全文获取类型
收费全文 | 7439篇 |
免费 | 719篇 |
国内免费 | 6篇 |
专业分类
8164篇 |
出版年
2023年 | 51篇 |
2022年 | 117篇 |
2021年 | 236篇 |
2020年 | 154篇 |
2019年 | 184篇 |
2018年 | 181篇 |
2017年 | 158篇 |
2016年 | 210篇 |
2015年 | 357篇 |
2014年 | 384篇 |
2013年 | 466篇 |
2012年 | 555篇 |
2011年 | 547篇 |
2010年 | 321篇 |
2009年 | 294篇 |
2008年 | 385篇 |
2007年 | 398篇 |
2006年 | 331篇 |
2005年 | 339篇 |
2004年 | 318篇 |
2003年 | 279篇 |
2002年 | 275篇 |
2001年 | 68篇 |
2000年 | 44篇 |
1999年 | 67篇 |
1998年 | 84篇 |
1997年 | 43篇 |
1996年 | 35篇 |
1995年 | 39篇 |
1994年 | 33篇 |
1993年 | 47篇 |
1992年 | 46篇 |
1991年 | 31篇 |
1990年 | 34篇 |
1989年 | 40篇 |
1988年 | 31篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 29篇 |
1984年 | 38篇 |
1982年 | 45篇 |
1981年 | 46篇 |
1980年 | 43篇 |
1979年 | 26篇 |
1978年 | 40篇 |
1977年 | 30篇 |
1975年 | 33篇 |
1974年 | 30篇 |
1973年 | 29篇 |
1972年 | 24篇 |
排序方式: 共有8164条查询结果,搜索用时 15 毫秒
41.
42.
43.
This study determined the correlation between the functional capacity of chronic lymphatic leukemia lymphocytes as determined by their response to nonspecific mitogens with their glucose metabolism and surface immunoglobulin characteristics. A majority of patients (12) were found to have lymphocytes with impaired transformation to both PHA and pokeweed mitogens. These cells also had impaired glucose metabolism in unstimulated cultures and failed to have the striking increase in glucose metabolism in response to mitogens which is characteristic of normal lymphocytes. Most of these lymphocytes had IgM surface immunoglobulins. However, we were not able to demonstrate surface immunoglobulins on the lymphocytes of one patient in this group. Two patients were found to have lymphocytes with normal lymphoblastic transformation to PHA and impaired transformation to pokeweed suggesting cells of T origin. The glucose metabolism of these lymphocytes were less impaired in unstimulated cultures than those of the other patients and had a striking increment in glucose metabolism in response to PHA similar to normal lymphocytes. Unexpectedly, these lymphocytes were found to have IgG on their surface suggesting cells of B origin. These results indicate that there may be two groups of CLL patients with clinically similar disease in whom the functional and metabolic characteristics of the lymphocytes are distinct and that the surface immunoglobulin characteristic of lymphocytes may not always predict their functional characteristic. 相似文献
44.
Carol?E?DonaldEmail author Fizza?Qureshi Malcolm?J?Burns Marcia?J?Holden Joseph?R?BlasicJr Alison?J?Woolford 《BMC biotechnology》2005,5(1):15
Background
The wide variety of real-time amplification platforms currently available has determined that standardisation of DNA measurements is a fundamental aspect involved in the comparability of results. 相似文献45.
46.
Clark H Palaniyar N Strong P Edmondson J Hawgood S Reid KB 《Journal of immunology (Baltimore, Md. : 1950)》2002,169(6):2892-2899
Surfactant protein D (SP-D) is a molecule of the innate immune system that recognizes the patterns of surface carbohydrate on pathogens and targets them for phagocytosis and killing. SP-D-deficient mice show an increased number of macrophages in the alveolar space, excess surfactant phospholipid, overproduction of reactive oxygen species, and the development of emphysema. We report here that SP-D-deficient mice have a 5- to 10-fold increase in the number of apoptotic and necrotic alveolar macrophages, as defined by annexin V and propidium iodine staining, respectively. Intrapulmonary administration of a truncated 60-kDa fragment of human recombinant SP-D reduces the number of apoptotic and necrotic alveolar macrophages and partially corrects the lipid accumulation in SP-D-deficient mice. The same SP-D fragment binds preferentially to apoptotic and necrotic alveolar macrophages in vitro, suggesting that SP-D contributes to immune homeostasis in the lung by recognizing and promoting removal of necrotic and apoptotic cells. 相似文献
47.
