全文获取类型
收费全文 | 2950篇 |
免费 | 156篇 |
专业分类
3106篇 |
出版年
2022年 | 22篇 |
2021年 | 30篇 |
2020年 | 19篇 |
2019年 | 32篇 |
2018年 | 44篇 |
2017年 | 46篇 |
2016年 | 80篇 |
2015年 | 111篇 |
2014年 | 112篇 |
2013年 | 207篇 |
2012年 | 212篇 |
2011年 | 193篇 |
2010年 | 120篇 |
2009年 | 115篇 |
2008年 | 181篇 |
2007年 | 184篇 |
2006年 | 182篇 |
2005年 | 163篇 |
2004年 | 150篇 |
2003年 | 135篇 |
2002年 | 127篇 |
2001年 | 27篇 |
2000年 | 19篇 |
1999年 | 28篇 |
1998年 | 25篇 |
1997年 | 32篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 23篇 |
1993年 | 29篇 |
1992年 | 26篇 |
1991年 | 25篇 |
1990年 | 27篇 |
1989年 | 16篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 19篇 |
1978年 | 21篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1973年 | 12篇 |
排序方式: 共有3106条查询结果,搜索用时 15 毫秒
51.
52.
53.
Davide Perini Marilena Meloni Kirsten Wolff Giorgio Binelli 《Conservation Genetics》2007,8(5):1263-1266
The hexaploid herbaceous species Primula glaucescens Moretti and Primula spectabilis Tratt. (2n = 6x = 66) are two endemics of the Italian Pre-Alps protected by national and international laws. In order to plan conservation
strategies for natural populations and to study the influence of the latest glaciation on them we developed a set of microsatellites
markers for the endangered Primula species: ten primer pairs allowed analysis of polymorphic disomic loci in P. glaucescens samples and seven of them also amplified polymorphic disomic markers in P. spectabilis.
Kirsten Wolff and Giorgio Binelli contributed equally to the paper 相似文献
54.
Castagneri Daniele Vacchiano Giorgio Hacket-Pain Andrew DeRose R. Justin Klein Tamir Bottero Alessandra 《Ecosystems》2022,25(1):30-43
Ecosystems - Drought will increasingly threaten forest ecosystems worldwide. Understanding how competition influences tree growth response to drought is essential for forest management aiming at... 相似文献
55.
Pier Giorgio Petronini Simonetta Urbani Roberta Alfieri Angelo F. Borghetti Guido G. Guidotti 《Journal of cellular physiology》1996,169(1):175-185
Human leukemia/lymphoma cells maintained in culture medium without provision of fresh nutrients lose viability and die by a process resembling apoptosis within a few days. Upon incubation in an FCS-supplemented RPMI 1640 medium containing 2 mM L-glutamine CEM, Namalwa, HL-60 and U937 cells, seeded at initial densities of 0.2 to 1 × 106 cells/ml, ceased growing within 3–5 days and progressively entered an apoptotic pathway, as assessed by nucleosomal DNA fragmentation and morphology. Both the major energy-source nutrients in the medium, glucose and glutamine, became rapidly exhausted during the incubation. Further studies were performed using CEM cells. Incubation in glutamine-free or glucose-free medium renewed every 24 h showed that glutamine deprivation is associated with cell death by apoptosis independent of energetic failure, whereas glucose deprivation is followed by rapid loss of mitochondrial function with sharp drop of intracellular ATP and cell death by necrosis. A 12–24 h incubation in glutamine-depleted medium was required to direct the cells toward the apoptotic pathway. Growth arrest followed by apoptotic death was detected in CEM cells when medium glutamine concentration remained below 0.3–0.4 mM for at least 24 h, but a reinstatement of medium glutamine to 2 mM within this period rescued the cells from growth arrest and death. © 1996 Wiley-Liss, Inc. 相似文献
56.
Gianfranco Biondi Olga Rickards Cristina Martinez-Labarga Tea Taraborelli Bianca Ciminelli Giorgio Gruppioni 《American journal of physical anthropology》1996,99(4):519-535
Genetic structure of the Berba of Benin was studied on the basis of biodemographic data and ABO, RH, MNS, KEL, JK, FY, ACP1, ADA, AK1, CA2, ESD, GLO1, G6PD, PGD, PGM1 (subtypes and thermostability), PGM2, PGP, SODA, HBα, HBβ, HBδ, BF, C3, and Hp gene frequencies. Comparisons were carried out with other populations of Benin and of sub-Sahara Africa. Correspondence analysis revealed genetic differentiation among the three main groups of populations who inhabit sub-Saharan Africa: Bushmen-Hottentots, Pygmies, and Negroes. The genetic differentiation of the Negroes in relation to their linguistic affiliation and geographic localization was evident. The first group included the populations belonging to the Bantoid subfamily of the Nigritic linguistic stock living in southern Africa; in the second subcluster the populations of central-eastern Africa were localized, and the third subcluster included the populations living in the West. © 1996 Wiley-Liss, Inc. 相似文献
57.
