇 |
1980年 | 64篇 |
1979年 | 42篇 |
1978年 | 43篇 |
1977年 | 41篇 |
1976年 | 43篇 |
1975年 | 40篇 |
1974年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
151.
Yuan-Pu Di Elizabeth Repasky Andrei Laszlo Stuart Calderwood John Subjeck 《Journal of cellular physiology》1995,165(2):228-238
The percentage of T and B lymphocytes expressing a distinct cytoplasmic aggregate enriched in spectrin, ankyrin, and in several other proteins including protein kinase C greatly increases following various activation protocols. Members of the 70 kDa family of heat shock proteins (hsp70) temporarily bind to and stabilize unfolded segments of other proteins, a function apparently required for proper protein folding and assembly. Considering the multiprotein and dynamic nature of the lymphocyte aggregate, the possibility that hsp70 also might be associated with componets of this structure is considered here. Double immunofluorescence analysis indicates that hsp70 is a component of the lymphocyte aggregate and is coincident with spectrin in a subpopulation of freshly isolated, untreated lymphocytes from various murine tissues and in a T-lymphocyte hybridoma. When cell lysates of lymph node T cells are immunoprecipitated using an antibody against hsp70 or spectrin and then analyzed by Western blot utilizing the alternate antibody, it was found that hsp70 and spectrin coprecipitated with one another. Moreover, this coprecipitation could be abolished by addition of ATP. This latter observation was extended to lymphoid cells using a transient permeabilization procedure, and it was shown that addition of exogenous ATP results in the dissipation of the aggregate structure itself. Finally, conditions that result in T-cell activation and aggregate formation, i.e., treatment with the phorbol ester PMA or T-cell receptor cross-linking, also lead to the repositioning of hsp70 into the aggregate from a membrane/cytosolic locale in congruence with spectrin. These data suggest that hsp70 is an active component of the aggregate and that it may function in the interactions believed to occur in this unique activation-associated organelle. © 1995 Wiley-Liss, Inc. 相似文献
152.
Superoxide dismutase activity of the captopril-iron complex 总被引:2,自引:0,他引:2
With an assay that generates superoxide anion radicals without the intervention of metal ions we investigated the antioxidant properties of captopril, an angiotensin-converting enzyme inhibitor with a sulfhydryl group. Under these conditions, increasing concentrations of the drug were seen not to scavenge O·
2
–
directly. However, a combination of captopril and iron could bring about the breakdown of the superoxide anion; a result that may help to understand the free radical-scavenging properties of captopril. 相似文献
153.
154.
Annalisa Botta Elizabeth A. Lindsay Vesna Jurecic Antonio Baldini 《Mammalian genome》1997,8(12):890-895
We have constructed a comparative map in mouse of the critical region of human 22q11 deleted in DiGeorge (DGS) and Velocardiofacial
(VCFS) syndromes. The map includes 11 genes potentially haploinsufficient in these deletion syndromes. We have localized all
the conserved genes to mouse Chromosome (Chr) 16, bands B1-B3. The determination of gene order shows the presence of two regions
(distal and proximal), containing two groups of conserved genes. The gene order in the two regions is not completely conserved;
only in the proximal group is the gene order identical to human. In the distal group the gene order is inverted. These two
regions are separated by a DNA segment containing at least one gene which, in the human DGS region, is the most proximal of
the known deleted genes. In addition, the gene order within the distal group of genes is inverted relative to the human gene
order. Furthermore, a clathrin heavy chain-like gene was not found in the mouse genome by DNA hybridization, indicating that
there is an inconsistent level of gene conservation in the region. These and other independent data obtained in our laboratory
clearly show a complex evolutionary history of the DGS-VCFS region. Our data provide a framework for the development of a
mouse model for the 22q11 deletion with chromosome engineering technologies.
Received: 8 July 1997 / Accepted 11 August 1997 相似文献
155.
156.
Metastasis formation is a major clinical problem in cancer treatment, and no significant progress in the treatment of metastatic
spread has been made. This apparent lack of progress is partly caused by the absence of clinically relevant animal models
of meta stases. The binding of the lectin Helix pomatia agglutinin (HPA) has been associated with a poor prognosis in breast
and colon cancer patients. HPA-positive and -negative human breast and colon cancer cell lines were transplanted into severe
combined immunodeficient (SCID) mice. HPA-positive breast cancer cell lines (MCF-7 and T47D) metastasized in SCID mice, whereas
the HPA-negative ones (BT20, HS578T and HBL100) did not. The HPA-positive colon cancer cell line HT29 metastasized, while
the HPA-negative ones (COLO320DM, SW480 and SW620) did not. However, in two of eight SCID mice inoculated with the HPA-negative
colon cancer cell line, CACO2 metastatic deposits were found. Despite this exception, HPA binding is a good indicator of the
metastasis of human breast and colon cancer cells in SCID mice: 23 out of 26 HPA-positive cancers metastasized, as opposed
to only two out of 38 HPA-negative cancers. This experimental model is well suited for investigating the functional role of
carbohydrate residues recognized by HPA in breast and colon cancer metastasis.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
157.