Chavda S Liu Y Babu B Davis R Sielaff A Ruprich J Westrate L Tronrud C Ferguson A Franks A Tzou S Adkins C Rice T Mackay H Kluza J Tahir SA Lin S Kiakos K Bruce CD Wilson WD Hartley JA Lee M 《Biochemistry》2011,50(15):3127-3136
With the aim of incorporating a recognition element that acts as a fluorescent probe upon binding to DNA, three novel pyrrole (P) and imidazole (I)-containing polyamides were synthesized. The compounds contain a p-anisylbenzimidazolecarboxamido (Hx) moiety attached to a PP, IP, or PI unit, giving compounds HxPP (2), HxIP (3), and HxPI (4), respectively. These fluorescent hybrids were tested against their complementary nonfluorescent, non-formamido tetraamide counterparts, namely, PPPP (5), PPIP (6), and PPPI (7) (cognate sequences 5'-AAATTT-3', 5'-ATCGAT-3', and 5'-ACATGT-3', respectively). The binding affinities for both series of polyamides for their cognate and noncognate sequences were ascertained by surface plasmon resonance (SPR) studies, which revealed that the Hx-containing polyamides gave binding constants in the 10(6) M(-1) range while little binding was observed for the noncognates. The binding data were further compared to the corresponding and previously reported formamido-triamides f-PPP (8), f-PIP (9), and f-PPI (10). DNase I footprinting studies provided additional evidence that the Hx moiety behaved similarly to two consecutive pyrroles (PP found in 5-7), which also behaved like a formamido-pyrrole (f-P) unit found in distamycin and many formamido-triamides, including 8-10. The biophysical characterization of polyamides 2-7 on their binding to the abovementioned DNA sequences was determined using thermal melts (ΔT(M)), circular dichroism (CD), and isothermal titration calorimetry (ITC) studies. Density functional calculations (B3LYP) provided a theoretical framework that explains the similarity between PP and Hx on the basis of molecular electrostatic surfaces and dipole moments. Furthermore, emission studies on polyamides 2 and 3 showed that upon excitation at 322 nm binding to their respective cognate sequences resulted in an increase in fluorescence at 370 nm. These low molecular weight polyamides show promise for use as probes for monitoring DNA recognition processes in cells. 相似文献
48.
Hao YH Yong HY Murphy CN Wax D Samuel M Rieke A Lai L Liu Z Durtschi DC Welbern VR Price EM McAllister RM Turk JR Laughlin MH Prather RS Rucker EB 《Transgenic research》2006,15(6):739-750
Vascular function, vascular structure, and homeostasis are thought to be regulated in part by nitric oxide (NO) released by endothelial cell nitric oxide synthase (eNOS), and NO released by eNOS plays an important role in modulating metabolism of skeletal and cardiac muscle in health and disease. The pig is an optimal model for human diseases because of the large number of important similarities between the genomic, metabolic and cardiovascular systems of pigs and humans. To gain a better understanding of cardiovascular regulation by eNOS we produced pigs carrying an endogenous eNOS gene driven by a Tie-2 promoter and tagged with a V5 His tag. Nuclear transfer was conducted to create these animals and the effects of two different oocyte activation treatments and two different culture systems were examined. Donor cells were electrically fused to the recipient oocytes. Electrical fusion/activation (1 mM calcium in mannitol: Treatment 1) and electrical fusion (0.1 mM calcium in mannitol)/chemical activation (200 μM Thimerosal for 10 min followed by 8 mM DTT for 30 min: Treatment 2) were used. Embryos were surgically transferred to the oviducts of gilts that exhibited estrus on the day of fusion or the day of transfer. Two cloned transgenic piglets were born from Treatment 1 and low oxygen, and another two from Treatment 2 and normal oxygen. PCR, RT-PCR, Western blotting and immunohistochemistry confirmed that the pigs were transgenic, made message, made the fusion protein and that the fusion protein localized to the endothelial cells of placental vasculature from the conceptuses as did the endogenous eNOS. Thus both activation conditions and culture systems are compatible with development to term. These pigs will serve as the founders for a colony of miniature pigs that will help to elucidate the function of eNOS in regulating muscle metabolism and the cardiorespiratory system. 相似文献
49.
50.