Giovanni Mantovani Vittorio Gebbia Mario Airoldi Cesare Bumma Paolo Contu Alessandro Bianchi Massimo Ghiani Daniela Dessì Elena Massa Luigi Curreli Biancarosa Lampis Paola Lai Carlo Mulas Antonio Testa Ernesto Proto Gabrio Cadeddu Giorgio Tore 《Cancer immunology, immunotherapy : CII》1998,47(3):149-156
We carried out an open, randomized, phase III, multicenter clinical trial to compare, in neo-adjuvant setting, the clinical
response and toxicity of the combination chemotherapy cisplatin + 5-FU with the same combination plus s.c. recombinant interleukin-2
(rIL-2) in patients with advanced (stage III–IV) head and neck squamous-cell carcinoma (HNSCC). Regimen A was the classical
Al Sarraf treatment: 100 mg/m2 cisplatin i.v. on day 1 plus 1000 mg m−2 day−1 5-FU on days 1–5 as a continuous infusion. Regimen B was the same as regimen A plus 4.5 MIU/day rIL-2 s.c. on days 8–12 and
15–19. Treatment was repeated every 3 weeks for three cycles. A total of 33 patients were enrolled in the study; 30 were evaluable
for toxicity and 28 for response. Seventeen patients were assigned to group A and 16 were assigned to group B. Three patients
(20%) of group A and 4 (31%) of group B had a complete response, 9 patients (60%) of group A and 6 (46%) of group B had a
partial response, with an overall response rate of 12 patients (80%) for group A and 10 patients (77%) for group B. Two patients
(13%) of group A and 3 patients (23%) group B had stable disease; 1 patient (7%) of group A had progressive disease. Thus,
there was not a statistically significant difference in response rate between the two groups and therefore there was no benefit
from the addition of immunotherapy with rIL-2 to the standard chemotherapy. Both regimens were well tolerated. There were
2 toxic deaths (6.7%), 1 from hematological causes in group A and 1 from cardiac causes in group B. Myelosuppression and gastrointestinal
toxicity, mainly nausea/vomiting and stomatitis, were the most frequent toxicities. The calculated number of patients for
the sample has not yet been reached; however, the projection of our present results suggests that it is highly improbable
that a clinically significant difference between the two treatment groups will be observed even if the calculated patient
sample size is achieved.
Received: 9 April 1998 / Accepted: 30 June 1998 相似文献
58.
Canamasas I Debes A Natali PG Kurzik-Dumke U 《The Journal of biological chemistry》2003,278(33):30952-30960
Recessive mutations of the Drosophila gene lethal(2)-tumorous imaginal discs (l(2)tid) cause neoplastic growth of the anlagen of the adult organs, the imaginal discs. Here we report that the three proteins encoded by this evolutionarily conserved gene, Tid50, Tid47, and Tid40, identified as members of the DnaJ cochaperone family, are destined for different cellular compartments, build complexes with many proteins in a developmental stage-specific manner, and are likely to be involved in different cellular processes. We show that the cytosolic Tid47 molecule is a novel component of the Hedgehog (Hh)-Patched (Ptc) signaling regulating cell/tissue polarity and spatial patterning during development and is associated with human tumors such as basal cell carcinoma (BCC) and medulloblastoma. We provide functional evidence for its direct in vivo interaction with the Hh-bound Ptc receptor during signal transmission. Because loss of l(2)tid causes neoplastic transformation of Hh-responsive cells, we suggest that Tid47 may at least act as a guardian of the Hh signaling gradient by regulating Ptc homeostasis in the tissue. Finally, we show that the expression of htid-1, the human counterpart of l(2)tid, is altered in human BCCs. We demonstrate that in BCCs loss of htid expression correlates with loss of differentiation capacity of the neoplastic cells similar to that found in the Drosophila tumor model. 相似文献
59.
Castelli MP Ferraro L Mocci I Carta F Carai MA Antonelli T Tanganelli S Cignarella G Gessa GL 《Journal of neurochemistry》2003,87(3):722-732
Two gamma-hydroxybutyric acid (GHB) analogues, trans-gamma-hydroxycrotonic acid (t-HCA) and gamma-(p-methoxybenzyl)-gamma-hydroxybutyric acid (NCS-435) displaced [3H]GHB from GHB receptors with the same affinity as GHB but, unlike GHB, failed to displace [3H]baclofen from GABAB receptors. The effect of the GHB analogues, GHB and baclofen, on G protein activity and hippocampal extracellular glutamate levels was compared. While GHB and baclofen stimulated 5'-O-(3-[35S]thiotriphospate) [35S]GTPgammaS binding both in cortex homogenate and cortical slices, t-HCA and NCS-435 were ineffective up to 1 mm concentration. GHB and baclofen effect was suppressed by the GABAB antagonist CGP 35348 but not by the GHB receptor antagonist NCS-382. Perfused into rat hippocampus, 500 nm and 1 mm GHB increased and decreased extracellular glutamate levels, respectively. GHB stimulation was suppressed by NCS-382, while GHB inhibition by CGP 35348. t-HCA and NCS-435 (0.1-1000 microm) locally perfused into hippocampus increased extracellular glutamate; this effect was inhibited by NCS-382 (10 microm) but not by CGP 35348 (500 microm). The results indicate that GHB-induced G protein activation and reduction of glutamate levels are GABAB-mediated effects, while the increase of glutamate levels is a GHB-mediated effect. Neither t-HCA nor NCS-435 reproduced GHB sedative/hypnotic effect in mice, confirming that this effect is GABAB-mediated. The GHB analogues constitute important tools for understanding the physiological role of endogenous GHB and its receptor. 相似文献
60.
Samanta Simioni Myriam Schluep Nadège Bault Giorgio Coricelli Joerg Kleeberg Renaud A. Du Pasquier Markus Gschwind Patrik Vuilleumier Jean-Marie Annoni 《PloS one》2012,7(12)