158.
Role of inhibition of nitric oxide production in monocrotaline-induced pulmonary hypertension 总被引:1,自引:0,他引:1
Mathew Rajamma; Gloster Elizabeth S.; Sundararajan T.; Thompson Carl I.; Zeballos Guillermo A.; Gewitz Michael H. 《Journal of applied physiology》1997,82(5):1493-1498
Mathew, Rajamma, Elizabeth S. Gloster, T. Sundararajan, Carl I. Thompson, Guillermo A. Zeballos, andMichael H. Gewitz. Role of inhibition of nitric oxide productionin monocrotaline-induced pulmonary hypertension. J. Appl. Physiol. 82(5): 1493-1498, 1997.Monocrotaline (MCT)-induced pulmonary hypertension (PH) isassociated with impaired endothelium-dependent nitric oxide(NO)-mediated relaxation. To examine the role of NO in PH,Sprague-Dawley rats were given a single subcutaneous injection ofnormal saline [control (C)], 80 mg/kg MCT, or the same doseof MCT and a continuous subcutaneous infusion of 2 mg · kg1 · day1of molsidomine, a NO prodrug (MCT+MD). Two weeks later, plasma NO3 levels, pulmonary arterialpressure (Ppa), ratio of right-to-left ventricular weights (RV/LV) toassess right ventricular hypertrophy, and pulmonary histology wereevaluated. The plasma NO3 level inthe MCT group was reduced to 9.2 ± 1.5 µM(n = 12) vs. C level of 17.7 ± 1.8 µM (n = 8; P < 0.02). In the MCT+MD group,plasma NO3 level was 12.3 ± 2.0 µM (n = 8). Ppa and RV/LV in theMCT group were increased compared with C [Ppa, 34 ± 3.4 mmHg(n = 6) vs. 19 ± 0.8 mmHg(n = 8) and 0.41 ± 0.01 (n = 9) vs. 0.25 ± 0.008 (n = 8), respectively;P < 0.001]. In the MCT+MDgroup, Ppa and RV/LV were not different when compared with C [19 ± 0.5 mmHg (n = 5) and 0.27 ± 0.01 (n = 9), respectively;P < 0.001 vs. MCT]. Medial wall thickness of lung vessels in the MCT group was increased comparedwith C [31 ± 1.5% (n = 9)vs. 13 ± 0.66% (n = 9);P < 0.001], and MDpartially prevented MCT-induced pulmonary vascular remodeling [22 ± 1.2% (n = 11);P < 0.001 vs. MCT and C].These results indicate that a defect in the availability of bioactive NO may play an important role in the pathogenesis of MCT-induced PH. 相似文献
159.
Clinical and Molecular Characterization of Patients with Distal 11q Deletions 总被引:10,自引:0,他引:10 下载免费PDF全文
Laura A. Penny Marie Dell'Aquila Marilyn C. Jones JoAnn Bergoffen Christopher Cunniff Jean-Pierre Fryns Elizabeth Grace John M. Graham Boris Kousseff Teresa Mattina James Syme Lucille Voullaire Leopoldo Zelante Julie Zenger-Hain Oliver W. Jones Glen A. Evans 《American journal of human genetics》1995,56(3):676-683
Jacobsen syndrome is caused by segmental aneusomy for the distal end of the long arm of chromosome 11. Typical features include mild to moderate psychomotor retardation, trigonocephaly, facial dysmorphism, cardiac defects, and thrombocytopenia, though none of these features are invariably present. To define the critical regions responsible for these abnormalities, we studied 17 individuals with de novo terminal deletions of 11q. The patients were characterized in a loss-of-heterozygosity analysis using polymorphic dinucleotide repeats. The breakpoints in the complete two-generation families were localized with an average resolution of 3.9 cM. Eight patients with the largest deletions extending from 11q23.3 to 11qter have breakpoints, between D11S924 and D11S1341. This cytogenetic region accounts for the majority of 11q− patients and may be related to the FRA11B fragile site in 11q23.3. One patient with a small terminal deletion distal to D11S1351 had facial dysmorphism, cardiac defects, and thrombocytopenia, suggesting that the genes responsible for these features may lie distal to D11S1351. Twelve of 15 patients with deletion breakpoints as far distal as D11S1345 had trigonocephaly, while patients with deletions distal to D11S912 did not, suggesting that, if hemizygosity for a single gene is responsible for this dysmorphic feature, the gene may lie distal to D11S1345 and proximal to D11S912. 相似文献
160.